Signs of Winter 2: Algae, Algae Everywhere

Algae. Photo by Pixabay

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“Algae” is a term of very imprecise meaning. It is used to refer to the microscopic, unicellular protists like the many species of diatoms and  dinoflagellates that make up the producing trophic foundation of most aquatic (especially marine) ecosystems. It is also the term, though, applied to the large, multicellular, plant-like, seaweeds like kelp (which can grow over 50 m long!) or nori which is used to wrap types of sushi. “Algae” has also been used a bit inappropriately but very regularly to describe some bacterial cells like the cyanobacteria (“the blue-green algae”). The one thing that all of these very different “algae” organisms can do, though, is carry out green plant photosynthesis. They utilize a wide array of complex pigments to capture energy from sunlight and then use that energy to make sugars out of carbon dioxide and water. And, as a consequence of this energy capture and transfer, all of these “algae” generate oxygen as a waste product, a fact that is much appreciated by all of us who carry out respiration!

Bluegreen algae (photo micrograph). Photo by J. Golden, Flickr

The blue-green algae are the most ancient of these “algal” organisms. Some 2.5 billion years ago blue-green algae formed thick, floating mats on the surface of the Earth’s primordial oceans. They photosynthesized furiously and produced so much oxygen that they transformed the Earth’s atmosphere from a poisonous, reducing cloud of volcanic gases into the present day’s sustaining, oxygenated system. All of this added oxygen then selected for certain types of energy metabolisms and changed the course of biotic evolution.

Blue-green algae are nowhere as abundant today as they were 2.5 billion years ago, but they still show up in a variety of mostly freshwater ecosystems. I have written about some of these modern day blue-green algae before (see Signs of Summer 1 (June 12, 2014), and Signs of Fall 13 (November 30, 2017)). They are also abundantly represented in the news today from southern Florida where they are clogging up the warm, phosphate and nitrogen rich waters of  Lake Okeechobee doing great damage to the fish population of the lake and the human population surrounding it.

When an algae population of any type grows out of control  it is referred to as a Harmful Algae Bloom (“HAB”). HAB’s frequently involve blue-green algae or the unicellular protist algae but not, as far as I know, the edible sushi seaweeds or kelp (although I do have something to say about a large, macro-seaweed algae HAB later on!). HABs are caused by a complex interplay of environmental factors. Excessive levels of nutrients (especially phosphorus and nitrogen), warm temperatures, changes in salinity, changes in wind or current direction, and alterations in deep ocean upwellings may all contribute to a HAB event. There is also evidence that iron rich dust blown across the Atlantic Ocean all the way from the Sahara Desert may be a factor in stimulating dinoflagellate populations on both the east and west coasts of the United States! Some of these factors are natural and have been causing HABs throughout recorded history. Other of these factors are human generated and may be the reason that the frequency and duration of HABs have been greatly increasing in recent decades.

Red tide. Photo by NOAA, Public Domain

“Red tide” is a term that is frequently applied to a HAB that occurs along an ocean shoreline or in an estuarine ecosystem. Red tides are caused by the out of control boom and bust of some of the species of dinoflagellate protists. When these dinoflagellate populations race out of equilibrium they make the waters in which they live cloudy with their massive numbers. Most species of dinoflagellates contain in their intracellular plastids large concentrations of carotinoid pigments which they use as secondary light capturing and transferring pigments in photosynthesis. Carotinoids are the same secondary pigments found in many green plant leaves. They are the pigments that are “revealed” (and, possibly, preferentially synthesized), for example, when a maple tree stops making chlorophyll in the fall and its leaves turn a brilliant red. Shoreline waters with abundant dinoflagellates, then, often turn red  with the abundant intra- and extracellular concentrations of carotinoids (hence the term “red tide”). The big problem in a red tide, though, are all of the other chemicals that are concentrated in and released from the dinoflagellate cells. Many of these chemicals are directly toxic to fish, sea mammals, birds and humans and embody the devastating biological threat of the red tide.

Karina brevis photo micrograph. Florida Fish and Wildlife C. , Flickr

On the Atlantic and Gulf Coasts of the United States that most common dinoflagellate that generates red tide events is Karenia brevis. Around the world, though, many other dinoflagellate species and even species from other protist groups can become over-stimulated and generate HABS (which may or not be red, and which may or may not generate significant levels of biological toxins).

Florida is currently experiencing a severe and very prolonged red tide that was possibly triggered by the release of a large amount of fertilizer and septic system enriched water from Lake Okeechobee in November 2017.  This was two months after Hurricane Irma pounded the Florida peninsula with rain, and the lake water was released to prevent more flooding across the southern part of the state. The high levels of nitrogen and phosphates in the released lake water when combined with the very warm waters of the Gulf triggered a HAB and a red tide that spread up the Gulf Coast and even spilled out to the Atlantic Coast. Most red tides are self-limiting and fade out as cooler weather and seasonal ocean currents and winds disperse the algal masses. This red tide, though, persisted through the year and is intensifying as the normal, red tide season begins again. Back in 1990’s a red tide in Florida lasted for a record two and half years! Experts say that this current red tide may exceed this thirty month time interval.

Karina brevis bloom off of Flordia (NOTE: a red tide does not have to be red!), Florida Fish and Wildlife C., Flickr

As of early October the Florida red tide has killed over one hundred manatees, dozens of dolphins, three hundred seas turtles and thousands of fish (including a twenty-six foot whale shark (the world’s largest fish)). The Florida Fish and Wildlife Conservation Commission  estimates that 145 miles of the Florida coast are affected by the red tide. Shellfish harvesting and fishing have been severely curtailed. Some people are not even able to go near the seashore during a red tide outbreak because air and sea spray-borne transport of algal generated toxins. One beach visitor reported that the experience of breathing in these toxins was like being sprayed with tear gas! Allergic  and asthmatic reactions to these toxins are also being reported.

So Florida is experiencing two types of HAB’s all at once! The blue green algae explosion in Lake Okeechobee and the Karina brevis explosion on their ocean coastlines. The consensus from the experts is we can only sit and wait for the populations of each of these types of algae to return to some degree of normal equilibrium. We may be waiting for many months or years for that to happen!

There is another type of algae exploding in abundance, too. This is a large, macro-algae that floats on the ocean surface and accumulates on unfortunately located beaches throughout the Gulf of Mexico and Caribbean. Next week we’ll talk about sargassum!





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Signs of Winter 1: Some Observations and Some Rules

Photo by D. Sillman

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December and January are months of wild weather swings. We have a family video of a December 30  from many years ago in which Deborah and I were out playing with in the yard with our children. We are all wearing light shirts, and it was sixty degrees and sunny. We may even have had lunch out on the picnic table that afternoon! I also have clear memories (no home movies, though) of sitting at my writing desk on a December 30 of another year looking out on a frozen, windblown snowscape. The air temperature had plunged to nine degrees (Fahrenheit) below zero and there was a steady, swirling wind of 23 mph.  The wind chills were in the -35 degree range.

There are no typical December days here in Western Pennsylvania!

The animals that really suffer from these wild fluctuations in temperature are the larger mammals like the white-tailed deer. They have spent several months building up a remarkably insulating winter coat and fat layer ideally suited for cold, blustery weather. When we get a robust southern flow of air, though, and the temperatures go up thirty or forty degrees from normal, the deer’s activities become very limited, and they hide out in the shade of the nearby woodlots and orchards. Smaller mammals, though, like gray squirrels and cottontail rabbits do not seem nearly as impacted by the winter heat wave as the deer.

There is an ecological rule that might help us understand these observations.

Photo by Pixabay

“Bergmann’s Rule” (articulated by Carl Bergmann in the middle of the Nineteenth Century) states that larger sized individuals (of a species or among closely related species) are found in colder climates, and that smaller sized individuals are found in warmer climates. Many studies on endothermic (“warm-blooded”) species and ectothermic (“cold-blooded”) species have demonstrated the validity of Bergmann’s Rule for half to maybe two-thirds of studied species. Those statistics, of course, clearly illustrate numerous exceptions to this rule, but its fundamental premises and implications are still quite important.

Bergmann’s explanation of his observations concerned a phenomenon of three-dimensional geometry that was first articulated by Galileo: as a three dimensional object gets larger, its volume increases at a much large rate than does its surface area. Consequently, large objects (or we could say “large animals”) have a smaller surface area relative to their body volumes than do small objects (or, “small animals”). This is significant in the energy dynamics of an animal since a great deal of metabolic heat is radiated out through the surfaces of their bodies. So, an animal that needs to dissipate body heat (an animal living in a warm environment) would be able to accomplish this more easily if it was small (i.e. if it had a high surface area to body volume ratio), and an animal that needs to retain its metabolically generated body heat (an animal living in a cold environment) would be able to accomplish this more easily if it was large (i.e. if it had a small surface area to body volume ratio).

Photo by D. Sillman

Wolves, bears, foxes, wild boar, tigers, many birds (like the wild turkey (photo to the left) we saw regularly in our front yard last winter), and a number of species of deer all demonstrate body size increases with increasing latitude or increasing altitude of their habitats. Humans also have positive Bergmann Rule tendencies as can be seen in the blocky, heavy bodies of high latitude peoples (like the Inuit) compared to the long, lanky bodies of lower latitude people (like the Masai and Dinka of East Africa). The arms and legs of these warm climate people also tend to be longer than those people of the cold climates (which is a corollary ecological law to Bergmann’s Rule called “Allen’s Rule”).

But, when environmental temperatures fluctuate from cold to warm, and do so in highly predictable ways, would the larger bodied mammals of a cold region be selected against in favor of smaller bodied mammals that could better dissipate their excess body heat even through their layers of insulating hair and body fat?

One aspect of climate change may not so much involve warmer winter temperatures but a greater degree of temperature fluctuation throughout the season. These fluctuations might be observed through some Bergmann’s Rule (or even some Allen’s Rule) observations and measurements.

Greenland. Photo by Jensbn, Wikimedia Commons

Humans living on the southern edges of the expanded ice sheets during the last Ice Age were subject to powerful stimuli for biological and cultural evolution. Many of our current responses to the cold undoubtedly have their roots in this do-or-die evolutionary moment. Biologically when we are subjected to sustained cold we tend to crave and consume more high calorie (high fat) foods and use these abundant calories to fuel a higher metabolic rate and a more robust generation of body heat. We lay down more subcutaneous fat for surface insulation and even, in some peoples, increase the amount of fat wrapping around the internal organs. We shiver and use these muscle contractions to generate heat. We decrease the blood flow to our dermal blood vessels via vasoconstriction (but also set up a long-term oscillation of vasoconstriction followed by vasodilation so that the skin does not freeze and die). This varied vascular response is called the “Lewis Hunting Phenomenon.”

Photo by Aka, Wikimedia Commons

Culturally and behaviorally humans living in the extreme cold learned to construct warm shelters and make insulating clothing. They used fire (and a wide variety of fuels to maintain that fire) to heat their habitations and frequently clustered and slept closely together inside of these shelters. When they went outside they tended to maintain vigorous and continuous physical activity in order to generate high levels of metabolic heat. Many of these cold-adapted people also synthesized and drank alcohol to generate at least the illusion of being warm (alcohol dilates blood vessels to the limbs and to the skin and, thus, makes a person feel warmer. In reality, though, this dilation accelerates heat loss from the body and can, unless other mechanisms of heat retention are in place, have disastrous, even fatal, consequences!).

We are the product of mixed messages from our evolutionary history and from our culture and intellect. Our ability to add and then as needed remove layers of insulating clothing lets us glide through winter days that have wide variations in temperature. We do start craving fatty comfort foods, though, as the days get shorter and the temperatures get colder, and maybe even the occasional glass of a beverage containing alcohol. Maybe tonight I will make lasagna and have a glass of Chianti and something chocolaty for dessert. My Paleolithic genes are demanding it!



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Signs of Fall 13: Oysters!

Photo by M. Fischer

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In October, Deborah and I had the pleasure of sitting with our son, Joe, his partner, Marlee, and our daughter, Marian, at an oyster farm on the shore of Puget Sound shucking and eating raw oysters. We had a sense while we sat there of a bond with the ancient, human lineage of shellfish eaters. The movement of people from Siberia down the west coast of North America and into South America probably followed the lines of abundance of shellfish! We looked around at the bubbling water tanks and algae vats of the farm and watched their acres and acres of floating bags rise and fall with the waves and tides. We had so many questions (but mostly we were enjoying the great oysters!).

Let’s do some of the questions now!

What is an oyster?

Pacific oyster,. Photo by Pixabay

Oysters are  mollusks with two shells and an astonishingly simple anatomy. They have no head nor any other body segments, no brain, and no obvious sensory organs. On the inside of their protective shell is a tissue called the mantle that not only secretes the shell but also is full of blood vessels and is able to exchange oxygen and carbon dioxide between the oyster and its surrounding sea water. The oyster also has a prominent set of similarly very vascular, mucous covered gills that it uses to filter the incredible volume of water that it can pass through its open shell. These gills also exchange respiratory gases but even more importantly they gather up algae and other suspended materials from the water and pass them into the oyster’s quite inconspicuous mouth. At the other end of its very short digestive tract there is an even less conspicuous rectum and anus from which it excretes the non-digestible or non-absorbable solid waste. There is also a heart to push the clear blood through the blood vessels, some glands to assist digestion, two tiny kidneys to clean wastes from the blood, some reproductive organs that can change from testes to ovaries and back again with amazing speed, a couple of rudimentary neural ganglia and nerve cords, and a strong adductor muscle that contract and hold the shell tightly closed.

Where do oyster’s live?

Chincoteague Island, USFWS, Public Domain

Oysters live in the shallow shoreline and estuarian waters of most of the oceans of the world. They form large masses of shells in which one generation grows on top of the remains of the previous ones. Each type of oyster seems to be preferentially attracted to and to grow on the shells of its own species, so these great “oyster beds” or “oyster reefs” are often dominated by a single oyster species.

Oysters are a keystone species in their ecosystems. Their reefs generate protective habitats for a large number of vertebrate and invertebrate animals, and their constant intake and filtering of water greatly improves the water quality of their habitats. A single oyster can filter 50 gallons of water each day! Imagine the impact on water quality that one acre of oyster beds (about 750,000 oysters) can have!

How do oyster’s reproduce?

Oyster reef. Photo by Senckenberg Research Institute

When an oyster reaches one year of age its reproductive organs mature into sperm producing testes. Older, larger oysters that have built up significant metabolic reserves may have their reproductive organs transformed into ovaries which produce an astonishingly large number of eggs (up to 100 million) during the seasonal spawning. The production of this many eggs is extremely stressful on the “female” oyster! The trigger for the mass release of gametes in an oyster bed occurs when environmental temperatures reach about 68 degrees F (early summer). The spawning of a few oysters in the bed stimulates more and more oysters to release their sperm and eggs, and the water over the bed becomes cloudy with suspended oyster gametes.

Fusion of the sperm and egg forms a microscopic larva called a “veliger.” The veliger has cilia which it uses to swim about, a mantle which it uses to begin to make a tiny shell, and an eye spot that it uses to find a suitable substrate to attach to.  They also have a muscular foot that they use to crawl about on possible attachment surfaces. After two or three weeks the veliger attaches itself to something solid (often the old shells of oysters of its same species). This attached oyster larva is called a “spat,” and, if undisturbed, it will spend its entire lifetime growing in its attached site and cycling each year in the group spawning.

When an oyster is making eggs, its body changes under the metabolic stress. It becomes quite translucent and takes on an unpleasant, acidic taste. This is one of the reasons that natural oysters are not harvested in the summer (i.e. in the months without “R’s” (May, June, July and August). Oyster farming, though, through a variety of manipulations, has bypassed this summer restriction.

How do you farm oysters?

Oyster farm. Photo by Pixabay

Oyster farming takes the natural oyster life and reproductive cycle and manipulates the various stimuli and life stages to maximize growth rates and yields. Brood oysters have been developed that display specific genetic traits and physical features. The “stud book” for these brood lines is an extensive and complex set of documents! New genotypes from wild oyster strains are regularly incorporated into the breeding gene pool. These brood oysters are placed into large tanks with algae and nutrients and then carefully brought up to 68 degrees F. The warm temperatures simulate the onset of summer (regardless of what the actual month of the year it is!) and stimulate the brood oysters to release sperm and eggs. Fertilization, then, takes place in the water of the brood tank.

The veliger larvae then grow for about six weeks feeding on the algae of the tank. The larvae are constantly sorted and culled via filtration to make sure that a specific larval cohort is made up of individuals of similar sizes and also to get rid of any defective or slow growing individuals. When the larvae reach the appropriate size and development stage they are then given oyster shell materials so that they can attach and become spats.

These oyster shells can be in two forms: 1. Large, intact oyster shells (to which a large number of spats will attach thus forming what are called “shellstock oysters” (which are used in the commercial processing of oyster meats)), or 2. Small, sand-grain sized pieces of oyster shell (to which single spats will attach (this is how the individual oysters typically served in restaurants and bars are generated)).

The spats are then either spread on a suitable intertidal beach (a “Bottom Grow-Out” area) or suspended in bags or cages in inter-tidal zones (an “Off-Bottom Grow-Out” area). The beach “farm” is very simple to set up but may expose the oysters to predators or damage due to storms. The bags and cages are more complex to set up, but may be less impacted by predators and may offer the benefit of smoother and larger volume shells. The oysters stay in their grow-out areas for two or three years until they reach a suitable commercial size.

A very positive aspect of oyster farming in great contrast to most other types of maricuture is that there are very few negative impacts of the artificial oyster beds on the surrounding ecosystems. In fact, the water filtration benefits of the oyster mass actually improves the habitat quality around most oyster farming systems. Recognizing this filtration feature of oysters has led to the use of managed oyster beds in the effluent outflow of other, more potentially polluting fish and shellfish farming systems to the great benefit of system water quality.

Finally, oysters take on specific flavors when grown in specific estuaries or intertidal zones. The term “terroir” has been applied to this site-specific flavor development in wines, and a similar term, “merroir” has been coined for oysters.

“The time has come,” the walrus said, “to speak of many things…”

And , of course, he was talking to the many groups of four, fat oysters that he and the carpenter had taken for a walk on the beach and were about to greedily consume. We might have spent the column today talking about the symbolism of Lewis Carroll’s poem, but I prefer that we talked about oysters!



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Signs of Fall 12: More on Plastics

Photo from Grendz,com

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A little over a year ago I wrote a blog about plastics (Signs of Fall 4, 2017). Some key ideas from that post were: Plastics are human manufactured materials, they were invented 110 years ago, and they are large polymers of repeating organic subunits with very high molecular weights.

Humans have, so far, made 8.3 billion tons of plastics. That is enough plastic, according to Roland Geyer (University of California, Santa Barbara) in a recent Science Advances (July 19, 2017) paper, to cover the entire country of Argentina ankle deep in plastic materials. Geyer also notes that almost all of this plastic is non-degradable and will, along with all of the rapidly  accelerating yearly production of new plastics, be with us for many hundreds of years. The rate of acceleration of plastic synthesis is staggering! In 1970 global production of plastics was 30 million tons. In 2015, global production had risen to 322 million tons!

Most plastics are used once and then not recycled. In 2012, 26% of disposable plastics were recycled in Europe while only 8.8% of these types of plastics were recycled in the United States. Most plastics end up in landfills but many millions of tons a year pollute our oceans, land masses, and food webs They are even part of the pollution load in our atmosphere! We are conducting an unintentional, unregulated, global experiment in which we are covering the Earth in plastic and feeding it to a wide range of birds, fish and mammals.

Photo by hhach, Pixabay

Plastics out in our environment can be in large, macro-sized forms (like the visible plastic debris I described in the surfing picture at the Carnegie Natural History Museum’s exhibition on the Anthropocene (Signs of Summer 10, 2018), or the ocean-transported, plastic debris that I wrote about that befouls the beaches of the uninhabited Henderson Island out in the middle of the Pacific Ocean (Signs of Fall 4, 2017). Even more insidiously, though, plastics can be suspended and transported in both freshwater and marine systems in the form of microscopic pieces. These particles are coated with algae and attract zooplankton and larger consumers (like sea birds and marine mammals). The surfaces of these plastic particles also attract and accumulate a myriad of extremely toxic pollutants (including heavy metals, dioxins, PCB’s, DDT’s, and PAH’s) which then bioaccumulate in the organisms that ingest the plastic materials.

A very important study recently published in PLOS One (April 11, 2018) looked at drinking water samples from around the world and examined them for microplastic contamination. Researchers at the University of Minnesota School of Public Health and the State University of New York (SUNY) Fredonia sampled tap water from fourteen countries  (evenly divided between “More Developed” (MD) and “Less Developed” (LD) nations). A very large percentage of the samples (81%) had microplastic debris. Samples taken from locations in North America had the highest levels of microplastics (9.18 particles per liter) while samples taken from seven E.U. countries had the lowest (3.60 particles per liter). Water samples from MD countries had higher levels of microplastic particles than samples from LD countries in spite of assumed superiority of the MD countries’ water treatment facilities and technologies.

The authors of the paper estimated that, on average, each person in the world ingests over 5000 microplastic particles a year just from their consumption of drinking water.

This PLOS One paper also looked at two other human ingested products and analyzed them for microplastics. The first was sea salt. Sea salt is produced by the evaporation of sea water. Sea salt, like mined rock salt, is primarily sodium chloride but can also have small percentages of other chloride and even sulfate salts of potassium, magnesium and calcium. Sea salts also potentially contain the specific  microparticulate debris that were present in the original sea water. All brands of seas salt tested contained microplastic contaminates. There were between 46.7 and 806 microplastic particles per kilogram of tested sea salt.

Water and salt are two vital components of the human diet, and the microplastic materials found in each were very disturbing. Most news articles that reported the results of this study, though, never mentioned either of these very compelling observations. Instead, the third material that the PLOS One paper examined took over all of the headlines and discussion. This third comestible was beer.

Photo by egien, Wikimedia Commons

The PLOS One article built on a study of microplastics in German beer that had been published in 2014 in the journal Food Additives & Contaminants.  In this earlier study, microplastics and other contaminants were found in a variety of German beers. The average contaminant loads were 22.6 plastic fibers per liter of beer, 12 to 109 “solid fragments” per liter and 2 to 66 “foreign granules” per liter. The paper described a number of possible sources of this contamination that included atmospheric debris from inside the brewery or from outside air pulled into the brewing facility, gradual decay of materials used directly in the processing and filtration of the beer, or foreign materials associated with the bottles used to package the finished beer. Some of the foreign granules, they suggested, may have been sand particles from the spring water sources used in the brewing processes.

The Minnesota and SUNY researchers looked at beer from twelve breweries arrayed around the Great Lakes of the United States. Three of these breweries used water from Lake Superior, four used Lake Michigan water, one used Lake Huron water, two used Lake Erie water, and two used Lake Ontario water in their brewing. They found, on average, 4.50 plastic fibers per liter of beer but almost none of the solid or granule contaminants reported in the German study. They attributed these lack of coarse contaminants in the United States beers to the more intense filtration methods employed by most large, United States brewers. These extra filtration steps are designed to prolong the shelf-life of finished beer.

The PLOS ONE article stressed that there was no correlation between the levels of plastic fibers in the beers tested and the levels of plastic fibers in the municipal water supplies feeding into the breweries. The plastics, they suggest, came from within the brewing process rather than flowing in with the water.

This study made headlines all over the country: “Great Lakes Beers Contain Microplastics.” These news stories then triggered some energetic outpourings of disgust and outrage from large numbers of beer drinkers. Looking at the numbers, though, there is a very different end-story to this study.

  1. German beer had five times the load of microplastics in it (and much higher levels of “other” contaminants) than Great Lakes brewed beer.
  2. Sea salt, like the ocean itself, contains high levels of microplastic contaminants.
  3. Our tap water contains twice the level of microplastics than our beer!

I can just hear the neighbor at the party in the movie “The Graduate” telling Benjamin the secret to his future success: “plastics!” Were they drinking water or beer at the time?







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Signs of Fall 11: Honey Bees Are The Answer (But, What Was The Question?)_

Honeybee. Photo by I.Tsukuba, Flickr

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Honey bees (Apis mellifera), as we have discussed many times before, are an extremely important pollinator for many of the crop plants that make up our agricultural ecosystems. One third of the food we consume depends on honey bees for its pollination! The need for honey bee pollinators, often at a very specific time in the development of a crop and often for just a few short weeks, has increased right along with increased productivity of our industrial agricultural systems!

This growing need for honey bees has led to the development of an industry in which billions of hived honey bees are trucked about on flatbed trailers from one end of the country to the other in order to accomplish each region’s and each crops’ essential pollination. Along this yearly circuit of bee transportation the bees are also taken to areas where they can rest, recover and reproduce. According to the non-profit “Bee Informed Partnership,” though, about forty percent of these industrial bee colonies die each and every calendar year.

The causes of the bee colony deaths are varied: the stress of transport, the exposure to high load of pesticides and herbicides in the agricultural fields, infections with viruses and infestations with mites probably interact synergistically to kill off the colonies. The cost of this colony death rate is staggering, and this cost gets passed on to everyone who contracts with the bee industries for assisted pollination.

Beekeepers are developing ingenious ways to deal with mites and viruses and even transportation stresses, but they can do very little about the ever increasing levels of agricultural chemicals in the environment or about the shrinking reserves of natural vegetation upon where they formerly rested and refueled their colonies. Honey bees may be approaching the upper limits of what they can accomplish in our agricultural systems!

Almond grove. Photo by Pixabay

Wild bees and other insect pollinators have been shown in a number of published studies to be much more effective pollinators of crop plants than the “industrial” honey bees both in terms of numbers of flowers visited and amount of fruit or seed set. Also, when a crop is pollinated by both honey bees and some other bee species, there seems to be a synergistic impact on the efficiency of the pollination. This has been observed in almond orchards in California. Orchards with surrounding flowering plants supported a wild bee population that helped the “industrial” honey bees pollinate the almonds. It has also been observed in cherry orchards in Washington State.  Orchards produced twice as many cherries as they had in previous years after populations of native, blue orchard bees were established to augment the pollination work of the “industrial” honey bees.

Wild and alternative bee species gather and transport pollen in slightly different ways than honey bees, and the combination of these different types of pollen transport may make the overall crop pollination effort more efficient. These non-honey bee types of bees also have different flight patterns and activity levels within the branches of the nut and fruit trees and, thus, pollinate different flowers in different parts of the tree crowns. Wild and many alternative bees also readily work at temperatures that are too cool for honey bee activity.

A recent article in the New York Times (“Honey Bees Are Hurting,” August 21, 2018) listed four commercially available, alternative bees in the United States: the blue orchard bee, the bumble bee, the alfalfa leafcutter bee, and the ground nesting alkali bee.

Blue orchard bee. S. Leckie, Flickr

The blue orchard bee (Osmia lignaria) is a type of mason bee and displays many of the life cycle features that we have discussed before (see Signs of Spring 8, April 19, 2018). These bees are native to North America and readily pollinate fruit and nut trees during their month or two of spring activity. Females build their mud partitioned nests in a variety of types of holes  and readily use artificial paper tubes just like their eastern, mason bee relatives.  Populations of these bees and the timing of their emergence can be controlled by the manager of the orchard crop. The blue orchard bees used in the Washington State cherry orchard cost the cherry grower fifty cents each! Realizing that this cost could be avoided by providing the bees a safe place to construct their nests within or near the orchard, the cherry farmer took on the task of nurturing the bees. “If I double my cherries, I’ll do the extra work,” he said.

Bumblebee. Photo by Trounce, Wikimedia Commons

Bumblebees are any one of 250 species of bees all in the genus Bombus. Forty six of these Bombus species are native to North America. Bumblebees are robust pollinators that form small colonies (50 to 400 individuals). They are capable of traveling between one to two kilometers from their nests to find flowers. Bumblebees are important pollinators of tomatoes, pumpkins, squash, watermelons, blueberries and cranberries.

The alfalfa leafcutter bee (Megachile rotundata) is a European bee species brought to the United States specifically for the pollination of alfalfa. Alfalfa flowers are not easily pollinated by honey bees. The leafcutters are solitary bees that make tubular nests that they line with cut-up leaves.  Within the nests eggs and balls of gathered pollen and nectar are sealed up in chambers formed by the leaves. These bees are now found all across the United States in both managed and feral populations. In addition to pollinating alfalfa they also pollinate both fruit and nut trees.

The ground nesting alkali bee (Nomia melanderi) is a native North American species. Primarily found in the west and southwest, this solitary bee prefers to nest in soils enriched with salts. Alfalfa farmers, decades ago, found that if they disturbed or plowed up the surrounding salt flats near their alfalfa fields, productivity of their alfalfa crop greatly declined. These bees now are widely managed and encouraged through careful cultivation of their salty-soil habitats.

“Integrated Crop Pollination” is a public-private program funded in part by the Department of Agriculture. An important paper published in Basic and Applied Ecology in 2017 describes the objectives and structures of this new system of crop pollination. This program is exploring ways by which the presence of wild bees in our agricultural systems can be augmented. Logically, this will involve the establishment of wild, flowering plant areas in and around the agricultural fields. Providing a nursery and a refuge for wild pollinators may also result in improved habitats for the industrial honey bees! The program also wants to determine the best alternative bees for particular crops in different regions of the country. They are also planning to conduct experiments to try to determine the basis for the observed pollination synergies between honey bees and alternative bee species, and  to better understand the interspecific interactions between the honey bee and the myriad of wild and alternative bees.


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Signs of Fall 10: PA Pawpaw Patch

Photo by D. Sillman

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About three miles down the Roaring Run Trail is a dense copse of slender trees that stretch their long, thin branches and their dark, shiny green leaves out over the path. If you stop to look at them you can see the boundaries of the patch just up the terraced hillside and over to the edge of a fast running creek. If you then turn around you can also see that a few of these small trees (or, according to some authorities, large shrubs) are growing on the river side of the path, too, right down to the abrupt drop-off of the shoreline.

I can’t even begin to calculate how many times I have ridden past this cluster of trees over the years without noticing how different they were. A good friend had to point them out to me one afternoon when we were on a group ride down the trail.

These are pawpaw trees (let’s not call them shrubs even though they don’t show up in my dendrology or silvics books), and they are growing in a proverbial pawpaw patch!

Photo by D. Sillman

Pawpaws (Asimina trilobal) have a southern U.S. cachet to them, but they are naturally found all across the eastern half of the United States as far west as eastern-most Kansas and Oklahoma and as far north as southern Ontario. They are not terribly common across their wide, natural range and tend to grow in single species patches usually in relatively wet, bottom-land soils surrounded by mixes of other deciduous tree species. A quick glance at a few of the local names for the pawpaw gives you a sense of their broad distribution. The are called prairie bananas, Indiana bananas, Kansas bananas, hillbilly bananas, Michigan bananas, Missouri bananas and Ozark bananas (and more). The name “pawpaw” probably came from early European settlers who thought that it was the same species as the tropical papaya tree (which is also commonly called, to the great confusion of Internet searches, the “pawpaw”).

Pawpaws tend to grow in clonal patches that have formed via root sprouts from a single, or small group, of parental trees. The copse of pawpaws along the Roaring Run trail, then, may actually be the above-ground growth of a single individual.  That individual may have been planted here decades ago as a part of a surface mine rehabilitation project. The patch is growing in what looks to me like terraced mining spoil.

Young pawpaw seedlings are very sensitive to sunlight and must grow in the shade. Seedlings from root sprouts under mature pawpaw trees, then, would be self-shaded by the taller, older clones and would readily grow in an expanding, but sustainable dynamic and, eventually, form a large clonal patch.

Pawpaw flower, Photo by Kenraiz, Wikimedia Commons

The fruit of the pawpaw is one of the species’ great features. It is the largest fruit produced by a native North American tree and was highly valued by both Native Americans and European settlers. The fruit begins to form in the early spring, reddish purple flowers after they have been pollinated by a variety of flies (especially blow flies) and beetles (especially carrion beetles). That the pawpaw’s dominate pollinating insects are carcass decomposers gives you an idea of what the scent of its flower is like (it is delicately described as a “fetid” odor).

It is also said, possibly to explain the observation that wild pawpaw trees produce very few fruits, that pawpaws are unable to self-fertilize. That means that NONE of the clonal sprouts of a pawpaw patch can produce pollen that can fertilize any of the other clonal flowers! For a patch to produce fruit (and seed), it must have different genetic individuals close by that can exchange their pollen via their flies and beetles.

Pawpaw fruit. Photo by S. Bauer, USDA, Public Domain

The fruit starts out green in color and grows rapidly. By early autumn the fruits, which are really large berries, can be 2 to 6 inches long and 1 to 3 inches wide and weigh over one pound. The weight of the fruit pulls the slender upper branches of the pawpaw trees downward. When ripe the fruits turn yellow-green to brown and fall to the ground where, unless they are gathered up by humans, they are eaten by raccoons, opossums, squirrels and bears. The very large seeds of the pawpaw, though, are not easily swallowed by any of these animals and are, therefore, not readily transported in the animals intestines. The pawpaw, like the Osage orange and a number of other temperate and tropical tree species, are thought to have evolved symbiotic, seed dispersal relationships with much larger animals (like giant ground sloths and mastodons) which went extinct (probably due to human activity) in the late Pleistocene. These tree species, then, have no natural way to disperse their seeds and have consequently retreated into smaller and smaller actual growth ranges or patches (see Signs of Summer 11, August 11, 2016). Possibly in response to this aborted seed dispersion, the pawpaw now relies primarily on root sprouting and clonal reproduction (and clonal patch formation) for its propagation.

The pawpaw fruit has a very intense flavor variously described as a combination of a mango and banana with the texture of a custardy pudding. Ripe fruit must be handled very carefully to avoid bruising and damage. The fruits also ferment very rapidly and so must be eaten quickly or be frozen for preservation.  The spotty nature of fruit production and the fragility and lability of the fruit make pawpaws a difficult plant to grow in agroecosystems. Also, the need to grow the pawpaw seedlings in the shade for their initial growth years makes commercial orchard management difficult.

Photo by DE. Sillman

The pawpaw produces a number of secondary chemicals which act as protections against insect damage and vertebrate herbivory.  A major consequence of this is that pawpaw leaves, twigs and fruit are not readily eaten by white-tailed deer. In places with high numbers of deer, which readily consume most other tree species, pawpaw patches tend to expand. Possibly in our present day, “deer dominated” eastern U.S. forests, pawpaw trees will assume a greater and greater presence.

One specific secondary chemical (acetogenin) synthesized by pawpaw trees plays an important role in the lifecycle of a coevolved insect (the zebra swallowtail butterfly (Protographium marcellus)). The zebra swallowtail preferentially or possibly exclusively lays its eggs on pawpaw trees. The larvae (the caterpillars) that hatch from these eggs then feed exclusively on pawpaw leaves up until they metamorphose into adult butterflies. This exclusive feeding on pawpaw leaves causes the bodies of the caterpillars and also the bodies of the adult zebra swallowtails to be rich in the metabolic by-products of acetogenin. These chemicals, then, make both the caterpillars and the adult butterflies toxic to most potential predators. This plant-insect relationship is similar to the frequently described monarch butterfly and milkweed symbiosis that is so vital to the life cycle of the monarch.

So as the old folk song says (leaving out some of the repetition):

Where is dear little Nellie?

Way down yonder in the pawpaw patch!

Pickin’ up pawpaws and puttin’ in her pocket!

Pickin’ up pawpaws and puttin’ in her pocket!


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Signs of Fall 9: Puffins and Ponies

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MS Vandeem (Photo by D. Sillman)

In June, 2016 Deborah and I went on a St. Lawrence River cruise. We left from Montreal, traveled slowly down the river and out into the Gulf of the St. Lawrence. We then went into the North Atlantic and turned south along the Canadian and then U.S. eastern coasts. One of the aspects of this trip that excited me the most was the possibility of seeing large numbers of seabirds. However, as I wrote in a blog after we returned home, we saw almost none at all (Signs of Summer 4, June 23, 2016). The weather on the cruise was, to put it mildly, not very good. It was cold, rainy and blustery. Considering where we were traveling, we probably should have anticipated the cold and gloom, but all of that is 20-20 hindsight, of course.

On the cruise there were a number of extra excursions out into the surrounding countryside. One of these was an all day trip in some small, open boats to go up into a pristine shoreline outside of Charlottetown, Prince Edward Island with the stated goal of seeing puffins. It was a tough decision: on the one hand the sight of a puffin would be incredibly rewarding, but on the other hand it was cold and rainy and the seas were running very rough. There was also the extra $150.00 or so (per person) cost and a story from one of our new acquaintances on the cruise about going on this side-trip on a previous cruise and being terribly seasick. Also, they were in a boat whose guide forgot to pack the box lunches or water bottles. Now if you were seasick enough, I suppose lunch wouldn’t matter, but the excursion didn’t sound like much fun. So, we decided to tour Charlottetown instead, had a peaceful walk around the town and a wonderful lunch of clams and mussels (and local beers) at a harbor-side café.

Later that night on board the ship, we got into the elevator with a woman who was soaking wet and covered with mud. In between her shivering she reported that she had gone on the birding excursion. They hadn’t seen many birds, but eventually, thanks to the persistence of their guide (who had remembered to take the sandwiches and water with them!) they saw a single puffin swimming a few yards offshore from a rocky beach. They had spent eight hours in the open boat looking for it!

I asked her if it had all been worth it, and she said “yes, of course.” She then went to her stateroom for a hot shower and then, hopefully, something equally warming from one of the ship’s bars.

Photo by R. Bartz, Wikimedia Commons

In Halifax I bought a small statue of a puffin, and I have right here next to my computer. Puffins are the iconic birds of the North Atlantic, but recent surveys of their populations indicate that their numbers have dropped sharply over the past few decades. Puffins are still abundant (there are over eleven million adult Atlantic puffins scattered over their extensive European and Canadian North Atlantic range), but they are not nearly as many of them as there were twenty years ago. The rocky coast of Iceland shelters 60% of the world’s Atlantic puffins during nesting, and these numbers have dropped from seven million to just over five million birds during the Twenty-first Century.

Puffins are very long-lived birds. Life spans of forty years or more are quite common. Puffins spend most of the year as solitary individuals far away from land. They float on the ocean surface and eat fish. Their coloration helps to keep them safe out at sea: their white bellies make them nearly invisible to predators coming from below and their black backs camouflage them on the dark sea surface from potential aerial predators. They come onto land in the spring to lay their eggs in burrows that they often usurp from rabbits. They reproduce, though, quite slowly (they reach reproductive maturity at age four or five and lay only one egg per year), have a very long incubation interval (39 to 45 days) and an equally long nestling phase (another 34 to 50 days). During these three months of on-land existence the adult puffins can have a great deal of difficulty finding sufficient food for their nestlings.

Photo by S. Deger, Wikimedia Commons

Puffins are not strong fliers. They have very short wings that are more adapted for swimming than flying. Nesting puffins, though, often have to fly 60 miles or more in order to find suitable food supplies. This excessive energy outlay by the parents greatly stresses them! The puffin nestlings eat small fish and, locally, rely almost exclusively on sand eels that their parents bring to their burrows. Both fish and sand eel populations have greatly declined over the past two decades. This decline is attributed to the steady warming of the North Atlantic due to the combined effects of the warming phase of the North Atlantic Oscillation and human-induced global warming. Increasingly, researchers are finding puffin nestlings dead in their burrows apparently the victims of starvation.

Photo by J. Sweet, Wikimedia Commons

Down on the warmer beaches of the mid-Atlantic coast of North America are the barrier islands with their  populations of feral ponies. These ponies are thought to have come to these islands via shipwrecks in the 1500’s. The pony herds are able to survive even the most severe hurricanes by orienting themselves rump-end to the winds or by finding shelter in the higher elevations of the islands’ maritime forests. There is concern, though, that these pony herds will not be able to adapt to the combined climate change effects of rising sea level and increased incidence and severity of Atlantic hurricanes. The freshwater pools of the islands may become increasingly infused with saltwater and cease to be a suitable water supply for the horses.

In a 2008 paper published in Natural Areas Journal, John Taggart of the University of North Carolina Wilmington suggests that the barrier island pony herds be moved to mainland pastures both for humane reasons (the vanishing water supply on the islands) and for ecological reasons (the ponies by grazing on the dune grasses slow down the formation and decrease the stability of the critical sand dunes all across the island systems). These dunes are needed to guard the shoreline against the coming super-hurricanes of our Climate Change Era.

So puffin nestlings are starving and puffin adult are having to fly greater and greater distances to nurture their young. Quite possibly puffins will have to move further and further north to find sustainable and accessible food supplies for their nesting cycles. Barrier island ponies are under stress because of the vanishing supply of freshwater in their sand dune ecosystems, and the impact of the ponies on their islands’ sand dunes may be destabilizing the islands themselves in the face of the increasing number and intensity of destructive hurricanes.

As Heraclitus put it (as quoted by Plato in the Cratylus dialogue):

“Everything flows and nothing stays.
Everything flows and nothing abides.
Everything gives way and nothing stays fixed.
Everything flows; nothing remains.
All is flux, nothing is stationary.
All is flux, nothing stays still.
All flows, nothing stays.”

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Signs of Fall 8: Even More on Bees!

Bumblebee. Photo by Alvagaspar, Wikimedia Commons

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There is a lot of interesting research on bees being conducted at the Royal Holloway University of London. Previously, they determined that a commonly used pesticide inhibited the ovaries in bumblebee queens and more recently they have looked into the impacts of some new pesticides on bees and have also evaluated how bumblebees living in cities differ from bumblebees living in the country!

Their research on the impacts of the pesticide sulfoxaflor was published in Nature on August 15, 2018. Sulfoxaflor is a member of the Sulfoximine class of pesticides. Sulfoximines are being considered as replacements for the very commonly used neonicotinoid pesticides that have been shown to have very negative impacts on bees and other pollinating insects. Several neonicotinoids have been banned from use on agricultural fields by the European Union. Neonicotinoids have been shown to inhibit ovarian development in bumblebees (that was the Royal Holloway University study!), to interfere with the ability of honeybees to fly (and, thus, gather nectar and pollen), to reduce the winter survival rates in honeybees, to decrease the reproductive rates in bumblebees, and to make honeybee sperm less active (see Signs of Summer 4, June 26, 2018, Signs of Summer 11, July 7, 2017, and  Signs of Fall 9, November 3, 2016).

In this most recent pesticide study, captured bumblebees were fed a sugar solution containing 5 parts per billion of sulfoxaflor (a dosage estimated to be the exposure dosage in a sulfoxaflor-treated field) for two weeks. Those treated bumblebees and a similarly handled control group not exposed to the pesticide were then released back into their habitats. Later in the season the colonies were recovered and reevaluated. The bumblebees exposed to sulfoxaflor produced no new queens during the study period while 12% of the control bumblebees did produce queens during this time frame. The treated bumblebees also had a reduced number of worker bees compared to controls. The researchers stressed that although the bumblebee colonies “survived” the sulfoxaflor treatment, they were significantly stressed and reduced because of it.

Bumblebee at burrow. Photo by The Maddest, Public Domain

The “city bumblebee” vs. “country bumblebee” study was published in the Proceedings of the Royal Society B (June 27, 2018). Two hundred queen bumblebees were collected in a large park in Surrey, U.K. From these queens 40 bumblebee colonies were raised in the lab. These colonies were then placed in urban and rural habitats in and around London. Over several months, the research team visited each colony once a week and made observations and took measurements indicative of the health of each colony. The team found that the bumblebees in the more urban locations had fewer parasites, more offspring, a greater mass of accumulated food (pollen and nectar) in their colonial tube, and that the individuals in the city habitats lived significantly longer. The “city” bumblebees, then, on the basis of these multiple variables were much healthier than the “country” bumblebees.

There were a number of speculations as to why city environments might be healthier for bumblebees. These included an observed decrease in brood parasitism in the city bumblebees. Possibly this occurred because of the scent disruption by all of the odors of the city which made it much harder for brood parasites to find the bumblebees. Also there was an increased diversity and abundance of nectar rich flowers in the gardens of the city which may have provided the bumblebees with a more robust supply of food. There was also less pesticide use in the city environments which may have removed that important stress from the city bumblebees.

This study reminds me of the Michigan study that found bumblebees thriving in the city of Detroit compared to both smaller city environments and rural environments (see Signs of Winter 4, December 28, 2017). The abundance of suitable sites for soil burrows in the patchwork, abandoned lot urban landscape of Detroit was thought to be one of the main features that made the city more conducive to bumblebees than less urban locations.

Honeybees, Public Domain, Pixabay

And, finally, a team headed up by researchers at Penn State University (which also included a number of other universities and research institutions from the United States, India, Ukraine, Panama, and Kenya) have developed a new technique to rapidly and accurately evaluate a bee’s viral microbiome. This technique isolates viral DNA and RNA from a specimen bee and matches it to known viral sequences. The research group applied this technique to extractions from twelve bee species collected from nine countries around the world.

Bee viruses are a very important component in the stress matrix that can lead to Colony Collapse Disorder (C.C.D.), and most of the research on bee viruses have centered on the evaluation of the viruses in honeybees in light of this possible C.C.D. connection. Previous research has described 24 different viruses in honeybees. Some of these viruses seem to cause no harm to the bees while others can cause the death of individual bees or contribute to C.D.C.

The team found the suggestion of 127 viral sequences in their wide range of bee species. Of these total sequences seven were identified as common, previously described bee viruses, and twenty-seven were determined to be new bee viruses! Use of this viral assay technique should greatly expand our knowledge of the viruses that affect a very wide range of bee species!

Wow! Two weeks of bee information! “Industrial bees,” the impacts of proposed pesticides on bees, “city” bumblebees vs. “country” bumblebees, and new ways to study bee viruses! I also just saw on my local NPR station’s Newswire that beekeeping is being classified as a “cool” behavior by young people in Philadelphia! Craft beers, fusion foods, new music and bees! It’s all good!


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Signs of Fall 7: More on Bees!

Honeybee. Photo by C.J.Sharp, Wikimedia Commons

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When we say the word “bee” we probably have in mind the larger members of the seven families and 20,000 species that are classified as “bees.” Honeybees and bumblebees are the usual species that people recognize as “bees,” but they represent a very small number of the “bees” that are around us and upon which our natural ecosystems depend.

There are four thousand native species of bees in North America and several of these are bumblebees, but the honeybee is actually an alien species brought to North America by European settlers. Now, fortunately, we don’t append the second adjective “invasive” to the honey bee because they seem to carry out their life functions without impinging significantly upon the ecological niches of the native bee species. Honeybees are especially important for pollinating the large number of plant species that European settlers brought with them to form the foundation of our agricultural ecosystems! Honeybees, though, are not able to pollinate many of the plants that are native to North America. The often small, solitary native bee species are needed for that.

Bee species of all kinds are under a great deal of stress. Honeybees are suffering from Colony Collapse Disorder (C.C.D.) all over the world due to the synergistic impact of varola mites, viruses, pesticides and poor nutrition.  C.C.D. was first described in bee colonies in Pennsylvania ten years ago. Also, as I reported in July 22, 2017, 30% of bumblebee species worldwide are showing significant decreases in numbers. Climate change and parasitic infections are the two likely forces triggering these declines.

Photo by R. Moehring, USFWS, Flickr

Honeybees (which many states classify as “livestock” to emphasize their domesticated lifestyle) are tended by beekeepers who have developed increasingly elaborate methods to feed their bees in the face of the widespread loss of wild plants needed by the honeybees for good nutrition. The beekeepers have also developed techniques to reduce mite infestations, and to mitigate virus and pesticide exposures. All of these efforts have pulled the honeybee back from the brink of possible extinction that was threatened ten years ago by the 90% mortality rate in the widespread C.C.D. epidemic. Winter mortality rates, though are still nearly double the pre-2006 rates (28% loss vs, 15% before 2006).

In an article this month in the New York Times the ecology and technology of honeybees was described in great detail. The article (“The Superbowl of Beekeeping”) centered upon the largest honeybee pollination event of the year, the pollination of the almond trees in the central valley of California.

Almond flowers. Photo by M. Pixel

Almond trees are the first crop that flowers each year in California. Typically, in mid-February the one million (plus!) acres of California almond trees which will generate 80% of the world’s almond crop make flowers which must be pollinated by bees during their short (a couple of weeks) time frame of fertility. In 2018 two million colonies of bees were brought into the valley to accomplish this herculean task.

These billions and billions of imported bees represent two-thirds of all of the honeybees in the United States! The logistics and transport of these bees by bee-keeping corporations is complex and expensive but absolutely necessary.

These “industrial bees” typically overwinter in Texas or Florida and are brought into California for the February almond bloom on flatbed trucks. After the almond pollination they need to be removed from the groves so that the scheduled applications of pesticides on the almond trees do not decimate them. They may then be transported back to Florida or Texas to pollinate watermelons, or to Washington State to pollinate cherry or apple trees, or to Maine to pollinate blueberries. One third of the pants in our food supply-chain require bee pollination in order to produce their food crops.

In the warm summer months, these bees are often taken to cooler environs of the upper mid-west (like North or South Dakota) where the bee keepers feed them protein supplements and split the hives to stimulate queen formation and reproduction. These mid-western areas used to be rich with both alfalfa fields and wild range lands that were packed with weeds and wildflowers that provided the bees with a diverse base of natural foods. But more extensive agriculture, drought and also suburban expansion have reduced these wild plant areas considerably much to the detriment of the honeybees.

Bee colonies and the plants they depend on have also been harmed by natural disasters. The hurricanes in Florida, the drought in Texas and the wildfires in California have both killed bee colonies and also destroyed extensive areas of wild plants. As bee colonies have become more stressed they have also increased in value and have been subject to million dollar thefts and hijackings.

Almond grove. Photo by Pixabay

The California almond industry is the main driver of the industrial bee economy. Almonds generate $7.6 billion dollars a year for the California economy. Over 100,000 jobs are supported by almond production, distribution, and processing . The dependency of the almond growers on the bees is absolute.

Research into the effectiveness and efficiency of honeybee pollination of almond trees has generated some interesting observations. For example, it was found that when wild, flowering plants were planted in and around almond trees the attraction of native pollinators actually stimulated the honeybees to do a more efficient job in pollinating the almond tree’s flowers. Most almond growers, though, rejected this idea maintaining in spite of the evidence to the contrary that a nearby source of non-almond flowers would distract the honeybees and divert their pollinating efforts to these other plants.

A variety of self-pollinating almond tree has also been developed. These trees, then, would not require bees in order for them to set their nuts. The almonds generated by these trees, though, did not taste as good as bee-pollinated almonds. As one researcher put it, “I don’t know if bee honey from the almond grove hives tastes like almonds or if almonds taste like bees!”

There have also been plans drawn up for (and even patents applied for!) small drone, bee-robots that would mechanically transfer pollen from flower to flower on an almond tree. In March 2018, Wal-Mart applied for a patent for one of these bee-drone systems.

The ancient Egyptians carried bees hives up and down the Nile in order to pollinate crops of flowers. Other civilizations around the Mediterranean kept domesticated bees not only for honey but also to pollinate their crops. Industrial agriculture is producing exponentially more food than the simpler systems of the past. Let’s hope that they find a way to keep the bees active and viable in these new production systems.




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Signs of Fall 6: Changing Leaves

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Orange leaves

Photo by D. Sillman

I am waiting for the leaves to fall en mass from my trees. It is an event that occurs about the same time each year (sometime after Columbus Day but before Halloween), but every year it seems late in coming. I am not sure why I am always so eager to get on with the Fall, it just means that winter is closing in on us and that the color green is going away for five months!

Leaf loss is a purely “economic” decision for a tree. Leaves are a tree’s organs for photosynthesis and energy acquisition, but leaves also lose incredible quantities of water via transpiration. In the summer many tree species (like black locusts and the cherries) balance their needs for energy (for growth, reproduction, repair, etc.) with the necessity of maintaining an acceptable water balance in their tissues and cells. In wet summers, like this year, these trees can keep all of their leaves, fix abundant energy, and transpire water without damage. In dry summers, though, the limiting factor of water availability makes the tree give up some of its photosynthetic potential in order to maintain its water balance. In these dry years “Fall” actually starts in June or July!

With the approaching winter the leaves for all deciduous trees are shed primarily to help the trees to withstand the incredibly dry conditions of winter. This seasonal leaf loss also recognizes that the freezing of leaf cells’ cytoplasm and interstitial fluids would cause such widespread damage to the cellular  structures of the leaves that they would be incapable of any future photosynthesis.

Photo by D. Sillman

When deciduous trees get ready to shed their leaves, they undergo several well defined stages of change. First, in response to the length of the dark period of the day reaching a critical length, they begin to generate large numbers of cells right at the junction of the leaf’s petiole and its branch. These cells greatly increase in number but not, at first, in their individual sizes. This layer of cells (the “abscission layer”) slowly starts to interfere with the flow of sugars out of the leaf and the flow of nutrients into the leaf, and, so, sugar levels rise in the leaf and nutrient levels fall. The lack of nutrients causes the leaf to stop synthesizing new chlorophyll molecules. Chlorophyll is, of course, the functional pigment of photosynthesis and also the pigment that gives plants their characteristic green color. Initial cessation of chlorophyll production makes the leaves appear a bit paler and less intensely green than they were during the height of summer. Continued loss of the chlorophyll then starts to unmask the other pigments (the “accessory” pigments of photosynthesis: the carotinoids and xanthophylls) that had been present in the leaves all summer long. As these pigments are “revealed” the leaves then “turn” orange (from the carotinoids) or yellow (from the xanthophylls) before they finally fall. The accumulation of the sugars in the leaves also has an effect on eventual leaf color. These sugars stimulate the synthesis of anthocyanin pigments in the leaf. These pigments generate purple or bright red colors in the leaf and are thought to possibly protect the leaf (and particularly next year’s delicate leaf buds) from insect damage.

Photo by D. Sillman

The deciduous trees in our area are beginning to turn their autumnal colors. The breakdown of the chlorophyll and the revealing of the accessory pigments is inevitable in our climate zone. In some years, though, the intensity of the reveled colors is much more extreme than in other years. The weather patterns of the fall and of the preceding spring and summer all contribute to the magnitude of the final color response.

Good, healthy abundant leaves are favored if the previous spring had adequate rainfall. A normal to wet summer insures that a large number of leaves will persist intact through their active photosynthetic seasons. Warm, sunny autumn days combined with cool but not freezing autumn nights will maximize sugar production and anthocyanin synthesis in the leaves. These accumulating anthocyanins then give the leaves their brilliant red and crimson colors that are so important in defining a “good” color year in the forest!

The way this year is working out, we should have some very spectacular colors around us, and that is almost everyone’s favorite Sign of Fall!

Photo by D. Sillman

After the leaves fall from my trees, I usually rake them up into several large, strategically located piles around my yard and leave them to nourish the worms and beetles and other invertebrates that will shred and grind them up into food for fungi and bacteria. In the old days my kids and I would jump in the piles and further accelerate their fragmentation. Now I just rely on the worms to do the job with less noise and vigor. Through the next spring and summer birds (especially the robins and the cardinals) peck at and dig around in the leaf piles looking for insect larvae and earthworms. These leaf piles are a great source of nutrition for these hunters and gleaners. By the time the next fall rolls around, the piles are remarkably reduced in size and are ready to be renewed by freshly raked up leaves. One pile down in my orchard was kept in this yearly equilibrium for over twenty years. I eventually dug up the rich, humus that accumulated at the bottom of the pile and added it to the soil of my tomato patch.

In a forest, the fallen leaves spread out in a thin layer over a broad area. Earthworms start working on these leaves right away, pulling them into their middens and burrows, grinding them up with their muscular mouth-parts and gizzards, mixing them up with ingested soil, and defecating them out in nutrient rich, erosion resistant pellets. In soils without earthworms, numerous arthropods of many sizes begin to slowly chew away the leaf materials making a fine powder of organic residues enriched with bacteria. Both the worms and the arthropods are setting the table for the bacteria and fungi that then steadily work away at the less resistant molecules in the leaves. Like in my leaf piles, by the time the next fall comes around what’s left of the old leaves serves as a base for the new and the decomposition process grinds on.

So, enjoy the coming events of the Fall and make sure you use your leaves for the biological health of your yard!


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