Cranberry Lake, New York. Photo by S. Conn, Flickr
(Click on the following link to listen to an audio version of this blog … Science and serendipity
Many years ago I was combing through scientific journals looking for some interesting articles to use in a summer course in micro-community ecology that I was going to teach up at SUNY-ESF’s Cranberry Lake Biological Station up in the Adirondacks. Leafing through one journal (this is long before everything was on-line) in the dusty stacks of the University of Pittsburgh Library, I came across an article with a very compelling title: “The decomposition of elephant carcasses in the Tsavo (East) National Park, Kenya.”
This article was published in the Journal of Arid Environments (March, 1978) and was written by Malcolm Coe of Oxford University.
Photo by A. Shiva. Wikimedia Commons
Coe and a team of co-workers had traveled to Kenya in November 1971 to study the invertebrate community involved in the decomposition of elephant dung. Unfortunately, the “short rain” season that should have ended in early November persisted making conditions for studying beetles and ants and termites impossible. Instead of just sitting about waiting for the weather to clear, though, Coe looked around and saw an opportunity for study: dead elephant carcasses (ironically, most of these elephants had died as a consequence of an extensive drought which the on-going, abundant rains that were thwarting Coe’s invertebrate ecology study had only just broken).
The paper was fascinating and outlined the stages of the physical and biological breakdown and recycling of these huge (six and half tons) animals. The clarity and detail of the descriptions were only surpassed by the fact the never once did the author mention the stench and reek of the carcasses! A British stiff upper lip, indeed! When a 13,000 pound opportunity knocks, go for it!
When I was a grad student at SUNY-ESF, I shared some lab and greenhouse space with a student who had come to ESF with a vague idea of studying something to do with trees. There was, though no funding available for such unfocused research, so she was left unfunded and unsupported in her graduate studies.
Mirex. Figure by NEUROtilar, Wikimedia Commons
A research opportunity for this student, though, came up because of a chemical spill and a large fish kill up on Lake Ontario. Mirex is an organochloride insecticide had been used to kill fire ants in the south. Mirex, though, was manufactured in New York State in Niagara Falls by the Hooker Chemical Company (the company made notorious by the disaster of Love Canal!)). Large quantities of mirex had seeped or poured out of Hooker’s manufacturing facility and ended up in Lake Ontario. The mirex then bioaccumulated in many species of fish including salmon leading to widespread debilities and fatalities. The State of New York had introduced Chinook salmon to Lake Ontario just a few years before in an attempt to establish both a commercial and a recreational salmon-fishing industry. Unfortunately, the salmon, being apex predators, accumulated significant mirex levels in their tissues, and any survivors were far too toxic to eat!
One of the questions that the EPA wanted studied was to determine the decomposition web spread of mirex from the tissues of a decaying salmon. Did the mirex enter decomposer organisms (like blow flies, for example) and then spread out across an ecosystem? If so, how significant is this toxic spread? There was just enough money behind this question to fund a Master’s student at ESF! It was an unexpected opportunity!
Chinook salmon. Photo by J. Larios, Wikimedia Commons
The experimental design for this study involved laying out 8, 25 pound (or so) wild, mirex contaminated Chinook salmon carcasses in the open greenhouse and noting and harvesting developing decomposing organisms (maggots etc.). for the weeks it took the salmon to rot away. The smell was incredible, gagging and nauseating, and the experiment seemed to go on forever.
The graduate student did finish her study, wrote her EPA report and her thesis. The last I heard of her, she was living in a trailer up near Lake Ontario. I bet the memory of the smell of decaying fish has never left her! In hindsight, though, two hundred pounds of rotting fish had to be nothing compared to tons of rotting elephant! I am glad that Dr. Coe was not sharing my greenhouse!
American beaver. Photo by Steve, Wikimedia Commons
I have written about beavers before (see Signs of Winter 8 (January 24, 2019) and Signs of Fall 3 (October 3, 2019). A few of the essential points about the keystone nature of beavers in their ecosystems:
- Beaver dams and ponds help to control high water flow rates in the spring, and they also store water to keep streams flowing in the summer.
- Beaver ponds slow down surface water flow rates sufficiently to allow the surface water to percolate down into ground water. This ground water, then, helps to sustain wide areas of plant growth even in seasonally dry climates. Along the Colorado River, for example, sites without beaver dams experience water table declines of two meters or more during a dry summer. These declines effectively remove water from the reach of the surrounding vegetative community. This results in a shrinkage of the riparian vegetation zone down to a narrow band of green very close to the streambed itself. In areas with beaver dams, though, dry season water table drops of only five centimeters are observed. This means that ground water is well in reach of plant roots over a wide area around the ponded stream. This allows extensive vegetation to flourish and sustains a wide range of animal life even during a very dry summer season.
- Beaver ponds improve water quality by facilitating sedimentation and the sequestering and processing of pollutants (including bacteria from the feces of wild and domestic grazing animals and nitrogen and phosphates from agricultural field runoff).
- Beaver dams also back up the large water volume flows in the spring so that soils far above the riparian plane get inundated and receive nutrient rich sediments during the spring floods! The ponds also generate areas of open water that support a wide variety of birds, mammals, insects and fish. Beaver dams and ponds have been shown in numerous studies to be extremely important to the overall abundance and success of wild trout and salmon populations throughout North America.
Crested Butte, Colorado. Photo by B.W.Schaler, Wikimedia Commons
In 2017, Christian Dewey, a doctoral student studying water and soil science at Stanford University, was up on the East River near Crested Butte, Colorado measuring nitrogen levels in the stream. Drought and reduced snow pack melt had led to sluggish water flow in the stream which, in turn, could lead to accumulations of nitrogen compounds in the stagnant water. These nitrogen compounds could then stimulate the growth of algae and lead to a harmful algae bloom (“HAB”). HAB’s, as I have discussed many times (see Signs of Winter 2, December 13, 2018, Signs of Summer 11, August 29, 2019, and Signs of Summer 16, September 17, 2020), can then deplete oxygen in the stream water leading to the death of fish and other aquatic species.
Beaver dam. Photo by wsiegmund, Wikimedia Commons
While Dewey was taking his water samples, a group of beavers built a dam across his study stream and ruined his experiments. He viewed this unexpected interruption, though, as an opportunity and kept taking water samples in the expanding pond spreading out behind the beaver dam. He found that as the nitrogen-rich water of the stream soaked into the surrounding soils, soil micro-organisms converted the nitrogen compounds in the stream water into nitrogen gas (N2) which then volatilized into the air. The impact of this augmented, community nitrogen metabolism was a 44% improvement in the system’s natural nitrogen cleansing capacity! In times of drought, beaver dams and beaver ponds are critical in maintaining high levels of water quality in mountain streams!
So, one has to keep one’s eyes open when one is off on a scientific quest. You never know when something unexpected like a dead elephant, or some poisoned fish or a beaver dam may pop up!