Environmental Science, 10th Edition (Cunningham)

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Overview: Measuring Energy Flows in Cedar Bog Lake, p. 63

Aided by his wife, Eleanor, Lindeman spent many hours collecting samples of aquatic plants and algae, grazing and predatory zooplankton and fish, and the benthic (bottom-dwelling) fauna of worms, insect larvae, crustaceans, and sediment. Back in the laboratory, he measured photosynthetic rates for the plants, respiration rates of the animals, and total energy content of organic compounds in each of the different trophic levels. This was the first empirical study of trophic levels in an ecosystem.

Describing the system in terms of energy flows was a radical departure from ecological methods at the time. Lindeman made a careful balance sheet of the total energy content in the biomass at each trophic level, the energy used in respiration, and the energy content of organic matter deposited in the sediment. To his surprise, he found that each successive feeding level contained only about 10 percent of the energy captured by the level below it. The remainder is lost as hear or deposited in sediments, he argued, because of the work performed by organisms as well as the inefficiency of biological energy transformations. In his dissertation, Lindeman showed that energy represents a common denominator that allows us to sum up all the processes of production and consumption by the myriad organisms in a biological community. Lindeman also broke from standard procedure by representing the relationships in his study lake as a mathematical model. A series of equations described thermodynamic relationships and the efficiency of energy capture and transfer. Ironically, Lindeman's most important paper was rejected by the journal Ecology as being too theoretical and too quantitative. It was only after the intercession of G. Evelyn Hutchinson from Yale, with whom Lindeman had a postdoctoral fellowship after finishing his studies at Minnesota, that his mathematical model and energy analysis of Cedar Bog Lake was finally published. Unfortunately, Ray Lindeman died of liver failure before his article appeared. It has since become a landmark in ecological history.

In the years since Lindeman's work, the idea of taking a systemic view of a biological community together with its physical and inorganic environment has become standard in ecology. Energy flows and nutrient cycles are central to the way we understand the workings of ecological systems. Constructing quantitative models to describe, explain, and explore ecological processes has become routine. In this chapter we will investigate the ways energy and matter are used by living things, and the ways these flows create relationships in ecosystems.

1			Use your measuring tool to determine the length and width of the lake, in meters. How big is it?
			A)	About 20 m by 40 m
			B)	About 50 m by 100 m
			C)	About 75 m by 150 m
			D)	About 100 m by 200 m
			E)	About 200 m by 400 m
2			Observe the bog and surrounding shoreline. What makes a "bog" unique from other types of lakes?
			A)	Bogs are larger than most lakes.
			B)	Bogs don’t have inlet or outlet streams.
			C)	Bogs are smaller than most lakes.
			D)	Bogs are deeper than most lakes.
			E)	Bogs contain saline water, rather than fresh water.
3			Why was it important that Lindeman studied a bog for his experiment, rather than some other type of lake?
			A)	Bogs tend to be cooler than other types of lakes.
			B)	Bogs tend to be hotter than other types of lakes.
			C)	The relative shallowness of bogs makes it easier to collect specimens.
			D)	Because bogs are relatively closed ecosystems, Lindeman could measure energy flows between compartments much more accurately and easily.
			E)	Bogs tend to be harder for humans to reach, reducing the potential for accidental contamination of the experiment.
4			In an intensive study of energy cycling, why is a small lake a good subject?
			A)	Small lakes are easy to find.
			B)	A small lake requires less energy to walk around.
			C)	A small lake makes sampling easier.
			D)	Small lakes tend to have fewer disease-carrying mosquitoes.
			E)	Big lakes tend to attract more people, which can impact the experiment's results.