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Chapter 24

Freshwater Ecosystems

Dodds & Whiles

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FIGURE 24.1

Graphic representation of one of the first accountings of energy flux through an ecosystem. Flux rates in g-cal cm22 y21. The data are for Cedar Bog Lake. (Lindeman, 1942).

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FIGURE 24.2

Biomass (A), production (B), and production per unit biomass (C) of Silver Springs, Florida. Note that production is divided into respiration and growth. (Data from Odum and Odum, 1959).

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FIGURE 24.3

An Allen curve showing changes in density and individual weights of a cohort of animals over time. N is number and W is individual weight; subscript t and t 1 1 indicate points in time. Over time, the number of individuals declines (moving down the y axis; difference between Nt and Nt11 5  mortality) and individuals grow (moving left to right on the x axis). The sum of the new biomass created by survivors (represented by the light gray rectangle) and the biomass produced in the interval but lost to mortality (darker grey triangle) represent production for the time interval depicted. Total production for the cohort is the area under the curve; note that the area under the dashed line at the top would represent total production for the cohort if no mortality occurred.

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FIGURE 24.4

Diagram of nitrogen fluxes in a cold water spring (Mare’s Egg Spring) dominated by Nostoc, a nitrogen-fixing cyanobacterium. Fluxes are given in moles N year21. Note: Fluxes are measured so where the budget does not balance there are measurement errors. (Redrawn from Dodds and Castenholz, 1988).

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FIGURE 24.5

Benthic macroinvertebrates that burrow into layered sediments and accelerate nutrient cycling and movement of materials into the water column. Burrowing bivalve, crayfish, tubificid worms, and aquatic insect larvae mix O2 into the sediments through their activities. Surface-dwelling invertebrates increase turnover of microbial communities and increase sediment suspension. (Reproduced with permission from Covich et al., 1999).

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FIGURE 24.6

Ranges of documented respiration rates from various types of sediments. (Data from Kieft and Phelps, 1997).

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FIGURE 24.7

A diagram of nutrient spiraling in streams. S is the total spiral length, Sp is the time spent in particulate form in water column or the benthic zone and Sw is the average time spent in the water. Average velocity is greater in the riffle on the left, so spiral length is greater than in the pool at the right.

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FIGURE 24.8

Diagram of the river continuum concept. See text and Table 24.3 for explanation. (Modified from Vannote et al., 1980).

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FIGURE 24.9

A simple diagram of nutrient flux through a lake ecosystem. The system is represented as a two-compartment bioreactor with a pelagic zone and the benthic zone. (Modified from Covich et al., 1999).

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FIGURE 24.10

Diagram of carbon flux in Lawrence Lake, Michigan. (Data from Wetzel, 1983).

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FIGURE 24.11

Ranges and means of production by various ecosystems. (Data from Whittaker, 1975).

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FIGURE 24.12

Sediment deposition rates for wetlands. (Data from Schlesinger, 1997).

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FIGURE 24.13

Carbon biomass and flux rates for the Creeping Swamp ecosystem. Biomass values in g cm2 are listed in the compartment boxes, and flux rates in g C m22 y21 are in parentheses. (Data from Mullholland, 1981).

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FIGURE 24.14

Freshwater habitats aligned across gradients that drive ecosystem properties.

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FIGURE 24.15

Comparison of carbon flow pathways and trophic complexity of groundwater, wetland, lake, and stream habitats.