6
Seasonal Dynamics of Lipids in
Freshwater Benthic Invertebrates
Joann F. Cavaletto and Wayne S. Gardner
6.1. Introduction
Although there is a wealth of information on lipids in marine organisms, especially zooplankton (Kattner and Hagen, 1995; Tande and Henderson, 1988;
Clarke et aI., 1987; Lee, 1975; Lee and Hirota, 1973), relatively little information
is available on freshwater benthic organisms. The benthos of large temperate lakes
often experience a seasonal variation in food supply that is similar to the high to
midlatitudes of the ocean (Lee, 1975). For instance, in temperate large lakes the
diatom bloom that eventually settles to the profundal zone of the lake may be the
main source of high-quality food for the benthos during the year (Fitzgerald and
Gardner, 1993; Johnson and Wiederholm, 1992; Gardner et aI., 1990; Fahnenstiel
and Scavia, 1987).
The seasonal variation in lipid content of benthic organisms can provide clues
to the ecology of the organisms. The high energy content of lipids (39.35 J .
mg- I ) over proteins (23.63 J . mg- I ) and carbohydrates (17.18 J . mg- I ) make it
the most efficient energy-storing compound for most freshwater benthic organisms. To survive periods when high-quality food is not reaching the benthic
community, cold stenothermic benthic invertebrates often store energy as lipids
(i.e., triacylglycerols [TAG]) when food is abundant (Johnson and Wiederholm,
1992; Gardner et aI., 1990; Gauvin et aI., 1989; Gardner et aI., 1985a). The
seasonal lipid dynamics of an organism may also depend on their feeding strategy.
For example, some benthic animals feed at the sediment surface whereas others
feed below the surface. Consequently, animals may feed on particles at various
phases of decomposition and nutritional quality depending on their feeding mode.
In addition, the trophic state of the water body that the benthic invertebrates
inhabit may affect their lipid dynamics. Besides availability of food resources,
morphology, life history, habitat, and the reproductive state of a benthic animal
may contribute to its seasonal lipid profile.
In this chapter, we explore the seasonal changes of lipids in different benthic
invertebrates with emphasis on large temperate lakes. Seasonal lipid dynamics in
benthos from lotic environments is limited, so only minimal comparative information is provided on stream invertebrates. Because the location of benthic inverte109
Seasonal Dynamics of Lipids in
Freshwater Benthic Invertebrates
Joann F. Cavaletto and Wayne S. Gardner
6.1. Introduction
Although there is a wealth of information on lipids in marine organisms, especially zooplankton (Kattner and Hagen, 1995; Tande and Henderson, 1988;
Clarke et aI., 1987; Lee, 1975; Lee and Hirota, 1973), relatively little information
is available on freshwater benthic organisms. The benthos of large temperate lakes
often experience a seasonal variation in food supply that is similar to the high to
midlatitudes of the ocean (Lee, 1975). For instance, in temperate large lakes the
diatom bloom that eventually settles to the profundal zone of the lake may be the
main source of high-quality food for the benthos during the year (Fitzgerald and
Gardner, 1993; Johnson and Wiederholm, 1992; Gardner et aI., 1990; Fahnenstiel
and Scavia, 1987).
The seasonal variation in lipid content of benthic organisms can provide clues
to the ecology of the organisms. The high energy content of lipids (39.35 J .
mg- I ) over proteins (23.63 J . mg- I ) and carbohydrates (17.18 J . mg- I ) make it
the most efficient energy-storing compound for most freshwater benthic organisms. To survive periods when high-quality food is not reaching the benthic
community, cold stenothermic benthic invertebrates often store energy as lipids
(i.e., triacylglycerols [TAG]) when food is abundant (Johnson and Wiederholm,
1992; Gardner et aI., 1990; Gauvin et aI., 1989; Gardner et aI., 1985a). The
seasonal lipid dynamics of an organism may also depend on their feeding strategy.
For example, some benthic animals feed at the sediment surface whereas others
feed below the surface. Consequently, animals may feed on particles at various
phases of decomposition and nutritional quality depending on their feeding mode.
In addition, the trophic state of the water body that the benthic invertebrates
inhabit may affect their lipid dynamics. Besides availability of food resources,
morphology, life history, habitat, and the reproductive state of a benthic animal
may contribute to its seasonal lipid profile.
In this chapter, we explore the seasonal changes of lipids in different benthic
invertebrates with emphasis on large temperate lakes. Seasonal lipid dynamics in
benthos from lotic environments is limited, so only minimal comparative information is provided on stream invertebrates. Because the location of benthic inverte109