Plankton abundance and dynamics across nutrient levels: tests of hypotheses

W.W. Murdoch, R.M. Nisbet, E. McCauley, A.M. de Roos, William Gurney

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

In lakes and reservoirs in which Daphnia is able to suppress the biomass of edible algae far below the level set by nutrients, the interaction is stable across the range of nutrient-poor to nutrient-rich environments. This phenomenon contradicts standard con sumer-resource models, which predict that dynamics should become increasingly unstable with enrichment. We test four hypotheses that might account for stability at high-nutrient levels: (1) greater abundance of inedible algae with enrichment interferes with Daphnia's feeding; (2) Daphnia's death rate increases with enrichment; (3) Daphnia's death rate increases with Daphnia density; (4) Daphnia's functional response depends on Daphnia's density. All hypotheses are rejected because they predict much higher biomass of edible algae at high-nutrient levels than is observed. Additional evidence on Daphnia death rates strengthens the case against hypotheses (2) and (3). We consider other hypotheses and conclude that three in particular would repay further investigation. (a) Inedible algae act as a nutrient "sponge," reducing the effective carrying capacity for edible algae; (b) limited spatial movement can enhance stability through a metapopulation-like effect, and (c) stochastic variation among individuals can be stabilizing. The central problem investigated here is a general one, with implications for many consumer-resource systems.
LanguageEnglish
Pages1339-1356
Number of pages17
JournalEcology
Volume79
Issue number4
DOIs
Publication statusPublished - Jun 1998

Fingerprint

algae
nutrient dynamics
Daphnia
plankton
alga
nutrient
nutrients
testing
functional response
individual variation
biomass
metapopulation
resource
nutrient-nutrient interactions
carrying capacity
sponge
test
lake
lakes
rate

Keywords

  • plankton abundance
  • nutrient levels
  • hypotheses
  • tests
  • daphnia
  • population dynamics
  • plankton
  • paradox of enrichment
  • models
  • freshwater

Cite this

Murdoch, W.W. ; Nisbet, R.M. ; McCauley, E. ; de Roos, A.M. ; Gurney, William. / Plankton abundance and dynamics across nutrient levels : tests of hypotheses. In: Ecology. 1998 ; Vol. 79, No. 4. pp. 1339-1356.
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Plankton abundance and dynamics across nutrient levels : tests of hypotheses. / Murdoch, W.W.; Nisbet, R.M.; McCauley, E.; de Roos, A.M. ; Gurney, William.

In: Ecology, Vol. 79, No. 4, 06.1998, p. 1339-1356.

Research output: Contribution to journalArticle

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T1 - Plankton abundance and dynamics across nutrient levels

T2 - Ecology

AU - Murdoch, W.W.

AU - Nisbet, R.M.

AU - McCauley, E.

AU - de Roos, A.M.

AU - Gurney, William

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AB - In lakes and reservoirs in which Daphnia is able to suppress the biomass of edible algae far below the level set by nutrients, the interaction is stable across the range of nutrient-poor to nutrient-rich environments. This phenomenon contradicts standard con sumer-resource models, which predict that dynamics should become increasingly unstable with enrichment. We test four hypotheses that might account for stability at high-nutrient levels: (1) greater abundance of inedible algae with enrichment interferes with Daphnia's feeding; (2) Daphnia's death rate increases with enrichment; (3) Daphnia's death rate increases with Daphnia density; (4) Daphnia's functional response depends on Daphnia's density. All hypotheses are rejected because they predict much higher biomass of edible algae at high-nutrient levels than is observed. Additional evidence on Daphnia death rates strengthens the case against hypotheses (2) and (3). We consider other hypotheses and conclude that three in particular would repay further investigation. (a) Inedible algae act as a nutrient "sponge," reducing the effective carrying capacity for edible algae; (b) limited spatial movement can enhance stability through a metapopulation-like effect, and (c) stochastic variation among individuals can be stabilizing. The central problem investigated here is a general one, with implications for many consumer-resource systems.

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