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Can filter-feeding fishes improve water quality in lakes? (2002)

HAMBRIGHT, K. D. ; BLUMENSHINE, S. C. ; SHAPIRO, J.

Oxford UK : Blackwell Science Ltd

Freshwater biology 47 (2002), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. In this paper we examine the potential of a cichlid fish species (Sarotherodon galilaeus) to both maintain positive growth rates through filter-feeding on phytoplankton and improve water quality in Lake Kinneret through suppression of dinoflagellate (Peridinium gatunense) blooms.2. Seasonal plankton consumption by S. galilaeus from Lake Kinneret was examined experimentally by monitoring changes in plankton assemblages during 24 h in 5-m3 mesocosms containing varying densities of fish. Taxon-specific grazing rates ranged from 0 to 17 mg gfish day–1, with mean total consumption of 1.6% fish body weight per day. During the spring bloom of P. gatunense, S. galilaeus consumed mostly (94%) netphytoplankton (≥20 μm). The remaining 6% consisted mostly of nanophytoplankton (〈20 μm). During the summer and fall, net- and nanophytoplankton accounted for 54 and 42%, respectively, of the diet of S. galilaeus. Zooplankton and flagellated and ciliated protozoans made up the remaining 4%.3. Simulations using a fish bioenergetics model indicated that consumption rates (C) were near maximum in spring (90%Cmax), while consumption was reduced in summer-fall (59%Cmax). Sarotherodon galilaeus obtains sufficient energy through filter-feeding year-round, although most growth (≥60%) occurs during the spring P. gatunense bloom.4. Despite efficient feeding on P. gatunense and nanophytoplankton by S. galilaeus, estimates of instantaneous plankton mortality caused by ingestion were two orders of magnitude lower than maximum potential plankton growth rates. Thus the potential for the S. galilaeus population in Lake Kinneret to positively affect water quality through algal suppression is low.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00840.x

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Body size and food web structure: testing the equiprobability assumption of the cascade model (2000)

Neubert, M. G. ; Blumenshine, S. C. ; Duplisea, D. E. ; [et al.]

Springer

Oecologia 123 (2000), S. 241-251

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ISSN: 1432-1939

Keywords: Key words Food webs ; Body size ; Cascade model ; Contingency tables ; Kernel smoothing

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The cascade model successfuly predicts many patterns in reported food webs. A key assumption of this model is the existence of a predetermined trophic hierarchy; prey are always lower in the hierarchy than their predators. At least three studies have suggested that, in animal food webs, this hierarchy can be explained to a large extent by body size relationships. A second assumption of the standard cascade model is that trophic links not prohibited by the hierarchy occur with equal probability. Using nonparametric contingency table analyses, we tested this ”equiprobability hypothesis” in 16 published animal food webs for which the adult body masses of the species had been estimated. We found that when the hierarchy was based on body size, the equiprobability hypothesis was rejected in favor of an alternative, ”predator-dominance” hypothesis wherein the probability of a trophic link varies with the identity of the predator. Another alternative to equiprobabilty is that the probability of a trophic link depends upon the ratio of the body sizes of the two species. Using nonparametric regression and liklihood ratio tests, we show that a size-ratio based model represents a significant improvement over the cascade model. These results suggest that models with heterogeneous predation probabilities will fit food web data better than the homogeneous cascade model. They also suggest a new way to bridge the gap between static and dynamic food web models.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420051011

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