Effects of colonial morphology on zooplankton utilization of algal resources during blue‐green algal (Microcystis aeruginosa) blooms1

Abstract

Experiments were conducted to test the following proposed mechanisms whereby blooms of colonial blue-green algae (Microcystis aeruginosa) may more negatively affect large-bodied cladocerans than other zooplankton taxa: that colonial morphology most strongly interferes with the feeding of larger cladocerans, and that larger cladocerans more readily ingest toxic or nonnutritious colonial blue-greens. Experiments were conducted with both colonial and unicellular M. aeruginosa, in order to distinguish the effects of coloniality from chemical inhibitory factors associated with bluegreen algae. Experiments with colonial M. aeruginosa provided some support for both mechanisms, particularly with the cladoceran Diaphanosoma brachyurum. However, some small-bodied species associated with blue-green algal blooms did not conform to the proposed mechanisms, showing relatively strong reductions in clearance rates in the presence of colonial M. aeruginosa (Bosmina longirostris, Ceriodaphnia quadrangula) or relatively high consumption of colonial M. aeruginosa (Brachionus cafyciflorus, B. Iongirostris). Our results indicate that, contrary to earlier proposals, neither body size, taxonomic position, nor association with blue-green algal blooms are good predictors of the response to colonial M. aeruginosa.It has often been noted that blooms of colonial or filamentous blue-green algae are associated with changes in zooplankton composition, including losses of large cladocerans and increases in importance of smaller cladocerans, rotifers, and copepods (Gliwicz 1977;Edmondson and Litt 1982; Richman and Dodson 19 8 3; Orcutt and Pace 1984). Among the explanations for such changes in zooplankton composition is that the colonial morphology of the blue-green algae most strongly inhibits large-bodied cladocerans. Two major, but not necessarily mutually exclusive, mechanisms have been proposed for the greater susceptibility of large cladocerans to colonial or filamentous blue-green algae (Gliwicz 1977;Webster and Peters 1978). First, it has been suggested that colonial or filamentous algae clog the filtering appendages of larger cladocerans, reducing their feeding rates on co-occurring nutritious food sources or increasing their respiration rates or both. Several studies have supported this mechanism, showing that feeding or respiration rates of larger cladocerans are most strongly affected by the presence of filamentous blue-greens (Webster and Peters 1978;Richman and Dodson 1983; Porter and McDonough 1984). However, this mechanism has not been examined with more loosely organized colonial blue-greens, such as Microcystis aeruginosa. Moreover, these studies do not clearly demonstrate that the effects on feeding and respiration are due solely to the filamentous morphology; toxic or inhibitory chemicals produced by the blue-green algae could also contribute to the effect. Lampert ( 198 1, 1982) has shown that unicellular M. aeruginosa can strongly inhibit cladoceran feeding rates, presumably due to a chemical effect. Webster and...

Effects ofDaphnia-Associated Infochemicals on the Morphology and Growth ofScenedesmus obliquusandMicrocystis aeruginosa

“…Based on our results and some other studies (Hessen and van Donk 1993, Lampert et al 1994, LUrling 2003, we hypothesize that induction of colony formation in S. obliquus is probably widespread among herbivorous zooplankton and this has been confirmed to be an effective inducible defense mechanism against grazing by smaller sized herbivorous zooplankton (Mayeli et al 2004). Our result that infochemicals released from Daphnia could not induce colony formation in M. aeruginosa is consistent with the studies of Fulton and Paerl(1987) and Hesson and van Donk (1993). An effective way for S.…”

“…But chemicals released from Daphnia ambigua appeared ineffective as colony-inducing agents in M. aeruginosa (Fulton and Paerl 1987). Also chemicals released from Daphnia magna were ineffective in inducing Microcystis spp.…”

Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju(Cyanobacteria): variação semanal e relações com fatores ambientais em um reservatório eutrófico, São Paulo, SP, Brasil

“…Ainda que a herbivoria seja um importante fator regulador de populações fitoplanctônicas em geral, as cianobactérias, por seu tamanho relativamente grande, normalmente não são afetadas por herbívoros (Fulton & Paerl 1987, Pinto-Coelho et al 1999 e, portanto, este processo não foi considerado no presente trabalho.…”

Effects of nutrients and zooplankton on an estuary's phytoplankton: inferences from a synthesis of 30 years of data

“…Even if the maximum estimates of individual clearance rates are used, zooplankton are expected to have had little effect on phytoplankton during the early 1980s. One potential explanation for the relatively low abundances of zooplankton in the early 1980s could be that the blue-green algal blooms prevalent during that time may have prohibited zooplankton grazing and growth through toxicity or mechanical means, but this is not supported by experimental data (Fulton and Paerl 1987) or by corresponding zooplankton and blue-green abundances in monitoring data of the Chowan River (Mozley 1984). Alternatively, zooplankton abundance may have been suppressed by planktivorous fish, particularly adult and juvenile river herring, which feed heavily on zooplankton (Brooks and Dodson 1965, Hutchinson 1971, Burbidge 1974, Vigerstad and Cobb 1978, Domermuth and Reed 1980, Guest and Drenner 1991.…”