Grazing and Food Size Selection of Zooplankton Community in Lake Biwa during BITEX '93.

Urabe, Jotaro; Kawabata, Keiichi; Nakanishi, Masami; Shimizu, Kensuke

doi:10.3739/rikusui.57.27

Cited by 26 publications

(21 citation statements)

References 11 publications

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“…In the offshore region, 1 mg DW of zooplankton removed, on average, 290 µg C of seston per day (Urabe et al 1995(Urabe et al , 1996. Seston removal rates in our study using phytoplankton collected from Nagahama Harbor are slightly lower but comparable, suggesting that inshore algae are grazed as efficiently as those in the offshore region.…”

Section: Incubation Experimentsmentioning

confidence: 48%

Effects of zooplankton on nutrient availability and seston C : N : P stoichiometry in inshore waters of Lake Biwa, Japan

et al. 2001

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Forty-eight-hour experimental manipulations of zooplankton biomass were performed to examine the potential effects of zooplankton on nutrient availability and phytoplankton biomass (as measured by seston concentration) and C : N : P stoichiometry in eutrophic nearshore waters of Lake Biwa, Japan. Increasing zooplankton, both mixed-species communities and Daphnia alone, consistently reduced seston concentration, indicating that nearshore phytoplankton were generally edible. The zooplankton clearance rates of inshore phytoplankton were similar to rates measured previously for offshore phytoplankton. Increased zooplankton biomass led to increased concentrations of nutrients (NH 4 -N, soluble reactive phosphorus [SRP]). Net release rates were higher than those found in previous measurements made offshore, reflecting the nutrient-rich nature of inshore seston. Zooplankton nutrient recycling consistently decreased TIN : SRP ratios (TIN ϭ NH 4 ϩ NO 3 ϩ NO 2 ). This effect probably resulted from the low N : P ratios of nearshore seston, which were lower than those commonly found in crustacean zooplankton and thus resulted in low retention efficiency of P (relative to N) by the zooplankton. Thus, zooplankton grazing inshore may ameliorate algal blooms due to direct consumption but tends to create nutrient supply conditions with low N : P, potentially favoring cyanobacteria. In comparison with previous findings for offshore, it appears that potential zooplankton effects on phytoplankton and nutrient dynamics differ qualitatively in inshore and offshore regions of Lake Biwa.

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Section: Incubation Experimentsmentioning

confidence: 48%

Effects of zooplankton on nutrient availability and seston C : N : P stoichiometry in inshore waters of Lake Biwa, Japan

et al. 2001

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“…Thus, although zooplankton cannot always utilize the production of large phytoplankton directly, they may use a large part indirectly by grazing on fungal zoospores and heterotrophic organisms in the microbial food web (Azam et al 1983). Because of such indirect processes, the sedimentation rate was low in Lake Biwa (Urabe et al 2005) when large inedible phytoplankton species dominated during summer.…”

Section: Discussionmentioning

confidence: 99%

To sink or to be lysed? Contrasting fate of two large phytoplankton species in Lake Biwa

Kagami

Gurung

Yoshida

et al. 2006

Limnology & Oceanography

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We estimated the contributions of sedimentation and cell lysis to the loss of two large phytoplankton species (Fragilaria crotonensis and Staurastrum dorsidentiferum) in Lake Biwa. Major loss process differed between species, and large phytoplankton did not necessarily function as a nutrient sink. The spring bloom of F. crotonensis was terminated by nutrient depletion and a subsequent increase in sedimentation rate. Although this species could be occasionally grazed by zooplankton, sedimentation eliminated nutrients from the surface. In contrast, the summer bloom of Staurastrum dorsidentiferum crashed mainly as a result of cell lysis caused by fungal infection within the surface mixing layer, which accounted for more than 75% of the mortality rate of this species. Cell lysis of S. dorsidentiferum may lead to nutrients within the surface mixing layer, supporting the production of bacteria and zooplankton. The different loss process of these two species implies that the function of phytoplankton in material flows cannot be assessed by cell size alone. Fungal parasitism can result in a different fate, which may play an important role in material cycling in lakes.

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“…Among the phytoplankton, Fragilaria crotonensis, a colonial diatom species, forms large blooms in spring, but Staurastrum dorsidentiferum, a large desmid alga, predominates from summer to autumn. Several studies have examined the effects of zooplankton on phytoplankton in Lake Biwa, including the effects of direct grazing (Okamoto 1984;Kawabata 1987;Urabe et al 1996), nutrient regeneration Elser et al 2001), and both grazing and nutrient regeneration (Yoshida et al 2001b). However, these studies focused mainly on total phytoplankton abundance, as quantified by chlorophyll-a or seston concentration.…”

Section: Introductionmentioning

confidence: 98%

Direct and indirect effects of zooplankton on algal composition in in situ grazing experiments

et al. 2002

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To examine both direct and indirect effects of macrozooplankton on phytoplankton species in Lake Biwa, we conducted in situ grazer-gradient experiments under different nutrient levels in summer, when Daphnia galeata dominated, and in autumn, when Eodiaptomus japonicus dominated. The experiments revealed that grazing pressure on phytoplankton was highly dependent on zooplankton species composition. Smaller phytoplankton species such as Stephanodiscus carconensis were more grazed when D. galeata was abundant, whereas large colonial diatom species such as Aulacoseira granulata were preferentially grazed when E. japonicus dominated. In addition, indirect effect of macrozooplankton through nutrient regeneration was suggested, although the magnitude of nutrient regeneration effects seemed to differ between D. galeata and E. japonicus. Specifically, growth rates of Sphaerocystis schroeteri were stimulated more by E. japonicus than by D. galeata. Macrozooplankton also enhanced the growth rates of colonial cyanobacteria such as Microcystis incerta, probably through decreasing the density of microzooplankton grazers (ciliates and rotifers). The results suggest that the effects of large zooplankton on phytoplankton populations are species-specific and cannot be understood without consideration of changes in abundance of other components of plankton communities.

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Grazing and Food Size Selection of Zooplankton Community in Lake Biwa during BITEX '93.

Cited by 26 publications

References 11 publications

Effects of zooplankton on nutrient availability and seston C : N : P stoichiometry in inshore waters of Lake Biwa, Japan

Effects of zooplankton on nutrient availability and seston C : N : P stoichiometry in inshore waters of Lake Biwa, Japan

To sink or to be lysed? Contrasting fate of two large phytoplankton species in Lake Biwa

Direct and indirect effects of zooplankton on algal composition in in situ grazing experiments

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