The Protozoan‐Metazoan Trophic Link In Pelagic Ecosystems

Gifford, Dian J.

doi:10.1111/j.1550-7408.1991.tb04806.x

Cited by 222 publications

(115 citation statements)

References 81 publications

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“…The majority of studies that have examlned the nutritional importance of microheterotrophs have focused on pelagic consumers, such a s zooplankton (Gifford & Dagg 1988, Stoecker & Capuzzo 1990, Gifford 1991, Sanders & Wickham 1993. Trophic coupling between pelagic microheterotrophs and benthic suspensionfeeders is typically not considered in modern models of aquatic food webs (e.g.…”

Section: Diet Culturesmentioning

confidence: 99%

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Ingestion and assimilation of carbon from cellulolytic bacteria and heterotrophic flagellates by the mussels Geukensia demissa and Mytilus edulis (Bivalvia, Mollusca)

Da¹,

Newell²

1996

Aquat. Microb. Ecol.

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We I4C-labeled cellulolytic bacteria and 3 species of bacterivorous nanoflagellates and fed these cultured organisms to 2 species of intertidal mussels, Geukensia demissa and Mytllus edulis. using a pulse-chase experimental design under controlled laboratory conditions. Ingestion and assimilation of C from these rmcroheterotrophs by mussels were calculated from measured rates of defecation, respiration, excretion, and tlssue incorporation. The proportion of available C ingested by G. demissa did not dlffer significantly among bacteria (39%), heterotrophic flagellates (58%), or the unicellular algae Isochrysis galbana (66%), which was used as a reference diet. In contrast, M. edulis ingested a signlflcantly lower proportion (19%) of the small bacterla ( < l pm in diameter) than the larger ( 3 to 5 pm diameter) heterotrophic flagellates (58%). The efficiency with which G. dernissa assimilated C from I. galbana (77 %) was significantly greater than that from either bacteria (42 %) or heterotrophic flagellates (44%) M edulis assimilated bacterial C with significantly lower efficiency (21 96) than C from heterotrophic flagellates (62%) These results indicate that heterotrophic flagellates can contribute to the C requirements of both G. dernlssa and M edulis, however, only G. demissa is capable of assimilating a considerable amount of C from bactena.

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Section: Diet Culturesmentioning

confidence: 99%

“…I. galbana were enumerated with a hemaLaboratory mesocosm studies and field estimates of cytometer, inoculated at 70000 cells ml-l, and unibacterial productivity and heterotrophic flagellate bioformly labeled with 14C in f/2 culture medium (Guillard mass by Newel1 & Field (1983a) . 1991.…”

Section: Introductionmentioning

confidence: 99%

Ingestion and assimilation of carbon from cellulolytic bacteria and heterotrophic flagellates by the mussels Geukensia demissa and Mytilus edulis (Bivalvia, Mollusca)

Da¹,

Newell²

1996

Aquat. Microb. Ecol.

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“…It has been reported by many field studies that when omnivorous species dominate in assemblage, mesozooplankton or copepods (a major group of mesozooplankton) often prefer feeding on microzooplankton to phytoplankton due to larger sizes and higher nutritional quality of microzooplankton (e.g., Stoecker and Capuzzo, 1990;Gifford, 1991;Fessenden and Cowles, 1994;Atkinson et al, 1996;Nejstgaard et al, 2001;Zeldis et al, 2002;Calbet and Saiz, 2005;Liu et al, 2005b;Gifford et al, 2007). Predation on microzooplankton is also an important feeding strategy of omnivorous species that are able to switch their feeding behaviors to conquer food limitation or to survive during nuisance phytoplankton blooms in coastal waters (Kiørboe et al, 1996;Nejstgaard et al, 1997;Gifford et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Seasonal Variability of Mesozooplankton Feeding Rates on Phytoplankton in Subtropical Coastal and Estuarine Waters

2017

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In order to understand how mesozooplankton assemblages influenced phytoplankton in coastal and estuarine waters, we carried out a monthly investigation on mesozooplankton composition at two contrasting stations of Hong Kong coastal and estuarine waters and simultaneously conducted bottle incubation feeding experiments. The assemblage of mesozooplankton was omnivorous at both stations with varying carnivory degree (the degree of feeding preference of protozoa and animal food to phytoplankton) and the variations of carnivory degree were significantly associated with microzooplankton biomass (ciliates for the coastal station, both ciliates and dinoflagellates for the estuarine stations) and physical environmental parameters (primarily salinity). High carnivory was primarily due to high composition of noctilucales, Corycaeus spp., Oithona spp. and Acartia spp. Results of feeding experiments showed that grazing impacts on phytoplankton ranged from −5.9 to 17.7%, while the mean impacts were just <4% at both stations. The impacts were size-dependent, by which mesozooplankton consumed around 9% of large-sized phytoplankton while indirectly caused an increase of 4% of small-sized phytoplankton. Mesozooplankton clearance rate on phytoplankton, calculated from the log response of chlorophyll a concentrations by the introduction of bulk grazers after 1-day incubation, was significantly reduced by increasing carnivory degree of the mesozooplankton assemblage. The mechanism for the reduction of mesozooplankton clearance rate with increasing carnivory degree was primarily due to less efficient of filtering feeding and stronger trophic cascades due to suppression of microzooplankton. The feeding rates of mesozooplankton on microzooplankton were not obtained in this study, but the trophic cascades indirectly induced by mesozooplankton carnivorous feeding can be observed by the negative clearance rate on small-sized phytoplankton. Overall, the main significance of this study is the empirical relationship between carnivory degree and clearance rate, which allow researchers to potentially predict the herbivory of mesozooplankton in the nature without conducting feeding experiments.

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“…They are capable of grazing bacteria (Sherr and Sherr, 1994) and transporting bacterial biomass out of the microbial loop (Sherr and Sherr, 1988). They can grow at rates which equal or exceed prey growth (Sherr and Sherr, 1994) and can serve as a viable food source for metazoans (Gifford, 1991;Stoecker and Capuzzo, 1990).…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton growth, microzooplankton herbivory and community structure in the southeast Bering Sea: insight into the formation and temporal persistence of an Emiliania huxleyi bloom

Olson

Strom

2002

Deep Sea Research Part II: Topical Studies in Oceanography

143

108

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Using the seawater dilution technique, we measured phytoplankton growth and microzooplankton grazing rates within and outside of the 1999 Bering Sea coccolithophorid bloom. We found that reduced microzooplankton grazing mortality is a key component in the formation and temporal persistence of the Emiliania huxleyi bloom that continues to proliferate in the southeast Bering Sea. Total chlorophyll a (Chl a) at the study sites ranged from 0.40 to 4.45 mg C l À1 . Highest phytoplankton biomass was found within the bloom, which was a mixed assemblage of diatoms and E. huxleyi. Here, 75% of the Chl a came from cells >10 mm and was attributed primarily to the high abundance of the diatom Nitzschia spp. Nutrient-enhanced total phytoplankton growth rates averaged 0.53 d À1 across all experimental stations. Average growth rates for >10 mm and o10 mm cells were nearly equal, while microzooplankton grazing varied among stations and size fractions. Grazing on phytoplankton cells >10 mm ranged from 0.19 to 1.14 d À1 . Grazing on cells o10 mm ranged from 0.02 to 1.07 d À1 , and was significantly higher at non-bloom (avg. 0.71 d À1 ) than at bloom (avg. 0.14 d À1 ) stations. Averaged across all stations, grazing by microzooplankton accounted for 110% and 81% of phytoplankton growth for >10 and o10 mm cells, respectively. These findings contradict the paradigm that microzooplankton are constrained to diets of nanophytoplankton and strongly suggests that their grazing capability extends beyond boundaries assumed by size-based models. Dinoflagellates and oligotrich ciliates dominated the microzooplankton community. Estimates of abundance and biomass for microzooplankton >10 mm were higher than previously reported for the region, ranging from 22,000 to 227,430 cells l À1 and 18 to 164 mg C l À1 . Highest abundance and biomass occurred in the bloom and corresponded with increased abundance of the large ciliate Laboea, and the heterotrophic dinoflagellates Protoperidinium and Gyrodinium spp. Despite low grazing rates on phytoplankton o10 mm within the bloom, the abundance and biomass of small microzooplankton (o20 mm) capable of grazing E. huxleyi was relatively high at bloom stations. This body of evidence, coupled with observed high grazing rates on large phytoplankton cells, suggests the phytoplankton community composition was strongly regulated by herbivorous activity of microzooplankton. Because grazing behavior deviated from size-based model predictions and was not proportional to microzooplankton biomass, alternate mechanisms that dictate levels of grazing activity were in effect in the southeastern Bering Sea. We hypothesize that these mechanisms included morphological or chemical signaling between phytoplankton and micrograzers, which led to selective grazing pressure. r

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The Protozoan‐Metazoan Trophic Link In Pelagic Ecosystems

Cited by 222 publications

References 81 publications

Ingestion and assimilation of carbon from cellulolytic bacteria and heterotrophic flagellates by the mussels Geukensia demissa and Mytilus edulis (Bivalvia, Mollusca)

Ingestion and assimilation of carbon from cellulolytic bacteria and heterotrophic flagellates by the mussels Geukensia demissa and Mytilus edulis (Bivalvia, Mollusca)

Seasonal Variability of Mesozooplankton Feeding Rates on Phytoplankton in Subtropical Coastal and Estuarine Waters

Phytoplankton growth, microzooplankton herbivory and community structure in the southeast Bering Sea: insight into the formation and temporal persistence of an Emiliania huxleyi bloom

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