The impact of appendicularian grazing on natural food concentrations in situ1

Alldredge, Alice L.

doi:10.4319/lo.1981.26.2.0247

Cited by 114 publications

(81 citation statements)

References 23 publications

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“…Also absent are the impacts of relatively rare large salps. Pelagic tunicates generally have higher specific rates of water clearance and they feed closer to the base of the food web than copepods (e.g., Alldredge 1981;Diebel and Lee 1992;Madin et al 1997). Consequently, their impacts would need to be considered to arrive at a full accounting of mesozooplankton grazing at the study site.…”

Section: Discussionmentioning

confidence: 99%

Mesozooplankton influences on the microbial food web: Direct and indirect trophic interactions in the oligotrophic open ocean

Calbet

Landry

1999

Limnology & Oceanography

220

148

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The phytoplankton in warm oligotrophic regions of the open oceans is dominated by Ͻ2-m cells too small for efficient direct consumption by mesozooplankton. However, these primary producers are hypothetically linked to higher trophic levels via the cascading impacts of mesozooplankton grazing on intermediate consumers. To assess the magnitudes of these indirect trophic linkages, grazing experiments, involving different concentration treatments of the mixed mesozooplankton community, were performed during cruises in the subtropical North Pacific at station ALOHA. Mesozooplankton fed on a diverse assemblage of microzooplankton and nanoheterotrophs Ͼ5 m, and their predation indirectly enhanced net growth rates of phytoplankton and 2-5-m heterotrophs. Increasing the concentration of mesozooplankton also enhanced growth rates of heterotrophic bacteria, but this was more likely the result of organic enrichment than trophic transfer. Scaled to their natural abundance, the indirect grazing impacts of mesozooplankton on lower trophic levels are small, accounting for Ͻ0.005 d Ϫ1 of the growth rates of each prey category examined. Thus, the larger consumers appear to exert little net influence on the dynamics at the base of the food web. In contrast, size-fraction manipulations of consumers between 2 and 20 m (i.e., the nanozooplankton) elicited strong responses among bacterial populations indicative of tightly coupled predatory chain of at least two steps. Given the present results, detailed studies of the interactions among pico-and nanoplankton appear to be the most profitable avenue for improving our understanding of community structure and function in this region and for acquiring useful data for developing and validating ecosystem models of the open oceans.

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Section: Discussionmentioning

confidence: 99%

Mesozooplankton influences on the microbial food web: Direct and indirect trophic interactions in the oligotrophic open ocean

Calbet

Landry

1999

Limnology & Oceanography

220

148

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“…Formalin was added within 7 min from the start of the incubation, less than the gut passage time of O. dioica (ca. 8 min; Alldredge 1981;Bedo et al 1993). López-Urrutia and Acuña (in press) have measured gut passage times as short as 6 min for O. dioica at high FCs of I. galbana.…”

Section: Methodsmentioning

confidence: 99%

Functional response of the appendicularian Oikopleura dioica

Acuña

Kiefer

2000

Limnology & Oceanography

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Different concentrations of 14 C radiolabeled cultures of the prymnesiophyte Isochrysis galbana (5.5 m in size), the prasinophyte Tetraselmis suecica (9.5 m), and the chlorophyte Chlorella sp. (3.5 m) were offered as food to groups of 2-5 Oikopleura dioica to determine the response of clearance (CR) and ingestion (IR) rates to food concentration (FC for the prey I. galbana, T. suecica, and Chlorella sp., respectively. The K m values are high and in two of three cases exceed the maximum concentration of ingestible particles found in the natural habitat, which suggests that O. dioica is adapted to high phytoplankton concentrations. In contrast with classical FR models, CR remained nearly constant for all concentrations. Particles cleared from suspension by O. dioica are ingested and transformed into fast-sinking fecal pellets at low FC, while they are mainly accumulated into slow to fast-sinking filter houses at high FC, which implies considerable shifts in the biogeochemical role of these animals with changing particle concentrations.

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“…Although numerous studies have investigated the rates at which appendicularians can clear and/or ingest particles from temperate, subarctic and arctic waters (Acuña et al 1999, López-Urrutia et al 2003, Fernández et al 2004, only a handful have been conducted with warmwater species (Alldredge 1977, 1981, Sato et al 2004 and almost all utilized proxies for natural prey, such as latex beads or ink particles.…”

Section: Introductionmentioning

confidence: 99%

Grazing of two common appendicularians on the natural prey assemblage of a tropical coastal ecosystem

Scheinberg

Landry²,

Calbet³

2005

Mar. Ecol. Prog. Ser.

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The clearance rates of co-occurring appendicularian species, Oikopleura longicauda and O. fusiformis, in Kaneohe Bay, Hawaii, were investigated to evaluate and compare their roles in a tropical food web. Individual appendicularians were captured in situ and allowed to feed on the natural plankton assemblage for 60 to 180 min. Feeding rate estimates were based on flow-cytometry analyses of cell-density changes for heterotrophic bacteria (Hbact), Synechococcus spp. (Syn) and <13.0 µm autotrophic eukaryotes (Aeuks). Despite morphological differences, O. longicauda and O. fusiformis cleared the largest prey size-fraction at statistically indistinguishable rates. For the 3 prey categories (Hbact, Syn and Aeuks), mean clearance rates (± 95% CI) were 12 ± 7, 27 ± 6 and 34 ± 18 ml individual (ind.)-1 h -1 and 25 ± 12, 26 ± 15 and 38 ± 20 ml ind. , O. fusiformis can remove an almost equivalent amount (> 50%). Nevertheless, the consistently higher abundances of O. longicauda make this species a more significant link between picoplankton production and higher-level consumers (chaetognaths and fishes) in this coastal tropical embayment.

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The impact of appendicularian grazing on natural food concentrations in situ1

Cited by 114 publications

References 23 publications

Mesozooplankton influences on the microbial food web: Direct and indirect trophic interactions in the oligotrophic open ocean

Mesozooplankton influences on the microbial food web: Direct and indirect trophic interactions in the oligotrophic open ocean

Functional response of the appendicularian Oikopleura dioica

Grazing of two common appendicularians on the natural prey assemblage of a tropical coastal ecosystem

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