Export 3 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z   [Show ALL]
Roman, MR, Adolf HA, Landry MR, Madin LP, Steinberg DK, Zhang X.  2002.  Estimates of oceanic mesozooplankton production: a comparison using the Bermuda and Hawaii time-series data. Deep-Sea Research (Part II, Topical Studies in Oceanography). 49:175-192.   10.1016/S0967-0645(01)00099-6   AbstractWebsite

Mesozooplankton growth rates were estimated for the Hawaiian (HOT) and Bermuda (BATS) ocean time-series stations using the empirical model of Hirst and Lampitt (Marine Biology 132 (1998) 247), which predicts copepod growth rate from temperature and body size. Using this approach we derived seasonal and annual estimates of mesozooplankton production as well as rates of mesozooplankton ingestion and egestion using assumed growth and assimilation efficiencies for the period 1994-1997. Annual mesozooplankton production estimates at HOT (average 0.79 mol C m super(-2) yr super(-1)) were higher than production estimates at BATS (average 0.33 mol C m super(-2) yr super(-1)) due to both higher mesozooplankton biomass and higher estimated mesozooplankton individual growth rates. Annual primary production at the two sites was similar (average 14.92 mol C m super(-2) yr super(-1) at HOT and 13.43 mol C m super(-2) yr super(-1) at BATS). Thus, mesozooplankton production was a greater fraction of primary production at HOT (0.05) as compared to BATS (0.02). Mesozooplankton potentially contributed more to the gravitational flux of carbon at HOT, where the ratio of the average annual estimate of mesozooplankton fecal pellet carbon production/annual estimate of carbon flux at the base of the euphotic zone was 1.03 compared to the same ratio of 0.39 at BATS. Mortality estimates were similar to estimates of mesozooplankton production when compared over the entire study period. The higher mesozooplankton biomass and derived rate parameters at HOT compared to BATS may be due to the more episodic nature of nutrient inputs at BATS, which could result in mismatches between increases in phytoplankton production and the grazing/production response by mesozooplankton. In addition, there is evidence to suggest that there are periodic blooms of gelatinous macrozooplankton (salps) at BATS that may not be captured sufficiently by the monthly sampling program. Thus the gelatinous zooplankton would add to the overall grazing impact on the phytoplankton at BATS as well as the contribution of zooplankton to the gravitational flux of biogenic material via fecal pellet production.

Landry, MR.  2009.  Grazing processes and secondary production in the Arabian Sea: A simple food web synthesis with measurement constraints. Indian ocean biogeochemical processes and ecological variability. ( Wiggert JD, Hood RR, Naqvi SWA, Brink KH, Smith SL, Eds.).:133-146.: American Geophysical Union, Washington, DC (USA)   10.1029/2008GM000781   Abstract

The Joint Global Ocean Flux Study in the Arabian Sea during the mid 1990s provides a rare opportunity to elucidate carbon flows in the lower food web of an open ocean ecosystem. Analysis of that data to date has, however, produced widely divergent perspectives on major flux pathways and roles of zooplankton: from zooplankton as controlling grazers tightly coupled to microbial processes to zooplankton as casual consumers who let a large fraction of production, mostly generated by picophytoplankton, flow directly to detritus and export. Synthesis of experimental grazing rates and production inferences for mesozooplankton and microzooplankton fit well in a conceptually simple food web, constrained by measured carbon flows through phytoplankton and bacteria. Microzooplankton dominate grazing processes, consuming over 70% of particulate primary production (PP), on average, and providing steady and significant supplemental nutrition to mesozooplankton. Direct grazing estimates of mesozooplankton, on the order of 25% of PP, are sufficient to balance the remaining particulate production, with additional transfer through a one- to two-step food chain of microzooplankton accounting for a total ingestion of 6 40% of PP required for mesozooplankton secondary production. Dissolved organic carbon fluxes to bacteria are provided mostly within the constraints of gross and net primary production. Contradictory results from inverse models are likely due to an assumption that exaggerates by approximately twofold the production contribution of picophytoplankton and to the failure to use measured rates of gross primary production as a system constraint. Grazing generally balances net particulate primary production in the Arabian Sea, but true grazer control of phytoplankton dynamics remains an open issue for further study.

Decima, M, Landry MR, Stukel MR, Lopez-Lopez L, Krause JW.  2016.  Mesozooplankton biomass and grazing in the Costa Rica Dome: amplifying variability through the plankton food web. Journal of Plankton Research. 38:317-330.   10.1093/plankt/fbv091   AbstractWebsite

We investigated standing stocks and grazing rates of mesozooplankton assemblages in the Costa Rica Dome (CRD), an open-ocean upwelling ecosystem in the eastern tropical Pacific. While phytoplankton biomass in the CRD is dominated by picophytoplankton (<2-mu m cells) with especially high concentrations of Synechococcus spp., we found high mesozooplankton biomass (similar to 5 g dry weight m(-2)) and grazing impact (12-50% integrated water column chlorophyll a), indicative of efficient food web transfer from primary producers to higher levels. In contrast to the relative uniformity in water-column chlorophyll a and mesozooplankton biomass, variability in herbivory was substantial, with lower rates in the central dome region and higher rates in areas offset from the dome center. While grazing rates were unrelated to total phytoplankton, correlations with cyanobacteria (negative) and biogenic SiO2 production (positive) suggest that partitioning of primary production among phytoplankton sizes contributes to the variability observed in mesozooplankton metrics. We propose that advection of upwelled waters away from the dome center is accompanied by changes in mesozooplankton composition and grazing rates, reflecting small changes within the primary producers. Small changes within the phytoplankton community resulting in large changes in the mesozooplankton suggest that the variability in lower trophic level dynamics was effectively amplified through the food web.