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Structural-functional relationships in the pelagic community of the eastern
tropical Atlantic Ocean
Sergey Piontkovski1, 3, Robert Williams2,
Sergey Ignatyev3, Alexander Boltachev3, and Mikhail
Chesalin3
1 MSRC, State University of New York at Stony Brook, NY
11794-5000, USA.
2 Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1
3DH, UK
3 Institute of Biology of the Southern Seas, Sevastopol 99011,
Ukraine
Abstract
Sampling was carried out from the R/V "Professor Vodyanitsky” during
July to September 1987 on 4 transects at latitudes 6, 12, 18, and 24o W, from 6o
S to 4o N.
A total number of 81 stations were occupied where physical, chemical
and biological measurements were taken. Temperature, salinity, chlorophyll "a",
phytoplankton, primary production, bacterial production, micro-, meso-,
macrozooplankton and mesopelagic fishes and squids) were sampled in the upper
120m layer.
The biomass size spectrum of the plankton community was relatively
flat within the divergence zone but the slope of the size spectrum increased
towards the convergence zone. Higher turnover rates (the ratio of primary
production to the total community biomass) were observed in regions where the
size spectra were mostly sloped.
Primary production exceeded the community
metabolism by 3 to 5 times in regions where the size spectra were sharply
sloped. In regions with flat-type spectra (with slopes from -0.2 to 0) a balance
between primary production and community metabolism was observed.
The variation
coefficient and the dispersion index (the variance to mean ratio) indicated an
increase of the spatial variability of biomass in the sequence: "phytoplankton-mesozooplankton - macrozooplankton - micronekton".
At the higher trophic level of the zooplankton community, between the biomass of
squids and gelatinous zooplankton, a logarithmic linear relationship was
derived.
Squids actively consumed gelatinous organisms in regions of high
concentrations, although large copepods, euphausiids, amphipods, flying fishes,
and myctophid fishes also contributed to their diet.
Corresponding author. Email: spiontkovski@notes.cc.sunysb.edu
Journal of Plankton Research, 2003, vol.25, Iss.9, pp.1021-1034
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