Multisensor sampling of pelagic ecosystem variables in a coastal environment to estimate zooplankton grazing impact

• Published in: Continental shelf research 2001, Vol.21 (1), p.69-87
• Main Authors: Sutton, Tracey, Hopkins, Thomas, Remsen, Andrew, Burghart, Scott
• Format: Article
• Language: English
• Subjects: Copepoda; Florida; Grazing; Larvacea; Marine; Ostracoda; Phytoplankton; Plankton sampling; Red tides; USA; West Florida shelf; Zooplankton
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/S0278-4343(00)00074-1

Sampling was conducted on the west Florida continental shelf ecosystem modeling site to estimate zooplankton grazing impact on primary production. Samples were collected with the high-resolution sampler, a towed array bearing electronic and optical sensors operating in tandem with a paired net/bottle verification system. A close biological–physical coupling was observed, with three main plankton communities: 1. a high-density inshore community dominated by larvaceans coincident with a salinity gradient; 2. a low-density offshore community dominated by small calanoid copepods coincident with the warm mixed layer; and 3. a high-density offshore community dominated by small poecilostomatoid and cyclopoid copepods and ostracods coincident with cooler, sub-pycnocline oceanic water. Both high-density communities were associated with relatively turbid water. Applying available grazing rates from the literature to our abundance data, grazing pressure mirrored the above bio-physical pattern, with the offshore sub-pycnocline community contributing ∼65% of grazing pressure despite representing only 19% of the total volume of the transect. This suggests that grazing pressure is highly localized, emphasizing the importance of high-resolution sampling to better understand plankton dynamics. A comparison of our grazing rate estimates with primary production estimates suggests that mesozooplankton do not control the fate of phytoplankton over much of the area studied (