Zooplankton community grazing impact on a bloom of Alexandrium fundyense in the Gulf of Maine |
| |
| Institution: | 1. University Corporation for Atmospheric Research, Joint Office for Science Support, Visiting Scientist at Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA;2. Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA;3. University of Washigton, under contract to Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA;4. University of Washington Tacoma, Campus Box 358400, 1900 Commerce St., Tacoma, WA 98402, USA;5. Woods Hole Oceanographic Institution, MS#32, Woods Hole, MA 02543, USA;1. Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0226, USA;2. Ocean Sciences and Institute for Marine Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA;1. Ocean Sciences and Institute for Marine Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA;2. Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive #0226, La Jolla, CA, 92093, USA;3. Southern California Coastal Water Research Project, 3535 Harbor Blvd, Suite 110, Costa Mesa, CA, 92626, USA |
| |
| Abstract: | Shipboard grazing experiments were conducted in the Gulf of Maine and on Georges Bank during of June 2006 to estimate zooplankton community grazing impact on a natural bloom of the toxic dinoflagellate Alexandrium fundyense. Surface seawater samples containing natural populations of grazers and A. fundyense from 23 stations were incubated at ambient temperatures. Concentrations of A. fundyense after incubations were compared to those at the start of each experiment to determine net increases due to population growth, or decreases presumed to be primarily due to grazing losses. Abundances of both microzooplankton (tintinnids, oligotrich ciliates, rotifers, copepod nauplii and heterotrophic dinoflagellates) and mesozooplankton (copepod nauplii, copepodites and adult copepods, rotifers, marine cladocerans, and meroplankton) grazers in experimental aliquots were also determined. The total zooplankton community had minimal grazing impact on natural populations of A. fundyense at most stations. At 70% of the stations where grazing experiments were performed, there were no significant differences in initial and final concentrations of A. fundyense. This indicated that growth of, and grazing on A. fundyense were in approximate balance. At 2 stations, which had the highest A. fundyense abundances of the cruise (>104 cells l?1), % of the A. fundyense population grazed per day was significantly negative, indicating that net population growth of A. fundyense exceeded grazing losses. At 5 stations, which had low concentrations of A. fundyense (102–103 cells l?1), % of the A. fundyense population grazed per day was significantly positive, indicating that losses of A. fundyense due to grazing exceeded net population growth. For stations with significant differences between Initial and Grazed concentrations of A. fundyense, grazing had the greatest impact at lower concentrations of A. fundyense, and grazing impact by the larger mesozooplankton was inversely related to zooplankton abundance. There was no relationship between microzooplankton abundance and grazing impact on A. fundyense. Grazing exceeded growth only where A. fundyense abundance was low, and growth exceeded grazing only where A. fundyense abundance was high. The inverse relationship between grazing impact and A. fundyense abundance implies that grazing may be capable of retarding bloom development at low concentrations typical of the early stages of a bloom, but at higher concentrations once a bloom becomes established, either grazing maintains a balance with A. fundyense growth, or growth exceeds grazing losses at highest concentrations. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
