Fall 2007 Update: Ship of Opportunity Data-Dominant Zooplankton Species
Phytoplankton color index from the Continuous Plankton Recorder transect across the Gulf of Maine is shown in the top panel. The color index reflects the relative abundance of larger phytoplankton retained by the silk filter. The index indicates that the abundance of large phytoplankton continues to decline in the Gulf of Maine as compared to high values observed in the 1970s and 1980s. Abundances of two species of copepods from the Gulf of Maine Continuous Plankton Recorder transect are shown in the lower graph. Adult Calanus finmarchicus, which is a key indicator species for ecosystem status in the Gulf of Maine, has recently increased after a period of lower values in the 1990’s. Smaller zooplankton, as exemplified by Oithonia spp., have decreased after a period of higher values in the 1990’s. These changes are indicators of shifts in community structure from larger bodied copepods, including Calanus in the 1980’s, to smaller bodied copepods in the 1990’s, including Oithonia, back to larger bodied copepods in the 2000’s. The increase in larger-bodied copepods coincides with an increase in total zooplankton biomass during the fall.