Spring 2007 Update: Annual Zooplankton
The general trends in zooplankton biomass in all four shelf subareas resemble the shelf-wide average; however, the dynamic pattern of change in biomass level and internal variability in survey results are dramatically different among subareas. The northern subareas, GOM and GB, show a more conservative pattern of interannual change in biomass, suggesting zooplankton are responding to conservative forcing parameters and are well estimated. Zooplankton biomass in SNE and MAB vary widely year to year, which we believe reflects the dynamic nature of the circulation system affecting zooplankton in the region. Generally zooplankton appear to have declined during the early 1980s and have since slowly increased in biomass level. However, this pattern of decline is not the same among the subareas. On GB and in the GOM the decline in zooplankton was most pronounced in the 1980s, resulting in a relative decrease of nearly 50% in zooplankton biomass levels. The biomass in both subareas increased to levels close to 1970s high period between 2000 and 2005. The relative decline in SNE and MAB was more on the order of 20%. Similarly, the recent increase in zooplankton differs in magnitude among subareas. The decrease from 2000 to 2006 in the GOM and GB areas was on the order 10 and 4%, respectively, whereas the increase in SNE and MAB was on the order of 7 and 5%.