Biodiversity and abundance of the zooplankton of the Northeast Shelf ecosystem

Abstract

Since 1961, the Northeast Fisheries Science Center of the National Marine Fisheries Service has been conducting a study of the zooplankton of the US Northeast Shelf ecosystem. One of the objectives is to investigate ecological patterns of the system for any evidence of regime shifts and their effects on biodiversity and abundance of zooplankton and fish stocks. Two sampling strategies have been used: collections with Continuous Plankton Recorders beginning in 1961; and collections with bongo nets during the decade of MARMAP surveys (1977-1987), augmented by a time series of collections made during the autumn and spring groundfish surveys (1977-1993). The climate regime of the region leads to distinct and recurring seasonal pulses in zooplankton biomass and species succession in each of the four subareas of the shelf ecosystem distinguished. Evidence was detected in the analyses of inter-annual variability in species abundance and zooplankton biomass. However, no evidence of a large-scale regime shift of the magnitude described recently for other areas was detected from our analyses. Species shifts in abundance and the inter-annual and decadal variability observed in zooplankton biomass levels have allowed for sufficient residual sustainability in zooplankton biodiversity and abundance to support the recovery of depleted pelagic fish stocks.