Biological-Physical Interactions on Georges Bank: Plankton Transport and Population Dynamics of the Ocean Quahog, Arctica islandica

Losses of bank water because of strong winter wind forcing were hypothesized to he a factor limiting recruitment of Georges Bank communities. These alterations in bank trophic structure may reduce recruitment of higher trophic levels. NPZ and copepod stage structure models embedded in stratified flow over an idealized bank indicate that strong storms (13 m/s wind for 20 days) can cause replacement of bank water and loss of plankton. Arctica islandica on Georges Bank appear primarily below 50 meters and are densest on the South Flank. Observed age and size structures suggest only one cohort, spawned in 1986, was detected in 1982-94 surveys of the bank. Larval transport was modeled using tide and realistic winds from three winters. Variability in Ekman transport frequently overwhelmed tidal rectification and residual flow. Population model predictions were compared with NMFS survey observations; correlation of models with data was best for simulations from 1974 and 1991. Projection matrix eigenvalues were most sensitive to changes in adult and larval survival, planktonic duration and changes affecting the Northeast Peak. This work indicates (1) that winter wind variability alters plankton transport and (2) that interannual differences in recruitment and plankton dynamics may depend on that variability.