| Traditional views state that phytoplankton blooms support high secondary production and ultimately more abundant fishes. If this cascade occurs, tight trophic coupling must exist. This work investigated trophic coupling between primary and secondary production in Mobile Bay, AL and the northern Gulf of Mexico (NGOM). Primary production, Acartia tonsa egg production, R/D ratios, copepod ingestion rate, cephlathorax length and zooplankton community structure were taken in Mobile Bay (March 2000–February 2001) and the NGOM (August 2000). Environmental factors alleviated coupling signals year round in Mobile Bay. Another decoupler was gelatinous zooplankton predation. The NGOM, however, was highly coupled with both secondary production and trophic transfer efficiency correlated with primary production. Food limitation on the shelf may have contributed to the degree of coupling. Ingestion rate did not differ between the two systems, suggesting food quantity and quality limitation in the Gulf. Unlimited food conditions in Mobile Bay may encourage spawning, increase juvenile survival, and reinforce evolution of estuarine dependent species. Changes in the existing balance within a system like Mobile Bay could change the current degree of coupling and threaten the usefulness of it as a nursery ground. |
