Title

Continental Shelf Food Chains of the Northern Gulf of Mexico

Document Type

Book Chapter

Publication Date

1-1-1991

Department

Marine Science

School

Ocean Science and Engineering

Abstract

Biological productivity in the northern Gulf is significantly affected by the Mississippi River. The freshwater discharge (577 km3 yr−1, approx 10% of the volume of water on the shelf) contains high concentrations of dissolved nutrients (100-150 μmol NO3 l−1). Flow is primarily constrained by prevailing winds to the continental shelf west of the Mississippi Delta. River plumes are regions of high phytoplankton stock (>30 g Chi l−1) and production (5 g C m−2 d−1), high copepod stocks (nauplius concentrations >1000 l−1) and high ichthyoplankton stocks (larval concentrations >50 m−3). The high temperature of shelf waters assures high physiological rates, implying high rates of trophic transfer and high turnover rates. The primary fate of phytoplankton production is grazing by macrozooplankton and microzooplankton. However, sinking of phytoplankton and other organic material fuels the annual development of a band of hypoxic water along the Louisiana coast. Fisheries production is high; the northern Gulf supports the largest volume fishery in the United States, the Gulf menhaden, Brevoortia patronus. The Loop Current in its northernmost position affects shelf processes to the east of the Delta. Anticyclonic rings derived from the Loop Current occasionally impact on the Louisiana shelf west of the Delta but usually drift over to the western Gulf resulting in exchange of oceanic and shelf water off Texas.

Publication Title

Food Chains, Yields, Models, and Management of Large Marine Ecosoystems

First Page

67

Last Page

106

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