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Distribution of the crustacean zooplankton in a subtropical estuarine system : implications for the predator-prey interaction between the primary and secondary consumers
Abstract
The spring and summer zooplankton community in East Lagoon, Galveston Island, Texas was similar to the summer assemblages of many U.S. estuaries. Species diversity was low and the crustacean zooplankton were dominated by a single calanoid species, Acartia tonsa. Length regression studies led to the suggestion that the community was at times food resource limited. Furthermore the available resources appeared to be ecologically partitioned both inter- and intra-specifically among the community members. Inter-specific partitioning of prey resources was also observed for larval and postlarval fishes entering the estuary. Diet overlap between zooplanktivores was low. Prey resources appeared to be partitioned across prey size distributions, habitat separations, and temporal foraging patterns. Within their respective foraging strategies, predators were essentially generalists and diets were well varied between individuals and over time. It still remains unknown whether the juvenile fishes were food limited. Weekly zooplankton densities and spatial distributions were highly variable. Spatial/temporal distributions appeared to be influenced by the active response of the zooplankton to environmental stimuli. The larger copepodids were concentrated in the deeper areas of the lagoon in the midday hours, presumably taking refuge from visual predators. Under seemingly stressful conditions such as reduced surface salinities, population densities of the smaller copepodids were observed to decrease in the surface waters while densities simultaneously increased in the deeper less environmentally variable areas of the lagoon. Horizontal distribution characteristics were asymmetrical, particularly in the spring along the windward shoreline. At this time most copepodid instars were substantially represented in the shallow nearshore waters. Consequently larval and postlarval fishes within the estuary were able to sample a concentrated prey resource in a lighted environment where protection from their predators and potentially higher growth rates were available. A wind driven circulation pattern resulting in a zone of divergence along the windward shoreline in the spring when the vertical temperature distribution within the lagoon was nonuniform was hypothesized to explain the zooplankton concentration. ...
Description
Typescript (photocopy).Subject
Biology1981 Dissertation L786
Predation (Biology)
Crustacea
Ecology
Estuarine ecology
Marine zooplankton
Collections
Citation
Livingston, Gerald Parker (1981). Distribution of the crustacean zooplankton in a subtropical estuarine system : implications for the predator-prey interaction between the primary and secondary consumers. Texas A&M University. Texas A&M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -646857.
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