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Abstract
The roles of life history and behavior in the dynamics of dispersal, recruitment and population maintenance were investigated for a dense infaunal polychaete assemblage on the Kendall-Frost mudflat in Mission Bay, California. Polychaete life history features provided the framework for investigations of (1) the relevant scales and mechanisms of dispersal, (2) spatial and temporal predictability of species abundances in the plankton, during recruitment, and in the benthos, and (3) response to disturbance and community resilience. The polychaetes Pseudopolydora paucibranchiata, Polydora ligni, Rhynchospio arenicola, Streblospio benedicti, Exogone lourei, Fabricia limnicola and Capitella capitata, exhibited many shared life history traits which limit the spatial extent of dispersal.
Hydrographic studies and plankton surveys demonstrated that back-bay circulation is sluggish. Most larvae released on the Kendall-Frost mudflat are constrained to small-scale oscillations in back waters. Approximately 3% of planktotrophic larvae are transported out to sea and may experience longshore transport 100 km or more to the north or south.
Small-scale dispersal was examined by studying patterns of larval availability, recruitment into settling cartons and response to disturbance. Artificially defaunated sediment patches mimicked small-scale disturbance; a severe storm and raw sewage spill created an episodic large-scale perturbation. Rates and mechanisms of colonization were governed by development and mobility patterns. For Streblospio, Exogone and Fabricia, brood protection, reduced pelagic larval phases, and post-larval movements, particularly by brooding adults, permit rapid colonization of disturbed patches and result in maintenance of high infaunal densities. Pseudopolydora and Polydora larvae, though good dispersers, are highly seasonal and variable from year to year, depending on critically timed disturbance for successful colonization.
Within the dense assemblage, behavioral interactions mediate spatial pattern and influence the relative success of surface feeding species. Pseudopolydora exhibits intraspecific territoriality and interspecific interference with Fabricia and Streblospio feeding activity.