Bay-Ocean Exchange Processes: Development and Application of a Meroplankton Tracer Technique
Abstract
Further advancement in understanding the dynamics of larval exchange between estuarine and coastal marine benthic invertebrate populations requires: (1) knowing the origins of field-sampled larvae, and (2) synoptic assessments of horizontal and vertical larval distribution patterns over large areas for extended periods. Larval concentration and water velocity data were sampled concurrently and used to estimate larval flux rates between regions of San Diego Bay (SDB) and nearshore coastal waters in southern California. Simulations with a 2-D hydrodynamic model of SDB indicated widely differing larval transport probabilities depending on whether tidal vertical migration behavior occurs in the water column. Field studies indicate that crab (Pachygrapsus crassipes) zoeae migrate vertically in SDB, a behavior that promotes transport out of the Bay. In contrast, larvae of other crab species (Lophopanopeus spp.), which do not migrate vertically, are retained within SDB during development. An elemental larval fingerprinting technique (based on Cu, Zn, Al, Mn, and Sr) was developed to distinguish SDB from non-SDB spawned P. crassipes zoeae. With this method, bi-directional larval exchange was observed between SDB and coastal waters. Approximately 26% of P. crassipes larvae observed at the SDB entrance, and 5% at a mid-bay site, originated outside the Bay. This exchange is likely to have significant consequences for larval populations. Laboratory experiments revealed reduced survivorship in larvae spawned from or reared in SDB water relative to pristine coastal waters. Combined use of trace elemental fingerprinting and synoptic field methods can facilitate understanding of larval transport and ultimately population dynamics of coastal species.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 09, 1999
- Accession Number
- ADA370651
Entities
People
- Lisa A. Levin
Organizations
- Scripps Institution of Oceanography