Date of Award

Winter 1-2018

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Ronald Kaufmann

Committee Co-Chair

Jennifer Prairie

Committee Member

Jennifer Prairie

Committee Member

Nathalie Reyns

Abstract

The vertical distribution of copepods in estuaries is known to vary in relation to environmental factors. However, the relationships between environmental conditions (e.g., tides, hydrography) and copepod distributions are not well understood. This project examined connections between environmental parameters and copepod distribution in Mission Bay, San Diego, California. Copepods (adults, juveniles, and nauplii) were collected every two hours over a diel cycle at three sites across the bay. A plankton pump was used to draw ~2 m3 of water from each of two depths - just below the surface and just above the bottom. Copepods were retained in a 100 µm mesh net, enumerated and identified to the lowest possible taxon. Results showed that the vertical distribution of copepods only varied over time at the front bay site, perhaps due to vertical migration on diel and tidal time scales. At this site, densities were highest in the bottom of the water column during night ebb tides and lowest in the surface and near-bottom samples during day flood tides. This result suggests that copepods were migrating between the near-bottom waters and the middle of the water column throughout the day. A strong oceanic influence was apparent in both hydrographic parameters and migration patterns in the front bay. Samples from the front bay site contained mostly coastal species, whereas samples from the mid bay site contained both estuarine and coastal species, while mostly estuarine species were identified from the back bay site. The results provide support that tides have a strong influence on copepod density in the front portion of Mission Bay and that both active and passive migration behaviors can be present within a species, depending on hydrographic conditions in a particular region of Mission Bay.

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