HCNSO Student Theses and Dissertations

Defense Date

7-2010

Document Type

Thesis

Degree Name

M.S. Marine Biology

Second Degree Name

M.S. Coastal Zone Management

Department

Oceanographic Center

First Advisor

Amy Hirons

Second Advisor

Jonathan Shenker

Third Advisor

Alexander Soloviev

Abstract

Biological and physical sampling of a 10km long, east-west transect was performed during 2007, off the coast of southeast Florida. Temperature and salinity measurements were recorded using a conductivity-temperature-depth (CTD) sensor, and current direction and magnitude measurements were recorded using an acoustic Doppler current profiler (ADCP). Zooplankton samples were collected, during the daytime, using a Tucker multiple net mid-water trawl, with 760μm mesh, at intended depths of ~25m and ~200m, at three stations along the transect. Laboratory analysis indicated that several currents and water masses influenced the density distribution of calanoid copepods and chaetognaths. During April and September 2007, a Subsurface Counter Current existed in conjunction with an offshore meander of the Florida Current. Physical data confirmed the presence of Continental Edge Water and Yucatan Water occupying different spatial and temporal scales, and the boundary between these two water masses existed as the western boundary of the Florida Current. Temperature and salinity profiles confirmed that the Subsurface Counter Current was composed of Continental Edge Water and not Yucatan Water. Therefore, the Subsurface Counter Current observed during the transect was not a cross section of a passing eddy caused by the meandering front of the Florida Current. Densities of both taxa were highest in the Subsurface Counter Current and the Intermediate water, while the lowest densities are found in the Florida Current. Calanoid copepod and chaetognath densities exhibited typical zooplankton trends for tropical and subtropical coastal waters. Densities were highly influenced by the physical parameters of each month. Highest densities were observed in April and the lowest in July/September, typically the nutrient limited season. Analysis by location showed that the calanoid copepod and chaetognath densities were highest inshore and decreased offshore. The Florida Current exhibited the lowest densities for both taxa, while the Subsurface Counter Current and Intermediate water had higher densities. Previously documented southward flow had been associated with an offshore meander of the Florida Current, but during May and July there was a Subsurface Counter Current and an onshore meander of the Florida Current. Densities of both taxa were still lowest in the Florida Current. The stable isotope values of the zooplankton were skewed because of the preservation media and it was not possible to determine if the currents and water masses were isotopically different, and thus creation of a correction factor for the preservation effect was not possible. The δ13C values were variable in magnitude and direction from the control for each taxon. The δ15N values were less variable, but increased from the control, rather than decrease, as was expected for each taxon.

Comments

This project was funded by Calypso LN, LLC and GDF Suez Energy North America.

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