GUSTO Program 2010 Student Abstracts

Biogeographical and sedimentary distribution of pteropods on the western edge of the Gulf Stream off the coast of Charleston, SC
- D.J. Zurlo

The distribution of genera of pteropods, in the water column and sediments were compared and analyzed at five stations on the western edge of the Gulf Stream off the coast of Charleston, South Carolina.  Using meter net tows and Shipek grabs samples were taken in 20-25 m of water and in the seafloor sediments below each of the meter tows.  Any one of the genera Clio, Limacina, Creseis, Styliola, and Cavolinia could have been found.  The water column samples were filtered to size fractionation of 125 mm and relative abundances of genera were compared to other water column samples to determine if water column distributions differed at each of the sites.  Five cc’s of sediment for each Shipek station were filtered to a size fractionation of 500 mm and absolute and relative abundances were compared for each site to determine any differences.  Pteropods in the water column were concentrated and a relative abundance of genera was calculated and the abundances were compared between each meter net station.  An absolute abundance of the sediments was also calculated and qualitatively compared to the abundances in the water column.  Using ADCP current data the distance traveled by a shell from its meter net station was estimated to determine the accuracy with which the sediments represented the water column.  In the water column, Limacina exhibited 98% abundance at 004, 86% at 006 and 31% at 009, and Clio exhibited 2% abundance at 004, 14% at 006, and 69% at 009.  No data were collected for 002 and 005.  In the sediments total abundance for 002 was 1 individual/5 cc of sediment, 004 was 5/5 cc, 005 was 28/5 cc, 006 was 3/5 cc, and 009 was 2/5 cc.  The estimated distance traveled for 004 was 1.18 km, 2.48 km for 005, 0.64 km for 006 and 2.15 km for 009.  Discrepancies between 004 and 006 and 009 were most likely due to diel vertical migration.  That so few pteropods were found may have been due to shoaling of the aragonite compensation depth because of the organic rich sediments on the continental shelf causing an increase in CO2 concentrations at depth.  The sediments found at the seafloor should be representative of the sediments in the water column because of the relatively shorts distances estimated shells travel in the water.

Size Fractionation of Phytoplankton According to Nutrient Concentration Along the Cruise Track C-229
- Bobby Baranello and Alex Hoang

It is well established that the study of phytoplankton is extremely important to modern science. Phytoplankton play an extremely important role in primary production and nutrient recycling in oceanic environments. We sampled pico- (0.45 – 8.0 μm), nano- (8.0 – 20.0 μm) and micro- (>20.0 μm) phytoplankton in the subtropical South Carolina Coast, the Gulf Stream and the Sargasso Sea. Theoretically, we expected to see the size of phytoplankton decrease as we traveled from coastal waters to the Sargasso Sea. Instead, there seemed to be no correlation. We also expected to see the size of phytoplankton increase as depth increased, which was observed in our data. In this study, we determined the main contributors to the phytoplankton biomass and their distribution vertically and along our cruise track, C-229.

Ocean-Atmospheric Carbon Dioxide Flux in the Western North Atlantic
- Beatriss Calhoun and Lindsey Sydow

As anthropogenic carbon production increases, the amount of carbon dioxide in the atmosphere is increasing. Yet, atmospheric pCO2 (measured in parts per million) is not as high as it should be if the atmosphere was indeed holding all of the CO2 emmitted. Scientists have found that the ocean and terrestrial biosphere act as sinks for CO2. This paper studies the effects of temperature on CO2 sequestration in the Western North Atlantic. Results show a negative correlation between temperature and pCO2.

Geological evaluation of iceberg scour marks off South Carolina; Implications on paleo-currents, climates, and Gulf Stream characteristics at Georgetown Hole
- Brent E. DeArmond and Kristopher J. Enfinger

Iceberg impact scours, created by the release of icebergs during the deglaciation of the Last Glacial Maximum, are large bathymetric features found around Georgetown Hole, off the coast of South Carolina.  Described by Hartmut Heinrich, the deglaciation of the Last Glacial Maximum increased the amount of freshwater input in northern latitudes, which caused a strong southward flowing current, carrying icebergs.  This insertion of icebergs into the southern latitudes of the U.S. was allowed by a weakened and diverted paleo-Gulf Stream, caused by the decrease in sea level.  The icebergs reaching Georgetown Hole created bathymetric features including scours in linear and sinusoidal patterns, impact pits, and post impact sediment lobes.  The sediment lobes are deemed to be post impact features created by Gulf Stream transported sediments, due to the geometry observed in seismic profiles.  These features impact sedimentation, and have affects on the surrounding Tilefish habitat.  This is one of the first thorough examinations of icebergs rafting into southern latitudes of the East coast of the U.S..  From these scours new information on paleo-climate and current has been revealed, and information on fisheries management has been further inspected. 
College of Charleston

Describing the Deep Chlorophyll Maximum in the subtropical North Atlantic
- Erin Fannin

The Deep Chlorophyll Maximum (DCM) is a natural phenomenon that occurs in all bodies of water. There are multiple factors which determine the position of the DCM; light and nutrients are the principle factors. This is due to phytoplankton’s need for light and nutrients. Primary productivity and the DCM are associated in eutrophic bodies of water, while in oligotrophic ecosystems they might not be related. This study, which occurred over a 12-day period along a cruise track between Charleston, SC and Bermuda, examines the DCM in three regions: the southeastern continental shelf of North America, the Gulf Stream, and the Sargasso Sea. From this information, comparisons about the development and affects of the DCM were made in these three distinct regions. Results from this study suggest that light, not nutrients, has the greatest influence of DCM position in all regions, while density also demonstrated importance with regard to localization of DCM. The affects of DCM on the oxygen levels in the surrounding water column varied between regions, which was likely due to whether the DCM was the site of maximum primary production.

Distribution of Fossil Foraminifera in the Western Gulf Stream and Sargasso Sea off the Carolina Coast
- John Hildreth

Living planktonic foraminifera were studied during the late spring and early summer months on the western edge of the Gulf Stream along the Carolina continental shelf.  Distribution and abundances of their tests in the sediment between Charleston and Georgetown South Carolina were assessed. The Gulf Stream flows along the North American coast just north of Bermuda and transports approximately 31 SVs. of water and 1.3x1015 W of heat into the north Atlantic (Lund, 2006).  This powerful current is an important contributor to warm weather throughout the north Atlantic and brings foraminifera life. 
Sediment grabs of the surface sediments along the western edge of the Gulf Stream was used to determine the composition of foraminifera assemblages.  Sedimentary layers were also observed to determine the ocean floor habitat these microscopic organisms were preserved.  Research done on these creatures tests will not only be helpful in understanding the distribution of these zooplanktonic organisms and the characteristics of the water masses in which they live, but it also provides key information to help understand the fossil record of the past.  Furthermore, the assemblage’s proxy for the biogeographical parameters of past temperature and salinity can help to understand if a tropical/subtropical/transitional zone existed off the Carolina coast in the past.
The study’s main objective was to examine relative abundances of each species preserved on the ocean floor at 4 shelf edge locations as well as one mid-shelf station.  Using the relative abundances, there should be a correlation between the specimens sampled and diversity at each location.  The study should also narrow down exactly what the assemblage off the coast of South Carolina signifies about the present environment of the region.

Plastics: An Investigation of Distribution Due to Water Currents of the North Atlantic Ocean
- Daniel Hodge and Coti Phillips

The distribution of plastics was assessed across the Western Atlantic Ocean by measuring abundance, mass, and types of plastic in the
surface waters. Neuston samples were collected at 16 sites along the C229 cruise track in Continental Shelf, Gulf Stream, and Sargasso Sea
waters. 354 total pieces were collected resulting in an average abundance of 19,369 pieces/ km2. 91% of the pieces collected were
micro-size post-consumer fragments. Concentration of pieces was found to be increasing towards the center of the Sargasso Sea indicating
that plastics accumulate at the center of mega-scale mechanisms such as the North Atlantic Gyre. Knowing where plastics are distributed is
important when implementing counteractive strategies against the negative affects of plastic on marine environments.

Phytoplankton: Diversity and Abundance in Relation to Silicate and Phosphate
- Brittany Sapyta and Hollis Romanchik

This study was done to find diversity and abundance correlations between diatoms and dinoflagellates in relation to silicate/phosphate levels in the coastal shelf waters of the eastern United States, the Gulf Stream, and the Sargasso Sea. Phytoplankton samples were taken by a flow through system throughout the course track. Results suggest no correlation between silicate levels and diatom and dinoflagellate abundance, and no correlation between diatoms and phosphate. A negative correlation between dinoflagellates and phosphate was found. There was found to be no correlation between diversity and nutrient levels. However, further study is needed.

Diel Vertical Migratory Patterns of Zooplankton by Light Cues
- Stephanie Vogtman and Kirk Gillen

Zooplankton of the Gulf Stream were examined for their photoresponse correlating with diel vertical migration (DVM) patterns.    A Surface Photosynthetic Available Radiation (SPAR) was used to record each sunrise and sunset during the 14 day C229 cruise.  The data from the SPAR was compared to backscatter readings from the Acoustic Doppler Current Profiler (ADCP), which show the daily migrations of the zooplankton.  Additionally, a 333 µm Neuston net was used to collect zooplankton samples at midnight and noon to determine biomass and diversity of the different species.  Results suggest that zooplankton DVM is cued by irradiance at sunset.  The organisms practicing DVM are known to be traveling up the water column to feed in the absence of light so that they can avoid visual predators which reside in the same region as the phytoplankton on which they feed.