Seasonal Variation of Water Column
Chemical and Physical Properties across the Continental Shelf, Charleston Transect
-Caroline Dietz, Leg 02
In order to begin to understand the dynamic regime of the Charleston Transect,
water column chemical and physical properties were analyzed and compared for
the months of November 2003 and May 2004. Water column profiles were created
for temperature, salinity, chlorophyll, and density using data gathered from
CTD casts taken from nine stations along the mainline of transect. In November
2003, winter mixing was evident in the inner and mid shelf, outer margin, and
surface waters of the upper slope. A thermocline, pycnocline, and halocline
were all observed at approximately 80m water depth, giving evidence of the permanent
thermocline that forms the base of the surface layer. Waters in May were observed
to be stratified in the middle shelf, outer margin and upper slope. The inner
shelf shows little variation between mixing and stratification, thought to be
due to its proximity to the coast. Profiles showed temperature to be the primary
factor causing stratification in the water column. Chlorophyll showed no patterns
of distribution reflecting stratification, regardless of season.
School of Science and Mathematics Annual Student Research Poster Session,
College of Charleston, 2005
November Water Column Phosphate
(PO4 3-) Concentrations Across the Continental Shelf off Charleston, SC
-Brett Floyd, Leg 01
Phosphate nutrient concentrations within the water column are important for
biological productivity. Coastal areas often have a higher concentration of
phosphate present as compared to outer continental shelf waters because of riverine
and anthropogenic input. To test for this, water samples were collected aboard
the research vessel Savannah during November 2003 using a CTD and Niskin rosette
ranging in depths from the surface to a max of 150 meters from just off the
coast of Charleston, across the continental shelf, and into the Gulf Stream.
Phosphate concentrations from these water samples will be measured on a UV-VIS
spectrophotometer using standard colorimeter techniques. The results from these
tests will show the concentration of phosphorous present across the continental
shelf off the coast of Charleston, South Carolina.
POSTER
Biogenic Sulfur Production in Waters
Over the Continental Shelf Off the Coast of Charleston, SC
-Nathan Garcia, Leg 01
For years scientists have been struggling to balance the global sulfur
budget. Estimates show that a sulfur compound known as dimethylsulfide (DMS)
contributes approximately 50% of the biogenic sulfur input to the atmosphere.
This radiatively active compound is produced largely by phytoplankton (dinoflagellates
and haptophytes) and can increase the reflectance of light off the earth’s
atmosphere (albedo), potentially affecting global climate. While it has been
hypothesized that dimethylsulfoniopropionate (DMSP, a precursor to DMS) producing
phytoplankton have the ability to regulate light levels reaching the ocean’s
surface, the exact significance of its cellular production is not well understood.
Recent studies support the hypothesis that these sulfur compounds may be part
of an anti-oxidant system. In accordance with this hypothesis, cellular DMSP
production should increase in response to oxidative stressors such as high light,
low iron, and low CO2 levels. Understanding the cellular function of this compound
is becoming increasingly important as global CO2 levels continue to rise. This
study will examine the production of particulate DMSP (DMSPP) at the ocean surface
and at depths where 50% and 1% of the surface light level occurs. Water samples
were filtered on board the RV Savannah over the continental shelf off the coast
of Charleston, SC. Laboratory analysis of DMSPP was performed using gas chromatography
by measuring the total DMS evolved when reacted with sodium hydroxide. Concentrations
of DMSPP normalized to estimates of primary production (chlorophyll a) are expected
to increase with increasing light levels.
POSTER PhotoDocumentary
Fall Chlorophyll Maxima Depth Across
the Continental Shelf off Charleston, South Carolina
-Amanda Thomas, Leg 01
Phytoplanktonic organisms are the main primary producers in marine surface waters.
In temperate climates, their vertical distribution in the water column is determined
by summer stratification that occurs concomitant with a shallow thermocline.
This stratification disappears during the fall as turbulence due to fall storms
increases and air and surface temperatures decrease. This study measures phytoplankton
accumulations at specific depths over the continental shelf off South Carolina.
Phytoplankton abundance is estimated by measuring the concentration of chlorophyll-a,
the principal pigment of photosynthesis. In November 2003, aboard the R/V Savannah,
water samples were collected with Niskin bottles from multiple depths at 17
stations along a transect line crossing the continental shelf. Water was filtered
on board onto glass fiber filters and frozen in liquid nitrogen. Following the
cruise, chlorophyll-a concentrations were measured using a fluorometer. This
hypothesis is also tested by analyzing vertical profiles of temperature and
salinity in shelf waters.
POSTER
Interannual Marine Phytoplankton Community Dynamics in Continental Shelf Waters off Charleston, South Carolina
-Morgan Cawley, Leg 05
Rarely do offshore phytoplankton surveys return to the same geographic locations at the same time of year to observe interannual changes in community structure and correlate these changes to differences in oceanographic environmental variables. This study offers an interannual comparison of continental shelf phytoplankton species composition and distribution in the fall of 2004 and 2009. Undergraduate students from the College of Charleston Transect Program collected data aboard the R/V Savannah. Oceanographic data were recorded along 2 parallel transect lines stemming from nearshore waters off Charleston, SC to the western edge of the Gulf Stream. Phytoplankton samples were collected using a 20 µm phytoplankton net towed on the surface for 3 minutes. Samples were identified using Scanning Electron Microscopy at the National Oceanic and Atmospheric Administration’s Center for Coastal Environmental Health & Biomolecular Research at Charleston (NOAA - CCEHBR). Cell counts were made using light microscopy to calculate relative abundance of different phytoplankton species and ratio of diatoms to dinoflagellates. Interannual differences in the diversity and abundance of phytoplankton communities will be described and interpreted in accordance to recorded surface water environmental parameters. The abundance and distribution of the Domoic acid producing diatom species, Pseudo-nitzschia, will be highlighted because of the potential role of this harmful algae in the mortality of marine mammals.
POSTER
Spatial Distribution and Characterization
of Communities of Organisms Associated with Sargassum spp. Algae in Autumn.
-Meghan Chafee, Leg 01
Sargassum spp. is a floating brown macroalgae (Division Phaeophyta) that generally
forms clumps or large mats on the ocean surface providing spawning, nursing,
feeding grounds, and refuge with a high structural complexity for a variety
of marine organisms. Distribution and abundance data of Sargassum spp. and neustonic
organisms were collected from neuston net tows across the continental shelf
off the coast of Charleston (South Carolina) in November 2003. The spatial distribution
of Sargassum spp. and associated species will be analyzed along the shelf transect.
Use of Sargassum spp. as a spawning substrate will be tested by correlating
abundances of algal clumps with adult Halobates spp. insects, which employ floating
Sargassum spp. as a substrate for egg laying. Zooplankton biomass will be used
as an indicator of the amount of food available for fishes associated with Sargassum
spp., in an attempt to determine if algal clumps are used by fishes for feeding
or as refuge.
Autumn phytoplankton species composition
and distribution across the continental shelf from the coast of Charleston,
South Carolina, to the Gulf Stream
-Elizabeth Symon, Leg 03
In November of 2004, College of Charleston students embarked on a five day oceanographic
research cruise aboard the R/V Savannah along two parallel transect lines across
the continental shelf off the shore of Charleston, S.C. to the Gulf Stream.
Few studies have been done on phytoplankton off the southeast coast of the U.S.
Phytoplankton samples were collected using a CTD. Samples were filtered and
analyzed using SEM while cell counts were done using light microscopy. A ratio
of diatoms (class Bacillariophyceae) to dinoflagellates (class Dynophyceae)
was determined. Diatoms and dinoflagellates were classified into genus and specie
level when possible to determine percent specie composition at each site sampled.
Diversity was measured using the Shannon-Weaver Diversity Index and analyzed
to see if a correlation existed between diversity and distance from shore. Surface
maps of chlorophyll concentration, temperature, and salinity were analyzed to
hypothesize what may have affected phytoplankton species composition and distribution.
POSTER
The Generic Distribution of Benthic
Foraminifera along the Charleston Transect of the Continental Shelf off Charleston
South Carolina
-Nicole Abdul, Leg 02
Knowledge of the distribution of benthic foraminifera can provide scientists
with valuable insight into reconstructing paleo-environments, paleo-bathymetry
and paleo-climates. Information dating back to the Cambrian lays hidden beneath
modern day oceans, trapped in the Calcium Carbonate test of these sand-sized
protists. Although in excess of 700 studies have been conducted on the distribution
of benthic forams around North America (Culver 1980) very few address their
distribution along the eastern continental shelf. Eight sediment grab samples,
collected along the Charleston Transect of the continental shelf’s inner,
middle and outer shelf, in waters 11 to 96 meters were analyzed for Benthic
foraminifera distribution. Preliminary results suggests the dominance of one
main genus namely Quinqueloculina; however, as one moves from the inner to outer
continental shelf, a distinct shift from Milliolid- to Rotalaria-dominated facies
becomes evident. Although this pattern of distribution aligns well with previously
documented patterns along the Southern coast of Florida and into the Gulf of
Mexico, further study is required to continue the mapping of the distribution
of Benthic foraminiferal assemblages along the eastern continental shelf.
Temporal and Spatial Variability
in Benthic Foraminifera Fossil Assemblages off the Continental Shelf,
Charleston, SC
-Nicole Abdul (Leg 02), Dr. Leslie Sautter, Sam
Crickenberger (Leg 04), Christina Skalit (Leg 04)
Benthic foraminifera are morphologically diverse Protists found in habitats
ranging from the shallow inter-tidal zones of marshes and bays to the depths
of the open oceans. Although globally distributed, foraminifera genera are environmentally
specific and therefore knowledge of their modern day distribution can provide
valuable insight into reconstructing paleo-bathymetry, paleo-stratigraphy, and
ultimately paleo-climatology. Very few studies address foram distributions along
the southeastern North American continental shelf. Over a two year period, four
cruises were conducted as part of the Transect Program, along the Charleston
Transect of South Carolina’s continental shelf. Sediment grab sample collections
were conducted on each cruise at the same eight stations, in waters with depths
ranging from 11 to 96 m. Between 25 and 39 benthic foraminifera genera were
identified for a single cruise, with an average of 8 “dominant”
genera (> 5 % of the foram genera at any station). Dominant genera consistently
included Quinqueloculina, Textularia, Hanzawaia, Cibicides, Triloculina, Bigenerina,
Bolivina, Eponoides, Amphistegina and Elphidium. Additionally, genera were grouped
by test texture: Miliolid (porcelain tests), Agglutinate (tests composed of
cemented grains), and Hyaline (glassy tests). For each cruise collection, considerable
cross-shelf assemblage variability existed. However, significant temporal variability
was also observed at many of the sampling stations for the four cruise collections.
Although similar foraminifera genera were identified from samples collected
on each cruise, the spatial distribution of dominant genera and textural groups
showed a high degree of temporal variability. To some degree the distribution
of foraminifera along the Charleston Transect compliments previously established
and documented patterns along the Southern coast of Florida and into the Gulf
of Mexico. Further studies are required to conclusively map the distribution
patterns of benthic foraminiferal assemblages along North America's southeastern
continental shelf. We will report on comparisons of foram assemblage variations
and distribution with respect to ongoing grain size analyses and video data
collected with a remotely operated vehicle.
Benthic Foraminiferal Population Distribution off
the coast of Charleston, SC, November 2003
-Daniel Boles, Leg 01
In the Fall of 2003, students from the College of Charleston sailed aboard the
research vessel SAVANNAH along a southwest trending transect from south of the
Charleston harbor to the continental shelf edge. Samples were collected along
the transect using a Smith-MacIntyre grab apparatus, and preserved in a 4% formalin/seawater
solution with rose bengal dye added to stain living organisms. Sediment collected
by the grab apparatus will be analyzed and described using standard analytical
techniques, and living foraminifera will be counted and classified. These data
will be used to show the relationship between living populations of benthic
foraminifera and the grain size distribution of their respective habitat locations.
This information will serve as a reference to subsequent College of Charleston
Transects cruises, and future Transects students will be able to compare data
to show seasonal and inter-annual changes in foraminiferal populations.
POSTER
Comparison of Benthic Foraminifera Between Two Cross-Shelf Transects off Charleston, SC
-Vikki Bernotski, Leg 05
During the Transect Program in November 2009, fourteen sediment samples were collected using a Shipek Grab Sampler along two South Carolina cross-shelf transects: the Primary Transect off Folly Beach and the Capers Transect off Capers Island. A 120 mL homogenized sub-sample was taken from each grab sample for the purpose of studying benthic foraminifera. Foraminifera specimens were picked from the > 500 mm size fraction and identified to the genus level. The most common foraminifera genera, >10% of total abundance, were compared between the two transects for the inner, middle, and outer continental shelf regions. All genera found are present in both transects, showing equal diversity. The major genera vary across the shelf and are similar between the two transects at the outer shelf, but vary greatly for the inner and mid-shelf regions.
POSTER
Spatial Distribution of Benthic
Foraminifera Across the Continental Shelf off the Coast of Charleston, South
Carolina
-Sam Crickenberger, Leg 04
Benthic foraminifera fossil test assemblages can serve as proxies for paleoecological
and paleooceanographic conditions. Sediments in the Gulf of Mexico, as well
as along the Charleston Transect, are most accurately dated to the early Pleistocene,
providing an environmental record during that time period. Thirteen grab samples
were collected along the Charleston Transect, ranging in depth from 9.9 to 100.4
m, and were analyzed for benthic foraminifera distributions. General dominance
distributions were found similar to that of Poag (1981) in the Gulf of Mexico
with the exception of Textularia, Eponides, and Elphidium. Textularia was dominant
at the hard grounds of the outer shelf with Eponides and Elphidium having somewhat
of a role reversal in their depth related distributions.
POSTER
Vertical Depth Habitats and Geographic
Distribution of Living Benthic Foraminifera within the Continental Shelf Sediments
off Charleston SC, November 2003
-C. Travis Debnam, Leg 01
Benthic foraminifera are generally known to occupy species-specific habitats
within the surface and near-surface ocean bottom sediments. Few studies on living
benthic foraminifera populations within the shelf sediments off Charleston SC
have been conducted, as a result the geographic distribution and vertical depth
habitats in this region are poorly understood. Seven push-core samples were
taken across the continental shelf off Charleston SC, during November of 2003,
while onboard the R/V Savannah during Leg 01 of the College of Charleston’s
Transects Program. Populations of living benthic foraminifera identified were
sampled and compared in 2 cm interval slices, from four of seven cores, to a
depth of 10 cm. Data indicates variations in species populations vertically
down-core, as well as with water depth across the continental shelf along the
Transects line. This study will supplement any further research conducted through
the College of Charleston’s Transects Program.
POSTER
Benthic Foraminifera Distribution
across the Continental Shelf off Charleston, South Carolina
-Ross Martin, Leg 03
In November 2003 (Transect Program, Leg 01) 8 sediment stations were sampled from
the inner shelf to the shelf edge, off the coast of Charleston, SC, from aboard
the R/V Savannah. Benthic foraminifera were extracted from sediment to study their
distribution and abundance which had only been documented by previous Transect
research (Abdul, 2004). Specimens were identified to the genus level, and relative
abundances (%) were calculated. Twenty-seven genera were identified, 9 of which
accounted for more than five percent at one or more stations. Hanzawaia was the
dominant genus at 7 of the 8 stations, whereas Textularia was dominant at the
outer shelf station. Cibicidoides was the second most abundant genus at all but
station #7, located on the mid-shelf. These data differ from previous unpublished
studies, despite replication of methodology. Further studies are very necessary
to determine the dominant genera year round.
POSTER
Cross-Shelf Benthic Foraminifera Distribution off the Charleston, SC Coast
-Emily Osborne, Leg 05
Benthic foraminifera are single celled, calcium carbonate Protists found in all marine environments. These chambered organisms have proven to be invaluable proxies for reconstructing paleo-environments. The College of Charleston Transect Program has conducted five oceanographic research cruises off the Charleston coast along cross-shelf transect lines. Using a Shipek Grab Sampler, sediment samples were collected in November 2009, and foraminifera (125-500 µm) were extracted from each sample and identified to the genus level. Foraminifera were also classified by test texture, showing an overall dominance of Rotalids. Twenty genera were found across the continental shelf, seven of which were dominant. The genus Cibicidoides (a Rotalid) dominates across Charleston’s entire continental shelf. This distribution differs from Wylie Poag’s Generic Predominance Facies off the West Florida shelf, possibly the result of low bottom water temperature variance off Charleston, due to the influence of the Gulf Stream at the shelf edge.
POSTER PhotoDocumentary
Distribution and Variance of Modern
Benthic Foraminifera Assemblages Found off Charleston, S.C., Across the Continental
Shelf.
-Elizabeth Rogers, Leg 01
Participation in the College of Charleston’s Transects Program
provided an opportunity to obtain seven surface sediment grab samples across
the continental shelf off Charleston, S.C. in November 2003. Water depths along
this main transect ranged from 10 m to 100 m. Sediments collected aboard the
R/V Savannah were dried, sieved, split, and examined to identify modern benthic
foraminifera to the genus level. While the predominant genera changed as the
water depth increased, two genera of benthic foraminifera dominated –
Quinqueloculina and Cibicides. While these genera were found in every sample,
it appears that they prefer different habitats, perhaps dependent upon sediment
influx into the system. Excluding these genera, the overall distribution of
many other genera is widespread but only in low to medium abundances.
POSTER
Benthic Foraminifera of the Continental
Shelf off Charleston, SC
-Christina Skalit, Leg 04
Benthic foraminifera were picked from surface sediments collected across the
continental shelf off Charleston, SC, along the Charleston Transect. Relative
abundances of genera -- defined as any genus greater than 5% in one or more
sample -- were calculated, and the distributions of Generic Predominance Facies
were mapped. The inner shelf (0-20m water depth) was dominated by Quinqueloculina,
and the mid-shelf (20-50m), was dominated by Cibicides and Quinqueloculina.
The outer shelf (50-100m), which is strongly influenced by the Gulf Stream,
was dominated by Cibicides and Hanzawaia; however, one station
located near a rocky outcrop (50m) was dominated by Textularia. These
strong variations in predominance of foraminifera genera are due to (1) depth
variations across the shelf; (2) proximity to the Gulf Stream; and (3) substrate
differences. Substrates range from coarse sand mega-ripples, to hardground areas
surrounded by sediment, to incised ancient river channels.
POSTER
Temporal and Spatial Variability
in Benthic Foraminifera Fossil Assemblages off the Continental Shelf, Charleston,
SC
-Skalit, Christina, Sautter, Leslie, Abdul, Nicole,
Crickenberger, Sam, and White, Ransom
As part of the College of Charleston's Transect Program, four research cruises
were conducted over a two-year period, sampling across the South Carolina continental
shelf adjacent to Charleston. Sediment grab sample collections were conducted
on each cruise at the same eight cross-shelf stations, in waters with depths
ranging from 10 to 100 m. Between 25 and 39 benthic foraminifera genera (>125
micron size fraction) were identified for a single cruise, with more than 10
“dominant” genera (> 5 % of the genera at any station), including
Quinqueloculina, Textularia, Hanzawaia, Cibicides, Triloculina, Bigenerina,
Bolivina, Eponoides, Amphistegina, and Elphidium. The distribution of foraminifera
along the Charleston Transect only partially compliments previously documented
patterns along the southeast shelf and the Gulf of Mexico. For each cruise collection,
considerable cross-shelf assemblage and dominant genera variability existed.
Although similar foraminifera were identified from samples collected on each
cruise, the spatial distribution of dominant genera showed a high degree of
temporal variability for the four cruise collections. Sediments in the study
region consist of a thin veneer of modern and relict sands, underlain by limestone
hardground. Video of the seafloor collected with a remotely operated vehicle
shows evidence of migrating sand megaripples which may be responsible for the
seasonal reworking and redistribution of sediments. Sediment characteristics
within the megaripples vary with respect to grain size and composition, and
may be influencing the foraminiferal assemblage composition. Comparisons will
be presented on foraminiferal assemblage variations and distribution with respect
to grain size analyses and video data collected with a remotely operated vehicle.
GSA Abstracts with Programs, 2006, Vol. 38, No. 7.
Distribution and Diel Vertical Migration of Zooplankton in the South Atlantic Bight
-Leianna Arnold , Leg 05
The vertical and horizontal distributions of zooplankton over the South Atlantic Bight were analyzed and correlated with chlorophyll distributions. Zooplankton samples were taken with a Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) and a Neuston net in November of 2009 in continental shelf waters off Charleston, SC along two transect lines perpendicular to the coastline. The abundance and diversity of different zooplankton taxa were analyzed from preserved samples using a compound scope in order to describe distributional patterns in relationship to oceanographic variables. To characterize possible diel vertical migration (DVM) behavior patterns within the zooplankton community, MOCNESS tows were taken at discrete depths during day and night times and compared. Total zooplankton biomass was higher closer to shore, suggesting a positive correlation between zooplankton and phytoplankton densities. Also zooplankton biomass in surface waters was higher during night tows than day tows suggesting diel vertical migrations.
POSTER
Zooplankton in the South Atlantic
Bight: Characterization of dispersion and
environment through biovolume correlations
-John R. Casey, Leg 04
Neuston net tows were made during both the day and night across the continental
shelf off Charleston, SC during June 2004. Zooplankton biomass estimates were
used to describe zooplankton distribution patterns; they were also correlated
to a suite of environmental and biological factors to determine their influence
in explaining these distributions. Potential biological proxies analyzed included
surface chlorophyll a concentrations and the presence of floating Sargassum
spp. clumps, a planktonic macroalgae which provides a unique habitat for fish,
marine insects, and other natural predators of zooplankton. Sargassum is also
a convenient biomarker for convergent surface currents. Our findings show that
total zooplankton biomass at the surface were more than twice as high in samples
containing significant (>170mL) amounts of Sargassum. Biomass was also nearly
doubled during nighttime tows due to DVM. No direct correlations were observed
between biomass and salinity, SST and, interestingly, chlorophyll.
Distribution of the Hyperiid
Amphipod, Lestrigonus bengalensis, across the Continental Shelf off South Carolina,
USA: Does Diel Vertical Migration Play an Important Role?
-David Couillard, Leg 01
The processes that regulate the distribution and migration of zooplankton have
been studied for more than a century. The interaction of biotic (e.g., competitors,
predators, and food) and abiotic (e.g., temperature, currents, and light) factors
likely lead to the adoption of behaviors that attempt to optimize temporal and
spatial resource use concomitant with predator avoidance. To examine diurnal
and nocturnal distributions of the abundant Hyperiid amphipod, Lestrigonus bengalensis,
plankton net samples were taken from the R/V Savannah between November 19-23,
2003 across the continental shelf off the coast of Charleston, South Carolina.
Oblique tows of a bongo net were employed to sample the top 50 meters of the
water column, while a neuston net captured only organisms in the surface layer
(0.5 meters). Comparisons of diurnal and nocturnal abundances of L. bengalensis
found in samples caught with bongo and neuston nets are used as a measure of
the presence or absence of diel vertical migration.
PhotoDocumentary
Seasonal Comparison of Distribution
of the Hyperiid Amphipod, Lestrigonus bengalensis, across the Continental Shelf
off South Carolina
Wes Dukes, Leg 02
The Hyperiid amphipod, Lestrigonus bengalensis, is among the most abundant
amphipod found off the coast of South Carolina. Lestrigonus bengalensis is thought
to perform diel vertical migration however very few studies have been conducted
to show this. Results from two cruises, fall and spring, indicate that diel
vertical migration is performed by Lestrigonus bengalensis. Data from both cruises
was compared in order to begin studying the seasonal distribution patterns of
Lestrigonus bengalensis off the coast of Charleston, South Carolina.
Title of Paper: Compositional
Differences in Fall Zooplankton Communities across the Continental Shelf off
Charleston, S.C.
-Jennifer Fountain, Leg 01
Zooplankton communities were sampled across the continental shelf off
Charleston, South Carolina from the oceanographic R/V Savannah in November 2003.
Shallow water (0-50 m) plankton samples were taken at night using a 505 µm
mesh- bongo net along a main transect that lay perpendicular to the coastline.
Sample biomass was measured employing a volumetric displacement method, and
organism diversity was estimated through the identification and quantification
of zooplankton samples using dissecting scopes. Spatial differences in coastal
phytoplankton primary productivity are hypothesized to directly affect zooplanktonic
communities. Phytoplankton concentrations frequently decrease with distance
from the shore, due to nutrient influx from coastal rivers. Therefore, zooplankton
biomass is expected to diminish with distance from the coastline, and be positively
correlated to chlorophyll-a concentrations. Zooplankton composition is predicted
to vary across the continental shelf, reflecting differences in the amount of
benthic organisms’ larvae (meroplankton) due to increasing depth. The
ratio of pelagic zooplankton (holoplankton) to meroplankton abundance is projected
to increase along the continental shelf, with maximum values achieved in the
Gulf Stream sample.
POSTER PhotoDocumentary
Abundance of Chaetognaths (Arrow
Worms) across the Continental Shelf off Charleston, South Carolina
-Brooke Pehr, Leg 02
Abundance of chaetognaths was calculated at 7 stations in the South
Atlantic Bight off Charleston, SC between May 18 and May 22, 2004. Zooplankton
samples were obtained from bongo net night tows. Physical characteristics of
the water, as well as zooplankton biomass estimates were considered when determining
reasons for abundance or lack of abundance. Chaetognaths were present at every
station, however more abundant at some stations than others. A positive correlation
was found between chaetognath abundance and total zooplankton biomass estimates,
which we attribute to the fact that chaetognaths prey on other zooplankton,
especially copepods. We did not find a correlation between abundance and distance
from shore, although a significantly lower abundance was calculated at the station
closest to shore. Chaetognaths are found in a variety of temperatures and salinity.
While we found the highest abundance of chaetognaths at the station with the
coldest average water column temperature and one of the highest salinity averages,
we did not find a correlation between temperature, salinity, and chaetognath
abundance as a whole. We conclude that chaetognath abundance does vary across
the shelf and is most closely related to abundance of other zooplankton.
PhotoDocumentary
Ichthyoplankton densities and distribution
across the continental shelf off Charleston, South Carolina.
-Michelle Bahm, Leg 03
On November 19-23, 2004, the Transects program collected larval fish from a
transect line extending from the coast of Charleston, SC. Larval fish were collected
with a bongo net with a mesh size of 505 µm. The fish were later quantified
and identified to determine abundance and distribution of several species across
the continental shelf. These data were compared to those collected in 2003 by
the Transects program, and in 1973 by MARMAP. Results showed that fish are more
abundant on the middle shelf, and more fish per cubic meter were obtained in
2003 than in 1973 or 2004. Pleuronectiformes and Leptocephalus larvae were the
most abundant species observed per cubic meter of water, with Clupeiformes and
the genus Ophidiidae being the next abundant.
POSTER
Spring Distribution and Abundance
of Ichthyoplankton across the Continental Shelf
-Sherena H. Coachman, Leg 02
To study the abundance and distribution across the continental shelf samples
were collected during a 5-day research cruise along the Charleston Transect
off the coast of Charleston, SC. The time of the cruise was from May 18th-22nd.
Nine samples were collected during day and night and analysized. Larval fish
were categorized into the orders of Pleuronectiforms, Clupeiforms, and Scombriforms.
Those not identified were placed in the other category. Clupeiforms were one
of the dominant percentages found during both the fall and spring. The distribution
and abundance may have been affected by the Gulf Stream. Another factor affecting
abundance is that it was not spawning season for some the larval fish used for
this study.
Fall Icthyoplankton Abundance
Across the Continental Shelf Off Charleston, South Carolina
-Marilyn B. Laserna, Leg 01
The ichthyoplankton communities of the South Atlantic Bight were characterized
in detail during the 1970s, as part of the Marine Resources Assessment and Prediction
program (MARMAP). Ichthyoplankton communities inhabiting the shallow shelf waters
were sampled in the fall of 2003 from the RV Savannah with both Bongo and Boothbay
neuston net samplers. Only nocturnal tows were analyzed for this study. The
nets were equipped with flow meters in order to estimate the volume of water
filtered. Larval fishes were removed from the plankton samples, and the Clupeiform,
Pleuronectiform and Elopomorpha (leptocephalus) larvae were identified and quantified.
In order to analyze the possible historical changes in the ichthyoplankton communities
of the shelf, the present overall abundance, composition and distribution of
the larval fishes will be compared with the historical ichthyoplankton data
collected in the fall of 1973 as part of the MARMAP program. This study attempts
to describe historical changes in ichthyoplankton communities 30 years after
the original study and focuses primarily on the orders Pleuronectiform (flatfishes),
Clupeiform (sardines and their allies) and the super order Elopomorpha (eels
and their allies). Similar abundance, relative abundance and occurrence values
were found when compared to MARMAP cruise D5-73. Variations may be attributed
to the fact that the MARMAP studies covered a larger sampling area and included
both nocturnal and daylight samples.
POSTER
Diel Differences in Ichthyoplankton
Communities Collected with a Bongo Net: Gear Avoidance or Diel Vertical Migration?
-Brad Schondelmeier, Leg 01
Differences in ichthyoplankton abundance collected with plankton nets in varying
light levels have been described in a multitude of studies, including the Marine
Resources Monitoring Assessment and Prediction (MARMAP) plankton surveys off
the coast of South Carolina in the mid 1970’s. In November 2003, oblique
shallow water tows (0-50 m) were performed with a 505 micrometer bongo net at
each of 17 different stations along a main transect line perpendicular to the
South Carolina coast, south of Charleston. Surface icthyplankton samples (top
50 cm) were collected at the same stations with a 1000 micrometer neuston net.
All samples were preserved in 95% ethanol and later examined in order to quantify
and identify planktonic fishes. It has been documented that young larval fishes
tend to perform diel vertical migrations (DVM), swimming to deeper waters during
daytime, primarily to avoid predators. But certain fishes with advanced swimming
abilities have also been documented to avoid nets, mainly during daytime hours,
due to increased visual detection of sampling gears. By comparing day and night
samples, plus simultaneous bongo and neuston tows, we will attempt to determine
what causes the differences in icthyoplankton composition: diel vertical migrations
or visual net avoidance.
POSTER PhotoDocumentary
Seasonal Ichthyoplankton Distribution
Across the Continental Shelf
Off Charleston, SC
-Ryan Yaden, Leg 03
In order to compare the seasonal and spatial distribution of across the continental
shelf off the coast of Charleston. The collection plankton samples took place
on a 5 day cruise starting on November 19 and continuing to the 23, 2004. Seven
samples were analyzed by removing the ichthyoplankton from the other zooplankton.
Then those ichthyoplankton were identified into Leptocephalus, Scombridae, Ophidiidae,
Pleurinectiformes, and Syngnathidae. The larval fishes that could not be classified
were put into the “unknown” category. When comparing the abundance
form May to November it was found that the abundance of larval fish in November
is greater than the abundance in May. When comparing this to the coast of Georgia
the fish abundance was greater in the spring than in the fall. The greater abundance
in fall 2004 could be that the temperatures for the fall were higher then average
possibility giving the fishes a longer spawning season.
POSTER
Distribution of Benthic Meiofauna
across the Continental Shelf off the Coast of Charleston, SC
-Chris Giguere, Leg 02
This paper is primarily a characterization of the benthic meiofauna
found across the continental shelf off the coast of Charleston, SC. Actual abundances
of organisms are evaluated at 8 stations along a transect perpendicular to the
coast. These abundances are compared to grain size found at each station, and
a correlation is evaluated. Taxonomic richness is calculated for each station
using a modified Shannon-Weaver Index. Taxonomic richness is then compared to
grain size at each station, and a correlation is evaluated. Other similar studies
are mentioned and compared to this study.
POSTER
Seasonal Comparison of Echinodermata
across the continental shelf off Charleston, South Carolina
-Lauren Halloran, Leg 03
Echinoderm specimens were collected in November 2004 and May 2005 across the
continental shelf off Charleston, SC aboard the R/V Savannah. Specimens were
identified to the species level and separated into three taxonomic groups: asteroids,
ophiuroids, and echinoids. Species density per 1000 m2 for all organisms collected
was determined along with a seasonal comparison and overall spatial distribution
of key species. Greater than 10 specimens of a species per 1000 m2, collected
in November or May, defined the key species. Overall, more echinoderms were
collected in May than in November. Asteroids were found in greater numbers in
May compared to November and were more numerous in the mid-shelf during May
and November. Similarly, more ophiuroids were collected in May, however, one
key species was dominant across the shelf in both seasons. Seasonal variations
and a change in dominance of echinoids were observed across the shelf.
POSTER
The Effects of Depth and Primary
Sediment Composition on the Distribution of Echinoderms across the Continental
Shelf of Charleston, S.C.
-Cecilia Lewis, Leg 02
Echinoderms have been described as one of the most abundant groups of invertebrates
in marine environments. The objectives of this study were to: 1) determine whether
depth solely dictated the distribution of echinoderms (i.e. echinoids and asteroids)
with increasing depth or 2) whether the primary sediment component occurring
at each station determined echinoderm distribution across the continental shelf.
Sampling for this project took place in spring 2004 from May 18 to 22nd onboard
the R/V Savannah. Samples were collected along a transect line extending across
the continental shelf from the southern most end of Folly Island, South Carolina.
A dredge trawl was employed for benthic macrofaunal sampling and a Smith-Macintyre
Grab Sampler was employed to for sediment sampling. Total counts and calculated
percentages of echinoderms captured at inner shelf stations indicate that members
of class echinoidea dominated the inner shelf as well as the outer shelf benthos.
Distribution of benthic meiofauna
crustaceans across the Continental shelf off Charleston, SC.
-Alison M. Cawood, Leg 03
Benthic meiofaunal communities can vary tremendously, depending on a variety
of factors such as sediment type, mean grain size, water depth, and temperature.
There has been little work done on the benthic meiofaunal crustaceans of the
South Atlantic Bight, and no work has been done on the groups of crustaceans
that inhabit the continental shelf of this area. A Smith-McIntyre grab sampler
was used to collect sediments along two parallel cross-shelf transects off Charleston,
SC in November 2004. Ten groups of crustaceans were found, representing fourteen
families. No correlation was observed between the abundance of crustaceans and
abiotic factors, such as depth, temperature, salinity, or mean grain size. Perhaps
the crustacean abundance is being controlled by other factors such the type
of environment (e.g., live bottom) or other environmental factors (e.g., nutrient
availability and/or predator abundance).
POSTER
Abundance, diversity and distribution
of micro Gastropoda across the continental shelf, off Charleston, SC.
-Thomas P. Smith, Leg 04
The depth ranges and factors affecting the micro Gastropoda off the southeast
United States are poorly known. Sediment samples were collected aboard the R/V
Savannah with a Smith-MacIntyre grab sampler and Gastropoda were removed and
identified. The relative abundance, absolute abundance and species density were
compared to depth data, sediment composition data and sediment mean grain size.
The results showed that micro gastropods became more abundant and had higher
species density with a decrease in mean grain size. This may be a result of
mobility factors, predation effects and food source limits in small gastropods.
Sediment that had a higher composition of biogenic sediment increased the species
density but not the absolute abundance of micro gastropods. Higher amounts of
biogenic sediment usually reflect higher diversity of organisms and higher carrying
capacity of an ecosystem. Depth did not affect either absolute abundance or
species density.
Distribution,
abundance, and diversity of micro-gastropods across the continental shelf off
Charleston, South Carolina, with consideration to sediment analyses.
-Thomas P. Smith (Leg 04), Post-Transects independent study
Surface sediments from 3 different Transect Program research cruises were collected
across the continental shelf off Charleston, SC. The Charleston Transect ranged
from nearshore waters to the shelf edge where water depths were 100 m. Different
depth zones and cross-shelf geographic ranges were identified using these micro-gastropod
assemblages. Four different micro-gastropod sediment facies can be identified
by the abundance of two to three species found at each site within the inner
shelf (0-20m water depth), mid-shelf (20-50m), outer shelf and shelf edge (50-100m).
No seasonal variability was observed, despite the variations in sediment grain
size analyses (White, 2006), indicating a well-homogenized fossil assemblage.
POSTER
Relationship of Coarse-Grained Sediment Distribution and Composition
with Echinoderm Species’ Habitat Preferences
-Delynn Woodman, Leg 05
Characterizing the habitat of benthic echinoderm species requires a close examination of sediments on the ocean floor. Using sediment grab sampling devices, sediments were collected by the College of Charleston’s Transect Program from seven stations across the continental shelf off Folly Island, SC in November 2004, May 2005 and November 2009. Collection stations ranged in depth from 17 to 120 m. Grain size distributions were determined using dry sieving analysis, and the larger grain size fractions of gravel (>2.00 mm) and very coarse sand (1.00 to 2.00 mm) were examined for composition focusing on the biogenic component. Echinoderm fragments were counted and included in the percent biogenic. Using a beam trawl, echinoderm specimens were collected at the same sediment sample locations in November 2009 and compared with spatial distribution and abundance of echinoderms previously studied for the November 2004 and May 2005 cruises. Sediment characteristics showed consistent trends on the self edge for all three sampling years but the majority of the shelf showed little consistency. Echinoderm abundance was highest in May 2005 and lowest in November 2009. Based on results, the distribution and abundance of various echinoderm species have no strong, probable correlation with any sediment characteristics or depth across the continental shelf.
POSTER
Abundance, Distribution and Diversity
of Benthic Fishes from the Continental Shelf off Charleston, South Carolina
-Dana B. Hughlett, Leg 03
We studied the special distribution, relative abundance and biodiversity across
the Continental Shelf off Charleston, South Carolina. Using a 1 m beam trawl,
we sampled eleven sites across the shelf, fixing and preserving representative
samples in 10% formaldehyde and 95% Ethanol, respectively. Each segment into
which the shelf was divided (Inner, Middle and Outer) was found to be dominated
by a different species. The Inner Shelf had the highest relative abundance of
Citharichthys sp., while the Middle shelf was dominated by Otophidium omostigmum
and the Outer shelf was characterized by Otophidium dormitator and Urophycis
regia. We found that biodiversity decreases with increasing distance from shore.
A total of thirty-three species were identified across the entire shelf, with
varying number of species at each shelf segment.
POSTER
Seasonal abundance and size distribution
of benthic fishes across the continental shelf off Charleston, South Carolina
-Lester Proctor, Leg 04
Seasonal changes in relative abundance and size distribution of demersal fishes
were examined from samples collected across the continental shelf off Charleston,
SC, in May 2005 and November 2004. Fifteen sites were sampled with a 1 meter
beam trawl, catching fifty four different fish species. Each physiographic region
of the continental shelf (Inner, Middle and Outer Shelf) was dominated by a
different fish species. The Inner and Middle shelf had the highest relative
abundance of Etropus cyclosquamus (Shelf Flounder), while the Outer shelf was
dominated by Synodus foetens (Inshore Lizardfish). Demersal fish abundances
variedbetween seasons however; patterns were observed suggesting possible migration
and recruitment events. Size analysis of E. cyclosquamus and Prionotus carolinus
showed an increased abundance but lower average size, suggesting a recruitment
event occurred between seasons. The other species analyzed for seasonal size
differences were Symphurus minor, Serrinaculus pumilio, and S. foetens, all
observedhad increased abundance and size.
Etropus
cyclosquamus and Symphurus minor: a closer look
at two South Atlantic Bight flatfishes
-Dana Hughlett and Lester Proctor, Legs 03 and 04
As part of the Transects project, in the Spring of 2005, we
sampled small sized demersal fishes at seven sites across the Continental Shelf
using a 1 m beam trawl. Symphurus minor (Largescale tonguefish) was found at
all depths along the continental shelf, and the maximum recorded depth of 100
meters was 40 meters deeper than currently documented for this species. Both
males and females were caught at the same depths, indicating a mixed sex adult
habitat, although females were found to dominate the sex ratio. The only site
where a juvenile was caught was located at the nearest site to shore, no mature
individuals were sampled, possibly indicating its value as a recruitment site.
Large captures of juvenile Etropus cyclosquamus (Shelf flounder) indicate possible
recruitment events during winter months in near shore waters. We also conducted
preliminary age-size analysis of juveniles E. cyclosquamus.
Habitat and spatial distribution of
benthic fishes along the Continental shelf off Charleston, South Carolina
-Benjamin Stone, Leg 04
In May of 2005, the Transects program (LEG 04) collected benthic samples along
a transect line across the continental shelf off the coast of Charleston, South
Carolina. Samples were collected using a beam trawl with a 1.0 meter wide opening
in order to describe shelf communities of small demersal fishes. A total of 41
different species of fish were caught. Fish density and diversity were compared
with depth, sediment type, and presence of live bottom. Fish distribution patterns
seemed to be species specific, and were commonly correlated with depth and/or
the presence of live bottom. The presence of live bottom was positively correlated
with biodiversity, with the outer shelf having the highest diversity compared
to the inner and mid-shelf zones.
Sediment grain size and composition
An Analysis of Microfossil Assemblages
Across the Continental Shelf off the Coast of Charleston, SC
-Adriane Cushman, Leg 03
Sediment samples were collected in November 2004 on the continental shelf off
the coast of Charleston, SC aboard the R/V Savannah. Seven samples were dried
and split, then grains were counted and identified as biogenic or non-biogenic
sediment. The percent of biogenics present was calculated, and biogenics were
divided into microfossil taxa. Results show that the inner-, middle-, and outer-shelf
samples consistently contain less than 10 % biogenic sediment, most of which
is fragments of bivalves and other hard part remains of organisms. In contrast,
the shelf-edge station, which is influenced by the Gulf Stream and far from
the source of lithogenic material, consists of nearly 70 % biogenic sediment.
Planktonic and benthic foraminifera, echinoderm and coral fragments are present
along with numerous bivalve shell fragments.
POSTER
Sediment Analysis and Mineral Composition across the South Carolina Continental Margin
-Cody Donofrio, Leg 05
Leg 05 of College of Charleston’s Transect Program was conducted in November 2009, during which sediment samples were collected across the continental shelf off Charleston, South Carolina. Sediments were collected using a Shipek Grab Sampler at 14 locations along two transect lines, one extending from Folly Island and the other from Capers Island. Using a particle size analyzer, grain size distributions were determined along two cross-shelf transects. A Scanning Electron Microscope and binocular microscope were used to determine mineral composition contained in coarse material at the 0.5 mm size fraction. Grain size distributions and mineral composition will be related to distance from shore and proximity to the Gulf Stream. Results indicate that the sediments collected do not follow the traditional model of sediment distributions along the continental shelf.
POSTER
Changes in Cross-Shelf Sand Size Distribution Off the Coast of Charleston, SC from 2003 to 2009.
-Veronica Holton, Leg 05
Temporal changes in cross-shelf sand size distribution have been studied by undergraduate students from the College of Charleston Transect Program using sediment samples collected at seven stations during three research cruises from November 2003 to November 2009. Variations in grain size demonstrate changes in wave energy, currents, and tides affecting how deposition occurs. In 2009, samples were collected along a cross-shelf transect off Folly Island, SC using a Shipek grab sampler. Ro-Tap sieve and statistical analyses were conducted, and compared to results from two previous cruises on sediment samples collected at the same stations to demonstrate temporal changes in cross-shelf grain size distribution. The mid-shelf has a higher level of variability, whereas the most of the inner and outer shelves remained constant. Variability may be due to a station’s close proximity to rocky hard ground areas.
POSTER
Surface Sediment Composition and Grain Size Distribution
on the Continental Shelf off Charleston, SC.
-Glen Landon, Leg 01
Surface sediments of the continental shelf adjacent to Charleston, SC were sampled
between November 19 and 23, 2003. The area sampled, referred to as the Charleston
Transect, included 8 sites along one primary cross-shelf line and 8 sites sampled
along four shore-parallel lines. Each shore-parallel line represents a distinct
part of the continental shelf – nearshore, mid-shelf, outer shelf, and
shelf edge – with water depths ranging from 10 to 100 meters. Examining
the sediment composition and grain size distribution at these sites will help
determine the types of current energies and characteristics of the benthic environments
that occur at these locations. This sedimentological analysis will serve as
a base-line study of the Charleston Transect as part of the College of Charleston
Transects Program. Our results will be compared to future sampling at these
locations to determine seasonal and interannual changes in sedimentology for
this portion of the southeast U.S. continental shelf.
POSTER
Sediment Analysis of the Continental
Shelf off Charleston, SC
-Ransom White III, Leg 03
Sediment analysis is a valuable tool for predicting water current flow patterns
and energy. The ideal continental shelf model progresses from coarse grained
sediments near shore to finer sediments off shore; passing over the inner-,
mid-, and outer-shelf, and shelf edge. Research conducted in November 2004 on
the continental shelf off Charleston, South Carolina, was designed to examine
sediment grain size and composition. Fifteen sediment samples were collected
along two transects, from the inner shelf to the shelf edge. The Gulf Stream
appears to cause sediment size variations to deviate slightly from the model
of a typical continental shelf. Grains get coarser as distance from shore increases
to the outer shelf, but shelf edge sediments are finer. The Gulf Stream allows
fine biogenics to settle off shore but not lithogenics. The coarse shelf sediments
are relict beach deposits meaning the Gulf Stream prevents deposition at the
mid-outer shelf.
POSTER
Sediment
analysis and grain size distribution of the continental shelf off Chalreston,
South Carolina
-Ranson White III
Sedimentological
analysis of the continental shelf off Charleston, SC
-White, Ransom C., Sautter, Leslie R., and Landon,
Glen
Research conducted on the continental shelf off Charleston, SC was
designed to examine sediment grain size and composition. Eleven stations across
the inner-, mid-, and outer-shelf regions as well as along the shelf edge were
sampled at least three times during four College of Charleston Transect Program
cruises. Generally, sediments in the study region are a thin veneer of modern
and relict sands, underlain by limestone hardground. Grain size variations deviated
from the classic fining-outward shelf model in that mean grain sizes irregularly
progressed from fine sand (2.5-3.0 Phi) on the inner-shelf to medium sand (1.5-2.0
Phi) on the middle and outer shelf regions. Sediments were composed predominantly
of lithogenic sands, with a higher concentration of relict lithogenics on the
outer shelf, most likely remnant from shoreline migrations since the Pleistocene.
Conversely, shelf-edge sediments were fine biogenic sands deposited in association
with the Gulf Stream. Transitional sea level phases have sculpted the continental
shelf across this area of South Atlantic Bight, leaving morphologies that skew
sediment distribution across the shelf. In addition to spatial variability,
temporal variations in sedimentology were observed in this study. Several samples
collected on different cruises at the same location varied significantly in
both grain size and composition. Videos collected of the seafloor collected
by a diver and with a remotely operated vehicle show evidence of migrating sand
megaripples, which may be responsible for the seasonal reworking and redistribution
of sediments.
GSA Abstracts with Programs, 2006, Vol. 38, No. 7
A Geologically Based Habitat Characterization
of an Outer Continental Shelf Ledge
-Hannah Giddens, Leg 02
Habitat characterization of Lionfish Ledge was conducted with video and sediment
samples collected aboard the R/V Savannah between May 17 and May 22, 2004, as
part of the larger Charleston Transects program. Lionfish Ledge was located
with a 100-khz sidescan sonar, video images were recorded from a ROV transect
on the ledge, and sediment samples were collected with a Smith-MacIntyre grab
sampler. Video image analysis quantified and described substrate and substrate
morphologies. Video analysis showed the transect to consist of 84.7% sediment
and 15.3% hard substrate. Grab sample analysis consisted of grain size and compositional
analysis. Grain size analysis showed coarse and medium grain sizes to dominate
samples. Compositional analysis determined the relative abundances of biogenic
and lithogenic materials. Compositional analysis showed 3 grab samples to be
composed mostly of lithogenics and 2 grab samples composed primarily of biogenics.
Two lionfish were observed in the area of highest relief. Megafaunal invertebrate
populations were qualitatively observed, however not quantified. Further studies
of Lionfish Ledge are needed in order to characterize the fish and invertebrate
community.
POSTER
Habitat Characterization of Continental Shelf Seafloor off Charleston, SC
-Stephen Long, Leg 05
Habitat characterization of seafloor sites on the continental shelf off Charleston was conducted using video and sediment samples collected as part of Project Oceanica’s Transects Program. Samples were collected aboard the R/V Savannah in November 2009, using a Phantom 300 remotely operated vehicle (ROV) and a Shipek grab sampler. In addition to these samples, ROV video images from November 2003 were sub-sampled and sediment analysis data from White and Sautter (2004, unpublished) were used. Adjacent transects of the continental shelf were compared in terms of substrate and sediment. The habitats observed included soft to hard substrate with features such as mottled ripples and rock outcrops. Relief ranged from less than 0.5 m to greater than 1.5 m. Epifaunal density was found to be primarily sparse, however abundant in areas of the greatest relief. Sediment ranged from coarse silt to very coarse sand. These results can supplement additional research being conducted.
POSTER
Substrate Characterization
of an Inner-Shelf Hardground Area: the Harris Meander
-Philip Antman, Leg 02
An outer region of the inner continental shelf off the coast of Charleston,
South Carolina was surveyed using: sidescan-sonar, ROV, and grab sample techniques.
A large meandering channel was present in the image compiled from the sidescan
data. 3 ROV dives were deployed transecting the study area and the meandering
channel. Date from these dives were used to characterize substrate distributions
in the area. Exposed hardground and soft ground areas were observed. Also quantified
were varying geomorphologies of the hard and soft substrate areas. Grab samples
taken at various distances from the channel help also to characterize the sediment
of this area, and to prove the possible origin of this meandering channel. This
study provides baseline data for comparison in future studies.
POSTER
Ground-Truthing Shelf-Edge Sidescan
Sonar Imagery
-Chris Stubbs, Leg 03
In May 2004, sidescan sonar data were collected along the continental shelf
edge off of Charleston, SC, and compared to remotely operated vehicle (ROV)
video and sediment to generate preliminary ground-truthing and habitat characterization
of a 4 km2 region of the continental shelf edge (Giddens, 2005). Further comprehensive
sidescan data of the same and adjacent areas were collected in November 2004,
and processed into an image mosaic with associated ROV and grab sample data.
Interpretations were made for the full 16 km2 sidescan region based on the features
identified in the May 2004 region. Potential broken rock pavement, mega-ripple
formations and homogenized sediment beds have been identified in the extended
region. The November 2004 sidescan data are useful for identifying large trends
on the sea floor. This research will provide background for more extensive study
and sampling in May 2005.
POSTER
Multibeam Mapping and Exploration of the Continental Shelf Edge
-Christopher Stubbs (Leg 03) and Ray Creede, Post-Transects Independent Study
In March 2006, the NOAA Ship Nancy Foster conducted a cruise on the continental
shelf edge off South Carolina to calibrate a new Kongsberg Simrad multibeam
sonar system. Students from the College of Charleston Geology Department assisted
with bathymetric data collection and have begun preliminary processing and evaluation
of identified seafloor features, using Caris HIPS/SIPS software. The data are
being contextualized with previously quantified shelf-edge sidescan sonar data
from the region collected during previous Transects Programs (Stubbs 2005, Giddens
2005) and Ocean Exploration submersible expeditions (Sedberry et al. 2002).
The most prominent feature discovered is an outcropping hard-ground structure
approximately 650 by 150m, with 10m vertical relief. It is oriented parallel
to shore along the shelf edge in water depths of 60m. Possible geological and
biological influences on the structure's origin and morphology are being explored.
POSTER
Multibeam Mapping and Exploration of the Continental Shelf Edge
-Christopher Stubbs, Leslie Sautter, and Ray Creede
In March 2006, the NOAA Ship Nancy Foster conducted
a cruise on the continental shelf edge off South Carolina to calibrate a new
Kongsberg Simrad multibeam sonar system. Students from the College of Charleston
(CofC) Geology Department assisted with bathymetric data collection and have
begun preliminary processing and evaluation of identified seafloor features,
using Caris HIPS/SIPS software. The data are being contextualized with previously
quantified shelf-edge sidescan sonar and sub-bottom profiler data from the region
collected during CofC's Transect Program cruises and NOAA Ocean Exploration
submersible expeditions. The most prominent feature discovered is an outcropping
hard-ground structure approximately 650 by 150 m, with 10 m vertical relief.
It is oriented parallel to shore along the shelf edge in water depths of 60
m. Possible geological and biological influences on the structure's origin and
morphology are being explored.
GSA Abstracts with Programs, 2006, Vol. 38, No. 7.
On the Nature of
Rocky Outcrops on the Continental Margin East of Charleston, South Carolina:
Pavements, Meander Scars, and Linear Trends as Documented through Direct Observations
and Remote Geophysical Methods
Harris, M. Scott, Sautter, Leslie, Lund, Prentiss, Stubbs, Christopher, Antman,
Philip, Giddens, Hannah, and White, Ransom
The lack of sediment availability on the Continental Shelf in the South Atlantic
Bight (SAB) combined with a shallow Tertiary geological framework creates a
mosaic of intermittently to consistently exposed rocky features that range from
very low-relief pavements to linear ridges of rocky exposures two to three meters
high and several kilometers long. This paper focuses on the geophysical data
results of three educational cruises conducted as part of the NSF-funded educational-focused
Transects Program at the College of Charleston and highlights both geological
mapping in the offshore as well as geologic mapping training and analysis of
field data.
As part of the SAB and with a significant amount
of unmapped critical benthic habitat, the study area along a transect extending
from Charleston, South Carolina to the shelf edge contains three distinctly
different bottom types ranging from 7-m to 50-m water depth. Sidescan sonar
mosaics, chirp subbottom profiling, ROV-video transects, bottom grabs, and shallow
sediment cores were collected to characterize and document the nature of the
materials along various transect sites. The inner most, shallow site consists
of primarily an extensive, intermittently exposed pavement of exposed shales
and limestones. The intermediate depth site at approximately 18-m depth includes
a series of entrenched tidal creek or river channel meanders that incise a rocky
platform, creating areas of varied relief. The deeper offshore site at approximately
50-m depth includes a series of boulders along an extensive high-relief ridge.
Each bottom character and the potential for critical
habitat in these regions is directly related to the nature of the nearsurface
geological materials and stratigraphic architecture, sea level changes and fluctuations
since the last glacial maximum, minimal sediment input from other than local
sourcing from eroding rock, and the nature of the relief and subsequent burial
and exposure due to modern shelf processes. We do not submit here a new classification
for hardground and habitat types offshore, but rather provide the reader with
a sense of the differences across this portion of the shelf. As these studies
continue, we will further investigate the nature of the seafloor with respect
to hardground distribution and type, changes in these types through time, and
suitability for habitat for each type.
Published in: GSA Abstracts with Programs, 2006, Vol. 38, No. 3
