Utilization of Microbial Exopolymers by a Deposit-feeding Brittlestar: Trophic and Toxicological Implications

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The Marine Science Program at Savannah State
University
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Dionne Hoskins, Ph. D. Fishery Biologist/Associate
Professor National Marine Fisheries
Service/ Savannah State University
dionne.hoskins_at_noaa.gov
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The bottom is called the benthos and the
organisms that live there are called the benthic
community

• My Research Interests are in the ecology of
  marine sediments as it relates to
• Food availability for deposit feeding organisms
• Essential Fish Habitat

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Defining Deposit-Feeder Ecology
deposit feeder satisfies its nutritional
requirements from the organic fraction of
ingested sediment (Levinton, 1987)

• typically lives at or below the sediment
  surface or attached to a hard substrate
• includes filter/suspension feeders, sediment
  ingesters, particle feeders

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Who lives on the bottom?
Littorina sp.
grass shrimp
clams
fiddler crabs
flatfish
shrimp
blue crabs
crabs
bacteria
flounder
worms
Glycerid bloodworms
Amphitrite
molluscs
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Other benthic polychaetes
Amphitrite Arenicola
Pseudiospio
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What else?
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Benthic Microbial Ecology
Lets talk
Microbial EPS
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Extracellular Polymeric Secretions (EPS)
glycocalyx, biofilms, exopolysaccharides,
exopolymers

• Produced by algae and bacteria and
• secure attachment
• concentrate DOM sequester nutrients
• offer protection from environmental stresses
• provide a barrier against toxins
• localize concentrate biotoxins,
• extracellular enzymes

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Chemical Characteristics of EPS

• usually heteropolysaccharides
• mostly water, 1-2 polymer
• have high surface area
• negatively charged
• acidic (carboxyl groups of
• uronic acids)
• Bind divalent cations
• like Ca, Mg, Na, Cd, Cr, Pb, and Ni)

SEM courtesy of Alan Decho
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Deposit feeder ecology includes the study of
processes which affect food availability to
benthic organisms
how bottom feeding animals get food
how deposit feeders interact with processes in
the estuary which affect nutrient cycling
how deposit feeders interact with other prey or
predatory organisms
what biological, chemical, and physical factors
affect their food availability
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My Current Project in this area a 12 month study
Seasonal macrofaunal fluctuations in a
cyanobacterial mat community (Williamson Island,
GA)
Diatom film
Cyanobacterial mat
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N
SSU
Williamson Island Lagoon
We are measuring EPS abundance
Macrofauna Microbial Community
LMRCSC interns Steward James and Jamila Jenkins
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Preliminary Results
480 samples!

• Capitellid (polychaete) worms dominate the
  samples we have identified to date
• High numbers of polychaetes in winter (Jan) cores
• EPS concentrations high in winter cores
• EPS is present in cores w/o dense cyanobacterial
  mat

Significance EPS is available for benthic
organisms Diatom films may produce significant
mass of EPS
LMRCSC research assistants Anthony Bell William
Price
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So?
Well, if they dont eat,
She dont eat.
And if she dont eat,
They dont eat. And if they dont eat,
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Yeah, thats right.
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Current Faculty Projects by NOAA research
priority area
Biological Assessments (Richardson, Curran,
Hoskins) Distributions of the freshwater
molluskan fauna of the Canoochee River Larval
distribution of winter flounder Young of the
year eel distributions in southeast
Georgia Effects of ray pits on meiofaunal
communities Effects of Salinity on Palaemontes
pugio Seasonal macrofaunal fluctuations in a
cyanobacterial mat community Distribution of
blue crabs in coastal Georgia Marine Chemical
Processes (Pride , Richardson) Sedimentation
and micropaleontology in Georgia
estuaries and marshes Water quality in all of
Georgias coastal counties
Adopt-a-Stream programs with public
schools in each county Habitat Assessment
(Curran, Richardson, Pride, Hoskins,
Franklin) Deadmarsh Phenomena in Coastal
Georgia
SSU Spartina greenhouse
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Faculty Research
Dr. Joseph Richardson water chemistry, aquatic
ecology
Dr. Carol Pride paleoceanography, marine
sediments Dr. Carla Curran fish biology, marsh
ecology
Dr. Dionne Hoskins benthic ecology Dr. Matthew
Gilligan ichthyology, Biogeography
Captain Jay Rosenzweig, Boat Operations Ms
Megan Bradley Grants Administrator
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Essential Fish Habitat
The deadmarsh phenomenon in coastal Georgia
Possible Causes Drought Pollution Microbes Predat
ion
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6 sites in GA, 2 monitored by SSU
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Marina Nimrod and Jamila Jenkins preparing a
control site for replanting

• Deadmarsh research in my lab
• Replanting
• Effects of snail density and microbial
• community on Spartina alterniflora

Crystal Jackson collecting Littorina snails for
a density experiment
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Kimberly Brown May 2003 graduate Marine Science
Richard Hodges Senior Biology
John Braxton Senior Biology
Steward James Senior Marine Science
Marina Nimrod May 2003 graduate Marine Science
Julia Pearson Senior Marine Science
Jessica Green Junior Computer Science Technology
Gregory Hunter May 2003 graduate Marine Science
Ranaldo Smith May 2003 graduate Marine Science
Ebony Henderson Junior Marine Science
Muhammad Ali Cochran December 2002
graduate Marine Science
Dori-Lynn Coburn Senior Marine Science
Nena Strachan Senior Biology
Qadree Jackson Junior Marine Science
Jamila Jenkins Senior Chemical Engineering
Technology
Jared Dillet May 2002 graduate Marine Science
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