Marine Ecology Research Opportunities
Dr. Walters’ Lab
Snails, Snails, Snails
Recent papers by Bertness and Silliman raised the profile of intertidal marsh snails and posed many intriguing questions about the role of snails in salt marsh dynamics.  Along with Dr. Hutchens, CCU Biology, we are examining the following questions focusing on the marsh periwinkle, Littoraria irrorata, as a model organism:
1) What are the natural movement patterns of snails and what factors affect those movements?
2) What are the long-term contributions of snails to salt marsh ecosystem dynamics and energy flow?
3) Do L. irrorata and S. alterniflora interact in the marsh (e.g., snails gardening plant fungi, plants developing physical/chemical defenses to snail foraging, etc.)?
Habitat Restoration
Coastal industrial, residential and recreational development has accelerated the loss of critical estuarine habitats (e.g., salt marshes, oyster reefs).  In collaboration with Dr. Coen, SCDNR, we have been examining the possibility of establishing structurally and functionally similar marsh and reef habitats in GA and SC.  We also have been assessing the most effective methods and costs/benefits of restoration efforts.
Crustacean Dynamics
Harpacticoid copepods (far right) are the first or second most numerous marine micrometazoans living in or on marsh sediments and plants.  Copepod communities associated with Spartina stems are isolated from one another at least 2x per day.  We have been studying the population and community dynamics of the stem-copepod association in order to examine the assumptions and predictions of Metapopulation Theory.
Habitat Boundaries
Increasing residential and industrial development of coastal environments (top image, right) has resulted in increased loss of natural terrestrial-saltmarsh boundaries (bottom image, right).  With Drs. Hutchens, Luken and Koepfler, CCU Biology & Marine Science, we have been examining the boundary loss effects on the ecological dynamics of high-marsh communities.
The above are just a few examples of ongoing research projects in which students and I have been involved over the past few years.   If you are interested in participating in any of these or other research projects please contact me at kwalt@coastal.edu, 349-2477 or stop by my office in SCX4.
Blue crabs are reported to exert top-down regulation on snail numbers in the marsh limiting the snail’s ability to over-graze cordgrass.  Note the numbered tags on the snails enabling mark-recapture studies.
Salinity differences between Murrells Inlet barrier island and mainland developed and undeveloped sites.  Salinities were greater within developed site sediments.
Movement of marked snails out of 0.25 m2 plots in which 0 or 50% of the Spartina stems had been removed.  Inconsistent with past studies, data suggest that snails are very mobile within salt marsh habitats.
Snail density  differences between Murrells Inlet barrier island and mainland developed and undeveloped sites.  Littoraria were only present in significant numbers in developed sites whereas Melampis densities were greater in undeveloped sites.
Murrells Inlet developed (top) and undeveloped (bottom) mainland sites.
Salt marsh restoration project (GA) showing initial Spartina planting (top left) and restored (top right) and natural marsh (bottom) growth 2 yrs. later.
Ongoing oyster reef restoration experiment in Murrells Inlet testing the effectiveness of bag shells and stakes as oyster recruitment and reef restoration methods.
Micrometazoan density differences on Spartina standing-dead stems collected during low and high tides in a GA saltmarsh.  Greater copepod numbers are found on stems during high tides.
Examples of male, female and copepodite harpacticoid copepods.
Harpacticoid copepod numbers trapped in the water column of a GA salt marsh during day and night incoming and outgoing tides.  Diel and tidal differences suggest copepods are dispersing actively through the water column.
Copepod numbers on standing-dead Spartina stems maintained within experimental chambers in which initial densities were either unchanged or increased.  Day 0 to Day 5 changes indicated copepod migrations between stems.
Seasonal changes in L. irrorata densities among low-, mid- and high-marsh zones within the Waites Island barrier salt marsh.  Distributional differences may result from differences in settlement or predation pressure.
New and old shoot leaf differences in S. alterniflora cinnamic acid composition within high- and low-marsh zones.  Cinnamic acid concentrations consistently were greater in old stem leaves and may inhibit L. irrorata feeding.
Yearly structural differences between natural and restored marsh S. alterniflora live, standing-dead and new shoot densities within GA high-, mid- and low-marsh zones.  Stem densities were similar between natural and restored marshes by 1998, ≈2 yrs. after restoration.
Yearly differences in Gukensia demissa, ribbed mussel, shell and tissue growth  between natural and restored GA salt marshes.  Except for the low-marsh, mussel growth was greater within the natural marsh and indicated continued functional differences within the restored salt marsh.
(Last updated 1/04)