Re-evaluating models to take on new challenges in ecology and evolution
Final presentation draft 3.14.14
1. Purple Marsh Crab and Cordgrass
Population Densities within South
Carolina’s ACE Basin
Alejandra Luna, Ramsey Millison, & Tara Poyer
2. Estuaries
“Provide more services per unit area than any
other ecosystem worldwide” (Gedan K. B. et al. 2011)
3. Salt Marsh
Are transitional areas located
along intertidal zones of
estuaries (Wenner, 2010).
Serve as shoreline erosion
prevention.
4. Salt Marsh Die-Off in Cape Cod, Massachusetts
Cordgrass die off on seaward
edge of salt marsh
Area critical to marsh
development and maintenance.
Decreasing barrier capabilities
Gedan K. B. et al. 2011
Gedan K. B. et al. 2009
6. Cordgrass Die Off Due to Purple Marsh Crab
Found that all
die-off areas had
over 100 crab
burrows/m2
Speculated
overpopulation
is due to
overfishing of
predators of
purple marsh
crab.
(Holdredge et al. 2008)
(Smith et al. 2013)
= die-off marsh
= healthy marsh
110
25
7. Purpose of the Study
1. Establish baseline populations for both cordgrass
and purple marsh crab in relatively unfished areas.
2. Characterize population relationships between
cordgrass and purple marsh crab.
3. Assess populations of other crab species present.
ACE Basin
8. Our Study
QUESTION: What are the population characteristics of
purple marsh crab and cordgrass?
How do they compare to those studied in Cape Cod,
Massachusetts?
HYPOTHESIS: As the population of purple marsh crab
changes, the population of cordgrass will change.
PREDICTION: As the population of purple marsh crab
increases the population of cordgrass will decrease.
13. Results: Correlative Analysis
y = -3.2859x + 219.39
R = -0.336
0
50
100
150
200
250
300
350
0 5 10 15 20 25 30 35 40 45
Cordgrass(stalks/m2)
Purple Marsh Crab (burrows/m2)
Botany Bay A Botany Bay B Ashepoo
14. Population Density Comparisons Between South
Carolina ACE Basin and Cape Cod Massachusetts
0
50
100
150
200
250
300
Ashepoo Botany Bay A Botany Bay B
Stalks/m2
0
5
10
15
20
25
Ashepoo Botany Bay A Botany Bay B
Burrows/m2
ACE Basin
‘Unhealthy’ Area
Cape Cod
‘Healthy’ Area
Cordgrass
Purple Marsh Crab
270 stalks/m2
0 stalks/m2
25 burrows/m2
110 burrows/m2
(Holdredge et al. 2008)
15. Botany Bay A
Botany Bay B
Ashepoo
male= = female=
Results: Purple Marsh Crab Size/Sex Distribution
male= 1 female=18
male= 6 female= 3
male= 18 female= 22
x̅ = 11.8 SD = 3.54
x̅ = 13.1 SD = 1.48
x̅ = 14.8 SD = 3.97
NumberofPurpleMarshCrabs
16. Results: Community Interactions
Salt Marsh Mud Crab
(Panopeus obesus)
Atlantic Mud Crab
(Panopeus herbstii)
Squareback Marsh Crab
(Armaces cinereum)
Botany Bay
A
n=45
Botany Bay
B
n=44
Ashepoo
n=72
Diet Predators
Squareback marsh 11.11% 75.00 % 27.78%
Cordgrass,
leaves, aphids
Birds, mammals, larger
crabs
Atlantic Mud Crab 6.67% 0 2.78%
Periwinkle
Snails
Blue Crab (C. sapidus)
Salt Marsh Mud 17.78% 2.27 % 0
Periwinkle
Snails
Blue Crab (C. sapidus)
Purple Marsh Crab 64.44% 22.73% 69.44% Cordgrass Blue Crab (C. sapidus)
17. Salt Marsh Mud Crab Atlantic Mud Crab
Squareback Marsh Crab
Blue Crab
Purple Marsh Crab
Cordgrass Periwinkle Snail
18. Conclusions
Purple marsh crab and cordgrass populations are
equally healthy in comparison to the healthy salt
marshes of Cape Cod.
Purple marsh crab populations appear to affect
cordgrass populations, however more populations
assessments are needed throughout the ACE basin
19. Acknowledgements
DePaul University Department of Biological Sciences for
funding this research.
Special thanks to South Carolina’s Department of Natural
Resources for allowing us to work in the salt marshes and
providing room and board during our research.
Editor's Notes
Change title
Estuaries: A mixing of saltwater and freshwater
Services: nurseries for commercial and naturally occurring fish. Important for their biochemical and pollutant filtering capabilities.
Include habitats like the Maritime Forest and Salt Marsh: in the photo to the right is an example of a salt marsh
Temperature, salinity, and water depth constantly change due the rise and fall of tides
Salt marshes have a diverse variety of organisms
Talk about Top down systems (switch orientation of arrows)
(maybe add actual numbers in die off graph: 110 for die off, 25 for healthy)
Put circle a little to the left and a little down, and make it smaller, Please! Make the other circle smaller too.
Not Correlation, this is a Regression. Also say how does this compares to MA?
Tara fix the axis on these please! Also we need to do a single sample t-test in order to see significance in differences. [add error bars!]-make these bigger!!!
Not sure what you guys want to do about the picture distortion. Also for width means and standard dev. Should we include the <11 mm data in calculations. For now I’m going to include it. Also Tara could you do the alignment thing for the mean and SD. Thanks.
Put circles around the bolded numbers. Not sure where the circles should go. I think the circles need to emphasize the percentage of Squareback crabs in Botany Bay B, the percentage of purple marsh in Ashepoo and Botany Bay A. Circle also need to be animated.
Switch arrows to pointing up from cordgrass, and extend arrows to look like arrow from blue crap to salt marsh mud crab. Should all the arrows be the same size?
Cant say stable here for first point. And unsure of last point.