9. Research Questions
1. What is the biotic response to shoreline armoring
a. Species richness and abundance
2. Herbaceous plants vs. woody plants
a. Mature plants
b. Sprouts
c. Seeds
3. Any land crab predation on sprouts?
4.What is the community composition between different soil
textures?
14. Results
1.What is the biotic response to shoreline armoring?
200
150
50
0
100
Herb Seed Sprout Trees Herb Seed Sprout Trees
6
0
4
2
Richness
Abundance
NA
T
RW
NA
T
RW
15. Results
Hibiscus tiliaceus (native) p > 0.05
Inocarpus fagifer (native) p > 0.05
Thespesia populnea (native) p > 0.05
Terminalia catappa (native) p < 0.05
Cocos nucifera (native) p > 0.05
Callophyllum inophyllum
(native) p > 0.05
Cordia subcordata (native) p < 0.05
Barringtonia asiatica (native) p < 0.05
Vigna marina p > 0.05
Wedelia trilobata p > 0.05
Grasses p > 0.05
Abundance by species along natural coast vs. rock wall coast
18. Results
R2 = 0 .015SproutAbundance
Crab Hole Abundance
3. Do the
number of
crab holes
correlate
with the
number of
sprouts?
No correlation
19. Results
4. What is the community composition between different soil
textures?
T. catappa (w)
I. fagifer (w)
B. asiatica (w)
C. nucifera (w)
H. tiliaceus (w)
P. pallida (w)
T. populnea (w)
T. argentea (w)
PercentComposition
Loam Loamy sand Rocks Sand S.C. loam Sandy loam Silty clay
SoilTexture Category
20. Results – Points of Interest and Discussion
Understanding the Biotic Response Surveyed
▪ Between both coastal types, T. catappa, C. subcordata, B.
asiatica are significantly different
▪ Native, coastal strand species
▪ Woody plants
▪ Can be ocean-dispersed
▪ Natural coast Woody, coastal strand plants
▪ Rock wall coast Herbaceous plants
▪ Sustainability concerns
21. Professors: Stephanie Carlson, Cindy Looy, Brent Mishler,
Patrick O’ Grady, Jonathon Stillman,Vince Resh
GSIs: Eric Armstrong, Dave Kurz, Camilla Suoto
Gump Station Managers: Frank and Hinano Murphy
Drivers, mangrove expert : Cheryl Resh, Dr. Orlo Steele
Field friends: Dana Lin, Karen Gallardo, Katie Horton, Kyle
Ingraham, NumfahVanitchanant
Mo’oreaClass of 2015
Acknowledgements
Photo #:
Talk about natural slope, but with rock wall there is no more natural slope/inclination into the ocean
Hi, I’m Erica and my project is about an analysis of armored shorelines as barriers for coastal vegetation. I am a Geography major, and coming into this class I had a background in geomorphology, but very little in biology. So, I decided on a coastal project, where I could expose myself to biology and still study geomorphology at the same time. Mo’orea was an ideal place to study coastlines because as an island it’s very accessible, making it a place of high activity, ecologically and socially.
Alright, so, we are all familiar with this landscape. We all know a good beach with palm trees. What’s not as obvious is how coastlines can change pretty easily. Natural coasts are dynamic. They move and take away sediment along coasts to create beaches or to transport sediment to other areas for plants to establish. So, because it’s beautiful and because it’s accessible, over 40% of the global human development is along coasts. To secure these developments along a changing coast, we decide to armor our coastlines.
But, what is an armored shoreline? It’s a method of physically protecting the shoreline with large boulders. They are installed to keep human development safe from wave action and erosion processes.
There are many forms of shoreline armoring, but like most coastlines throughout the world, they are commonly found near or in front of roads, hotels, and homes.
Here’s a side by side picture showing an example of an adjacent natural coast and rock wall coast. Notice that the natural coast has a gentle slope, but the rock wall has none and is also inundated with water.
Rock walls help us as humans, but are they actually too overprotective? There are ecological impacts from shoreline armoring. They include physically removing habitat to install the rock walls and can result in an imbalance of sediment deposits along a coast. Rock walls also challenge seeds to reach substrate and establish, which would really mean plant dispersal by ocean would lower.
#2. Is there a difference between herbaceous and woody plants between natural and rock walls?
#3. Are there any land crab predation on sprouts?
In my experimental design, I needed paired sites of adjacent natural and rock wall coast. I sampled using 2m square quadrats and surveying 4 times randomly along a 25 meter section. For data, I wrote down Species, Count, and % Cover for woody, herbaceous, sprouts, seeds, and # of crab holes.
Here is Frank and Hinano Murphy who are both station managers at Gump Research Station. They showed me the coastline by boat, so I could see where adjacent coastal types were and also learn about the history of rock walls.
This is me surveying at one of my 8 sites. In this picture I wanted to point out where I decided to lay my transect. I put it at the average high water mark, which was just indicated by where plant and marine debris had collected along the shore.
To quantify the biotic response of each coast type to shoreline armoring, I calculated the Species Richness and Abundance. Natural is in the red orange color, and rock wall is in turqouise. They are not significantly different, but there is a difference. Rock walls had higher richness and abundance in Herbaceous plants.
Natural coasts had higher richness and abundance for seeds and sprouts.
I ran a test to do a species specific analysis to see if there were different abundances between natural and rock wall coasts. Out of all these, 3 species had a difference with a higher abundance along natural coasts. They’re all native, woody coastal strands.
These are the results to my 2nd question. To see differences between woody and herbaceous plants between coastal types, I ran a test and got significant results. This is a stacked bar plot that visualizes the differences. For natural, you can see there are more seeds and sprouts from woody plants, while rock walls house more herbaceous plants.
This is another visualization of data for herbaceous vs. woody plants between natural and rock wall. Natural is in green and rock wall is in blue. They overlap
One of my hypotheses was that land crabs ate the sprouts. For this question, I tried to test if the presence of land crabs, sampled by number of crab holes, had an affect on sprouts, but turns out, there is no correlation.
For the community composition between different soil textures, I found that Hibiscus and Thespesia were most abundant throughout all soil types. However, Loamy sand and Rocks housed the most species. To clarify, my soil samples were taken in 1 spot of the entire 2m squared quadrat, so the category “Rocks” does not represent the entire substrate of the quadrat.
Here, I wanted to discuss the results I found most compelling. Between both coastal types, 3 species had significantly higher abundance in natural coastline than rock wall. All of these are native, coastal strand woody plants. Since they can be ocean-dispersed, this may be indicating that rock walls are inhibiting plants that have ocean-dispersed seeds. In combo with the other analysis of woody versus herbaceous plants, natural coast housed more woody coastal strands while rock walls housed more herbaceous plants. From my surveys, the biotic response is not necessarily a decline in vegetation, but a difference in TYPE of coastal vegetation. A concern is that, In the future, the sustainability of biodiversity could be affected due to these armored shorelines because chances of seed penetration and ultimately establishment on the island would be lower.
