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Does Cape Elizabeth have a Healthy Marine Ecosystem?
Abstract:
My project’s purpose is to determine whether or whether not Cape Elizabeth
has a healthy marine ecosystem. I used Vital Signs to record and count data from
inventories on the crab species and periwinkle species. I did this for each individual
species so I could determine if the invasive species were dominating the native crab
and periwinkles. My findings indicate that the green and Asian shore crab and
common periwinkle (all invasive) have diminished the native crab and periwinkle
population. I conclude that creating a business centered around the harvesting of
invasive species could reduce the population in an environmentally and financially
conscience way.
Introduction:
My essential question is Does Cape Elizabeth have a healthy shore
ecosystem? The topic is on multiple organisms in one location rather than one
organism in multiple locations. I chose this because it is very specific, and Maine has
several abundant invasive species. With the data I have collected, I can conclude if
the native species are being affected negatively by invasive species. I think this a
very important study because the uncontrollable spread of an invasive species could
have a disastrous effect on Maine’s shore life. I have decided in this paper to focus
primarily on invasive species green crab and common periwinkle.
A Portland Press Herald article on the growing green crab population had this
to say:
“The crabs, native to Europe, first became noticeable in Maine around the
turn of the 20th century. They threaten the soft-shell clam fishery, which is the third
largest in Maine and generated almost $17 million in 2013, and damage coastal
habitats like eelgrass beds and salt marshes. State officials say the crabs have
increased population as the temperatures of the ocean off of Maine have risen.”
The other invasive species is the common periwinkle. The common
periwinkle now covers the intertidal zones of Maine, possibly degrading the native
smooth and rough periwinkle populations.
My hypothesis is that unfortunately green crabs and common periwinkles
have diminished and/or pushed out native species. My reason behind this is the
Jonah and Rock crab, and the smooth and rough periwinkle inhabit the same areas
and have the same diet as their invasive counterparts, this means their increasing
numbers hurt native species.
Methods:
I have decided to focus on the effect of green crabs and common periwinkles
on Cape Elizabeth’s marine ecosystem. To answer my question I used primarily Vital
Signs data from GMRI. There were many inventories conducted in Cape Elizabeth,
so I can use this data rather than actually having to design an experiment. My
method is to make sense of data already there, and draw conclusions for my EQ
from the website.
My first step is to export my data, then I sorted through 355 studies and
singled out marine surveys. Then I counted the number of confirmed studies of
individual crab species, and periwinkle species. I also found it important to read the
biodiversity reports of the studies on invasive species to determine whether or
whether not native species were present. My findings will consist of both objective
(confirmed studies), and nonobjective (students opinions of the findings and
biodiversity reports) I will take the raw data and express it in graphs and written
explanations on my findings to answer the question: Does Cape Elizabeth have a
healthy marine ecosystem.
Results:
My raw results were in Cape Elizabeth: 24 confirmed invasive green crab
sightings, 15 confirmed invasive Asian shore crab sightings (Invasive Species,) 2
confirmed Native Jonah carb sightings, and 2 confirmed native rock crab sightings.
This small amount of data has illustrated a lack of native species, but I extended my
research to biodiversity reports to determine if native species still thrived in Cape
Elizabeth. I read over the green crab studies to see what other crabs were in the
area. Not all studies discussed biodiversity, but 10/24 studies reported only green
crabs and/or Asian shore crabs. Many people reported things like this “We were
surprised about how many invasive crabs we found on the beach under the slippery
seaweed. It seemed like the native crabs had disappeared.” For this study quotes
like these are just as important as field data. I created two graphs to illustrate the
clear dominance of invasive species.
This pie graph above shows the percentage of native species found to
invasive species found. You can compare them as percentages to the total crab
count. Green Crabs make up over 50% of the total and invasive species make up
around 90%, while native species contribute less than 10%.
Below you can see the quantities compared to each other in a frequency
histogram.
Below is crab biodiversity. In this graph you can see if native species lived
alongside invasive species. Most of the time there was a clear dominance of
invasive species in the area. 10 times people reported only invasive species, only 4
times did people find native crabs.
My second study was of how the invasive periwinkle population in Maine is
affecting the native smooth and rough periwinkles in Cape Elizabeth. I looked
primarily biodiversity comments because less overall periwinkle studies were
conducted. These reports show whether or not the native species are present and if
the native species have grown out of control. My findings were 7 of the studies
reported that they only found common periwinkles, and none or very few smooth or
rough periwinkles. Only one study reported a diverse population. This graph
illustrates the dominance of the invasive species.
Conclusions:
My one sentence to sum up the marine shore life: Cape Elizabeth boasts
many thriving native species of shore life, but the native crab and periwinkle
populations are overrun by the invasive Green crab and common periwinkle. My
results clearly showed an unbalance. People now seldom find native rock or Jonah
crabs, but green crabs are common on beaches. This poses a major and current
threat to not only the marine ecosystem but Maine’s multi-million dollar shellfish
industry. Green crabs prey upon soft shell clams, causing significant damage. A
Portland Press Herald article on the crab invasion discussed the repercussions of
the invasive green crab. “The crabs, native to Europe, first became noticeable in Maine
around the turn of the 20th century. They threaten the soft-shell clam fishery, which is the
third largest in Maine and generated almost $17 million in 2013, and damage coastal
habitats like eelgrass beds and salt marshes. State officials say the crabs have increased
population as the temperatures of the ocean off of Maine have risen.” In conclusion this
population has thrown the ecosystem off and damaged the environment. I suggest
solutions lie in turning the green crab into an industry, use it as bait or food to counteract
the growth.
My study of the common periwinkle population has exploded in Maine, my
results showed surprise at the large population of the invasive species, and very few
sightings of the smooth and rough species. My work is backed up by lots of research on
the subject. The invasive population though diminishes the native populations might have
an important role in the ecosystem. An article on the Natural Museum Of History titled
Morphologic Variation in the Common periwinkle” says that the common periwinkle
population consumes large amounts of algae that keeps the food chain in balance. This is
credible, but I question if the native species could do the same if their numbers weren’t so
thin. Cape Elizabeth has many different native species and for the most part a healthy
ecosystem, with the exception of a damaging invasive population of green crabs and an
overabundance of common periwinkles. I believe that the clearest solution is to build an
industry around theses species, that will allow people to make a profit by killing these
invasive species. Eradicating them will benefit the native species. If we start eating these
animals or using them as bait we can provide incentive to catch them and create jobs and
an industry that helps Cape Elizabeth’s and Maine’s ecosystem.