Midterm Paper
Introduction
Uca minax
is a fiddler crab species found along the United States’ east coast, as well as
in the Gulf of Mexico. They are easily differentiable from other fiddler crab
species due to their red joints, giving them their common name: a red-jointed
fiddler crab (see Figure 1). Males have one major claw on either side of their
body, which can grow to be up to fifty percent of their body mass, and a
regular-sized claw on the other side, while females have two normal-sized claws
(Bethany Fisher). Fiddler crabs live in coastal wetlands in the intertidal
regions of the coast, meaning seawater from the ocean periodically floods their
habitat based on the high and low tides. Salt marshes are broken down into the
high marsh, midshore, and low marsh. The low marsh is the least salty of the
three portions; this is due to the fact that is most always submerged by water,
lessening the amount of evaporation occurring. The Uca minax mostly inhabit this region of the wetlands due to its low
salinity (Susan Woodward).
Figure 1: The above photo is a Uca minax fiddler crab, easily identifiable by the red claw and
appendage joint (Michael Rosenberg).
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Figure 2: Above is a photograph of Spermaceti Cove
on Sandy Hook, New Jersey, the site of
fiddler crab counting for this
experiment (Bri Astorino).
A
population assessment will be conducted by counting fiddler crabs at Spermaceti
Cove on Sandy Hook, New Jersey, in order to determine the status of the
species, whether or not it is increasing, decreasing, or remaining the same,
and, using statistics and past years' data collection, discover any population
trends over the years. Ecology, the study of relating the organism to their
habitat, will be used in order to determine how the Uca minax species' habitat affects the crabs themselves. The hypothesis for this study is as follows: Uca minax fiddler crab species located
at Spermaceti Cove on Sandy Hook, New Jersey will increase in the future. This
longitudinal study incorporates baseline data from the 2016-2017 data
collection period and combines it with the data collected this period,
2017-2018, in order to see any trends in the fiddler crab population at
Spermaceti Cove on Sandy Hook, New Jersey.
Science Concepts in Experiment
All
scientific experiments begin with the use of the scientific method and its
first step, asking a question. In the case of this longitudinal study, a
scientific study that is continued with the exact same method for a long period
of time in order to see any potential trends in a population, the question is
what will happen to the population of Uca
minax fiddler crabs at Spermaceti Cove on Sandy Hook, New Jersey as the
years go on. The trends of their population are especially important in the
case of the Uca minax species, as
they are an indicator species. As mentioned above, an indicator species makes
it very easy to determine the state of their habitat; should there be a low
population, it is expected that the habitat is lacking the necessities for life
and is, therefore, unhealthy. Conversely, if the species is thriving, it is
expected that the habitat is very suitable for life.
Next,
one must research for background information to further educate his- or herself
on the topic being studied. In this case, over forty primary sources, including
scientific research papers, newspaper articles, and books, were procured, read,
and annotated. The topics researched include, but were not limited to,
statistics and the statistical calculations that are conducted with
longitudinal studies, the ecology of the Uca
minax fiddler crab species, general fiddler crab knowledge, information
specific to the red-jointed fiddler crab, characteristics of the crab’s
habitat, coastal wetlands, more specifically salt marshes, and the other
organisms living in salt marshes. Through the obtainment of this many primary
sources, all of the information learned helps one to gain a better
understanding of the Uca minax’s
behavior, characteristics, and interaction with their habitat, or their
ecology. The following two paragraphs give a brief overview of the information studied
through this research.
Uca minax
fiddler crabs have horizontal indents behind their eyes that are perched on a
stalk, with a brownish-gray carapace and red claw joints. All male fiddler
crabs have one major claw, which can grow up to half of the crab’s body weight,
and one minor claw, equal in size to those of a female’s claw. Males can be
either right or left-clawed, meaning that the larger claw males have can be on
either side of their body. Because of their larger claw, or cheliped, males
take two times longer than females to feed. They use these claws, combined with
the quality of their burrow, to attract a female to mate with (Fisher). Their
major claws are also used to fight off any other males, whether it is for a specific
female or territory, as they are very territorial creatures (see Figure 1 for a
photograph of a Uca minax fiddler
crab). Should a male lose their cheliped, their remaining small claw will
either grow bigger or they will regrow it in the next molt; the process to
regrow it varies between fiddler crab species (Hogarth).
Coastal
wetlands are places with halophytic plants, meaning that they can sustain the
constant flooding of salt water, and are characteristic of large masses of
spartina cordgrass living there (see Figure 2 for a photograph of a coastal
wetlands environment). They are in a part of the intertidal zone protected from
most of the elements, such as wind and strong waves (U.S. Fish & Wildlife
Services). The ample food supply in the habitat makes it an important place for
migrating animals to take a break, as well as for baby fish to nurse. The
plants' ability to hold in extremely high amounts of carbon and nitrogen lessen
the effects of global warming. By absorbing the ocean's energy, they prevent
flooding and land erosion (Environmental Protection Agency). The freshest
marshes are at the bases of mountains, as they provide glacial runoff. Fiddler
crabs prefer a low salinity, as closest to freshwater as possible, making this
an ideal habitat (Coultas). The burrowing moves around soil, since the crabs
have to dig and make pellets with the excavated soil at the base of the hole.
Bioturbation is when animals move sediment, exactly what happens with fiddler
crabs in coastal wetlands. This aerates the soil and allows the nutrients to be
moved around. This increases soil water content and nitrogen and carbon
turnover, making the coastal wetlands that much more productive (Chattergee).
Determining
a hypothesis follows researching the topic. The hypothesis for this
longitudinal study is as follows: The Uca
minax fiddler crab species located at Spermaceti Cove on Sandy Hook, New
Jersey will increase as the years go on. Because statistics are used to
determine whether or not the data procured supports the hypothesis, a null
hypothesis is also necessary. A null hypothesis, generally speaking, claims the
opposite of the hypothesis. The null hypothesis for this study is as follows: There
will be no difference in the Uca minax
population at Spermaceti Cove on Sandy Hook, New Jersey over the years.
To
test the hypothesis, the fiddler crabs were counted at the site during new and
full moons at low tide during their breeding season, in order to ensure as many
crabs as possible were seen. They must be counted during the breeding season
because outside of this season, they remain inside their burrows, unable to be
counted. This is best seen in the data collection table, where little to no
fiddler crabs were counted in early October, as the temperature was too low and
their breeding season had already ended (see Figure 3).
Many
limitations must be taken into consideration in order to fully understand the
scope of this project. During data collection, the weather being different
could affect the amount of crabs counted on a given day; should it be cold,
windy, or rainy out, then the fiddler crabs may be inclined to go into their
burrows, preventing them from being counted. As the breeding season progressed,
more and more vegetation grew, also hindering how easy it was to see and count
the crabs. The crabs were not static during counting sessions, meaning they had
the potential to be counted multiple times, as well as to move away from the
counting area in between counting dates. Lastly, counting could only occur when
there was a new or full moon and during low tide.
Statistical
methods and analysis were conducted to test the hypothesis (see “Mathematical
Concepts in Experiment” for more information on the specific calculations
completed). After the calculations were completed, one is able to draw
conclusions based off of them, and then communicate the results, which is
writing this scientific research paper, completing the final two steps of the
scientific method.
Technology Concepts in Experiment
The
project itself does not include any types of technological concepts; however,
several pieces of technology were used in order to conduct the experiment.
Microsoft Excel allows one to organize all of the different data that has been
collected in a consolidated and user-friendly manner. Keeping accurate data of
the population of the Uca minax
fiddler crab species makes it possible to see the trends in the future
population more easily. This includes the quantitative and qualitative data
taken during each counting session, including but not limited to the amount of
crabs spotted on each side of Spermaceti Cove, the wind speed in miles per hour
and direction, the temperature in degrees Celsius, and any differences in the site
appearance (see Figure 3).
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| Figure 6: The bar graph shows the amount of Uca minax fiddler crabs counted on the North and South sides of Spermaceti Cove on Sandy Hook, New Jersey during the 2017-2018 data collcetion set (Bri Astorino).
Continuing, Excel corroborated several different
statistical calculations that were done by
hand to ensure the accuracy of the
numbers (see Figure 7 for a table of the numbers needed for a
correlation).
Figures 8 and 9), as well as to
take notes about the site and amount of fiddler crabs counted.
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It
is known that fiddler crabs are considered indicator species, meaning that
their population fluctuates easily with changes in their environment (Wenner).
Fiddler crabs burrow into the sediment for protection and to mate in, which
aerates the soil and moves the sediment and nutrients around, maximizing their
availability for other organisms (Subhasish Chatterjee). This, in return,
increases the productivity of their habitat. Fiddler crabs are very sensitive
to contaminants, such as insecticides and fertilizers that come from rain
runoff and river drainage. Should the amounts of these increase, the population
of the fiddler crabs in the area would decrease. Because of the fact that these
contaminants are biomagnified as one moves further up the food chain, meaning
that these pollutants are found in much higher quantities in bigger predators
than in organisms such as primary producers and primary consumers, this form of
pollution affects the entire ecosystem (Wenner). With this being said, in order
to see clearly whether or not the ecosystem is thriving, it is helpful to look
at the stability of the fiddler crab population.
In
order to conduct research regarding the Uca
minax fiddler crab species and their habitat, the coastal wetlands, more
than forty primary sources, including newspaper articles, scientific research
papers, and books, were procured and read. This helped to better understand
statistics and the relationship between the Uca
minax fiddler crab species and their habitat of coastal wetlands,
furthering my knowledge of their ecology.
A blog website, called Blogger, enables the work
completed to be posted for the general public to access. It also enables the
mentors for this experiment to keep up with its progress (see Figure 10 for a
photo of the blog).
Figure 10: Above is a
screenshot of the blog that all of the work completed on this study is posted
on. The link is bafiddlerecology.blogspot.com (Bri Astorino).
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In the near future, GPS
will be used in order to map out the counting sites at Sandy Hook, New Jersey
on Spermaceti Cove.
Mathematical Concepts in Experiment
After
there were no longer fiddler crabs spotted at the cove, all of the data was
compiled into a spreadsheet (see Figure 3) in order to easily see all of the
information collected at once. The table shows all of the data collected during
the 2017-2018 collection year in a neat and organized fashion in order to
encourage easy access to the information.
Then,
the amount of fiddler crabs at the cove was plotted against the counting
session on a line graph (see Figure 4) to see if there were any trends as the
breeding season progressed. All of this was useful when beginning to work on
the statistics and raw data analysis. In order to better see the amount of
fiddler crabs counted each counting session, bar graphs were made in Microsoft
Excel (see Figure 5 for the bar graph of the baseline data and Figure 6 for the
bar graph of the 2017-2018 data), because the line graphs were not as
descriptive as expected.
For
the raw data analysis portion of this project, a correlation between the
temperature of the counting session day against the amount of crabs seen was
calculated (see Figure 7 for a table of the calculations made for this
correlation). The table shows all of the necessary calculations in order to
derive the correlation between the temperature of the counting day in Celsius
against the amount of fiddler crabs counted at both of the counting sites. The
correlation between these two variables was calculated to be .31056; this means
there is a slightly positive correlation between the temperature and the amount
of crabs counted.
Several different types of statistical analysis
were conducted in order to see the spread of data among both years of this
longitudinal study, 2016-2017 and 2017-2018. These statistics include average
number of crabs counted each year, as well as the standard deviation and variance (see Figure 11).
The
higher the variance and standard deviation, the bigger the spread of the data,
meaning there
is a considerably large difference between each counting session
and the amount of crabs spotted on
each side of the cove. The variance of both
years varied greatly between both sides of Spermaceti
Cove. For example, the
variance of the North side of the cove during 2016-2017 is 28,835.8, while
the
variance during 2017-2018 is only 5,586.5, meaning that the amount of crabs
counted in the
latter data set has values much closer together than in the
2016-2017 data set.
On
the other hand, the difference in variance between the South side of the cove
between both data sets is significantly less, with a variance of 48,062.8 in
the 2016-2017 data set and 47,435.1. This means that the amount of crabs
spotted on the South side were relatively close to each other each counting
session. The same is true of the standard deviation between both sides of
Spermaceti Cove, with a bigger difference of standard deviation on the North
side than on the South side in both data sets.
The
summer months of the baseline data, from 2016-2017, were statistically compared
to the summer months of this year’s data, from 2017-2018, by using the formula
[(ED)/N]/sqrt[(ED^2)-(ED)^2/N]/(N-1)N, where ED is the sum of the different
counting sessions, (ED^2) is the sum of the square of the different counting
sessions, and N is the sample size, or amount of counting sessions being taken
into consideration. The months of June, July, and August were compared during
the summers of 2016 and 2017, thus the sample size, or N, was 6. Following the
formula for conducting a t-test, subtract the amount of crabs counted from each
counting session in 2016-2017 from the crabs counted from that same session in
2017-2018, and then total this. Afterwards, square each of my results, and
total this column (see Figure 12 for a table with the necessary numbers for
this comparison). Plug the values into a calculator to receive an answer of
1.943.
N-1 is
the degrees of freedom of a t-test, so there are 5 degrees of freedom in this
specific calculation. Using a t-distribution table, the t-test number with an
alpha level of .05 and 5 degrees of freedom should have been 2.015. Since my
calculated t-test is lower than the t-table value, the null hypothesis, that
there will be no significant change in fiddler crab population as the years
progress, should be accepted as true.
| Figure 12: Above is a table of all of the necessary numbers to conduct a t-test. Here, the value of ED is shown, 1015, and the value of (ED)^2 is also shown, 399203. |
Conclusion
The
scientific method and its six steps sum up the scientific concepts in this
longitudinal study. These steps include defining the question the study seeks
to answer, conducting background information, forming a hypothesis and then
testing it, analyzing the test through the use of statistics, and, finally,
communicating the experiment’s results through a scientific research paper. By
following the method, this study can be easily replicated in the coming years
in order to corroborate or refute the study’s hypothesis that the Uca minax fiddler crab species at
Spermaceti Cove on Sandy Hook, New Jersey will increase as time progresses.
When
it comes to the technology in this longitudinal study, Microsoft Excel was used
in order to create line and bar graphs and tables to display the study’s data
and information in a more user-friendly manner. Excel was also used to
calculate several of the statistical analyses necessary for the experiment.
The
mathematic concepts in this study include all of the statistical analysis in
this project. This includes the data’s average, standard deviation, variance,
correlation, and t-test comparison between the summer months of the 2016-2017
data set and the 2017-2018 data set.
In
total, the collected data from June 2017 to the beginning of October 2017 was
statistically compared to the baseline data collected during the Uca minax breeding season in 2016-2017. This
study will be continued in the following years in order to gain even more data,
thus making the conclusions drawn from said data that much more accurate and
trust-worthy.
Works Cited
Chatterjee, Subhasish, Debasis Mazumdar, and Susanta
Chakraborty. Ecological Role of Fiddler Crabs (Uca Spp.) through Bioturbatory Activities in the Coastal Belt
of East Midnapore, West Bengal,
India (2015): n. pag. Marine Biological Association of India.
Marine
Biological
Association of India, 2017. Web. 5 Nov. 2017.
Coastal Salt Marsh (n.d.): n.
pag. U.S. Fish & Wildlife Service. U.S. Fish & Wildlife
Service, 2017. Web. 5 Nov. 2017.
Coultas, Charles, and Yuch-Ping Hsieh. "Ecology and
Management of Tidal Marshes." Google Books. St. Lucie Press,
1997. Web. 05 Nov. 2017.
Fisher, Bethany.
"Uca Minax." Animal Diversity Web. University of
Michigan, 2017. Web. 05 Nov. 2017.
Hogarth, P.J. "Uca Fiddler Crabs." Encyclopedia
of Life. Encyclopedia of Life, 2017. Web. 05 Nov. 2017.
Rosenberg, Michael S. "Systematics and Taxonomy of Fiddler
Crabs." OUP Academic. Oxford University
Press, 01 July 2001. Web. 05 Nov. 2017.
Wenner, Elizabeth. "Fiddler Crabs." South
Carolina Department of Natural Resources. South Carolina Department of Natural Resources, 2017. Web. 5 Nov.
2017.
"Why Are Wetlands Important?" EPA.
Environmental Protection Agency, 27 Feb. 2017. Web. 05 Nov. 2017.
Woodward, Susan. "Salt Marsh." Biomes of the
World. Radford University, 1997. Web. 05 Nov. 2017.
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