Invasive Relative Population Population Measurements of Carceinus maenasvs.andHemigrapsus sanguineus at Tthe Drowned Forest at Odiorne Point, Rye, NH
Introduction
Carceinus maenas, or more commonly known as the European green crab, first entered the U.S. during the 1800’s aboard sailing ships traveling from Europe to the Cape Code region (Ricketts and Calvin, 2002Cite). They have since migrated northwards along the coast towards Nova Scotia (Ricketts and Calvin, 2002).C. maenasowes its success to its ability to easily adapt its diet to its surroundings (Jensen, McDonald and Armstrong, 2002cite).C. maenas’s It’s[JG1] early introduction to the U.S. shores have allowed it to overpopulate several areas, beating out competition (Grosholz and Ruiz, 2002). C. maenasis slowly beginning to lose its dominance due to a recently introduced non-native species, —Hemigrapsus sanguineus (Jensen, McDonald and Armstrong, 2002)cite[JG2]).
Similarly, to the European green crab,H. sanguineusis a non-native species that has overrunravished the eastern coast of the U.S (Ledesma and O’Connor, 2001cite). It arrived toin the U.S. in more recent years and has flourished in the colder waters of Maine—beating out native and non-native species (Ledesma and O’Connor, 2001cite[JG3])). . Much likeC. maenas, H. sanguineus has an adaptive diet which allows it to reproduce and populate much faster than its competition (Ledesma and O’Connor, 20016).
The eEastern coast of the U.S.nited States hasve seen a population explosion of non-native species over the past 200+ years (McDermott 2002cite).C.maenashas long dominated the coastlines of the U.S., but is being challenged by a faster reproducing and more adaptable competitor—H. sanguineus (Ledesma and O’Connor, 2001)cite[JG4]).The question arose which species, Is theC. maenas, or the H.sanguineus, is more likely to be dispersed near the shorelinewaterline; and which population would be greater? There may be no correlation between the species distribution and distance from the waterline. I hypothesize, however, that between C. maenas and H. sanguineus, H. sanguineus will have a significantly larger population size as the transect moves closer to the waterline.
. I hypothesize, however, that that is dispersed near the shoreline and the greater population. Due to its earlier introduction to the area, the C. maenas will be more prominent on the watershoreline with a greater number[JG5].
Methods
The study site where the data was collected was located in the Drowned Forest at Odiorne Pointe, Rye, NH during low-tide from 3-6 pm on the South shore when to when. The study site included a 90m stretch of shore which held a small collection of tide pools and rocky terrain.
A 4050 m transects wasere raun perpendicular from the waterline (0m) inland. The area was initially marked by running a 90m transect NE—parallel to the water line. A second transect of 20m was centered and ran perpendicularly to the original transect. 0.585m2 quadrats were laid every 105m of the squared areastarting at the waterline (0m). At Within each quadrat, the number of Carcinus maenas and Hemigrapysus sanguinerus were counted and their relative locations from the waterline were recorded. Location details of the marked area were also recorded, including terrain and exposure to tide. The number of each species, along with distance from waterline, [JG6]Data was were recorded, uploaded into an app, and transferred and represented intotransferred into a Microsoft Excel. Data wasanalyzed by…and separated into three graphs. Both H. sanguineus and C. maenas had separate box charts which showed the average number of each individual specie collected every 5m, as well as the standard deviations for each distance. A linear line was plotted to show the averages for the population. The third graph plotted the two separate charts into a single chart which better showed similarities and differences of the two species...[JG7]scatter plot.
Results:
The data collected concluded that there was no significant difference in population of C. maenas and H. sanguineus at different distances of the transect. The two crabs followed similar population trends as the distance for the transect increased (Figure 1).
Based on Figure 2, H. sanguineus followed a subtle decrease in population as the distance of the transect increased. The population followed a slope of y= -0.0011x + 0.1836. The overall average for H. sanguineus totaled to 0.1667 crabs/transect measurement. Population of the Asian shore crab followed this slope with exception of the 15m mark which showed the highest population of H. sanguineus.
The data collected for C. maenas was almost identical to the data for H. sanguineus. Figure 3 shows the population of C. maenas following a slope of y= -0.0001x + 0.0916 with a total average of 0.0918 crabs/transect measurement. The difference in distance did not produce significant changes in population. C. maenas experienced a small spike in population at the 10m mark—similar to the spike in population of H. sanguineus at 15m.
Discussion and Conclusion:
The original hypothesis for this project stated that there will be a significant difference in average population size between H. sanguineus and C. maenas as the distance of the transect increased. The research conducted did not support our original hypothesis and failed to reject the null hypothesis that there would be no significant differences in population as distance increased.
Based on the data collected, H. sanguineus had its highest average in the mid range of the transect and had an overall average of 0.166 crabs/transect. While C. maenas had its highest average in the lower range of the transect with an overall average of 0.0918 crabs/transect. But the overall averages between the two groups fell extremely close.
Many factors in the data collection could lead to skewed results. Odrione Point is in New England which means weather conditions can drastically change the outcome of data. The spring season can bring a combination of warm and frigid weather patterns. This creates an uncertainty of population survival during this period. The crabs can also prove to be difficult to catch and identify in the region where the research was conducted.
One of the published peer review studies used during this project was one published by McDermott. In this study, McDermott found similar results to what was concluded for this project. It was found that H. sanguineus had the highest averages in the mid to upper regions of the tested area, while C. maenas had the highest averages in the mid to lower regions. McDermott conducted his research in Rhode Island during July and August which may have given him a larger sample size. This study was also carried out for a month opposed to the one collection date for this project—which allowed a better range of results.
Another study used during this project was one done by Kimberly Westgate. The results for this study go against what was concluded during this study. The study was conducted over seven sites. The total number of crabs in the area were marked, as well as their relative location from the shoreline. Out of the 714 total crabs recorded during the study, 559 of them were H. sanguineus (Westgate, 2012). The Asian shore crab was not held to one region of the shoreline—it flourished throughout. Competition between H. sanguineus and C. maenas was non-existent seeing that of the crabs recorded, only 2.24% of them were C. maenas (Westgate, 2012). These numbers were recorded in Massachusetts which may play a role in why the two results are drastically different.
Understanding which areas of the transect had a higher average of crabs allows us to understand how an ecosystem, such as the one at Ordiorne State Park, deals with competition between two competing invasive species. This could be extremely helpful in eliminated an invasive species from an ecosystem and restoring its natural balance of organisms.Unfortunately, the goal of this project was not to identify the factors that influence which specie out-competes the other—but it would be an interesting area to explore. Following up this data collection with one that examines these factors would add another level in support, or against, the hypothesis proposed.
Reference Section
Grosholz, E. and G. Ruiz. 2002. Management Pplan for the European green crab. Aquatic Nuisance Species Task Force 7: 250-315.
Jensen, G.C. and S. McDonald, D.A. Armstrong. 2002. East meets west: interactions between
green crab Carcinus maenas, and native and introduced shore crab Hemigrapsus spp.
Marine Ecology Progress Series 255: 251-262.
Ledesma, M.E. and N.J O’Connor. 2001. Habitat and diet of the non-native crab Hemigrapsus
sanguineus in Southeastern New England. Northeastern Naturalist 8(1): 63-78.
McDermott, J.J. 1998. The western Pacific brachyuran (Hemigrapsus sanguineus: Grapsidae), in its new habitat along the Atlantic coast of the United States: geographic distribution and ecology. ICES J Mar Sci 55(2): 289-298
Ricketts, E.F. and J. Calvin. 2002. Aquatic invasive species: European green crab. Between Pacific Tides 4:117-130.
Westgate, K. 2011. The invasive Asian shore crab, a dominant species on Southeastern Massachusetts beaches: A cause for concern. Bridgewater State University 7(25): 1-5
[JG1]Avoid using “it” and “they” in papers. Instead say what it/they is/are.
[JG2]There is a great article by Jensen and others about Hemigrapsus and Carcinus competition.
[JG3]This is an interesting one. I’ve read a number of articles that greens are still more cold tolerant that’s why they are still dominant further north.
[JG4]Ledesma probably works here.
[JG5]Do you mean number of C. maenas will decrease as distance from the waterline increases? What about H. sanguineus?
[JG6]Repeat of what you just said.
[JG7]Tell me what you did. Averages? Stdev? What were you indep & dep variables? Then tell me the graph and what test you did. This sounds like it’ll be a ttest,, but we can discuss more during stats.
Also, if you end up grouping distances to compare the crabs, you’ll need to put that here.