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Community structure and species abundant’s in Antarctic Community’s on Livingston island Byers Peninsula

Bachelor Thesis 2011 46 Pages

Biology - Geobiology

Excerpt

Index

1. Abstract

2. introduction

3. Methods and materials
3.1. Collection method in the field
3.2. site descriptions
3.3 Method used in lab
3.4. Statically analysis used
3.5. Hypothesis

4. Results
4.1. ANOVA on species richness abundant’s and diversity
4.2. MDS analysis
4.3. ANOSIM
4.4. SIMPER Species that define the communities

5. Discussion
5.1. conclusion

6. references

7 appendix

7.1. Arial photographs of ice retreat on Livingston Island
7.2. site pictures of sample sites
7.3. identification recourses used
7.4. amphipod identification list
7.4.1. species list with identification pictures
7.5. presence absence list

1. Abstract

This study was carried out in the lab to identify species that were collected from three sites (Cape Smellie, Past Clark and Nunatak) on Byers peninsula, Livingston Island South Shetland Islands. The study was to investigate whether the length of time a site had been ice free affected community structure. It was found that Cape Smellie had the highest species richness with sixteen more species than Past Clark and twenty-nine more species than Nunatak. Cape Smellie also had the highest of species and was the site that had been ice free for the longest time period +50 years and the Nunatak samples showed a higher diversity than the other two site samples and is the site that has been ice free for less than 10 years. All of the sites sampled were found to have high numbers of Laevilltorina calignosa, Donacidae, Spinonid, Plathyhelminthe and Amphipods, all of which are highly adaptive species to different stress gradients and are all found worldwide in different types of ecosystems. The main findings in this study suggest that glacial retreat could be a possible cause for the increase in species as the data shows that glacial retreat over time co-insides with the increase in species abundant richness and diversity found on the different sites. There is a good possibility that there are different stages of colonisation by different species being seen in this study, and that location of the sites and the different stress gradients, substrata and exposure are possible controlling factors in the type of species and their found at the different sites. All three study sites had ten of the same species present; amphipods two, three, four, six, and nine, Terrebellida, Nephtyidae, Donacidae, Plathyhelminthe one and two and Enchytraeidae, but as likely, the substrata and different stress gradients i.e. wave intensity tolerance to freezing, the dominant species found on the study sites at Byers peninsula also correspond with the majority of studies carried out on other islands in and around the Antarctic region.

2. Introduction

The Antarctic is one of the most inhospitable regions on the planet with glaciations and strong currents and strong westerly winds that are unimpeded by land (Griffiths. 2010). The Antarctic region was thought for many years to have low species diversity (Knox. 1960. Gruzov and Pushkin. 1979), however it has been shown that benthic assemblages that are present have densities and biomasses comparable to the most productive systems elsewhere in the world (Saiz-Salinas, et al. 1998).

Antarctica intertidal zones historically have been thought of as being too inhospitable to support life; however it has been show in a number of studies that this is not the case (Macalister, 1996. Barnes and Hughes. 1988. Saiz Salinas, et al.1997). These communities especially have to be able to adapt and cope with many different stresses and substrata acting upon their environment as Zinsmeister (1976) found when he worked on Seymour Island also situated in the Antarctic Peninsula also see (Selkirk, et al. 1990). Four major environmental gradients have been suggested by (Raffaelli & Hawkins. 1997) One: the vertical unidirectional stress gradient from sea to land. Two: the horizontal gradient of exposure to wave action. Three: the practical size gradient. Four: the Marine-freshwater gradient (Barnes. 1999). It has been shown that exposed and sheltered shores show differences in distribution and composition (Graham. 1997. Defelice and Parrish. 2001. Smith and Simpson. 2002). All these factors have to be considered when looking at coastal environments, but Antarctica and other areas of the world that have glacial and ice formations at different seasonal and time periods will inevitably have to deal with ice retreats and potential for floating ice-bergs to hit the coasts. In both cases it would cause ice scoring, which has the potential to damage and remove species and even damage the habitats (Pugh and Davenport. 1997. Scrosati and Heaven. 2007).

Davenport and Macalister (1996) carried out a study on South Georgia which showed that species living on the higher zones of the shore are more thermally tolerant than those living nearer to the low water zones also see (Newell. 1979). And that it is probably physical tolerances that are the primary controllers of the upper limits of zoneation and that the lower limits of the zones are determined by biotic influences such as competition and predation. A study also looking at reasons for species dispersal on coastal habitats was carried out by Scorosati and Heaven (2007), they achieved this by the creation of a model, the (ESM) environmental stress model. It showed that stress gradients are prominent on vertical gradients because of osmotic stresses and greater temperature fluctuations and that these stresses intensify with elevation due to the increasing aerial exposure due to tides. The study also showed that on a horizontal basis, stress gradients occur due to changes in wave exposure and ice scoring intensity. The model showed that a higher intertidal zone represents a higher end of the stress gradient. The model showed that highly stressful habitats should sustain a low species richness and diversity thus saying that the upper limits of the shore should show less richness and diversity than that of the lower shore. Using the EMS model it is clear that species that inhabit low shore environments will have to injure extreme cold conditions, so the species must have developed some sort of mechanism against the cold to stop their bodily fluids from freezing. Those species that can’t avoid potentially lethal sub zero temperatures and are at risk of dying have formed two basic strategies; one, to avoid freezing by extensive super-cooling (freeze avoidance) and two, the ability to tolerate the formation of ice in their bodily fluids (freezing tolerance). It is thought that intertidal species show more negligible use of super-cooling strategies tolerating formation of ice in their extra cellular fluids (Waller, et al. 2006).

Nutrient intake is also a factor in conditions such as those found in Antarctica. It has been found that there are two major types of feeding strategies in Antarctic intertidal communities, one is suspension feeding and the other is deposit feeding. (Barnes and Hughes. 1988), and (Saiz Salinas, et al.1997), showed that there was segregation between the two feeding groups when they carried out their study on Livingston Island, Deception Island and the Bransfeld Strait. With predominantly only two types of feeding niches and the fragmentation of those two niches this could have a significant effect on species and their biomass that are found within these areas. Saiz-Salinas et al (1997) also showed in their study that shallow water benthos attained a biomass value 6 times greater than the corresponding value from deeper waters. When looking at diversity, two parts of community structure that make up diversity richness and evenness need to be looked at (Scorosati and Heaven. 2007).

These conditions are some of the hardest to establish life in but miraculously life does persist across the Marian and terrestrial environments of Livingston island. Byer’s peninsula is very different to the rest of the island as it is the largest ice free area in the south Shetland islands covering an area of 60.1km2,unlike the majority of the islands which are still covered in a glacial ice. The substrata rock is volcanic and volcaniclastic rock dating from the upper Jurassic to lower Cretaceous marine sedimentary and the site is designated a site of special scientific interest (SSSI), with permits needed to go onto it and to carry out research. The Byers peninsula coast is around 71km in length, the coast is of a rugged irregular topography. Byer’s peninsula is also well known for its broad beaches which are prominent on all three coasts in the North West and south. The largest of these beaches can be found in the south, extending 12 km along the coast and the peninsula has an extensive drainage network due to the snow and ice melt in the summer periods (López-Martínez, et al. 1996).

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Figure 1 map of the Shetland Islands red = Livingston Island and the black =Byers peninsula.

This study was to taxonomically identify and to determine if there were any differences in species community structures from the different sites, and to establish if the different periods of ice retreats have had any affects or influence on the community structure of species within those sites. The main focus in this study was to look at how similar the assemblages are between sites, second was there one assemblage more diverse than the others within and between sites and do the dominant species vary between sites, and has there been a change in assemblage structure due to a disturbance e.g. glacial retreat.

The hypothesis tested for in this study is that there is no difference in species community’s structure, diversity, and richness between the three sites sampled at Byers peninsula Livingston Island.

3. Methods and materials

3.1 Collection method in the field

Species were collected from different sites from Livingston Island in the Byers Peninsula between the 10/01/2009 - 10/02/2009. There were three study sites where specimens were collected from each, varying in different periods of glacial retreat. A 50x50cm2 quadrant was used for initial field work that was carried out by Dr Catherin Waller.

3.2 Site descriptions

There is a number of islands off of main land Antarctica, one of these island chains is the Shetland Island (between latitudes 62°34’35" and 62°40’35" S and longitudes 60°54’14" and 61°13’07" W) .The chain consists of nine main islands with King George Island being the largest of the group and Livingston Island being the second largest situated in the south west of the chain and the island where sampling took place. (Lopez-Martinez et al 1996. Google Earth. 2011).

Temperatures in the area are somewhat constant, rarely exceeding 3 °C (37.4 °F) in summer or falling below −11 °C (12.2 °F) in winter, with ice and glacial formations in the winter months and melting in the summer months (ABM. 2011). The sites were Cape Smellie on the south west part of the island, Past Clark situated on the south east side of the island as is the Nunatak site. The Cape Smellie site has been ice free for 50+ years and is manly a reasonably flat area with boulders and small pebbles with patches of algal cover scattered around the site see appendix 2. The Past Clark site that has been ice free for 10+ years is made up of fine silt with areas of small to medium loose rocks, and the glacier is clearly seen, see appendix 2. The Nunatak site that has been ice free for less than 10 years is mainly flat land with medium to coarse sediment and rock pools surrounded by medium to large rocks see appendix 2. Past Clark and the Nunatak sites are the sites that have had the most recent period of glacial retreat thus having the least time to form species communities. The identification of the species that were brought back from Livingstone Island was carried out in the laboratory in Scarborough England. The hypothesis looked at was to see if the glacial retreat on Byers peninsula has had any

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Figure 2 Cape Smellie, Past Clark and Nunatak sample sites on Livingston Island marked by red arrows. Map obtained from http://www.scar.org/publications/bulletins/150/aspa126/

3.3 Method used in lab

The collected Specimens were preserved in 70% ethanol on arrival to the lab. The specimens were empted into trays taking judicial care not to mix the different sites. The specimens were then separated out by eye into workable categories (morphospecies) i.e. amphipods, worms, shells and so on, once this was achieved the different groups were then thoroughly examined under a CETI dissection microscope. Identification of the different species was achieved by a number of identification resources which can be viewed in appendix 3. The specimens were identified to family not genus, this was due to difficulty in finding information on the taxa due to the lack of in-depth information on species from the Antarctic region. Photos were taken of all species for recording purposes. Amphipods were photographed with accompanying notes. This was done because of the wide variety of specimens found, full species list can be viewed in appendix 4. Specimens were then placed in a specimen pot which was labelled with the site where it was found and filled with 70% ethanol for the purpose of preserving the specimen for future work. For those specimens that had excusably large numbers, the count was achieved by sub-sampling the group, counting them then multiplying the rest.

3.4 Statistical analysis used

The data collected was fed in to windows XL for further statistical analysis. Primer was used for univariate data analysis - diversity analysis of the sites was carried out using a MDS plot for visual representation of the dispersal of the sites then an ANOSIM was run to see any similarities between the sites and finally a SIMER was preformed to get a break down of all the sites and species found there; looking for similarities/dissimilarities within/between sites and then minitab was used to carry out an ANOVA to test H = diversity, S = richness, and N = against the sites. (Fowler. et al. 1998).

The hypotheses for the different statistical tests run are:

Ho/ Diversity, and richness, index showed no significant departure from a normal distribution.

Ho/ There is no significant departure from homogeneity between the variances in Diversity, and richness between the three sites.

Ho/ There is no significant difference in Diversity, and richness between the three study sites.

Ho/ there was no significant difference in similarity of the species between the three different sites.

4. Results

4.1

ANOVA

Diversity, abundance and richness, index both conformed to a normal distribution (Kolmogorov Smirnov test P>0.15).

The variance of the samples from the sites, species, diversity and richness data could be considered equal (i.e. no departure from homogeneity of variances) Diversity (Levene’s test, test statistic = 0.22 P=0.807). (Levene’s test, test statistic = 0.89 P=0.457). Richness (Levene’s test, test statistic = 0.42 P=0.675).

All variance tests were significant and the data conformed to a normal distribution an

ANOVER was used

There was a significant difference in richness between the three study sites (ANOVA, F 2, 6 = 9.69, P= 0.013) mean richness was significantly higher in the species from Cape Smellie (mean = 25.3, s.d. = 5.03) than those from Nunatak (mean =12.0, s.d. = 3.0). There was no significant difference in species richness between Cape Smellie and Past Clark and Nunatak and Past Clark (Tukey P=0.05).

There was no significant difference in Diversity (ANOVA, F2, 6 = 0.08, P=0.926) (ANOVA, F2, 6 = 0.88, P=0.461) between the three study sites.

There was no difference in species richness except for the comparisons between Cape Smellie site and the Nunatak site and there was no statistical difference in species diversity or between the sites.

Figure 3 species richness of the different samples from each site

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Figure 4 species of the different samples from each site

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Figure 5 species diversity of the different samples from each site

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4.2.

Figure 6 illustrates the results of MDS analysis on a Bray-Curtis similarity matrix for Livingston island samples. There are two distinct clusters of points each corresponding to two of the three sites; Past Clark and Cape Smellie. The representation from Nunatak site shows dispersal from each other and one factor from Cape Smellie is fragmented from its group. The stress value was 0.01 indicating that this is a very good representation of the similarity between the samples.

4.3. ANOSIM

There was a significant difference in species community similarity between the three different sites (ANOSIM, Global R = 0.531, P = 1.1%). The Pairwise test was null and void due to lack of replications in sampling.

4.4. SIMPER

Species that define the communities at Cape Smellie Four species accounted for 61.3% of the 12.2% overall similarity between the samples in the Cape Smellie samples. Laevilltorina calignosa had a mean average of 49.3% and contributed to 21.3% of the similarity between the samples, Donacidae was the next most important species (average % abundance = 437.0% contributing 20.12% to the overall similarity of the samples), followed by Spinonid (average % abundance= 15.3% contributing 11.4% to the overall similarity of the samples), and Plathyhelminthe 1

(average % abundance = 22.3% contributing 8.6% to the overall similarity of the samples).

Species that define the communities at Past Clark

Four species accounted for 92.7% of the 42.9% overall similarity between the samples in the Past Clark samples. Amphipod 9 had a mean average of 118.7% abundance and contributed to 37.2% of the similarity between the samples, Amphipod 6 was the next most important species (average % abundance = 58% contributing 23.06% to the overall similarity of the samples), followed by Amphipod 3 Cheirimedon femoratus (average % abundance = 76.33% contributing 17.2% to the overall similarity of the samples), and Kidderia bicolor (average % abundance = 134.7% contributing 15.2% to the overall similarity of the samples).

Species that define the communities at Nunatak

Three species accounted for 77.7% of the 21.66% overall similarity between the samples in the Nunatak samples. Laevilltorina calignosa had a mean average of 28.3% abundance and contributed to 37.1% of the similarity between the samples, Plathyhelminthe 1 was the next most important species (average % abundance = 33% contributing 31.3% to the overall similarity of the samples), followed by Amphipod 3 Cheirimedon femoratus (average % abundance = 9% contributing 9.3% to the overall similarity of the samples).

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Details

Pages
46
Year
2011
ISBN (eBook)
9783656694359
ISBN (Book)
9783656695059
File size
2.6 MB
Language
English
Catalog Number
v276442
Institution / College
University of Hull – Centre for Environmental and Marine Sciences
Grade
Tags
community antarctic community’s livingston byers peninsula

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Title: Community structure and species abundant’s in Antarctic Community’s on Livingston island Byers Peninsula