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2014 Feb 13;92:e98802. doi: 10.1371/journal.pone.0098802.
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Anthropogenic disturbance and biodiversity of marine benthic communities in Antarctica: a regional comparison.
The impacts of two Antarctic stations in different regions, on marine sediment macrofaunal communities were compared: McMurdo, a very large station in the Ross Sea; and Casey, a more typical small station in East Antarctica. Community structure and diversity were compared along a gradient of anthropogenic disturbance from heavily contaminated to uncontaminated locations. We examined some of the inherent problems in comparing data from unrelated studies, such as different sampling methods, spatial and temporal scales of sampling and taxonomic uncertainty. These issues generated specific biases which were taken into account when interpreting patterns. Control sites in the two regions had very different communities but both were dominated by crustaceans. Community responses to anthropogenic disturbance (sediment contamination by metals, oils and sewage) were also different. At McMurdo the proportion of crustaceans decreased in disturbed areas and polychaetes became dominant, whereas at Casey, crustaceans increased in response to disturbance, largely through an increase in amphipods. Despite differing overall community responses there were some common elements. Ostracods, cumaceans and echinoderms were sensitive to disturbance in both regions. Capitellid, dorvelleid and orbiniid polychaetes were indicative of disturbed sites. Amphipods, isopods and tanaids had different responses at each station. Biodiversity and taxonomic distinctness were significantly lower at disturbed locations in both regions. The size of the impact, however, was not related to the level of contamination, with a larger reduction in biodiversity at Casey, the smaller, less polluted station. The impacts of small stations, with low to moderate levels of contamination, can thus be as great as those of large or heavily contaminated stations. Regional broad scale environmental influences may be important in determining the composition of communities and thus their response to disturbance, but there are some generalizations regarding responses which will aid future management of stations.
Figure 1. Location of sampling sites around McMurdo and Casey Stations.
Figure 2. Effect of mesh size on number of species.Species accumulation (species-area) curves comparing 0.5 mm with 1 mm mesh size for replicate cores at 4 locations at Casey Station and for all four combined.
Figure 3. Contamination levels in sediments.Organic carbon content and metal concentrations in marine sediments at Casey and McMurdo Stations. Note different scales for copper (Cu) and cadmium (Cd) in each region. Data for Casey are from  and ; data from McMurdo are from , , . Pb = lead; Zn = zinc; OBB = O’Brien Bay; BB = Brown Bay; WQB = Winter Quarters Bay.
Figure 4. Patterns of biodiversity at Casey and McMurdo.A) Species accumulation curves for Casey and McMurdo regions, and control and disturbed locations within each region. B) Rank/abundance plots for macrofaunal communities from control and disturbed locations at Casey and McMurdo.
Figure 5. Species richness and spatial scales.Species richness at increasing spatial scales in each region. Different symbols represent different locations, blue symbols represent control locations, clear symbols disturbed locations, star symbol represents largest scale in each region (SRH, control and disturbed combined). Numbers in brackets indicate number of replicates in sample. SRP = Point (replicate) species richness, SRS = sample (combined replicates for location) species richness, SRL = large sample species richness, SRH = habitat species richness.
Figure 6. Diversity of major taxonomic groups.Comparison of taxonomic diversity in each region, based on the total number of species found in cores, McMurdo n = 325, Casey n = 160.
Figure 7. Taxonomic distinctness at different spatial scales.Comparison of taxonomic distinctness indices in each region. SR = species richness, Δ = taxonomic diversity (takes account of species abundances), Δ* = taxonomic distinctness, Δ+ = average taxonomic distinctness (based on presence-absence only), which equates to the average taxonomic distinctness between two randomly selected species.
Figure 8. Species abundance and dominance relationships.A & B) The relationship between the number of species and number of individuals in each region; C & D) The relationship between the number of species and dominance in each region. Blue symbols represent control samples, red symbols represent disturbed samples. Type of function used to fit trendline indicated following R2 value.
Figure 9. Macrofaunal community patterns in each region.A & B) MDS ordinations of macrofaunal communities at Casey region species level (A) and McMurdo region species level (B); C) Combined family level MDS ordination of macrofaunal communities at Casey and McMurdo, showing control, intermediate and disturbed groups within each region; D) PCO plot of distances among group centroids in C to show relative effect size. Based on square root transformed abundances and Bray-Curtis similarities. PCO1 = 50.8% of total variation, PCO2 = 27.3% of total variation.
Figure 10. Community composition and effect of disturbance.Relative proportions of polychaetes and crustaceans in infaunal assemblages at Casey and McMurdo, split into control and disturbed locations.
Figure 11. Comparative abundance of key taxa.Comparison of mean abundance per core for major taxonomic groups at Casey and McMurdo. Note Casey data based on 1