Browsing by Subject "Pollution"

Now showing 1 - 6 of 6
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    Aspects of benthic decapod diversity and distribution from rocky nearshore habitat at geographically widely dispersed sites
    (Public Library of Science, 2011) Pohle, Gerhard; Iken, Katrin; Clarke, K Robert; Trott, Thomas; Konar, Brenda; Cruz-Motta, Juan José; Wong, Melisa; Benedetti-Cecchi, Lisandro; Mead, Angela; Miloslavich, Patricia
    Relationships of diversity, distribution and abundance of benthic decapods in intertidal and shallow subtidal waters to 10 m depth are explored based on data obtained using a standardized protocol of globally-distributed samples. Results indicate that decapod species richness overall is low within the nearshore, typically ranging from one to six taxa per site (mean = 4.5). Regionally the Gulf of Alaska decapod crustacean community structure was distinguishable by depth, multivariate analysis indicating increasing change with depth, where assemblages of the high and mid tide, low tide and 1 m, and 5 and 10 m strata formed three distinct groups. Univariate analysis showed species richness increasing from the high intertidal zone to 1 m subtidally, with distinct depth preferences among the 23 species. A similar depth trend but with peak richness at 5 m was observed when all global data were combined. Analysis of latitudinal trends, confined by data limitations, was equivocal on a global scale. While significant latitudinal differences existed in community structure among ecoregions, a semi-linear trend in changing community structure from the Arctic to lower latitudes did not hold when including tropical results. Among boreal regions the Canadian Atlantic was relatively species poor compared to the Gulf of Alaska, whereas the Caribbean and Sea of Japan appeared to be species hot spots. While species poor, samples from the Canadian Atlantic were the most diverse at the higher infraordinal level. Linking 11 environmental variables available for all sites to the best fit family-based biotic pattern showed a significant relationship, with the single best explanatory variable being the level of organic pollution and the best combination overall being organic pollution and primary productivity. While data limitations restrict conclusions in a global context, results are seen as a first-cut contribution useful in generating discussion and more in-depth work in the still poorly understood field of biodiversity distribution.
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    Large-scale spatial distribution patterns of echinoderms in nearshore rocky habitats
    (Public Library of Science, 2010) Iken, Katrin; Konar, Brenda; Benedetti-Cecchi, Lisandro; Cruz-Motta, Juan José; Knowlton, Ann; Pohle, Gerhard; Mead, Angela; Miloslavich, Patricia; Wong, Melisa; Trott, Thomas
    This study examined echinoderm assemblages from nearshore rocky habitats for large-scale distribution patterns with specific emphasis on identifying latitudinal trends and large regional hotspots. Echinoderms were sampled from 76 globally-distributed sites within 12 ecoregions, following the standardized sampling protocol of the Census of Marine Life NaGISA project ( www.nagisa.coml.org ). Sample-based species richness was overall low (<1-5 species per site), with a total of 32 asteroid, 18 echinoid, 21 ophiuroid, and 15 holothuroid species. Abundance and species richness in intertidal assemblages sampled with visual methods (organisms >2 cm in 1 m 2 quadrats) was highest in the Caribbean ecoregions and echinoids dominated these assemblages with an average of 5 ind m −2 . In contrast, intertidal echinoderm assemblages collected from clearings of 0.0625 m 2 quadrats had the highest abundance and richness in the Northeast Pacific ecoregions where asteroids and holothurians dominated with an average of 14 ind 0.0625 m −2 . Distinct latitudinal trends existed for abundance and richness in intertidal assemblages with declines from peaks at high northern latitudes. No latitudinal trends were found for subtidal echinoderm assemblages with either sampling technique. Latitudinal gradients appear to be superseded by regional diversity hotspots. In these hotspots echinoderm assemblages may be driven by local and regional processes, such as overall productivity and evolutionary history. We also tested a set of 14 environmental variables (six natural and eight anthropogenic) as potential drivers of echinoderm assemblages by ecoregions. The natural variables of salinity, sea-surface temperature, chlorophyll a , and primary productivity were strongly correlated with echinoderm assemblages; the anthropogenic variables of inorganic pollution and nutrient contamination also contributed to correlations. Our results indicate that nearshore echinoderm assemblages appear to be shaped by a network of environmental and ecological processes, and by the differing responses of various echinoderm taxa, making generalizations about the patterns of nearshore rocky habitat echinoderm assemblages difficult.
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    Lichens as air pollution assays on the Western Cape coast
    (1994) Muofhe, Mmboneni Leonard; Bond, William J
    A pollution survey was done in Milnerton industrial area along three transects, the coastal road, the R27 road, and the N7 road. In this project lichens were used as pollution monitors and their availability, abundance and percentage cover were used to estimate the level of pollution. Lichen specimens were collected from St. James, which is far from the pollution source and put in the vicinity of the Caltex oil refinery for four month after which they were analysed for their fluorescence and chlorophyll content. In all transects, lichen species richness and percentage cover increased with distance from the oil refinery, suggesting that indeed lichens are sensitive to pollution and are therefore good air pollution bio-monitors. The fruticose growth forms especially Teloschistes and Usnea were shown in this study to be the most sensitive to pollution because none of them was recorded close to the oil refinery. Photosynthetic pigment analyses revealed that Parmelia and Xanthoria are affected differently by pollution. Parmelia showed chlorophyll a and b injury under high pollution conditions while Xanthoria showed high carotenoid injury. The results of this study indicate that the atmosphere in the Milnerton industrial area is heavily polluted, with the Caltex oil refinery being the main pollution source.
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    Plastic pollution in the world's oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea
    (Public Library of Science, 2014) Eriksen, Marcus; Lebreton, Laurent C M; Carson, Henry S; Thiel, Martin; Moore, Charles J; Borerro, Jose C; Galgani, Francois; Ryan, Peter G; Reisser, Julia
    Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world's oceans from 24 expeditions (2007-2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N = 680) and visual survey transects of large plastic debris (N = 891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic <4.75 mm and meso- and macroplastic >4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove <4.75 mm plastic particles from the ocean surface.
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    Seabirds as monitors of marine plastic pollution
    (2025) Perold, Vonica; Ryan, Peter
    Small buoyant plastic items are one of the most pervasive and abundant marine pollutants. They pose significant environmental impacts, including threatening the health of marine life through plastic ingestion, necessitating efforts to reduce plastic leakage into the sea. To evaluate the effectiveness of mitigation strategies, it is essential to understand trends in marine plastic densities, types, and sources, which requires a reliable baseline for repeated assessments. While sea-surface net trawls are commonly used to monitor trends in small floating plastics at sea, they face several challenges. Seabirds, particularly petrels and albatrosses (order Procellariiformes), offer a practical alternative to net sampling as they often ingest and retain buoyant plastics encountered while foraging at sea, making them valuable indicators of this type of plastic pollution. However, few studies have thoroughly tested their utility. Larger species, such as albatrosses and giant petrels, typically ingest macroplastics items like bags, bottle lids, and fishery-related debris, which can often be traced back to specific sources. In contrast, smaller petrels, including storm petrels, prions, and shearwaters, tend to ingest smaller items like industrial pellets and fragments of larger plastic objects, whose sources are more challenging to identify. Due to their high propensity for ingesting plastics and their tendency to consume larger volumes, these smaller petrels may be particularly well- suited for monitoring ingested plastic loads over time. In Chapter 2, I assess trends in litter items collected at the nests of albatrosses and giant petrels breeding on Marion Island in the southwestern Indian Ocean, from 1996 to 2018. Temporal variation in litter composition and amounts were compared to data on Patagonian toothfish Dissostichus eleginoides fishing intensity in the area. Fishery-related litter abundance peaked during industry's height, declining in the following two decades. Other litter items increased over the last decade, when the most frequently recorded identifiable litter items were drink bottle lids from Indonesia. Long-distance drift of buoyant plastic items from Southeast Asia, mainly Indonesia, is a major source of litter to the western Indian Ocean. In Chapter 3, I assess the use of an indirect method to sample plastics ingested by seabirds by examining regurgitated Brown Skua Catharacta antarctica (Stercorariidae) pellets containing prey remains of petrels at Inaccessible Island in the central South Atlantic Ocean. I compare the size of plastics in skua pellets to those collected directly from seabird carcasses, to assess the validity of this method. I also compare the composition of plastics ingested within each seabird taxon to small buoyant plastics sampled with a neuston net, to understand how the ingested plastic compares with that found in the environment. I found that as a community, petrels reflected the composition of small buoyant plastics at sea, providing support for their use as biomonitors of marine plastic pollution. In Chapter 4, I assess how plastic loads in four petrels have changed from 1987 to 2018 in roughly decadal time periods and years. More than 3 700 regurgitated Brown Skua pellets, each containing the remains of a single petrel, indicated fluctuations in plastic loads between periods and years, but no overall clear trend was evident in any species. The number and proportions of industrial pellets among ingested plastics decreased over the study period, indicating that industry initiatives to reduce pellet leakage have been at least partly successful. In Chapter 5, I assess whether the size, mass, and polymer types of ingested plastic items have changed over the study period (1987 – 2018) to help interpret the results from Chapter 4. I found little change in the size and mass of ingested plastics since the 1980s. The ratio of polypropylene to polyethylene has increased consistently among hard fragments of user items over time. Overall, the limited change in plastic characteristics is consistent with the absence of clear trends in plastic loads over time (Chapter 4). In Chapter 6, which also serves as my synthesis, I investigate whether plastics sampled on beaches along the southern Cape coastline of South Africa from 1984 to 2023 exhibit the same trends in composition as small buoyant plastics ingested by petrels from 1987 to 2018. The findings show minimal changes in beached hard fragment sizes, with a recent increase in industrial pellet mass due to two major spills at sea off South Africa in 2017 and 2020. Polymer ratios in hard fragments mirrored those ingested by seabirds in the South Atlantic, indicating common influencing variables. More data are needed to understand the increase in the ratios of polypropylene to polyethylene over time, and how this may influence retention rates of plastics on the sea surface. In summary, this thesis demonstrates that sampling plastics ingested by seabirds provides a comprehensive assessment of marine litter composition and sources. Seabirds offer valuable insights into temporal trends in plastic loads and characteristics which align with variations observed in beached plastics. The lack of clear patterns in plastic loads over time suggests that initiatives to reduce the influx of plastics, and remove existing litter, may be preventing a rapid increase in the density of floating plastics at sea, despite the ongoing increase in global plastic production. However, the possible egestion of plastics by seabirds while out at sea, may also account for the lack of clear trends. More empirical data are needed to assess this, and how turnover rates of floating plastics will change under different plastic emission scenarios, to help interpret patterns in the loads and sizes of plastics in the marine environment. These insights are crucial for assessing the efficacy of mitigation strategies to reduce plastic waste leakage into the marine environment.
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    Spatial relationships between polychaete assemblages and environmental variables over broad geographical scales
    (Public Library of Science, 2010) Benedetti-Cecchi, Lisandro; Iken, Katrin; Konar, Brenda; Cruz-Motta, Juan; Knowlton, Ann; Pohle, Gerhard; Castelli, Alberto; Tamburello, Laura; Mead, Angela; Trott, Tom
    This study examined spatial relationships between rocky shore polychaete assemblages and environmental variables over broad geographical scales, using a database compiled within the Census of Marine Life NaGISA (Natural Geography In Shore Areas) research program. The database consisted of abundance measures of polychaetes classified at the genus and family levels for 74 and 93 sites, respectively, from nine geographic regions. We tested the general hypothesis that the set of environmental variables emerging as potentially important drivers of variation in polychaete assemblages depend on the spatial scale considered. Through Moran's eigenvector maps we indentified three submodels reflecting spatial relationships among sampling sites at intercontinental (>10000 km), continental (1000-5000 km) and regional (20-500 km) scales. Using redundancy analysis we found that most environmental variables contributed to explain a large and significant proportion of variation of the intercontinental submodel both for genera and families (54% and 53%, respectively). A subset of these variables, organic pollution, inorganic pollution, primary productivity and nutrient contamination was also significantly related to spatial variation at the continental scale, explaining 25% and 32% of the variance at the genus and family levels, respectively. These variables should therefore be preferably considered when forecasting large-scale spatial patterns of polychaete assemblages in relation to ongoing or predicted changes in environmental conditions. None of the variables considered in this study were significantly related to the regional submodel.