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Результаты 461-470 из 1,908
Physical dynamics controlling variability in nearshore fecal pollution: Fecal indicator bacteria as passive particles
2013
Rippy, M.A. | Franks, P.J.S. | Feddersen, F. | Guza, R.T. | Moore, D.F.
We present results from a 5-h field program (HB06) that took place at California’s Huntington State Beach. We assessed the importance of physical dynamics in controlling fecal indicator bacteria (FIB) concentrations during HB06 using an individual based model including alongshore advection and cross-shore variable horizontal diffusion. The model was parameterized with physical (waves and currents) and bacterial (Escherichia coli and Enterococcus) observations made during HB06. The model captured surfzone FIB dynamics well (average surfzone model skill: 0.84 {E. coli} and 0.52 {Enterococcus}), but fell short of capturing offshore FIB dynamics. Our analyses support the hypothesis that surfzone FIB variability during HB06 was a consequence of southward advection and diffusion of a patch of FIB originating north of the study area. Offshore FIB may have originated from a different, southern, source. Mortality may account for some of the offshore variability not explained by the physical model.
Показать больше [+] Меньше [-]Fine scale distribution constrains cadmium accumulation rates in two geographical groups of Franciscana dolphin from Argentina
2013
Polizzi, P.S. | Chiodi Boudet, L.N. | Romero, M.B. | Denuncio, P.E. | Rodríguez, D.H. | Gerpe, M.S.
Franciscana dolphin is an endemic cetacean in the southwestern Atlantic Ocean and is classified as Vulnerable A3d by the International Union for Conservation of Nature. Cadmium accumulation was assessed in two geographic groups from Argentina; one inhabits the La Plata River estuary, a high anthropogenic impacted environment, and the other is distributed in marine coastal, with negligible pollution. Despite the environment, marine dolphins showed an increase of renal Cd concentrations since trophic independence; while in estuarine dolphins was from 6years. This is associated with dietary Argentine anchovy which was absent in the diet of estuarine dolphins, being a trophic vector of cadmium in shelf waters of Argentina. Cluster analysis also showed high levels of cd in association with the presence of anchovy in the stomach. The difference in the fine scale distribution of species influences dietary exposure to Cd and, along with other data, indicates two stocks in Argentina.
Показать больше [+] Меньше [-]Impact of elevated levels of CO2 on animal mediated ecosystem function: The modification of sediment nutrient fluxes by burrowing urchins
2013
Widdicombe, S. | Beesley, A. | Berge, J.A. | Dashfield, S.L. | McNeill, C.L. | Needham, H.R. | Øxnevad, S.
A mesocosm experiment was conducted to quantify the relationships between the presence and body size of two burrowing heart urchins (Brissopsis lyrifera and Echinocardium cordatum) and rates of sediment nutrient flux. Furthermore, the impact of seawater acidification on these relationships was determined during this 40-day exposure experiment. Using carbon dioxide (CO2) gas, seawater was acidified to pHNBS 7.6, 7.2 or 6.8. Control treatments were maintained in natural seawater (pH≈8.0). Under normocapnic conditions, burrowing urchins were seen to reduce the sediment uptake of nitrite or nitrate whilst enhancing the release of silicate and phosphate. In acidified (hypercapnic) treatments, the biological control of biogeochemical cycles by urchins was significantly affected, probably through the combined impacts of high CO2 on nitrifying bacteria, benthic algae and urchin behaviour. This study highlights the importance of considering biological interactions when predicting the consequences of seawater acidification on ecosystem function.
Показать больше [+] Меньше [-]Consequences of a simulated rapid ocean acidification event for benthic ecosystem processes and functions
2013
Murray, Fiona | Widdicombe, Stephen | McNeill, C Louise | Solan, Martin
Whilst the biological consequences of long-term, gradual changes in acidity associated with the oceanic uptake of atmospheric carbon dioxide (CO2) are increasingly studied, the potential effects of rapid acidification associated with a failure of sub-seabed carbon storage infrastructure have received less attention. This study investigates the effects of severe short-term (8days) exposure to acidified seawater on infaunal mediation of ecosystem processes (bioirrigation and sediment particle redistribution) and functioning (nutrient concentrations). Following acidification, individuals of Amphiura filiformis exhibited emergent behaviour typical of a stress response, which resulted in altered bioturbation, but limited changes in nutrient cycling. Under acidified conditions, A. filiformis moved to shallower depths within the sediment and the variability in occupancy depth reduced considerably. This study indicated that rapid acidification events may not be lethal to benthic invertebrates, but may result in behavioural changes that could have longer-term implications for species survival, ecosystem structure and functioning.
Показать больше [+] Меньше [-]As main meal for sperm whales: Plastics debris
2013
de Stephanis, Renaud | Giménez, Joan | Carpinelli, Eva | Gutierrez-Exposito, Carlos | Cañadas, Ana
Marine debris has been found in marine animals since the early 20th century, but little is known about the impacts of the ingestion of debris in large marine mammals. In this study we describe a case of mortality of a sperm whale related to the ingestion of large amounts of marine debris in the Mediterranean Sea (4th published case worldwide to our knowledge), and discuss it within the context of the spatial distribution of the species and the presence of anthropogenic activities in the area that could be the source of the plastic debris found inside the sperm whale. The spatial distribution modelled for the species in the region shows that these animals can be seen in two distinct areas: near the waters of Almería, Granada and Murcia and in waters near the Strait of Gibraltar. The results shows how these animals feed in waters near an area completely flooded by the greenhouse industry, making them vulnerable to its waste products if adequate treatment of this industry’s debris is not in place. Most types of these plastic materials have been found in the individual examined and cause of death was presumed to be gastric rupture following impaction with debris, which added to a previous problem of starvation. The problem of plastics arising from greenhouse agriculture should have a relevant section in the conservation plans and should be a recommendation from ACCOBAMS due to these plastics’ and sperm whales’ high mobility in the Mediterranean Sea.
Показать больше [+] Меньше [-]Bioaccumulation of organochlorines in relation to the life history in the white-spotted charr Salvelinus leucomaenis
2013
Arai, Takaomi
The bioaccumulation of organochlorines (OCs) in the muscle tissue of sea-run (anadromous) and freshwater-resident (fluvial) white-spotted charr (Salvelinus leucomaenis) was determined to assess the ecological risk related to intraspecies variations in diadromous fish life history as they migrate between sea and freshwater. Generally, there were significant correlations between the accumulation of OCs such as DDTs, HCB, HCHs and CHLs. In addition, various biological characteristics, such as total length (TL), body weight (BW) and age, and number of downstream migration (NDM) were correlated. A positive correlation occurred between the lipid content and the OC concentrations. Close linear relationships were found between TL, BW and NDM and the lipid content. Although they are both the same species, the OCs concentrations in the anadromous fish were significantly higher than those in the fluvial individuals. These results suggest that anadromous S. leucomaenis have a higher ecological risk for OCs exposure than the fluvial fish.
Показать больше [+] Меньше [-]A baseline study of levels of mercury, arsenic, cadmium and lead in Northeast Arctic cod (Gadus morhua) from different parts of the Barents Sea
2013
Julshamn, Kaare | Duinker, Arne | Nilsen, Bente M. | Frantzen, Sylvia | Maage, Amund | Valdersnes, Stig | Nedreaas, Kjell
This study is one of several baseline studies that will provide basic and reliable information about the content of undesirable substances in important species of fish caught in Norwegian waters. Concentrations of metals in the muscle and liver of more than 800 Northeast Arctic cod caught at 32 sites in the Barents Sea are reported. The highest concentration of both mercury in the muscle and cadmium in the liver was found in cod caught in the western part of the Barents Sea, while the highest concentration of total arsenic was found in cod from the eastern part. The arsenic concentrations varied greatly among individual fish, ranging from 0.3 to 170mgkg−1 wet weight in the muscle. Such high levels of total arsenic have never previously been reported in any fish, and the primary factor for these high concentrations is likely to be the shrimp in the cod diet.
Показать больше [+] Меньше [-]Broad-scale patterns of tissue-δ15N and tissue-N indices in frondose Ulva spp.; Developing a national baseline indicator of nitrogen-loading for coastal New Zealand
2013
Barr, Neill G. | Dudley, Bruce D. | Rogers, Karyne M. | Cornelisen, Christopher D.
A survey of tissue-δ15N and tissue-N values in the green macroalga, Ulva, was conducted around the coast of New Zealand to determine if these indices could be used as indicators of anthropogenic nutrient loading in coastal waters. In addition, data from four case studies showed temporal and spatial responses of tissue-δ15N and tissue-N in Ulva to significant terrestrial nutrient inputs. Tissue-δ15N in Ulva from ‘natural’ exposed coastal sites showed a relatively narrow baseline range of values (6.6±0.1–8.8±0.1‰) in both summer and winter that was consistent throughout New Zealand. Departures in Ulva tissue-δ15N ratios outside this range, particularly when coupled with high (>3.1%) tissue-N values, indicate significant contributions of terrestrially-derived nitrogen to coastal seawater. We note that tissue-N content is also affected by exposure, light and season; however provided such factors are taken into account Ulva can be a cost-effective indicator of relative changes in both source and amount of nitrogen-loading.
Показать больше [+] Меньше [-]Bloom of Cochlodinium polykrikoides (Dinophyceae: Gymnodiniales) in Bahía de La Paz, Gulf of California
2013
Gárate Lizárraga, Ismael
As part of a continuing toxic microalgae monitoring program, phytoplankton samples were collected on 16–17 August 2012 at several sampling sites in the southern part of the Bahía de La Paz. A bloom of the dinoflagellate Cochlodinium polykrikoides was detected. Abundance of C. polykrikoides ranged from 73 to 276×103cellsL−1 on the first day to 980–1425×103cellsL−1 on the second day. Study of live specimens showed great variation in cell size and form, mainly as single cells or chains of two cells. Live cells were 30–47μm long and 20–35μm wide (n=30). Seawater temperature during the bloom was 29–30°C. Low densities of Cochlodinium convolutum, Cochlodinium helicoides, and Cochlodinium shuettii were also found in the samples of the bloom event. These high densities of C. polykrikoides did not lead to fish die-offs in the bay.
Показать больше [+] Меньше [-]DNA strand breaks (comet assay) in blood lymphocytes from wild bottlenose dolphins
2013
Lee, Richard F. | Bulski, Karrie | Adams, Jeffrey D. | Peden-Adams, Margie | Bossart, Gregory D. | King, Lydia | Fair, Patricia A.
The comet assay was carried out on blood lymphocytes from a large number of wild dolphins (71 from Indian River Lagoon, FL, USA; 51 from Charleston Harbor, SC, USA) and provides a baseline study of DNA strand breaks in wild dolphin populations. There were no significant differences in the comet assay (%DNAintail) results between the different age and sex categories. Significant difference in DNA strand breaks were found between Charleston Harbor dolphins (median – 17.4%DNAintail) and Indian River Lagoon dolphins (median – 14.0%DNAintail). A strong correlation found between T-cell proliferation and DNA strand breaks in dolphin lymphocytes suggests that dolphins with a high numbers of DNA strand breaks have a decreased ability to respond to infection. Higher concentrations of genotoxic agents in Charleston Harbor compared with Indian River lagoon may have been one of the causes of higher DNA strand breaks in these dolphins.
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