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Effects of nutrient enrichment on macroalgal coralligenous assemblages Texto completo
2011
Piazzi, Luigi | Gennaro, Paola | Balata, David
Effects of eutrophication on marine ecosystems have been widely studied, even if both the effects on deep subtidal rocky assemblages and response of different successional stages to nutrients impact are still not clear. In this context, the study aimed to evaluate the effects of nutrient enrichment on Mediterranean macroalgal assemblages associated with coralligenous habitat. A manipulative field experiment was carried out by supplying both mature and early successional stages of assemblages with nutrients. A total of 62 macroalgal species were identified. Multivariate and univariate analyses showed that the structure of both mature and early successional macroalgal assemblages of coralligenous significantly varied between areas treated with nutrients and not treated areas. Moreover, differences were stronger when macroalgal assemblages were in the early successional stage than in the mature one. Results highlighted the role played by nutrients in determining the structure of macroalgal coralligenous assemblages, furthermore suggesting possible synergetic effects with other kinds of disturbances.
Mostrar más [+] Menos [-]Macrobenthic community response to copper in Shelter Island Yacht Basin, San Diego Bay, California Texto completo
2011
Neira, Carlos | Mendoza, Guillermo | Levin, Lisa A. | Zirino, Alberto | Delgadillo-Hinojosa, Francisco | Porrachia, Magali | Deheyn, Dimitri D.
We examined Cu contamination effects on macrobenthic communities and Cu concentration in invertebrates within Shelter Island Yacht Basin, San Diego Bay, California. Results indicate that at some sites, Cu in sediment has exceeded a threshold for “self defense” mechanisms and highlight the potential negative impacts on benthic faunal communities where Cu accumulates and persists in sediments. At sites with elevated Cu levels in sediment, macrobenthic communities were not only less diverse but also their total biomass and body size (individual biomass) were reduced compared to sites with lower Cu. Cu concentration in tissue varied between species and within the same species, reflecting differing abilities to “regulate” their body load. The spatial complexity of Cu effects in a small marina such as SIYB emphasizes that sediment-quality criteria based solely on laboratory experiments should be used with caution, as they do not necessarily reflect the condition at the community and ecosystem levels.
Mostrar más [+] Menos [-]The combined effects of oxygen availability and salinity on physiological responses and scope for growth in the green-lipped mussel Perna viridis Texto completo
2011
Wang, Youji | Hu, Menghong | Wong, Wai Hing | Shin, Paul K.S. | Cheung, Siu Gin
Mussels were maintained for 4weeks under different combinations of dissolved oxygen concentration (1.5, 3.0 and 6.0mgO₂l⁻¹) and salinity (15, 20, 25 and 30) in a 3×4 factorial design experiment. Clearance rate (CR), absorption efficiency (AE), respiration rate (RR) and scope for growth (SFG) decreased with decreasing salinity and dissolved oxygen concentration (DO), while excretion rate (ER) increased with decreasing salinity and increasing DO. The O:N ratio was <10 at salinities of 15 and 20, irrespective of DO levels. SFG was negative in most of the treatments, except for those under 6.0mgO₂l⁻¹ or at a salinity of 30 when DO was lower. The results may help explain the distribution pattern of Perna viridis in Hong Kong waters and provide guidelines for mussel culture site selection.
Mostrar más [+] Menos [-]PAHs distribution in sediments associated with gas hydrate and oil seepage from the Gulf of Mexico Texto completo
2011
Wang, Cuiping | Sun, Hongwen | Chang, Ying | Song, Zhiguang | Qin, Xuebo
Six sediment samples collected from the Gulf of Mexico were analyzed. Total concentrations of the PAHs ranged from 52 to 403ngg⁻¹ dry weight. The lowest PAH concentration without 5–6 rings PAHs appeared in S-1 sample associated with gas hydrate or gas venting. Moreover, S-1 sample had the lowest organic carbon content with 0.85% and highest reduced sulfur level with 1.21% relative to other samples. And, analysis of the sources of PAHs in S-1 sample indicated that both pyrogenic and petrogenic sources, converserly, while S-8, S-10 and S-11 sample suggested petrogenic origin. The distribution of dibenzothiophene, fluorine and dibenzofuran and the maturity parameters of triaromatic steranes suggested that organic matters in S-1 sample were different from that in S-8, S-10 and S-11 sample. This study suggested that organic geochemical data could help in distinguish the characteristic of sediment associated with gas hydrate or with oil seepage.
Mostrar más [+] Menos [-]Biomarker responses in pelagic and benthic fish over 1 year following the Hebei Spirit oil spill (Taean, Korea) Texto completo
2011
Jung, Jee-Hyun | Kim, Moonkoo | Yim, Un Hyuk | Ha, Sung Yong | An, Joon Geon | Won, Jong Ho | Han, Gi Myung | Kim, Nam Sook | Addison, R. F. | Shim, Won Joon
After the Hebei Spirit oil spill incident (7th December, 2007) in the west coast of Korea, contamination of biliary PAH metabolite and hepatic biomarkers in a pelagic and a benthic fish was monitored for 1 year. Concentrations of 16 PAHs and alkylated PAHs in fish muscle were highest (22.0ng/g d.w. for 16 PAHs and 284ng/g d.w. for alkylated PAHs) at 5 days after the spill and then decreased rapidly to background levels at 11months after the spill. Fish from the oiled site had elevated biliary PAH metabolite concentrations immediately after the spill; these declined steadily in both species, but were still above reference site concentrations 2 months after the spill. Oiled-site fish showed hepatic CYP 1A induction whose trend closely followed those of biliary PAH metabolite concentrations, implying continuous exposure to PAHs. Brain acetylcholinesterase activity was not related to oil exposure.
Mostrar más [+] Menos [-]Effects of the construction of Scroby Sands offshore wind farm on the prey base of Little tern Sternula albifrons at its most important UK colony Texto completo
2011
Perrow, Martin R. | Gilroy, James J. | Skeate, Eleanor R. | Tomlinson, Mark L.
Despite widespread interest in the impacts of wind farms upon birds, few researchers have examined the potential for indirect or trophic (predator–prey) effects. Using surface trawls, we monitored prey abundance before and after construction of a 30 turbine offshore wind farm sited close to an internationally important colony of Little terns. Observations confirmed that young-of-the-year clupeids dominated chick diet, which trawl samples suggested were mainly herring. Multivariate modelling indicated a significant reduction in herring abundance from 2004 onwards that could not be explained by environmental factors. Intensely noisy monopile installation during the winter spawning period was suggested to be responsible. Reduced prey abundance corresponded with a significant decline in Little tern foraging success. Unprecedented egg abandonment and lack of chick hatching tentatively suggested a colony-scale response in some years. We urge a precautionary approach to the timing and duration of pile-driving activity supported with long-term targeted monitoring of sensitive receptors.
Mostrar más [+] Menos [-]Why are hatching and emergence success low? Mercury and selenium concentrations in nesting leatherback sea turtles (Dermochelys coriacea) and their young in Florida Texto completo
2011
Perrault, Justin | Wyneken, Jeanette | Thompson, Larry J. | Johnson, Chris | Miller, Debra L.
Leatherback sea turtles (Dermochelys coriacea) have low hatching and emergence success compared to other sea turtle species. Postmortem examinations of hatchlings showed degeneration of heart and skeletal muscle that was similar to that found in other neonates with selenium deficient mothers. Selenium deficiency can result from elevated concentrations of bodily mercury. Ingested mercury is detoxified by the liver through mercury–selenium compound formation. In animals persistently exposed to mercury, the liver’s ability to detoxify this element may decrease, especially if dietary selenium is insufficient. We measured mercury and selenium concentrations in nesting female leatherbacks and their hatchlings from Florida and compared the levels to hatching and emergence success. Both liver selenium and the liver selenium-to-mercury ratio positively correlated with leatherback hatching and emergence success. This study provides the first evidence for the roles of mercury and selenium in explaining low reproductive success in a globally imperiled species, the leatherback sea turtle.
Mostrar más [+] Menos [-]Recovery from the impact of light reduction on the seagrass Amphibolis griffithii, insights for dredging management Texto completo
2011
McMahon, Kathryn | Lavery, Paul S. | Mulligan, Michael
A large-scale, manipulative experiment was conducted to examine the extent and rate of recovery of meadows of the temperate Australian seagrass, Amphibolis griffithii to different light-reduction scenarios typical of dredging operations, and to identify potential indicators of recovery from light reduction stress. Shade cloth was used to mimic different intensities, durations and start times of light reduction, and then was removed to assess the recovery. The meadow could recover from 3months of light stress (5–18% ambient) following 10months re-exposure to ambient light, even when up to 72% of leaf biomass was lost, much faster recovery rates than has previously been observed for large seagrasses. However, when the meadow had been shaded for 6–9months and more than 82% of leaf biomass was lost, no recovery was detected up to 23months after the light stress had ceased, consistent with other studies. Five potential indicators of recovery were recommended.
Mostrar más [+] Menos [-]Stable isotopes as a useful tool for revealing the environmental fate and trophic effect of open-sea-cage fish farm wastes on marine benthic organisms with different feeding guilds Texto completo
2011
Wai, Tak-Cheung | Leung, Kenneth M.Y. | Wu, Rudolf S.S. | Shin, Paul K.S. | Cheung, S.G. | Li, X.Y. | Lee, Joseph H.W.
Environmental fate of fish farm wastes (FFW) released from an open-sea-cage farm at Kat O, Hong Kong was examined by measuring carbon and nitrogen stable isotope (SI) ratios in selected benthic organisms collected along a 2000m transect from the farm. Our results showed that FFW significantly influenced the energy utilization profile of consumers near the fish farm. Although nitrogen enrichment effect on δ¹⁵N was anticipated in biota near the farm, the predicted patterns did not consistently occur in all feeding guilds. Two species of suspension-feeders, which relied on naturally δ¹⁵N-depleted sources, were δ¹⁵N-enriched near the fish farm. In contrast, both species of benthic grazer and deposit-feeder, which relied on naturally δ¹⁵N-enriched algal sources, were δ¹⁵N-depleted under the influence of FFW. The SI signatures of biota can, therefore, serve as feasible biomarkers for FFW discharges only when the trophic structure of the receiving environment is fully elucidated.
Mostrar más [+] Menos [-]A 400-year record of black carbon flux in the Xisha archipelago, South China Sea and its implication Texto completo
2011
Liu, Xiaodong | Xu, Liqiang | Sun, Liguang | Liu, Fei | Wang, Yuhong | Yan, Hong | Liu, Yi | Luo, Yuhan | Huang, Jing
We reconstructed the first long-term (∼400years) records of black carbon (BC) deposition flux from three ornithogenic sediment profiles, which were collected from three remote, isolated islets of the Xisha archipelago, South China Sea. The significant correlations between black carbon, organic matter and excess ²¹⁰Pb suggested that black carbon was mainly derived from atmospheric deposition, and further enriched by plant-derived organic matter in sediments. During the past 400years, the BC flux remained relatively low before the onset of 20th century; it started to increase from approximately 1900 AD, and peaked around the 1970s. In the recent 30years, the BC flux seemed to display decreasing trend, very likely due to the change of energy structure and development of pollution control techniques. In comparison with marginal sea regions that are greatly impacted by anthropogenic activities, these pristine Xisha islands were not significantly influenced by black carbon of anthropogenic origin.
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