Mercury in lake sediments of the Precambrian Shield near Huntsville, Ontario, Canada   总被引：10，自引：0，他引：10  

P. E. Rasmussen  D. J. Villard  H. D. Gardner  J. A. C. Fortescue  S. L. Schiff  W. W. Shilts 《Environmental Geology》1998,33(2-3):170-182

 Long sediment cores (>1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the whole of Canada. Strong areal correlations between Hg concentrations and LOI (r ² =0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (>20 cm) was found to mirror the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r ² =0.85;n=25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in smallmouth bass normalized to 35 cm length (R ² =0.63;n=15 lakes). The latter relationship suggests that smallmouth bass and lake sediment indicators provide mutually supportive information regarding Hg loading to the lacustrine environment from geological sources in the watershed system. Received: 31 October 1996 · Accepted: 27 May 1997  相似文献   

Retardation of Fin Regeneration in Freshwater Fish Oreochromis mossambicusby Zinc     

Yogendra Verma 《洁净——土壤、空气、水》2004,32(6):429-433

Regeneration of partially amputated caudal fin was studied in freshwater fish Oreochromis mossambicus exposed to sublethal concentrations of zinc (5.0 mg L^—1 and 10.0 mg L^—1) under ambient laboratory conditions over a period of 20 days. Caudal fin regeneration was measured on 5th, 10th, 15th and 20th day of exposure and after amputation. Significant ( p < 0.05) retardation in fin regeneration was observed on day 5th and 10th in fish exposed to the nominal concentration of 5.0 mg L^—1 Zn, while retardation was found highly significant ( p < 0.01) at all the observations in 10.0 mg L^—1. The maximum inhibition in caudal fin regeneration (20.8 % and 24.3 %) was found during the initial observation at both of the concentrations (5.0 mg L^—1 and 10.0 mg L^—1) of zinc exposure. Later on the regeneration rate was almost as good as in the control group. Thus in this study fin regeneration was significantly inhibited at all time points following Zn exposure as a detrimental effect of Zn to fish. This study demonstrates that fish caudal fin regeneration is a simple assay, sensitive and easy to perform, and can serve as a model to determine the toxicity of pollutants in aquatic environment.  相似文献   

Fish in the littoral zone: ecology, threats and management     

Ian J. Winfield   《Limnologica》2004,34(1-2):124

The importance of the littoral zone of lakes to a diversity of fish species has been appreciated for many centuries, although the complexity and heterogeneity of this habitat have resulted in a poorer understanding of local fish ecology compared with that achieved for typically much larger but simpler offshore habitats. Lake fish species may occupy the littoral zone permanently or visit it on diel, seasonal or ontogenetic timescales in response to a range of intrinsic and extrinsic factors. The purposes of such occupations include feeding, refuge from predation and, most importantly for many species, reproduction. The primary environmental threats to fish in the littoral zone arise from eutrophication, which may directly or indirectly alter feeding conditions through the loss of macrophytes, from increases or decreases in water level variations and from siltation rates, both of which may interfere with spawning or egg incubation, and from the introduction of alien species, many of which preferentially colonise the littoral zone where they may act as predators, competitors or environmental degraders. The management of these threats is best accomplished through general lake management measures such as the control of nutrient levels, but some actions specific to the littoral zone or its fish populations are also feasible. These include the replacement of lost or damaged spawning substrata, the active management of water levels at appropriate times of year, and, at least potentially, the deployment of artificial structures to provide appropriate physical habitat for adult fish.  相似文献   

Feeding habits of Solea senegalensis in earthen ponds in Sado estuary     

Maria Ana Castelo Branco  Marco A. Arruda  Sofia Gamito   《Journal of Sea Research》2010,64(4):446-450

The senegale sole, Solea senegalensis Kaup, 1858, is a commercially valuable fish and it is beginning to be cultured in a semi-intensive way in fish farms in southern European countries. The present study was initiated to investigate the diet of S. senegalensis under semi-extensive conditions. The feeding habits of sole were studied in two earthen ponds of a fish farm in the Sado estuary. In one earthen pond, artificial fish ration was given. S. senegalensis feeds on few prey items, its diet is mainly composed of insect larvae (Chironomus salinarus) and polychaeta (Hediste diversicolor). The diet composition of this species suggests feeding specialization, by consuming mainly annelids and insect larvae and by avoiding other items, extremely abundant in the environment, such as gastropods. In the water reservoir where ration was given, some fish consumed simultaneously benthic organism together with ration. However, benthic organisms seem to be the most important component of S. senegalensis diet.  相似文献   

Differences in causal reasoning about resource dynamics and consequences for the participatory debate on North Sea fisheries     

M.C. Verweij  W.L.T. van Densen 《Marine Policy》2010

Fishermen, scientists, policy makers, and staff of environmental NGOs (ENGOs) have significantly different understandings of the processes that determine developments in fish stocks. These perception differences hinder the participatory debate on why fish stocks change and which management measures are effective. In this study, differences in causal reasoning about processes between fishermen, policy makers, ENGO-staff, and scientists were examined, regarding four case studies within the management of the fishery on North Sea plaice. First, it appeared that all parties, besides scientists, had difficulty reasoning about long-term effects because of comprehension problems with stock dynamics, and because of short-term economical interests. Second, there were differences in how parties deal with natural variation and interconnectedness of natural and anthropogenic influences. Stock assessment scientists work with single-species models, reducing complexity by using assumptions that rule out variation, in order to inform policy makers about the effect of one isolated management measure. Fishermen on the other hand, relying on information from their daily lives at sea, emphasize complexity and interconnectedness, and the impact of the ever-changing and unpredictable nature. ENGO-staff appeared reluctant to reason about single species and broaden the debate to the ecosystem-level, while emphasizing the effect of man. As a consequence of the diverging perceptions, much time in multi-stakeholder settings is lost on repetitive discussions, mainly on the relative importance of 'nature' versus 'man'. No wonder that policy makers feel lost, and experience processes as very complex. Concluding, to handle these perception differences, there is need for a directive process coordinator, and a more creative informative role for fisheries scientists. Together with all participants, they should map all expectancies and lines of reasoning at the beginning of the debate. This scheme can be relied on during subsequent meetings, in which perceptions can adequately be positioned.  相似文献   

250 years of sardine and anchovy scale deposition record in Mejillones Bay, northern Chile   总被引：2，自引：1，他引：1  

Jorge Valds  Luc Ortlieb  Dimitri Gutierrez  Luis Marinovic  Gabriel Vargas  Abdel Sifeddine 《Progress in Oceanography》2008,79(2-4):198

Marine oxygen-deficient environments with high sedimentation rates and high primary productivity can provide relevant information regarding variations of ocean–climatic conditions in the past. In the Humboldt current ecosystem, which now hosts huge populations of pelagic fishes (mainly anchovy and sardine), fish scale abundance in the sedimentary record may be useful indicators of environmental change. Here we assess such a proxy record in a 42 cm-long sedimentary core collected from 80 m in Mejillones Bay (23°S, northern Chile). We also analyse fish remains in surface sediment sampled along a bathymetric transect (from 10 to 110 m water depth) in the same bay. In the core-top record, the fluctuations of sardine and anchovy scale deposition rates (SDR) agreed with those of industrial catches for these two species in northern Chile, tending to validate the SDR as a proxy of local fish biomass when bottom anoxic conditions prevail. However, apparent SDR for records prior to 1820 have probably been influenced by dissolution processes linked to the oxygenation of the bottom environment of Mejillones Bay, as suggested by other proxy records. After 1820, the fluctuations in the relative abundance of sardine and anchovy scales point to alternating warm and cold conditions during about 30 years and then a progressively cooler period. Since ca. 1870, marked fluctuations of SDR of both species are observed, probably as a consequence of the onset of a different oceanographic regime characterized by intensified upwelling, stronger subsurface oxygen deficiency, higher primary productivity, and enhanced “ENSO-like” interdecadal variability. While anchovy SDR fluctuated in periods of 25–40 years, only two peak periods of sardine SDR occurred (late 19th century and late 20th century), suggesting that sardine abundance depends on other ocean–climatic factors.  相似文献   

Application of food waste based diets in polyculture of low trophic level fish: Effects on fish growth,water quality and plankton density     

Wing Yin Mo  Zhang Cheng  Wai Ming Choi  Yu Bon Man  Yihui Liu  Ming Hung Wong 《Marine pollution bulletin》2014

Food waste was collected from local hotels and fish feed pellets were produced for a 6 months long field feeding trial. Three types of fish feed pellets (control diet: Jinfeng® 613 formulated feed, contains mainly fish meal, plant product and fish oil; Diet A: food waste based diet without meat and 53% cereal; Diet B: food waste based diet with 25% meat and 28% cereal) were used in polyculture fish ponds to investigate the growth of fish (grass carp, bighead and mud carp), changes in water quality and plankton density. No significant differences in the levels of nitrogen and phosphorous compounds of water body were observed between 3 fish ponds after the half-year feeding trial, while pond receiving Diet A had the highest density of plankton. The food waste combination of Diet B seems to be a better formulation in terms of the overall performance on fish growth.  相似文献   

Benthic foraminifera assemblages as elemental pollution bioindicator in marine sediments around fish farm (Vrgada Island,Central Adriatic,Croatia)     

Jelena Vidović  Matej Dolenec  Tadej Dolenec  Vatroslav Karamarko  Petra Žvab Rožič 《Marine pollution bulletin》2014

Effects on sediments of fish farming activity near Vrgada Island was analysed through living and total foraminiferal assemblages and concentration of major, minor and trace elements from three sediment cores. Elemental concentrations of sediments are in accordance with carbonate characteristics of the surrounding area and show mostly natural element variations between sampling locations and throughout the cores, with no significant increases due to fish farming activity. Only phosphorus concentration shows elevate values below the fish cage, assigned to fish pellets. Foraminiferal communities are dominated by epifaunal and stress tolerant species, while diversity indices point to normal marine conditions. The type of substrate and phosphorus content in sediments principally influence foraminiferal community composition, while other elemental concentrations have no perceptible effect on the assemblages. Some foraminiferal species Ammoniatepida, Ammoniabeccarii, Elphidiumcrispum, Elphidiummacellum and genus Haynesina are confirmed to be tolerant to elevated nutrient (phosphorus) content, while Ammonia parkinsoniana shows sensitivity to pollution. Postmortem processes cause decrease of foraminiferal density and species richness with core depth. All results point to negligible influence of fish farming and relatively stable environmental conditions at all sampling locations.  相似文献   

Total mercury concentrations in lionfish (Pterois volitans/miles) from the Florida Keys National Marine Sanctuary,USA     

《Marine pollution bulletin》2014,78(1-2):51-55

Strategies to control invasive lionfish in the western Atlantic and Caribbean are likely to include harvest and consumption. Until this report, total mercury concentrations had been documented only for lionfish from Jamaica, and changes in concentrations with increasing fish size had not been evaluated. In the Florida Keys, total mercury concentrations in dorsal muscle tissue from 107 lionfish ranged from 0.03 to 0.48 ppm, with all concentrations being less than the regulatory threshold for limited consumption. Mercury concentrations did not vary consistently with standard lengths or wet weights of lionfish. In 2010, lionfish from the upper Keys had mean concentrations that were 0.03–0.04 ppm higher than lionfish from the middle Keys, but mean concentrations did not differ consistently among years and locations. Overall, total mercury concentrations in lionfish were lower than those in several predatory fishes that support commercial and recreational fisheries in Florida.  相似文献   

The expansion,limit and decline of the global marine fish catch     

Giulio Pontecorvo  William E. Schrank 《Marine Policy》2012

Catch of marine fish grew from after WW II–1989, at which point it stabilized. In 1996 it began to decline. It continues to decline now, at a time when earth's population is expected to reach 10 billion by 2050. Since the factors driving the increase are primarily the growth in income, population, technology of catching fish and ever increasing fishing effort, it is to be expected that the aggregate marine catch will continue to decline. This decline has important implications for marine ecosystems but primarily its importance relates to the human use of other global resources such as food, water and world's climate.  相似文献