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1.
The Shad fisheries of the Chesapeake Bay in Maryland have been declining since an 1897 peak of 7860 × 103kg. No periods of stability have been recorded. Data are presented to trace the decline not only as a function of specific areas within the Northern Chesapeake Bay but also in terms of environmental problems and recruitment overfishing.The problem is related to improving the commercial fishing yield. An estimation of a maximum effort of 200,000 man-hours is suggested if a stable yield is to be approached. Methods for obtaining this goal include alternating of closed fishing areas, adoption of rest days, enforcement of fisheries regulations and reduction of the number of metres of gill net used per fisherman.  相似文献   

2.
Larvae of striped bass (Morone saxatilis (Walbaum)) were exposed to a mixture of organic and inorganic contaminants in fresh well water and 2 g L?1 saline water for 30 days and in 5 g L?1 saline water for 90 days. Environmental concentrations (ECs) of organic and inorganic chemicals were estimated for the Chesapeake Bay area. Striped bass were exposed to the EC, 0.25 EC, 0.5 EC, 2 EC, 4 EC, and a solvent control to simulate potential conditions in their spawning and nursery habitats of the Chesapeake Bay. The sensitivities of striped bass as determined by survival depended on the characteristics of the exposure water. Larvae exposed in fresh well water were the most susceptible to the contaminant mixture; the 2 and 4 EC treatments caused significant (P:5 0.05) mortality within 30 days. In the 2 g L?1 salinity water, the 4 EC treatment caused significant mortality after 30 days of exposure. Larvae exposed to the contaminant mixture for 90 days in the 5 g L?1 saline water incurred significant mortality in the 2 and 4 EC treatments. We concluded that the age of the larvae, concentration of the contaminants, and salinity of the environment must be considered in evaluating the influence of environmental contaminants on the decline of striped bass along the east coast.  相似文献   

3.
Reduced striped bass populations along the East Coast of the United States have prompted numerous studies to assess various factors contributing to the decline. Available data from in-situ, on-site and laboratory studies with striped bass in conjunction with water quality and contaminants data confirm that the eastern shore rivers of the Chesapeake Bay (Choptank, Nanticoke, and Pocomoke Rivers) are susceptible to acidic conditions. The Choptank and Nanticoke Rivers are significant striped bass spawning areas. Acidification conditions (low pH, Al, low hardness) were documented in these systems in 1984 at levels reported to cause high mortality to striped bass larvae. Striped bass populations in several western shore tributaries such as the Mattaponi, Pamunkey, Patuxent, and Rappahannock Rivers also appear to be vulnerable to acidic pH conditions. In-situ toxicity studies documenting actual striped bass larval mortality are lacking in these systems; however, based on laboratory data it appears that potentially toxic acidic conditions can exist. Although certain Chesapeake Bay spawning tributaries do exhibit acidic conditions during spawning periods, other systems are resistant to acidification. The Chesapeake and Delaware Canal (C & D Canal), Elk River and Susquehanna River of the Upper Chesapeake Bay and the Potomac River on the western shore appear to be resistant to reductions in pH. The upper Chesapeake Bay and Potomac River are major striped bass spawning areas. Therefore, reduced striped bass production in these systems may be related to factors other than acidification.  相似文献   

4.
Chronic tributyltin toxicity experiments were conducted with the following Chesapeake Bay organisms: amphipod, Gammarus sp.; juvenile Atlantic menhaden, Brevoortia tyrannus and larval inland silverside, Menidia beryllina. TBT concentrations ranging from 29 to 579 ng L?1 did not significantly affect survival of the benthic amphipod, Gammarus sp. after 24-d exposures. The weight of Gammarus exposed to control conditions was 2.8 times greater than the weight of these test organisms exposed to 579 ng L?1 TBT. Twenty-eight day exposures to TBT concentrations of 93 and 490 ng L?1 did not significantly affect survival of juvenile B. tyrannus or larval M. beryllina. Histological examinations of B. tyrannus did not demonstrate absolute effects resulting from TBT exposure due to extensive variation between individuals. Various morphometric measurements of M. beryllina after TBT exposure did not demonstrate significant effects. However, significant reductions in growth were reported for M. beryllina at both TBT concentrations. Environmental concentrations of TBT in Chesapeake Bay and possible effects on the above biota are discussed.  相似文献   

5.
The Hudson River Foundation convened a conference to evaluate evidence pertaining to the roles played by acid deposition and stream acidification in the decline of anadromous fish populations along the Atlantic coastal plain. The stimuli for the conference were that (1) some populations of Atlantic salmon, American shad, hickory shad, alewives, blueback herring and striped bass as well as a few species resident in coastal streams (yellow perch and white perch) are in a state of severe decline along portions of the east coast of North America; (2) several of these species have declined more or less simultaneously since about 1970; and (3) severe episodic pH depressions are observed in some streams of the Chesapeake Bay system. For example, the pH of Lyons Creek decreased from 7.0 to 5.9 in 1 hr during a rain event, returning to 7.0 a day later. After discussing several possible mechanisms for these observations, the conferees agreed that a combination of factors including stream and river acidification, toxic metals and organic compounds, eutrophication and overfishing appears to be contributing to the reduction in fish stocks. The essential point resulting from the conference is that the acid deposition hypotheses for stream acidification and declines of anadromous fish populations, a potential mechanism that has received very little attention heretofore, was shown to be viable for these coastal areas. Specific recommendations for research were agreed upon by the conferees.  相似文献   

6.
Abstract

The objective of this research was to assess the long‐term effects of broiler litter applications on soil phosphorus (P), copper (Cu), zinc (Zn), manganese (Mn), and arsenic (As) concentrations in Chesapeake Bay watershed Coastal Plain soils. Litter and soil samples were collected from 10 farms with more than 40 years of broiler production and from wooded sites adjacent to fields and were analyzed for P and metal contents. Averaged over farms, total P and metal concentrations in the litter were 12.8 g kg?1 P and 332, 350, 334, and 2.93 mg kg?1 Cu, Zn, Mn, and As, respectively. Surface (0–15 cm) soil pH values were greater than (5.7–6.4) the 0‐ to 15‐cm depth at wooded sites (3.5–4.3). Surface soil Bray 1 P values (149–796 mg kg?1) in amended fields were greater than wooded sites (4.4–17 mg kg?1). The 1N nitric acid (HNO3)–extractable metal concentrations were higher in amended soils than in wooded areas and were 7.7–32, 5.7–26, 12.3–71, and 0.6–3.0 mg kg?1 for Cu, Zn, Mn, and As, respectively, compared to 0.76–14, 4.6–22, 1.6–70, and 0.14–0.59 mg kg?1 for the same metals, respectively, in wooded areas. Results from this study demonstrated that long‐term broiler litter applications have altered the chemical properties of the Coastal Plain soils of the Maryland Eastern Shore. Metal concentrations were low in the surface layer of amended fields and typically decreased with depth. Phosphorus additions rather than metals are most likely to contribute to the degradation of the Chesapeake Bay watershed.  相似文献   

7.
Arsenic distribution and dispersion in sediments of the EngenhoInlet and the Sepetiba Bay were investigated in order to evaluate the extent of the contamination caused by a metallurgical plant installed in the Sepetiba Bay watershed. The ore used in the smelting process, the soil around the plant, and ore waste collected inside the plant were also analyzed for As. Very high As concentrations in the stronglyand weakly bound fractions (up to 63 000 and 52 700 μgg-1, respectively) were found in the ore waste. The soilsalso contained high concentrations of both the strongly andweakly bound fractions (748 and 636 μg g-1, repectively), although the ore itself contained lower levelsof the two fractions (63 and 13 μg g-1, respectively).The sediments of the Engenho Inlet had a high degree of contamination (up to 347 μg g-1) decreasing toward Sepetiba Bay where the lowest concentrations were found (up to 50 μg g-1). Altough lower concentrations were found in the Sepetiba Bay sediments, they are 5 times higher than the world average. The results showed that there is an As transport from the Engenho Inlet to the Sepetiba Bay. These results suggests that the bay's fish and mollusk stock my be contaminated. This contamination may adversely affect the health of the local population, whose main protein supply is seafood.  相似文献   

8.
Water, Air, & Soil Pollution - Many management strategies to improve the health of Chesapeake Bay focus on reducing losses of sediments and nutrients from agricultural land. Plot-scale studies...  相似文献   

9.
The Susquehanna River watershed has a large drainage area (71200 km(2)) containing heavy agricultural land usage. The river provides approximately half the total freshwater input to the Chesapeake Bay. Water samples were collected at Conowingo Dam near the mouth of the river every 9 days from February 1997 through March 1998. Atrazine, its transformation product 6-amino-2-chloro-4-(isopropylamino)-s-triazine (CIAT), and metolachlor were found in the highest concentrations with maximums of 500, 150, and 330 ng/L, respectively. The annual mass loads for atrazine, CIAT, metolachlor, simazine, and 6-amino-2-chloro-4-(ethylamino)-s-triazine (CEAT) from the Susquehanna River to the Chesapeake Bay were 1600, 1600, 1100, 820, and 720 kg/year, respectively. Annual loadings of insecticides and organochlorine compounds ranged from 2.8 kg/year for alpha-HCH to 34 kg/year for diazinon. Strong correlations between loading data from this and previous studies and total annual water discharge through the dam were used to estimate total metolachlor and atrazine loads (12400 and 9950 kg, respectively) to the northern Chesapeake Bay from 1992 to 1997.  相似文献   

10.
基于鱼类保护目标的椒江环境流量研究   总被引：1，自引：0，他引：1  
以鱼类为保护目标, 通过建立概念模型将鱼类保护目标与流量之间的关系相联系, 识别了与椒江鱼类保护目标相关的环境流量组成要素。采用FLOWS 方法, 计算了椒江2 个断面的环境流量, 柏枝岙断面的低流量为6.8~17.3 m3·s-1、高流量为22.2 m3·s-1, 低流量脉冲为74 m3·s-1, 高流量脉冲为110 m3·s-1, 齐岸流量为948 m3·s-1; 灵海断面的低流量为16.0~31.8 m3·s-1, 高流量为46.0 m3·s-1, 齐岸流量为2 488~3 184 m3·s-1。并得出每组环境流量出现时间、持续时间和出现频率等的推荐结果。与Tennant 方法的计算结果比较, 采用FLOWS 计算方法能够反映环境流量的季节性变化特点, 同时体现了环境流量与自然流量过程的一致性。此研究结果可为椒江的水资源合理利用与河流生态系统保护提供理论依据。  相似文献   

11.
It has been hypothesized that human mercury (Hg) exposure via fish consumption will increase with increasing acidic deposition. Specifically, acidic deposition leads to reduced lake pH and alkalinity, and increased sulphate ion concentration ([SO4 2?]), which in turn should cause increased Hg levels in fish, ultimately resulting in increased human Hg exposure via fish consumption. Our empirical test of this hypothesis found it to be false. We specifically examined Hg levels in the hair of Ontario Amerindians, who are known consumers of fish from lakes across the province, and observed a weak negative association with increasing sulphate deposition. An examination of Hg levels in lake trout, northern pike and walleye, three freshwater fish species commonly consumed by Ontario Amerindians, found a similar weak negative association with increasing sulphate deposition. Further analysis of these fish data found that fish [Hg] was most significantly (positively) associated with lake water concentrations of dissolved organic carbon (DOC), not pH, alkalinity or [SO4 2?]. Lake DOC levels are lower in regions of greater acidic deposition. We propose an alternate hypothesis whereby human Hg exposure declines with increasing acidic deposition. In particular, we propose that increasing sulphate deposition leads to reduced lake DOC levels, which in turn leads to lower Hg in fish, ultimately reducing human Hg exposure via fish consumption.  相似文献   

12.
Concentrations of dissolved urea were monitored in several Chesapeake Bay tributaries from 1998 to 2002. Urea is a commonly used agricultural fertilizer and is also a breakdown product of poultry manure, which is used as an additional source of fertilizer throughout the watershed. Two trends were apparent. First, in several of the tributaries, seasonal peaks in ambient urea concentration coincided with the periods of the year (early spring and mid summer) when agricultural applications are most common. Second, highest annual mean concentrations (up to 2.6 μg atom N L?1), as well as highest individual measurements (up to 24 μg atom N L?1), were found for those tributaries with the most intensive agricultural and poultry operations. Peak urea concentrations were significantly higher than those which could be attained from in situ sources and regeneration. These elevated concentrations are of concern because this form of nitrogen has been shown to be a preferred form of nitrogenous nutrient for many phytoplankton, including some dinoflagellates which form harmful algal blooms. These results demonstrate that urea from land based sources can contribute to anthropogenic eutrophication.  相似文献   

13.
Otoliths of black bream (Acanthopagrus butcheri) collected from the Swan River Estuary were analysed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to measure concentrations of 14 trace metals. Trace metal concentrations in the otoliths may be related to the environmental exposure history of fish to contamination. The following metal isotopes were investigated: aluminium (27Al), calcium (44Ca), manganese (55Mn), iron (57Fe), copper (65Cu), zinc (66Zn), strontium (88Sr), cadmium (111Cd), tin (120Sn), barium (138Ba), mercury (202Hg), lead (208Pb) and the metalloids arsenic (75As, 77As) and selenium (82Se). Significant differences in otolith trace metal composition were found between sampling sites. Lead and 57Fe were consistently lower in downstream fish relative to upstream fish, while 88Sr varied with the salinity gradient in the urban estuary. Lead and 57Fe followed similar patterns within the otoliths, and appeared to provide the best discriminatory power for relating otolith metal concentration to the environmental history of the fish.  相似文献   

14.
Soils and vegetation of the coastal zone of the Khaipudyr Bay of the Barents Sea have been examined and compared with analogous objects in the Karelian coastal zone of the White Sea. The environmental conditions of these two areas are somewhat different: the climate of the Khaipudyr Bay coast is more severe, and the seawater salinity is higher (32–33‰ in the Khaipudyr Bay and 25–26‰ in the White Sea). The soil cover patterns of both regions are highly variable. Salt-affected marsh soils (Tidalic Fluvisols) are widespread. The complicated mesotopography includes high geomorphic positions that are not affected by tidal water. Under these conditions, zonal factors of pedogenesis predominate and lead to the development of Cryic Folic Histosols and Histic Reductaquic Cryosols. On low marshes, the concentrations of soluble Ca2+, K+ + Na+, Cl–, and SO2-4 ions in the soils of the Khaipudyr Bay coast are two to four times higher than those in the analogous soils of Karelian coast. Cluster analysis of a number of soil characteristics allows separation of three soils groups: soils of low marshes, soils of middle-high marshes, and soils of higher positions developing under the impact of zonal factors together with the aerial transfer and deposition of seawater drops. The corresponding plant communities are represented by coastal sedge cenoses, forb–grassy halophytic cenoses, and zonal cenoses of hypoarctic tundra. It is argued that the grouping of marsh soils in the new substantivegenetic classification system of Russian soils requires further elaboration.  相似文献   

15.
传统稻鱼系统生产力提升对稻田水体环境的影响   总被引：5，自引：0，他引：5  
如何在提升传统农业系统生产力的同时又不破坏其内涵、还对环境不产生负面影响,是一个受到研究者持续性关注的挑战性课题。本研究以具有1 200年历史的全球重要农业文化遗产稻鱼系统为例,研究稻鱼系统鱼的放养密度对生产力和环境的影响,探讨能够显著提升稻鱼系统生产力且又不破坏其传统性(产品优质、环境友好)的途径。研究表明,传统稻鱼系统(RF)(田鱼目标产量375 kg.hm 2)与水稻单作系统(RM)水体的化学需氧量(COD)、总氮(TN)、总磷(TP)及铵态氮(NH4+-N)含量均没有显著性差异。随着田鱼养殖密度提高(鱼产量由750 kg.hm 2提高到3 000 kg.hm 2)和饲料投入的相应增加,稻鱼系统的生产力和经济产出大幅度提高(稻鱼系统的净经济收入增加25.2%~101.4%),但稻鱼系统(RF)水体的COD值及TN、TP和NH4+-N含量均呈现增加的趋势,尤其是当鱼目标产量增至3 000 kg.hm 2时,水体TP含量和COD值显著提高,面源污染风险增加。分析还表明,鱼放养目标产量为2 250 kg.hm 2时,稻鱼系统经济效益最佳,此时净经济收入比传统稻鱼系统增加55.9%,并且不会对水体环境质量产生负面影响。  相似文献   

16.
Metal (Cu, Mn, Ni, Zn, Fe) concentrations in marine sediment and zooplankton were investigated in Izmir Bay of the Eastern Aegean Sea, Turkey. The study aimed to assess the levels of metal in different environmental compartments of the Izmir Bay. Metal concentrations in the sediment (dry weight) ranged between 4.26–70.8 μg g?1 for Cu, 233–923 μg g?1 for Mn, 14.9–127 μg g?1 for Ni, 25.6–295 μg g?1 for Zn, 12,404–76,899 μg g?1 for Fe and 38,226–91,532 μg g?1 for Al in the Izmir Bay. Maximum metal concentrations in zooplankton were observed during summer season in the inner bay. Significant relationships existed between the concentrations of certain metals (Al, Fe, Mn and Ni) in sediment, suggesting similar sources and/or similar geochemical processes controlling such metals. Higher concentrations of Cu, Zn and percent organic matter contents were found in the middle-inner bays sediments. Based on the correlation matrix obtained for metal data, organic matter was found to be the dominant factor controlling Cu and Zn distributions in the sediment. In general, mean Cu and Zn levels in the bay were above background concentrations in Mediterranean sediments. Zooplankton metal concentrations were similar to sediment distributions.  相似文献   

17.
From 1972–1989, Bougainville Copper Limited (BCL) dischargedmine tailings into Empress Augusta Bay on the west coast ofBougainville Island, Papua New Guinea. For a decade(1977–1987), trace elements (Cu, Pb, Zn, Cd, Hg and As) weremeasured in muscle tissue and organs of 8 species of tropicalmarine fish common to both the east and west coasts of theIsland. Metal concentrations were not elevated in muscle tissueof west fish compared with those from the east coast.Concentrations of Cu, Pb, Zn and Cd in fish muscle from bothcoasts ranged from 10–15% of recommended maximum residuelimits (MRLs), whereas concentrations of Hg in muscle wereslightly higher, ranging up to 80% of the MRL (0.5 mgkg-1 Hg wet wt.). Maximum total As concentrations (3.6 mgkg-1 wet wt.) were recorded in the shark (Rhizoprionodon acutus), while highest Hg values (0.76 mgkg-1 wet wt.) were found in hammerhead sharks (Sphyrnalewini) from both coasts. Despite significant temporalvariations in Hg and As concentrations in muscle tissue of somewest coast fish populations (p < 0.05), there was no evidencefor bioaccumulation or biomagnification of any of these metalsduring the 10 yr period, even in the soft organs (liver andkidney) of fish. Several site specific factors contributing toabsence of metals uptake from tailings are discussed.  相似文献   

18.

Purpose

Sediment cores provide a reliable record of mercury (Hg) contamination and can be used to study long-term Hg pollution and relevant environmental change. In the last hundred years, there were several events which may have contributed to the accumulation of Hg in Jade Bay and its catchment. This work was undertaken to assess the record in total Hg (THg) content in sediments of cores from Jade Bay and its catchment.

Materials and methods

A 5-m sediment core from Jade Bay, Lower Saxonian Wadden Sea, southern North Sea and a 12-m core from its catchment area (Wangerland, coastal zone of the Jade Bay) were used to study Hg contents in sediments. Total Hg, grain size distribution, aluminium (Al) and total organic carbon (TOC) were analysed on subsamples of both sediment cores. Total Hg was determined by oxygen combustion-gold amalgamation using DMA-80.

Results and discussion

As THg contents of the Jade Bay core were positively correlated to the sum of TOC and Al contents (r 2?=?0.86, p?<?0.001), the Hg data were interpreted using a regional normalisation function with the sum of Al and TOC as the normalisation parameters. Total Hg contents of the Wangerland core were correlated better to Al contents (r 2?=?0.70, p?<?0.001) than to the sum of TOC and Al contents (r 2?=?0.63, p?<?0.05). Therefore, Hg contents in sediments of the Wangerland core were normalised to Al contents. Comparison between enrichment factors and the background range of the sediment cores suggested that Jade Bay was contaminated about 50 years ago, and that Wangerland, or the catchment area of Jade Bay, was contaminated about 300 years ago, if no diagenetic remobilization occurred.

Conclusions

Total Hg contents of both cores were low and of no concern to the aquatic environment of Jade Bay. The Hg record was in good agreement with the history of industrial development in the region; thus, Hg deposition could have occurred through atmospheric input, ammunition residues of the Second World War and volcanic emanations, as well as through diagenetic remobilization.  相似文献   

19.
Shi  Jianjun  Guo  Jiangfeng  Chen  Hui 《Water, air, and soil pollution》2003,149(1-4):177-187
In order to get a better understanding of the environmental behavior of 95Zr and to generate fundamental data for evaluation of its ecological risk, an experiment was conducted to study the distribution and the migration of 95Zr in a simulated fish/seawater/sediment system over a period of 20 days. The concentration of 95Zr in seawater decreased rapidly with time, and its half-life is only 0.2 day. Most of adsorbed 95Zr was found in upper 2.5 cm in sediment, and more than 99.3% of applied 95Zr was detected in upper 2.5 cm duringthe whole experimental period, which implied that the 95Zr in seawater could be adsorbed strongly by sediment and it could not readily migrate downwards with percolating water. After taken in by fish, it was accumulated in viscera, gill, and fin. The concentration of 95Zr was very low in meat, bone, liver and roe, which was only slightly greater than the detection limit. The dynamics of 95Zr concentrations in fish, seawater and sediment can be described with exponential function.  相似文献   

20.
Decline in global surface water quality around the world is closely linked to excess sediment and nutrient inputs. This study examined sediment and phosphorus fluxes in Aquia Creek, a fourth-order sub-watershed of the Chesapeake Bay located in Stafford, Virginia. The Revised Universal Soil Loss Equation (RUSLE), sediment delivery ratio (SDR), field sediment traps, bank erosion pins, and LIDAR data, combined with historical aerial images, were used in quantifying rill and inter-rill erosion from the basin, as well as internally generated sediments. Stream water and stream bank soils were analyzed for phosphorus. RUSLE/SDR modeling estimates a basin total sediment flux of 25,247 tons year?1. The greatest calculated soil losses were in deciduous forests and cropland areas, whereas medium and high-intensity developed areas had the least soil loss. Cut-bank erosion ranged from 0.2 to 27.4 cm year?1, and annual bank sediment fluxes were estimated at 1444 Mg, with a corresponding annual mass of phosphorous of 13,760 kg year?1. The highest bank loss estimates were incurred along reaches draining urban areas. Stream water total phosphorous levels ranged from 0.054 μg g?1 during low flows to 134.94 μg g?1 during high discharge periods in autumn and spring. These results show that stormwater management practices in urban areas are limiting runoff water and soil contact, reducing surficial soil loss. However, the runoff acceleration due to expansion of impervious surfaces is progressively increasing the significance of intrinsic sediment and phosphorous sources by exacerbating stream bank erosion and resuspension of internally stored sediments.  相似文献   

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