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1.
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   

2.
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   

3.
Striped bass (Morone saxatilis) collected from the Annapolis and Shubenacadie Rivers in Nova Scotia, Canada, were analyzed for Hg in four tissues and for PCB's in two tissues. Average Hg concentrations in the muscle, liver, kidney, and gonad of 3.9 kg fish from Annapolis River were 0.77, 0.79, 0.26, and 0.07 μg g?1, respectively, and the corresponding values for the much smaller, 1.5 kg, fish from the Shubenacadie River were 0.51, 0.27, 0.24, and 0.06 μg g?1. The PCB concentrations in the muscle tissues of fish from Annapolis and Shubenacadie Rivers are 0.02 and 0.01 μg g?1, respectively, while the concentrations in gonads are 1.4 and 0.04 μg g?1 The observed lack of recruitment of striped bass in the Annapolis River may be related to high PCB concentrations in the gonad tissue.  相似文献   

4.
We studied the effects of acidification on female sexual behavior in brown trout (Salmo trutta) and compared the results with those in hime (land-locked sockeye) salmon (Oncorhynchus nerka) (Kitamura and Ikuta, 2000). The results were similar to those of sockeye salmon. Spawning brown trout were extremely sensitive to the acidity of ambient water, and nest-digging behavior was severely inhibited (p<0.05) by very slight acidification (pH below 6.4). However, there were some differences between the two species. Female trout and salmon showed almost no digging below pH 5.0 and 6.0 (Kitamura and Ikuta, 2000), respectively. When the ambient water was returned to nearly neutral (pH6.6) conditions, digging in hime salmon reappeared in 4 of the 6 fish tested (Kitamura and Ikuta, 2000), whereas digging in brown trout reappeared in all 6 fish tested. The above-mentioned differences in behavioral response between the two species appear to reflect the species difference in terms of vulnerability to acidification (Ikuta et al., 1992). Avoidance of slightly acidic water in selection of spawning site or cessation of spawning behavior in weakly acidic environments may be the most potent cause of the reduction of salmonid populations in the early stages of acidification.  相似文献   

5.
The Rhode River estuarine/watershed system is a tributary of Chesapeake Bay located on the inner Atlantic Coastal Plain. Its soils are fine sandy loams. Bulk precipitation pH in the spring season declined from 4.95 in 1974 to 3.82 in 1981 and was 4.03 in 1985. The changes in pH of a forested primary stream were more related to changes in bulk precipitation pH than were the changes in pH of agricultural streams, reflecting the importance of other major terrestrial sources of acidity on agricultural systems. Surges in acidity and dissolved total Al concentration in primary (first order) streams reached extremes of pH 3.2 and 300 μg Al L?1. Higher order streams were observed to have surges in acidity with pH minima below 5.0. Surges in acidity ocurred during accelerated groundwater percolation following storm events and did not coincide with surface runoff or snowmelt. One of the reasons why groundwater is more acidic than surface runoff is that the vegetation exchanges H30 + for alkaline cations in the soil and translocates these ions to the vegetational canopy. When it rains, subsequently, H30+ in the precipitation displace some of these alkaline cations from the canopy. The end result is that overland flow during storms is enriched in alkaline cations, while groundwater is enriched in H30+. Although the source of dissolved Al is dissolution of clay minerals with atomic ratios of Al to silicate of 1:l, 1:2, or 1:3, this ratio in stream water rapidly declined to 1:1200 due to loss of Al. On average, forest drainage was the most acidic, the highest in dissolved Al, and the lowest in Ca. Surges in acidity were most severe from pastureland, and next most severe from cropland. Total fluoride concentrations were high relative to Al from all three land uses. Rhode River spawning runs of Perca flavescens declined drastically from the early 1970s to essentially zero since 1981. Larval bioassays of acidity indicate negligible toxicity to Hyla crucifer, significant toxicity to Perca flavescens and drastic effects on Morone saxatilis at pH 5.0.  相似文献   

6.
The toxicity of Al and a mixture of inorganic contaminants to young striped bass Morone saxatilis in soft fresh water was demonstrated to be age- and pH-dependent. Toxicity of the contaminants was increased with decreases of pH of the test waters. The interaction between low pH from acid deposition and inorganic contaminants should be considered as a possible factor contributing to the decline in abundance of east coast striped bass.  相似文献   

7.
Restoration of riparian buffers is an important component of nutrient reduction strategies in the Chesapeake Bay watershed. In 1998, Maryland adopted a Conservation Reserve Enhancement Program (CREP), which provides financial incentives to take agricultural land out of production to plant streamside vegetation. Between 1998 and 2005, 1–30% of streamside vegetation (average?=?11%), was restored to forest or managed grass in 15 agriculturally dominated sub-basins in the Choptank River basin, a tributary of Chesapeake Bay. Pre-existing forested buffers represented 10–48% of the streamside (average?=?33%), for a total of 12–61% buffered streamsides (average?=?44%). Using multi-year water quality data collected before and after CREP implementation (1986, 2003–2006), we were unable to detect significant effects of CREP on baseflow nutrient concentrations based on the area of restored buffer, the percentage of restored streamside, or the percentage of total riparian buffer in the sub-basins (p?>?0.05). Although CREP increased the average buffered streamside from 33% in the 1990s to 44% by 2005, N and P concentrations have not changed or have increased in some streams over the last 20 years. Reductions may not have occurred for the following reasons: (1) buffer age, width, and connectivity (gaps) between buffers are also important to nutrient reductions; (2) agricultural nutrient inputs may have increased during this period; and (3) riparian buffer restoration was not extensive enough by 2005 to have measurable affects on the stream water quality in these sub-basins. Significant effects of CREP may yet be resolved as the current CREP buffers mature; however, water quality data through 2006 in the Choptank basin do not yet show any significant effects.  相似文献   

8.
Little Rock Lake was experimentally acidified in 1984–1990 during which sulfuric acid was added to one basin, decreasing pH from 6.1 to 5.6, 5.1 and 4.7. The lake has been allowed to recover without manipulation since autumn 1990. By the third year of recovery, ～40% of the change necessary to return to pre-acidification values of pH, acid neutralizing capacity (ANC), sulfate (SO4 2?) and calcium (Ca2+) had occurred. During recovery years 1–2, ANC was closely predicted by models based on acidification phase observations, but recovery during years 3–4 was slower than predicted. A possible explanation for the slowed recovery is acidification of the upper 0–5 cm of sediment, which acts as a sink for the ANC generated via SO4 2? reduction, the primary recovery mechanism. Trends for Zooplankton did not follow pH recovery very closely. Species diminished by acidification (e.g. Keralella cochlearis, Daphnia dubia) have not recovered, but species that dominated the community at pH 4.7 (e.g. K. taurocephala, D. catawba) have not maintained high populations. The time required for the Zooplankton community to recover to pre-manipulation conditions is uncertain. Delays also have been observed for the mayfly species Caenis, which had disappeared at pH 4.7. In contrast, reproductive success of largemouth bass (Micropterus salmonides) mirrored that observed during acidification; egg hatch and survival of young-of-the-year to autumn recurred when pH exceeded response levels documented during acidification. Overall, recovery has not closely followed the pattern predicted by acidification responses.  相似文献   

9.
Event-based precipitation samples were collected during the main agricultural season (April-September) over 4 years (2000-2003) at one site in the Choptank River Watershed on the Delmarva Peninsula. The samples were analyzed for 19 agricultural pesticides to determine the contribution of wet deposition as a source of these compounds to the Chesapeake Bay and the factors affecting the temporal trends in deposition. Chlorothalonil was detected most frequently (92% samples) followed by metolachlor (66%) and endosulfans (49%). Although chlorothalonil is the single biggest contributor to pesticide flux (33-46%), pesticide wet deposition is dominated by herbicides (46-61%), with the greatest fluxes occurring during the time of herbicide application on corn and soybeans. The analysis suggests that the extent of wet deposition of herbicides depends on the timing of precipitation relative to herbicide application. The insecticide and fungicide flux was greater in years with above-average rainfall (2001 and 2003), suggesting that for these pesticides deposition flux is dependent on the total amount of rainfall in the agricultural season. The data indicate that the use of chlorpyrifos, an organophosphate insecticide which is on the Toxics of Concern list for the Bay, is on the increase. Total pesticide flux ranged from 90 microg/m2 (2001) to 180 microg/m2 (2000). Wet deposition can account for up to 10-20% of the annual loadings of pesticides to the Bay.  相似文献   

10.
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   

11.
Fisher  T.R.  Lee  K.-Y.  Berndt  H.  Benitez  J.A.  Norton  M.M. 《Water, air, and soil pollution》1998,105(1-2):387-397
The Choptank River basin is a coastal plain catchment dominated by agriculture (52% of land use). We summarize an 11 year data set of discharge and chemistry from a gauged subbasin. Discharge exhibited seasonal variations driven by seasonal evapotranspiration. There were double seasonal maxima of pH, NH4 +, NO3 -, total N, Fe, and total P concentrations in late spring and fall as the saturated zone rose and fell within the soil. Significant interannual variability in discharge was the result of rainfall variation. There were positive nterannual trends in NO3 - concentrations and negative interannual trends in NH4 + and PO4 3- concentrations. These data were combined to estimate N and P export coefficients of 3-11 kg N ha-1 yr-1 and 0.14-0.66 kg P ha-1 yr-1, driven primarily by interannual variations in discharge. These export coefficients are low compared to other coastal plain watersheds dominated by agriculture and may be responsible for the small anthropogenic effects in the Choptank estuary compared to other Chesapeake drainages.  相似文献   

12.
The chemistry of 282 sampled low pH (<6.0) lakes in the U.S. E.P.A. Eastern Lake Survey (ELS) was evaluated in an attempt to assess why these systems have low pH. Evaluations were made using a decision protocol for classifying lakes according to several hypothesized acidifying mechanisms: acidic deposition, presence of wetlands and organic soils, acid mine drainage, watershed S sources, salt driven acidification, and changes in land use. The algorithm evaluates lakes in three steps: (1) initial exclusion criteria exclude from consideration lakes with pH greater than 6.0 or subject to strong confounding influences (e.g., road salt); (2) a general classification discriminates between lakes according to anion dominance; and (3) a secondary classification of lakes within each anion dominant class determines the most likely acidification pathway, using preliminary quantitative criteria designed to discriminate among competing hypotheses. Results computed for sampled lakes were scaled-up to produce regional population estimates, using the statistical framework of the ELS. Acidic deposition appears to be the most likely cause of low pH conditions in about two-thirds of the non-excluded lakes in the ELS low pH target population. Organic acidity arising from wetlands or land use changes appears to be primarily responsible for the low pH status of one quarter of these lakes. Watershed S sources and acid mine drainage appear to be of negligible importance, though further information on dry deposition rates and/or watershed soils is required to confirm this.  相似文献   

13.
Spatial and temporal variations of eight selected water quality measurements were examined for the 26 stations located in the Han River and its tributaries within the city of Seoul from 1993 to 2002. The eight measurements are water temperature, pH, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, suspended solid, total nitrogen and total phosphorus. There is no discernable increase or decrease in water quality measurements in four representative stations. A striking longitudinal variation of all water quality measurements is detected for eight stations along the Han River. Water quality dramatically decline in the middle section of the Han River where the river receives inputs from polluted tributaries. All water quality measurements, except pH, exhibit better conditions in the main river group than its counterpart tributary group. The 26 stations can be grouped into three main clusters; (1) the main river and its tributaries that have relatively good water quality, (2) the tributaries that have medium water quality, and (3) the tributaries nearby industrial sites that are heavily polluted.  相似文献   

14.
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   

15.
Groups of Eurytemora affinis were held in flow-through chambers and exposed to ambient water from moderately (Station 1) and heavily (Station 2) polluted sites in Chesapeake Bay tributaries. A control group was held in identical chambers supplied with water from a clean site. Survival, growth and reproduction were assessed after 10 days exposure. At the moderately polluted site, an additional treatment consisting of a 50∶50 mix of control and ambient water was also run. Survival of E. affinis was not a reliable indicator of water quality. Growth was indicative of water quality at each station, but not between stations. Relative fecundity was the best indicator of water quality within and between stations. At Station 1, the relative fecundity was 2.6, 4.2 and 10.0 in ambient, 50∶50 mix and control water, respectively. At Station 2, the relative fecundity was 0.8 and 10.0 in ambient and control water, respectively.  相似文献   

16.
The Norwegian monitoring programme of acidification include studies of invertebrates, which started in 1981. The invertebrate programme is based on kick samples from a fixed station net in 8 river systems. The stations include tributaries as well as stations in the main river. This paper deals with three rivers located in a gradient covering the range of acidic deposition in West Norway. The invertebrates are identified to species level and sorted with respect to acid sensitive and acid tolerant species, used for stating an acidification index. The spring samples generally show the highest acidification due to release of acids during snow smelt. In fall the acidity was lower and the index was less variable. A significant increase in the acidification index (reduced acidity) was recorded during fall in the period 1989 – 94 in two of the watersheds. In the third watershed no significant trend was recorded. During the years 1982 – 1988 a significant increase in the index occurred in spring in the watershed with lowest acidic deposition. The increases observed in the index is probably a result of the reductions in acid deposition in Norway.  相似文献   

17.
The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP-Water) started in 1987. The main aim of the programme is to establish degree and geographical extent of acidification of surface waters and evaluate dose/response relationships to aquatic biota attributable to acidic deposition. The sample frequency in each locality is from a few — to a large number every year. Samples of invertebrates are taken from 108 localities. One time samples as well as regularly seasonal samples over years exist in the database. The acidity score (Raddum index) is determined for the different sites and regions, and compared with the corresponding chemical data. The analysis show a strong relationship between water quality and fauna. Sensitive species/taxa are associated with high ANC and pH, while tolerant species/taxa are associated with low pH and ANC. The diversity of the fauna in less acidified areas varies from region to region depending on the native water quality and the adaptions of the fauna. In areas with strongly oligotrophic water, low in ionic strength, the sensitive fauna tolerate lower ANC and pH than in areas with originally high ionic strength and high pH. The critical load of ANC, 20 μeq/1, developed for the oligotrophic water in Norway, should therefore be increased in watersheds with high ionic strength. In Central Europe the data indicate a critical level of ANC ≈50 μeq/1.  相似文献   

18.
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   

19.
To investigate the consequences of acidification and metal accumulation on the biology of aquatic bryophytes, the acid-tolerant liverwort Scapania undulata (L.) Dum. and the acid-sensitive moss Rhynchostegium riparioides (Hedw.) Cardot were transplanted from one stream to two other streams of differing acidity (pH 5.20 and 6.38). The bryophytes were collected in a circumneutral (pH 6.57) stream in the Vosges Mountains. Metal accumulation was semi-quantitatively measured in shoots by energy dispersive TEM X-ray spectroscopy (EDXS). After 1 month, the two species remained green without alteration signs. Although no marked ultrastructural damage was observed in either species, some cells seemed to be necrotic, with flattened chloroplasts, in R. riparioides. Lipid droplet accumulation was observed in some leaf cells of S.undulata when transplanted to the most acidic stream. Metal was mostly localised in the cell wall, and was only sometimes detected in small vacuoles. Under acidic conditions, R. riparioides showed the highest relative amount of Al and the lowest amount of Fe, whereas the acid-tolerant bryophyte species S. undulata contained more Fe and less Al. The capability to limit the uptake of metals into the cytoplasm varies according to the bryophyte species. This could be an explanation of the tolerance of S. undulata to acidification.  相似文献   

20.
Nelson Lake, a moderately acidic (pH 5.7), metal-contaminated (Cu 22 μg L?1; Zn 18 ug L?1) lake, 28 km from the smelters at Sudbury, had a degraded fish community in the early 1970's, with lake trout (Salvelinus namaycush) scarce, smallmouth bass (Micropterus dolomieui) extinct, and the littoral zone dominated by the acid-tolerant yellow perch (Perca flavescens). Liming of the lake in 1975–76 increased pH to 6.4, and decreased metal concentrations. Chemical conditions have remained relatively stable in the 10 yr following base addition. Initially, it appeared that neutralization produced dramatic changes in the resident fish community. Yellow perch abundance declined rapidly after neutralization, lake trout abundance increased to the extent that 3.26 kg ha?1 were caught in the winter of 1980, and reintroduced smallmouth bass reproduced and established a large population. However, these changes in the fish community can not be directly attributed to liming, as water quality and the sport fisheries of an unlimed nearby lake also improved. Reduced emissions from Sudbury smelters were responsible for improvements in the untreated lake. Recovery of the lake trout population in Nelson Lake appears to have begun prior to liming. Of the lake trout sampled during the 1980 winter fishery, 65.8% were present prior to the chemical treatment. Predation by lake trout was the likely cause of the perch decline. Our results suggest that chemical conditions producing population level responses in fish have abrupt thresholds and that neutralization of lakes above these thresholds may not produce distinguishable effects.  相似文献   

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