Kepone concentration in juvenile anadromous fishes

Young-of-the-year alewife, American shad, blueback herring, and striped bass were analyzed for Kepone contamination. Samples were collected from the Potomac, Rappahannock, Pamunkey, Mattaponi, Chickahominy, and James rivers during the period 1977–79. Concentrations of Kepone ≥0.3 ppm occurred in all four species collected in the James River nursery zone between km 65 and 120, and in the lower Chickahominy River. Concentrations of Kepone <0.3, ppm were also present in samples from the Mattaponi and Pamunkey rivers. Four possible explanations, for the occurrence of Kepone in these samples from the upper York River system (Mattaponi and Pamunkey rivers) were, evaluated. Kepone was not detectable in samples from the Rappahannock and Potomac rivers.     

Effects of low dissolved oxygen events on the macrobenthos of the lower Chesapeake Bay

The effects of low dissolved oxygen or hypoxia (<2 mg l^?1) on macrobenthic infaunal community structure and composition in the lower Chesapeake Bay and its major tributaries, the Rappahannock, York, and James rivers are reported. Macrobenthic communities at hypoxia-affected stations were characterized by lower species diversity, lower biomass, a lower proportion of deep-dwelling biomass (deeper than 5 cm in the sediment), and changes in community composition. Higher dominance in density and biomass of opportunistic species (e.g., euryhaline annelids) and lower dominance of equilibrium species (e.g., long-lived bivalves and maldanid polychaetes) were observed at hypoxia-affected stations. Hypoxia-affected macrobenthic communities were found in the polyhaline deep western channel of the bay mainstem north of the Rappahannock River and in the mesohaline region of the lower Rappahannock River. No hypoxic effects on the infaunal macrobenthos were found in the York River, James River, or other deep-water channels of the lower Chesapeake Bay.     

The distribution of heavy metals in the hard clam,Mercenaria mercenaria,in the lower Chesapeake Bay region

Populations of the hard clam,Mercenaria mercenaria, were sampled at thirty sites in the lower Chesapeake Bay region in 1972 and 1973. Subsamples were taken for analysis for the trace metals cadmium, copper and zinc. Emphasis was placed on samples from the York and James rivers, two very productive and commercially utilized clam grounds. The levels of metals determined were comparable to those reported from other regions except Southampton Water in the United Kingdom. Differences in levels between the York and James rivers were statistically significant (P<0.001) which indicates that the James River probably suffers from contamination by these metals. One metal, copper, varied significantly with the age of the organism whereas the other two, cadmium and zinc, varied with salinity. InMercenaria the salinity of the sampling site must be considered before cadmium and zinc data can be interpreted. A standard action-level to denote pollution from copper would be adequate in this species.     

Hypoxia and salinity in Virginia estuaries

Hypoxia, periods of reduced dissolved oxygen concentrations, has been observed not only in the Chesapeake Bay but also in the deeper waters of the Virginia estuaries that are tributaries to the Chesapeake Bay. When water temperature exceeded 20°C, minimum oxygen concentrations were observed to be <50% of saturation concentrations in 75%, 50% and 2% of the surveys in the estuaries of the Rappahannock, York and James rivers, respectively. The observation that hypoxia rarely occurred in the James River is surprising, given the fact that it receives the greatest amount of wastewater. Analysis of the oxygen budgets in these estuaries indicates that the variations in the frequency, duration, and severity of hypoxia are related to the net movement of bottom waters. This relationship has significant implications for the management of water quality and marine fisheries.     

Annual cycle of kepone® residue and lipid content of the estuarine clam,Rangia cuneata

Factors affecting Kepone uptake and lipid content of the clam,Rangia cuneata, were tested over a 12 month study. Clams obtained from the Rappahannock and James Rivers were held in submersible liver boxes at two sites in the James River estuary and were sampled monthly from September 1978 through August 1979. Clams held in the freshwater zone near the source of Kepone contamination (Hopewell, Virginia) generally had higher Kepone and lipid content than those held downstream in the oligohaline zone. Significant differences in Kepone content between test sites and months are largely, but not entirely, a function of ambient water temperature, dissolved oxygen, amount of lipid in the clam, turbidity, Kepone content of the water column and duration of exposure. Lipid content of clams varied significantly between test sites, river of origin and months and is significantly related to salinity, ambient water temperature, pH and duration of exposure. Kepone content was more closely correlated with total lipid stores of clams than any other real variable. This association may be due to lipid reserves acting as a storage site for Kepone, but may also be interpreted as the result of selection against clams lacking lipid stores that might act as reservoirs for Kepone thus protecting more delicate tissues.     

Partial Migration Across Populations of White Perch (<Emphasis Type="Italic">Morone americana</Emphasis>): A Flexible Life History Strategy in a Variable Estuarine Environment

We evaluated the prevalence of partial migration, coexisting resident and migratory life history types, within six white perch (Morone americana) populations in sub-estuaries (Upper Bay, and Potomac, Choptank, Nanticoke, James, and York Rivers) of the Chesapeake Bay. Otolith stable isotope (δ¹⁸O) values were used to resolve fish habitat use along an estuarine salinity gradient and define resident or migratory behavior. The majority of adults within Upper Bay and Potomac River populations were resident, whereas individuals from the Choptank, Nanticoke, James, and York Rivers were predominantly migratory. Beyond population differences, large interannual variability in life history types was observed, likely due to differences in estuarine conditions that influence growth rate of individuals (e.g., temperature, zooplankton density). Because we observed partial migration in all study populations, we suggest that this trait is characteristic of this species, permitting plastic responses to variation in the estuarine environment.     

A comparison of phytoplankton assemblages and environmental relationships in three estuarine rivers of the lower Chesapeake Bay

A 16-month data set of phytoplankton assemblages and environmental parameters were studied in the lower James, York (-Pamunkey), and Rappahannock rivers using several exploratory statistical approaches. Based on species composition and river station relationships, three site groups were established and subsequently identified as predominantly tidal fresh, oligo-mesohaline, and mesohaline sites. Phytoplankton assemblages within these rivers were influenced and subsequently augmented by the onset of the spring freshet which was different in 1986 and 1987. Five temporal assemblages of phytoplankters were also identified and designated into seasonal groupings of spring 1986, summer-fall, summer-winter, fall-winter, and winter-spring 1987. Discriminant analysis (MANOVA) evaluations were made for water quality parameters to site and seasonal phytoplankton assemblages and these relationships are discussed. Moving downstream along an oligohaline-mesohaline gradient, the nitrogen and phosphorus levels decreased and the phytoplankton composition was more similar at several corresponding site locations in the different rivers than at stations relatively close to each other in the same river. Within these data sets approximately 58% of the explained variance was associated with site (spatial) effects, 30% with temporal effects, and 12% with site-temporal interactions. A transition from dominant bloom-producing freshwater diatoms to estuarine species occurs from the tidally influenced freshwater zone downstream. This change may be rapid as the decline ofSkeletonema potamos, or more gradual, as withCyclotella striata andCyclotella meneghiania. These are replaced downstream bySkeletonema costatum, Cyclotella caspia, andLeptocylindrus minimus as dominant species.     

Hypoxia in Chesapeake Bay Tributaries: Worsening effects on Macrobenthic Community Structure in the York River

We assessed the effects of hypoxia on macrobenthic communities in the York and Rappahannock Rivers, Chesapeake Bay, in box-core samples before and after hypoxic episodes in 2003 and 2004. Hypoxia occurred in both years and was associated with a decrease in biomass and a shift in community structure toward opportunistic species in both rivers. Long-term data indicate that the frequency of hypoxia in the York has increased over the last 22 years. In previous work from ∼20 years ago, the macrobenthic community structure did not change in response to hypoxia in the York; however, in the present study hypoxia was associated with a reduction in community biomass and a change in community structure. We conclude that currently hypoxia is a more important environmental problem in the York than in previous years. Hypoxia likely negatively affects the estuarine food web, as lower macrobenthic biomass could decrease food availability to epibenthic predators.     

Survival,duration of larval stages,and size of postlarvae of grass shrimp,Palaemonetes pugio,reared from kepone® contaminated and uncontaminated populations in Chesapeake Bay

Replicate groups of larvae from each of three female grass shrimp,Palaemonetes pugio, collected at each of six sites within Chesapeake Bay were reared in the laboratory to metamorphosis at 25°C, 25 ppt salinity. They were provided with approximately 300Artemia nauplii/larva/day. Sites were selected to provide both suspected Kepone^® contaminated and non-contamined shrimp populations. A sample of eggs, adult females with and without eggs, and newly hatched larvae from each site were analyzed by Virginia Institute of Marine Science for Kepone as were postlarvae obtained through laboratory rearings. Females and eggs from the James River had highest concentrations of Kepone (0.63 and 0.47 ppm, respectively) with samples from the Lafayette River at the mouth of the James River having the second highest levels (0.04 and 0.4 ppm). Concentrations in ovigerous females and eggs in the populations most distant from the James (mouth of Potomac and upper Potomac River) were at or below the limits of detectability (0.001 to 0.015 ppm). In laboratory reared postlarvae from each site, concentrations of Kepone were undetectable. Despite these apparent differences in Kepone concentrations in the various populations we found no significant differences in larval survival, larval duration, or length of post-larvae attributable to site of origin. Highly significant differences in larval duration and size of post-larvae were attributable to parental variation.     

Hydrogeologic assessment of escalating groundwater exploitation in the Indus Basin, Pakistan

Groundwater development has contributed significantly to food security and reduction in poverty in Pakistan. Due to rapid population growth there has been a dramatic increase in the intensity of groundwater exploitation leading to declining water tables and deteriorating groundwater quality. In such prevailing conditions, the hydrogeological appraisal of escalating groundwater exploitation has become of paramount importance. Keeping this in view, a surface water–groundwater quantity and quality model was developed to assess future groundwater trends in the Rechna Doab (RD), a sub-catchment of the Indus River Basin. Scenario analysis shows that if dry conditions persist, there will be an overall decline in groundwater levels of around 10 m for the whole of RD during the next 25 years. The lower parts of RD with limited surface water supplies will undergo the highest decline in groundwater levels (10 to 20 m), which will make groundwater pumping very expensive for farmers. There is a high risk of groundwater salinization due to vertical upconing and lateral movement of highly saline groundwater into the fresh shallow aquifers in the upper parts of RD. If groundwater pumping is allowed to increase at the current rate, there will be an overall decline in groundwater salinity for the lower and middle parts of RD because of enhanced river leakage.     

Dissolved Boron in the Tapi,Narmada and the Mandovi Estuaries,the Western Coast of India: Evidence for Conservative Behavior

The concentrations of dissolved boron have been measured during different seasons in three estuaries, the Tapi, Narmada and the Mandovi situated on the western coast of India, to investigate its geochemical behavior and inputs from the localized anthropogenic pressures of industrial effluents and sewage discharge. The measured boron concentrations in these estuaries (except the Tapi during non-monsoon) at salinity ≤0.1 fall in a narrow range?～?2–4 μmol/kg (average B?～?2.4?±?0.8 μmol/kg) within the reported wide range?～?0.1–18.6 μmol/kg for global rivers. The much higher estimate of boron concentration in the Tapi River during non-monsoon is attributed to its possible additional supply from the sewage and/or industrial effluents discharged along the river course. During monsoon, the rains seem to be a significant source of dissolved boron to all the three rivers. The distribution of dissolved boron in each estuary exhibits a conservative behavior during the seasons sampled suggestive of no measurable addition or removal of boron in the estuarine region. The orders of magnitude differences in boron concentration between the river waters and seawater, and the conservative behavior of dissolved boron indicate that its major contributor to the estuaries sampled is seawater.     

Composition and textural variability along the 10 m isobath,Great Barrier Reef: Evidence for pervasive northward sediment transport

Previous workers have proposed that northward‐directed bedload transport dominates the inner shelf of the Great Barrier Reef lagoon. Results from a sediment sampling survey along the 10 m isobath between Bowen and Cape York reveal a series of northward trends of increasing sediment maturity and demonstrate pervasive north‐directed sediment transport interacting with a succession of sediment (fluvial) sources. South of the Tully River, the occurrence of limited compositional variability indicates significant mixing on the inner shelf. However, further north the data are highly variable, suggesting that sediment inputs from individual rivers may be retained relatively close to source. This may be related to a greater sediment trapping efficiency within northern embayments and/or by lower net rates of along‐shelf transport.     

Contaminants from cretaceous black shale: II. Effect of geology,weathering, climate,and land use on salinity and selenium cycling,Mancos Shale landscapes,southwestern United States

The Cretaceous Mancos Shale (MS) is a known nonpoint source for a significant portion of the salinity and selenium (Se) loads in the Colorado River in the southwestern United States and northwestern corner of Mexico. These two contaminants pose a serious threat to rivers in these arid regions where water supplies are especially critical. Tuttle et al. (companion paper) investigates the cycling of contaminants in a Colorado River tributary watershed (Uncompahgre River, southwestern Colorado) where the MS weathers under natural conditions. This paper builds on those results and uses regional soil data in the same watershed to investigate the impact of MS geology, weathering intensity, land use, and climate on salt and Se storage in and flux from soils on the natural landscape, irrigated agriculture fields, areas undergoing urban development, and wetlands. The size of salinity and Se reservoirs in the MS soils is quantified. Flux calculations show that during modern weathering, natural landscapes cycle salt and Se; however, little of it is released for transport to the Uncompahgre River (10% of the annual salinity and 6% of the annual Se river loads). When irrigated, salinity and Se loads from the MS soil increase (26% and 57% of the river load, respectively), causing the river to be out of compliance with Federal and State Se standards. During 100 years of irrigation, seven times more Se has been removed from agricultural soil than what was lost from natural landscapes during the entire period of pedogenesis. Under more arid conditions, even less salt and Se are expected to be transported from the natural landscape. However, if wetter climates prevail, transport could increase dramatically due to storage of soluble phases in the non-irrigated soil. These results are critical input for water-resource and land-use managers who must decide whether or not the salinity and Se in a watershed can be managed, what sustainable mitigation strategies are possible, and what landscapes should be targeted. The broader implications include providing a reliable approach for quantifying nonpoint-source contamination from MS and other rock units elsewhere that weather under similar conditions and, together with results from our companion paper, address the complex interplay of geology, weathering, climate, and land use on contaminant cycling in the arid Southwest.     

Effects of two hurricanes onSyringodium filiforme, manatee grass, within the Loxahatchee River estuary, Southeast Florida

In September 2004, the Loxahatchee River Estuary was affected by Hurricanes Frances and Jeanne, which resulted in a monthly rainfall record of 610 mm and abnormally high freshwater discharges to the system. The occurrence, density, and biomass ofSyringodium filiforme in the Loxahatchee River Estuary declined significantly following the September 2004 storms based on 15 mo of pre-hurricane monitoring and 12 mo of post-hurricane monitoring. Throughout posthurricane monitoring,S. filiforme showed no sign of recovery, thoughHalophila johnsonii increased considerably during the post-hurricane period. Freshwater discharges resulting from the September 2004 hurricanes lowered minimum daily salinity values to near zero and increased standard deviation of daily salinity values to 11‰. Extremely low minimum daily salinity values and high daily salinity fluctuations likely resulted in the observed decline ofS. filiforme. We advise the use of minimum daily salinity values when assessing seagrass habitat suitability or when modeling the effects of alternative water management scenarios.     

Multi-element geochemistry of sediments from the Pearl River system,China

Sediment samples were taken along the West, North, and East rivers of the Pearl River system at 28 locations in 1998, and a total of 49 elements were determined by ICP–AES, ICP–MS and INAA. The probability features of the datasets were studied, and the average concentrations of these elements in sediments of the three rivers were calculated. Significant differences in element concentrations among the three rivers were observed and the results were confirmed by statistical tests including analysis of variance (ANOVA), Kruskal–Wallis test, and t-test. Spatial distribution maps of element concentrations were produced using a geographical information system (GIS). The immobile trace elements (such as Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are enriched in the West River where limestone dominates the rock types in the watershed. Because of the strong weathering, immobile trace elements are enriched and reside in secondary minerals of the weathering products. All three rivers have high concentrations of rare earth elements (REEs) because of strong weathering, but relatively higher concentrations of REEs are observed in sediments of the East River where granite dominates the rock type. Granite contains high concentrations of REEs and the sediments have inherited this feature from their bedrock. Alkaline element (Li, Na, K, Rb, and Cs) concentrations are elevated in sediments of the East River, these may reside in granitic primary minerals. Relatively high concentrations of alkaline earth elements (Mg, Ca, Sr, and Ba) are observed in the West River, inherited from the limestone bedrock. High Pb and Bi concentrations are found in the North River and are caused by Pb mineralization and the discharge of a smelter in the upper reaches of the river. However, statistical tests did not indicate a significant difference between Pb concentrations in the North River and the other two rivers, which suggests that statistical results should be carefully used and explained.     

Secondary turbidity maximum in a partially mixed microtidal estuary

Data from a two-year period of monthly slackwater surveys reveal that in addition to the classical estuary turbidity maximum (ETM), another peak of bottom total suspended sediment (TSS) concentration, or a so-called secondary turbidity maximum (STM), often exists in the middle part of the York River estuary, Virginia. This STM, observed in most (but not all) of the slackwater surveys, moves back and forth in the region of about 20 to 40 km from the York River mouth where the mud percentage of bottom sediment is very high. The distribution of the potential energy anomaly, which was calculated using salinity data, indicates that the STM usually resides in the transition zone between the upstream well mixed and the downstream more stratified water columns. An analysis using the conservation equation of suspended sediment concentration in the water column reveals that four processes may contribute to the formation of the STM: convergence of bottom residual flow, tidal asymmetry, inhibition of turbulent diffusion by stratification, and bottom resuspension. The along-channel variations of the strength of bottom residual flow, the effect of tidal asymmetry, and the stratification patterns are probably due to the geometric features of the York River estuary.     

Serum transferrin polymorphism in grey trout,Cynoscion regalis,from the lower Rappahannock River

Serum transferrin distribution was studied in grey trout, Cynoscion regalis, obtained from the lower Rappahannock River of Virginia. Three phenotypes were observed, representing two codominant alleles at a single gene locus. The distribution of the phenotypes, designated as Tf A, Tf B, and Tf AB, did not differ significantly from that predicted by Hardy-Weinberg analysis.     

Spatiotemporal variation of meteorological droughts based on the daily comprehensive drought index in the Haihe River basin,China

Meteorological droughts can affect large areas and may have serious environmental, social and economic impacts. These impacts depend on the severity, duration, and spatial extent of the precipitation deficit and the socioeconomic vulnerability of the affected regions. This paper examines the spatiotemporal variation of meteorological droughts in the Haihe River basin. Meteorological droughts events were diagnosed using daily meteorological data from 44 stations by calculating a comprehensive drought index (CI) for the period 1961–2011. Based on the daily CI values of each station over the past 50 years, the drought processes at each station were confirmed, and the severity, duration and frequency of each meteorological drought event were computed and analyzed. The results suggest the following conclusions: (1) the use of the CI index can effectively trace the development of drought and can also identify the duration and severity of each drought event; (2) the average drought duration was 57–85 days in each region of the Haihe River basin, and the region with the highest average values of drought duration and drought severity was Bohai Bay; (3) drought occurred more than 48 times over the study period, which is more than 0.95 times per year over the 50 years studied. The average frequencies of non-drought days, severe drought days and extreme drought days over the study period were 51.2, 3.2 and 0.4 %, respectively. Severe drought events mainly occurred in the south branch of the Hai River, and extreme drought events mainly occurred in the Shandong Peninsula and Bohai Bay; (4) the annual precipitation and potential evapotranspiration of the Haihe River basin show decreasing trends over the past 50 years. The frequency of severe drought and extreme drought events has increased in the past 20 years than during the period 1961–1990. The results of this study may serve as a reference point for decision regarding basin water resources management, ecological recovery and drought hazard vulnerability analysis.

     

Spatiotemporal variation of meteorological droughts based on the daily comprehensive drought index in the Haihe River basin,China

Meteorological droughts can affect large areas and may have serious environmental, social and economic impacts. These impacts depend on the severity, duration, and spatial extent of the precipitation deficit and the socioeconomic vulnerability of the affected regions. This paper examines the spatiotemporal variation of meteorological droughts in the Haihe River basin. Meteorological droughts events were diagnosed using daily meteorological data from 44 stations by calculating a comprehensive drought index (CI) for the period 1961–2011. Based on the daily CI values of each station over the past 50 years, the drought processes at each station were confirmed, and the severity, duration and frequency of each meteorological drought event were computed and analyzed. The results suggest the following conclusions: (1) the use of the CI index can effectively trace the development of drought and can also identify the duration and severity of each drought event; (2) the average drought duration was 57–85 days in each region of the Haihe River basin, and the region with the highest average values of drought duration and drought severity was Bohai Bay; (3) drought occurred more than 48 times over the study period, which is more than 0.95 times per year over the 50 years studied. The average frequencies of non-drought days, severe drought days and extreme drought days over the study period were 51.2, 3.2 and 0.4 %, respectively. Severe drought events mainly occurred in the south branch of the Hai River, and extreme drought events mainly occurred in the Shandong Peninsula and Bohai Bay; (4) the annual precipitation and potential evapotranspiration of the Haihe River basin show decreasing trends over the past 50 years. The frequency of severe drought and extreme drought events has increased in the past 20 years than during the period 1961–1990. The results of this study may serve as a reference point for decision regarding basin water resources management, ecological recovery and drought hazard vulnerability analysis.     

1956—2018年中国江河径流演变及其变化特征

地表水资源是维系区域生态平衡和促进经济社会发展的制约性要素,河川径流是地表水资源的主要形式,二者的丰枯变化均直接影响流域水资源管理。基于江河实测径流量资料和水资源公报资料,初步分析了1956—2018年中国主要江河实测径流量和中国十大水资源区地表水资源的变化和演变特征。结果表明:① 除长江大通站外,中国主要江河代表性水文站实测年径流量均呈现下降趋势。② 黄河上游唐乃亥站实测年径流量为非显著性减少趋势,黄河花园口站实测径流量呈现显著性减少趋势;1980—2000年和2001—2018年唐乃亥站实测径流量较基准期1956—1979年分别变化1.8%和-5.9%,而同时期花园口站实测径流量分别减少26.7%和41.0%。③ 地理分布上,黄河是中国南北地区径流变化的分水岭,黄河以南地区江河径流量为非显著性变化,黄河以北江河径流量为显著性减少趋势,特别是海河流域,实测径流量减少最为显著;21世纪以来,黄河以北河流实测径流量较1980年之前减少幅度超过25%,海河减幅高达80%以上。④ 1956—2018年全国地表水资源量约为27 266亿m³,较第二次全国水资源评价结果偏少122亿m³。21世纪以来,海河、黄河、辽河地表水资源明显减少,进一步加重了区域水资源供需矛盾。