Long-term monitoring using resident and caged mussels in Boston Harbor yield similar spatial and temporal trends in chemical contamination     

Carlton D. Hunt  Elizabeth Slone 《Marine environmental research》2010,70(5):343

Measurements of chemical contaminants in caged (transplanted) and resident mussel populations have become a routine tool for monitoring and assessing the status and trends of coastal water quality. However, few long-term data sets are available to assess the comparability and efficacy of these two monitoring approaches. Three long-term independent data sets exist for Boston Harbor: the National Mussel Watch program has analyzed resident blue mussels (Mytilus edulis) from the Boston Harbor/Massachusetts Bay region for over twenty years, the Massachusetts Water Resources Authority has annually deployed caged (transplanted) mussels (M. edulis) to assess bioaccumulation potential of sewage effluent discharged under its NPDES permit for over fourteen years, and the GulfWatch program has analyzed resident blue mussel populations for over twelve years. Together, these data provide consistent and comparable information on temporal and spatial changes in chemical contamination in Boston Harbor as steps were taken to reduce contaminant loading. The data also demonstrate the complementary nature of resident and caged (transplanted) mussels for assessing contaminant trends even when the basic approaches and sampling frequency differ. These fifteen-year data sets demonstrate contaminant concentrations in mussels from Boston Harbor are similar and with few exceptions have significantly decreased since the early 1990s. The observed trends also demonstrate broad scale improvements to the quality of Boston Harbor and expand understanding of the response of coastal systems to interventions that reduce the load of chemicals to the ocean.  相似文献   

The steps forward of GIS in China   总被引：2，自引：0，他引：2  

CHEN Shu peng  ZENG Shan  ZHONG Er shun 《中国地理科学(英文版)》2000,10(1):1-6

1　ＨＩＳＴＯＲＩＣＡＬＳＴＥＰＳ—ＡＴＥＭＰＯＲＡＬＡＮＡ ＬＹＳＩＳＲｅｓｅａｒｃｈｅｓｏｆＧＩＳｉｎＣｈｉｎａｃａｎｄａｔｅｂａｃｋｔｏｔｈｅｅａｒｌｙ 1980ｓ .Ａｔｔｈａｔｔｉｍｅ ,ａｒｅｍｏｔｅｓｅｎｓｉｎｇａｐｐｌｉｃａ ｔｉｏｎｐｒｏｊｅｃｔｗａｓｃａｒｒｉｅｄｏｕｔｉｎＳｏｕｔｈｗｅｓｔＣｈｉｎａｕｓｉｎｇＧＩＳｍｅｔｈｏｄｉｎｔｅｇｒａｔｅｄｗｉｔｈｒｅｍｏｔｅｓｅｎｓｉｎｇｄａｔａｔｏｓｏｌｖｅｔｈｅａｒｅａｍｅａｓｕｒｅｍｅｎｔａｕｔｏｍａｔｉｃａｌｌｙ .Ａｆｔｅｒｔｈｅｆｉｒ…  相似文献   

Variability and trends in runoff in the rivers of British Columbia's Coast and Insular Mountains          下载免费PDF全文

Marco A. Hernández‐Henríquez  Aseem R. Sharma  Stephen J. Déry 《水文研究》2017,31(18):3269-3282

This study examines the 1914–2015 runoff trends and variability for 136 rivers draining British Columbia's Coast and Insular Mountains. Rivers are partitioned into eastward and westward flowing rivers based on flow direction from the Coast Mountains. Thus, eastward and westward runoff trends and influence of topography on runoff are explored. Our findings indicate that rivers flowing eastward to the Nechako and Chilcotin plateaus contribute the lowest annual runoff compared to westward rivers where runoff is high. Low interannual runoff variability is evident in westward rivers and their alpine watersheds, whereas eastward rivers exhibit high interannual runoff variability. On Vancouver Island, some of the rivers with the highest annual runoff exhibit high interannual variability. A significant (p < .05) negative correlation exists between mean annual runoff (R_m) and latitude, gauged area, mean elevation, and its corresponding coefficient of variation. However, a significant positive correlation was found between the glacierized area of mountainous regions and R_m. The mean coefficient of variation in annual runoff is significantly negatively correlated with latitude and glacierized area, but significantly positively correlated with longitude. Annual and seasonal runoff trend analyses of each river were performed for an early (1936–2015), a middle (1966–2015), and a late (1986–2015) period using the Mann–Kendall test. Trend analyses revealed a shift towards more positive detectable (signal‐to‐noise ratio > 1) trends in annual and seasonal runoff from the middle to the late period across the study domain. Most positive detectable seasonal runoff trends in the middle period occur in spring in glacierized westward rivers located >1,200 m, whereas in the late period, they all occur in fall and are regionally coherent around Vancouver Island and south coastal BC. Rivers draining eastward exhibit more positive trends over 1986–2015 compared to westward rivers. This study provides crucial information on the hydrology of mountain watersheds across British Columbia's coast in response to Pacific Decadal Oscillation phase changes, the elevational amplification of regional climate change, and their influences on precipitation and glacier retreat.  相似文献   

Spatial and temporal patterns of dissolved organic matter quantity and quality in the Mississippi River Basin, 1997–2013          下载免费PDF全文

Sarah M. Stackpoole  Edward G. Stets  David W. Clow  Douglas A. Burns  George R. Aiken  Brent T. Aulenbach  Irena F. Creed  Robert M. Hirsch  Hjalmar Laudon  Brian A. Pellerin  Robert G. Striegl 《水文研究》2017,31(4):902-915

Recent studies have found insignificant or decreasing trends in time‐series dissolved organic carbon (DOC) datasets, questioning the assumption that long‐term DOC concentrations in surface waters are increasing in response to anthropogenic forcing, including climate change, land use, and atmospheric acid deposition. We used the weighted regressions on time, discharge, and season (WRTDS) model to estimate annual flow‐normalized concentrations and fluxes to determine if changes in DOC quantity and quality signal anthropogenic forcing at 10 locations in the Mississippi River Basin. Despite increases in agriculture and urban development throughout the basin, net increases in DOC concentration and flux were significant at only 3 of 10 sites from 1997 to 2013 and ranged between ?3.5% to +18% and ?0.1 to 19%, respectively. Positive shifts in DOC quality, characterized by increasing specific ultraviolet absorbance at 254 nm, ranged between +8% and +45%, but only occurred at one of the sites with significant DOC quantity increases. Basinwide reductions in atmospheric sulfate deposition did not result in large increases in DOC either, likely because of the high buffering capacity of the soil. Hydroclimatic factors including annual discharge, precipitation, and temperature did not significantly change during the 17‐year timespan of this study, which contrasts with results from previous studies showing significant increases in precipitation and discharge over a century time scale. Our study also contrasts with those from smaller catchments, which have shown stronger DOC responses to climate, land use, and acidic deposition. This temporal and spatial analysis indicated that there was a potential change in DOC sources in the Mississippi River Basin between 1997 and 2013. However, the overall magnitude of DOC trends was not large, and the pattern in quantity and quality increases for the 10 study sites was not consistent throughout the basin.  相似文献   

Evaluation of trends and predictability of short‐term droughts in three meteorological subdivisions of India using multivariate EMD‐based hybrid modelling     

Sankaran Adarsh  Manne Janga Reddy 《水文研究》2019,33(1):130-143

This paper presented trend analysis of droughts in Kerala, Telangana, and Orissa meteorological subdivisions in India and proposed a framework for drought prediction by employing the Empirical Mode Decomposition (EMD)‐based prediction models. The study used 3‐month standardized precipitation index (SPI3) for drought analysis. The trend analysis of SPI3 series for the period 1871–2012 using Mann–Kendall method showed statistically significant increasing trend in Kerala and Telangana subdivisions and a decreasing trend in Orissa subdivision. In addition, the non‐linear trend component extracted from EMD showed statistically significant changes in all the three subdivisions. Then, the study proposed a hybrid approach for prediction of short‐term droughts by coupling multivariate extension of EMD (MEMD) with stepwise linear regression (SLR) and genetic programming (GP) methods. First, the multivariate dataset comprising the SPI3 series of current and lagged time steps are decomposed using the MEMD. Then, SLR/GP models are developed to predict each subseries of SPI3 of desired time step considering the subseries of predictor variables at the corresponding timescales as inputs. The resulting models at different timescales are recombined to obtain the SPI3 values of the desired time step. The method is applied for prediction of short‐term droughts in the three subdivisions. The results obtained by the hybrid models are compared with that obtained by conventional prediction models using M5 Model Trees and GP. The rigorous performance evaluation based on multiple statistical criteria clearly exhibited the superiority of the hybrid approaches (i.e., prediction models with MEMD‐based decomposition over models without decomposition) for prediction of SPI3 in three subdivisions. Further, the study found that MEMD‐GP model performs marginally better than the MEMD‐SLR model due to its efficacy in modelling high frequency modes.  相似文献   

中国现代沙漠动态变化及其发展趋势   总被引：14，自引：0，他引：14  

钟德才 《地球科学进展》1999,14(3)

用遥感、地图和野外考察研究等方法,首次揭示了我国现代沙漠动态变化规律和发展趋势,认为我国现代沙漠动态变化的总趋势是向草原化和绿洲化方向缓慢发展,其变化速度为４４５ｋｍ２／ａ,我国现代沙漠还在继续蔓延,但其扩大速度比较缓慢,约为３１０ｋｍ２／ａ。  相似文献   

中国现代浙江省动态变化及其发展趋势   总被引：3，自引：0，他引：3  

钟德才 《地球科学进展》1999,14(3):229-234

用遥感,地图和野外考察研究等方法,首次揭示了我国现代沙漠动态变化规律和发展趋势,认为我国现代沙漠动态变化的总趋势是向草原化和绿洲化方向缓慢发展,其变化速度为４４５ｋｍ＾２／ａ,我国现代沙漠还在继续蔓延,但其扩大速度比较缓慢,约为３１０ｋｍ＾２／ａ。  相似文献   

Anthropogenic nutrient load of the Baltic Sea     

Günther Nausch  Dietwart Nehring  Gunni Aertebjerg 《Limnologica》1999,29(3):233

The discharge of nutrients is investigated in relation to their sources and effects in two case studies. The reduction of 47% in the phosphorus load from Denmark to marine areas between 1989 and 1993 has resulted in significantly lower phosphorus concentrations in most Danish coastal waters, and tendency to decrease can be seen in the Belt Sea and Kattegat as well. No general changes in nitrogen concentrations have been observed. This is due to the fact that more than 80% of the nitrogen load in Danish waters originate from diffuse agricultural sources.In the Pomeranian Bight strong nutrient gradients are generated by the mixing of Odra river water and coastal water. The spreading of the river plume could be exactly observed especially in winter, when biological activity is low. In general, different types of distribution, transport and modification patterns can be described.The annual input of nutrients from the catchment area to the Baltic Sea was estimated to be around 1000 kt N and 46 kt P. As a result, winter concentrations of phosphate and nitrate are characterized by positive overall trends in the surface layer in all subregions of the Baltic Proper for the period 1969 to 1993. These trends stem mainly from the strong increase in the 1970ies and early 1980ies. Thereafter, the concentrations of both nutrients fluctuate strongly around a high level. The drastic decrease in fertilizer consumption since the late 1980ies mainly caused by the great economic changes in the countries of the former East Bloc is not yet significantly reflected in decreasing winter concentrations, but first signs already have been found in the decrease in averaged phosphate concentrations in winter, especially in the Arkona and Bornholm Seas.  相似文献   

Abundance and Distribution Patterns of Nekton and Micronekton in the Northern California Current Transition Zone   总被引：1，自引：0，他引：1  

Richard D. Brodeur  William G. Pearcy  Stephen Ralston 《Journal of Oceanography》2003,59(4):515-535

The epipelagic and mesopelagic nekton communities of the northern California Current have been sampled somewhat continuously over the last four decades with bottom and pelagic trawls, small midwater trawls, and purse seines. We review the zoogeography and community and environmental associations of the dominant pelagic micronekton and nekton species in this region with a view to understanding their role in this dynamic marine ecosystem. As is typical of many upwelling eastern boundary current regions, the pelagic biomass is dominated by a few species that fluctuate dramatically through time. The abundance trends of pelagic nekton caught in this region demonstrated large-scale ecosystem changes about the time of the regime shifts of 1976/77 and 1989 and possibly another beginning in 1999. The rapidity of the changes in composition indicates that the response was due to a change in migration or distribution patterns as opposed to recruitment patterns. The 1989 regime shift led to a dramatic increase in sardine and a decrease in anchovy populations. The most pronounced interannual signals were attributed to strong El Niño/Southern Oscillation (ENSO) conditions in 1983 and 1998 that altered the latitudinal ranges and proximity to the coast of many pelagic species. Variations in abundance and cross-shelf distribution patterns were noted for both pelegic nekton and micronektonic from surveys off California, Oregon, and Washington.  相似文献   

Can the pattern of juvenile recruitment and population structure of the speckled swimming crab Arenaeus cribrarius (Decapoda: Brachyura) be determined by geographical variations?          下载免费PDF全文

Luciana Segura de Andrade  Israel Fernandes Frameschi  Antônio Leão Castilho  Rogério Caetano da Costa  Adilson Fransozo 《Marine Ecology》2015,36(4):950-958

This study evaluated the effect of environmental stimuli and selective pressures in different geographical areas along a latitudinal gradient, on the juvenile recruitment, population structure, and sex ratio of the speckled swimming crab Arenaeus cribrarius. Samples were collected monthly during 1 year in three locations along the Brazilian coast: Macaé, state of Rio de Janeiro (MAC, 22°47′ S, 41°45′ W); Ubatuba, São Paulo (UBA, 23°27′ S, 44°58′ W); and São Francisco do Sul, Santa Catarina (SFS, 26°08′ S, 48°34′ W). The specimens of A. cribrarius were identified, counted, sexed, and measured for maximum carapace width (CW). The largest juvenile found was in UBA (47.7 ± 1.36 mm); and the largest adult females and males in MAC (74.26 ± 0.93 and 77.04 ± 0.79 mm, respectively). Recruitment in MAC was continuous, whereas in UBA and SFS, recruitment showed seasonal characteristics. The sex ratio was skewed toward females only in UBA; in MAC and SFS, males and females were present in equal proportions. These results indicate that geographical variations can cause differences in the recruitment and population structure of A. cribrarius. These regional differences call attention to the necessity for improved management plans and control of shrimp fishing, which can affect population patterns such as juvenile recruitment, population structure and life history of the target species and species that are caught in bycatch from shrimping, such as the swimming crab A. cribrarius.  相似文献