Reversal of eutrophication following sewage treatment upgrades in the New River Estuary, North Carolina     

Michael A. Mallin  Matthew R. McIver  Heather A. Wells  Douglas C. Parsons  Virginia L. Johnson 《Estuaries and Coasts》2005,28(5):750-760

The New River Estuary consists of a series of broad shallow lagoons draining a catchment area of 1,436 km², located in Onslow County, North Carolina. During the 1980s and 1990s it was considered one of the most eutrophic estuaries in the southeastern United States and sustained dense phytoplankton blooms, bottom water anoxia and hypoxia, toxic outbreaks of the dinoflagellatePfiesteria, and fish kills. High nutrient loading, especially of phosphorus (P), from municipal and military sewage treatment plants was the principal cause leading to the eutrophic conditions. Nutrient addition bioassay experiments showed that additions of nitrogen (N) but not P consistently yielded significant increases in phytoplankton production relative to controls. During 1998 the City of Jacksonville and the U.S. Marine Corps Base at Camp Lejeune completely upgraded their sewage treatment systems and achieved large improvements in nutrient removal, reducing point source inputs of N and P to the estuary by approximately 57% and 71%, respectively. The sewage treatment plant upgrades led to significant estuarine decreases in ammonium, orthophosphate, chlorophylla, and turbidity concentrations, and subsequent increases in bottom water dissolved oxygen (DO) and light penetration. The large reduction in phytoplankton biomass led to a large reduction in labile phytoplankton carbon, likely an important source of biochemical oxygen demand in this estuary. The upper estuary stations experienced increases in average bottom water DO of 0.9 to 1.4 mg l⁻¹, representing an improvement in benthic habitat for shellfish and other organisms. The reductions in light attenuation and turbidity should also improve the habitat conditions for growth of submersed aquatic vegetation, an important habitat for fish and shellfish.  相似文献   

兴文天坑的崩塌过程     

Tony WALTHAM  张远海 《中国岩溶》2006,25(Z1):79-83

四川兴文喀斯特包括小岩湾天坑和大岩湾退化天坑,以及猪槽井洞穴系统中潜在的洞穴崩塌大厅.这3个地方似乎可以说明天坑的演化顺序,即天坑从多重洞穴崩塌,到最后退化成大型漏斗的过程.  相似文献   

Modeling estuarine nutrient geochemistry in a simple system     

Lisa Wells Kaul  Philip N. Froelich 《Geochimica et cosmochimica acta》1984,48(7):1417-1433

We present a model of estuarine mixing, removal, and input for dissolved constituents, and apply the model to 39 nutrient (P, N, Si) profiles collected over a 14-month period in a pristine river/ estuary: Ochlockonee Bay, Florida. Each profile is deconvolved into three component functions: linear mixing (conservative) first-order removal (biological productivity), and parabolic input (regeneration). After correction for temporal variations in the fluvial end-members, the model provides quantitative estimates of total estuarine primary production, net regeneration, and subsequent fluxes to the ocean over a year-long period. The modeled data set is internally self-consistent: virtually perfect mass balances are obtained for P and Si. All biological P-uptake is regenerated within the estuary so that virtually 100% of the fluvial reactive-P enters the ocean. One-third of the fluvial reactive-P enters the estuary as particles whose phosphate is released after deposition in estuarine sediments. About 20% of the dissolved fluvial silica flux is removed biologically; all of this biogenic silica dissolves in the estuary and enters the ocean. N cannot be mass balanced, probably because it enters and escapes the bay in unmeasured forms (as NH₄ or via denitrification to N₂ and N₂O). In the Ochlockonee, biological productivity removes nutrients in the ratios N:P ? 9:1 and Si:P ? 20:1.  相似文献   

Influence of Venezuelan crude oil on lobster larvae     

P.G. Wells 《Marine pollution bulletin》1972

Emulsions of crude oil are lethal to larvae of the American Iobster at concentrations of 100 ppm and appear to have sublethal effects at concentrations down to 1 ppm.  相似文献   

Nematode/copepod ratios for monitoring pollution: A rebuttal     

B.C Coull  G.R.F Hicks  J.B.J Wells 《Marine pollution bulletin》1981,12(11):378-381

The nematode/copepod ratio recently proposed by Raffaelli & Mason is not a valid tool for assessing pollution. We found many discrepancies in the original paper and felt obliged to point them out. There was no quantitative assessment of contagion; and seasonal variation was great, two factors which could alter the ratio. We partitioned the original data into Raffaelli & Mason's and others and found that the ratio was not significantly correlated with grainsize when using the literature values. There are several exceptions to their statement that nematodes dominate in organically enriched sites and that there are not copepods in deep water samples. We do not believe that reducing the very complex meiofaunal community structure to a single ratio is appropriate and are concerned that those not familiar with the meiofaunal literature will try to use this ratio method as a panacea for assessing pollution before its validity is fully known.  相似文献   

On the use of the nephelometer in estuarine waters     

Andrew Eaton  Virginia Grant  Owen Bricker  Darlene Wells 《Estuaries and Coasts》1981,4(4):379-384

A study of the problems encountered in nephelometric determinations of suspended sediment loads in the Chesapeake Bay estuary has led to development of a technique which uses nephelometer readings as a guide for sampling at vertical profiles in an estuary. This permits optimum sampling for concentration profiles and allows one to use nephelometer/load ratios to characterize particles.  相似文献   

Sources of uncertainty in projections of twenty-first century westerly wind changes over the Amundsen Sea,West Antarctica,in CMIP5 climate models     

Thomas J. Bracegirdle  John Turner  J. Scott Hosking  Tony Phillips 《Climate Dynamics》2014,43(7-8):2093-2104

The influence of changes in winds over the Amundsen Sea has been shown to be a potentially key mechanism in explaining rapid loss of ice from major glaciers in West Antarctica, which is having a significant impact on global sea level. Here, Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model data are used to assess twenty-first century projections in westerly winds over the Amundsen Sea (U _AS ). The importance of model uncertainty and internal climate variability in RCP4.5 and RCP8.5 scenario projections are quantified and potential sources of model uncertainty are considered. For the decade 2090–2099 the CMIP5 models show an ensemble mean twenty-first century response in annual mean U _AS of 0.3 and 0.7 m s^?1 following the RCP4.5 and RCP8.5 scenarios respectively. However, as a consequence of large internal climate variability over the Amundsen Sea, it takes until around 2030 (2065) for the RCP8.5 response to exceed one (two) standard deviation(s) of decadal internal variability. In all scenarios and seasons the model uncertainty is large. However the present-day climatological zonal wind bias over the whole South Pacific, which is important for tropical teleconnections, is strongly related to inter-model differences in projected change in U _AS (more skilful models show larger U _AS increases). This relationship is significant in winter (r = ?0.56) and spring (r = ?0.65), when the influence of the tropics on the Amundsen Sea region is known to be important. Horizontal grid spacing and present day sea ice extent are not significant sources of inter-model spread.  相似文献   

A modeling study of coastal inundation induced by storm surge,sea-level rise,and subsidence in the Gulf of Mexico   总被引：2，自引：2，他引：0  

Zhaoqing Yang  Taiping Wang  Ruby Leung  Kathy Hibbard  Tony Janetos  Ian Kraucunas  Jennie Rice  Benjamin Preston  Tom Wilbanks 《Natural Hazards》2014,71(3):1771-1794

The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a “change of inundation depth” parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and subsidence, and that responses of storm surge and coastal inundation to the effects of sea-level rise and subsidence are highly nonlinear and vary on temporal and spatial scales.  相似文献