Levels of tin in core sediments along the Alexandria Coast, Egypt

Tin concentrations were determined in surface and core sediments from three hot spots along the Alexandria coast, namely: Abu-Qir Bay, Eastern Harbour, and Western Harbour. The mean concentrations in surface sediment were 2.434, 3.212, and 5.572 μg/g dry weight for Abu-Qir Bay, Eastern Harbour, and Western Harbour, respectively. A sharp decrease in tin level in core sediments with depth was observed in almost all locations except for core 4 in Abu-Qir Bay and core 17 in the Eastern Harbour, where the sub-sample at the 5 cm level recorded the highest tin concentrations.     

Pollutants and the health of green sea turtles resident to an urbanized estuary in San Diego, CA

Rapid expansion of coastal anthropogenic development means that critical foraging and developmental habitats often occur near highly polluted and urbanized environments. Although coastal contamination is widespread, the impact this has on long-lived vertebrates like the green turtle (Chelonia mydas) is unclear because traditional experimental methods cannot be applied. We coupled minimally invasive sampling techniques with health assessments to quantify contaminant patterns in a population of green turtles resident to San Diego Bay, CA, a highly urbanized and contaminated estuary. Several chemicals were correlated with turtle size, suggesting possible differences in physiological processes or habitat utilization between life stages. With the exception of mercury, higher concentrations of carapace metals as well as 4,4′-dichlorodiphenyldichloroethylene (DDE) and γ chlordane in blood plasma relative to other sea turtle studies raises important questions about the chemical risks to turtles resident to San Diego Bay. Mercury concentrations exceeded immune function no-effects thresholds and increased carapace metal loads were correlated with higher levels of multiple health markers. These results indicate immunological and physiological effects studies are needed in this population. Our results give insight into the potential conservation risk contaminants pose to sea turtles inhabiting this contaminated coastal habitat, and highlight the need to better manage and mitigate contaminant exposure in San Diego Bay.     

Polychlorinated naphthalenes (PCNs) in riverine and marine sediments of the Laizhou Bay area, North China

PCN congeners were analyzed in marine and riverine sediments of the Laizhou Bay area, North China. Concentrations of PCNs ranged from 0.12 to 5.1 ng g⁻¹ dry weight (dw) with a mean value of 1.1 ng g⁻¹ dw. The levels of PCNs varied largely, with industrial group approximately ten folds higher than those of the rural in riverine sediment. A strong impact by direct discharge from local factories was suggested. Similar compositional profiles were found within groups. High resemblance of compositional profiles between industrial samples and Halowax 1014 was observed. It was indicated that PCNs in riverine sediments were mainly from release of industrial usage, with additional contributions from industrial thermal process at certain sites. In marine sediments, it was suggested that PCNs along the coast of Laizhou Bay were mainly controlled by riverine input. While in the central bay, PCN distributions were possibly impacted by combined multiple factors.     

Methylmercury and total mercury in estuarine organisms from Rio de Janeiro, Brazil

Guanabara Bay (GB), located in the Rio de Janeiro State, is still a productive estuary on the south-eastern Brazilian coast. It is an ecosystem heavily impacted by organic matter, oil and a number of other toxic compounds, including Hg. The present study aimed to comparatively evaluate the aquatic total mercury (THg) and MeHg contamination, and the ratios of MeHg to THg (% MeHg), in 3 species of marine organisms, Micropogonias furnieri-carnivorous fish (N = 81), Mugil spp.--detritivorous fish (N = 20) and Perna perna--filter-feeding bivalves (N = 190), which are widely consumed by the population. A total of 291 specimens were collected at the bay in different periods between 1988 and 1998. THg concentrations were determined by cold vapour AAS with stannous chloride as a reducing agent. MeHg was extracted by dithizone-benzene and measured by GC-ECD. Analytical quality was checked through certified standards. All organisms presented both low THg and MeHg concentrations and they were below the maximum limit of 1,000 micrograms Hg.kg-1 wet wt. as established for human intake of predatory fish by the new Brazilian legislation. Carnivorous fish showed higher THg and MeHg concentrations, and also % MeHg in muscle tissues, than organisms with other feeding habits and lower trophic levels. The average of THg concentrations in carnivorous fish was 108.9 +/- 58.6 micrograms.kg-1 wet wt. (N = 61) in 1990 and 199.5 +/- 116.2 micrograms.kg-1 wet wt. (N = 20) in 1998, but they presented different total length and body weights. The average THg content in detritivorous fish was 15.4 +/- 5.8 micrograms.kg-1 wet wt., whereas THg concentrations ranged from 4.1 to 53.5 micrograms.kg-1 wet wt. for the molluscs. The THg and MeHg contents of mussel varied according to the sampling point and water quality. MeHg concentration in detritivorous fish was similar to MeHg concentration in molluscs, but there was a significant difference in the MeHg/THg ratio: the carnivorous fish presented higher MeHg percentages (98%) than the detritivorous fish (54%) and the molluscs (33%). Weight-normalised average concentration of THg in carnivorous fish collected in 1990 (0.18 +/- 0.08 microgram.g-1/0.7 kg wet wt.) and in 1998 (0.16 +/- 0.09 microgram.g-1/0.7 kg wet wt.) presented no significant difference (t = 1.34; P < 0.5). In conclusion, the low THg and MeHg concentrations in the organisms from the GB ecosystem, are related to its eutrophic conditions and elevated amounts of suspended matter. In this situation, Hg could be strongly complexed or adsorbed by the particulate, which would dilute the Hg inputs and reduce its residence time in the water column, with a consequent decrease in its availability to organisms.     

Changes Of Hydrological Environment And Their Influences On Coastal Wetlands InThe Southern Laizhou Bay, China

The structure and function of the coastal wetland ecosystem in the southern Laizhou Bay have been changed greatly and influenced by regional hydrological changes. The coastal wetlands have degraded significantly during the latest 30 years due to successive drought, decreasing of runoff, pollution, underground saline water intrusion, and aggravating marine disasters such as storm tides and sea level rising. Most archaic lakes have vanished, while artificial wetlands have been extending since natural coastal wetlands replaced by salt areas and ponds of shrimps and crabs. The pollution of sediments in inter-tidal wetlands and the pollution of water quality in sub-tidal wetlands are getting worse and therefore “red tides” happen more often than before. The biodiversity in the study area has been decreased. Further studies are still needed to protect the degraded coastal wetlands in the area.     

New Technology for Conducting Radiation Hazard Assessments: The Application of the Underwater Radiation Spectral Identification System (URSIS) at the Massachusetts Bay Industrial Waste (U.S.A.)

The Underwater Radiation Spectral Identification System (URSIS) is a portable spectrometer used for the in situ detection of radioactivity in the marine environment. This paper reports on the first time application of this technology to assess, in a preliminary manner, the potential radiation threat to the public and environment at an aquatic disposal site – the Massachusetts Bay Industrial Waste Site (IWS). Utilizing the meneuvering capabilities of ROV and manned submersible vehicles, the URSIS was successfully positioned close (5–10 cm) to waste containers for a period sufficient to detect, in real time, the presence of radioactive materials. Spectral data from 45 individual targets indicated that the radionuclides present in sediments which draped or partially buried waste containers were consistent with natural background concentrations. No man-made radionuclides were detected at any of the target or background measurement locations. These data support the conclusion that low-level radiation does not pose an imminent and widespread human health or ecological threat in Massachusetts Bay.     

Status and Trends of Dissolved Oxygen in Corpus Christi Bay, Texas, U.S.A.

The purpose of this studywas to determine status and long-term trends of dissolved oxygen concentrations (DO) in Corpus Christi Bay, Texas, U.S.A. A 20-year record of randomized stations was used to determine the trend of surface water DO, salinity, and temperature over space and time. A 13-year record of two fixed stations was used to determine the temporal nutrient trends. A 10-year record of fixed stations in the southeastern region of Corpus Christi Bay was used to determine the status of disturbance caused by low DO in bottom waters. From 1982 to 2002, there was a significant decrease in surface water DO at a rate of 0.06 mg L⁻¹ yr⁻¹ and a significant increase in surface water temperature at a rate of 0.07°C yr⁻¹. The southeastern region of Corpus Christi Bay had the lowest average DO, and during July and August, DO are steadily declining at a rate of 0.09 mg L⁻¹ yr⁻¹. It is not likely that eutrophication is causing hypoxia, because freshwater inflow rates have significantly decreased since 1941 and nutrient levels have not changed from 1987 to 2000. Even though long-term trends indicate that average surface DO is decreasing, disturbance by hypoxia appears to be stable, but this may be due to just eight years of data. In fact, if the current trend continues, surface water DO will not meet exceptional aquatic life standards (≤5 mgL⁻¹) in 2032.     

Application of the benthic index of biotic integrity to environmental monitoring in Chesapeake Bay

The Chesapeake Bay benthic index of biotic integrity (B-IBI) was developed to assess benthic community health and environmental quality in Chesapeake Bay. The B-IBI provides Chesapeake Bay monitoring programs with a uniform tool with which to characterize bay-wide benthic community condition and assess the health of the Bay. A probability-based design permits unbiased annual estimates of areal degradation within the Chesapeake Bay and its tributaries with quantifiable precision. However, of greatest interest to managers is the identification of problem areas most in need of restoration. Here we apply the B-IBI to benthic data collected in the Bay since 1994 to assess benthic community degradation by Chesapeake Bay Program segment and water depth. We used a new B-IBI classification system that improves the reliability of the estimates of degradation. Estimates were produced for 67 Chesapeake Bay Program segments. Greatest degradation was found in areas that are known to experience hypoxia or show toxic contamination, such as the mesohaline portion of the Potomac River, the Patapsco River, and the Maryland mainstem. Logistic regression models revealed increased probability of degraded benthos with depth for the lower Potomac River, Patapsco River, Nanticoke River, lower York River, and the Maryland mainstem. Our assessment of degradation by segment and water depth provided greater resolution of relative condition than previously available, and helped define the extent of degradation in Chesapeake Bay.     

Rookery Bay and Naples Bay circulation simulations: Applications to tides and fresh water inflow regulation

A three-dimensional, baroclinic numerical circulation model is applied to the combined Rookery Bay and Naples Bay estuary complex. We focus on two aspects of the model simulations: the tidal circulation, for which we have observations of sea level and currents at several stations spanning Rookery Bay, and the salinity variations, for which we have observations at one station. After establishing model veracity through quantitative comparisons with observations, we use the model to address salinity changes that could arise due to regulatory fresh water flow rate modifications. Two different sets of experiments are performed. The first considers the salinity changes in Rookery Bay by increasing the fresh water flow rates into Henderson Creek through the addition of either 1.4 m³/s or 2.8 m³/s to the ambient flow rates. The second considers the salinity changes in Naples Bay by decreasing the fresh water flow rates through the subtraction of 9.9 m³/s from the Golden Gate Canals’ ambient flow rates. All of these scenarios result in significant, quantifiable salinity changes within the Rookery Bay and Naples Bay estuary complexes, demonstrating the environmental management utility of using high resolution, three-dimensional, numerical circulation models, as applied herein, for assessing the water properties of complex, multi-connected estuarine systems.     

Sea level rise and eelgrass (Zostera marina) production: A spatially explicit relative elevation model for Padilla Bay, WA

The dynamics that govern the elevation of a coastal wetland relative to sea level are complex, involving non-linear feedbacks among opposing processes. Changes in the balance between these processes can result in significant alterations to vegetation communities that are adapted to a specific range of water levels. Given that current sedimentation rates in Padilla Bay, Washington are likely less than historical levels and that eustatic sea level rise is accelerating, the extensive Zostera marina (eelgrass) meadows in the bay may be at risk of eventual submergence. We developed a spatially explicit relative elevation model and used it to project changes in the productivity and distribution of eelgrass in Padilla Bay over the next century. The model is mechanistic and incorporates many of the processes and feedbacks that govern coastal wetland elevation change. Accretion estimates made using ²¹⁰Pb dating of sediment cores, sediment characteristics measured within cores, and eelgrass productivity and decomposition data were used to initialize and calibrate the model. Validation was performed using an elevation change rate measured with a network of surface elevation tables. Both the field data and model simulations revealed a net accretion deficit for the bay. Simulations using current rates of sea level rise indicated an overall expansion of eelgrass within Padilla Bay over the next century as it migrates from the center of the bay shoreward.