Sources and Distribution of Heavy Metals in East China Sea Surface Sediments

Box cores and surficial sediments collected from the shelf, slope and Okinawa Trough of the East China Sea were analyzed for loss on ignition, and concentration and speciation of Al, Fe, Mn, Pb, Cd, Cu and Zn. in general, concentrations of these metals are higher in the inner shelf and lower in the midshelf, but the highest LOI, Cd and Mn levels are found in the Okinawa Trough. Spatial distributions of these metals in surficial sediments indicate that the Yangtze River is the major source for materials deposited in the inner shelf. the results of a six-stage sequential leaching experiment indicate that the fluvial input includes natural (e.g., Al and Fe) and anthropogenic (e.g., Pb) materials. the depletion concentration of these metals in the midshelf sediments reflects the dominance (～ 70%) of coarse, relict sand, while the enrichments in the inner shelf and the Okinawa Trough sediments are due to the fine grained, organic-rich sediments. the speciation of Mn in the sediments of the Okinawa Trough indicates that its distribution is diagentically or hydrothermally controlled.     

Particulate Organic Matter Composition in A Semi-Enclosed Marine System

Spatial and temporal changes in the biochemical composition of particulate organic matter in a semi-enclosed marine system (Stagnone di Marsala, Mediterranean Sea) were studied, on a monthly basis, from January to December 1994, in order to assess nutritional value of suspended particles for benthic suspension feeders. According to previous findings, the study site displayed a strong oligotrophy. Chlorophyll-a accounted for a very low fraction of the total suspended matter pool (0.1%), whereas at least 75% of POC was of detrital/heterotrophic origin. POC: PON ratio values indicate that bacterioplankton biomass accounted for a significant fraction of the total POC pool, displaying values comparable to those of the phytoplankton biomass (phytoplankton to bacterial biomass ratio was about (1). Temporal and spatial changes in the biochemical composition of particulate organic matter were rather limited and related to its sources, the main of which is represented by detrital particles released by the Posidonia oceanica (L.) beds. the comparison between our results and those encountered in other coastal lagoons indicates that the low abundance of suspension-feeding organisms observed in the study area is related to the “quality depression” of particles due to the dilution of high quality compounds (i.e., biopolymeric carbon) in a largely inorganic matrix. This result leads us to conclude that, to reach the same amount of high quality particulate food, a suspension feeder mollusc in the Marsala lagoon would need to filter a sea water volume around 3 times higher than in other Mediterranean coastal lagoons.     

Prospects for Development of an Index of Biotic Integrity for Evaluating Habitat Degradation in Coastal Systems

A multivariate index for assessment of habitat quality and its degradation, the Index of Biotic Integrity (IBI), has been developed for stream fish communities. the extension of the IBI concept to coastal waters is proposed by the development of an estuarine IBI based on macrobenthos and submerged aquatic vegetation. Eleven variables are proposed for inclusion in this index, although further consideration of the appropriateness of several variables is required. It is concluded that development of an IBI for coastal systems is feasible.     

Marine Organisms as Indicators of Heavy Metal Pollution-Experience from 16 Years of Monitoring at a Lead Zinc Mine in Greenland

In monitoring the impact of a lead-zinc mine in Greenland, species of fish, prawns, seaweed and mussels have been analysed for cadmium, copper, lead and zinc for several years. These metals have been released to the marine environment in significant amounts from the mining operation.     

Radioactive Contamination in the Italian Seas: An Overview Also in the Light of the European Marina-Med Project

Following a similar project performed for the Northern European Seas in the years 1985–1990, a study on the radioactive contamination of the Mediterranean Sea has recently been conducted by a group of experts of the European Union (MARINA-MED Project). Its aim was to assess the radiological exposure of the population of the European Union, due both to natural and man-made radionuclides in the Mediterranean Sea. A review of the conclusions of this study is presented, with special attention to the environmental radioactive data. the Italian radioactive monitoring organisation is described. Starting from this experience, some proposals for new research projects are presented.     

Horizontal Distribution of Some Artificial Radionuclides in Sediments Collected Off the Rhone Mouth (Gulf of Lions-Mediterranean Sea)

Abstract

The Rhône delta is a typical microtidal estuary. River runoff spreads out into the Gulf of Lions as a surface plume influenced by the prevailing N or NW wind and the Liguro-Provençal-Catalan current. in the prodelta, sediments form a filter that traps radionuclides released by the different nuclear installations on the Rhône River and which are associated with fine particles. the horizontal distribution of various artificial radionuclides shows the highest concentrations at the Rhône River mouth. There,¹³⁷Cs reaches 86.6 and 94.4 Bq·kg^?1 dry wt. and is still present 10 miles away (32.5 Bq·kg^?1 dry wt.) in the southwestward direction (influence of the general circulation). Data obtained in the sediment at Roustan station between 1980 and 1990 show that in 1990, ¹³⁷Cs levels were similar to those found previous to the Chernobyl accident.     

A general process-based mass-balance model for phosphorus/eutrophication as a tool to estimate historical reference values for key bioindicators,as exemplified using data for the Gulf of Riga

This work describes how a general, process-based mass-balance model (CoastMab) for phosphorus for coastal areas may be used as a tool to estimate realistic values of “natural” or preindustrial reference levels of key bioindicators in coastal science, including the Secchi depth, a standard measure of water clarity, the chlorophyll-a concentration, an operational measure of phytoplankton biomass and the concentration of cyanobacteria, a measure of the concentration of harmful algae. The CoastMab-model is an ecosystem model giving monthly predictions to achieve seasonal variations of basin-wide properties. The selected case-study area, the Gulf of Riga, is sensitive to nutrient loading because of its shallowness and low openness towards the Baltic Proper. The morphometry of any coastal area, as given by the size and form parameters, influences all internal processes, such as sedimentation, resuspension, diffusion in water and from sediments to water, biouptake and retention in biota, stratification, mixing and outflow. There has been no mass-balance modeling for nitrogen (N) in this work because empirical data (from the HELCOM database) clearly indicate that the monthly primary production in the Gulf of Riga is regulated by phosphorus (P) – the mean monthly total-N to total-P ratios are well over 7.2 (the Redfield-ratio) and generally higher than 15 for the data used in this study (from 1992 to 2005). At present anthropogenic loads, the average modeled monthly values for Secchi depth, chlorophyll (Chl), cyanobacteria (CB) and total-P (TP) are 3.2 m, 3.8 μg/l, 78 μg/l and 31.3 μg/l, respectively. If 50% of all anthropogenic sources to the Gulf of Riga via rivers, point sources and diffuse sources were to be removed, these values would be 3.6 m, 3.4 μg Chl/l, 63 μg CB/l and 29.1 μg TP/l. If 60% of the anthropogenic phosphorus fluxes to the Baltic Proper were to be omitted and as well as 75% of all direct anthropogenic sources to the Gulf of Riga, the values would be 4.6 m, 2.7 μg Chl/l, 45 μg CB/l and 25.4 μg TP/l. These values represent the “natural” reference levels and it is not realistic to expect that remedial measures would improve the conditions more than that. Using the CoastWeb-model, similar calculations can be made for any given coastal area and the data necessary for such calculations are discussed in this work.     

Mechanisms of moisture stress in a mid-latitude temperate forest: Implications for feedforward and feedback controls from an irrigation experiment

While it is well established that stomata close during moisture stress, strong correlations among environmental (e.g., vapor pressure deficit, soil moisture, air temperature, radiation) and internal (e.g., leaf water potential, sap flow, root-shoot signaling) variables obscure the identification of causal mechanisms from field experiments. Models of stomatal control fitted to field data therefore suffer from ambiguous parameter identification, with multiple acceptable (i.e., nearly optimal) model structures emphasizing different moisture status indicators and different processes. In an effort to minimize these correlations and improve parameter and process identification, we conducted an irrigation experiment on red maples (Acer rubrum L.) at Harvard Forest (summers of 2005 and 2006). Control and irrigated trees experienced similar radiative and boundary layer forcings, but different soil moisture status, and thus presumably different diurnal cycles of internal leaf water potential. Measured soil moisture and atmospheric forcing were used to drive a transient tree hydraulic model that incorporated a Jarvis-type leaf conductance in a Penman–Monteith framework with a Cowan-type (resistance and capacitance) tree hydraulic representation. The leaf conductance model included dependence on both leaf matric potential, Ψ_L (so-called feedback control) and on vapor pressure deficit, D (so-called feedforward control). Model parameters were estimated by minimizing the error between predicted and measured sap flow. The whole-tree irrigation treatment had the effect of elevating measured transpiration during summer dry-downs, demonstrating the limiting effect that subsurface resistance may have on transpiration during these times of moisture stress. From the best fitted model, we infer that during dry downs, moisture stress manifests itself in an increase of soil resistance with a resulting decrease in Ψ_L, leading to both feedforward and feedback controls in the control trees, but only feedforward control for the irrigated set. Increases in the sum-of-squares error when individual model components were disabled allow us to reject the following three null hypotheses: (1) the f(D) stress is statistically insignificant (p = 0.01); (2) the f(Ψ_L) stress is statistically insignificant (p = 0.07); and (3) plant storage capacitance is independent of moisture status (p = 0.07).     

Quantifying the dynamics of marine invertebrate metacommunities: What processes can maintain high diversity with low densities in the Mediterranean Sea?

The Mediterranean Sea hosts 5.6% of the world benthic invertebrate species on 0.82% of the ocean surface. Mediterranean ecosystems are also characterized by low densities (and biomasses) compared to other oceanic ecosystems, a feature often attributed to their oligotrophic environment. Oligotrophic conditions can induce lower growth rates and higher mortality rates, and a stronger competition for food between individuals. A theoretical model was developed in order to study the diversity vs. density patterns in coastal benthic invertebrate species. This model describes their minimal population dynamics including basic processes (growth, mortality, reproduction and effects of competitive interactions between individuals) and incorporating fluxes of larvae (finally recruited as juveniles) between a mosaic of local habitats. Populations are therefore structured in a metacommunity. The connectivity between local communities is ensured by passive pelagic larval dispersal. In the Mediterranean Sea, because of the microtidal regime, the connectivity between coastal habitats is lower and more variable than in macrotidal basins. Mathematical properties of the model revealed that competitive interactions (intra- and interspecific competitions) have a stabilizing effect on interacting organisms when gains by recruitment are higher than losses by mortality. In addition, low mortality rates and low connectivity which decreases negative local interactions maintains high regional species diversity with low local densities. This property suggested that oligotrophy cannot be the only factor leading to the high diversity–low density pattern observed in the Mediterranean Sea.     

Ecological risks of polycyclic aromatic hydrocarbons found in coastal sediments along the northern shores of the Bohai Sea (China)

The total concentrations of 16 United States Environmental Protection Agency (US EPA)-listed polycyclic aromatic hydrocarbons (PAHs) found in coastal and estuarine sediments along the northern shores of the Bohai and Yellow Seas, China, at any study location varied from 0.236 to 8.34 nM g^?1 dry weight (dw). For a given PAH, concentrations varied by one to two orders of magnitude. Ecological risk assessments based on biota–sediment accumulation factors (BSAFs) indicated that the potential ecological hazard of PAHs in the sediments was limited. The average total sediment PAH concentrations were less than the effects range low, indicating that PAHs currently present in the sediments were not harmful to aquatic organisms. The estimated PAH concentration in the aquatic organisms was 0.223 nM g^?1 and posed a limited threat to human health via biological concentration from sediment to harvest of the sea. Assuming no additional PAH inputs, 99% of the 16 PAH molecules currently present in the sediments would be degraded in 40 years.