Functional responses of filter feeders increase with elevated metal contamination: Are these good or bad signs of environmental health?

Fast urbanization in coastal areas has increased the load of contaminants entering estuaries worldwide, threatening the diversity and provision of services by these important systems. Contamination causes structural changes in ecosystems, but the consequences for their functioning are still overlooked. Here we investigated filtration and biodeposition rates of the mussel Mytilaster solisianus across different concentrations of metals, nutrients and suspended material, and levels of urbanization. As expected, filtration rates increased with the number of particles in the water column. However, in areas with low particle concentration, filtering increased in mussels with higher metal concentrations (Cu/Zn/Ni), which were, in turn, related to high urbanization. Similarly, biodeposition rates were positively related to metal concentration in mussels. The increased functional responses observed here is likely a symptom of stress, caused by potential compensatory mechanisms to the energetic costs of cell maintenance and body detoxification of mussels, rather than an indication of healthy systems/organisms. CAPSULE: Increased functional responses of mussels can be a sign of environmental stress.

Assessment and Ecological Risk of Heavy Metals in Sediment and Molluscs from the Mediterranean Coast

  Heavy metal contamination in both sediments and molluscs from the Egyptian Mediterranean coast was investigated. Seawater, sediments, and mollusc samples were collected from representative locations along the coastal area. Different representations of the data set, including, statistical methods (correlation matrix and cluster analyses), various sediment quality assessment methods, and bioaccumulation factor calculation, were combined to investigate the trends of heavy metals, identify pollution sources, and assess sediment quality from a toxicological point of view. The measurements of dissolved oxygen (DO) revealed to relatively well oxygenate surface water in all locations. There is a distinct change in the contents of heavy metals (Fe, Al, Zn, Cu, Ni, Cr, Pb, Cd, and Hg) among the sampling sediments. The statistical interpretations showed that the bio-availability of the studied heavy metals is controlled by different factors, including the geochemistry of sediments, the hydrology of the system, the uptake of metals from sediments, as well as human anthropogenic activities. Although, there are still certain points of the Egyptian Mediterranean coast with a relatively high concentration of toxic metals, the toxicological approach suggests that the risk for living organisms is not high, but, in the long run, toxicological implications can appear. These results can provide useful information for the local managers and decision makers.

Composition, Shell Strength, and Metabolizable Energy of Mulinia lateralis and Ischadium recurvum as Food for Wintering Surf Scoters (Melanitta perspicillata)

Decline in surf scoter (Melanitta perspicillata) waterfowl populations wintering in the Chesapeake Bay has been associated with changes in the availability of benthic bivalves. The Bay has become more eutrophic, causing changes in the benthos available to surf scoters. The subsequent decline in oyster beds (Crassostrea virginica) has reduced the hard substrate needed by the hooked mussel (Ischadium recurvum), one of the primary prey items for surf scoters, causing the surf scoter to switch to a more opportune species, the dwarf surfclam (Mulinia lateralis). The composition (macronutrients, minerals, and amino acids), shell strength (N), and metabolizable energy (kJ) of these prey items were quantified to determine the relative foraging values for wintering scoters. Pooled samples of each prey item were analyzed to determine composition. Shell strength (N) was measured using a shell crack compression test. Total collection digestibility trials were conducted on eight captive surf scoters. For the prey size range commonly consumed by surf scoters (6–12 mm for M. lateralis and 18–24 mm for I. recurvum), I. recurvum contained higher ash, protein, lipid, and energy per individual organism than M. lateralis. I. recurvum required significantly greater force to crack the shell relative to M. lateralis. No difference in metabolized energy was observed for these prey items in wintering surf scoters, despite I. recurvum’s higher ash content and harder shell than M. lateralis. Therefore, wintering surf scoters were able to obtain the same amount of energy from each prey item, implying that they can sustain themselves if forced to switch prey.

Sterols from Mytilidae show anti-aging and neuroprotective effects via anti-oxidative activity

For screening anti-aging samples from marine natural products, K6001 yeast strain was employed as a bioassay system. The active mussel extract was separated to give an active sterol fraction (SF). SF was further purified, and four sterol compounds were obtained. Their structures were determined to be cholesterol (CHOL), brassicasterol, crinosterol, and 24-methylenecholesterol. All compounds showed similar anti-aging activity. To understand the action mechanism involved, anti-oxidative experiments, reactive oxygen species (ROS) assays, and malondialdehyde (MDA) tests were performed on the most abundant compound, CHOL. Results indicated that treatment with CHOL increases the survival rate of yeast under oxidative stress and decreases ROS and MDA levels. In addition, mutations of uth1, skn7, sod1, and sod2, which feature a K6001 background, were employed and the lifespans of the mutations were not affected by CHOL. These results demonstrate that CHOL exerts anti-aging effects via anti-oxidative stress. Based on the connection between neuroprotection and anti-aging, neuroprotective experiments were performed in PC12 cells. Paraquat was used to induce oxidative stress and the results showed that the CHOL and SF protect the PC12 cells from the injury induced by paraquat. In addition, these substance exhibited nerve growth factor (NGF) mimic activities again confirmed their neuroprotective function.

Biomarkers of environmental stress in gills of ribbed mussel Aulacomya atra atra (Nuevo Gulf, Northern Patagonia)

In this study, we assessed in gills of native ribbed mussels Aulacomya atra atra from three sites within Nuevo Gulf (Northern Patagonia) several biomarkers such as reactive oxygen species (ROS), lipid radicals (LR), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and metallothionein (MT). Furthermore, concentrations of main trace metals (Fe, Al, Zn, Cu, Cd and Pb) were quantified in mussel tissue. Results showed significant induction of SOD, GST, MT and MDA, as well as, higher concentration of Fe, Al and Cd in winter than in summer. The high MDA content measured in mussels from Folías Wreck seemed to be caused by the very high levels of Fe that would come from the corrosion of the vessel. Mussels from the control site Punta Cuevas presented the lowest levels of Cd and the highest of Al in winter. Despite positive correlations were found between Al and GST and MT, no spatial differentiation was detected in those biomarkers. On the other hand, MT was only related to Al been most likely influenced by environmental variables than by the trace metals. It has to be highlighted that the relationship detected among water temperature, nutrients and antioxidant responses in gills is probably related to the fact that this tissue is in direct contact with water and it is sensitive to its fluctuations. Taking into account that mussel gill is a tissue actively proliferating and the first target of contaminants present in water, so that changes in its antioxidant system can provide an earlier warning signal than in other tissues.

Metal concentrations in the shell of Bathymodiolus azoricus from contrasting hydrothermal vent fields on the Mid-Atlantic Ridge

Specimens of Bathymodiolus azoricus were sampled along the Mid-Atlantic Ridge at the Menez Gwen, Lucky Strike and Rainbow hydrothermal fields. Individual shells (n = 51), through the weight range 0.62 to 15.70 g, were analyzed for their magnesium, strontium, iron, manganese, copper, zinc and cadmium concentrations. Amongst the marine molluscs the shell of B. azoricus is confirmed as being particularly impoverished in strontium (mean 943 microg g(-1)). Trace metal concentrations in the shells decreased in the order Fe> Mn> Zn> Cu> Cd. Despite originating from trace metal rich environments mean concentrations were low (37.9, 13.2, 10.7, 1.1 and 0.7 microg g(-1), respectively). Irrespective of geographical origin magnesium, strontium and copper concentrations were primarily dictated by shell weight. In contrast cadmium concentrations were elevated in shells from the Rainbow field and ambient seawater chemistry imparted site specific chemical fingerprints to the shells with respect to the iron to manganese ratio.

[Carbohydrate-binding proteins of marine invertebrates]

The information on the carbohydrate specificity and molecular organization of some carbohydrate-binding proteins (lectins) of marine invertebrates is reported. Antiviral activity of some of the lectins against human immunodeficiency virus has been studied. Lectins of marine invertebrates are promising tools for studying natural glycoconjugates and cell effectors in vitro.

A comparative assessment of heavy metal accumulation in soft parts and byssus of mussels from subarctic, temperate, subtropical and tropical marine environments

Existing data on metal concentrations in mussels from subarctic, temperate, subtropical and tropical waters were analyzed using multivariate statistics in order to assess regional variations in metal contamination. Potential errors were reduced by only analyzing data from surveys that employed the same protocols, analytical methodologies and analysts. Factor analysis demonstrated that mussels inhabiting extremely contaminated areas (e.g. from Japanese and Swedish metallurgy sources) could be separated from mussels from other contaminated areas, and that metals such as Cd, Pb, Cu and Zn could be used to identify heavily contaminated samples while Co, Fe, Cr and Ni concentrations were good markers for exposure to inputs from different industrial sources. Furthermore byssus, like soft tissue, selectively and sensitively reflects variations of certain metal concentrations in ambient waters and thus serves as a reliable biomonitor for these contaminants in a variety of coastal and estuarine areas.