Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m-2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m-2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H', Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-mzone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997–1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system

Site-specific sediment quality values for the Gulf of Cádiz (Spain) and San Francisco bay (USA), using the sediment quality triad and multivariate analysis

 Sediment quality values need to be developed to help protect public health and the environment. Data derived from sediment chemistry, sediment toxicity tests and macrobenthic infaunal community structure from two separate integrative studies (sediment quality triad) conducted in the Gulf of Cádiz and in San Francisco Bay were analyzed by multivariate statistical techniques (principal component analysis [PCA] and factor analysis) to identify the concentration ranges of the chemicals associated with adverse effects. Application of PCA-factor analysis to the data matrix for the Gulf of Cádiz showed that the three data types could be represented by five principal factors, whereas for San Francisco Bay, there were four principal factors. These factors, as well as chemical concentrations and biological effects, were used to establish site-specific sediment quality values for each area studied. Positive prevalence of these factors in the cases studied (seven stations in the Gulf of Cádiz and nine in San Francisco Bay) was used to establish the ranges of chemical concentrations associated with adverse effects. The values proposed for the Gulf of Cádiz, in terms of concentrations at or below which biological effects have been shown to be minimal, are (in mg kg–1 of dry sediment): chromium, 101.2; lead, 66.8; linear alkylbenzenesulphonate, 12.8; silver, 1.2; and mercury, 0.46. The values proposed for San Francisco Bay are (in mg kg–1 of dry sediment): zinc, 156; chromium, 110; nickel, 88; copper, 68; arsenic, 58; lead, 49; tin, 8.0; silver, 4.0; mercury, 0.37; PCBs, 0.057; and DDTs, 0.00224

CH4 and N2O may contribute more to greenhouse effect than CO2 emission from the SCS

The South China Sea (SCS) is the largest marginal sea in the world. It is now apparent that in summer tropical seas, such as the SCS, are either close to neutral or are a small source of CO2 to the atmosphere. Methane (CH4) and nitrous oxide (N2O), however, are clearly much more supersaturated in the SCS. In the case of the SCS, the CH4 and N2O released from the surface waters contribute about three times as much to the greenhouse effect as CO2 does. In addition, abnormally high subsurface CH4 concentrations were found on the continental slopes in the northern SCS, as CH4 have been released from sediments and/or may have originated in CH4 gas hydrates. CH4 gas hydrates might become an important source of energy in the future. However, will the buried CH4 be released either due to the warming of the seawater, the internal waves, tropical storms or other disturbances? It may compound the severity of global warming

Deriving sediment quality guidelines in the Guadalquivir estuary associated with the Aznalcollar minig spill: A comparison of different approaches

Concentrations of heavy metals (Fe, Zn, Cd, Pb, Cu and Mn) and sediment toxicity tests (mortality of amphipods, Ampelisca brevicornis, of clams, Scrobicularia plana, and of fish, Solea senegalensis) were used to derive sediment quality guidelines (SQGs). The approaches are based on the determination of LC50, on the application of a multivariate analysis (MAA), and on the Threshold Effect Level Quotients (TELQs). All approaches lead to consistent SQGs. The range of concentrations established with MAA results in narrower uncertainty ranges. Sediment toxicity estimated by TELQs is in good agreement with that determined experimentally. In terms of the toxic mud concentration, the maximum and minimum LC50s (for fish EC50s) are 1.07% and 0.44% for amphipods, 5.75% and 1.25% for clams, and 7.24% and 1.97% for fish, based on dry weight. However, heavy metal concentrations or ranges should be used only as a first tier in a "weight-of-evidence" approach to determine the environmental quality in aquatic systems. The use of SQGs for the management of these systems should be taken with care, especially those used for the management of dredging processes

Evaluation of the toxicity of an oil spill conducted through bioassays using the fish Solea senegalensis

The toxicity produced by fuel pollutants was evaluated through bioassays using the Senegalese sole Solea senegalensis. Juveniles were exposed for 21 days to different dilutions obtained by mixing fuel extracted from the Prestige oil tanker and sediment from a clean area of Cádiz Bay. After the exposure period, three biomarkers were analyzed (7-ethoxyresorufin-Odeethylase [EROD], glutathione S-transferase [GST], and glutathione reductase [GR] enzymatic activity), as well as the histopathology of two of the main target organs (gills and liver). Significant (P < 0.05) biomarker inductions were observed in the exposed fish analyzed on day 21 relative to the control group (day zero). Lesions were detected in both organs studied, but the liver was the most affected. The frequency of appearance of the lesions was greater in the samples containing higher concentrations of polycyclic aromatic hydrocarbons (PAHs) and metals. The results showed significant correlations between the total PAH concentrations and GST, GR, and EROD enzymatic activity, with correlation coefficients of R = 0.96 for GST, R = 0.82 for GR, and R = 0.60 for EROD.

Benthic community structure and biomarker responses of the clam Scrobicularia plana in a shallow tidal creek affected by fish farm effluents (Rio San Pedro, SW Spain).

The effects of solid organic wastes from a marine fish farm on sediments were tested using benthic community as ecological indicators and biomarkers in native clam (Scrobicularia plana) as biochemical indicators. The benthic fauna and clam samples were collected in the intertidal sediment in October 2010 from five sites of the Rio San Pedro (RSP) creek, following a gradient of contamination from the aquaculture effluent to the control site. Numbers of species, abundance, richness and Shannon diversity were the biodiversity indicators measured in benthic fauna. Morphological and reproduction status of clams were assessed using the condition factor and gonado-somatic index, respectively. Phase I and Phase II detoxification enzymatic activities (ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST)), antioxidant enzymatic activities (glutathione peroxidase (GPX), glutathione reductase (GR)) and oxidative stress parameters (Lipid Peroxidation (LPO) and DNA strand breaks) were measured in clams' digestive gland tissues. In parallel, temperature and salinity in the adjacent water, redox potential, pH and organic matter in sediment, and dissolved oxygen in the interstitial water were measured. The results suggested that RSP showed a spatial gradient characterised by hypoxia/anoxia, reduced potential, acidic conditions and high organic enrichment in sediments at the most contaminated sites. Significant (p<0.05) decrease of biodiversity indicators were observed in the areas impacted by the aquaculture discharges. Biomarkers did not show a clear pattern and of all biochemical responses tested, GPX, DNA damage and LPO were the most sensitive ones and showed significant (p<0.05) increase in the polluted sites. Benthic biodiversity indicators were significantly (p<0.05) positively correlated with pH, redox potential and dissolved oxygen and negatively correlated with organic matter. On the contrary, antioxidant enzymatic responses (GPX) and oxidative stress parameters were significantly (p<0.05) negatively correlated with those physico-chemical parameters. It has been demonstrated that effluents from fish aquaculture activities in Rio San Pedro creek may produce an alteration of physicochemical characteristics of seabed and induce oxidative stress and DNA damage in soft-sediment species which may lead to changes of the benthic population structure and health status of the exposed organisms. (C) 2012 Elsevier Ltd. All rights reserved

Application of neutral red retention assay to caged clams (Ruditapes decussatus) and crabs (Carcinus maenas) in the assessment of dredged material.

Dredged material management is a key issue for the protection of aquatic environments. The in situ approach using caged bioindicator species has been chosen lately as a new methodology for the assessment of dredged material. In a tier testing approach, neutral red retention (NRR) assay has been applied as a screening tool to detect adverse changes in health status associated with contamination. Nevertheless, to authors' knowledge, little is known about the application and validation of this technique in sediment bioindicator species and under field conditions. Caged Ruditapes decussatus and Carcinus maenas were exposed during 28 days to potentially contaminated sediments at three sites in Algeciras Bay (SW Spain) and one site in C\ue1diz Bay (SW Spain). Lysosomal membrane stability was measured over time in haemolymph samples of exposed clams and crabs using the NRR assay. Sediment characterization of the study sites was performed in parallel. NRR time did not vary significantly (p > 0.05) over time in organisms from C\ue1diz Bay. Conversely, significant differences (p &lt; 0.05) in NRR time were found in clams and crabs exposed to sediments from Algeciras Bay, which exhibited a 30-70% decrease in haemocyte lysosome membrane stability compared to day 0. Statistical analysis showed a strong correlation between the drop of haemocyte lysosome membrane stability, in both crabs and clams, and the presence of metals (p &lt; 0.05) and PAHs (p &lt; 0.01) in the studied sediments. The results obtained confirmed the use of NRR assay as a suitable and sensitive method to be used in the assessment of sediment quality using as bioindicator species the clam R. philippinarum and the crab C. maenas

Interlaboratory assessment of marine bioassays to evaluate the environmental quality of coastal sediments in Spain. III. Bioassay using embryos of the sea urchin Paracentrotus lividus

 The present paper reports the results of an interlaboratory variability study of a bioassay using larval stages of the marine sea urchin Paracentrotus lividus. This exercise was developed in two different phases and included four laboratories, each of which determined the toxicity of six sediment samples. The samples were collected from different Spanish ports and were characterized by exposing sea urchin embryos for 48 h to sediment elutriates. Phase I was used to redesign test parameters and to avoid possible interfering factors when interpreting test results. Laboratories were more homogeneous in the classification of sediments according to the toxic responses in Phase II despite the high variability of the elutriate testing protocols. Based on our results, the test seems suitable to characterize dredged material, the interlaboratory variability being similar to that found for other bioassays in previous studies