Factors affecting RPSI in imposex monitoring studies using Nucella lapillus (L.) as bioindicator

Nucella lapillus (L.) is a marine gastropod mollusc widely used as a bioindicator of TBT pollution in the North Atlantic coastlines. The species reproductive cycle and the male penis length seasonal/spatial variation were studied at a single site at Aveiro seashore (NW Portugal) between December 2005 and June 2007. The main objective of this work is to assess if the "Relative Penis Size Index" (RPSI)--an important imposex assessment index--varies seasonally and spatially in the same sampling site and how this can affect results obtained in imposex monitoring programmes. Animals able to reproduce were found every month but a seasonal pattern in N. lapillus reproductive cycle was evident. Female gametogenic maturation varied seasonally and a decrease in capsule gland volume and condition factor occurred in late summer/early autumn. The gametogenesis in males did not show a significant seasonal variation as in females but the condition factor, penis length, amount of sperm and prostate volume also diminished in late summer/early autumn. On the other hand, males that were close to egg capsules clusters had larger penises than those far away from clusters. The temporal and spatial male penis length variation introduces a bias on imposex assessment results when using RPSI and the magnitude of the error involved is evaluated for different TBT pollution levels scenarios. We consider that RPSI provides interesting and complementary information that should not be excluded from monitoring programmes, but temporal or spatial comparisons of imposex should be based on other more reliable imposex indices like the VDSI.     

Heavy metals concentrations in zooplankton and suspended particulate matter in a southwestern Atlantic temperate estuary (Argentina)

The present work includes part of the first studies of metals concentrations in the zooplankton from a heavily industrialized estuary of Argentina, the Bahía Blanca estuary. Cd, Cu, and Pb concentrations in the zooplankton (macro- and mesozooplankton) and the suspended particulate matter were measured at stations with different degree of pollution. Physicochemical variables and zooplankton composition and abundance were also analyzed. Thus, the aim of the present work was to analyze the spatial and temporal distribution of heavy metals in these two different fractions, and the possible relation among them due to their importance in the biogeochemical cycles of marine environments. Samplings were carried out during a year, from March 2005 to April 2006, every 2 months, at stations located near chemical and petrochemical industries, stations far from these points and one station in an intermediate location. In the mesozooplankton, the mean concentrations of Cd, Cu, and Pb were 3.63?±?1.46, 34.46?±?5.40, and 11.54?±?3.04 μg?g^?1 dry weight (d.w.) respectively, while in the macrozooplankton, 3.20?±?2.28, 21.86?±?4.79, and 8.36?±?1.85 μg?g^?1 d.w. On the other hand, particulate Cd, Cu, and Pb presented a mean concentration of 3.33?±?1.22, 12.75?±?2.67, and 12.53?±?3.20 μg?g^?1 d.w., respectively. Metals’ levels in both the SPM and zooplankton fluctuated throughout the study time and were relatively high in the particulate phase especially for Cu and Pb. Moreover, zooplankton accumulated important concentrations of the three metals. The sources of them are probably the discharges of the industries and domestic sewages located near the estuary.     

Synergistic effects caused by atrazine and terbuthylazine on chlorpyrifos toxicity to early-life stages of the zebrafish Danio rerio

This study examined the effects of three widely used pesticides that have been previously detected in aquatic systems neighbouring agricultural fields on the early-life stages of the zebrafish Danio rerio. Tests involving single exposures and binary combinations of the s-triazine herbicides (atrazine and terbuthylazine) and the organophosphate insecticide chlorpyrifos were performed. Several endpoints, such as swimming behaviour, morphological abnormalities and mortality, were studied. In addition, the inhibition of acetylcholinesterase (AChE) activity was investigated in order to evaluate the mode of action and toxicity of chlorpyrifos in the presence of these herbicides. Results indicate that both binary mixtures elicited synergistic responses on the swimming behaviour of zebrafish larvae. Moreover, although the herbicides were not effective inhibitors of the AChE on their own, a synergistic inhibition of the enzyme activity was obtained by exposure to mixtures with chlorpyrifos. We observed a correlation between impairment of swimming behaviour of the larvae and inhibition of AChE activity. This study supports previous studies concerning the risk assessment of mixtures since the toxicity may be underestimated when looking only at the single toxicants and not their mixtures.     

Tipping Elements in the Arctic Marine Ecosystem

The Arctic marine ecosystem contains multiple elements that present alternative states. The most obvious of which is an Arctic Ocean largely covered by an ice sheet in summer versus one largely devoid of such cover. Ecosystems under pressure typically shift between such alternative states in an abrupt, rather than smooth manner, with the level of forcing required for shifting this status termed threshold or tipping point. Loss of Arctic ice due to anthropogenic climate change is accelerating, with the extent of Arctic sea ice displaying increased variance at present, a leading indicator of the proximity of a possible tipping point. Reduced ice extent is expected, in turn, to trigger a number of additional tipping elements, physical, chemical, and biological, in motion, with potentially large impacts on the Arctic marine ecosystem.     

Energy budget in <Emphasis Type="Italic">Daphnia magna</Emphasis> exposed to natural stressors

Background, aim, and scope  

Climate changes are nowadays an important issue of concern, and it is expected that in the near future it will be intensified, leading to extreme environmental conditions. These changes are expected to originate additional sources of stress; therefore, the exposure of organisms to natural stressors is receiving an increased importance in risk assessment. Organisms tend to avoid extremely environmental conditions looking for optimum conditions. This work aimed to evaluate the effects of natural stressors on the energetic reserves of Daphnia magna using the quantification of lipids, proteins, and sugars.     

Response of Holm oak (Quercus ilex subsp. ballota) and mastic shrub (Pistacia lentiscus L.) seedlings to high concentrations of Cd and Tl in the rhizosphere

The impairment of root growth and photosynthetical functioning are the main impacts of trace elements on woody plant seedlings. In this work, we assessed the response of Holm oak (Quercusilex subsp. ballota) and mastic shrub (Pistacia lentiscus) seedlings to high concentrations of Cd and Tl in the rhizosphere. These are non-essential trace elements, with a potential high mobility in the soil-plant system. Seedlings of these species are frequently used in the afforestation of degraded soils in mining areas. Plants were exposed to different levels of Cd (20, 80 and 200 mg L⁻¹) and Tl (2, 10 and 20 mg L⁻¹) in a sand culture. Biomass allocation, growth rates, chlorophyll fluorescence and gas exchange were studied. Both metals affected root biomass. Cadmium produced an increase in the root mass ratio and a decrease in the specific leaf area of the plants in oak seedlings, while Tl did not provoke such response. Mastic plants were more sensitive to Tl and Cd than oak plants. Between elements, Tl provoked more severe toxic effects in the plants, affecting the antennae complexes and reaction centers of the photosystem II. Both elements decreased net assimilation rates (down to a 20% of the control plants) and stomatal conductance (5-10% of the values for the control plants). Cadmium was highly retained in the roots of both species, while Tl was highly translocated into the leaves. In general, Holm oak showed a higher tolerance for Cd than for Tl, and a higher resistance to both metals than mastic shrub, due to a high capacity for Cd retention at the root level. However, such accumulation in roots may induce water stress in the seedling exposed to Cd.     

Cell size dependent toxicity thresholds of polycyclic aromatic hydrocarbons to natural and cultured phytoplankton populations

The toxicity of pyrene and phenanthrene to phytoplankton was studied by analyzing the effect on the growth, abundance and cell viability of cultured species and natural communities of the Atlantic Ocean and the Mediterranean Sea. A decrease in cell abundance, and growth rate was observed as concentration of PAHs increased, with catastrophic cell mortality induced at the highest PAH concentration tested. A strong positive linear relationship was observed between the LC50 (the PAH concentration at which cell population will decline by a half), and the species cell volume, for both phenanthrene and pyrene. Natural communities were however significantly more sensitive to PAHs than cultured phytoplankton, as indicated by the lower slope (e.g. 0.23 and 0.65, respectively, for pyrene) of the relationship LC50 vs. cell volume. The results highlight the importance of cell size in determining the phytoplankton sensitivity to PAHs identifying the communities from the oligotrophic ocean to be more vulnerable.     

Occurrence and sources of selected phenolic endocrine disruptors in Ria de Aveiro,Portugal

Background, aim and scope  

Ria de Aveiro (Portugal) is a shallow coastal lagoon of high economic and ecological importance. Hardly any data on its chemical pollution by polar organic pollutants are available in literature. This study focused on the presence and sources of a series of phenolic endocrine-disrupting compounds (EDCs) in this area, including parabens, alkylphenolic compounds and bisphenol-A (BPA). A number of possible sources of pollution are present in the area, including the large harbours present in the lagoon, the city of Aveiro and the rivers discharging into the area. A recently constructed submarine wastewater outfall, located a few kilometres from the lagoon inlet has also been suggested as a possible source of pollution to Ria de Aveiro in several publications. The aim of the current field study was to investigate the occurrence and main sources of phenolic endocrine disruptors in Ria de Aveiro.     

Assessment of water quality in the Alqueva Reservoir (Portugal) using bioassays

Background, aim, and scope  

Alqueva Reservoir is the biggest artificial freshwater reservoir in Europe and is an important water supply for human and agricultural consumption in the Alentejo region (Portugal). Pollution can impair environmental and human health status, and to assure water quality and ecological balance, it is crucial to frequently monitor water supplies. In this study, we used an ecotoxicological test battery to identify the potential toxicity of water from this reservoir.     

Biochemical responses of the marine mussel Mytilus galloprovincialis to petrochemical environmental contamination along the North-western coast of Portugal

Following the development of urban and industrial centres petrochemical products have become a widespread class of contaminants. The aim of this study was to investigate the effects of petrochemical contamination in wild populations of mussels (Mytilus galloprovincialis) along the NW Atlantic coast of Portugal by applying antioxidant and energetic metabolism parameters as biomarkers. For that, mussels were collected at five sampling sites presenting different petrochemical contamination levels. To evaluate the mussels' antioxidant status, enzymatic activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione S-transferases, as well as glutathione redox status were evaluated in gills and digestive glands of mussels collected from the selected sites. Lipid peroxidation was determined in the same tissues to quantify cellular oxidative damage. Furthermore, to investigate how energetic processes may respond to these contaminants, the activity of NADP(+)-dependent isocitrate dehydrogenase was determined in mussels' digestive glands, and octopine dehydrogenase was determined in mussels' posterior adductor muscle. Furthermore, the concentrations of aliphatic hydrocarbons, unresolved complex mixture and polycyclic aromatic hydrocarbons (PAHs) were quantified in mussels' tissue, and abiotic parameters were quantified in water samples collected at each site. Several biomarkers showed statistically significant differences among sampling sites. The redundancy analysis (RDA) used to perform the integrated analysis of the data showed a clear separation of the sampling sites in three different assemblages, which are in agreement with the PAHs levels found in mussels tissues. In addition, the RDA indicated that some of the selected biomarkers may be influenced by abiotic parameters (e.g. salinity, pH, nitrates and ammonia). The approach selected for this study seems to be suitable for monitoring petrochemical contamination.