Environmental pollution and natural populations: a biomarkers case study from the Iberian Atlantic coast

The degradation of estuaries is a result of human activities which overloads the environment with substances of both industrial and/or natural origins. Bioindicators have been consistently used to interpret effects of contaminants in the environment. In this study, the use of biomarkers (particular measurable characteristics of a bioindicator organism) was used to evaluate the contamination by xenobiotics of Crangon crangon natural populations. The central aim was to evaluate the capability of a battery of biomarkers to discriminate sites with different types of contamination. The activity of the enzymes cholinesterases (ChE), lactate dehydrogenase (LDH) and glutathione S-transferases (GST) were used as biomarkers. In addition, the ChE form(s) present in the cephalotorax of C. crangon were characterised. Organisms were seasonally sampled from winter 2001/2002 to autumn of 2002, at "reference" sites and at sites that receive agricultural, industrial and/or urban effluents. Results obtained in the characterisation of ChE with different substrates and selective inhibitors demonstrate that the form of ChE present in the cephalotorax of C. crangon shows proprieties of vertebrates' AChE and therefore it may be classified as true AChE-like ChE. The battery of biomarkers exhibited seasonal and local variations, apparently related to agricultural, industrial or urban effluent contamination. The tested biomarkers proved to be able to discriminate sources of environmental contamination, and confirms C. crangon as a sensitive species suitable to be used as a bioindicator.     

Bioaccumulation of heavy metals and radionuclides from seawater by encased embryos of the spotted dogfish Scyliorhinus canicula

Encased embryos of spotted dogfish Scyliorhinus canicula absorbed six radio-isotopes (241Am, 109Cd, 57Co, 134Cs, 54Mn and 65Zn) directly from seawater during short-term experimental exposure, demonstrating the permeability of the egg-case to these contaminants. Embryo to water concentration factors (CFs) ranged from 0.14 for 134Cs to 7.4 for 65Zn. The 65Zn and 57Co CFs increased exponentially with embryo length, whereas the CF for 109Cd declined with length. Among different components of the encased embryo the egg case was the major repository (69-99%) of all six radio-isotopes that were distributed throughout its wall. Egg-case CFs were as high as 10(3) for 57Co and 65Zn, making it the major source of gamma radiation exposure to the embryo and potentially of radio-isotopes for continued absorption by the embryo, following the uptake phase of the experiment. The patterns of uptake by the egg-case approximated linearity for most isotopes and loss rates were isotope-specific; egg-case biokinetics were not greatly affected by the viability of the contained embryo. Within the embryo initial data on radio isotopic distribution show that the skin is their major site of uptake, as previously demonstrated for juveniles.     

Exposure of inner-shelf reefs to nutrient enriched runoff entering the Great Barrier Reef Lagoon: post-European changes and the design of water quality targets

We used historical flood plume extent data (modelled) to quantify the typical spatial extent of the summer runoff-seawater mixing zone of the Great Barrier Reef (GBR) lagoon. Spatially explicit analysis of the variability of in situ chlorophyll a concentrations (observed) across the runoff-seawater mixing zone, then allowed us to explore regional differences in the nutrient enrichment impact of runoff events from the various river systems that drain the GBR catchment. We demonstrate the existence of a discernable north-south gradient along the length of the GBR, such that for equivalent runoff:seawater dilutions ratios, lower levels of nutrient enrichment (as indicated by chlorophyll alpha observations) result from the river systems that drain the relatively undisturbed northern areas of the GBR catchment, compared to more human-impacted central and south areas. We identify a strong correlation between this north-south enrichment gradient and the flood concentration of dissolved inorganic nitrogen (DIN) entrained by the various river systems. By substituting the nutrient enrichment characteristics of the human-impacted river discharges with those of the undisturbed northern rivers, we provide a means to compare the short-term enriching 'footprint' for existing runoff intrusions with those that are likely to have occurred under pre-European catchment conditions. We demonstrate that under pre-European conditions, the nutrient enriching impact from river runoff was likely to have been largely constrained within 1-2 km of the coast, whereas existing conditions support the impact of reefs some 20-30 km off the coast. By using the developed spatial relations, we show that for the heavily human-impacted river systems, reductions in the end-of-river concentrations of DIN in the order 50-80% are needed in order to restore parity with pre-European conditions. We discuss these results in regard to developing end-of-catchment water quality targets for the region.     

Pure-phase transport and dissolution of TCE in sedimentary rock saprolite

The objective of this study was to experimentally determine the influence of pore structure on the transport and dissolution of trichloroethylene (TCE) in clay-rich saprolite. In order to simulate a "spill," pure-phase TCE containing a water-insoluble fluorescent dye was injected into two heterogeneous 24-cm-diameter by 37-cm-long undisturbed columns of water-saturated saprolite. TCE entry occurred at capillary pressures of 2.7 and 4.0 kPa. Ten or 28 d after injection, the column was sliced horizontally into three sections and visually examined. The distribution of fluorescent dye indicated that pure-phase TCE migrated mainly through fractures in the shale saprolite and through fine root holes or other macropores in the limestone saprolite residuum. Analysis of saprolite subsamples indicated that TCE was present throughout much of the saprolite column but usually at concentrations less than the solubility of TCE. This spreading was caused by diffusion, which also contributed to the rapid dissolution of TCE in the fractures and macropores. Modeling was carried out using previously published dissolution and diffusion equations. The calculations confirm that rapid disappearance of immiscible TCE can occur in this type of material because of the small size of fracture or macropore openings and the high porosity of the fine-grained material. This study indicates that industrial solvents can readily enter fractures and macropores in otherwise very fine-grained subsoils and then rapidly dissolve and diffuse into the fine-pore structure, from which they may be very difficult to remove.     

Resolution of MRS applied to the characterization of hard-rock aquifers

The performance of the Magnetic Resonance Sounding (MRS) method applied to the investigation of heterogeneous hard-rock aquifers was studied. It was shown using both numerical modeling and field measurements that MRS could be applied to the investigation of the weathered part of hard-rock aquifers when the product of the free water content multiplied by the thickness of the aquifer is >0.2 (for example, 10-m-thick layer with a 2% water content). Using a currently available one-dimensional MRS system, the method allows the characterization of two-dimensional subsurface structures with acceptable accuracy when the size of the subsurface anomaly is equal to or greater than the MRS loop. However, the fractured part of hard-rock aquifers characterized by low effective porosity (<0.5%) cannot be resolved using currently available MRS equipment. It was found that shallow water in the weathered part of the aquifer may screen MRS signals from deeper water-saturated layers, thus further reducing the possibility of investigating deeper fractured aquifers. A field study using the NUMIS(plus) MRS system developed by IRIS Instruments was carried out on an experimental watershed in southern India. A heterogeneous unconfined aquifer in a gneissic formation was successfully localized, and MRS results were confirmed by drilling shortly after the geophysical study. The top of the aquifer revealed by MRS was found to be in a good agreement with observed static water level measurements in boreholes.     

Esterase activities and lipid peroxidation levels in offshore commercial species of the NW Mediterranean Sea

There is a lack of information on monitoring neurotoxicity in offshore commercial species. To help fill this gap, we sampled hake (Merluccius merluccius) and Norway lobster (Nephrops norvegicus) in fishing grounds off the coast of l’Ametlla de Mar (NW Mediterranean) in June 2005 at a depth of 100 m and 400 m. Additionally, at 400 m depth, two other fish species, Micromesistius poutassou and Phycis blennoides were included. Neurotoxicity markers such as Colinesterases (ChEs), namely acethyl- (AChE), butyryl- (BChE), propionyl- (PrChE) and carboxilesterase (CbE) were measured in muscle. Lipid peroxidation (LP), a marker of oxidative damage, was also included. The results are discussed in relation to the animal’s sex, size and fishing depth. A comparison of esterases and LP levels between muscle and liver of hake and between muscle and hepatopancreas of Norway Lobster was made.

AChE was dominant in muscle and CbE in hepatopancreas. No differences between fish species were seen for AChE. However, N. norvegicus, presented lower levels of ChEs and LP. A size-dependence in ChEs was seen for M. merluccius, with larger animals showing significantly lower activities (p < 0.05). Sex-dependence was seen in N. norvegicus for most esterases, except AChE, with males displaying higher activities (p < 0.05). A sampling-depth effect was also seen in the crustacea, with animals from 100 m generally presenting lower esterase activities and higher LP levels.     

The AEM and regional carbonate aquifer modeling

The analytic element method (AEM) has been applied to a 15,000-km2 area of the Paleozoic carbonate rock terrain of Nevada. The focus is the Muddy River springs area, which receives 1.44 m3/s (51 ft3/s) of regionally derived ground water, and forms the Muddy River. The study was undertaken early in 2000 to support the development of a cooling water supply for a gas-fired generation facility 20 km south of the Muddy River springs. The primary objectives of the AEM modeling were to establish a better understanding of regional fluxes and boundary conditions and to provide a framework for examination of more local transient effects using MODFLOW. Geochemical evidence available in 2000 suggested two separate flow fields, one in the north discharging at the springs, and a southern area of small hydraulic gradients. To be conservative, however, hydraulic continuity between the two areas was maintained in the 2000 AEM model. Using new monitoring well data collected in the south, and analyses confirming that seasonal pumping effects in the north are not propagated to the south, a later AEM model that included a barrier calibrated with relative ease. The analytic element model was well suited for simulating an area larger than the immediate area of interest, was easy to modify as more information became available, and facilitated the stepwise development of multiple conceptual models of the site.     

The impact of a macroalgal mat on benthic biodiversity in Poole Harbour

Blooms of macroalgal matting are increasingly common within temperate zones and are often comprised of opportunistic species such as Ulva lactuca. Where this algae forms a dense mat, a stressful environment is created in the sediment below, influencing the invertebrate infaunal assemblage. This study was conducted over a six month period during which a dense mat of U. lactuca developed and subsequently dispersed. The algal mat was found to have a significant negative impact on species richness, abundance and biomass of the macroinfauna. However, a faunal community developed within the algal mat which contained several species not previously observed. This community increased the abundance and diversity of the overall invertebrate assemblage. The results are discussed in relation to impacts on the ecosystem as a whole.