Chemical contamination in coastal areas alters shape, resistance and composition of carnivorous gastropod shells.

Morphological, structural and compositional alterations in shells of molluscs have been proposed as putative biomarkers of chemical contamination in coastal zones. Despite this, few studies were carried out using top predator gastropods which tend to be more susceptible to contamination exposure. Thus, the present study assessed disturbances on shells of Stramonita brasiliensis considering compression resistance and organic and mineralogical matrix composition, related to morphometric alterations. Results showed reductions in compression resistance and organic matrix content associated with higher contaminated sites. In addition, a predominance of calcite polymorphs was seen in shells obtained in polluted areas. Such outputs were consistent with local contamination levels which may have induced the observed alterations. Thus, changes in mollusc shells showed good performance as potential biomarkers of coastal contamination, being probably observed in other species of carnivorous gastropods around the world.

Mollusc shell shape as pollution biomarkers: Which is the best biological model?

Alterations in mollusc shells have been proposed contamination biomarkers. We used geometric morphometrics analyses associated with analytical determinations of contaminants to select suitable biological models among species widely distributed on coastal zones. The study was carried out using Lottia subrugosa (herbivore limpet), Crassostrea brasiliana (filter-feeder bivalve), and Stramonita brasiliensis (carnivore gastropod) obtained along a marked contamination gradient at Santos Estuarine System (Brazil). L. subrugosa and S. brasiliensis presented distinct shapes along the gradient, while no significant differences in shell form were seen for C. brasiliana. Indeed, limpets and snails presented morphometric parameters consistent with measured contamination levels hazardous substances. Based on cross-validation models, the reliability of morphometric responses was over 75% for the herbivore and carnivore species. In addition, for S. brasiliensis, a 95.2% confidence was detected in most contaminated sites. Therefore, shell alterations on carnivorous gastropods should be further investigated, seeking to be effectively employed as pollution biomarkers.

Contamination gradient affects differently carbonic anhydrase activity of mollusks depending on their feeding habits.

Aquatic organisms that inhabit coastal areas are often exposed to several contaminants. It is known that the bioaccumulation of contaminants can be amplified according to the species feeding habits and contaminant properties. As a consequence, species can experience different effects to contaminant exposure even if they inhabit the same area. The present study aimed to investigate the activities of carbonic anhydrase (CA), Ca2+-ATPase, and Mg2+-ATPase in different tissues (soft tissue, mantle, and gill) of three mollusk species (Lottia subrugosa, Stramonita brasiliensis, and Crassostrea brasiliana) with different feeding habits (herbivore, carnivore, and filter-feeder, respectively) which were sampled within a known contamination gradient at Santos Estuarine System (Southeastern Brazil). From the three enzymes tested, only CA was affected by the presence of contaminants within the contamination gradient evaluated. In general, the CA activity from the three species were lower in contaminated sites when compared to the reference site. The contrasting CA activity response observed in S. brasiliensis compared to L. subrugosa and C. brasiliana could be related to the tissue-specificity of this enzyme activity and species feeding habits (filter-feeders can accumulate more contaminants than herbivores and even carnivores). Results indicated that C. brasiliana mantle is the most suitable tissue for the use of CA analysis as a biomarker.

Shell form and enzymatic alterations in Lottia subrugosa (Gastropoda, Lotiidae) transplanted to a contaminated site.

Studies have shown that shell morphology and enzymatic activities in mollusks are affected by contaminants exposure. However, the correlation between enzymatic activities and the biomineralization process are not fully understood. The present study used a transplant bioassay and field sampling to evaluate shell measurements and the activities of carbonic anhydrase, Ca2+-ATPase, and Mg2+-ATPase in Lottia subrugosa sampled in Brazilian sites under different contamination levels. Results showed that, in general, shells from the reference site (Palmas) were more rounded than the ones from the contaminated site (Balsa). Effects in enzymatic activities in specimens from transplant bioassay were attributed to the known high contaminant levels present at Balsa. While the lack of enzymatic activity alterations during field sampling was attributed to physiological adaptation to contaminants exposure. Enzymatic activities were not correlated to shell biometric parameters in field sampling, indicating that these enzymes were not related to shell alterations detected in the present study.

Can shell alterations in limpets be used as alternative biomarkers of coastal contamination?

The present study evaluated the association among traditional biochemical biomarkers with biometric, morphometric, and elemental composition of Lottia subrugosa (patelliform gastropod) shells from three multi-impacted coastal areas in Brazil. The study was carried out in Todos os Santos Bay (TSB), Santos/São Vicente Estuarine System (SESS) and Paranaguá Estuarine Complex (CEP), using three sampling sites to seek contamination gradients in each area. Results showed that all biomarkers evaluated responded to environmental contamination, regardless the presence (SESS and CEP) or absence (TSB) of a gradient of contamination. The responses found using biometric and morphometric parameters were consistent with the traditional biomarkers of exposure and effects (lipid peroxidation and DNA damage). Indeed, changes in elemental composition of L. subrugosa shells suggest that exposure to contaminated environments is probably responsible for the alterations detected. Despite the simplicity and lower cost of biometric and morphometric analyzes, these parameters are influenced by natural environmental conditions from which biases may arise. Therefore, these tools should be evaluated through experimental studies before it can be used in future assessments. However, the findings from the present study were observed in three aquatic systems distributed over a wide range of latitudes, which indicates that gastropod shells reflect effects resulting from environmental contamination.