CGL2013-47674-P - Parasitología ambiental y ecotoxicología

Pollution, biological invasions and climate change are three major threats to estuarine ecosystems. It is not possible to have a complete integrated understanding of the influence of these threats on aquatic ecosystems without taking into account parasites, which have a central role in foodwebs and in contaminant pathways. “Environmental Parasitology” is an interdisciplinary field addressing the interactions between parasites and pollution. This project will focus on brine shrimps Artemia and their abundant cestode parasites, building on three previous National I+D+i projects. The main study area is the Odiel salt pans which lie within the estuary of the Odiel and Tinto rivers, which is highly contaminated with heavy metals and Arsenic. Waterbirds feeding on native Artemia in these ponds accumulate contaminants in their bloodstream. The American brine shrimp Artemia franciscana is displacing native Artemia from across the Mediterranean region, and Odiel is one of few remaining sites with native Artemia. It has been suggested that local adaptation to the contaminated conditions by the native population prevents colonization by A. franciscana, and we will test this hypothesis and study the role of cestodes in the influence of metals on their intermediate hosts (brine shrimp) and final hosts (birds). The concentrations of heavy metals and Arsenic in Artemia, their cestodes, sediments, water and benthic chironomids will be assessed in ponds across the range of salinities at Odiel and at less contaminated salt pans in Doñana and Cadiz Bay (which holds A. franciscana). We will test whether the cestodes bioaccumulate contaminants and therefore detoxify the tissues of their host, as demonstrated for some other parasites. The toxicity of five metals will be compared for adults of the two Artemia species (with and without parasites) taken from the field from the three locations. Local adaptation against contaminants and the influence of increasing temperature and decreasing pH due to climate change will be tested on Artemia reared in the laboratory from eggs collected at each of the three field sites. The influence of an increase of 4oC and drop of 0.4 units in pH on the toxicity of Arsenic and a representative heavy metal, as measured by changes in mortality and in growth rate, will be determined for each population. The results from all these analyses and experiments will be incorporated in a model to calculate the ingestion rate of metals by waterbirds at Odiel under different scenarios (after an Artemia invasion, or after temperature increase). We will apply ecotoxicoproteomics and transcriptomics in experiments to identify the mechanisms underlying the complex interactions between contaminants, parasites and environmental conditions. These are powerful approaches that will identify the genes involved in conferring resistance to metals, as well as specific proteins acting as biomarkers of toxicity for native and alien Artemia. The results will be of help in the development of the Artemia-cestode system as a model to study the ecological effect of pollution, biological invasions and effects of climate change in estuarine systems around the world. They will also be of applied interest for aquaculture, e.g. as the identification of genes conferring resistance to metals may facilitate the rearing of Artemia and production of their cysts in contaminated areas.