CHANGING THE PARADIGM OF THE ECOTOXICITY ASSAYS APPLIED IN ENVIRONMENTAL RISK ASSESSMENT: FROM TOXICITY TO HABITAT SELECTION

N THE ENVIRONMENTAL RISK ASSESSMENT SCHEMES, ECOTOXICOLOGICAL ASSAYS HAVE BEEN CONSIDERED AN INDISPENSABLE TOOL TO ASSESS THE TOXICITY CAUSED BY THE CONTAMINANTS ON ORGANISMS. ALTHOUGH BIOASSAYS TRY TO SIMULATE THE ENVIRONMENTAL CONDITIONS AT WHICH ORGANISMS ARE REALLY EXPOSED, THE EXPERIMENTAL ENVIRONMENT SIMULATED IN THE BIOASSAYS IS VERY REDUCTIONIST IF COMPARED TO A REAL SYSTEM: FOR INSTANCE, THE FORCED EXPOSURE USED TO ASSESS THE TOXICITY OF THE CHEMICAL COMPOUNDS. TRADITIONALLY, BIOASSAYS ARE PERFORMED IN A CONFINED ENVIRONMENT, WHERE ORGANISMS ARE FORCEDLY EXPOSED TO THE CONTAMINANTS AND THE EFFECTS ARE MEASURED AFTER AN EXPOSURE PERIOD. THIS FORCED EXPOSURE COULD, BE CONSIDERED ENVIRONMENTALLY UNREALISTIC AS IT: (I) ASSUMES THAT ORGANISMS ARE PASSIVE AGENTS ACCEPTING THE CONTINUOUS EXPOSURE TO CONTAMINANTS, (II) IGNORES THAT ORGANISMS CAN DETECT AND AVOID CONTAMINATION BY ESCAPING TOWARDS LESS CONTAMINATED AREAS AND (III) DOES NOT TAKE INTO ACCOUNT IF AND HOW CONTAMINANTS DETERMINE THE DISPLACEMENT OF ORGANISMS AND THEIR HABITAT SELECTION PROCESSES. THE PRESENT PROJECT WILL PROVIDE A NOVEL APPROACH TO BIOASSAYS, BY USING A NON-FORCED EXPOSURE SYSTEM, TO SIMULATE THE DISPERSION PATTERN OF CONTAMINANTS, THROUGH WHICH ORGANISMS CAN FREELY MOVE AND SELECT AREAS WITH DIFFERENT CONTAMINATION LEVELS. THIS AVOIDANCE RESPONSE PREVENTS ORGANISMS OF SUFFERING TOXIC EFFECTS CAUSED BY THE CONTINUOUS EXPOSURE AND IT FOCUSES ON THE EFFECTS RELATED TO THEIR SPATIAL DISTRIBUTION. THE NON-FORCED APPROACH ALLOWS FOR REDUCING THE LIMITATIONS OF THE FORCED EXPOSURE USED IN THE TRADITIONAL BIOASSAYS AND IT BREAKS THE WIDELY ACCEPTED PARADIGM THAT THE RISK OF A CHEMICAL COMPOUND IS CONDITIONED TO THE TOXICITY CAUSED AT THE INDIVIDUAL LEVEL. THE GOAL OF THE PRESENT PROJECT IS TO DEVELOP AND IMPLEMENT A NON-FORCED EXPOSURE SYSTEM TO BE USED IN ENVIRONMENTAL RISK STUDIES AND, MOREOVER, TO ASSESS HOW THIS APPROACH CAN HELP PREDICTING THE ROLE OF CONTAMINANTS IN HABITAT SELECTION.