Comparing Chemical and Ecological Status in Catalan Rivers: Analysis of River Quality Status Following the Water Framework Directive

Abstract

In Europe, diverse biological indices and metrics have been developed for ecological status assessment in rivers using macroinvertebrate, diatoms, macrophytes, and fish communities according to the Water Framework Directive (2000/60/EC). Additionally, priority and hazardous substances (pesticides, PAHs, heavy metals, chlorinated and non-chlorinated solvents, endocrine disruptors, etc.) must be analyzed using their environmental quality standards (EQS) according to the 2008/105/EC Directive. Chemical and biological elements have to be properly combined to set the final water quality status. We compare ecological and chemical status outputs in a Mediterranean watershed (the Catalan river basins, NE Spain), in order to provide useful information about the strengths and weaknesses of quality status classification in rivers.A total of 367 sites with different sampling frequencies along the monitoring program period (for six following years) were used to determine the chemical and the ecological status in Catalan rivers. The results of the monitoring program carried out in Catalan rivers (2007–2009) show a higher percentage of nonfulfillment quality objectives due to ecological status rather than chemical status. A total of 144 river water bodies (39%) do not achieve the good biological quality according to the 2000/60/EC Directive, whereas 68 river water bodies (19%) do not achieve the EQS for priority and hazardous substances provided by the 105/2008/EC Directive (chemical status). Both chlorinated pesticides (mainly endosulfan, trifluralin, and hexachlorocyclohexanes) and endocrine disruptors (nonylphenols and octilfenols) are the main substances responsible for quality standard failures in Catalan rivers.Some chemical values must be carefully considered, since they are found near the EQS and their threshold detection values. EQS values for some priority substances (mainly heavy metals and organic compounds) are extremely low, up to threshold detection levels, which make chemical results uncertain. Additionally, bad chemical status does not necessarily imply biological community damages, at least in short time. A total of 21 river water bodies (6%) showed priority substance concentrations over the EQS thresholds, whereas biological elements showed good quality. Biological indices based on community structure and composition cannot detect specific chemical alterations at very low concentrations. Complementary analysis for risk assessment using biomarkers, species sensitivity distribution toxicity test, or other emerging tools can provide additional information of possible coming problems, which should be considered for investigative monitoring.