Ecological and ecotoxicological responses in the assessment of the ecological status of freshwater systems: A case-study of the temporary stream Brejo of Cagarrão (South of Portugal)

Abstract

The objective of the study was to assess the integrated use of macroinvertebrate indexes and ecotoxicological parameters in the evaluation of the ecological status of a temporary stream with a strong agricultural influence. Water quality was analysed at two sampling sites along the stream, considering: chemical supporting parameters; hazardous substances (pesticides); benthic macroinvertebrate communities, through quality (Iberian Biological Monitoring Working Party and Iberian Average Score Per Taxon) and multi-metric indices (Southern Portuguese Index of Invertebrates and Ecological Quality Ratio); and ecotoxicological responses using lethal and sub-lethal bioassays. The water chemical characterization showed high levels of organic matter and nutrients, mainly in the dry period ((biochemical oxygen demand (BOD): 18.5-25.5mgL, chemical oxygen demand (COD): 60.8-193.7mgL; total phosphorus (TP): 0.17-0.33mgL)), which may compromise the support of biological life. In accordance with the physicochemical results, the stream had an ecological status less than good. Of the 25 pesticides analysed, only five, namely terbuthylazine, 2-methyl-chlorophenoxyacetic acid, bentazone, mecoprop and metolachlor were quantified. In general, the concentrations of pesticides detected were low, except at the source of the stream in January 2012 (sum of pesticides 2.29μgL), mainly due to the concentration of bentazone (1.77μgL), both values surpassing the European Commission threshold values. The analysis of benthic macroinvertebrates showed low levels of abundance and family diversity, with communities dominated by resistant groups to organic pollution and pesticides, such as the Chironomidae family. In general, the reproduction ecotoxicological results showed a very marked decrease in the number of juveniles per female. The Spearman correlation identified pesticides, namely MCPA (R=-0.89; p<0.05), as the main responsible for the observed effect. The results showed the linearity and complementarity of the two groups of biological responses, allowing to cover the interactions between the ecosystem's species and the different types of pollutants.

Assessment of the Benthic Macroinvertebrate Communities in the Evaluation of the Water Quality of Portuguese Reservoirs: An Experimental Approach

“…However, other studies have observed low diversity and abundance of macroinvertebrate communities in reservoirs when compared to natural lakes (e.g., [26]). Furthermore, these communities tend to be dominated by groups resistant to organic pollution and pesticides, such as CHI, as mentioned in Palma [4] and Trottier [21].…”

“…Over the past few years, a growing concern with the decrease of freshwater quality worldwide has been acknowledged [1][2][3]. Indeed, ensuring the waterbody quality is essential to preserve the ecosystem and conserve the natural structure, function, and dynamics [4] to guarantee the maintenance of the ecological balance [5]. The construction of dams in lotic ecosystems promotes the creation of lentic water bodies upstream (identified as heavily modified and artificial water bodies, such as reservoirs).…”

Land-Cover Patterns and Hydrogeomorphology of Tributaries: Are These Important Stressors for the Water Quality of Reservoirs in the Mediterranean Region?

“…The dissolved oxygen (DO), also showed a great temporal variability, with saturation percentages exceeding the limits for the good ecological status (60-120%; [47]) at Amieira, in January and July 2017 (DO = 181%), at Álamos in January 2017 (DO = 125%), and at Zebro in July 2017 (DO = 171%). In general, the DO variations are related with seasonal changes and rainfall patterns, being the higher values observed during the wet season [7,8,48], which may explain the high levels detected in January, characterized by low water temperature. The electric conductivity (EC) was the parameter that presented the major variability among streams, with the highest values (>1000 μS cm −1 ) detected at Zebro and Álamos.…”

How water quality standards for pesticides affect the classification of the chemical status of rivers

“…For example, the chemical status of the Boiron River was mainly defined as good at S2 and S3 when using the revised WQC whereas it was characterized as poor to very poor when using the historical standard. In addition, aquatic species have been shown to be sensitive to the concentration of pollution (see e.g., Ccanccapa, Masiá, Navarro-Ortega, Picó, & Barceló, 2016;Milano et al, 2018;Palma et al, 2018). The quality of the river in terms of nutrient and pesticide concentration is an important stress factor for aquatic organisms, whose sensitivity to pollution often follows a log-normal distribution (Nagai, 2016).…”