Macroinvertebrate short-term responses to flow variation and oxygen depletion: A mesocosm approach

Ana R Calapez; Paulo Branco; José M Santos; Teresa Ferreira; Thomas Hein; António G Brito; Maria João Feio

doi:10.1016/j.scitotenv.2017.05.056

Macroinvertebrate short-term responses to flow variation and oxygen depletion: A mesocosm approach

Sci Total Environ. 2017 Dec 1:599-600:1202-1212. doi: 10.1016/j.scitotenv.2017.05.056. Epub 2017 May 13.

Authors

Ana R Calapez¹, Paulo Branco², José M Santos³, Teresa Ferreira³, Thomas Hein⁴, António G Brito⁵, Maria João Feio⁶

Affiliations

¹ LEAF - Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Lisbon, Portugal; MARE - Marine and Environmental Sciences Centre, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal; Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Vienna, Austria. Electronic address: anacalapez@isa.ulisboa.pt.
² CEF - Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, Portugal; CERIS - Civil Engineering for Research and Innovation for Sustainability, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal.
³ CEF - Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, Portugal.
⁴ WasserCluster Lunz - Inter-university Center for Aquatic Ecosystem Research, Lunz am See, Austria; Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Vienna, Austria.
⁵ LEAF - Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Lisbon, Portugal.
⁶ MARE - Marine and Environmental Sciences Centre, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal.

PMID: 28514838
DOI: 10.1016/j.scitotenv.2017.05.056

Abstract

In Mediterranean rivers, water scarcity is a key stressor with direct and indirect effects on other stressors, such as water quality decline and inherent oxygen depletion associated with pollutants inputs. Yet, predicting the responses of macroinvertebrates to these stressors combination is quite challenging due to the reduced available information, especially if biotic and abiotic seasonal variations are taken under consideration. This study focused on the response of macroinvertebrates by drift to single and combined effects of water scarcity and dissolved oxygen (DO) depletion over two seasons (winter and spring). A factorial design of two flow velocity levels - regular and low (vL) - with three levels of oxygen depletion - normoxia, medium depletion (dM) and higher depletion (dH) - was carried out in a 5-artificial channels system, in short-term experiments. Results showed that both stressors individually and together had a significant effect on macroinvertebrate drift ratio for both seasons. Single stressor effects showed that macroinvertebrate drift decreased with flow velocity reduction and increased with DO depletion, in both winter and spring experiments. Despite single stressors opposing effects in drift ratio, combined stressors interaction (vL×dM and vL×dH) induced a positive synergistic drift effect for both seasons, but only in winter the drift ratio was different between the levels of DO depletion. Stressors interaction in winter seemed to intensify drift response when reached lower oxygen saturation. Also, drift patterns were different between seasons for all treatments, which may depend on individual's life stage and seasonal behaviour. Water scarcity seems to exacerbate the oxygen depletion conditions resulting into a greater drifting of invertebrates. The potential effects of oxygen depletion should be evaluated when addressing the impacts of water scarcity on river ecosystems, since flow reductions will likely contribute to a higher oxygen deficit, particularly in Mediterranean rivers.

Keywords: Drift; Hypoxia; Mediterranean streams; Multiple-stressors; Synergistic effects; Water scarcity.