Modelling the response of floodplain aquatic assemblages across the lateral hydrological connectivity gradient
B. Gallardo A C , S. Gascón B , M. González-Sanchís A , A. Cabezas A and F. A. Comín AA Pyrenean Institute of Ecology – Spanish Council of Science, Avda. Montañana 1005, 50192 Zaragoza, Spain.
B Institute of Aquatic Ecology – Faculty of Sciences, University of Girona 17071, Girona, Spain.
C Corresponding author. Email: belinda@ipe.csic.es or galla82@hotmail.com
Marine and Freshwater Research 60(9) 924-935 https://doi.org/10.1071/MF08277
Submitted: 2 October 2008 Accepted: 24 February 2009 Published: 22 September 2009
Abstract
Hydrological connectivity is one of the main controlling factors of habitats and aquatic assemblages on river floodplains. Nevertheless, the lack of universal measures of river–floodplain connectivity (i.e. the lateral hydrological connectivity, LHC) limits the comparison of the response of aquatic assemblages to hydrological connectivity and impedes the understanding of floodplain functioning across different systems. To address these needs, we tested the ability of six different LHC surrogates to model changes in richness, abundance and composition of aquatic assemblages across a Mediterranean floodplain (Ebro River, NE Spain). As shown by generalised additive models, LHC surrogates explained 15% to 65% of the richness and abundance of aquatic assemblages. Zooplankton, macroinvertebrates and phytoplankton showed overlapping peaks of richness at flood duration rates of 5, 15 and 30 days year–1 respectively. Redundancy analyses showed that LHC surrogates explained 17% to 37% of aquatic assemblage composition. Distance to the river and flood duration were the most important determinants of macroinvertebrate composition, whereas flood magnitude and water-level variability best accounted for the variance in zooplankton and phytoplankton compositions. Models based on LHC surrogates such as those presented here can help in predicting the consequences of restoration measures and may be useful in setting restoration goals for aquatic assemblages.
Additional keywords: flood duration, generalised additive model, macroinvertebrates, phytoplankton, rarefied richness, redundancy analysis, zooplankton.
Acknowledgements
This study was supported by the Spanish Ministry of Education (MEC CGL2005-07059-C02-01) and Department of Environment–Aragon Government, with additional support for B.G. from the Aragon Government (B061 2005 pre-doctoral grant), to A.C. from the Spanish Scientific Council (I3P pre-doctoral grant) and to M.G.-S. from the Spanish Ministry of Education (FPI pre-doctoral grant). Xavier Quintana, Jordi Sala, Dani Boix and Stéphanie Gascóon helped with organism identification and the author is specially grateful to them for their contribution. Thanks are extended to Andrew Boulton and two anonymous referees for their helpful suggestions that have increased the quality of this paper.
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