Environ Sci Pollut Res DOI 10.1007/s11356-015-5703-0
RESEARCH ARTICLE
Response of invertebrates from the hyporheic zone of chalk rivers to eutrophication and land use Octavian Pacioglu 1 & Oana Teodora Moldovan 2
Received: 24 April 2015 / Accepted: 26 October 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Whereas the response of lotic benthic macroinvertebrates to different environmental stressors is a widespread practice nowadays in assessing the water and habitat quality, the use of hyporheic zone invertebrates is still in its infancy. In this study, classification and regression trees analysis were employed in order to assess the ecological requirements and the potential as bioindicators for the hyporheic zone invertebrates inhabiting four lowland chalk rivers (south England) with contrasting eutrophication levels (based on surface nitrate concentrations) and magnitude of land use (based on percentage of fine sediments load and median interstitial space). Samples of fauna, water and sediment were sampled twice, during low (summer) and high (winter) groundwater level, at depths of 20 and 35 cm. Certain groups of invertebrates (Glossosomatidae and Psychomyiidae caddisflies, and riffle beetles) proved to be good indicators of rural catchments, moderately eutrophic and with high fine sediment load. A diverse community dominated by microcrustaceans (copepods and ostracods) were found as good indicators of highly eutrophic urban streams, with moderate-high fine sediment Responsible editor: Thomas Hein Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-5703-0) contains supplementary material, which is available to authorized users. * Octavian Pacioglu
[email protected] Oana Teodora Moldovan
[email protected] 1
River Communities Group, Freshwater Biological Association, River Laboratory, Queen Mary University of London, East Stoke, Wareham, Dorset BH 20 6BB, UK
2
BEmil Racovita^ Institute of Speleology, Clinicilor 5, 400006 Cluj-Napoca, Romania
load. However, the use of other taxonomic groups (e.g. chironomids, oligochaetes, nematodes, water mites and the amphipod Gammarus pulex), very widespread in the hyporheic zone of all sampled rivers, is of limited use because of their high tolerance to the analysed stressors. We recommend the use of certain taxonomic groups (comprising both meiofauna and macroinvertebrates) dwelling in the chalk hyporheic zone as indicators of eutrophication and colmation and, along with routine benthic sampling protocols, for a more comprehensive water and habitat quality assessment of chalk rivers. Keywords Hyporheos . Classification and regression trees . Chalk rivers . Hyporheic zone . UK
Introduction The hyporheic zone (HZ) is increasingly recognised as an important ecotone (Boulton et al. 2010) that is central to the functioning of the whole lotic ecosystem for its role in the biogeochemical cycling and turnover of chemicals between surface and groundwater (Williams et al. 2010). The HZ is an important habitat for both meiofauna and early instars of macroinvertebrates (hyporheos, sensu Boulton 2000), providing shelter during floods and important nesting sites for fish such as salmonids (Kemp et al. 2011). Although the existence of the hyporheos was recognised more than half a century ago (Orghidan 1955), there are still many aspects of its ecology that require further elucidation (Robertson and Wood 2010). Despite increasing acknowledgement of the HZ as a crucial habitat in the functionality of river ecology (Ward and Tockner 2001), the evaluation of habitat requirements of hyporheos is still in its infancy (Boulton et al. 2010; Griebler et al. 2010). Chalk rivers are considered iconic ecosystems in the southern UK (Berrie 1992) and one of the most productive riverine
Environ Sci Pollut Res
habitats (Bowes et al. 2005). They are groundwater-fed ecosystems, with low fluctuations in flow, temperature and suspended sediments (Sear et al. 1999). However, the very factors that make chalk streams unique also make them particularly susceptible to human impact (Bowes et al. 2005). Nutrient pollution and fine sediment deposition are widespread phenomena that are encountered in streams and rivers worldwide, including chalk streams (Howden and Burt 2009; Collins et al. 2013). Nitrate concentrations in groundwater and rivers in developed areas of the world have risen substantially as a result of the use of synthetic N fertilisers and cultivation of N-fixing crops (Turner and Rabalais 2003). Recent mathematical models suggest that nitrate concentrations will increase in rural chalk streams in the south-east of the UK by approximately 1 mg NO3/year (Howden and Burt 2009). Furthermore, urban chalk rivers (e.g. tributaries of the Thames flowing through London) are highly polluted with nitrates, nitrites, ammonia and phosphorus due to point source pollution from sewage treatment plants, septic tanks and household untreated water (Flynn et al. 2002; Snook and Whitehead 2004). Chalk rivers are also influenced by adjacent land use (Kemp et al. 2011). Soil erosion and river bank instability in rural areas (Collins et al. 2011) and high turbidity downstream sewage treatment plants in urban areas has resulted in a rising rate of accumulation of fine sediments (
