Ostracods as freshwater pollution indicators: a case study from the Ouseburn, a polluted urban catchment (Tyneside, NE England)

Ian Boomer,Frances Attwood

doi:10.1144/jm.26.2.117

Abstract

Abstract. The relationship between ostracod occurrence and water quality is investigated in the Ouseburn (Newcastle upon Tyne, NE England) in both a spatial and temporal context. For the first time, ostracod assemblages are used alongside traditional biological water quality indices. Physico-chemical parameters of the water are used in conjunction with standard macro-invertebrate-based biological indices (BMWP, ASPT) to assess general water quality. This is also the first detailed study of ostracod occurrence within a small urban catchment. Ostracod, macro-invertebrate and environmental samples were taken during the summer of 2001, with a small number of late autumn replicates taken to characterize the impact of known pollution events. The pollutants encountered in this study are primarily organic in nature and include sewage, agricultural sources (such as slurry) and de-icer runoff from the local airport. The head-water and tributaries are generally characterized by good water quality despite a number of pollution events recorded during the study. Ostracod diversity and abundance, although often low, support the evidence from the traditional methods of water quality assessment, both of which decrease downstream. An inverse relationship observed between ostracod abundance and macro-invertebrate indices suggests that relatively clean-water macro-invertebrate assemblages out-compete the ostracods or may be preying upon them.

Highlights

Biological indicators are useful measures of pollution loading in river systems because they respond to intermittent pollution events that might flush-through relatively quickly but may be missed by subsequent chemical sampling when the pollutant has passed through the system; they may respond to pollutants which are not picked up by routine chemical monitoring
This study investigates, albeit from a relatively small dataset, the relationship between ostracod abundance/diversity and water quality and the possible pollution tolerance of the most abundant species in the Ouseburn, northeast England
Traditional water quality assessment methods demonstrate a broad decrease in water quality downstream as the catchment becomes increasingly urbanized

Summary

Introduction

Biological indicators are useful measures of pollution loading in river systems because they respond to intermittent pollution events that might flush-through relatively quickly but may be missed by subsequent chemical sampling when the pollutant has passed through the system; they may respond to pollutants which are not picked up by routine chemical monitoring. Macro-invertebrates, generally >2 mm in length (e.g. gastropods, chironomids and the aquatic larval or adult stages of various insects), in particular are traditionally used as biological indicators to provide a qualitative and/or quantitative indication of water quality by their presence/absence and abundance (Mason, 1996). Microinvertebrates and their fossils are rarely employed as pollutant indicators in isolation but the widespread occurrence and often great numerical abundance of ostracods in freshwater suggests that such an application may have great potential. To derive the ASPT, the BMWP score is divided by the number of scoring taxa in that sample

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