The effects of chemical pollution on the bioturbation potential of estuarine intertidal mudflats

Abstract

Bioturbation by benthic infauna has important implications for the fate of contaminants as well as for changes to the sediment structure, chemistry and transport characteristics. There is an extensive literature dealing with the influence of sedimentary variables on the structure and function of infaunal marine and estuarine organisms but less is known of the converse, the influence of biota on sedimentary structure. Although some work has been carried out regarding spatial and temporal patterns of bioturbation, little attention has been given to the effects of pollution. The paper gives a framework of animal sediment relationships in an intertidal environment and discusses the general role of macrofauna in structuring and modifying sedimentary features. A brief outline of the various techniques used for quantifying the degree of bioturbation is given and some of these techniques have then been used to demonstrate the effect of a petrochemical discharge on the bioturbation potential of intertidal communities in the Humber estuary, eastern England. These studies indicate an increase in bioturbation with increasing distance from the source of pollution, not only because of differences in abundance, animal size and depth of activity but also because of the difference in species composition between the communities. As a means of interpreting the responses, the species present have been broadly classified in terms of their feeding strategy and sediment modification potential. The paper concludes by discussing the potential impact, in terms of effect on sediment transport, of selectively removing the different guilds (by pollution).

Can functional groups be used to indicate estuarine ecological status?

“…We assess how changing the way in which the biota are classified alters the match of biological and abiotic data, and the implication this has for our understanding of ecosystem health. Muzik & Elliott (2000) demonstrated that the bioturbation potential scores of Swift (1993) and trophic groups both altered with increasing pollution levels. We extend their work by examining how well each category differentiates sites along natural environmental gradients and how easily the results can be interpreted.…”

“…To differentiate between coastal sites according their bioturbation ''potential'', Swift (1993) proposed a system of scoring species. Muzik & Elliott (2000) combined both of these approaches with work by Gerino et al (1993), Wheatcroft et al (1994) and Dauwe et al (1998), to examine relationships between functional groups and sediment dynamics, along a pollution gradient. They successfully demonstrated changes in function with distance from a pollution source.…”

“…However, the system assumes that any two species with the same potential score are active at the same scale and level of intensity, i.e., they have equal potential to cause displacement of sediment particles, but no consideration is taken of how far those particles might be moved or how often. Muzik & Elliott (2000) point out that bioturbation scores could have greater ecological significance if biomass, abundance and body size were also considered.…”

Rapid Assessment of Intertidal Wetland Sediments

“…Fluctuations in temperature, salinity, dissolved oxygen, and water content are more extreme in the intertidal region than in the sublittoral zone (Hayward, 1994). Furthermore, the environmental variables in intertidal wetlands are greatly affected by pollution and sudden changes to the environment (Mazik and Elliott, 2000;de la Huz et al, 2005;van der Wal et al, 2008b). Field monitoring is simply too expensive in practice for the dynamically changing conditions of intertidal wetlands.…”

Ecological restoration of tidal estuaries in North Western Europe: an adaptive strategy to multi-scale changes

“…Pollution and eutrophication needed to be tackled (Mazik & Elliott 2000, Mazik 2004) while setting back the shore line was required in response to sea level rise. A large scale experimental site was chosen in the 1990s for depolderisation and habitat (re)creation.…”