Benthic responses to organic enrichment and climatic events in the western North Sea

Abstract

Macrofaunal assemblages inhabiting stable offshore muddy sand substrata responded predictably to the effects of mild organic enrichment arising from sewage-sludge disposal off the north-east coast of England (western North Sea). At the disposal site, densities were elevated up to two-fold, but classical ‘indicator’ species were only marginally enhanced and there was no evidence of a significant waste-induced change in assemblage structure. The response following cessation of disposal was equally predictable, with a decline in densities to ‘reference’ levels some three years later. However, physical manifestations of disposal, including tomato pips and non-biodegradable artefacts, were still evident after this time.Changes in diversity at selected monitoring stations tended to track each other over time and the employment of treatment/reference ratios and limit values for acceptable change provided a useful model for the simplified expression of trends. Predictions concerning the limited scale and intensity of the effects of sewage-sludge disposal appear to have been met, indicating that the management option of sea disposal was, at the time, an environmentally acceptable one.Temporal trends in the benthic fauna were also correlated with winter values of the North Atlantic Oscillation Index for the preceding year. The densities and variety of species tended to be lower in response to warmer winters characterized by westerly airflows which were commonly encountered in the 1990s. Finally, the increasing importance of extended time-series data for the investigation of man-made impacts on the marine environment is highlighted, along with the accompanying requirement for continuity and quality assurance of sampling programmes.

Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea

“…Overall, they suggested these changes can be linked to the variability of North Sea hydro-climate influenced by the North Atlantic Oscillation. However, as observed in previous studies, the role of NAO on diversity remains imprecise with positive or negative responses being observed (Dippner et al, 2003;Beuchel et al, 2006;Rees et al, 2006;Kröncke et al, 2011;Birchenough et al, 2015).…”

“…They suggested that the intermediary between NAO and benthic macrofauna was sea surface temperature in late winter and early spring. This hypothesis was supported by subsequent studies (Tunberg and Nelson, 1998;Kröncke et al, 2001;Hagberg and Tunberg, 2000;Rees et al, 2006). As highlighted by Birchenough (2015), climatic changes have high influence on sea-water temperature, hydrodynamic patterns, ocean acidification and sea-level rise-coastal squeeze.…”

Response of intertidal macrofauna to multiple disturbance types and intensities – An experimental approach

“…Increased total biomass Eleftheriou et al (1982), Rowlatt et al (1991), Rees et al (1992b), Rees and Rowlatt (1995), Moore (2003), Kress et al (2004), Elias et al (2005), Rees et al (2006), and Whomersley et al (2007) Fishing Changes in sedimentology and roughness, frequency of sediment plumes, changes in trophic structure, increased scavengers (Asterias rubens), removal of target species, death/ injury of large long lived benthic species (Glycymerus glycymerus) and bioturbating species (Echinocardium cordatum) reduction in biomass, abundance, species number and diversity Hall (1994), Dayton et al (1995), Macdonald et al (1996), Kaiser and Spencer (1996), Brown and Wilson (1997), Jennings and Kaiser (1998), Hansson et al (2000), Lindegarth et al (2000), Jennings et al (2001), Kaiser et al (2001), andDe Biasi (2004) transportation and freshwater and organic inputs (Elliot et al, 1998, Zajac, 2004Fujii, 2007). Common species found inhabiting intertidal mud flats are generally regarded as opportunistic and display more-or-less continual reproductive activity and recruitment through the year (Bagheri and Mclusky, 1982;Lillebo et al, 1999;Rossi, 2003;Bolam, 2004) as opposed to a more episodic, distinctly seasonal pattern.…”

Changes in North Sea macrofauna communities and species distribution between 1986 and 2000

“…Changes in sublittoral North Sea benthic communities in the last decades have been found in different areas (Ibanez and Dauvin, 1988;Rachor, 1990;Frid et al, 1996;Kröncke et al, 1998;2001;Wieking and Kröncke, 2001;Dippner and Kröncke, 2003;Franke and Gutow, 2004;Schröder, 2005;van Hoey et al, 2005;Rees et al, 2006;Reiss et al, 2006;van Hoey et al, 2007;Neumann et al, 2008;2009a, b;Schückel et al, 2010;Lindley et al, 2010). Most shifts in the community structure were directly or indirectly correlated to the variability of the North Atlantic Oscillation Index (NAOI) in winter, especially to the increase in NAOI since the late 1980, and resulted in the increase in warm-temperate species, a decrease in cold-temperate species or the invasion of non-native species.…”