Sea-level rise, expected environmental changes, and responses of intertidal benthic macrofauna in the Humber estuary, UK

Abstract

In many European estuaries, extensive intertidal habitats could vanish in the future due to rising sea levels that squeeze tidal flats against established sea defences. The remaining intertidal area is likely to become steeper with coarser sediment, and saline water may intrude upstream due to increased water depth and enhanced wave energy. This paper investigates the impacts of sea-level rise on benthic macrofauna in an intertidal habitat in the Humber estuary, UK. Field surveys were conducted between 2003 and 2004 to examine spatial patterns of benthic macrofaunal biomass along the estuarine longitudinal gradient and the local beach width gradient. Multiple regression analysis revealed that >80% of the observed variation in biomass of the 2 dominant bivalve species Macoma balthica and Cerastoderma edule, and the total biomass of other macrobenthic species, could be explained by key environmental variables such as salinity, sediment characteristics and morphological factors. Physical data for the Humber estuary were assessed to predict the likely course of changes in these key environmental variables in response to sea-level rise. Model simulations showed that a sea-level rise of 0.3 m would result in a 6.7% loss of intertidal area and 6.9% loss of total macrobenthic biomass, and that saline intrusion could partly compensate for such loss of macrobenthic biomass. However, associated environmental changes, such as beach slope steepening and sedimentary shifts, could have overriding negative impacts with potential loss of macrobenthic biomass of up to 22.8%, depending on the extent of environmental changes.