“Think I’ll go eat worms?”: does nutrient pollution transform upper trophic levels of estuarine food webs?
Start date: 30 August 2015
Eutrophication of estuarine environments is a global conservation concern. As a consequence of excess nutrients extensive intertidal macro-algal mats can develop. These can cause anoxic conditions within the sediment and potentially transform the composition and diversity of benthic invertebrate communities. This could have implications for higher tropic levels and the functioning of the estuarine food web. In Poole Harbour (UK) mats of green algae now develop from spring and persist into the autumn months, thereby coinciding with the arrival of nationally and internationally important populations of migratory coastal birds (Charadrii). To determine the impact of algal mat development in the harbour on bird feeding behaviour the abundance and biomass of benthic invertebrate prey was measured over two winters at three locations that were colonised by algal mats. This was combined with monthly bird counts and video of bird behaviour to determine the species functional response. Invertebrate abundance and biomass was highly variable yet showed that abundances and biomass of important bird prey species declined with increasing mat coverage and biomass. Field observations and video analysis revealed that some coastal bird species are adapting their feeding behaviour to cope with substantial algal mat coverage.