Macroalgal mats in a eutrophic estuarine marine protected area: implications for benthic invertebrates and wading birds

Authors: Thornton, A., Herbert, R.J.H., Stillman, R. and Franklin, D.

Pages: 703-727

Publisher: Elsevier

Green macroalgal mats are a consequence of increased nutrient input into estuarine ecosystems and can cover extensive areas of intertidal habitats. The extent and biomass of mats is a key metric for estuarine ecological condition assessment. We measured macroalgal mats in Poole Harbour Marine Protected Area (MPA) from 2013 to 2015. Peak biomass reached >2 kg m 2 and persisted at >1 kg m 2 with >50% coverage throughout both seasons.

Intertidal mudflats in Poole Harbour MPA contain an abundance and diversity of benthic macrofauna providing a vital prey resource for 20,000 overwintering wading birds. Overall invertebrate abundance declined when macroalgal mat biomass >800 g m 2.

Dense macroalgal mats persisted into autumn thereby coinciding with the arrival of the overwintering wading birds. This level of coverage, combined with reduced prey energy, could lead to a decline in the designated feature with implications for the UK’s binding agreements, and lead to sanctions under current legislation.

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