Meeting Abstract

77.1  Friday, Jan. 6  Decadal-scale changes of shallow subtidal benthos in an Irish marine reserve TROWBRIDGE, C.D.*; LITTLE, C.; PILLING, G.M.; STIRLING, P.; MILES, A.; Univ. of Oregon; Univ. of Bristol; Secretariat of the Pacific Community; Univ. of Bristol

Long-term annual monitoring of rocky intertidal and shallow subtidal shores of an Irish sea lough (1990-2011) documented major regime shifts in the last decade. Shortly after the population densities of the purple urchin Paracentrotus lividus plummeted in Lough Hyne Marine Reserve in SW Ireland, the warm-water fucalean alga Cystoseira foeniculacea and ephemeral algae proliferated. Release from herbivory and/or climate change may have facilitated this algal proliferation, which blanketed the benthos. Smothering of the benthos has led to shallow subtidal hypoxia. Furthermore, the invasive fucalean alga Sargassum muticum has made repeated incursions into the reserve. Although currently being reduced by persistent eradication efforts (2003-2011), Sargassum is spreading within the lough. Limited seawater flushing and propagule dispersal within the lough as well as eutrophication in coastal waters may have contributed to community-level changes. Whether the regime change is cyclical (contingent on re-establishment of urchins within the lough and continued eradication of S. muticum) or irreversible (due to critical transitions) currently remains unclear.