Lough Hyne: Europe’s First Statutory Marine Reserve—A Biodiversity Hotspot

Lough Hyne Marine Reserve was designated Europe’s first statutory marine reserve in June 1981 due to its range of habitats and the associated rich biodiversity. Located in south-west Ireland, it has become one of the most studied marine sites in the world, with over 500 publications derived from studies from the late 19th century onwards. More than 1850 marine species have been recorded from its waters. The Lough has asymmetric tides due to a delay caused by the presence of a restrictive sill at the Rapids, a narrow and shallow constriction through which all tidal exchange with the outside ocean occurs. The tidal inflow takes 4h, the ebb is 8.5h. In the Rapids, current speeds can exceed 3ms−1, but drop close to zero in the north-east corner of the inner Lough. This highly variable current regime contributes significantly to the differences seen in habitats as well as associated fauna and flora, both intertidally and subtidally. Significant changes, including biodiversity loss, have been recorded in the Lough flora and fauna over the last 20years. A number of potential drivers of change have been identified. These include: eutrophication from anthropogenic nutrient runoff along the entire Irish south-west coast; oxygen depletion stemming from natural thermocline formation, plus decomposition of increased densities of ephemeral algal mats (themselves potentiated by eutrophication); the arrival of invasive species. Increased tourism and climate change may also have played their part. It is evident that active restoration of sites may be required, together with enhanced management of the marine reserve to slow the biodiversity loss.