Monitoring the resilience of a no-take marine reserve to a range extending species using benthic imagery

Fostering marine resilience through the reduction of anthropogenic pressures in temperate rocky reefs

Resilience is vital for maintaining the health of temperate coastal systems, especially in the Anthropocene era, where anthropogenic pressures such as pollution, physical impacts, and overfishing pose significant threats. However, the scarcity of studies addressing marine resilience hampers its effective management. To address this issue, we evaluated the resilience of 300 temperate rocky reefs situated in Southern Europe, considering biological, environmental, and anthropogenic factors. We identified 43 top resilient areas recommended for conservation and 39 bottom resilient areas that could benefit from reducing anthropogenic pressures. Given that our findings suggest that anthropogenic pressures unequally influence the resilience of bottom resilient areas, we followed their decreasing order of influence to simulate five management scenarios based on the cumulative reduction of these pressures. While different percentages of reduction in anthropogenic pressures were necessary to significantly enhance resilience in each scenario, we found that, regardless of the approach taken, a comparable percentage of bottom resilient areas-ranging from 17 % to 23 %-could be reclassified as moderate resilient areas. By advancing resilience knowledge in temperate rocky reefs, this research underscores the important role that reducing anthropogenic pressures plays in enhancing resilience but also provides valuable insights for their strategic management.

Vulnerability of Temperate Mesophotic Ecosystems (TMEs) to environmental impacts: Rapid ecosystem changes at Lough Hyne Marine Nature Reserve, Ireland

Temperate Mesophotic Ecosystems (TMEs) are stable habitats, usually dominated by slow-growing, long-lived sessile invertebrates and sciaphilous algae. Organisms inhabiting TMEs can form complex three-dimensional structures and support many commercially important species. However, TMEs have been poorly studied, with little known about their vulnerability to environmental impacts. Lough Hyne Marine Nature Reserve (Ireland) supports TMEs in shallower waters (12-40 m) compared with other locations (30-150+ m) as a result of the unusual hydrodynamic conditions. Here, we report changes that have occurred on the sponge-dominated cliffs at Lough Hyne between 1990 and 2019, providing insights into TME long-term stability and vulnerability to environmental impacts. Our main finding was a marked decline in most three-dimensional sponges at the internal sites of the lough. This was likely the result of one or more mass mortality events that occurred between 2010 and 2015. We also found an increase in ascidians, which might have been more tolerant and benefited from the space freed by the sponge mortality. Finally, in the most recent surveys, we found a high abundance of sponge recruits, indicating that a natural recovery may be underway. The possible factors involved in these community changes include eutrophication, increased temperature, and a toxic event due to an anomaly in the oxycline breakdown. However, the absence of comprehensive monitoring of biotic and abiotic variables makes it impossible to identify the cause with certainty. Our Lough Hyne example shows the potential vulnerability of TMEs to short-term disturbance events, highlighting the importance of monitoring these habitats globally to ensure they are appropriately conserved.