This month, Journal of Applied Ecology turns its focus to the health of the worlds’ oceans, with a new Spotlight, Conservation in marine habitats. Ignasi Montero-Serra summarizes the importance of this collection of work that provides a variety of cutting-edge tools to quantify the impact of major stressors, and to guide management actions across marine habitats; from the intertidal to the deep sea.

Marine habitats are essential to the diversity, structure and function of life in the oceans. A large proportion of human population heavily depends on healthy marine ecosystems to ensure economic subsistence and development. Yet, these systems are exposed to several stressors acting at multiple scales.

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Photo by GEORGE DESIPRIS on Pexels.com

Marine conservation was born as a discipline to improve the sustainability of fisheries. During the past decades, there has been a growing awareness of the ecological and socio-economic benefits of conserving key ecosystem properties, and this led to the adoption of ecosystem-based fisheries management plans. However, not only fisheries threaten marine ecosystem. Nowadays, marine conservation has become a broad field that aims to design holistic management strategies that consider a wide range of impacts derived from human-related activities.

The latest issue of Journal of Applied Ecology addresses a great variety of such stressors, from local impacts of bottom trawling and direct invertebrate fisheries (e.g. the historically overfished Mediterranean red coral), to vessel traffic and collisions risk, acoustic disturbances by sonars, to more regional and diffuse impacts such as land-based pollution and climate change. Here, we feature seven study cases from different systems across the world that provide key insights to advance conservation science in marine ecosystems and its applications to current challenges.

Focusing locally but with wider implications, two novel studies provide tools to quantify and reduce the risk of impacts by vessels and sonar use to endangered marine mammals. Southall and colleagues quantified deep-sea foraging habitats for a beaked whale in areas where Navy sonar is often used. They found small-scale prey heterogeneity, where a high abundance of prey coincides with a commonly used area for beaked whales. These results can inform protection plans for endangered deep-diving marine mammals, with the implementation of sonar-free areas for important foraging habitats. On the other hand, Udell and colleagues present a novel framework based on encounter rate theory and decision analysis to quantify the effectiveness of speed zones as a management strategy to reduce collision risk for the Florida manatee (Trichechus manatus latirostris). Their decision analysis component helps to integrate ecological risks with socio-economic costs when evaluating different spatial configurations of management area designations.

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From a more regional perspective, Brown and colleagues reviewed modelling efforts for land-sea planning with a focus on water quality and fisheries and the linkages between terrestrial, freshwater and marine ecosystems. They provide an in-depth analysis of modelling tools and the need to consider the trade-off between model complexity and feasibility, with tools that can ensure representativity of key dynamic processes while maintaining their applicability under diverse contexts, which can include limited resources and data availability.

To address optimal monitoring of benthic communities under limited resources, Cooper and colleagues show how using biological-based indicators to classify habitats requires more fine-scale data but is much more cost-effective in the long-run, since the minimum sample size to detect meaningful changes can be reduced up to a 49%. Another important insight into management for sessile communities comes from the study published by Hiddink and colleagues, who linked longevity of benthic biota to their response to bottom-trawling, demonstrating that species and communities dominated by longer-lived species are much more vulnerable due to their lower intrinsic population growth rates. Focusing on a long-lived emblematic octocoral, the Mediterranean red coral, Montero-Serra and colleagues show that fishing impacts affect colony-size distributions and thus, marine protected areas (MPAs) are an effective tool to enhance the structural complexity this historically harvested species. However, protection of coral populations appears to provide little buffering to the detrimental impacts of recurrent heat waves in the Mediterranean Sea.

Climate change is among the most important stressors to marine ecosystems. Yet, restoration plans for marine habitats are only starting to consider this growing threat. In their Practitioner’s Perspective, Mitchell & Bilkovic discuss common approaches to the restoration of marshes and call for a reconsideration of current designs towards more dynamic solutions that can facilitate adaptation and resilience to climate change.

This new Spotlight on Conservation in marine habitats adds solid scientific evidence to marine conservation literature and should serve as a basis to advance towards dynamic and more complex modelling frameworks that can take advantage of new data while also guiding the acquisition of new data and management decisions under data-poor contexts. This collection presents a handful of cutting-edge modelling tools and novel frameworks and guidelines to monitor, assess and design sound conservation strategies that can be widely applied to quantify impacts and mitigate their effects on vulnerable marine species and communities.

Read all the papers in the Spotlight collection, Conservation in marine habitats in issue 56:5 of Journal of Applied Ecology.