Drivers of recruitment in sessile marine organisms are often poorly understood, due to the rapidly changing requirements experienced during early ontogeny. The complex suite of physical, biological, and ecological interactions beginning at larval settlement involves a series of trade‐offs that influence recruitment success. For example, while cryptic settlement within complex microhabitats is a commonly observed phenomenon in sessile marine organisms, it is unclear whether trade‐offs between competition in cryptic refuges and predation on exposed surfaces leads to higher recruitment.To explore the trade‐offs during the early ontogeny of scleractinian corals, we combined field observations with laboratory and field experiments to develop a mechanistic understanding of coral recruitment success. Multiple experiments conducted over 15 months in Palau (Micronesia) allowed a mechanistic approach to study the individual factors involved in recruitment: settlement behavior, growth, competition, and predation, as functions of microhabitat and ontogeny. We finally developed and tested a predictive recruitment model with the broader aim of testing whether our empirical insights explained patterns of coral recruitment and quantifying the relative importance of each trade‐off.Coral settlement was higher in crevices than exposed microhabitats, but post‐settlement bottlenecks differed markedly in the presence (uncaged) and absence (caged) of predators. Incidental predation by herbivores on exposed surfaces at early post‐settlement (<3 mm) stages and targeted predation by corallivores at late post‐settlement (3–10 mm) stages exceeded competition in crevices as major drivers of mortality. In contrast, when fish were excluded, competition with macroalgae and heterotrophic invertebrates intensified mortality, particularly in crevices. As a result, post‐settlement trade‐offs were reversed, and recruitment was more than twofold higher on exposed surfaces than crevices. Once post‐settlement bottlenecks were overcome, survival was higher on exposed surfaces regardless of fish exclusion. However, maximum recruitment occurred in crevices of uncaged treatments, being ninefold higher than caged treatments. Overall, we characterize recruitment success throughout the earliest life‐history stages of corals and uncover some intriguing trade‐offs between growth, competition and predation, highlighting how these change and even reverse during ontogeny and under alternate disturbance regimes.

The number of marine protected areas (MPAs) has grown exponentially worldwide over the past decade in order to meet international targets. Most of these protected areas allow extraction of resources and are therefore designated as “partially protected areas” (PPAs). However, the effectiveness of PPAs remains unclear due to the high variability of use types permitted. Here, we carried out what we believe to be the first global meta‐analysis of PPAs using a regulation‐based classification system for MPAs to assess their ecological effectiveness. This novel classification allows for unambiguous differentiation between areas according to allowed use, which is the key feature determining PPA performance. Highly and moderately regulated areas exhibited higher biomass and abundance of commercial fish species, whereas fish abundance and biomass in weakly regulated areas differed little from unprotected areas. Notably, the effectiveness of moderately regulated areas can be enhanced by the presence of an adjacent fully protected area. We concluded that limited and well‐regulated uses in PPAs and the presence of an adjacent fully protected area confer ecological benefits, from which socioeconomic advantages are derived.

Highlights d 6.01% of the Mediterranean is covered by protection d In 95% of this area, regulations are not stronger inside than outside MPAs d Only 0.23% of the Mediterranean is fully or highly protected d Protection is unevenly distributed across political boundaries and eco-regions

Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role.

While positive interactions have been observed to influence patterns of recruitment and succession in marine and terrestrial plant communities, the role of facilitation in macroalgal phase shifts is relatively unknown. In December 2012, typhoon Bopha caused catastrophic losses of corals on the eastern reefs of Palau. Within weeks of the typhoon, an ephemeral bloom of monospecific macroalgae (Liagora sp.) was observed, reaching a peak of 38.6% cover in February 2013. At this peak, we observed a proliferation of a second macroalgal species, Lobophora variegata. Lobophora was distributed non-randomly, with higher abundances occurring within the shelter of Liagora canopies than on exposed substrates. Bite rates of two common herbivorous fish (Chlorurus sordidus and Ctenochaetus striatus) were significantly higher outside canopies (2.5- and sixfold, respectively), and cage exclusion resulted in a significant increase in Lobophora cover. Experimental removal of Liagora canopies resulted in a 53.1% decline in the surface area of Lobophora after 12 days, compared to a 51.7% increase within canopies. Collectively, these results indicate that Liagora canopies act as ecological facilitators, providing a 'nursery' exclusion zone from the impact of herbivorous fish, allowing for the establishment of understory Lobophora. While the ephemeral Liagora bloom had disappeared entirely 9 months post-typhoon, the facilitated shift to Lobophora has persisted for over 18 months, dominating ~40% of the reef substrate. While acute disturbance events such as typhoons have been suggested as a mechanism to reverse algal phase shifts, our results suggest that typhoons may also trigger, rather than just reverse, phase shifts.

2Marine protected areas (MPAs) are key tools to mitigate human impacts in coastal environments, promoting sustainable activities to conserve biodiversity. The designation of MPAs alone may not result in the lessening of some human threats, which is highly dependent on management goals and the related specific regulations that are adopted. Here, we develop and operationalize a local threat assessment framework. We develop indices to quantify the effectiveness of MPAs (or individual zones within MPAs in the case of multipleuse MPAs) in reducing anthropogenic extractive and non-extractive threats operating at local scale, focusing specifically on threats that can be managed through MPAs. We apply this framework in 15 Mediterranean MPAs to assess their threat reduction capacity. We show that fully protected areas effectively eliminate extractive activities, whereas the intensity of artisanal and recreational fishing within partially protected areas, paradoxically, is higher than that found outside MPAs, questioning their ability at reaching conservation targets. In addition, both fully and partially protected areas attract non-extractive activities that are potential threats. Overall, only three of the 15 MPAs had lower intensities for the entire set of eight threats considered, in respect to adjacent control unprotected areas. Understanding the intensity and occurrence of human threats operating at the local scale inside and around MPAs is important for assessing MPAs effectiveness in achieving the goals they have been designed for, informing management strategies, and prioritizing specific actions.Keywords: fully protected area; partially protected area; management; extractive activities; non-extractive activities; marine use; Highlights• We present and operationalize a cost-effective framework to quantify local threats inside and outside MPAs.• We assess how good MPAs are at curbing extractive and non-extractive threats.• Fully protected areas effectively eliminate extractive threats.• Fully protected areas attract non-extractive threats, when allowed.• Small scale fishing intensity is larger in partially protected areas than outside.3

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The presence of biofouling communities in very large densities in offshore wind farms (OWFs) generates broad effects on the structure and functioning of the marine ecosystem, yet the mechanisms behind the temporal development of these communities remain poorly understood. Here, we use an 11-year series on biofouling fauna from OWFs installed in Belgian waters to determine succession patterns and to unravel the role of biological interactions in shaping community development. Our analysis shows that biological interactions, besides age and location, affect diversity patterns in OWFs. The abundance of foundation species, predators, and space occupiers was significantly related to richness and/or diversity. The trends in richness, diversity, and community composition suggest that no permanent stable climax is reached after 11 years, which can be linked to the dynamic and disturbance-prone environment of offshore fouling communities.