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Small island nations like the Maldives are highly dependent on healthy coral reefs and the ecosystem services they provide. Lately, Maldivian reefs have experienced considerable degradation as a result of severe mass bleaching events and accumulating threats posed by pollution, human development, coral diseases, and outbreaks of corallivores. Coral restoration can be a useful mitigation tool in assisting natural recovery, especially when economically important reef areas such as resort reefs are in poor health with slow natural recovery. This study assesses the performance efficiency of lagoon mid-water rope nurseries for coral gardening in two different atolls in the Maldives for the first time. Three different coral genera, namely Acropora, Pocillopora, and Porites, were assessed applying a common monitoring protocol. Fragment survival was generally very high, exceeding 90% survivorship for the genus Acropora and Pocillopora, while nursing success for Porites was significantly lower (66%). We further report benchmark growth rates for these genera in mid-water rope nurseries in the Maldives. The study also identifies potential threats to coral nursing success, namely disease occurrence and predation, as we report the corallivorous nudibranch Phestilla on in situ nursing stock for the first time. Overall, our results suggest that the use of mid-water rope nurseries in lagoons is an efficient and widely applicable technique for rearing corals in the Maldives. We aim to provide useful insight into best practices for applying this coral gardening technique on a wider scale in the archipelago and highlight future research requirements.

Corallivory causes considerable damage to coral reefs and can exacerbate other disturbances. Among coral predators, Drupella spp. are considered as delayer of coral recovery in the Republic of Maldives, although little information is available on their ecology. Thus, we aimed to assess their population structure, feeding behaviour and spatial distribution around 2 years after a coral bleaching event in 2016. Biological and environmental data were collected using belt and line intercept transects in six shallow reefs in Maldives. The snails occurred in aggregations with a maximum of 62 individuals and exhibited a preference for branching corals. Yet, the gastropods showed a high plasticity in adapting feeding preferences to prey availability. Drupella spp. were homogenously distributed in the study area with an average of 9.04 ± 19.72 ind/200 m2. However, their occurrence was significantly different at the reef scale with the highest densities found in locations with higher coral cover. The impact of Drupella spp. appeared to be minimal with the population suffering from the loss of coral cover. We suggest that monitoring programs collect temporal- and spatial-scale data on non-outbreaking populations or non-aggregating populations to understand the dynamics of predation related to the co-occurrence of anthropogenic and natural impacts.

The need for comprehensive and effective coral restoration projects, as part of a broader conservation management strategy, is accelerating in the face of coral reef ecosystem decline. This study aims to expand the currently limited knowledge base for restoration techniques in the Maldives by testing the performance of mid-water rope nurseries in a lagoon and a reef habitat. We examined whether different coral farming habitats impacted fragment survival, health and growth of two coral genera and how the occurrence of mutualistic fauna, predation and disease influenced coral rearing success. Two nurseries were stocked with a total of 448 Pocillopora verrucosa and 96 Acropora spp. fragments, divided into different groups (four Pocillopora groups: lagoon nursery at 5 m; reef nursery at 5, 10 and 15 m; two Acropora groups: lagoon nursery at 5 m and reef nursery at 5 m). Eight fragment replicates from the same donor colony (Pocillopora genets: N = 14, Acropora genets N = 6) were used in each group and monitored for one year. Our results show that fragment survival was high in both farming habitats (>90%), with P. verrucosa surviving significantly better in the lagoon and Acropora spp. surviving and growing significantly faster in the reef nursery. P. verrucosa growth rates were similar between reef and lagoon habitat. Different rearing depths in the reef nursery had no impact on the survival of P. verrucosa but coral growth decreased considerably with depth, reducing fragments’ ecological volume augmentation and growth rates by almost half from 5 to 15 m depth. Further, higher fish predation rates on fragments were recorded on the reef, which did not impact overall nursery performance. Mutualistic fauna, which correlated positively with fragment survival, was more frequently observed in the lagoon nursery. The occurrence of disease was noted in both habitats, even though implications for fragment health were more severe in the lagoon. Overall, our study demonstrates that lagoon and reef nurseries are suitable for rearing large numbers of coral fragments for transplantation. Nevertheless, we recommend considering the specific environmental conditions of the farming habitat, in particular water quality and year-round accessibility, in each case and to adjust the coral farming strategy accordingly. We hope that this novel research encourages the increased application of mid-water rope nurseries for ‘coral gardening’ to advance coral reef recovery and climate resilience in the Maldives.

Coral reefs are declining worldwide as a result of the effects of multiple natural and anthropogenic stressors, including regional-scale temperature-induced coral bleaching. Such events have caused significant coral mortality, leading to an evident structural collapse of reefs and shifts in associated benthic communities. In this scenario, reasonable mapping techniques and best practices are critical to improving data collection to describe spatial and temporal patterns of coral reefs after a significant bleaching impact. Our study employed the potential of a consumer-grade drone, coupled with structure from motion and object-based image analysis to investigate for the first time a tool to monitor changes in substrate composition and the associated deterioration in reef environments in a Maldivian shallow-water coral reef. Three key substrate types (hard coral, coral rubble and sand) were detected with high accuracy on high-resolution orthomosaics collected from four sub-areas. Multi-temporal acquisition of UAV data allowed us to compare the classified maps over time (February 2017, November 2018) and obtain evidence of the relevant deterioration in structural complexity of flat reef environments that occurred after the 2016 mass bleaching event. We believe that our proposed methodology offers a cost-effective procedure that is well suited to generate maps for the long-term monitoring of changes in substrate type and reef complexity in shallow water.

Green fluorescence is a common phenomenon in marine invertebrates and is caused by green fluorescent proteins. Many hydrozoan species display fluorescence in their polyps and/or medusa stages, and in a few cases patterns of green fluorescence have been demonstrated to differ between closely related species. Hydrozoans are often characterized by the presence of cryptic species, due to the paucity of available morphological diagnostic characters. Zanclea species are not an exception, showing high genetic divergence compared to a uniform morphology. In this work, the presence of green fluorescence and the morpho-molecular diversity of six coral- and bryozoan-associated Zanclea species from the Maldivian coral reefs were investigated. Specifically, the presence of green fluorescence in polyps and newly released medusae was explored, the general morphology, as well as the cnidome and the interaction with the hosts, were characterized, and the 16S rRNA region was sequenced and analyzed. Overall, Zanclea species showed a similar morphology, with little differences in the general morphological features and in the cnidome. Three of the analyzed species did not show any fluorescence in both life stages. Three other Zanclea species, including two coral-associated cryptic species, were distinguished by species-specific fluorescence patterns in the medusae. Altogether, the results confirmed the morphological similarity despite high genetic divergence in Zanclea species and indicated that fluorescence patterns may be a promising tool in further discriminating closely related and cryptic species. Therefore, the assessment of fluorescence at a large scale in the whole Zancleidae family may be useful to shed light on the diversity of this enigmatic taxon.

L’ecosistema delle scogliere coralline presenta una elevatissima diversità di specie, tuttavia è anche esposto a numerosi disturbi naturali ed antropici. Le minacce includono macro e micro-plastica, riscaldamento globale e predazione. La comprensione delle dinamiche ecologiche della scogliera corallina e le interazioni con attività umane è di primario interesse per evitare la perdita di biodiversità. Questa priorità è fondamentale per aree isolate e remote come la Repubblica delle Maldive, che risulta essere sensibile ai cambiamenti ambientali, anche se è un’area ancora poco investigata. Perciò, questo studio intende esplorare le maggiori minacce e interazioni che causano danni alla scogliera corallina maldiviana. In particolare la corallivoria, per cui, la struttura della popolazione, le preferenze alimentari e le variazioni di densità dei tre corallivori principali delle Maldive (Acanthaster planci, Culcita spp. and Drupella spp.) sono stati studiati. Questi corallivori hanno un ruolo nel deteriorare la copertura di corallo tramite predazione diretta e interazione con altri disturbi di origine antropica come l’aumento delle temperature delle acque. Ciò è specialmente valido per A. planci che ha sviluppato un’esplosione demografica nell’area di studio intensificando la pressione predatoria. Mentre Culcita spp. ha mostrato un ruolo potenzialmente specifico nel rallentare il recupero della scogliera corallina, poiché focalizza la predazione sulle reclute dei coralli. Al contratio, Drupella spp. ha mostrato un collasso della popolazione dopo un evento di mortalità dei coralli, riducendo la pressione predatoria senza apparentemente influenzare la fase di recupero. L’interazione tra corallivoria e minacce di origine antropica intensifica la mortalità dei coralli. Tuttavia non tutti i disturbi antropici sono conosciuti, spesso per mancanza di metodologie standard per quantificarli. Una minaccia aggiuntiva non ancora studiata in dettaglio è rappresentata dai detriti marini antropici (DMA). Perciò, un ulteriore obiettivo è stato quello di sviluppare un metodo efficace e rapido per monitorare e quantificare DMA sulle spiagge usando un drone e un sistema di intelligenza artificiale (IA) basato su un programma di apprendimento artificiale (PlasticFinder). L’alta risoluzione (0.5 cm/pix) dei dati ha permesso di rilevare più dell’ 87% degli oggetti presenti sulla spiaggia rappresentando uno strumento utile a monitorare rapidamente il tasso di accumulo di DMA anche in aree remote ed isolate o disabitate. Negl’ultimi decenni però le scogliere coralline hanno subito una elevata perdita di corallo vivo determinando lo sviluppo di tecniche per il restauro della scogliera corallina. Tuttavia, la valutazione dell’efficacia delle strategie di restauro sono limitate a pochi fattori, come sopravvivenza e crescita del corallo. Il coinvolgimento delle comunità di utenti delle scogliere coralline è stato dimostrato essere fondamentale. L’uso dell’analisi della soddisfazione degli utenti ha rivelato, in questo studio, il bisogno di intervenire con attività di restauro attivo invece che con l’uso di strutture artificiali. Inoltre, donne e locali si sono dimostrati i più interessati a dedicarsi a progetti di restauro, suggerendo che l’investimento nell’addestramento di queste categorie può risultare in una maggiore efficienza delle strategie di restauro. In conclusione, questo lavoro fornisce una visione dettagliata sull’impatto dei principali corallivori alle Maldive. Perciò può rappresentare un utile spunto per futuri studi sull’ecologia dei corallivori, e in più, per la comprensione di ulteriori impatti e strategie per salvaguardare la biodiversità delle scogliere coralline maldiviane. Coral reef is one of the most diverse ecosystem on Earth, yet one of the most exposed to natural and anthropogenic disturbances. Threats to coral reefs include macro and micro-plastic, global warming and natural coral predators. In this context, understanding the dynamics of coral reef and the interactions with anthropogenic activities is of primary interest to prevent the loss of the reef biodiversity. Such priority is fundamental for isolated and remote areas, such as the Republic of Maldives, which is highly sensitive to changes in environmental conditions, yet, barely investigated. Thus, this study is intended to explore natural and anthropogenic threats recently impacting the maldivian coral reef. Specifically, we investigated the population structure, feeding preferences, distribution and density variation of the three major corallivores occurring in the Maldives (Acanthaster planci, Culcita spp. and Drupella spp.). The results highlighted the role of corallivores in decreasing coral cover by direct predation and co-occurence with temperature-induced coral mortality. Especially for A. planci which showed a severe outbreak in the study area. While Culcita spp. showed a more specific possible role in delaying coral recovery, since resulted to focus predatory pressure on coral recruits. On the other hand, Drupella spp. showed a population collapse compared to previous studies in Maldives, reducing the predatory pressure during the recovery phase of the reef. Thus, the interaction between corallivores and anthropogenic disturbances intesify mortality of corals. Yet, not all disturbances are known, often for lacking of standard methodology for quantification. Among those, a further disturb not known in details is represented by marine anthropogenic debris (AMD). The purpose here was to develop an effective and time-saving method to monitoring and automatically quantifying AMD, using a commercial Unmanned Aerial Vehicle (UAV) and Artificial Intelligence (AI) with a deep-learning based software (PlasticFinder). The high resolution (0.5 cm/pix) of the data allowed to detect more than 87% of the object on the shores and the analysis from PlasticFinder reached a Positive Predictive Value of 94%, which overcame the limits highlighted in the previous AI algorithm used in the literature. The use of drone resulted in a time saving tool to survey AMD accumulation even in remote areas such as uninhabited islands. The degradation of the maldivian coral reef caused by anthropogenic and natural disturbances is a trigger for active strategies to enhance recovery through coral restoration. However, assessment tools of restoration effectiveness and development are still restricted to few ecological factors, such as coral survival and growth. Very few studies included other factors such as socio-economic assessment. The involvement of the community of users of the coral reefs are as important as factors related directly to corals, since users’ satisfaction may drive allocation of private funding useful to improve restoration success. Results presented here, revealed weak points and ways to improve coral restoration programs management in two resorts in the Maldives. The use of satisfaction analysis revealed the need for intervention dedicated to active restoration rather than using artificial reef. Further, women and Maldivians resulted to be the most willing to dedicate themselves to coral restoration project. Thus, suggesting that training session by the resort may be organized for such categories to build team of volunteers for improving local restoration programs. In conclusion, this work provide a detailed overview of the impacts of the main corallivores on the maldivian coral reef. Therefore, it may represent a baseline for future research on the ecology of coral predators and, additionally, for the understanding of further anthropogenic disturbances and for improving strategies to prevent the loss of maldivian coral reef biodiversity.

Although corallivory is recognized as a threat affecting the structure and integrity of coral reef habitats, ecological data on most species of coral consumers remain limited, slowing down the development of conservation and restoration strategies of the reef ecosystems. In this study, the population distribution and corallivorous behaviour of the cushion sea star Culcita sp. were investigated in the south region of Faafu Atoll, Maldives. Most sea stars were found on reef slopes within 0–10m depth and in areas characterized by low live coral cover. Several coral genera were preyed on by the sea star. Although most of the consumed corals belong to the genus Acropora, a feeding preference for the genera Pocillopora and Pavona and a consistent avoidance of the genus Porites were observed. Furthermore, the majority of the prey corals were small colonies (< 10cm diameter), even though Culcita sp. appeared to be capable of partially consuming larger colonies. Dietary preferences for specific coral colonies or genera have the potential to generate local shifts in coral community composition and structure and may affect reef recovery following natural and anthropogenic disturbance in an already impacted environment such as the Maldivian reefs.

Anthropogenic Marine Debris (AMD) is one of the major environmental issues of our planet to date, and plastic accounts for 80% of total AMD. Beaches represent one of the main marine compartment where AMD accumulates, but few and scattered regional assessments are available from literature reporting quantitative estimation of AMD distributed on the shorelines. However, accessing information on the AMD accumulation rate on beaches, and the associated spatiotemporal oscillations, would be crucial to refining global estimation on the dispersal mechanisms. In our work, we address this issue by proposing an ad-hoc methodology for monitoring and automatically quantifying AMD, based on the combined use of a commercial Unmanned Aerial Vehicle (UAV) (equipped with an RGB high-resolution camera) and a deep-learning based software (i.e.: PlasticFinder). Remote areas were monitored by UAV and were inspected by operators on the ground to check and to categorise all AMD dispersed on the beach. The high-resolution images obtained from UAV allowed to visually detect a percentage of the objects on the shores higher than 87.8%, thus providing suitable images to populate training and testing datasets, as well as gold standards to evaluate the software performance. PlasticFinder reached a Sensitivity of 67%, with a Positive Predictive Value of 94%, in the automatic detection of AMD, but a limitation was found, due to reduced sunlight conditions, thus restricting to the use of the software in its present version. We, therefore, confirmed the efficiency of commercial UAVs as tools for AMD monitoring and demonstrated - for the first time - the potential of deep learning for the automatic detection and quantification of AMD.

14 pages, 6 figures, 1 table, supporting information https://doi.org/10.1111/gcb.14670, Climate change and biological invasions are rapidly reshuffling species distribution, restructuring the biological communities of many ecosystems worldwide. Tracking these transformations in the marine environment is crucial, but our understanding of climate change effects and invasive species dynamics is often hampered by the practical challenge of surveying large geographical areas. Here, we focus on the Mediterranean Sea, a hot spot for climate change and biological invasions to investigate recent spatiotemporal changes in fish abundances and distribution. To this end, we accessed the local ecological knowledge (LEK) of small-scale and recreational fishers, reconstructing the dynamics of fish perceived as “new” or increasing in different fishing areas. Over 500 fishers across 95 locations and nine different countries were interviewed, and semiquantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, mostly warm-adapted species of both native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatial and temporal patterns, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of the shifting distribution of Mediterranean fishes and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macroregional coordination could pave the way for future large-scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level. This might help local communities to better understand, manage, and adapt to the ongoing biotic transformations driven by climate change and biological invaders, European Regional Development Fund, Grant/Award Number: MPA‐Adapt 1MED15_3.2_M2_337; Albert II of Monaco Foundation

The worldwide degradation of coral reefs due to local and global threats has, in the past decade, sparked the diffusion of active coral restoration programs which aim at supporting the natural process of recovery. Yet, most coral restoration projects limit monitoring to few ecological factors. The ability of measuring the effectiveness of these projects, including their socio-economic dimensions, could increase their credibility and determine their further expansion through ease access to financial resources. Here, we measured the satisfaction and the relative importance of key characteristics of the reef or “reef attributes” for clients and residents of resorts in the Maldives through Importance-Performance Analysis (IPA). Results of the fieldwork show that reef users in two resorts were not satisfied about the color, the quantity and the variety of the coral present in the locations. On the same items, importance ratings were very high thus indicating that a gap between satisfaction and importance and possibly highlighting a need for intervention. Some results were also gender-specific: women were much less satisfied than men but more willing to participate to a local coral restoration project. We recommend that evaluation of coral restoration programs include reef users’ satisfaction to provide a measure of effectiveness and potentially to ensure initial and longer-term support to the initiative.

Outbreaks of the corallivorous crown-of-thorns seastars have received increasing attention due to their negative impacts on coral reefs in the Indo-Pacific Ocean. However, outbreaks in remote and dislocated islands are still poorly understood. This study aims to begin filling informational gaps regarding outbreaks of Acanthaster planci in the remote islands of the central Ari Atoll, Republic of Maldives. The population of A. planci was monitored during three periods over 2 years (2015-2016) to evaluate variations in abundance and to characterise size structure and feeding behaviour. The outbreak appeared to be severe and active throughout the entire study period. The size structure analysis revealed a multimodal distribution dominated by individuals between 20 and 30 cm, suggesting that the outbreak may have resulted from a few nearby mass spawning events. Additionally, the most abundant live coral was Porites, which was also the most consumed genus; however, the electivity index showed a preference for corals of the genera Favites and Pavona. Finally, we also highlighted the need for more geographically extended surveys to better understand local patterns regarding outbreaks of A. planci in the Republic of Maldives.

The corallivorous crown-of-thorns starfish Acanthaster planci (COTS) is recognized as a major cause of coral reef degradation throughout much of the Indo-Pacific region (Fabricius 2013). In this study, we report a localised outbreak of COTS at Mama Ghiri, Ari Atoll, Republic of Maldives in June 2014 (3°44′40′′ N; 72°49′13′′ E) (Fig. 1a-c). Belt transects (approximately 9×100 m) were used to record COTS density in the shallows (0–5m depth). An average density of 120±51 COTS per transect (mean ± SD; n=6), with a maximum of 222, was recorded around Mama Ghiri. Moreover, coral mortality of approximately 70 % including complete or partial death of nearly 100 % of tabular Acropora (mainly belonging to the species A. cytherea, A. clathrata, and A. hyacinthus), was estimated (Fig. 1c). These data are comparable with those of COTS outbreaks recently reported in other Indo-Pacific regions (Baird et al. 2013). Although A. planci outbreaks were previously observed in the Maldives (Ciarapica and Passeri 1993), this event was more intense in terms of COTS density. As in many other parts of the world, Maldivian reefs are subjected to increasing pressure from natural and direct anthropogenic disturbances (Jaleel 2013). Considering that A. planci outbreaks may represent a significant threat to coral reef health and biodiversity, we stress the urgent need to explore other Maldivian reefs to document the extent of this phenomenon and its effect on corals and their associated fauna.