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.
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.
New insights into coral reef threats and restoration perception: a case study in the Republic of Maldives
SAPONARI, LUCA
2020
Abstract
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.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/72688
URN:NBN:IT:UNIMIB-72688