1,721,152 research outputs found
Long-term change in bioconstruction potential of Maldivian coral reefs following extreme climate anomalies
No full textGlobal climate change has increased the frequency and intensity of extreme heat anomalies and consequent mass coral bleaching events. Long-term dynamics of hard coral cover, bioconstruction potential, carbonate deposition, and reef accretion was monitored over a 20-year period on Maldivian coral reefs in order to investigate the effects of high-temperature anomalies on coral reef accretion and their recovery potential. Changes experienced by shallow reefs between 1997 and 2017 were evaluated by considering five different bioconstructional guilds and the BioConstruction Potential index (BCP), a proxy for the constructional capacity of reefs. Abnormally high temperatures in 1998 and 2016 led to severe coral bleaching and consequent mortality, especially of the primary builders. Renewed carbonate deposition was not documented until 2–3 years after the bleaching, and 6–9 years passed until constratal (i.e., low relief) growth was achieved. Finally, 14–16 years were required to reach accretion rates high enough to ensure superstratal (i.e., high relief) growth. Coral mortality in the Maldives during the 2016 bleaching event was lower than in 1998, and the initial recovery was faster and occurred via a different trajectory than in 1998. Rising levels of anthropogenic carbon emissions are predicted to accelerate sea level rise and trigger severe coral bleaching events at least twice per decade, a frequency that will (a) prevent coral recovery, (b) nullify reef accretion, and consequently, (c) result in the drowning of Maldivian reefs under the worst climate projections
The new face of the northernmost coral reefs of the Maldives revisited after 13 years
No full textCoral reef ecosystems in Ihavandhippolhu Atoll, the northernmost atoll of the Maldives, have undergone significant changes following the 1998, 2010, and 2016 bleaching events. This study evaluates the recovery after 13 years following repeated bleaching events and the shift in coral reef composition in this remote and scantly explored region of the Indian Ocean. Data collected in January 2024 from ten strategic sites within the atoll reveal substantial shifts in benthic composition compared to earlier surveys from 2011. We observed a significant increase in overall hard coral cover, with resilient taxa—such as massive and encrusting corals—becoming dominant after bleaching events. In contrast, more sensitive genera like branching and tabular Acropora have declined sharply, indicating a shift in the benthic community composition toward more resistant coral taxa. The substantial recovery of hard coral cover over time suggests the resilience of the coral ecosystem in this remote atoll, although the recovery process is still ongoing, as shown by the incomplete restoration of original diversity and colony growth forms. A standardized and periodic monitoring plan in Ihavandhippolhu Atoll will be needed to track the ongoing changes in reef community composition under conditions of minimal human influence
Early warning response of Posidonia oceanica epiphyte community to environmental alterations (Ligurian Sea, NW Mediterranean).
No full textThe epiphyte community structure of the Posidonia oceanica leaves in three impacted meadows occurring in urbanised coastal areas was contrasted with that observed in three meadows located within Marine Protected Areas in the Ligurian Sea. Samplings were carried out in two distinct periods, at the beginning and at the end of the summer season, in order to individuate early changes in the epiphyte community structure. Differently from the descriptors commonly adopted for evaluating the health status of P. oceanica ecosystem, the epiphyte community structure was able to detect alterations in the water quality already after 4 months. The impacted meadows showed an immature epiphyte community characterised by large development of brown algae. Leaf P. oceanica epiphytes are, thus, proposed as appropriate biological quality elements (BQEs) able to show early responses to environmental alterations and they should be included in the monitoring programs for the conservation and the management of coastal area
Geological control of Posidonia oceanica meadow distribution: the case of Capo Mortola (Liguria, NW Mediterranean)
No full textStructural variability of the epiphytic community in a Posidonia oceanica meadow (Ligurian Sea, NW Mediterranean).
No full textPattern and intensity of human impact on coral reefs depend on depth along the reef profile and on the descriptor adopted
No full textCoral reefs are threatened by multiple global and local disturbances. The Maldives, already heavily hit by the 1998 mass bleaching event, are currently affected also by growing tourism and coastal development that may add to global impacts. Most of the studies investigating effects of local disturbances on coral reefs assessed the response of communities along a horizontal distance from the impact source. This study investigated the status of a Maldivian coral reef around an island where an international touristic airport has been recently (2009-2011) built, at different depths along the reef profile (5-20 m depth) and considering the change in the percentage of cover of five different non-taxonomic descriptors assessed through underwater visual surveys: hard corals, soft corals, other invertebrates, macroalgae and abiotic attributes. Eight reefs in areas not affected by any coastal development were used as controls and showed a reduction of hard coral cover and an increase of abiotic attributes (i.e. sand, rock, coral rubble) at the impacted reef. However, hard coral cover, the most widely used descriptor of coral reef health, was not sufficient on its own to detect subtle indirect effects that occurred down the reef profile. Selecting an array of descriptors and considering different depths, where corals may find a refuge from climate impacts, could guide the efforts of minimising local human pressures on coral reef
The challenge of managing marine biodiversity: a practical toolkit for a cartographic, territorial approach
No full textPattern of wide-scale substitution within Posidonia oceanica meadows of NW Mediterranean Sea: invaders are stronger than natives
No full text- …
