Empirical Models of Transitions between Coral Reef States: Effects of Region, Protection, and Environmental Change

There has been substantial recent change in coral reef communities. To date, most analyses have focussed on static patterns or changes in single variables such as coral cover. However, little is known about how community-level changes occur at large spatial scales. Here, we develop Markov models of annual changes in coral and macroalgal cover in the Caribbean and Great Barrier Reef (GBR) regions

Global gradients of coral exposure to environmental stresses and implications for local management

Background: The decline of coral reefs globally underscores the need for a spatial assessment of their exposure to multiple environmental stressors to estimate vulnerability and evaluate potential counter-measures. Methodology/Principal Findings: This study combined global spatial gradients of coral exposure to radiation stress factors (temperature, UV light and doldrums), stress-reinforcing factors (sedimentation and eutrophication), and stress-reducing factors (temperature variability and tidal amplitude) to produce a global map of coral exposure and identify areas where exposure depends on factors that can be locally managed. A systems analytical approach was used to define interactions between radiation stress variables, stress reinforcing variables and stress reducing variables. Fuzzy logic and spatial ordinations were employed to quantify coral exposure to these stressors. Globally, corals are exposed to radiation and reinforcing stress, albeit with high spatial variability within regions. Based on ordination of exposure grades, regions group into two clusters. The first cluster was composed of severely exposed regions with high radiation and low reducing stress scores (South East Asia, Micronesia, Eastern Pacific and the central Indian Ocean) or alternatively high reinforcing stress scores (the Middle East and the Western Australia). The second cluster was composed of moderately to highly exposed regions with moderate to high scores in both radiation and reducing factors (Caribbean, Great Barrier Reef (GBR), Central Pacific, Polynesia and the western Indian Ocean) where the GBR was strongly associated with reinforcing stress. Conclusions/Significance: Despite radiation stress being the most dominant stressor, the exposure of coral reefs could be reduced by locally managing chronic human impacts that act to reinforce radiation stress. Future research and management efforts should focus on incorporating the factors that mitigate the effect of coral stressors until long-term carbon reductions are achieved through global negotiations

Coral reef degradation is not correlated with local human population density

The global decline of reef-building corals is understood to be due to a combination of local and global stressors. However, many reef scientists assume that local factors predominate and that isolated reefs, far from human activities, are generally healthier and more resilient. Here we show that coral reef degradation is not correlated with human population density. This suggests that local factors such as fishing and pollution are having minimal effects or that their impacts are masked by global drivers such as ocean warming. Our results also suggest that the effects of local and global stressors are antagonistic, rather than synergistic as widely assumed. These findings indicate that local management alone cannot restore coral populations or increase the resilience of reefs to large-scale impacts. They also highlight the truly global reach of anthropogenic warming and the immediate need for drastic and sustained cuts in carbon emissions

The Builders of the Oceans – Part I: Coral Architecture from the Tropics to the Poles, from the Shallow to the Deep

At any scale, corals are live buildings. Their carbonate skeletons constitute three-dimensional frameworks allowing the delicate coral polyp to emerge from the sea bottom and populate vast areas of the ocean. These constructions, reminders of the structural complexity found in the forest, are found everywhere in the Earth’s oceans, from the polar regions to the tropics and from the tidal pools to the dark abyssal plains. They can be found as solitary or in modest aggregations of a few centimeters in size or gargantuan colonies of mythological proportions; when many, they can create the largest nonhuman structures built by organisms. Life and death of the coral “trees” are influenced by the mineral architecture and the presence of bioeroders. Shape and size facilitate or restrict their access to food and light and influence structural strength tested by currents and swells. The role that corals play in the oceans defies any attempt at simplification since it transcends the life span of the small polyp, geological time, and ecological space. Long after the polyps are gone, coral skeletons continue to harbor numerous organisms of disparate nature by overgrowing, drilling, and dissolving the carbonates. These chapters are a personal journey into the coral forest of the world’s oceans, with stations along singular aspects of their present and past. Our point of departure is the ecosystem engineering of the coral polyp through the construction of its skeleton, followed by selected examples of human interactions with the “stone from the sea” ( see Chapter “The Builders of the Oceans – Part II: Corals from the Past to the Present (The Stone from the Sea)

Do No-Take Reserves Benefit Florida\u27s Corals? 14 Years of Change and Stasis in the Florida Keys National Marine Sanctuary

With coral populations in decline globally, it is critical that we tease apart the relative impacts of ecological and physical perturbations on reef ecosystems to determine the most appropriate management actions. This study compared the trajectories of benthic assemblages from 1998 to 2011 in three no-take reserves and three sites open to fishing, at 7-9 and 15-18 m depth in the Florida Keys. We evaluated temporal changes in the benthic assemblage to infer whether fisheries bans in no-take reserves could have cascading effects on the benthos in this region. Coral cover declined significantly over time at our sites and that trend was driven almost exclusively by decline of the Orbicella (formerly Montastraea) annularis species complex. Other coral taxa showed remarkable stasis and resistance to a variety of environmental perturbations. Protection status did not influence coral or macroalgal cover. The dynamics of corals and macroalgae in the 15 years since the reserves were established in 1997 suggest that although the reserves protected fish, they were of no perceptible benefit to Florida\u27s corals