Temperature patterns and mechanisms influencing coral bleaching during the 2016 El Niño

Under extreme heat stress, corals expel their symbiotic algae and colour (that is, ‘bleaching’), which often leads to widespread mortality. Predicting the large-scale environmental conditions that reinforce or mitigate coral bleaching remains unresolved and limits strategic conservation actions. Here we assessed coral bleaching at 226 sites and 26 environmental variables that represent different mechanisms of stress responses from East Africa to Fiji through a coordinated effort to evaluate the coral response to the 2014–2016 El Niño/Southern Oscillation thermal anomaly. We applied common time-series methods to study the temporal patterning of acute thermal stress and evaluated the effectiveness of conventional and new sea surface temperature metrics and mechanisms in predicting bleaching severity. The best models indicated the importance of peak hot temperatures, the duration of cool temperatures and temperature bimodality, which explained ~50% of the variance, compared to the common degree-heating week temperature index that explained only 9%. Our findings suggest that the threshold concept as a mechanism to explain bleaching alone was not as powerful as the multidimensional interactions of stresses, which include the duration and temporal patterning of hot and cold temperature extremes relative to average local conditions

Monitoramento em longo prazo da contenção vegetativa em talude rodoviário de saprolito de gnaisse em Minas Gerais

A sucessão de eventos após a revegetação de uma área, em geral, não é estudada. Com o passar do tempo, um consórcio vegetal que se apresentou favorável na fase inicial pode não ser adequado no futuro, deixando a área com o solo descoberto e suscetível à ação dos fatores intempéricos. O objetivo deste trabalho foi monitorar características associadas à contenção vegetativa e, em longo prazo, o surgimento de novas formas de cobertura ou exposição do solo em resposta à revegetação com gramíneas e leguminosas em talude rodoviário de declividade acentuada. Após quatro anos, foi observada, nas parcelas experimentais, a presença de novas formas de cobertura ou exposição do solo, denominadas tipologias, como: cobertura de braquiária, leguminosa, capim-gordura, espécies invasoras, biomanta, resíduos em decomposição, crostas microfíticas, crosta física, solo exposto, erosão e afloramento de rochas. Essas tipologias foram quantificadas em dois levantamentos: antes e após o período chuvoso. Foram confeccionados mapas de cobertura para cada parcela experimental e analisadas a dinâmica, distribuição espacial, frequência e competição entre as tipologias encontradas nos dois levantamentos. Das 11 tipologias encontradas, as espécies vegetais e as crostas microfíticas foram as mais importantes no estádio primário da sucessão ecológica, resultando em rápida estabilização e recuperação da superfície degradada e favorecendo o aparecimento de espécies invasoras. A variação sazonal entre os dois levantamentos levou à diminuição da erosão e ao solo exposto, pelo incremento da cobertura vegetal e das crostas microfíticas

Social–environmental drivers inform strategic management of coral reefs in the Anthropocene

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014–2017 global coral bleaching event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse

Recent advances in coastal ecology: studies from Kenya.

Evidence for the degradation of Kenyan coral reefs is abundant but the means to restore and manage them is less well understood. Degradation studies show that there are often two terminal states of coral reefs: one where the reef is dominated by large fleshy algae and the second by abundant sea urchins. Summaries of studies are presented where sea urchins and fleshy algae were reduced in order to determine the effect of algal and sea urchin dominance on coral reefs as well as the effect of elimination of fishing on one coral reef. Studies indicate that reducing coral reef plant and animal pests work best if done in areas where fishing is reduced. Reduction of fishing in one coral reef produced a number of predicted changes in the reefs, including increased fish and coral cover and reduced sea urchin and algal turf abundance. There are few options to restoring reefs that will not require reduced fishing effort. Many reefs presently have low coral cover due to the coral bleaching and mortality in March 1998, so there is a need to increase coral reef restoration activities.Publishe

Dynamics Of Drupella Cornuspopulations On Kenyan Coral Reefs

In the central Pacific and western Australia the coral-eating snail Drupella cornus has been reported to exhibit large population increases or 'outbreaks' (>10 snails/m2) that result in the loss or devastation of their coral prey. In Kenya, a large population increase of Drupella cornus was recorded from the early 1990's where D. cornus increased from a rare species in the mid 1980's to among the most common prosobranch snail by 1995 (~0.2 snails/m2). Population increases were most commonly observed in a section of reef that had experienced heavy fishing and loss of the durophagous predators such as triggerfish, but still maintained a high abundance of the branching coral Porites nigrescens. In unfished reefs, the population increases of D. cornus were less pronounced despite an abundance of their preferred coral prey - branching Acropora, Montipora, and Pocillopora. In one heavily fish reef, with a high abundance of another coral-eating snail, Coralliophila neritoidea, and low abundance of branching corals, few D. corn us were observed. Consequently, the success of D. corn us appears to be related to a complex interaction between appropriate environmental conditions for settlement success, the existence of branching corals, a low abundance of predators and the lack of other competitors such as C. neritoidea. An alternate hypothesis is that D. cornus settlement is patchy in space and time and the patterns observed in Kenya simply reflect this patchiness.Publishe