Algal symbiont diversity in Acropora muricata from the extreme reef of Bouraké associated with resistance to coral bleaching.

Widespread coral bleaching has generally been linked to high water temperatures at larger geographic scales. However, the bleaching response can be highly variable among individual of the same species, between different species, and across localities; what causes this variability remains unresolved. Here, we tracked bleached and non-bleached colonies of Acropora muricata to see if they recovered or died following a stress event inside the semi-enclosed lagoon of Bouraké (New Caledonia), where corals are long-term acclimatized to extreme conditions of temperature, pH and dissolved oxygen, and at a nearby control reef where conditions are more benign.

Corals adapted to extreme and fluctuating seawater pH increase calcification rates and have unique symbiont communities.

Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification rate. Identifying the resilience factors of corals to decreasing seawater pH is of paramount importance to predict the survivability of coral reefs in the future. This study compared corals adapted to variable pH (i.

Sponge organic matter recycling: Reduced detritus production under extreme environmental conditions.

Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions.

Phototrophic sponge productivity may not be enhanced in a high CO world.

Sponges are major components of benthic communities across the world and have been identified as potential "winners" on coral reefs in the face of global climate change as result of their tolerance to ocean warming and acidification (OA). Previous studies have also hypothesised that photosymbiont-containing sponges might have higher productivity under future OA conditions as a result of photosymbionts having increased access to CO and subsequently greater carbon production. Here we test this hypothesis for a widespread and abundant photosymbiont-containing sponge species Lamellodysidea herbacea at a CO seep in Papua New Guinea simulating OA conditions.

Ingestion of Diazotrophs Makes Corals More Resistant to Heat Stress.

Over the past decade, coral bleaching events have continued to recur and intensify. During bleaching, corals expel millions of their symbionts, depriving the host from its main food source. One mechanism used by corals to resist bleaching consists in exploiting food sources other than autotrophy.

pH variability at volcanic CO seeps regulates coral calcifying fluid chemistry.

Coral reefs are iconic ecosystems with immense ecological, economic and cultural value, but globally their carbonate-based skeletal construction is threatened by ocean acidification (OA). Identifying coral species that have specialised mechanisms to maintain high rates of calcification in the face of declining seawater pH is of paramount importance in predicting future species composition, and growth of coral reefs. Here, we studied multiple coral species from two distinct volcanic CO seeps in Papua New Guinea to assess their capacity to control their calcifying fluid (CF) chemistry.

Microbes support enhanced nitrogen requirements of coral holobionts in a high CO environment.

Ocean acidification is posing a threat to calcifying organisms due to the increased energy requirements of calcification under high CO conditions. The ability of scleractinian corals to cope with future ocean conditions will thus depend on their ability to fulfil their carbon requirement. However, the primary productivity of coral holobionts is limited by low nitrogen (N) availability in coral reef waters.

Near-future ocean warming and acidification alter foraging behaviour, locomotion, and metabolic rate in a keystone marine mollusc.

Environmentally-induced changes in fitness are mediated by direct effects on physiology and behaviour, which are tightly linked. We investigated how predicted ocean warming (OW) and acidification (OA) affect key ecological behaviours (locomotion speed and foraging success) and metabolic rate of a keystone marine mollusc, the sea hare Stylocheilus striatus, a specialist grazer of the toxic cyanobacterium Lyngbya majuscula. We acclimated sea hares to OW and/or OA across three developmental stages (metamorphic, juvenile, and adult) or as adults only, and compare these to sea hares maintained under current-day conditions.

High pCO promotes coral primary production.

While research on ocean acidification (OA) impacts on coral reefs has focused on calcification, relatively little is known about effects on coral photosynthesis and respiration, despite these being among the most plastic metabolic processes corals may use to acclimatize to adverse conditions. Here, we present data collected between 2016 and 2018 at three natural CO seeps in Papua New Guinea where we measured the metabolic flexibility (i.e.

Acclimatization of massive reef-building corals to consecutive heatwaves.

Reef-building corals typically live close to the upper limits of their thermal tolerance and even small increases in summer water temperatures can lead to bleaching and mortality. Projections of coral reef futures based on forecasts of ocean temperatures indicate that by the end of this century, corals will experience their current thermal thresholds annually, which would lead to the widespread devastation of coral reef ecosystems. Here, we use skeletal cores of long-lived Porites corals collected from 14 reefs across the northern Great Barrier Reef, the Coral Sea, and New Caledonia to evaluate changes in their sensitivity to heat stress since 1815.

Suitability of the shallow water hydrothermal system at Ambitle Island (Papua New Guinea) to study the effect of high pCO on coral reefs.

Volcanic CO seeps were successfully used to predict coral reef response to ocean acidification, although toxic elements, often characteristic of hydrothermal vents were rarely reported. We measured the physicochemical conditions, seawater carbonate chemistry and trace elements in Tutum Bay, Papua New Guinea. There, intense emission of hydrothermal fluids and CO expose the coral reef to a seawater pH between 7.

Effects of temperature and UVR on organic matter fluxes and the metabolic activity of .

Coral bleaching events are predicted to occur more frequently in the coming decades with global warming. The susceptibility of corals to bleaching during thermal stress episodes depends on many factors, including the magnitude of thermal stress and irradiance. The interactions among these two factors, and in particular with ultra-violet radiation (UVR), the most harmful component of light, are more complex than assumed, and are not yet well understood.

Reef-building corals thrive within hot-acidified and deoxygenated waters.

Coral reefs are deteriorating under climate change as oceans continue to warm and acidify and thermal anomalies grow in frequency and intensity. In vitro experiments are widely used to forecast reef-building coral health into the future, but often fail to account for the complex ecological and biogeochemical interactions that govern reefs. Consequently, observations from coral communities under naturally occurring extremes have become central for improved predictions of future reef form and function.

Nickel and ocean warming affect scleractinian coral growth.

The sensitivity of corals and their Symbiodinium to warming has been extensively documented; however very few studies considered that anthropogenic inputs such as metal pollution have already an impact on many fringing reefs. Thus, today, nickel releases are common in coastal ecosystems. In this study, two major reef-building species Acropora muricata and Pocillopora damicornis were exposed in situ to ambient and moderate nickel concentrations on a short-term period (1h) using benthic chamber experiments.

Ocean acidification affects fish spawning but not paternity at CO2 seeps.

Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification expected to occur owing to anthropogenic carbon dioxide emissions during this century. We provide the first evidence of the effects of ocean acidification on reproductive behaviour of fish in the wild. Satellite and sneaker male ocellated wrasse (Symphodus ocellatus) compete to fertilize eggs guarded by dominant nesting males.

Responses of two scleractinian corals to cobalt pollution and ocean acidification.

The effects of ocean acidification alone or in combination with warming on coral metabolism have been extensively investigated, whereas none of these studies consider that most coral reefs near shore are already impacted by other natural anthropogenic inputs such as metal pollution. It is likely that projected ocean acidification levels will aggravate coral reef health. We first investigated how ocean acidification interacts with one near shore locally abundant metal on the physiology of two major reef-building corals: Stylophora pistillata and Acropora muricata.

Metagenomics Reveals Planktonic Bacterial Community Shifts across a Natural CO2 Gradient in the Mediterranean Sea.

Bacterial communities at a CO2 vent (pH 6.7) were compared with those at control (pH 8.0) and transition sites (pH 7.

Calcification is not the Achilles' heel of cold-water corals in an acidifying ocean.

Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Ωara ) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2  1058 μatm, Ωara 1.

Thermally tolerant corals have limited capacity to acclimatize to future warming.

Thermal stress affects organism performance differently depending on the ambient temperature to which they are acclimatized, which varies along latitudinal gradients. This study investigated whether differences in physiological responses to temperature are consistent with regional differences in temperature regimes for the stony coral Oculina patagonica. To resolve this question, we experimentally assessed how colonies originating from four different locations characterized by >3 °C variation in mean maximum annual temperature responded to warming from 20 to 32 °C.

Ocean acidification impairs vermetid reef recruitment.

Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum.