The ecological effects of ocean acidification (OA) from rising atmospheric carbon dioxide (CO2) on benthic marine communities are largely unknown. We investigated in situ the consequences of long-term exposure to high CO2 on coral-reef-associated macroinvertebrate communities around three shallow volcanic CO2 seeps in Papua New Guinea. The densities of many groups and the number of taxa (classes and phyla) of macroinvertebrates were significantly reduced at elevated CO2 (425–1100 µatm) compared with control sites.
Anthropogenic nutrient inputs enhance microbial respiration within many coastal ecosystems, driving concurrent hypoxia and acidification. During photosynthesis, Symbiodinium spp., the microalgal endosymbionts of cnidarians and other marine phyla, produce O2 and assimilate CO2 , and thus potentially mitigate the exposure of the host to these stresses. However, such a role for Symbiodinium remains untested for non-calcifying cnidarians.
The climate change focus in Australia has shifted from mitigation to adaptation with an emphasis on place-specific case studies. The Barwon Estuary Complex (BEC) on the Bellarine Peninsula, central Victoria, was the focus of this place-specific study in which 37 local stakeholders were consulted through a series of semi-structured interviews on the impacts of climate change on their coastal community. Overall there was uniformity in stakeholder perceptions of the climate change impacts and vulnerabilities pertaining to the BEC.
The continuous increase of anthropogenic CO2 in the atmosphere resulting in ocean acidification has been reported to affect brain function in some fishes. During adulthood, cell proliferation is fundamental for fish brain growth and for it to adapt in response to external stimuli, such as environmental changes.
The resilience of tropical corals to ocean acidification depends on their ability to regulate the pH within their calcifying fluid (pHcf). Recent work suggests pHcf homeostasis under short-term exposure to pCO2 conditions predicted for 2100, but it is still unclear if pHcf homeostasis can be maintained throughout a corals lifetime. At CO2 seeps in Papua New Guinea, massive Porites corals have grown along a natural seawater pH gradient for decades. This natural gradient, ranging from pH 8.1-7.4, provides an ideal platform to determine corals' pHcf (using boron isotopes).
Freshwater discharge affects the biogeochemistry of river-influenced nearshore environments by contributing with carbon and nutrients. An increase in human activities in river basins may alter the natural riverine nutrients and carbon export to coastal ecosystems. Along a wide latitudinal range (32°55′S–40°10′S), this study explores the role of climate and land use in determining the nutrient and carbon concentrations in the river mouth and fluxes to adjacent coastal areas.
We present results of the CO2/carbonate system from the BIOSOPE cruise in the Eastern South Pacific Ocean, in an area not sampled previously. In particular, we present estimates of the anthropogenic carbon (C\textgreaterTrOCAant) distribution in the upper 1000 m of this region using the TrOCA method. The highest concentrations of CTrOCAant found around 13° S, 132° W and 32° S, 91° W, are higher than 80 $μ$mol.kg−1 and 70 $μ$mol.kg−1, respectively.
Exposure of the toxigenic dinoflagellate Alexandrium catenella to variations in pCO2/pH, comparable to current and near-future levels observed in Southern Chilean fjords, revealed potential functional adaptation mechanisms. Under calculated conditions for pH(total scale) and pCO2 ranging from 7.73–8.66 to 69.7–721.3 $μ$atm, respectively, the Chilean strain Q09 presented an optimum growth rate and dissolved inorganic carbon (DIC) uptake at near-equilibrium pCO2/pH conditions (∼8.1).
Rising atmospheric carbon dioxide (CO2) concentrations are causing additional CO2 to be absorbed by the oceans. Recent studies show that exposure to elevated CO2 causes olfactory impairment in reef fishes; however, the ecological consequences of this impairment are largely unknown. This study examined the effects of short-term exposure to elevated CO2 on habitat preferences of coral-dwelling gobies. Adult gobies collected from the reef at Lizard Island (Great Barrier Reef, Australia) were exposed for 4 days to ambient CO2 (440 $μ$atm) or elevated CO2 (880 $μ$atm).
Population outbreaks of the corallivorous crown-of-thorns starfish, Acanthaster planci, are a major contributor to the decline in coral reef across the Indo-Pacific. The success of A. planci and other reef species in a changing ocean will be influenced by juvenile performance because the naturally high mortality experienced at this sensitive life history stage maybe exacerbated by ocean warming and acidification. We investigated the effects of increased temperature and acidification on growth of newly metamorphosed juvenile A.
Changes in olfactory-mediated behaviour caused by elevated CO2 levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO2 will impact the other key part of the predator-prey interaction – the predators. We investigated the effects of elevated CO2 and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus).
Hypoxia and ocean acidification are two consequences of anthropogenic activities. These global trends occur on top of natural variability. In environments such as estuarine areas, short-term acute pH and O2 fluctuations are occurring simultaneously. The present study tested the combined effects of short-term seawater acidification and hypoxia on the physiology and energy budget of the thick shell mussel Mytilus coruscus. Mussels were exposed for 72 h to six combined treatments with three pH levels (8.1, 7.7 and 7.3) and two dissolved oxygen (DO) levels (2 mg L−1, 6 mg L−1).
In this paper, we demonstrated that ocean acidification (OA) had significant negative effects on the microscopic development of Saccharina japonica in a short-term exposure experiment under a range of light conditions. Under elevated CO2, the alga showed a significant reduction in meiospore germination, fecundity, and reproductive success. Larger female and male gametophytes were noted to occur under high CO2 conditions and high light magnified these positive effects.
We tested the effect of near-future CO2 levels (≈490, 570, 700, and 960 $μ$atm CO2) on the olfactory responses and activity levels of juvenile coral trout, Plectropomus leopardus, a piscivorous reef fish that is also one of the most important fisheries species on the Great Barrier Reef, Australia. Juvenile coral trout reared for 4 weeks at 570 $μ$atm CO2 exhibited similar sensory responses and behaviors to juveniles reared at 490 $μ$atm CO2 (control). In contrast, juveniles reared at 700 and 960 $μ$atm CO2 exhibited dramatically altered sensory function and behaviors.
Although there is a substantial body of work on how temperature shapes coastal marine ecosystems, the spatiotemporal variability of seawater pH and corresponding in situ biological responses remain largely unknown across biogeographic ranges of tropical coral species. Environmental variability is important to characterize because it can amplify or dampen the biological consequences of global change, depending on the functional relationship between mean temperature or pH and organismal traits.
1.Seaweeds are able to modify the chemical environment at their surface, in a micro‐zone called the diffusive boundary layer (DBL), via their metabolic processes controlled by light intensity. Depending on the thickness of the DBL, sessile invertebrates such as calcifying bryozoans or tube‐forming polychaetes living on the surface of the blades can be affected by the chemical variations occurring in this microlayer.
A geomorphic assessment of reef system calcification is conducted for past (3200 Ka to present), present and future (2010-2100) time periods. Reef platform sediment production is estimated at 569 m3 yr-1 using rate laws that express gross community carbonate production as a function of seawater aragonite saturation, community composition and rugosity and incorporating estimates of carbonate removal from the reef system. Key carbonate producers including hard coral, crustose coralline algae and Halimeda are mapped accurately (mean R2 = 0.81).
Rapid anthropogenic production of CO2 has driven the carbonate chemistry of the sea, causing lowered pH in surface waters. Increasingly, scientists are called on to study ocean acidification and its effects. The ‘minor' phylum Bryozoa shows considerable potential in understanding temperate southern hemisphere shelf carbonate dynamics, thus complementing tropical studies based mainly on corals. Lowered pH affects skeletons differently depending on their composition, but skeletons are even more strongly affected by morphology.
The unusual rate and extent of environmental changes due to human activities may exceed the capacity of marine organisms to deal with this phenomenon. The identification of physiological systems that set the tolerance limits and their potential for phenotypic buffering in the most vulnerable ontogenetic stages become increasingly important to make large-scale projections. Here, we demonstrate that the differential sensitivity of non-calcifying Ambulacraria (echinoderms and hemichordates) larvae towards simulated ocean acidification is dictated by the physiology of their digestive systems.
Understanding functional trait distributions among organisms can inform impacts on and responses to environmental change. In marine systems, only 1% of dissolved inorganic carbon in seawater exists as CO2. Thus the majority of marine macrophytes not only passively access CO2 for photosynthesis, but also actively transport CO2 and the more common bicarbonate (HCO3-, 92% of seawater dissolved inorganic carbon) into their cells.