Posts Tagged 'review'

Background briefs for 2020 Ocean Pathways Week: Impacts of climate change and ocean acidification on marine biodiversity

At the forefront of various threats to the ocean and its organisms, habitats and ecosystems is climate change, which interacts with other human-induced pressures such as pollution, eutrophication and over-exploitation of marine resources.

Climate-related drivers impacting the ocean include so-called ‘slow-onset events’ such as ocean warming, acidification, deoxygenation, sea level rise and glacial retreat, alongside extreme weather events such as marine heat waves and increased frequency of storms. These are all likely to drive biodiversity shifts in different ways, particularly in biodiversity hotspots such as coral reefs and other ecosystems that provide important services for coastal communities. The overall impact of climate change and ocean acidification on marine biodiversity is difficult to predict, as it involves complex interactions between organisms. Different species may either struggle or thrive in response to changing ocean conditions, depending on their specific tolerance limits or indirectly due to changes in species interactions and habitat loss. While precise predictions are currently not possible, it is certain that marine ecosystems will change and marine biodiversity will decrease, at least in the short term.

Continue reading ‘Background briefs for 2020 Ocean Pathways Week: Impacts of climate change and ocean acidification on marine biodiversity’

Defining CO2 and O2 syndromes of marine biomes in the anthropocene

Research efforts have intensified to foresee the prospects for marine biomes under climate change and anthropogenic drivers over varying temporal and spatial scales. Parallel with these efforts is the utilization of terminology, such as ‘ocean acidification’ (OA) and ‘ocean deoxygenation’ (OD), that can foster rapid comprehension of complex processes driving carbon dioxide (CO2) and oxygen (O2) concentrations in the global ocean and thus, are now widely used in discussions within and beyond academia. However, common usage of the terms ‘acidification’ and ‘deoxygenation’ alone are subjective and, without adequate contextualization, have the potential to mislead inferences over drivers that may ultimately shape the future state of marine ecosystems. Here we clarify the usage of the terms OA and OD as global, climate change‐driven processes and discuss the various attributes of elevated CO2 and reduced O2 syndromes common to coastal ecosystems. We support the use of the existing terms ‘coastal acidification’ and ‘coastal deoxygenation’ because they help differentiate the sometimes rapid and extreme nature of CO2 and O2 syndromes in coastal ecosystems from the global, climate change‐driven processes of OA and OD. Given the complexity and breadth of the processes involved in altering CO2 and O2 concentrations across marine ecosystems, we provide a workflow to enable contextualization and clarification of the usage of existing terms and highlight the close link between these two gases across spatial and temporal scales in the ocean. These distinctions are crucial to guide effective communication of research within the scientific community and guide policymakers responsible for intervening on the drivers to secure desirable future ocean states.

Continue reading ‘Defining CO2 and O2 syndromes of marine biomes in the anthropocene’

Ocean acidification as a multiple driver: how interactions between changing seawater carbonate parameters affect marine life

‘Multiple drivers’ (also termed ‘multiple stressors’) is the term used to describe the cumulative effects of multiple environmental factors on organisms or ecosystems. Here, we consider ocean acidification as a multiple driver because many inorganic carbon parameters are changing simultaneously, including total dissolved inorganic carbon, CO2, HCO3–, CO32–, H+ and CaCO3 saturation state. With the rapid expansion of ocean acidification research has come a greater understanding of the complexity and intricacies of how these simultaneous changes to the seawater carbonate system are affecting marine life. We start by clarifying key terms used by chemists and biologists to describe the changing seawater inorganic carbon system. Then, using key groups of non-calcifying (fish, seaweeds, diatoms) and calcifying (coralline algae, coccolithophores, corals, molluscs) organisms, we consider how various physiological processes are affected by different components of the carbonate system.

Continue reading ‘Ocean acidification as a multiple driver: how interactions between changing seawater carbonate parameters affect marine life’

Coralline algae in a changing Mediterranean Sea: how can we predict their future, if we do not know their present?

In this review we assess the state of knowledge for the coralline algae of the Mediterranean Sea, a group of calcareous seaweeds imperfectly known and considered highly vulnerable to long-term climate change. Corallines have occurred in the Mediterranean area for ~140 My and are well-represented in the subsequent fossil record; for some species currently common the fossil documentation dates back to the Oligocene, with a major role in the sedimentary record of some areas. Some Mediterranean corallines are key ecosystem engineers that produce or consolidate biogenic habitats (e.g., coralligenous concretions, Lithophyllum byssoides rims, rims of articulated corallines, maerl/rhodolith beds). Although bioconstructions built by corallines exist virtually in every sea, in the Mediterranean they reach a particularly high spatial and bathymetric extent (coralligenous concretions alone are estimated to exceed 2,700 km2 in surface). Overall, composition, dynamics and responses to human disturbances of coralline-dominated communities have been well-studied; except for a few species, however, the biology of Mediterranean corallines is poorly known. In terms of diversity, 60 species of corallines are currently reported from the Mediterranean. This number, however, is based on morphological assessments and recent studies incorporating molecular data suggest that the correct estimate is probably much higher. The responses of Mediterranean corallines to climate change have been the subject of several recent studies that documented their tolerance/sensitivity to elevated temperatures and pCO2. These investigations have focused on a few species and should be extended to a wider taxonomic set. Phylogeography, genomics, transcriptomics, and associated microbiomes are fields in which the information for Mediterranean corallines is very limited. We suggest that future work on Mediterranean corallines should be based on a multidisciplinary perspective combining different approaches, and that it should consist of large-scale efforts by scientists based both in western and eastern Mediterranean areas.

Continue reading ‘Coralline algae in a changing Mediterranean Sea: how can we predict their future, if we do not know their present?’

Behavioral responses to ocean acidification in marine invertebrates: new insights and future directions

Ocean acidification (OA) affects marine biodiversity and alters the structure and function of marine populations, communities, and ecosystems. Recently, effects of OA on the behavioral responses of marine animals have been given with much attention. While many of previous studies focuses on marine fish. Evidence suggests that marine invertebrate behaviors were also be affected. In this review, we discussed the effects of C02-driven OA on the most common behaviors studied in marine invertebrates, including settlement and habitat selection, feeding, anti-predatory, and swimming behaviors, and explored the related mechanisms behind behaviors. This review summarizes how OA affects marine invertebrate behavior, and provides new insights and highlights novel areas for future research.

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Ecological effects of elevated CO2 on marine and freshwater fishes: from individual to community effects

Research over the past decade has shown that climate-change relevant CO2 levels can affect the growth, development and survival of some fishes during early life. There are also wide-ranging effects on behavior that could alter performance and survivorship of some species. Yet, there is also substantial variation in the sensitivity of fishes to elevated CO2, both among and within species. This chapter explores the current understanding of ecological effects of projected future CO2 levels on marine and freshwater fishes, including major knowledge gaps and uncertainties, and interactions with other stressors such as global warming. While laboratory experiments show that elevated CO2 can affect ecologically important traits of some species, we are not yet able to predict which species are sensitive and which are tolerant to higher CO2 levels. Moreover, the impacts of elevated CO2 on ecologically relevant traits can depend on food availability and interact with elevated temperature and other stressors in unexpected ways. New studies also demonstrate that natural CO2 variation and ecological complexity can mitigate some of the negative effects of elevated CO2 observed in simplified laboratory experiments. Finally, studies at natural CO2 seeps suggest that indirect effects of elevated CO2 on food resources and habitats may have larger effects on fish populations than the direct effects of elevated CO2 on individual performance.

Continue reading ‘Ecological effects of elevated CO2 on marine and freshwater fishes: from individual to community effects’

CO2 and acid-base sensing

Carbon dioxide (CO2) and its hydration products hydrogen (H+), bicarbonate and carbonate ions collectively contribute to the acid-base status of aqueous solutions, and have major effects on the physiology of organisms. Correspondingly, organisms have developed the ability to sense specific acid-base disturbances that routinely arise from metabolic and environmental sources, and to coordinate a variety of homeostatic responses. A common requirement for all homeostatic mechanisms is the ability to sense specific acid-base disturbances and to coordinate appropriate responses. This chapter synthetizes our knowledge concerning the sensory pathways that allow fish to sense acid-base disturbances of both metabolic and environmental origin and the ensuing downstream physiological responses that promote homeostasis in different organs. We focus largely on the peripheral, and to a lesser extent, the central sites of CO2/H+ detection, emphasizing the cellular sites and molecular mechanisms of acid-base sensing.

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Ocean acidification in the IPCC AR5 WG II

OUP book