Posts Tagged 'review'

Skeletons of calcareous benthic hydroids (Medusozoa, Hydrozoa) under ocean acidification

The skeleton plays a vital role in the survival of aquatic invertebrates by separating and protecting them from a changing environment. In most of these organisms, calcium carbonate (CaCO3) is the principal constituent of the skeleton, while in others, only a part of the skeleton is calcified, or CaCO3 is integrated into an organic skeleton structure. The average pH of ocean surface waters has increased by about 25% as a result of anthropogenic carbon dioxide (CO2) emissions, which reduces carbonate ions (CO32−) concentration, and saturation states (Ω) of biologically critical CaCO3 minerals like calcite, aragonite, and magnesian calcite (Mg-calcite), the fundamental building blocks for the skeletons of marine invertebrates. In this chapter, we discuss how ocean acidification (OA) affects particular species of benthic calcareous hydroids in order to bridge gaps and understand how these organisms can respond to a growing acidic ocean.

Continue reading ‘Skeletons of calcareous benthic hydroids (Medusozoa, Hydrozoa) under ocean acidification’

Climate change and harmful benthic microalgae

Highlights

• Global SST increases of 0.4–1.4 °C by 2055 will promote growth rates of many BHABs.

• Steep declines in growth are expected in areas where temperatures exceed 31 °C.

• Migration to deeper, cooler habitats may provide protection from high temperatures.

• Latitudinal range extensions to both the north and the south are expected.

• Changes in salinity, pH, light are secondary to temperature in regulating BHABs.

• Sentinel sites recommended for long-term monitoring to detect range extensions.

Abstract

Sea surface temperatures in the world’s oceans are projected to warm by 0.4–1.4 °C by mid twenty-first century causing many tropical and sub-tropical harmful dinoflagellate genera like Gambierdiscus, Fukuyoa and Ostreopsis (benthic harmful algal bloom species, BHABs) to exhibit higher growth rates over much of their current geographic range, resulting in higher population densities. The primary exception to this trend will be in the tropics where temperatures exceed species-specific upper thermal tolerances (30–31 °C) beyond which growth slows significantly. As surface waters warm, migration to deeper habitats is expected to provide refuge. Range extensions of several degrees of latitude also are anticipated, but only where species-specific habitat requirements can be met (e.g., temperature, suitable substrate, low turbulence, light, salinity, pH). The current understanding of habitat requirements that determine species distributions are reviewed to provide fuller understanding of how individual species will respond to climate change from the present to 2055 while addressing the paucity of information on environmental factors controlling small-scale distribution in localized habitats. Based on the available information, we hypothesized how complex environmental interactions can influence abundance and potential range extensions of BHAB species in different biogeographic regions and identify sentinel sites appropriate for long-term monitoring programs to detect range extensions and reduce human health risks.

Continue reading ‘Climate change and harmful benthic microalgae’

The impacts of climate change on the biomechanics of animals: themed issue article: biomechanics and climate change

Anthropogenic climate change induces unprecedented variability in a broad range of environmental parameters. These changes will impact material properties and animal biomechanics, thereby affecting animal performance and persistence of populations. Climate change implies warming at the global level, and it may be accompanied by altered wind speeds, wave action, ocean circulation, acidification as well as increased frequency of hypoxic events. Together, these environmental drivers affect muscle function and neural control and thereby movement of animals such as bird migration and schooling behaviour of fish. Altered environmental conditions will also modify material properties of animals. For example, ocean acidification, particularly when coupled with increased temperatures, compromises calcified shells and skeletons of marine invertebrates and byssal threads of mussels. These biomechanical consequences can lead to population declines and disintegration of habitats. Integrating biomechanical research with ecology is instrumental in predicting the future responses of natural systems to climate change and the consequences for ecosystem services such as fisheries and ecotourism.

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Swimming performance of marine fish larvae: review of a universal trait under ecological and environmental pressure

The larval phase of marine teleost fishes is characterized by important morphological and physiological modifications. Many of these modifications improve the larvae’s ability to swim, which satisfies a suite of crucial biological and ecological functions. Indeed, larval fish swimming performance has been considered a good proxy for overall condition, a predictor for growth and survival, and particularly helpful in assessing effects of natural and anthropogenic stress. Several methodologies have been developed to test larval fish swimming performance; however, measured swimming capabilities can strongly depend on the methodology utilised and developmental stage investigated. The aims of this review were, therefore, to link the ontogenetic development of swimming performance in early life stages of marine fishes, particularly the anatomical and physiological processes around the fins, muscles, and gills, with both the experimental methodologies used and the environmental stressors tested. We conducted a literature search and found 156 research papers relevant to swimming performance of marine teleost fish larvae. We found swimming performance to be highly variable among species and driven by temperature. In a meta-analysis focusing on the impacts of environmental stress on larval swimming performance, we found that prey reduction had the greatest impact on swimming. Methods used to evaluate swimming should keep the ontogenetic stage a focus, as forced swimming experiments are unfit for larvae prior to flexion of the notochord. Overall, while the data are deficient in some areas, we are able to highlight where the field of larval fish swimming could be directed and provide insight into which methods are best used under certain ecological scenarios, environmental stressors, and developmental stages.

Continue reading ‘Swimming performance of marine fish larvae: review of a universal trait under ecological and environmental pressure’

Behavioral defenses of shellfish prey under ocean acidification

Biological interactions between predators and prey constitute a key component of the ecology and evolution of marine systems, and animal behavior can affect the outcome of predator–prey interactions. It has been recently demonstrated that CO2-induced ocean acidification can alter the behavior of marine organisms and potentially alter predator–prey dynamics. This study combines both quantitative (meta-analysis) and qualitative approaches to review the effects of ocean acidification on behavioral prey defenses in marine invertebrates. A systematic literature search identified 34 studies that experimentally assessed behavioral defenses under elevated pCO2 spanning three phyla: crustaceans, echinoderms, and molluscs. A meta-analysis suggested that exposure to elevated seawater pCO2 can negatively affect behavioral defenses in bivalve molluscs and malacostracan crustaceans. By contrast, defenses of cephalopod molluscs seem to be positively impacted by elevated pCO2, whereas gastropods and echinoids appear unaffected. A qualitative assessment of studies on combined effects of ocean acidification and warming revealed that combined effects typically differ from ocean acidification–only effects. Based on a qualitative assessment of three studies to date, neurological interference of GABAA receptors under elevated pCO2 may play a major role in ocean acidification effects on prey defense behaviors; however, more research is needed, and other mechanistic underpinnings are also important to consider. Ultimately, the results of this study suggest that behavioral prey defenses in some shellfish taxa may be vulnerable to ocean acidification, that the effects of ocean acidification are often different under warming scenarios than under present-day temperature scenarios, and that GABAA interference may be an important mechanism underpinning behavioral responses of shellfish prey under ocean acidification. Despite the importance of shellfish behavioral defenses in the ecology and evolution of marine biological communities, however, research to date has only scraped the surface in understanding ocean acidification effects. Increased research efforts on the effects of multiple stressors, acclimation and adaptation, environmental variability, and complex situational and ecological contexts are needed. Studies of fish behavioral defenses under ocean acidification can help streamline hypotheses and experimental approaches, particularly given the similar effects of elevated pCO2 on GABAA function.

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Establishing the link between Permian volcanism and biodiversity changes: insights from geochemical proxies

Highlights

• Current understanding of biodiversity changes in the Permian is summarized.

• Conventional and non-traditional geochemical proxy records in the Permian are assessed.

• Main characteristics of four Permian large igneous provinces are compared.

• The potential links between the Siberian Traps and EPME, and the Emeishan LIP and EGME, are examined.

• In addition to the Siberian Traps, continental arc magmatism could also played an important role in the EPME.

Abstract

Current understanding of biodiversity changes in the Permian is presented, especially the consensus and disagreement on the tempo, duration, and pattern of end-Guadalupian and end-Permian mass extinctions. The end-Guadalupian mass extinction (EGME; i.e., pre-Lopingian crisis) is not as severe as previously thought. Moreover, the turnovers of major fossil groups occurred at different temporal levels, therefore the total duration of the end-Guadalupian mass extinction is relatively extended. By comparison, fossil records constrained with high-precision geochronology indicate that the end-Permian mass extinction (EPME) was a single-pulse event and happened geologically instantaneous. Variation of geochemical proxies preserved in the sedimentary records is important evidence in examining potential links between volcanisms and biodiversity changes. Some conventional and non-traditional geochemical proxy records in the Permian show abrupt changes across the Permian-Triassic boundary, reflecting climate change, ocean acidification and anoxia, carbon cycle perturbation, gaseous metal loading, and enhanced continental weathering. These, together with the stratigraphic coincidence between volcanic ashes and the end-Permian mass extinction horizon, point to large-scale volcanism as a potential trigger mechanism.

To further define the nature of volcanism which was responsible for global change in biodiversity, main characteristics of four Permian large igneous provinces (LIPs; i.e., Tarim, Panjal, Emeishan, and Siberian) are compared, in terms of timing and tempo, spatial distribution and volume, and magma-wall rock interactions. The comparison indicates that volcanic fluxes (i.e., eruption rates) and gas productions are the key features distinguishing the Siberian Traps from other LIPs, which also are the primary factors in determining the LIP’s potential of affecting Earth’s surface system. We find that the Siberian Traps volcanism, especially the switch from dominantly extrusive eruptions to widespread sill intrusions, has the strongest potential for destructive impacts, and most likely is the ultimate trigger for profound environmental and biological changes in the latest Permian-earliest Triassic. The role of Palaeotethys subduction-related arc magmatism cannot be fully ruled out, given its temporal coincidence with the end-Permian mass extinction. As for the Emeishan LIP, medium volcanic flux and gas emission probably limited its killing potential, as evident from weak changes in geochemical proxies and biodiversity. Because of its long-lasting but episodic nature, the Early Permian magmatism (e.g., Tarim, and Panjal) may have played a positive role in affecting the contemporaneous environment, as implicated by coeval progressive climate warming, termination of the Late Palaeozoic Ice Age (LPIA), and flourishing of ecosystems.

Continue reading ‘Establishing the link between Permian volcanism and biodiversity changes: insights from geochemical proxies’

Air–sea CO2 exchange and ocean acidification in UK seas and adjacent waters

Ongoing anthropogenic emissions of carbon dioxide (CO2) into the atmosphere are driving a net flux of CO2 into the ocean globally, resulting in a decline in pH called ‘ocean acidification’. Here, we discuss the consequences of this for the seas surrounding the UK from a chemical perspective, focussing on studies published since the previous MCCIP review of ocean acidification research (Williamson et al., 2017). In this reporting cycle, the biological, ecological, and socio-economic impacts of ocean acidification are considered in more detail in separate accompanying MCCIP reviews.

The atmospheric CO2 concentration continues to increase due to human activities (Le Quéré et al., 2018), increasing the net flux of CO2 into the global ocean, including the North Atlantic and UK continental shelf seas. Such CO2 uptake has the desirable effect of reducing the rate of climate change, but the undesirable result of ocean acidification. Our understanding of the factors that drive high spatial and temporal variability in air-sea CO2 fluxes and seawater pH in UK waters has continued to improve, thanks to observational campaigns both across the entire North-West European continental shelf sea and at specific time–series sites. Key challenges for the future include sustaining time–series observations of near-surface marine carbonate system variables, and of the auxiliary parameters required for their interpretation (e.g. temperature, salinity, and nutrients); developing and deploying new sensor technology for full water-column profiles and pore waters in seafloor sediments; and increasing the spatial and temporal resolution of models sufficiently to capture the complex processes that dominate the marine carbonate system in coastal and shelf sea environments, along with improving how those processes are themselves simulated.

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Ocean acidification in the IPCC AR5 WG II

OUP book