Posts Tagged 'review'

An overview upon CO₂ – possible source of ocean acidification

The interest upon CO₂ concentrations introduced in the atmosphere by human activities enhances year after year because of the consequences on the atmosphere, land and oceans. Many studies showed that changes in the ocean carbon cycle are due to the absorption of anthropogenic CO₂ from the atmosphere. The increase of CO₂ has been correlated with the pH falling of seawaters, promoting a critical process known as acidification. Ocean acidification could modify many biochemical cycles and functioning of marine organisms. The aim of this paper is to demonstrate the chemistry behaviour of CO₂ on seawaters. Once dissolved in seawater, CO₂ reacts with water to form carbonic acid (H₂CO₃). Ocean stores CO₂ as dissolved inorganic carbon (DIC) which remains in the form of dissolved CO₂ and H₂CO₃, while the rest is in the form of HCO₃⁻ and CO₃²⁻. Adding CO₂ to seawater, thus increase HCO₃⁻ that bring about a decrease in ocean water pH by increasing H+ concentration.

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Major impacts of climate change on deep-sea benthic ecosystems

The deep sea encompasses the largest ecosystems on Earth. Although poorly known, deep seafloor ecosystems provide services that are vitally important to the entire ocean and biosphere. Rising atmospheric greenhouse gases are bringing about significant changes in the environmental properties of the ocean realm in terms of water column oxygenation, temperature, pH and food supply, with concomitant impacts on deep-sea ecosystems. Projections suggest that abyssal (3000–6000 m) ocean temperatures could increase by 1°C over the next 84 years, while abyssal seafloor habitats under areas of deep-water formation may experience reductions in water column oxygen concentrations by as much as 0.03 mL L–1 by 2100. Bathyal depths (200–3000 m) worldwide will undergo the most significant reductions in pH in all oceans by the year 2100 (0.29 to 0.37 pH units). O2 concentrations will also decline in the bathyal NE Pacific and Southern Oceans, with losses up to 3.7% or more, especially at intermediate depths. Another important environmental parameter, the flux of particulate organic matter to the seafloor, is likely to decline significantly in most oceans, most notably in the abyssal and bathyal Indian Ocean where it is predicted to decrease by 40–55% by the end of the century. Unfortunately, how these major changes will affect deep-seafloor ecosystems is, in some cases, very poorly understood. In this paper, we provide a detailed overview of the impacts of these changing environmental parameters on deep-seafloor ecosystems that will most likely be seen by 2100 in continental margin, abyssal and polar settings. We also consider how these changes may combine with other anthropogenic stressors (e.g., fishing, mineral mining, oil and gas extraction) to further impact deep-seafloor ecosystems and discuss the possible societal implications.

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Southern Ocean phytoplankton in a changing climate

Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced salinity, and the southward migration of ocean fronts. These changes are expected to alter the structure and function of phytoplankton communities in the SO. The diverse environments contained within the vast expanse of the SO will be impacted differently by climate change; causing the identity and the magnitude of environmental factors driving biotic change to vary within and among bioregions. Predicting the net effect of multiple climate-induced stressors over a range of environments is complex. Yet understanding the response of SO phytoplankton to climate change is vital if we are to predict the future state/s of the ecosystem, estimate the impacts on fisheries and endangered species, and accurately predict the effects of physical and biotic change in the SO on global climate. This review looks at the major environmental factors that define the structure and function of phytoplankton communities in the SO, examines the forecast changes in the SO environment, predicts the likely effect of these changes on phytoplankton, and considers the ramifications for trophodynamics and feedbacks to global climate change. Predictions strongly suggest that all regions of the SO will experience changes in phytoplankton productivity and community composition with climate change. The nature, and even the sign, of these changes varies within and among regions and will depend upon the magnitude and sequence in which these environmental changes are imposed. It is likely that predicted changes to phytoplankton communities will affect SO biogeochemistry, carbon export, and nutrition for higher trophic levels.

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Linking the biological impacts of ocean acidification on oysters to changes in ecosystem services: A review

Continued anthropogenic carbon dioxide emissions are acidifying our oceans, and hydrogen ion concentrations in surface oceans are predicted to increase 150% by 2100. Ocean acidification (OA) is changing ocean carbonate chemistry, including causing rapid reductions in calcium carbonate availability with implications for many marine organisms, including biogenic reefs formed by oysters. The impacts of OA are marked. Adult oysters display both decreased growth and calcification rates, while larval oysters show stunted growth, developmental abnormalities, and increased mortality. These physiological impacts are affecting ecosystem functioning and the provision of ecosystem services by oyster reefs. Oysters are ecologically and economically important, providing a wide range of ecosystem services, such as improved water quality, coastlines protection, and food provision. OA has the potential to alter the delivery and the quality of the ecosystem services associated with oyster reefs, with significant ecological and economic losses. This review provides a summary of current knowledge of OA on oyster biology, but then links these impacts to potential changes to the provision of ecosystem services associated with healthy oyster reefs.

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Adaptation policies and strategies as a response to ocean acidification and warming in the Mediterranean Sea

1. Introduction

The ocean are a fundamental component of the Earth’s climate regulation, life and its carbon cycle. By burning fossil fuels since the Industrial Revolution, and thus emitting large amounts of carbon into the atmosphere, humans are changing the ocean in several ways. In particular, the ocean is absorbing atmospheric carbon dioxide (CO2) at such an unprecedented rate that it is rapidly changing its chemistry, resulting in “ocean acidification”, a reduction in pH, carbonate ion concentration and the ocean’s buffering capacity. Ocean acidification is a global environmental issue posing a threat to open ocean and coastal marine ecosystems, including semi-enclosed seas such as the Mediterranean Sea. (…)

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Ocean acidification: impacts and governance

1. What is ocean acidification?

The ocean provides a vital benefit to human society by absorbing one-fourth of all man-made carbon dioxide (CO2) released into the atmosphere, thus substantially limiting climate change (Le Quéré et al. 2015). However, oceanic CO2 uptake come with a cost. Known s “the other CO2 problem”, ocean acidification is a new and emerging challenge for sustainable development and ocean governance. In short, the term describes a series of chemical changes occurring when atmospheric CO2 dissolves in seawater, with potentially dire consequences for marine organisms, ecosystems and the services they provide. (…)

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KrillDB: A de novo transcriptome database for the Antarctic krill (Euphausia superba)

Antarctic krill (Euphausia superba) is a key species in the Southern Ocean with an estimated biomass between 100 and 500 million tonnes. Changes in krill population viability would have catastrophic effect on the Antarctic ecosystem. One looming threat due to elevated levels of anthropogenic atmospheric carbon dioxide (CO2) is ocean acidification (lowering of sea water pH by CO2 dissolving into the oceans). The genetics of Antarctic krill has long been of scientific interest for both for the analysis of population structure and analysis of functional genetics. However, the genetic resources available for the species are relatively modest. We have developed the most advanced genetic database on Euphausia superba, KrillDB, which includes comprehensive data sets of former and present transcriptome projects. In particular, we have built a de novo transcriptome assembly using more than 360 million Illumina sequence reads generated from larval krill including individuals subjected to different CO2 levels. The database gives access to: 1) the full list of assembled genes and transcripts; 2) their level of similarity to transcripts and proteins from other species; 3) the predicted protein domains contained within each transcript; 4) their predicted GO terms; 5) the level of expression of each transcript in the different larval stages and CO2 treatments. All references to external entities (sequences, domains, GO terms) are equipped with a link to the appropriate source database. Moreover, the software implements a full-text search engine that makes it possible to submit free-form queries. KrillDB represents the first large-scale attempt at classifying and annotating the full krill transcriptome. For this reason, we believe it will constitute a cornerstone of future approaches devoted to physiological and molecular study of this key species in the Southern Ocean food web.

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Ocean acidification in the IPCC AR5 WG II

OUP book