Posts Tagged 'review'

Can shellfish adapt to ocean acidification?

Scientists peer into oyster and clam genomes to help the shellfish industry prepare for a change in ocean chemistry.

In the Pacific Northwest, oyster aficionados have likely tasted Chris Langdon’s scientific handiwork. Since 1996, his Molluscan Broodstock Program at Oregon State University has been breeding plump, fast-growing, and hardy oysters as stock for the $250 million West Coast oyster industry. But in the past several years, the program has taken on an additional goal: identifying oysters that are more resilient to ocean acidification.

In 2007, oyster hatcheries in Oregon and Washington began experiencing massive die-offs of their larvae that continued for several years. Eventually, managers and scientists realized that the larvae were dying during periods of strong upwelling, when deep waters rich in CO2 and low in pH come to the surface. These deep waters were even more acidified than in the past because of the oceans’ growing uptake of CO2 as its levels in the atmosphere increase. (…)

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Les systèmes aquacoles face au changement climatique (in French)

L’aquaculture contribue aujourd’hui pour environ 50 % à l’approvisionnement en ressources aquatiques destinées à la consommation humaine et cette part est amenée à s’accroître à l’avenir compte tenu de la stagnation des captures liées à la pêche. Si un certain nombre de travaux ont été effectués en vue d’évaluer l’impact du changement climatique sur la pêche, peu a encore été fait dans ce domaine sur l’aquaculture. Cet article de synthèse tente d’identifier les défis auxquels l’aquaculture aura à faire face dans un contexte de changement climatique et propose des voies, à la fois adaptatives et innovantes, pour répondre à ces défis. L’article se focalise particulièrement sur six composantes de l’environnement susceptibles de subir des modifications sous l’effet du changement climatique et d’avoir un impact direct sur l’aquaculture : l’augmentation du niveau des mers ; la modification de la température ; les précipitations, les crues et les sécheresses ; la disponibilité en eau ; la dégradation de la qualité des eaux et enfin l’acidification des océans. Les impacts indirects concernent quant à eux principalement l’approvisionnement en farine et huile de poissons, constituants stratégiques des aliments destinés aux élevages d’animaux aquatiques, dont la disponibilité est dépendante des débarquements des pêches minotières, elles-mêmes sensibles au changement climatique. Face au changement climatique, deux stratégies sont possibles. La première, adaptative, consiste à mettre en œuvre des solutions qui permettent de prendre en compte les modifications du milieu (espèce adaptée, sélection de site) ; la deuxième consiste à imaginer des systèmes où les facteurs du milieu sont rigoureusement maîtrisés. Réciproquement, l’impact de l’aquaculture sur le changement climatique est évoqué. Enfin, les résultats d’une enquête conduite par la FAO en 2016 sur la situation des mesures prises dans diverses parties du monde pour faire face au changement climatique en matière d’aquaculture sont exposés.

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Does ocean acidification even matter?

The chemistry of the ocean is changing ten times faster than at any other time during the past 50 million years and at least 100 times faster than at any other time in the last 20 million years. By the year 2200, under a business-as-usual scenario for fossil-fuel consumption, the increasing acidity of seawater could have serious impacts on coral reefs and associated ecosystems presumably with ripple effects throughout the food chain. It can be anticipated that such changes will affect all the other services that seas and oceans provide. That, of course, will have profound effects on coastal economies (fisheries, tourism, biodiversity and so on). The reader is taken through the issues and briefed on the need for robust global dialogue and political processes.

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A review on ocean acidification as a result of shipping emissions in harbors

In conjunction with global warming, ocean acidification has become a pressing problem, particularly in sensitive areas such as the Great Barrier Reef. Even though acidification from emissions is spatially non-uniform, it helps in understanding of changes in pH values in surface ocean waters. While averaged across the world’s oceans, ship emissions may have a relatively minor role in total ocean acidification, the intense activity of ships in ports and in shipping lanes can lead to a measurable reduction in pH levels. This occurs due to uptake of exhaust gases such as nitrogen and sulphur oxides and carbon dioxide across the air-sea interface. In other words, polluting emissions get chemically dissolved into the near surface of the sea causing the ocean to turn more acidic. This trend – which in modern times has basically begun since the Industrial Revolution – is considered harmful in a number of direct and indirect ways, including the threat to marine life and the food chain cycle. Several major attempts have been implemented worldwide to tackle the problem, such as emission control and climate engineering. Fleet emission of international trade is believed to highly impact this pattern, since ships are among the world’s highest polluting combustion sources per quantity of fuel consumed. Ship emissions are significantly increasing globally and have remarkably adverse impacts on air quality, on both sea and land. These emissions contribute to seriously harmful health and environmental effects. Territorial waters, inland seas and ports are the areas mostly affected by these emissions. In the search for a sustainable and effective solution, it is important that proper measures are taken in terms of controlling, improving and reducing emissions. Significant progress in estimating international ship emissions has been made in the past decade, however its impact on shore waters is a question requiring deeper attention. Conducting these kinds of research may be seen as useful tools for the improvement of maritime legislation on emissions. This paper is presenting an overview on the same matter, its basic concepts and general knowledge in hand as well as physics and chemistry behind the subject.

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Climate, anchovy, and sardine

Anchovy and sardine populated productive ocean regions over hundreds of thousands of years under a naturally varying climate, and are now subject to climate change of equal or greater magnitude occurring over decades to centuries. We hypothesize that anchovy and sardine populations are limited in size by the supply of nitrogen from outside their habitats originating from upwelling, mixing, and rivers. Projections of the responses of anchovy and sardine to climate change rely on a range of model types and consideration of the effects of climate on lower trophic levels, the effects of fishing on higher trophic levels, and the traits of these two types of fish. Distribution, phenology, nutrient supply, plankton composition and production, habitat compression, fishing, and acclimation and adaptation may be affected by ocean warming, acidification, deoxygenation, and altered hydrology. Observations of populations and evaluation of model skill are essential to resolve the effects of climate change on these fish.

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Multiple stressors and the functioning of coral reefs

Coral reefs provide critical services to coastal communities, and these services rely on ecosystem functions threatened by stressors. By summarizing the threats to the functioning of reefs from fishing, climate change, and decreasing water quality, we highlight that these stressors have multiple, conflicting effects on functionally similar groups of species and their interactions, and that the overall effects are often uncertain because of a lack of data or variability among taxa. The direct effects of stressors on links among functional groups, such as predator-prey interactions, are particularly uncertain. Using qualitative modeling, we demonstrate that this uncertainty of stressor impacts on functional groups (whether they are positive, negative, or neutral) can have significant effects on models of ecosystem stability, and reducing uncertainty is vital for understanding changes to reef functioning. This review also provides guidance for future models of reef functioning, which should include interactions among functional groups and the cumulative effect of stressors.

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Anthropogenic forcing of carbonate and organic carbon preservation in marine sediments

Carbon preservation in marine sediments, supplemented by that in large lakes, is the primary mechanism that moves carbon from the active surficial carbon cycle to the slower geologic carbon cycle. Preservation rates are low relative to the rates at which carbon moves between surface pools, which has led to the preservation term largely being ignored when evaluating anthropogenic forcing of the global carbon cycle. However, a variety of anthropogenic drivers—including ocean warming, deoxygenation, and acidification, as well as human-induced changes in sediment delivery to the ocean and mixing and irrigation of continental margin sediments—all work to decrease the already small carbon preservation term. These drivers affect the cycling of both carbonate and organic carbon in the ocean. The overall effect of anthropogenic forcing in the modern ocean is to decrease delivery of carbon to sediments, increase sedimentary dissolution and remineralization, and subsequently decrease overall carbon preservation.

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Ocean acidification in the IPCC AR5 WG II

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