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Ocean acidification in the IPCC Special Report: Global Warming of 1.5°C

Ocean acidification is mentioned in the Intergovernmental Panel on Climate Change (IPCC) Special Report: Global Warming of 1.5°C, released today, 8 October 2018. An overview of ocean acidification is given in chapter 3 section 3.10 titled Ocean Chemistry.

Ocean acidification is also included in a global synthesis table summarising the assessments of global and regional climate changes and associated hazards in section 3.3.11.

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Policy brief: Ocean-based measures for climate action

Current emission reduction pledges under the 2015 Paris Agreement are insufficient to keep global temperature “well below +2°C” in 2100 relative to pre-industrial levels and to reach targets of the United Nations Sustainable Development Goals. Increased political ambition is therefore required, as well as enhanced efforts in terms of both mitigation and ecosystem and human adaptation. There is growing evidence high- lighting both the role the ocean plays in mitigating anthropogenic climate change (i.e., absorption of atmospheric heat and anthropogenic carbon), and the cascading consequences on its chemistry and physics (i.e., ocean warming, acidification, deoxygenation, sea-level rise), ecosystems and ecosystem services. In such a context, a critical question arises: what are the ocean-based opportunities for climate action? In other words, what is the potential of the ocean and its ecosystems to reduce the causes of climate change and its impacts?

This document summarises the main findings of The Ocean Solutions Initiative that assessed the potential of 13 ocean-based measures.

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Ocean acidification and hypoxia council makes first recommendations to state legislature

Oregon is among the first places to document the impacts of “ocean acidification”— what happens when human-produced carbon dioxide is absorbed by seawater, resulting in chemical reactions that change the water’s pH and make it more acidic. Oregon is meeting this problem head on, most recently with the convening of the Oregon Coordinating Council on Ocean Acidification and Hypoxia.

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SDG Indicator 14.3.1 Methodology accepted by the IOC-UNESCO Executive Council

During its 51st Executive Council Meeting from 3-6 July 2018, the Member States of the Intergovernmental Oceanographic Commission (IOC) of UNESCO welcomed the Methodology for the Sustainable Development Goal (SDG) Target Indicator 14.3.1 and recommended to the IOC secretary as the custodian agency for this indicator to propose its upgrade from Tier III to Tier II. The SDG Target Indicator 14.3.1 calls for “average marine acidity measured at an agreed suite of representative sampling stations“. The Methodology provides guidance to scientists and countries about how to carry out measurements following the best practices established by experts in the ocean acidification community, including members of the Global Ocean Acidification Observing Network (GOA-ON), and explains how to report the collected information.
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California mussels as bioindicators of ocean acidification

A critical need in California is to develop robust biological indicators that can be used to understand emerging impacts to marine systems arising from human-induced global change. Among the most worrisome environmental stressors are those associated with shifts in the carbonate system of seawater, including reductions in ocean pH and decreased availability of carbonate ions (together termed ‘ocean acidification’). In this study, we explored the utility of employing newly settled California mussels (Mytilus californianus) as a bio-indicator of effects of ocean acidification. Our approach involved a field assessment of the capacity to link patterns of mussel recruitment to climate-related oceanographic drivers, with the additional step of conducting measurements of mussel morphology and body condition to maximize the sensitivity of the bio-indicator. Our results indicate that larval shells retained in mussels that have settled on the shore are smaller in area when larval stages were likely to have been subjected to more acidic (lower-pH) seawater. Similarly, the body condition — a measure of general health — of newly settled juveniles subjected to lower-pH seawater was reduced in cases where those waters were also warm. These findings suggest a strong potential for newly settled California mussels to serve as informative bio-indicators of ocean acidification in California’s coastal waters. Future efforts should pursue additional validation and possible expansion of this methodology, as well as the feasibility of a sustained commitment to sampling newly settled individuals of this species at multiple locations throughout the State.

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Acidification in Nordic waters: status, trends and implications for marine species

Recent studies on marine life show that the anthropogenic increase in atmospheric CO2 concentration can have negative impacts on growth and survival of groups of marine life such as corals and other calcifying organisms.

Increased CO2 concentration in the atmosphere, and hence in the oceans, lead to decreasing pH or increasing acidification, a process known as ocean acidification (OA). During the last century, the CO2 concentration in the atmosphere has risen from around 280 ppm to 400 ppm; this has led to a pH decrease in the oceans of 0.1. OA currently takes place at a rate corresponding to approximately -0.02 pH unit per decade and an increase in CO2 at around 2 ppm per year. The projections for atmospheric CO2 concentration is an increase to around 1000 ppm at the end of the century, which will lower pH in the oceans by 0.3-0.4. Although this may appear relatively small, a decrease in pH of 0.1 corresponds to an increase in acidity (“free” protons) of 25%, and 0.3-0.4 corresponds to an increase of 200-250%.

Coastal systems experience changes in pH over time exceeding those of the ocean by several orders of magnitude,
but the field is poorly studied, and the spatial variation is large. The Baltic Sea is no exception to this. pH changes in the Baltic Sea are tightly coupled to nutrient input, alkalinity (AT) of freshwater sources in addition to increased CO2 levels and warming. Acidification trends vary substantially among coastal systems and time of year, but have been reported up to 10 times faster than OA.

The TRIACID project has mapped acidification trends in the Baltic Sea during the past 40 years, in different regions, and identified areas with a general lack of data. The project has described spatial variation and trends in pH status, and the main drivers of changing pH have been identified. Given the spatial variation, the data gaps, and all the different drivers a detailed projection of the development is complicated but since we expect increasing CO2 concentration in the atmosphere, rising temperatures and decreasing nutrient input, the acidification trend will continue or accelerate in most of the region.

Continue reading ‘Acidification in Nordic waters: status, trends and implications for marine species’

The effects of climate change and ocean acidification on Corallina seaweeds

Significant increases in the concentrations of greenhouse gases in the Earth’s atmosphere owing to human combustion of fossil fuels and deforestation, is having profound effects on the world’s oceans. Two of the main effects on the marine environment are increased sea surface temperatures due to climate change, and ocean acidification. Increased sea surface temperatures are caused by the global warming effect of climate change. As the world’s atmosphere warms up, our oceans slowly absorb the heat. To date, the oceans have absorbed over 80% of the heat added to the atmosphere by climate change. This has caused an increase in global average sea surface temperature of approximately 0.69oC.

Ocean acidification refers to a decrease in ocean pH (increasing acidity) over decades or more that is caused by uptake of carbon dioxide (CO2) from the atmosphere. Because human activities are releasing CO2 into the atmosphere very quickly (a major cause of climate change), the ocean is taking up CO2 faster today than it has in the past. When CO2 dissolves in seawater, it acts like a weak acid and, through a series of chemical reactions, causes an increase in the acidity of the seawater, i.e. an increase in free hydrogen ions (H+). Additionally, increased CO2 concentration in seawater also causes a reduction in carbonate ions (CO32+), which are very important building blocks of calcifying marine species, i.e. those species that deposit shells, tubes, or other skeletal structures out of calcium carbonate (CaCO3), e.g. corals. Since the industrial revolution, the pH of the world’s oceans has decreased by approximately 0.1 units, which represents a 30% increase in H+ ions and a significant decrease in the availability of CO32+ to marine species.

As humans continue to release greenhouse gases into the atmosphere, climate change and ocean acidification will continue at a speed never seen before in the Earth’s history. Predictions of future concentrations of greenhouse gases in the atmosphere made by the Intergovernmental Panel on Climate Change (IPCC), show that by the year 2100 we can expect increases in sea surface temperature of approximately + 4oC and a further decrease in pH of 0.3 – 0.5 units (i.e. a 90 – 150% increase in hydrogen ions).

Continue reading ‘The effects of climate change and ocean acidification on Corallina seaweeds’


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