| Summary: | This paper presents a summary of the state of knowledge on ocean acidification.Summary of outcomes:The ocean continues to acidify at an unprecedented rate in Earth’s history. Latest research indicates the rate of change may be faster than at any time in the last 300 million years.As ocean acidity increases, its capacity to absorb CO2 from the atmosphere decreases. This decreases the ocean’s role in moderating climate change. Species-specific impacts of ocean acidification have been seen in laboratory and field studies on organisms from the poles to the tropics. Many organisms show adverse effects, such as reduced ability to form and maintain shells and skeletons, as well as reduced survival, growth, abundance and larval development. Conversely, evidence indicates that some organisms tolerate ocean acidification and that others, such as some seagrasses, may even thrive. Within decades, large parts of the polar oceans will become corrosive to the unprotected shells of calcareous marine organisms. Changes in carbonate chemistry of the tropical ocean may hamper or prevent coral reef growth within decades.The far-reaching effects of ocean acidification are predicted to impact food webs, biodiversity, aquaculture and hence societies. Species differ in their potential to adapt to new environments. Ocean chemistry may be changing too rapidly for many species or populations to adapt through evolution.Multiple stressors – ocean acidification, warming, decreases in oceanic oxygen concentrations (deoxygenation), increasing UV-B irradiance due to stratospheric ozone depletion, overfishing, pollution and eutrophication – and their interactions are creating significant challenges for ocean ecosystems. We do not fully understand the biogeochemical feedbacks to the climate system that may arise from ocean acidification. Predicting how whole ecosystems will change in response to rising CO2 levels remains challenging. While we know enough to expect changes in marine ecosystems and biodiversity within our lifetimes, we are unable ...
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