Ocean acidification

Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2°C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef 2008 begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided. 

Given the amount of CO2 currently being absorbed by the ocean, there is a great deal of research studying the effects of ocean acidification on a variety of species. Considering the relationship between pH and levels of calcium present in the ocean water, the healing process of Ventricaria ventricosa is hypothesized to be negatively affected by the decreased pH that is projected for the ocean. V. ventricosa is a green alga (Chlorophyta) and one of the largest unicellular organisms. When punctured, V. ventricosa forms an aggregation ring around the wound which contracts in order to heal the membrane. This research measured the healing rate of V. ventricosa in present day ocean water (pH=8.05) as well as acidified ocean water (pH less than 7.0). Individuals of V. ventricosa in present pH water conditions were able to heal the puncture wound within 120 minutes, while the individuals in acidified ocean water were not able to heal themselves within the same time frame. It is unknown whether the V. ventricosa would eventually heal themselves over a longer period of time or given a greater volume of ocean water; however it is apparent that the decreased levels of calcium in the acidified water had a negative effect on the healing process of V. ventricosa. Ocean acidification is likely to affect the basic biological functioning of a variety of marine life, which will face severe difficulties adapting to the acidified ocean water.

This student research was retrieved from Physis: Journal of Marine Science XIII (Spring 2013)19: 33-38 from CIEE Bonaire.

Carbon dioxide levels in the ocean are predicted to double by the end of the century, making the marine environment more acidic than it is today. This study aimed to analyze whether increasing acidity affects antipredator survival behavior of the bridled goby, Coryphopterus glaucofraenum. A group of 10 adult gobies were treated with elevated CO2 levels, simulating predicted conditions by the year 2100, and another group of 10 were treated in present-day levels. Each group was exposed to the chemical cue of an injured conspecific, a predation chemical alarm signal, and the behavioral responses of each individual were recorded. The two groups were compared according to average time spent under shelter, number of feeding attempts, and amount of time spent motionless after exposure to cue. Overall, this experiment supported the hypothesis that gobies treated in acidified water would fail to fully exhibit such predator avoidance behaviors; gobies treated in elevated CO2 levels spent less time motionless after exposure to predation chemical cue. This study attempts to make important observations about the effect of environmental factors on fish behavior as well as far-reaching implications for the future survival of fish species and the stability of marine ecosystems as a whole.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 30-35 from CIEE Bonaire.

Abstract Ocean acidification studies in the past decade have greatly improved our knowledge of how calcifying organisms respond to increased surface ocean CO2 levels. It has become evident that, for many organisms, nutri- ent availability is an important factor that influences their physiological responses and competitive interactions with other species. Therefore, we tested how simulated ocean acidification and eutrophication (nitrate and phosphate enrichment) interact to affect the physiology and ecology of a calcifying chlorophyte macroalga (Halimeda opuntia(L.) J.V. Lamouroux) and its common noncalcifying epi- phyte (Dictyota sp.) in a 4-week fully crossed multifacto- rial experiment. Inorganic nutrient enrichment (+NP) had a strong influence on all responses measured with the excep- tion of net calcification. Elevated CO2 alone significantly decreased electron transport rates of the photosynthetic apparatus and resulted in phosphorus limitation in both spe- cies, but had no effect on oxygen production or respiration. The combination of CO2 and +NP significantly increased electron transport rates in both species. While +NP alone stimulated H. opuntia growth rates, Dictyota growth was significantly stimulated by nutrient enrichment only at elevated CO2, which led to the highest biomass ratios of Dictyota to Halimeda. Our results suggest that inorganic nutrient enrichment alone stimulates several aspects of H. opuntia physiology, but nutrient enrichment at a CO2 con- centration predicted for the end of the century benefits Dic- tyota sp. and hinders its calcifying basibiont H. opuntia.