Ocean Acidification A National Strategy to Meet the Challenges of a Changing Ocean (2010) / Chapter Skim
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3 Effects of Ocean Acidification on the Physiology ofMarine Organisms
3 Effects of Ocean Acidification on the Physiology ofMarine Organisms
Pages 45-58
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From page 45... ...
It focuses on processes that are likely to be affected by acidification, both those that are common to many organisms (i.e., calcification and pH control) and those that affect primary produc tion, which provides the principal influx of organic material and energy to marine ecosystems (i.e., photosynthetic carbon fixation, nutrient uptake, and nitrogen fixation)
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From page 46... ...
Important exam ples include photosynthetic primary producers (e.g., coccolithophores and coralline algae) , zooplankton (e.g., pteropods)
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From page 47... ...
addressed multiple hypotheses to explain why acidification causes a decrease in coral calcification rates and suggested that decreases in intracellular or extracellular pH, or shifts in the buffering capacity of the calcifying fluid were likely. A recent study on a temperate coral provides evidence that the calcification response reflects changes in the proton pumping capacity, which is necessary to maintain the high saturation states of the internal calcifying fluid (Cohen et al., 2009)
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From page 48... ...
. As ocean acidification decreases the CO32 concentration, it decreases the degree of supersaturation of CaCO3 in the upper water column, brings the saturation horizons closer to the surface, and may result in some organ isms being exposed to undersaturated (corrosive)
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From page 49... ...
10 -1 C -1 8 Emiliana huxleyi Gephyrocapsa oceanica 6 -13 Calcification Rate (10 4 2 0 0 500 1000 1500 2000 2500 3000 pCO (ppmv) 2 Figure 3-1
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From page 50... ...
Dissolved CO2 in internal fluids tends to form bicarbonate and free hydrogen ions, acidifying the medium as it does in seawater. Most heterotrophic organisms excrete CO2, produced as a byproduct of metabolic activity, by utilizing a concentration gradient from high internal to the lower, external dissolved CO2.
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From page 51... ...
. Animals that actively regulate internal pH will have a greater metabolic demand to meet the high energetic cost of pumping ions across membranes, but the decreased affinity of the respiratory proteins will make it more difficult for the organism to meet that metabolic demand due to the reduction in overall aerobic respiration (Pörtner et al., 2000)
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From page 52... ...
Thus CO2, which is at low concentration in the ambient water, must be concentrated at the site of fixation; this is a difficult and energyconsuming process because the CO2 molecule diffuses readily through biological membranes and continuously leaks out of cells. It is thus expected that an increase in the CO2 concentration of surface seawater would facilitate marine photosynthesis and lead in some cases to an increase in primary production (i.e., the rate of organic matter synthesis per unit time and unit area of the ocean)
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From page 53... ...
These projections are based on limited data in the marine environment, but they are supported by the analogy with land plants, which possess similar underlying photosynthetic mechanisms. A large number of observations on terrestrial plants exposed to high CO2 show a boost in photosynthesis and a differential response among species.
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From page 54... ...
This is particularly true for trace metals such as zinc, cobalt, nickel, or iron, which are essential for various biochemical processes inside cells. These metals are readily taken up when present as free ions or ions bound to chloride, hydroxide, or other inor ganic species, but require specialized uptake machinery when bound in organic complexes (Morel et al., 2003)
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From page 55... ...
(Xu et al., 2006) Figure 3-3 R01733 Primary production -- the amount of organic matter that is synthe uneditable bitmapped image sized per area of surface seawater per unit time -- generally depends on the rate of supply of the limiting nutrient.
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From page 56... ...
Nitrogen fixation represents a major input of "new" nitrogen to marine ecosystems and is thus a key in controlling primary production in large regions of the world's oceans. Nitrogen fixation is an "expensive" biochemical process that requires synthesis of a complex, ironrich enzyme and uses large amounts of energy.
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From page 57... ...
. The persistence of various taxa under increasing ocean acidification will depend on either the capacity for acclimation (plasticity in phenotype within a generation)
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