Ocean Acidification Compromises Coral Recruitment

A recent study demonstrated that ocean acidification affects three sequential life history phases necessary for successful coral recruitment of Acropora palmata: 1) larval availability (by limiting fertilization), 2) settlement ecology (by reducing settlement success), and 3) postsettlement ecology (by impeding postsettlement growth). The results of this study show that ocean acidification has the potential to affect multiple life history stages of corals, including critical processes independent of calcification. The compounding nature of these impacts on successive life history stages suggests that the consequences of ocean acidification on coral populations and reef communities may be more severe than previously thought.3

Changes in ocean chemistry can have extensive direct and indirect effects on organisms and the habitats in which they live. Studies of marine calcifiers indicate that most, but not all, exhibit reduced calcification with increased ocean acidification1.

A growing number of studies have demonstrated adverse impacts on marine organisms as a result of ocean acidification, including the following:

The rate at which reef-building corals produce their skeletons decreases.
The ability of free-swimming zooplankton to maintain protective shells is reduced.
The rate at which marine macroalgae (crustose coralline and green algae Halimeda) produce calcium carbonate is reduced.
The survival of larval marine species, including commercial fish and shellfish, is reduced.
The developmental stages of invertebrates (fertilization, egg cleavage, larva, settlement and reproduction) are impaired.2

Representative examples of impacts of ocean acidification on major groups of marine biota derived from experimental manipulation studies. The response curves on the right indicate four cases:(a) linear negative, (b) linear positive, (c) level, and (d) non-linear parabolic responses to increasing levels of seawater pCO2 for each of the groups. Note that in some cases strains of the same species exhibited different behavior in different experiments (see Footnotes 1, 4).

Declining pH may affect organisms in ways that extend beyond declining calcification or metabolic performance including:

interactions between species during different life stages
shifting competitive pressures
alterations in predation, which will come into play as communities respond to acidification
alteration of fish larvae behavior and reduced recruitment success5

Furthermore, synergistic effects of other stressors, such as nutrient input, increased sea surface temperature and sea level rise will each play a role in determining alterations of marine communities in high CO2 conditions.

Acidification Impacts

Ocean Acidification Compromises Coral Recruitment

Resources