How does rising atmospheric CO2 affect marine organisms?

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Responses of Emergent Intertidal Coral Reefs to a Strong El-Niño
Kelmo, F., Bell, J.J., Moraes, S.S., Gomes, R.C.T., Mariano-Neto, E. and Attrill, M.J. 2014. Differential responses of emergent intertidal coral reef fauna to a large-scale El-Niño Southern Oscillation Event: Sponge and coral resilience. PLOS ONE 9: e93209.

Given the environmental variability that intertidal reefs experience, the authors speculate that "such reefs may potentially be more resilient to climatic events and provide important insights into the adaptation of reef fauna to future ocean warming." Yet they say there is a paucity of information on the impacts of the 1997-98 El Niño event and subsequent climatic episodes on such corals. And it was this dearth of data that moved them to conduct just such a study.

What was done
To "provide a contrast to patterns observed in subtidal reef systems," Kelmo et al. conducted a 17-year (1995 to 2011) study of four emergent intertidal reefs (Praia do Forte, Itacimirim, Guarajuba and Abai) of Northern Bahia, Brazil, in which they analyzed the impacts of the 1997-98 ENSO (El Niño Southern Oscillation) on the intertidal reefs' fauna and their subsequent responses.

What was learned
The six scientists - hailing from Brazil, New Zealand and the United Kingdom - report that (1) "the densities of two species of coral, Favia gravida and Siderastrea stellata, did not vary significantly across the study period," that (2) "echinoderms were reduced to a single species in 1999," but that (3) "diversity levels had recovered by 2002," that (4) "sponge assemblages were not impacted by the 1997-98 event," but that (5) "their densities had increased by the study end," and that (6) "molluscs, bryozoans and ascidians suffered severe declines in diversity and abundance and had not recovered to pre-El Niño levels by the end of the study." Last of all, however, they report that (7) "a stable invertebrate community had re-established on the reefs after the El Niño event," but they determined that (8) "it has a different overall composition to the pre-El Niño community."

What it means
In the concluding sentence of their paper, Kelmo et al. write that "the corals and sponges in these environments appeared relatively un-impacted by the ENSO event, and therefore represent future models for understanding the potential resilience of marine organisms to climate change." But their other findings suggest that although coral reef communities could likely survive predicted changes in climate, those new communities may look somewhat different than they do today in terms of their species composition, which is, nevertheless, a very welcome finding compared to the many "doom and gloom" prognostications of the world's climate alarmists.

Reviewed 25 June 2014