Population dynamics of Siderastrea stellata Verrill, 1868 from Rocas Atoll, RN: implications for predicted climate change impacts at the only South Atlantic atoll

Abstract

Coral reefs are one of the most vulnerable ecosystems to ocean warming and acidification, and it is important to determine the role of reef building species in this environment in order to obtain insight into their susceptibility to expected impacts of global changes. Aspects of the life history of a coral population, such as reproduction, growth and size-frequency can contribute to the production of models that are used to estimate impacts and potential recovery of the population, acting as a powerful tool for the conservation and management of those ecosystems. Here, we present the first evidence of Siderastrea stellata planulation, its early growth, population size-frequency distribution and growth rate of adult colonies in Rocas Atoll. Our results, together with the environmental protection policies and the absence of anthropogenic pressures, suggest that S. stellata population may have a good potential in the maintenance and recovery in the atoll. However, our results also indicate an impact on corals' recruitment, probably as a consequence of the positive temperature anomaly that occurred in 2010. Thus, despite the pristine status of Rocas Atoll, the preservation of its coral community seems to be threatened by current global changes, such as more frequent thermal stress events.

Carbon stable isotope record in the coral species Siderastrea stellata: A link to the Suess Effect in the tropical South Atlantic Ocean

“…The growth rate for S. stellata for the Rocas Atoll was previously estimated by Pinheiro et al (2017) to be on average 6.8 ± 0.7 mm.year −1 using coralXDS software (Helmle et al 2002) similar to the extension rate that can be deduced from some carbon isotopic cycles in the coral records presented here. As discussed in section 4.1, the comparison between the number of δ 13 C cycles and U-series ages for colonies 13SS-1 and 13SS-2 (table 2) is compatible with die-off events in these colonies of Siderastrea, probably associated environmental stress like SST anomalies.…”

“…The weak signal revealed by the Fourier analysis at 2 to 4 mm is less than the annual extension porposed by Pinheiro et al (2017), but similar to values of linear extension rates (2.73 ± 0.35 mm.year −1 ) for the same species at the coast of Bahia, Brazil, reported by Lins-de- Barros and Pires (2006), and specimens from this genus (Siderastrea siderea) from the coast of Florida, U.S.A. (Maupin et al 2008;DeLong et al 2011). These smaller extension rates (and carbon isotope fluctuations) underline that the seasonal δ 13 C record in S. stellata from the Rocas Atoll is poorly defined and overprinted by larger multiannual variability (Fig.…”