Background
The authors write that "coral assemblages on many reefs of the western Atlantic-Caribbean region have been highly volatile in recent decades," while "by contrast," they say the benthic communities at the Flower Garden Banks (FGB) - two shelf-margin reefs some 175 km off the coast of Texas in the western Gulf of Mexico - "have been remarkably stable during this time (Aronson et al., 2005)." However, they also note that the recent decadal-scale stability at the FGB site "belies centennial- to millennial-scale dynamics that are critical to understanding the history of these reefs and their future in a warming ocean."

What was done
Very briefly, Precht et al. "report the discovery of fossil acroporid corals at the FGB and use their ages and stratigraphic positions to reconstruct the ecological history of the Banks."

What was learned
First of all, the six scientists report the discovery of fossil elkhorn corals (Acropora palmata) at the FGB site that corresponded in time to what they say was "an interval of warmer-than-present sea-surface temperatures (SSTs) during the Holocene thermal maximum (HTM)." In addition, they note that another acroporid (A. cervicornis) "dominated the flanks of the FGB during the late Holocene, through the Medieval Warm Period, until they were killed by the coldest conditions of the Little Ice Age (Glynn et al., 1983)."

Continuing, Precht et al. opine that "the recent return of A. palmata colonies to the reef caps may be a bellwether of climate change," citing Precht and Aronson (2004) and noting that "over the past few decades, hundreds of species have responded to recent warming trends by expanding their ranges to higher latitudes, as well as by changing their phenologies (Walther et al., 2002; Parmesan and Yohe, 2003; Root et al., 2003; Berge et al., 2005; Figueria and Booth, 2010; Fodrie et al., 2010; Hoegh-Guldberg and Bruno, 2010)." And they say "the most parsimonious explanation for the return of A. palmata to the FGB is a decadal-scale increase in sea temperature (Levitus et al., 2000; Barnett et al., 2001; Hansen et al., 2006; Seidel et al., 2008), or a reduction in the frequency of extreme cold events (Cavanaugh et al., 2013)," while noting that similar range expansions of acroporids have been observed along the east coast of Florida (Precht and Aronson, 2004; ARBT, 2005), in Australia (Marsh, 1992; Veron, 1995; Baird et al., 2012), and in Japan (Yamano et al., 2011)."

What it means
In light of these several observations, Precht et al. conclude that "if the newly arrived acroporids persist and expand, we may well witness a new stage of reef development that is in reality a return to the conditions of times past," all of which suggests that earth's corals are well equipped to deal with significant shifts in planetary temperatures, as they have successfully done so many times before.

References
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