Hetzinger, Steffen, Pfeiffer, Miriam, Dullo, Wolf-Christian , Zinke, J. and Garbe-Schönberg, Dieter (2016) A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events. Scientific Reports, 6 (32879). DOI 10.1038/srep32879.

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Abstract

Coral reefs are biologically diverse ecosystems threatened with effective collapse under rapid climate
change, in particular by recent increases in ocean temperatures. Coral bleaching has occurred during
major El Niño warming events, at times leading to the die-off of entire coral reefs. Here we present
records of stable isotopic composition, Sr/Ca ratios and extension rate (1940–2004) in coral aragonite
from a northern Venezuelan site, where reefs were strongly impacted by bleaching following the
1997–98 El Niño. We assess the impact of past warming events on coral extension rates and geochemical
proxies. A marked decrease in coral (Pseudodiploria strigosa) extension rates coincides with a baseline
shift to more negative values in oxygen and carbon isotopic composition after 1997–98, while a
neighboring coral (Siderastrea siderea) recovered to pre-bleaching extension rates simultaneously.
However, other stressors, besides high temperature, might also have influenced coral physiology and
geochemistry. Coastal Venezuelan reefs were exposed to a series of extreme environmental fluctuations
since the mid-1990s, i.e. upwelling, extreme rainfall and sediment input from landslides. This work
provides important new data on the potential impacts of multiple regional stress events on coral
isotopic compositions and raises questions about the long-term influence on coral-based paleoclimate
reconstructions.

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