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要旨:
The Anthropocene Working Group is leading a worldwide campaign to sample and analyze modern strata, including annual density bands of tropical massive coral skeletons. Corals are unique in the suite of proposed Anthropocene Global Boundary Stratotype Section and Point (GSSP) sites since they are living organisms that produce aragonite exoskeletons that can be preserved in the rock record and contain highly accurate and precise (< ±1 year) internal chronologies. The GSSP candidate site of West Flower Garden Bank (27°52.5'N, 93°49'W) is an open ocean location in the Gulf of Mexico with a submerged coral reef and few direct human impacts. Here we present results from a large Siderastrea siderea coral (core 05WFGB3; 1755-2005 CE) sampled with annual and monthly resolutions that show clear markers of global and regional human impacts. Atmospheric nuclear bomb testing by-products (14C, 239+240Pu) have clear increases in this coral in 1956 and 1964 coinciding with bomb testing dates. The annually-resolved coral δ13C averages -1.43‰ in the 1800s with a decreasing trend starting in the 1920s that accelerates from 2000-2005 to an average value of -3.14‰, consistent with the Suess Effect resulting from the burning fossil fuels. Coral skeletal δ15N starts to increase in 1957 (0.17 ±0.02‰ decade-1) corresponding with the increased use of agricultural fertilizers at the onset of the green revolution and nitrogen load in the Mississippi River. The coral Ba/Ca corresponds to changes in offshore oil operations starting in the 1940s and dripping in the 1980s when oil prices drop and production is reduced. Mercury concentrations in the coral skeleton tracks global Hg releases with an increase from 1933-1975 when industrial pollution Hg emissions increase and are reduced after the introduction of the pollution regulations. During this same time interval of increased anthropogenic pollution, the coral's growth declines by 15%. As the scientific community debates the GSSP site and year that marks the start of the Anthropocene, corals will continue to record of their last years, passively archiving the changes in their environment, chronicling its stressors, pollutants, and damage done to these otherwise multi-centenarians living organisms.
