TY - JOUR
T1 - Stratigraphic unmixing reveals repeated hypoxia events over the past 500 yr in the northern Adriatic Sea
AU - Tomašovỳch, Adam
AU - Gallmetzer, Ivo
AU - Haselmair, Alexandra
AU - Kaufman, Darrell S.
AU - Vidović, Jelena
AU - Zuschin, Martin
N1 - Publisher Copyright:
© 2017 The Authors.
PY - 2017
Y1 - 2017
N2 - In the northern Adriatic Sea and in most semienclosed coastal regions worldwide, hypoxia induced by eutrophication in the late 20th century caused major die-offs of coastal marine organisms. However, ecosystem responses to hypoxia over longer centennial scales are unclear because the duration of direct observations is limited to a few decades and/or the temporal resolution of sedimentary archives is compromised by slow sedimentation and bioturbation. To assess whether perturbations of ecosystems by hypoxia recurred over centuries in the northern Adriatic Sea, we evaluate the timing and forcing of past hypoxia events based on the production history of the opportunistic, hypoxia-tolerant bivalve Corbula gibba, using 210Pb data, radiocarbon dating, amino acid racemization, and distribution of foraminifers in sediment cores that capture the past 500 yr in the Gulf of Trieste. Unmixing the stratigraphic record on the basis of 311 shells of C. gibba, we show that the reconstructed fluctuations in abundance do not correlate with abundances in the raw stratigraphic record. We find that production of C. gibba has undergone major decadal-scale fluctuations since the 18th century, with outbreaks corresponding to density of more than 1000 individuals per square meter. These outbreaks represent long-term phenomena in the northern Adriatic ecosystem rather than novel states characteristic of the 20th century eutrophication. They positively correlate with centennial-scale fluctuations in sea-surface temperature, indicating that the hypoxia events were coupled with water-column stratification rather than with nutrient enrichment.
AB - In the northern Adriatic Sea and in most semienclosed coastal regions worldwide, hypoxia induced by eutrophication in the late 20th century caused major die-offs of coastal marine organisms. However, ecosystem responses to hypoxia over longer centennial scales are unclear because the duration of direct observations is limited to a few decades and/or the temporal resolution of sedimentary archives is compromised by slow sedimentation and bioturbation. To assess whether perturbations of ecosystems by hypoxia recurred over centuries in the northern Adriatic Sea, we evaluate the timing and forcing of past hypoxia events based on the production history of the opportunistic, hypoxia-tolerant bivalve Corbula gibba, using 210Pb data, radiocarbon dating, amino acid racemization, and distribution of foraminifers in sediment cores that capture the past 500 yr in the Gulf of Trieste. Unmixing the stratigraphic record on the basis of 311 shells of C. gibba, we show that the reconstructed fluctuations in abundance do not correlate with abundances in the raw stratigraphic record. We find that production of C. gibba has undergone major decadal-scale fluctuations since the 18th century, with outbreaks corresponding to density of more than 1000 individuals per square meter. These outbreaks represent long-term phenomena in the northern Adriatic ecosystem rather than novel states characteristic of the 20th century eutrophication. They positively correlate with centennial-scale fluctuations in sea-surface temperature, indicating that the hypoxia events were coupled with water-column stratification rather than with nutrient enrichment.
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U2 - 10.1130/G38676.1
DO - 10.1130/G38676.1
M3 - Article
AN - SCOPUS:85015147289
SN - 0091-7613
VL - 45
SP - 363
EP - 366
JO - Geology
JF - Geology
IS - 4
ER -