I. Mazarrasa, N. Marbà, J. Garcia-Orellana, Pere Masque, A. Arias-Ortiz, C.M. Duarte
Limnology and Oceanography, (2017)
Seagrass meadows are strong coastal carbon sinks of autochthonous and
allochthonous carbon. The aim of this study was to assess the effect of
coastal anthropogenic pressure on the variability of carbon sources in
seagrass carbon sinks during the last 150 yr. We did so by examining the
composition of the sediment organic carbon (Corg) stocks by measuring the δ13Corg signature and C : N ratio in 210Pb dated sediments of 11 Posidonia oceanica
seagrass meadows around the Balearic Islands (Spain, Western
Mediterranean) under different levels of human pressure. On average, the
top meter sediment carbon deposits were mainly (59% ± 12%) composed by P. oceanica derived carbon whereas seston contribution was generally lower (41% ± 8%). The contribution of P. oceanica
to the total sediment carbon stock was the highest (∼ 80%) in the most
pristine sites whereas the sestonic contribution was the highest (∼
40–80%) in the meadows located in areas under moderate to very high
human pressure. Furthermore, an increase in the contribution of sestonic
carbon and a decrease in that of seagrass derived carbon toward present
was observed in most of the meadows examined, coincident with the onset
of the tourism industry development and coastal urbanization in the
region. Our results demonstrate a general increase of total carbon
accumulation rate in P. oceanica sediments during the last century, mainly driven by the increase in sestonic Corg
carbon burial, which may have important implications in the long-term
carbon sink capacity of the seagrass meadows in the region examined.