BIOLOGICAL PROXIES IN THE POSIDONIA OCEANICA (L. DELILE) SEDIMENTARY RECORD PROVIDE INFORMATION ON ECOSYSTEM PALEO-PRODUCTIVITY. (E)
Posidonia oceanica is a large long-living species that buries a significant part of the belowground production in the sediments, forming an organic bioconstruction known as mat. These mats have been proven to be a realible paleo-archive to study environmental changes at a pluri-millenary scale. Palaeoecological studies using seagrass archives are still scarce in general, and in particular those using biological proxies. The aim of this work is to evaluate the potential of some biological proxies, like the carbon and nitrogen stable isotopic composition of plant sheaths and the proportions of seagrass debris from different plant organs, along with other sedimentological proxies. The study was conducted in a 4 kyr mat core sampled in the NW coast of Spain. In the overall, the paleo-series obtained are suggestive of a period of a considerable stability from 4000 yr BP until ~1500-2000 cal. yr BP, when variability increased probably as a consequence of the onset of significant human impacts in the aquatic and adjacent terrestrial ecosystems. Changes in anthropic eutrophication and ecosystem production were evidenced by the proxies studied and were related to the effect and variability of global (solar irradiation) and local factors (human impact and water temperature). Our results suggest that, after a maximum around 1700 BP, the productivity of the system has initiated a steady decline reaching nowadays unprecedented low values. Although paleo-reconstructions have to be taken with caution, the trend observed should serve to encourage environmental managers to take measures to prevent the ecosystem from trespassing the threshold of its resilience, if still in time.
Leiva, C., Centro de Estudios Avanzados de Blanes (CSIC), Spain, email@example.com
Mateo, M. A., Centro de Estudios Avanzados de Blanes (CSIC), Spain, firstname.lastname@example.org
Serrano, O., Edith Cowan University, Spain, email@example.com
Martinez, A., Universidad de Santiago de Compostela, Spain, firstname.lastname@example.org
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