Biogeochemical cycling and phyto- and bacterioplankton communities in a large and shallow tropical lagoon Términos Lagoon, Mexico under 2009–2010 El Niño Modoki drought conditionsReport as inadecuate

Biogeochemical cycling and phyto- and bacterioplankton communities in a large and shallow tropical lagoon Términos Lagoon, Mexico under 2009–2010 El Niño Modoki drought conditions - Download this document for free, or read online. Document in PDF available to download.

1 LOMIC - Laboratoire d-Océanographie Microbienne 2 UAM - Universidad Autónoma Metropolitana Mexico 3 MIO - Institut méditerranéen d-océanologie

Abstract : The 2009–2010 period was marked by an episode of intense drought known as the El Niño Modoki event. Sampling of the Términos Lagoon Mexico was carried out in November 2009 in order to understand the influence of these particular environmental conditions on organic matter fluxes within the lagoon-s pelagic ecosystem and, more specifically, on the relationship between phyto- and bacterioplankton communities. The measurements presented here concern biogeochemical parameters nutrients, dissolved and particulate organic matter POM, and dissolved polycyclic aromatic hydrocarbons PAHs, phytoplankton biomass and photosynthesis, and bacteria diversity and abundance, including PAH degradation bacteria and ectoenzymatic activities. During the studied period, the water column of the Términos Lagoon functioned globally as a sink and, more precisely, as a -nitrogen assimilator-. This was due to the high production of particulate and dissolved organic matter DOM, even though exportation of autochthonous matter to the Gulf of Mexico was weak. We found that -bottom-up- control accounted for a large portion of the variability of phytoplankton productivity. Nitrogen and phosphorus stoichiometry mostly accounted for the heterogeneity in phytoplankton and free-living prokaryote distribution in the lagoon. In the eastern part, we found a clear decoupling between areas enriched in dissolved inorganic nitrogen near the Puerto Real coastal inlet and areas enriched in phosphate PO4 near the Candelaria estuary. Such a decoupling limited the potential for primary production, resulting in an accumulation of dissolved organic carbon and nitrogen DOC and DON, respectively near the river mouths. In the western part of the lagoon, maximal phytoplankton development resulted from bacterial activity transforming particulate organic phosphorus PP and dissolved organic phosphorus DOP to available PO4 and the coupling between Palizada River inputs of nitrate NO3 and PP. The Chumpan River contributed only marginally to PO4 inputs due to its very low contribution to overall river inputs. The highest dissolved total PAH concentrations were measured in the El Carmen Inlet, suggesting that the anthropogenic pollution of the zone is probably related to the oil-platform exploitation activities in the shallow waters of the southern of the Gulf of Mexico. We also found that a complex array of biogeochemical and phytoplanktonic parameters were the driving force behind the geographical distribution of bacterial community structure and activities. Finally, we showed that nutrients brought by the Palizada River supported an abundant bacterial community of PAH degraders, which are of significance in this important oil-production zone.

Author: Pascal Conan - Mireille Pujo-Pay - Marina Agab - Laura Calva-Benítez - Sandrine Chifflet - Pascal Douillet - Claire Dussud - Ren



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