ALBERT

Description: 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.

Description: A large set of biogeochemical (nutrients, dissolved and particulate organic matter), phytoplanktonic (biomass and photosynthetic activity) and bacterial (bacterial diversity and ectoenzymatic activities) parameters were determined to understand how the severe drought period relative to the 2009–2010 El Niño Modoki episode influenced biogeochemical cycling and phyto- and bacterio-plankton communities in Terminos Lagoon (Mexico) potentially prefiguring future environmental conditions due to expected trends in climate change. During the study period, the water column of Terminos Lagoon functioned globally as a sink, and especially as a "nitrogen assimilator", because of high production of particulate and dissolved organic matter although exportation of autochthonous matter to the Gulf of Mexico was weak. Coupling between top-down and bottom-up controls accounted for the diverse responses in phytoplankton productivity. Nitrogen and phosphorus stoichiometry mostly accounted for the heterogeneity in phytoplankton and bacteria distribution in the lagoon. In the Eastern part, we found a clear decoupling between areas enriched in dissolved inorganic nitrogen in the North close to Puerto real coastal inlet and areas enriched in phosphate (PO4) in the South close to 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) close to the river mouth. In the Western part of the lagoon, maximal phytoplankton development resulted from the coupling between Palizada river inputs of nitrate (NO3) and particulate organic phosphorus -PP- (but depleted in PO4) and bacterial activity transforming PP and dissolved organic phosphorus (DOP) to available PO4. The Chumpan River only marginally contributed to PO4 inputs due to its very low contribution to overall river inputs. 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 polycyclic aromatic hydrocarbon (PAH)-degraders, which are of significance in this important oil production zone.