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

Abstract

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 (PO 4 ) 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 PO 4 and the coupling between Palizada River inputs of nitrate (NO 3 ) and PP. The Chumpan River contributed only marginally to PO 4 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

Dissolved inorganic nitrogen and particulate organic nitrogen budget in the Yucatán shelf: driving mechanisms through a physical–biogeochemical coupled model

“…Monthly climatological values were calculated for the Mexican rivers and SGD systems, using temporally scattered information found in the literature (e.g. Rojas-Galaviz et al, 1992;Milliman and Syvitski, 1992;Poot-Delgado et al, 2015;Conan et al, 2016) and a data collection effort within Mexican institutions led by Jorge Zavala-Hidalgo (personal communication, January 2015) and from the GOMEX IV cruise of CINVESTAV (Centro de Investigación y Estudios Avanzados in Merida Yucatan) within the CIGoM project. During this cruise, a total of 71 profiles of NO 3 , potential temperature, salinity, and chlorophyll were collected at standard depths from 2 to 20 November 2015.…”

“…In order to obtain southern freshwater inputs, a time series is built based on the composite of temperature, salinity, volume transport and nutrient concentration at the location of the freshwater sources or near it. The information is obtained from values reported in the literature (Milliman and Syvitski, 1992;Herrera-Silveira et al, 2002Yáñez Arancibia and Day, 2004;Hudson et al, 2005;Herrera-Silveira and Morales-Ojeda, 2010;Poot-Delgado et al, 2015;Kemp et al, 2016;Conan et al, 2016) and from observational hydrographic stations near the Yucatán coast (Sect. 2.3).…”

Geoacumulation of Heavy Metals in Sediment of the Fluvial–Lagoon–Deltaic System of the Palizada River, Campeche, Mexico

“…The sediments can accumulate heavy metals that reach aquatic environments, in which changes in physicochemical conditions can be remobilized; in doing so, releasing these elements in the water column, these contributions can be transferred through the food chain [2,36]. The Palizada system interacts with surrounding aquatic bodies, presenting dynamics of material distribution to the Términos Lagoon, in which the water column, in its totality, acts as a sink for nutrients due to a high production of particles, dissolved organic matter, and a reduced export of material to the Gulf of Mexico [44]. As a consequence, in the Términos lagoon, a spatial and temporary heterogeneity of water-sediment flows predominates, with peaks in the mineralization rates during the rainy season, relating significantly to the content of organic matters in sediments [45].…”

Budget of the total nitrogen in the Yucatan Shelf: driving mechanisms through a physical-biogeochemical coupled model

“…For the US rivers the daily data were obtained from the U.S. Geological Survey (USGS) (https://www.usgs.gov/) and the Gulf of Mexico Coastal Ocean Observing System (GCOOS) (https://products.gcoos.org/). Monthly climatological values were calculated for the Mexican rivers, using temporally scattered information found in the literature (Rojas-Galaviz et al, 1992;Milliman and Syvitski, 1992;Poot-Delgado et al, 2015;Conan et al, 2016) and a data collection effort within Mexican institutions by Dr. Jorge Zavala-Hidalgo (personal communication). Therefore the US rivers present inter-annual variability but it is absent in the Mexican rivers.…”

“…For instance,Conan et al (2016) suggest that El Niño Modoki 2009-2010 event influenced the biogeochemical cycling of phyto and bacterio-plankton communities in Términos Lagoon (South of GoM, in the Campeche shelf). They found that in this period the export of organic matter to the GoM was weak, making the Lagoon function as an nitrogen sink.…”