Patterns of microbial abundance and heterotrophic activity along nitrogen and salinity gradients in coastal wetlands

Funding for open access charge: Universidad de Granada/CBUA. This research was funded by the projects FLAMENCO (CGL2010-15812) and CRONOS (RTI2018-098849-B-I00) of the Spanish Ministry of Economy and Competitiveness and Ministry of Science and Innovation, the Modeling Nature Scientific Unit (UCE. PP2017.03), European Regional Development Fund (ERDF) and a PhD fellowship FPI (Formacion del Personal Investigador: BES2011-043658) to GLB.Coastal wetlands are valuable aquatic ecosystems with high biological productivity, which provide services such as a reduction in nitrogen loading into coastal waters and storage of organic carbon acting as carbon dioxide sinks. The predicted rise of sea level or freshwater extractions, particularly in the arid Mediterranean biome, will salinize many coastal wetlands. However, there is considerable uncertainty about how salinization will affect microbial communities and biogeochemical processes. We determined the abundance of total prokaryotes, cyanobacteria, and viruses and quantified the heterotrophic production of prokaryotes sensitive- (predominantly Bacteria) and resistant- (predominantly Archaea) to erythromycin in 112 ponds from nine coastal wetlands. We explored the main drivers of prokaryotic abundance and heterotrophic production using generalized linear models (GLMs). The best GLM, including all the wetlands, indicated that the concentration of total dissolved nitrogen (TDN) positively affected the total abundance of prokaryotes and the heterotrophic erythromycin-resistant (ery-R) production. In contrast, heterotrophic erythromycin-sensitive (ery-S) production was negatively related to TDN. This negative relationship appeared to be mediated by salinity and virus abundance. Heterotrophic ery-S production declined as salinity and virus abundance increased. Consequently, we observed a switch from heterotrophic ery-S production towards ery-R production as salinity and virus abundance increased. Our results imply that microbial activity will change from heterotrophic bacterial-dominated processes to archaeal-dominated processes with anthropogenic nitrogen and salinization increases. However, more studies are required to link the mineralization rates of dissolved nitrogen and organic carbon with specific archaeal taxa to enable more accurate predictions on future scenarios in coastal wetlands.Universidad de Granada/CBUASpanish Government CGL2010-15812 RTI2018-098849-B-I00Modeling Nature Scientific Unit UCE. PP2017.03European CommissionPhD fellowship FPI (Formacion del Personal Investigador) BES2011-04365

Microbial ecology in saline wetlands: nitrogen, flamingos and drought as drivers

En esta tesis nos hemos centrado en el estudio de la ecología microbiana en humedales salinos ubicados en la región Mediterránea incluyendo un amplio gradiente de salinidad desde aguas oligosalinas a hipersalinas. Hemos seleccionado nueve complejos de humedales costeros a lo largo de la cuenca Mediterránea desde las Marismas de Odiel en Huelva (España) por occidente hasta las salinas de Sfax (Túnez) por oriente, y la laguna de Fuente de Piedra, localizada al sur de España, como sistema endorreico. Estos humedales salinos se caracterizan por ser refugio, lugar de forrajeo y nidificación para numerosas aves acuáticas migratorias, en particular el flamenco (Rendón et al. 2001, Rendón-Martos et al. 2000, Green y Elmberg, 2014). Estos hallazgos tienen un interés debido a las predicciones de sequías severas, como consecuencias del cambio climático, que probablemente conducirán a una salinización generalizada de los humedales (Herbert et al. 2015) y posterior desecación (Wurtsbaugh et al. 2017; Wang et al. 2018). En general, hemos observado que la dinámica de los procariotas heterótrofos es completamente diferente en los humedales costeros y en un sistema endorreico como la laguna de Fuente de Piedra. La concentración de nitrógeno resulta clave en humedales costeros, mientras que la reducción del área de inundación resultan determinantes de la riqueza, diversidad y composición de las bacterias en períodos de sequía en la laguna de Fuente de Piedra con posibles efectos sobre sus servicios ecosistémicos.In this thesis, we have focused on the study of microbial ecology in saline wetlands located in the Mediterranean region including a wide gradient of salinity from oligosaline to hypersaline waters. We have selected nine coastal wetland complexes along the Mediterranean basin from the Odiel Marshes in Huelva (Spain) in the western side to the Sfax (Tunisia) in the eastern side, and the Fuente de Piedra lagoon, located in southern Spain, as an endorheic system. These saline wetlands are refuges, foraging sites and nesting sites for migratory waterbirds, in particular, the flamingo (Rendón et al. 2001, Rendón-Martos et al. 2000, Green and Elmberg, 2014). These findings are of interest due to predictions of severe droughts, as consequences of climate change, which are likely to lead to massive salinization of wetlands (Herbert et al. 2015) and, subsequent, desiccation (Wurtsbaugh et al. 2017; Wang et al. 2018). In general, we have observed that the dynamics of heterotrophic prokaryotes are completely different in coastal wetlands and in an endorheic system such as Fuente de Piedra Lagoon. Nitrogen concentration is key in coastal wetlands, whereas the reduction of the inundation area is a main driver of the richness, diversity and composition of bacteria in periods of drought in Fuente de Piedra lagoon with potential effects on its ecosystem services.Tesis Univ. Granada.La investigación realizada ha sido financiada por el Ministerio de Educación y Ciencia y de Economía y de Competitividad del Gobierno de España a través de los proyectos de investigación con referencia CGL2010-15812 y CGL2014-52362-R incluyendo fondos FEDER.Los recursos informáticos han sido facilitados por los proyectos CGL2013-47558-P y por los los proyectos CGL2017-86626-C2-2-P, incluyendo fondos FEDER

Particulate organic carbon sedimentation triggers lagged methane emissions in a eutrophic reservoir

Reservoirs act as carbon sinks when sedimentation of particulate organic carbon (POC) exceeds CO2 and CH4 emissions. Here, we study the poorly explored process where phytoplankton-derived acidic polysaccharides (APs) aggregate into particulate organic matter, promoting carbon export to sediments. This source of POC in sediments can mineralize to CO2 and CH4 over various timescales. Our research, centered on a Mediterranean reservoir, elucidates phenological trends of APs and POC sedimentation and identifies their predominant drivers. Our findings present synchronic sedimentation patterns of POC and APs but identify a 2-week delay between POC sedimentation and CH4 emissions. Despite its eutrophic status, our data demonstrate this reservoir's role as a carbon sink, sequestering 4.33 g C m−2 yr−1. This highlights the need to consider various time scales when quantifying carbon budgets in reservoirs.Project QUAL21-011 (Modeling Nature) of the Consejería de Universidad, Investigación e Innovación of the Junta de Andalucía, SpainProject COCOMAS (MTM2017-91054-EXP), CRONOS (RTI2018-098849-B-I00) of Spanish Ministry of Science, Innovation, and UniversitiesProject B.RNM.558.UGR20 of FEDER/Junta de AndalucíaProject QUAL21-011 (Modeling Nature) Consejería de Universidad, Investigación e Innovación of the Junta de AndalucíaFPU Ph.D. fellowships (FPU20/05804 and FPU 19/02161) from the Ministry of UniversitiesPAIDI postdoctoral fellows funded by Junta de Andalucí