Impacto de las acumulaciones de macroalgas en la comunidad biológica intermareal

Los efectos de la acumulación de macroalgas verdes en la comunidad biológica intermareal del caño Sancti Petri se siguieron a lo largo de un ciclo anual. La medida con microelectrodos selectivos de O2 y H2S permitió obtener perfiles detallados de la distribución vertical de estos parámetros. Los cambios en la microflora bentónica se estudiaron en la zona superficial del sedimento mediante microscopia óptica. Los cambios en la meiofauna se estudiaron tanto en la capa de macroalgas como en el interior del sedimento. La acumulación de macroalgas produce fenómenos de hipoxia/anoxia tanto en el sedimento como en el interior de la capa de macroalgas, que se acentúan en periodos de oscuridad, favoreciendo la acumulación de H2S en zonas cercanas a la superficie del sedimento. En estas condiciones se produce una reducción del 96.7% en la población de microalgas bentónicas y un cambio en la comunidad, pasando de estar dominada por diatomeas a estarlo por cianobacterias. La meiofauna incrementa su densidad de población en un 845 ± 535%. El grupo con mayor crecimiento fueron los nematodos, cuya población es 9 veces superior al control, pasando a dominar completamente la meiofauna con un 92 ± 1% del número total de individuos, lo que produce una gran reducción de la diversidad.Ministerio de Educacion y Ciencia, proyectos: REN2002-01281/MAR y CTM2006-04015Acciones Marie Curie: HPMF-CT-2000-0099

Decadal variability 2010-2021 of zooplankton community at the Guadalquivir estuary (southern Spain)

A Long Term Ecological Research Program has been monitoring the Guadalquivir estuary meso- and macro- zooplankton community monthly since January 2010. As an important nursery area for many marine species (fish and crustacean) from the Gulf of Cadiz, whose juveniles and recruits depend on zooplankton as main prey, understanding how abiotic and biotic factors determine zooplankton community structure it´s necessary to unreveal recruitment variability. We sampled throughout the whole salinity gradient, 2 locations, the two diurnal ebb and flood tides during the new moon days using a 100 μm zooplankton net. Zooplankton community is mainly composed by copepods and mysids. While the exotic Acartia tonsa calanoid copepod is the most abundant specie by abundance, mysid Mesopodopsis slabberi contribute the most to total biomass, followed by mysids Rhopalophthalmus tartessicus and Neomysis integer. Other abundant groups were copepods Acartia bifilosa and Acartia clausii, Calanipeda aquaedulcis, Paracalanus parvus and Acanthocyclops robustus, cladocera Pleopis polyphaemoides, together with veliger larvae, Cirripeda and Ostracoda, and Decapoda larvae. About total biodiversity, we found up to 183 species, estimating a total mean Species Richness of 9.7 (minimum 2- maximum 33) per sample, mean Shannon Diversity Index 3.27, Pielou Evenness 0.50 and mean betadiversity 0.630. While copepods area abundant form fall to early spring and summer, mysid density peaks form spring to fall. Community is structured by Salinity, but Temperature, Turbidity, Nitrate, Nitrite and Dissolved Oxygen were also important variables leading spatio-temporal variability, mainly when estuary recives high freshwater discharges from Alcala del Río dam

Population dynamic and trophic position of mysid community demonstrates its key role for nursery function in a temperate estuary

Guadalquivir Estuary is a main nursery ground of marine goal species for Gulf of Cadiz fisheries. It is a well-mixed temperate estuary with horizontal salinity gradient and clear seasonal water temperature trend. Mysid community with Mesopodopsis slabberi, Neomysis integer and Rhopalophthalmus tartessicus make up to over 80% of total macrofauna biomass in the estuary. Life history, population structure, secondary production, trophic level and community spatio-temporal dynamic were unravelled combining analysis of long term 16y monitoring data with 2y of in depth population analysis and trophic biomarker studies. Results show a key trophic role in food web, a seasonal trend showing density peaks ( 23, 3 and 6 mg/m3, respectively) in spring-summer and winter marine coastward migration. Despite being euryhaline, the three species of showed unevenly spatial distribution, being salinity the variable best explaining structure changes of mysid assemblage. Inter- and intra-specific euryhalinity differences both for prey and predators seem to determine the entire spatial estuarine community distribution. High secondary production (P/B rates 38.2, 10.3 and 10.7) and food web studies confirm key role of mysids transferring energy up to juveniles (fish and crustaceans) arriving yearly in spring to their nursery area

Monitoring turbidity in a highly variable estuary using Sentinel 2-A/B for ecosystem management applications

The Guadalquivir estuary (southern Spain) occasionally experiences medium to high turbidity, reaching above 700 Formazin Nephelometric Unit (FNU) during extreme events, thus negatively influencing its nursery function and the estuarine community structure. Although several turbidity algorithms are available to monitor water quality, they are mainly developed for mapping turbidity ranges of 0-100 FNU. Thus, their use in a highly turbid region may not give accurate results, which is crucial for estuarine ecosystem management. To fill this gap, we developed a multi-conditional turbidity algorithm that can retrieve turbidity from 0 to 600 FNU using the Sentinel-2 red and red-edge bands. Four major steps are implemented: atmospheric and sun glint correction of the Level-1C Sentinel-2 data, spectral analysis for different water turbidity levels, regression modelling between in situ turbidity and remote sensing reflectance (Rrs) for algorithm development, and validation of the best-suited model. When turbidity was < 85 FNU, the Rrs increased firstly in the red wavelength (665 nm), but it saturated beyond a certain turbidity threshold (> 250 FNU). At this time, Rrs started to increase in the red-edge wavelength (704 nm). Considering this spectral behavior, our algorithm is designed to automatically select the most sensitive turbidity vs. Rrs, thus avoiding the saturation effects of the red bands at high turbidity levels. The model showed good agreement between the satellite derived turbidity and the in situ measurements with a correlation coefficient of 0.97, RMSE of 15.93 FNU, and a bias of 13.34 FNU. Turbidity maps derived using this algorithm can be used for routine turbidity monitoring and assessment of potential anthropogenic actions (e.g., dredging activities), thus helping the decision-makers and relevant stakeholders to protect coastal resources and human health

Cleavage of dimethylsulfoniopropionate and reduction of acrylate by Desulfovibrio acrylicus sp. nov.

From anoxic intertidal sediment, a dimethylsulfoniopropionate (DMSP)-cleaving anaerobe (strain W218) was isolated that reduced the acrylate formed to propionate. The bacterium was vibrio- to rod-shaped and motile by means of multiple polar flagella. It reduced sulfate, thiosulfate, and acrylate, and used lactate, fumarate, succinate, malate, pyruvate, ethanol, propanol, glycerol, glycine, serine, alanine, cysteine, hydrogen, and formate as electron donors. Sulfate and acrylate were reduced simultaneously; growth with sulfate was faster than with acrylate. Extracts of cells grown in the presence of DMSP contained high DMSP lyase activities (9.8 U/mg protein). The DNA mol% G+C was 45.1. On the basis of its characteristics and the 16S rRNA gene sequence, strain W218 was assigned to a new Desulfovibrio species for which the name Desulfovibrio acrylicus is proposed. A variety of other sulfate-reducing bacteria (eight of them originating from a marine or saline environment and five from other environments) did not reduce acrylate.