Phytoplankton composition in shallow water ecosystems: influence of environmental gradients and nutrient availability

Environmental gradients caused by hydrological changes, whether natural or maninduced, affect the planktonic taxonomic and functional composition in shallow water ecosystems. In this sense, our aim was to find out the main variables or variable ratios that are the driving forces of the major phytoplankton taxonomic groups in Mediterranean coastal lagoons. For this purpose, 11 waterbodies were choosen, 6 of them in Empordà wetlands and 5 in the Doñana National Park, looking for representative conditions along a gradient of salinity and nutrient content. Two surveys were conducted in each waterbody (January and May 2007), after that the phytoplankton composition (chemotaxonomic composition) and also several physical and chemical environmental variables were analyzed. Two methodological approaches were used and compared: a first approach with a log (x+1) variable transformation and a second one where variables were transformed using the compositional data analysis (CoDa) techniques introduced by Aitchison (1986). When the raw data approach and the CoDa approach analysis (RDA) were compared, the results obtained were similar with regard to explained variance and also interpretation. The CoDa approach was characterized by the introduction of a new environmental driving factor, the bacterial biomass, whose ratio with the peptidase enzyme activity became significant. In this sense, the CoDa approach contributed to improving the biological interpretation of the phytoplankton distribution based on the raw analysis

Dataset for analyzing and modelling the eutrophication processes in groundwater-coastal lagoon systems: The La Pletera lagoons case study (NE Spain)

A comprehensive hydrogeological report was conducted to determine the origin, occurrence and processes affecting nitrogen in a Mediterranean coastal aquifer-lagoon system. Water levels, hydrochemical and isotopic data was gathered during a 4-year period in the La Pletera salt marsh area (NE Spain). They were collected from the alluvial aquifer, two natural lagoons and four other permanent lagoons excavated during a restoration process (in 2002 and 2016), two watercourses (the Ter River and the Ter Vell artificial channel), 21 wells (considering six of them for groundwater sampling) and the Mediterranean Sea. Potentiometric surveys were carried out seasonally, however twelve-monthly campaigns (from November 2014 to October 2015), and nine seasonal campaigns (from January 2016 to January 2018) were conducted for hydrochemical and environmental isotopes analyses. The evolution of the water table was analysed for each well, and potentiometric maps were plotted to determine the relationship between the aquifer and the lagoons, sea, watercourses, and groundwater flow. Hydrochemical data included physicochemical data measured in situ (temperature, pH, Eh, dissolved oxygen, and electrical conductivity), major and minor ions (HCO3−, CO32−, Cl−, SO42−, F−, Br−, Ca2+, Mg2+, Na+, and K+), and nutrients (NO2−, NO3−, NH4+, Total Nitrogen (TN), PO43−, and Total Phosphorus (TP)). Environmental isotopes included stable water isotopes (δ18O and δD), nitrate (δ15NNO3 and δ18ONO3) and sulphate isotopes (δ34SSO4 and δ18OSO4). Water isotopes were analysed for all campaigns, however, nitrate and sulphate isotopes water samples were only analysed in some particular surveys (November and December 2014; January, April, June, July and August 2015). Additionally, two more surveys for sulphate isotopes were conducted in April and October of 2016. The data generated through this research may be used as a starting point to analyse the evolution of these recently restored lagoons, and their future responses to global change. In addition, this dataset may be used to model the hydrological and hydrochemical behaviour of the aquifer