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11 pages, 6 figures, 2 tables, supplementary material https://doi.org/10.1016/j.pocean.2019.05.008, The link between phytoplankton primary production (PPP) and chromophoric dissolved organic matter (CDOM) has been demonstrated indirectly in the laboratory, but not directly in the sea. Here, for the first time, we report a strong link between PPP and CDOM in a study carried out in coastal marine waters around Barcelona (NW Mediterranean) in contrasting seasons. We measured relevant correlations between a CDOM concentration and both PPP (r = 0.89, p < 0.001, n = 16; r = 0.76, p < 0.01, n = 10; and r = 0.68, p < 0.001, n = 26; for summer, winter–spring and both seasons together, respectively) and the specific production rate at optimal light intensity (P ; r = 0.77, p < 0.001, n = 16; r = 0.86, p < 0.01, n = 10; and r = 0.85, p < 0.001, n = 26; for the same seasons). Based on our findings, we design a model that predicts PPP very well, using a CDOM, water temperature and photosynthetically active radiation (PAR)(R = 0.84, p < 0.001, n = 26). Relationships between CDOM concentration parameters (measured at wavelengths of 280, 300, 340, 355, 375, 412 and 460 nm) and variables associated to CDOM processes (chlorophyll-a, bacterial abundance, turbidity related to sediment resuspension and PAR) were also evaluated. Bacterial abundance is significantly correlated with CDOM concentration measured at higher wavelengths when all samples are considered (e.g., r = 0.82, p < 0.001, n = 26, for a CDOM). However, in seasonal data analysis, the correlations decrease slightly (summer season: e.g., r = 0.79, p < 0.001, n = 16, for a CDOM) or become non-significant (winter–spring season: e.g., r = -0.02, p = 0.95, n = 10, for a CDOM). Sunlight photobleaching and sediment resuspension processes significantly influence CDOM dynamics in the summer (for a CDOM: r = -0.72, p < 0.001, n = 16; and r = 0.67, p < 0.01, n = 16, respectively), This work was supported by the Catalan Water Agency (Departament de Medi Ambient i Habitatge, Generalitat de Catalunya) through its Monitoring and Control Program (PSIC) of Catalan coastal waters

14 pages, 10 figures, 7 tables, supplementary data http://dx.doi.org/10.1016/j.ecolmodel.2016.07.009, The dinoflagellate Karlodinium and the diatom Pseudo-nitzschia are bloom-forming genera frequently present in Alfacs Bay. Both microalgae are associated with toxic events. Therefore, understanding their population dynamics and predict their occurrence in short-term is crucial for an optimal management of toxic events for the local shellfish production and ecosystem managers. Artificial neural networks have been successfully used to model the complex nonlinear dynamics of phytoplankton. In this study, this approach was applied to predict absence-presence and abundance of Karlodinium and Pseudo-nitzschia microalgae in Alfacs Bay (NW Mediterranean) using biological and/or environmental variables. Neural Interpretation Diagram (NID) and Connection Weight Approach (CWA) methodologies were applied to obtain ecological information from the models. The dataset used was long-term (1990–2015) time series of environmental and phytoplankton variables from different monitoring stations established in Alfacs Bay (Ebre Delta), meteorological data and Ebre River flow rates. Several models were presented. The best ones were achieved for one-week ahead procedures performed with environmental and biological variables using all the available data. A sensitivity analysis showed the larger the data set used, the better the models obtained. However, Karlodinium absence-presence models developed with five years of data present high accuracy. The size of the neural networks denotes complex relationships between environmental and phytoplankton variables. The environmental variables had stronger influence on the abundance models while biological variables had more importance in the absence-presence models. These results highlight a complex ecosystem in Alfacs Bay involving anthropogenic, climatic and hydrologic factors forcing phytoplankton dynamics. In addition, a change in the ecosystem dynamics regarding Karlodinium is detected. The configuration and the accuracy achieved with the models allow their use in different real-world applications as automated systems and/or monitoring programs, This research, including CG contract, has been funded by the Economy and Competitiveness Ministry of Spain under the program INNPACTO 2011 (“PURGADEMAR” project; IPT-2011-1707-310000) and INIA (project PROMAQUA RTA2013-00096-00-00)

An expansion of the distribution of Ostreopsis cf. ovata, a dinoflagellate which produces palytoxin-like compounds, has been reported in recent years. Economical and social interests are affected by blooms, as they are responsible for respiratory and skin problems in humans and may cause damage to marine organisms. In order to identify the most influential environmental factors that trigger proliferations of O. cf. ovata in the area of the adjacent shallow rocky coast of the Ebro Delta (NW Mediterranean Sea) a three-year survey was performed on the metaphytic microalgae community growing on the macrophytes Jania rubens and Corallina elongata. Small-size diatoms were more abundant than dinoflagellates; O. cf. ovata was identified as the only species present from the genus. Seawater temperature was the primary driver defining the ecological niche of O. cf. ovata. Freshwater and groundwater fluxes were more pronounced in southern than in northern sites, which may have resulted in a distinct O. cf. ovata spatial distribution, with the highest records of abundance and more frequent blooms in the north. In consequence, negative correlations between the abundance of O. cf. ovata and nitrate concentrations and significant positive correlation with salinity were observed. The temporal pattern of O. cf. ovata dynamics from mid-July to early-November is probably due to the fact that this species is observed only above a certain threshold temperature of seawater. Metaphytic cells of O. cf. ovata were smaller in the northern site than in the south, possibly as a result of an increase in cell division, coinciding with higher abundance, and this could be an indicator of favorable conditions. Toxicity in planktonic cells was negatively correlated with cell abundance in the water column, achieving maximum concentrations of 25pg. PLTX eqcell(-1).