CONSEQUENCES OF SINGULAR ENVIRONMENTAL EVENTS ON THE CYCLE OF METALS IN COASTAL LAGOONS AND THEIR INFLUENCE ON THE INCORPORATION OF METALS BY PRIMARY PRODUCERS

Coastal areas are valuable and sensitive environments subjected to great anthropogenic pressure. Among these pressures, metal pollution is of priority concern as these pollutants can reach concentrations that exceed the levels established to protect sensitive organisms in the ecosystem. In coastal lagoons, shallow systems with a reduced exchange with the open sea, metal concentrations are one or two orders of magnitude higher than in open-waters. In addition, these systems are subjected to physicochemical variations that can alter the biogeochemical cycling of the metals. Singular environmental events such as strong winds cause metal resuspension, torrential rain events provoke the entrance of solutes and pollutants, and phytoplankton blooms dramatically increase the concentration of organic matter. These events provoke alterations in the concentration and speciation of metals in the water column. This will have a direct impact in the organisms living in the area, since metal toxicity and bioavailability depends on the chemical speciation. Dissolved organic matter (DOM) is the most important variable influencing metal speciation and bioavailability in seawater. However, the effects of DOM on metal bioavailability have not been yet unravelled and contrasting results have been reported, some showing that DOM protects against metal toxicity and others showing the opposite. The present study was designed to study how the biogeochemical cycling of trace metals in the water column of coastal lagoons is influenced by these singular environmental events and how this affects the incorporation of metals by the primary producers, in this case, microalgae, with particular focus on the effect of dissolved organic matter on metal biouptake. The proposed work combines field sampling and analytical work in the Mar Menor lagoon (SE Spain). This project will substantially contribute to widen our knowledge about the behaviour of metals in coastal areas and to determine how the presence of DOM affects their toxicity

EFFECT OF DISSOLVED ORGANIC MATTER ON COPPER BIOAVAILABILITY TO A COASTAL DINOFLAGELLATE

Metal complexation by dissolved organic matter (DOM) is considered to decrease metal bioavailability by lowering the free metal ion concentration, therefore protecting organisms from the deleterious effects of metals (Campbell et al., 2002). In coastal lagoons like Mar Menor, with high terrestrial influence and low exchange with open sea, the levels of both DOM and metals are one or two orders of magnitude higher than in open-waters. In order to verify the free ion activity model (FIAM), copper internalization by Prorocentrum micans, a cosmopolitan dinoflagellate also present in the Mar Menor, was tested in the absence and presence of two types of DOM, commercially available fulvic acids from riverine origin (SRFA) and coastal DOM obtained by ultrafiltration (UF-DOM). The microalgae were exposed to artificial sea water enriched with increasing amounts of Cu65 isotope, at levels from 5 to 100 nM Cu, solely and in combination with DOM. After one-hour exposure, samples were centrifuged and washed and pellets were digested with nitric acid at 90ºC, following Sánchez-Marín et al (2010) and Croteau and Luoma (2005). In parallel, careful measurements of metal complexation by anodic stripping voltammetry (ASV) were performed and total Cu concentrations were measured by ICP-MS. Preliminary results show that copper internalization by the microalgae increases linearly as a function of labile Cu, both in the absence and presence of DOM, in agreement with FIAM and with labile Cu measurements performed by ASV. Future work might include testing the influence of competing metals, such as Pb or Zn, on Cu internalization, and to study Cu bioavailability in natural samples collected in the Mar Menor, in order to shed light into the factors that control Cu bioavailability in coastal lagoons

COPPER AND LEAD COMPLEXATION BY DISSOLVED ORGANIC MATTER IN MAR MENOR COASTAL LAGOON

Mar Menor coastal lagoon is a shallow system with a reduced exchange with the open sea, that is affected by several anthropogenic pressures, mainly agriculture and mining. The mining sierra of Cartagena-La Unión has been historically discharging mining waste rich in heavy metals in the south area of Mar Menor, resulting in high metal concentrations in sediments (García and Muñoz-Vera., 2015). The nutrients reaching the lagoon, together with the high temperatures, also provoke phytoplankton blooms that lead to high concentrations of dissolved organic matter (DOM). It is well known that total metal concentrations are not good predictors of their bioavailability, and metal speciation should be taken into account. The presence of ligands, such as DOM in the water, may form metal-DOM complexes and protect against the deleterious effects of metals. The present study aims at studying the effect of DOM on the speciation of dissolved metals (Cu and Pb) in Mar Menor waters. With that aim, filtered water was sampled at five sites in Mar Menor lagoon at several sampling periods. Metal concentration was analysed by ICP-MS with Argon gas dilution, DOC was analysed in a carbon-specific infrared gas analyser and optical characterization of DOM was obtained from absorbance and fluorescence spectra. Complexiometric titrations of Cu and Pb were performed by anodic stripping voltammetry following Durán and Nieto (2011). Preliminary results show that Cu and Pb concentrations in Mar Menor waters are higher than in other coastal areas, especially in the south area of the lagoon, reaching concentrations of tens of nanomolar. DOC concentrations are also very high in Mar Menor waters, leading to high complexation capacities for Cu, therefore protecting aquatic biota from the deleterious effects of Cu. Pb, on the contrary, is poorly complexed by DOM, and almost all dissolved Pb is present in inorganic forms

Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)

12 páginas, 5 figuras, 2 tablasAnthropogenic pressures are changing the magnitude and nature of matter inputs into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area. In order to assess short-term responses in biomass, production, and respiration of heterotrophic bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6 microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and primarily limited by C in autumn. Production responded more than biomass to increasing inputs of matter, whereas respiration did not change. The bacterial production response to increasing dissolved organic C load associated with riverine and atmospheric inputs was strongly related to the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that bacterial production might decrease with the increase of P-deficient allochthonous matter inputs, which would have important biogeochemical consequences for C cycling in coastal areasThis research was supported by the Spanish Ministry of Science and Innovation through project REIMAGE (grants CTM2011-30155-C03-01 and CTM2011-30155-C03-02) and by the Xunta the Galicia trough project DIMENSION (grant EM2013/023). E. B-L was funded by a F.P.I. MICINN fellowship. M.N.-C. was funded by the CSIC Program "Junta para la Ampliación de Estudios" co-financed by the ESF. S.M.G. was funded by a Marie Curie fellowshipPeer reviewe

Effect of dissolved organic matter on copper bioavailability to a coastal dinoflagellate at environmentally relevant concentrations

12 pages, 2 tables, 6 figures.-- Under a Creative Commons licenseThe speciation and bioavailability of copper (Cu) in the marine environment are affected by the presence of dissolved organic matter (DOM). Previous studies conducted at dissolved Cu concentrations >100 nM confirmed that Cu bioavailability depends on the concentration of labile Cu, as measured by anodic stripping voltammetry (ASV), which aligns with the expectations of the biotic ligand model (BLM). However, ambient Cu concentrations in coastal waters are generally lower, ranging between 1 and 80 nM, and the effect of DOM on the bioavailability of Cu to marine organisms has not been tested within that range of Cu concentrations. The present study aims to assess the impact of two types of DOM, a commercially available fulvic acid, and marine DOM extracted by ultrafiltration, on Cu bioavailability to phytoplankton using short-term 65Cu internalisation by the marine dinoflagellate Prorocentrum micans. Results showed that Cu internalisation decreases with DOM additions as expected according to the BLM and in agreement with ASV measurements of labile Cu, at the highest tested Cu concentration (100 nM). On the contrary, at a lower Cu concentration (20 nM), organic complexes appear to be partially bioavailable, thereby challenging the general applicability of the BLM model at environmentally relevant concentrations in coastal areasThis study was funded by the Spanish Ministry of Science and Innovation through project SEE-ME (PID2019-109355RA-I00)Peer reviewe

Response of pico-nano-eukaryotes to inorganic and organic nutrient additions

11 pages, 5 figures, 2 tables, supplementary data https://doi.org/10.1016/j.ecss.2019.106565Organic nutrient loading in coastal waters has considerably increased due to anthropogenic activities over the last decades. In particular, the increase in the proportion of organic vs. inorganic nitrogen may have an impact on microbial plankton communities, particularly within the small size classes, where mixotrophy is likely to be widespread. Here we explore the change in taxonomic composition of small eukaryotes (<20 μm) populating a productive coastal system in response to inorganic and/or organic nutrient amendments using 18S rRNA gene sequencing. Major changes in the community were observed in the mixed treatment, containing both inorganic and organic nutrients, which mostly affected phytoplankton taxa. Adding mixed nutrients had a positive effect on pigmented groups, when compared to additions of inorganic nutrients. The responding pigmented groups included dinoflagellates, cryptophyceans, chrysophyceans, bolidophyceans or dictyochophyceans, which comprise mixotrophic species, but also groups that are considered to be strictly autotrophs, such as diatoms or mamiellophyceans. Our results highlight the importance of organic nutrients for growth of small phytoplankton. The combination of both, autotrophic and heterotrophic capabilities, is possibly an advantage for small phytoplankton to thrive when inorganic nutrients or light are limiting or suboptimalThis research was supported by the Xunta de Galicia through DIMENSION project (grant EM2013/023) and by Spanish Ministry of Economy, Industry and Competitivity (MINECO) trough ENVISION project (grant CTM2014-59031-P) in collaboration with the “Instituto Español de Oceanografía” (IEO) RADIALES project. Esther Barber-Lluch was funded by an F.P.I. MINECO fellowship. [...] R. Logares was supported by a Ramón y Cajal fellowship (RYC-2013-12554, MINECO, Spain)With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI

Microbial plankton community responses to nutrient additions and B12-vitamin additions

Comunicación oralRecent studies in coastal waters suggest that phytoplankton is eventually limited or colimited by some metabolites derived from bacterial activity. The majority of phytoplankton species require an exogenous source of B12 vitamin for growth. As only selected prokaryotes are able to synthesize B12, they must be the ultimate source of B12 for auxotrophic phytoplankton. We conducted 3 microcosm experiments to assess the response of microbial plankton to B12-vitamin amendment in the coastal-ocean transition zone off NW Spain. Surface seawater was mixed with inorganic nutrients, B12-vitamin or a combination of both and incubated during 72h, under in situ temperature and light conditions. Size-fractionated (20, 3 and 0.2 μm) chlorophyll-a concentration and picoplankton abundance were monitored every 24h and changes in the size-fractionated eukaryotic and prokaryotic community structure were assessed by ARISA (automatic rRNA intergenic spacer analysis) at the end of the experiments. We observed that phytoplankton responded to B12-vitamin (alone or in combination) in 2 experiments. Nanophytoplankton was the most responsive fraction in terms of biomass, whereas changes in community structure associated to B12-vitamin addition were mainly observed for large eukaryotes

Cooper and lead complexation by dissolved organic matter in Mar menor coastal lagoon

Seminario Ibérico de Química Marina (SIQUIMAR), Las Palmas de Gran Canaria (Spain), 6-8th July 2022Mar Menor coastal lagoon is a shallow system with a reduced exchange with the open sea, that is affected by several anthropogenic pressures, mainly agriculture and mining. The mining sierra of Cartagena-La Unión has been historically discharging mining waste rich in heavy metals in the south area of Mar Menor, resulting in high metal concentrations in sediments (García and Muñoz-Vera., 2015). The nutrients reaching the lagoon, together with the high temperatures, also provoke phytoplankton blooms that lead to high concentrations of dissolved organic matter (DOM). It is well known that total metal concentrations are not good predictors of their bioavailability, and metal speciation should be taken into account. The presence of ligands, such as DOM in the water, may form metal-DOM complexes and protect against the deleterious effects of metals. The present study aims at studying the effect of DOM on the speciation of dissolved metals (Cu and Pb) in Mar Menor waters. With that aim, filtered water was sampled at five sites in Mar Menor lagoon at several sampling periods. Metal concentration was analysed by ICP-MS with Argon gas dilution, DOC was analysed in a carbon-specific infrared gas analyser and optical characterization of DOM was obtained from absorbance and fluorescence spectra. Complexiometric titrations of Cu and Pb were performed by anodic stripping voltammetry following Durán and Nieto (2011). Preliminary results show that Cu and Pb concentrations in Mar Menor waters are higher than in other coastal areas, especially in the south area of the lagoon, reaching concentrations of tens of nanomolar. DOC concentrations are also very high in Mar Menor waters, leading to high complexation capacities for Cu, therefore protecting aquatic biota from the deleterious effects of Cu. Pb, on the contrary, is poorly complexed by DOM, and almost all dissolved Pb is present in inorganic formsThis work has been supported by the Spanish Ministry Science and Innovation and by the European Union through the European Regional Development Fund (ERDF) through ‘SEEME’ PID2019-109355RA-I00) projectN

Seasonal succession of small planktonic eukaryotes inhabiting surface waters of a coastal upwelling system

19 pages, 7 figures, 1 tableSmall eukaryotes (0.2–20 μm cell‐size) represent a significant fraction of the microbial plankton community in shelf waters of NW‐Spain. The community composition of small eukaryotes living at the surface and at the base of the photic zone was analysed by means of 18S rDNA high‐throughput sequencing on a circa‐monthly basis over a 23 months period. Ostreococcus was the most abundant taxon in surface waters, showing marked peaks in read abundance in spring and late summer, while Syndiniales dominated at the base of the photic zone. A well‐defined seasonal pattern of community composition, linked to the succession of the dominant taxa, was found in surface waters. Seasonality was less apparent at the base of the euphotic zone. Temporal changes in abiotic factors significantly correlated with changes in community composition in surface (r = 0.71) and at the base of the photic zone (r = 0.38). Changes in community composition significantly correlated with changes in community function‐related variables (including biomass, primary production and respiration) only in surface water (r = 0.36). Co‐occurrence network analyses revealed 45 significant interspecies associations among the 50 most abundant taxa with highly connected OTUs belonging to cryptophyceans. The network topology, with small‐world characteristics, suggests a stabilizing role of biotic interactions to environmental disturbanceThis research was supported by the Xunta the Galicia through DIMENSION project (grant EM2013/023) and by Spanish Ministry of Economy, Industry and Competitivity (MINECO) trough ENVISION project (grant CTM2014‐59031‐P) in collaboration with the ‘Instituto Español de Oceanografía’ (IEO) RADIALES project. Esther Barber‐Lluch was funded by an F.P.I. MINECO fellowshipPeer reviewe