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- Estrutura e dinâmica da teia alimentar microbiana na Ria FormosaPublication . Barbosa, Ana B.; Galvão, Helena M.
- What are jellyfish really eating to support high ecophysiological condition?Publication . Morais, Pedro; Parra, María P.; Marques, Raquel; Angélico, Maria Manuel; Chainho, Paula; Costa, José Lino; Barbosa, Ana B.; Teodosio, Maria; Cruz, JoanaThe feeding ecology of Blackfordia virginica was evaluated concurrently with their ecophysiological condition in a temperate estuary. The diet of B. virginica is composed not only of metazooplankton, as commonly observed for other jellyfish species, but also of phytoplankton, ciliates and detritus. This feeding behavior might explain their good nutritional condition and sustainable growth during bloom peaks, when zooplankton abundance has already decreased significantly.
- Polar marine biology science in Portugal and Spain: Recent advances and future perspectivesPublication . Xavier, J.; Barbosa, Ana B.; Agustí, S.; Alonso-Sáez, L.; Alvito, P.; Ameneiro, J.; Ávila, C.; Baeta, A.; Canário, J.; Carmona, R.; Catry, P.; Ceia, F.; Clark, M. S.; Cristobo, F. J.; Cruz, B.; Duarte, C. M.; Figuerola, B.; Gili, J.-M.; Gonçalves, A. R.; Gordillo, F. J. L.; Granadeiro, J. P.; Guerreiro, M.; Isla, Enrique; Jiménez, C.; López-González, P. J.; Lourenço, S.; Marques, J. C.; Moreira, E.; Mota, A. M.; Nogueira, M.; Núñez-Pons, L.; Orejas, C.; Paiva, V. H.; Palanques, A.; Pearson, G. A.; Pedrós-Alió, C.; Peña Cantero, T. L.; Power, Deborah; Ramos, J. A.; Rossi, S.; Serrão, EsterPolar marine ecosystems have global ecological and economic importance because of their unique biodiversity and their major role in climate processes and commercial fisheries, among others. Portugal and Spain have been highly active in a wide range of disciplines in marine biology of the Antarctic and the Arctic. The main aim of this paper is to provide a synopsis of some of the results and initiatives undertaken by Portuguese and Spanish polar teams within the field of marine sciences, particularly on benthic and pelagic biodiversity (species diversity and abundance, including microbial, molecular, physiological and chemical mechanisms in polar organisms), conservation and ecology of top predators (particularly penguins, albatrosses and seals), and pollutants and evolution of marine organisms associated with major issues such as climate change, ocean acidification and UV radiation effects. Both countries have focused their polar research more in the Antarctic than in the Arctic. Portugal and Spain should encourage research groups to continue increasing their collaborations with other countries and develop multi-disciplinary research projects, as well as to maintain highly activememberships within major organizations, such as the Scientific Committee for Antarctic Research (SCAR), the International Arctic Science Council (IASC) and the Association of Polar Early Career Scientists (APECS), and in international research projects.
- Seasonal and interannual variability of planktonic microbes in a mesotidal coastal lagoon (Ria Formosa, SE Portugal): impact of climatic changes and local human influencesPublication . Barbosa, Ana B.The Ria Formosa coastal lagoon is a multi-inlet mesotidal system, located along the south coast of Portugal. It is subjected to multiple anthropogenic influences and is situated in a region classified as very vulnerable to climate change. This study aimed to describe the seasonal and interannual variability of planktonic microbes in the lagoon, the driving forces underlying microbe variability, and the relative contribution of climate and local-human influences. Changes in anthropogenic activities or climatic processes affecting the Ria Formosa Lagoon were identified for the period 1967 to 2008 and linked to current knowledge on abiotic variables and planktonic microbes in the western subembayment of the lagoon. Phytoplankton and heterotrophic bacterioplankton at inner lagoon locations exhibited unimodal annual cycles with summer peaks, coupled to temperature and light availability, whereas phytoplankton at inlet areas displayed a bimodal annual cycle, probably more intensively controlled by nutrient availability. The effects of increased anthropogenic pressure, both on seasonal and interannual time scales, were evident only at sites close to major urban centers, probably due to the low water residence time inside the lagoon, and the relevance of physical variables (e.g., temperature and light) as drivers of the growth of planktonic microbes. Long-term climatic variability apparently reverberated into the lagoon’s water column, leading to a generalized and significant winter warming trend, and strong interannual changes in the concentration of inorganic nutrients, particularly during the autumn–winter period. Phytoplankton biomass showed a generalized interannual declining trend during autumn and winter. This decline may be eventually related to the winter warming tendency, through its stimulatory effect upon phytoplankton grazers, or to decreases in nutrient concentrations associated with reductions in the autumn freshwater inflow. Long-term changes during spring and summer were less coherent across lagoon stations, indicating that more site-specific processes were driving phytoplankton variability. Despite overall reduced freshwater flows into the lagoon, interannual freshwater flow variability apparently exerted an important control on the biomass of phytoplankton, particularly during periods of relatively high flow rates and low light limitation (spring and autumn). Overall, synthesized data suggest that climate variability is an important driver of planktonic microbes in the lagoon, both on shortterm, seasonal, and interannual time scales. Local anthropogenic impacts are apparently spatially restricted. More extensive time-series and dedicated experiments are needed to conclusively establish direct links between the dynamics of planktonic microbes and climatic and local anthropogenic alterations in the Ria Formosa Lagoon.
- Are microcosm volume and sample pre-filtration relevant to evaluate phytoplankton growth?Publication . Nogueira, Patrícia; Domingues, Rita B.; Barbosa, Ana B.“Bottle effects” are one of the most deeply rooted concerns of phytoplankton microcosm studies and are mainly related to incubation time and sample volume. Sample pre-filtration to remove larger grazers is also a common procedure in experimental phytoplankton ecology studies, particularly in nutrient enrichment experiments. However, the effects of bottle volume and sample pre-filtration on the outcomes of such experiments, particularly on the net growth rates of specific phytoplankton taxa, have never been addressed. Therefore, this study aims to evaluate the effects of different bottle volumes and sample pre-filtration on phytoplankton net growth rates in microcosm experiments. To accomplish this goal, unfiltered and filtered (b100 μm)water samples, collected in the Guadiana estuary,were nutrient-enriched to avoid nutrient limitation and incubated for 3 days in polycarbonate microcosms with different volumes (0.5 L–8.0 L), inside a plant growth chamber. Phytoplankton composition, abundance, biomass and taxon-specific net growth rates were evaluated throughout the experiment. No systematic significant effects of bottle volume were detected in phytoplankton growth rates. However, sample filtration caused significant changes in phytoplankton composition, with a decline of diatom abundance. Moreover, the removal of large-sized predators and large-sized phytoplankton (diatoms) after sample filtration cascaded down the food web, affecting taxon-specific net growth rates differently. Net growth rates of green algae and eukaryotic picophytoplankton were significantly higher in filtered treatments in respect to unfiltered treatments. Conversely, both diatoms and cryptophytes presented higher net growth rates in unfiltered treatments while net growth rates of picoplanktonic cyanobacteria and plastidic nanoflagellates were not affected by sample filtration.We conclude that, while microcosm volume does not affect results in phytoplankton microcosms, sample pre-filtration may significantly alter the structure of the original phytoplankton community and hence increase the problems associated with the extrapolation of experimental outcomes to the natural environment.
- Co-limitation of phytoplankton by N and P in a shallow coastal lagoon (Ria Formosa): implications for eutrophication evaluationPublication . Domingues, Rita B.; Nogueira, Patricia; Barbosa, Ana B.The Ria Formosa coastal lagoon is a highly productive shallow ecosystem in southern Portugal, subjected to nutrient inputs from anthropogenic and natural sources. Nutrients are major abiotic drivers of phytoplankton in this system, but their effects on phytoplankton assemblages and the occurrence of nutrient limitation are still poorly understood. The main goal of this study was, thus, to evaluate the occurrence, type, and effects of nutrient limitation on phytoplankton community and specific functional groups in the Ria Formosa coastal lagoon. We conducted nutrient enrichment experiments with factorial additions of nitrogen (N) and phosphorus (P) using natural phytoplankton assemblages from distinct locations in the Ria Formosa, throughout a yearly cycle. Phytoplankton composition and abundance were evaluated using inverted and epifluorescence microscopies, and spectrophotometric methods were used for biomass. Limitation was defined as higher phytoplankton growth following enrichment with a particular nutrient in relation to the non-enriched control. The most common type of phytoplankton limitation was simultaneous co-limitation by N and P; diatoms, as r-strategists, were the most frequently limited group. Single N and P limitation, and serial P limitation were also observed, as well as negative responses to nutrient enrichment. Group-specific responses to nutrient enrichment were not reflected in the relative abundance of phytoplankton groups within the whole assemblage, due to the numerical dominance of pico-sized groups (cyanobacteria and eukaryotic picophytoplankton). Ambient nutrient ratios and concentrations did not predict phytoplankton nutrient limitation, given the different nutrient utilisation traits among phytoplankton functional groups. Therefore, nutrient ratios should not be used as indicators of nutrient limitation in eutrophication assessment.
- Tidal variability of phytoplankton and their environmental drivers in the freshwater reaches of the Guadiana estuary (SW Iberia)Publication . Domingues, Rita B.; Anselmo, Tânia P.; Barbosa, Ana B.; Sommer, Ulrich; Galvão, Helena M.The effects of different phases of semidiurnal and spring-neap tidal cycles on phytoplankton and environmental drivers were evaluated in a tidal, freshwater location of a mesotidal estuary (Guadiana estuary, SW Iberia). An Eulerian approach was used and sampling covered different seasons during 2008. Samples were collected during spring and neap tides, at high tide, mid-ebb, low tide and mid-flood. Several physical-chemical variables were measured, as well as phytoplankton abundance and biomass. Salinity was higher at high-tide and suspended particulate matter was higher during spring tides and flood, due to higher vertical mixing and resuspension of bottom sediments. Chlorophyll a concentration during winter and summer neap tides was higher than during spring tides, whilst the abundance of pennate diatoms was higher during winter and Spring spring tides than during neap tides, probably reflecting differences in river discharge. Overall, tidally-induced differences detected in the freshwater tidal reaches of the Guadiana estuary were not as considerable as those observed in the lower estuary. However, the occurrence of tidally-induced variability in some seasons reflects that thorough sampling programs to study estuarine tidal dynamics should be conducted throughout the year. Occasional sampling will not reflect the typical variability of these highly dynamic systems.
- Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: looking for region-specific environmental drivers and predictorsPublication . Lima, M.J.; Relvas, Paulo; Barbosa, AnaHarmful algal blooms (HABs) negatively impact coastal ecosystems, fisheries, and human health, and their prediction has become imperative for effective coastal management. This study aimed to evaluate spatialtemporal variability patterns and phenology for key toxigenic phytoplankton species off southern Portugal, during a 6-year period, and identify region-specific environmental drivers and predictors. Total abundance of species responsible for amnesic shellfish poisoning (Pseudo-nitzschia spp.), diarrhetic shellfish poisoning (Dinophysis spp.), and paralytic shellfish poisoning (G. catenatum) were retrieved, from the National Bivalve Mollusk Monitoring System public database. Contemporaneous environmental variables were acquired from satellite remote sensing, model-derived data, and in situ observations, and generalized additive models (GAMs) were used to explore the functional relationships between HABs and environmental variables and identify regionspecific predictors. Pseudo-nitzschia spp. showed a bimodal annual cycle for most coastal production areas, with spring and summer maxima, reflecting the increase in light intensity during the mixed layer shoaling stage, and the later stimulatory effects of upwelling events, with a higher bloom frequency over coastal areas subjected to stronger upwelling intensity. Dinophysis spp. exhibited a unimodal annual cycle, with spring/summer maxima associated with stratified conditions, that typically promote dinoflagellates. Dinophysis spp. blooms were delayed with respect to Pseudo-nitzschia spp. spring blooms, and followed by Pseudo-nitzschia spp. summer blooms, probably reflecting upwelling-relaxation cycles. G. catenatum occurred occasionally, namely in areas more influenced by river discharges, under weaker upwelling. Statistical-empirical models (GAMs) explained 7-8%, and 21− 54% of the variability in Pseudo-nitzschia spp. and Dinophysis spp., respectively. Overall, a set of four easily accessible environmental variables, surface photosynthetically available radiation, mixed layer depth, sea surface temperature, and chlorophyll-a concentration, emerged as the most influential predictors. Additionally, over the coastal production areas along the south coast, river discharges exerted minor negative effects on both HAB groups. Despite evidence supporting the role of upwelling intensity as an environmental driver of Pseudonitzschia spp., it was not identified as a relevant model predictor. Future model developments, such as the inclusion of additional environmental variables, and the implementation of species- and period-specific, and hybrid modelling approaches, may further support HAB operational forecasting and managing over complex coastal domains.
- Light as a driver of phytoplankton growth and production in the freshwater tidal zone of a turbid estuaryPublication . Domingues, Rita B.; Anselmo, Tânia P.; Barbosa, Ana B.; Sommer, Ulrich; Galvão, Helena M.Light is usually the main driver of phytoplankton growth in turbid estuaries, but it has received far less attention than nutrients as a bottom-up factor. This study presents the first experimental analysis of light limitation of phytoplankton growth and production and its seasonal variability in the freshwater tidal reaches of the turbid Guadiana estuary, SE Portugal/SW Spain. Natural phytoplankton communities were exposed to different photosynthetically active radiation (PAR) intensities. Short-term incubations with addition of 14HCO3 were used to estimate photosynthetic parameters and long-term incubations allowed the evaluation of the effects of light on phytoplankton composition and growth. Light limitation of phytoplankton growth occurred throughout the year in the freshwater tidal reaches of the estuary and no photoinhibition was observed at least up to 615 mmol photonsm 2 s 1. In the summer, co-limitation by nutrients prevented a positive response of phytoplankton to light enrichment. Diatoms were the most light-limited group, whilst cyanobacteria were the only group acclimated to low-light conditions. Green algae and dinoflagellates responded positively to higher PAR exposures. High saturating irradiances, high light-saturated rates of primary production and low photosynthetic efficiencies suggest that phytoplankton community was not acclimated to the low-light conditions that prevail in the Guadiana estuary.
- Impacts of decommissioning and upgrading urban wastewater treatment plants on the water quality in a shellfish farming coastal lagoon (Ria Formosa, South Portugal)Publication . Jacob, J.; Correia, Cátia; Torres, Ana Flor; Xufre, Gustavo; Matos, André Filipe; Ferreira, Cristina; Reis, Margarida; Caetano, Sandra; Freitas, Carla; Barbosa, Ana B.; Cravo, AlexandraRia Formosa is a productive coastal lagoon, located on the south coast of Portugal, and represents the largest national producer of shellfish bivalves (ca. 90% production). This ecosystem is subjected to various anthropogenic pressures, including the discharge of urban wastewater treatment plants (UWWTP), which impacts the lagoon water quality. This study aimed to assess the impact of alterations in the functioning of two UWWTP on the water quality of Ria Formosa, based on chemical variables, phytoplankton composition ( including potential harmful species) and faecal contamination. During the period September 2018 - October 2019, water sampling was conducted along dominant longitudinal gradients of the effluent dispersion from the discharge point (1-2 km), for two sites: a decommissioned (OP) and a modified (FO) UWWTP. After modification, the later started receiving a higher influent volume (ca. 40%), under an innovative technology system (biological treatment in aerobic granular sludge). Based on chemical water quality variables, phytoplankton and indicators of faecal contamination, a significant improvement along the longitudinal gradient from the discharge point was observed after OP decommissioning. This improvement was fast, being detected two months after decommissioning, positively affecting areas used as shellfish farming grounds. However, distribution patterns of bacteriological indicators and regular shellfish harvesting interdictions suggested an alternative source of faecal contamination after OP decommissioning. At FO, both chemical variables and bacteriological indicators of faecal contamination revealed a slower improvement, only six-months after the UWWTP alteration. Before that, increased and highly variable ammonium, chlorophyll a concentration, phytoplankton abundances and Escherichia coli densities, revealed an unstable phase. Overall, a lower water quality at FO in respect to OP reflected not only a higher effluent volume but also more restricted water circulation for the former.