Browsing by Author "Barbosa, Ana"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Allochthonous-derived organic matter subsidizes the food sources of estuarine jellyfishPublication . Morais, Pedro; Dias, Ester; Cruz, Joana; Chainho, P.; Costa, J. L.; Angélico, M. M.; Barbosa, Ana; Teodosio, MariaJellyfish modulate the energy fluxes between compartments of aquatic ecosystems and the period that energy remains within each compartment. However, the contribution of different sources of organic matter (OM) to the production of most estuarine jellyfish species is unknown. Therefore, this study aimed to identify and quantify the putative sources of OM for Blackfordia virginica (Cnidaria, Hydrozoa) Mayer, 1910 in two temperate estuaries, based on the analyses of carbon and nitrogen stable isotope ratios. Zooplankton was the main source of OM assimilated by B. virginica in both Mira and Guadiana estuaries. However, particulate organic matter (POM) also contributed to B. virginica biomass, up to 26 and 37% in Mira and Guadiana estuaries, respectively. The POM pool was apparently comprised by terrestrial derived OM, as based on stable isotope ratios and C:NPOM. Terrestrial-derived OM is an undescribed carbon source for estuarine jellyfish. Our results support a working hypothesis stating that terrestrial-derived OM might support good physiological condition of B. virginica during periods of low metazooplankton abundance, through a detritus based microbial food web transformation. Subsequent studies on trophic pathways ought to evaluate the temporal contribution of autochthonous and allochthonous OM and its consequences, accounting for the connectivity across ecosystems (terrestrial-estuarine-marine) and the interactions within compartments (pelagic-benthic).
- Ammonium, nitrate and phytoplankton interactions in a freshwater tidal estuarine zone: potential effects of cultural eutrophicationPublication . Domingues, Rita B.; Barbosa, Ana; Sommer, Ulrich; Galvão, Helena M.Nitrate and ammonium are the most important nitrogen sources for phytoplankton growth. Differential utilization of inorganic nitrogenous compounds by phytoplankton has been observed and may have significant impacts on primary productivity at local scales. We used enrichment experiments with natural phytoplankton populations from the freshwater tidal zone of the Guadiana estuary, a coastal ecosystem increasingly subjected to anthropogenic influences, to study the effects of nitrate and ammonium on N-consumption and phytoplankton growth. In addition, we used combined additions of nitrate and ammonium to understand the inhibitory effect of ammonium over nitrate uptake. Ammonium concentrations in the freshwater tidal reaches of the Guadiana estuary throughout the sampling period were too low to exert an inhibitory effect on nitrate uptake or a toxic effect on phytoplankton growth. Nitrate was clearly the main nitrogen source for phytoplankton at the study site. Overall, nitrate seemed to become limiting at concentrations lower than 20 lM and N-limitation was particularly significant during summer. A trend of decreasing nitrate uptake with increasing ammonium concentrations and uptake suggested an overall preference for ammonium. However, preference for ammonium was group-specific, and it was observed mainly in green algae and cyanobacteria. In fact, cyanobacteria relied only on ammonium as their N-source. On the contrary, diatoms preferred nitrate, and did not respond to ammonium additions. The increasing eutrophication in the Guadiana estuary and particularly increased inputs of nitrogen as ammonium due to urban waste effluents may result in a shift in phytoplankton community composition, towards a dominance of cyanobacteria and green algae.
- Gelificação dos oceanos – e a culpa não é da alforrecaPublication . Morais, Pedro; Amorim, Katherine; Dias, Ester; Cruz, Joana; Barbosa, Ana; Teodosio, MariaOcean jellification is associated with increasing occurrence of jellyfishes. Jellyfish are gelatinous organisms, with a life cycle composed by sessile stage (polyp) and free living stage (medusa). Blooms jellies, which may have negative impact on fisheries and tourism, are strongly driven by the availability of food, since predators are relatively reduce. The diet of jellies includes small crustacean, egg and fish larvae. Yet, recent UAlg studies showed a much more diverse diet (ex: drifting microbes, terrestrial detritus). Major contributors for ocean jellification are closed connect to men activities and include: (1) excessive input of nutrients (ex: sewage agriculture fertilizers), (2) overfishing of fishes and sea turtles; (3) introduction of artificial structures and (4) changes in hydrological cycle (ex: river dams).
- Impacts of sample storage time on estimates of phytoplankton abundance: how long is too long?Publication . Nogueira, Patricia; Barbosa, Ana; Domingues, RitaPhytoplankton play a key role in marine ecosystems, making the accurate quantification of functional groups/species, using standardized microscopy techniques, essential in many research efforts. In this study we aimed to evaluate the effects of (a) storage time on the abundance of microphytoplankton in samples fixed with acid Lugol’s solution; (b) storage time on the abundance of pico- and nanophytoplankton in frozen microscopy slides; (c) storage time on the abundance of pico- and nanophytoplankton in fixed refrigerated samples and (d) storage protocol (refrigerated versus frozen) on the abundance of pico- and nanophytoplankton. Microphytoplankton were analyzed using inverted microscopy, and pico- and nanophytoplankton using epifluorescence microscopy. Results indicate storage time negatively impacted the abundances of all phytoplankton size classes; however, effects were group-specific. For accurate abundance estimates, we suggest that samples fixed with acid Lugol’s should be analyzed within 30 and 180 days, for dinoflagellates/total microphytoplankton and diatoms, respectively. For picoeukaryotes, glutaraldehyde fixed samples should be kept refrigerated for up to 4 days, and slides should be prepared immediately before observation. It is recommended that authors specify the exact lag times between sample collection, fixation and analysis, to allow the comparability of phytoplankton datasets across different studies and/or monitoring programs.
- Short-term effects of climate change on Planktonic Heterotrophic Prokaryotes in a temperate coastal lagoon: temperature is good, ultraviolet radiation is bad, and CO2 is neutralPublication . Barbosa, Ana; Mosley, Benjamin A.; Galvão, Helena; Domingues, RitaPlanktonic heterotrophic prokaryotes (HProks) are a pivotal functional group in marine ecosystems and are highly sensitive to environmental variability and climate change. This study aimed to investigate the short-term effects of increasing carbon dioxide (CO2 ), ultraviolet radiation (UVR), and temperature on natural assemblages of HProks in the Ria Formosa coastal lagoon during winter. Two multi-stressor microcosm experiments were used to evaluate the isolated and combined effects of these environmental changes on HProk abundance, production, growth, and mortality rates. The isolated and combined effects of increased CO2 on HProks were not significant. However, HProk production, cellular activity, instantaneous growth rate, and mortality rate were negatively influenced by elevated UVR and positively influenced by warming. Stronger effects were detected on HProk mortality in relation to specific growth rate, leading to higher HProk net growth rates and abundance under elevated UVR and lower values under warming conditions.
- 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.
- Water quality for bivalve molluscs and consumer safety: application of novel and adapted multimetric indices in a coastal lagoon system exposed to wastewater dischargesPublication . Cravo, Alexandra; Barbosa, Ana; BORLIDO OLIVEIRA LIMA, MARIA JOÃO; Ferreira, Cristina; Correia, Cátia; Matos, André Filipe; Jacob, José; Caetano, SandraWater quality degradation associated with wastewater discharges compromises the production of marine living resources. Water quality indices (WQIs) are relevant tools for water quality management, but most applications are limited to the suitability of freshwater for drinking. In this study, a novel WQI was developed to assess the effects of urban wastewater treatment plant (WWTP) discharges on the water quality in Ria Formosa coastal lagoon, targeting the condition of bivalve molluscs and consumer food safety (WQIB). The application of WQIB was compared with an adapted version of the Canadian Council of Ministers of the Environment Water Quality Index, using similar parameters (CCME-WQIB). WQIB and CCME-WQIB were applied to four areas next to WWTPs, over a 2-year period. WQIB integrated seven sub-indices (salinity, unionized ammonia, dissolved oxygen, suspended solids, chlorophyll-a, Escherichia coli and toxigenic phytoplankton), using a weighted additive aggregation function. Water quality ranged from very poor to very good and generally improved with distance from the effluent discharge points, and during the cold period. Highest influence of WWTP discharges was detected in areas under weak hydrodynamics. In areas under strong hydrodynamics, poor water quality was caused by the advection of toxigenic phytoplankton from adjacent coastal waters during the warm period. Although correlated, the use of WQIB should be preferred over CCME-WQIB due its greater sensitivity, use of weighted parameters and application at the sampling event scale. Our novel index extends the limited number of WQIs applied to marine systems and can be adapted to other systems and water use purposes.