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- Integrating in situ and ocean color data to evaluate ecological quality under the water framework directivePublication . Brito, Ana C.; Garrido-Amador, Paloma; Gameiro, Carla; Nogueira, Marta; Calixto De Jesus Moita Garnel, Maria Teresa; Cabrita, Maria TeresaTheWater Framework Directive (WFD) aims at evaluating the ecological status of European coastal water bodies (CWBs). This is a rather complex task and first requires the use of long-term databases to assess the e ect of anthropogenic pressure on biological communities. An in situ dataset was assembled using concomitant biological, i.e., chlorophyll a (Chl a) and environmental data, covering the years from 1995 to 2014, to enable a comprehensive assessment of eutrophication in the Western Iberia Coast (WIC). Given the temporal gaps in the dataset, especially in terms of Chl a, satellite observations were used to complement it. Positive relationships between Chl a 90th percentile and nitrogen concentrations were obtained. The Land-Uses Simplified Index (LUSI), as a pressure indicator, showed no relationship with Chl a, except in Galicia, but it highlighted a higher continental pressure in the Portuguese CWBs in comparison with Galician waters. In general terms, the trophic index (TRIX) showed that none of the CWBs were in degraded conditions. Nevertheless, the relatively high TRIX and LUSI values obtained for the water body in front of Tagus estuary suggest that this area should be subject to continued monitoring. Results highlighted the usefulness of satellite data in water quality assessments and set the background levels for the implementation of operational monitoring based on satellite Chl a. In the future, low uncertainty and harmonized satellite products across countries should be provided. Moreover, the assessment of satellite-based eutrophication indicators should also include metrics on phytoplankton phenology and community structure.
- Phytoplankton distribution and physical processes off NW Iberia during two consecutive upwelling seasonsPublication . Oliveira, P. B.; Amorim, F. N.; Dubert, J.; Nolasco, R.; Moita, TeresaThis work presents the results of two oceanographic surveys conducted off NW Iberia during successive summer upwelling seasons, aiming at the identification of the physical processes underlying the phytoplankton distribution in the area. Mooring (ADCP and thermistors) and ship-based CTD-F observations corroborate previous results that wind-driven upwelling circulation, (sub)mesoscale eddies and the stratification induced by the Western Iberia Buoyant Plume (WIBP) are the main processes affecting the chlorophyll distribution, but also provide new insights on key oceanographic structures governing the shelf circulation and phytoplankton structuring, namely (i) the link between frontal activity along the shelf break south of similar to 41 degrees N, the flow bifurcation at that latitude and the establishment of a cyclonic area with low frontal activity over the mid-shelf; (ii) the measurement of a previously unreported, remarkably persistent (> 1 month), near bottom poleward flow at the 30 m isobath, interpreted as the response to the alongshore pressure gradient driven by the stronger upwelling intensity north of 41 degrees N; (iii) the impact of low salinity buoyant plumes expressed on the shallowing of the Ekman layer, with the consequent frictional (Ekman) currents intensity increase, their low chlorophyll content contrary to previous winter/spring observations, and the lack of a direct relationship between plume salinities and river runoff; and (iv) the strong coupling between the chlorophyll distribution and the small-scale (O(1 - 10)km) oceanographic features providing further evidence that the phytoplankton distribution off NW Iberia in the summer upwelling season is strongly coupled to submesoscale processes.
- Phytoplankton communities in two wide-open bays in the Iberian upwelling systemPublication . Santos, Mariana; Moita, Maria Teresa; Oliveira, Paulo B.; Amorim, AnaThe main meteorological and oceanographic drivers shaping phytoplankton community structure and dynamics are investigated in two wide-open bays influenced by coastal upwelling. Local processes influencing the proliferation of harmful algal bloom species were also investigated. The work was developed during one year in Lisbon Bay (central-west coast) and in Lagos Bay (south coast), both located on the upwelling shadow of prominent headlands. In both bays, the results indicated a bi-modal annual pattern in phytoplankton biomass, and phytoplankton concentration maxima, between spring and late-summer, were associated with high diatom abundances. In Lagos Bay, higher dinoflagellate abundances were observed from spring to autumn, while in Lisbon Bay these were recorded from late-summer to autumn. The coccolithophores were a frequent group all year round in Lisbon Bay, which contrasts with Lagos Bay where they were the least frequent group. The phytoplankton community structure showed significant spatial and seasonal differences. The community succession pattern indicated the existence of four biological seasons in Lisbon Bay and at the offshore site in Lagos Bay. By contrast, the nearshore site in Lagos Bay was characterized by having no significant differences between summer and autumn. Differences in HAB species/groups were also observed between the bays. In general, HABs occurred at higher concentrations and were more persistent in Lagos Bay. In both bays, winter assemblages were influenced by water column mixing processes, although precipitation was also relevant in Lagos. Upwelling was a key driver of the spring phytoplankton community in Lagos Bay, while in Lisbon Bay other factors seemed to drive the spring phytoplankton assemblages. Both summer and autumn communities were related to thermal stratification. In autumn, the occurrence of reversal circulation patterns also played an important role in shaping the phytoplankton communities, especially in Lagos Bay. Overall, this study revealed differences on phytoplankton community patterns in two wide-open bays, shaped by the local environmental variables.
- Characterizing phytoplankton biomass seasonal cycles in two NE Atlantic coastal baysPublication . Santos, Mariana; Mouriño, Helena; Calixto De Jesus Moita Garnel, Maria Teresa; Silva, Alexandra; Amorim, Ana; Oliveira, Paulo B.The seasonal and interannual variability of chlorophyll a was studied between 2008 and 2016 in two coastal bays located in the northeastern limit of the Iberia/Canary upwelling ecosystem. The work aims (i) to understand if small latitudinal distances and/or coastline orientation can promote different chlorophyll a seasonal cycles; and (ii) to investigate if different meteorological and oceanographic variables can explain the differences observed on seasonal cycles. Results indicate three main biological seasons with different patterns in the two studied bays. A uni-modal pattern with a short early summer maximum and relatively low chlorophyll a concentration characterized the westernmost sector of the South coast, while a uni-modal pattern characterized by high biomass over a long period, slightly higher in spring than in summer, and high chlorophyll a concentration characterized the central West coast. Comparisons made between satellite estimates of chlorophyll a and in situ data in one of the bays revealed some important differences, namely the overestimation of concentrations and the anticipation of the beginning and end time of the productive period by satellite. Cross-correlation analyses were performed for phytoplankton biomass and different meteorological and oceanographic variables (SST, PAR, UI, MLD and precipitation) using different time lags to identify the drivers that promote the growth and the high levels of phytoplankton biomass. PAR contributed to the increase of phytoplankton biomass observed during winter/midspring, while upwelling and SST were the main explanatory drivers to the high Chl-a concentrations observed in late-spring/summer. Zonal transport was the variable that contributed most to the phytoplankton biomass during late-spring/summer in Lisbon Bay, while the meridional transport combined with SST was more important in Lagos Bay.
- Ocurrence of Ostreopsis in two temperate coastal bays (SW iberia): Insights from the planktonPublication . Santos, Mariana; Oliveira, Paulo B.; Calixto De Jesus Moita Garnel, Maria Teresa; David, Helena; Caeiro, Maria Filomena; Zingone, Adriana; Amorim, Ana; D. Silva, AlexandraThe benthic genus Ostreopsis contains toxic-bloom forming species and is an important cause of concern in warm-temperate and tropical waters. On the coast of Portugal, NE Atlantic, the occurrence of Ostreopsis cf. siamensis and Ostreopsis cf. ovata has been reported since 2008 and 2011, respectively. This work aims to understand the favorable conditions for high concentrations of Ostreopsis cells in the plankton at two sites, Lagos and Lisbon Bays, located in the South and West coast of Portugal, respectively. This study is based on weekly Ostreopsis abundance data in the plankton, from 2011 to 2017, daily satellite and in situ sea surface temperature (SST), and meteorological and sea state parameters, namely wind stress and significant wave height. The molecular identification of local Ostreopsis spp. is also presented. The maximum cell densities occur between late-summer and autumn. The distribution range of Ostreopsis cf. ovata is restricted to the South coast, while Ostreopsis cf. siamensis has a wider distribution range, being also present on the West coast. In the study period, there was only one occurrence of Ostreopsis spp., in Lagos Bay, with concentrations within the alert phase of monitoring. In Lagos Bay, high Ostreopsis spp. concentrations were related with positive SST anomalies. These high concentrations were often recorded after a period of almost 2-weeks to more than 4-weeks of low sea state ( < 0.6 m), followed by short time events of onshore wind and moderate waves (0.6-1 m). The former conditions are interpreted as favoring bloom development on the substrate and the latter as causing the re-suspension of Ostreopsis cells in the water column. In Lisbon Bay, O. cf. siamensis occurred in the plankton in few occasions and no clear relation could be established with the studied environmental variables. It is here hypothesized that the recent records of O. cf. siamensis in Lisbon Bay may correspond to an early colonization stage of an invasion process. Knowledge gained on Ostreopsis dynamics along the Portuguese coast can be used for both the improvement of benthic harmful algal blooms (BHABs) monitoring in the region and as a basis to design forecasting models.
- Mesoscale dynamics and niche segregation of two Dinophysis species in Galician-Portuguese coastal watersPublication . Díaz, Patricio; Reguera, Beatriz; Calixto De Jesus Moita Garnel, Maria Teresa; Bravo, Isabel; Ruiz-Villarreal, Manuel; Fraga, SantiagoBlooms of Dinophysis acuminata occur every year in Galicia (northwest Spain), between spring and autumn. These blooms contaminate shellfish with lipophilic toxins and cause lengthy harvesting bans. They are often followed by short-lived blooms of Dinophysis acuta, associated with northward longshore transport, at the end of the upwelling season. During the summers of 1989 and 1990, dense blooms of D. acuta developed in situ, initially co-occurring with D.acuminata and later with the paralytic shellfish toxin-producer Gymnodiniumcatenatum. Unexplored data from three cruises carried out before, during, and following autumn blooms (13⁻14, 27⁻28 September and 11⁻12 October) in 1990 showed D. acuta distribution in shelf waters within the 50 m and 130 m isobaths, delimited by the upwelling front. A joint review of monitoring data from Galicia and Portugal provided a mesoscale view of anomalies in SST and other hydroclimatic factors associated with a northward displacement of the center of gravity of D. acuta populations. At the microscale, re-examination of the vertical segregation of cell maxima in the light of current knowledge, improved our understanding of niche differentiation between the two species of Dinophysis. Results here improve local transport models and forecast of Dinophysis events, the main cause of shellfish harvesting bans in the most important mussel production area in Europe.