J. Vitorino’s research while affiliated with Instituto Hidrográfico and other places

Chlorophyll-a satellite products are routinely used in oceanography, providing a synoptic and global view of phytoplankton abundance. However, these products lack information on the community structure of the phytoplankton, which is crucial for ecological modelling and ecosystem studies. To assess the usefulness of existing methods to differentiate phytoplankton functional types (PFT) or phytoplankton size classes from satellite data, in-situ phytoplankton samples collected in the Western Iberian coast, on the North-East Atlantic, were analysed for pigments and absorption spectra. Water samples were collected in five different locations, four of which were located near the shore and another in an open-ocean, seamount region. Three different modelling approaches for deriving phytoplankton size classes were applied to the in situ data. Approaches tested provide phytoplankton size class information based on the input of pigments data (Brewin et al., 2010), absorption spectra data (Ciotti et al., 2002) or both (Uitz et al., 2008). Following Uitz et al. (2008), results revealed high variability in microphytoplankton chlorophyll-specific absorption coefficients, ranging from 0.01 to 0.09 m2 (mg chl)− 1 between 400 and 500 nm. This spectral analysis suggested, in one of the regions, the existence of small cells (< 20 μm) in the fraction of phytoplankton presumed to be microphytoplankton (based on diagnostic pigments). Ciotti et al. (2002) approach yielded the highest differences between modelled and measured absorption spectra for the locations where samples had high variability in community structure and cell size. The Brewin et al. (2010) pigment-based model was adjusted and a set of model coefficients are presented and recommended for future studies in offshore water of the Western Iberian coast.

In the framework of the EUROSTRATAFORM project 108 bottom sediment samples (1st cm) from the Nazaré continental shelf have been analysed for grain-size, mineralogy (X-ray diffraction) organic carbon and carbonate contents. The particulate matter (PM) from intermediate (INL) and bottom nepheloid layers (BNL) was also analysed in 84 stations for grain-size and composition. The particle analysis was related to the present day sedimentary processes directly promoted (or intensified) by the presence of the Nazaré submarine canyon. The Nazaré canyon intersects the entire continental shelf and may act as a catchment area for material which is transported over the shelf, but its complex dynamics will extend to sediment distribution on the adjacent shelf. Major areas of erosion and resuspension and calmer areas where fine muddy sediments can settle on a temporary or permanent timescale were identified by their mineralogical and organic carbon (Corg) distribution pattern. According to this data the Victoria tributary and the Nazaré canyon head (280–300 m) seem to act as permanent depocenters. A conceptual model was proposed to delineate the mechanisms acting in this particular area, taking into account three different sources of material to the Nazaré canyon: 1. during upwelling conditions, resuspension of middle shelf deposits by internal wave activity and transport to the canyon in the BNL; 2.erosion of northern/southern beach and sea cliff materials transported by littoral drift to the canyon head and 3. fine sediment input from the southern river and transport to the canyon, during downwelling conditions (winter).

Two mooring lines equipped with near-bottom sediment traps were deployed in the axis of the Nazaré submarine canyon at ∼1600 and ∼3300 m depth, respectively. We studied time-series of particle flux, composition (biogenic silica, carbonates, organic matter and lithogenic fractions), granulometry, mineralogy and 210Pb concentration of particulate matter over five sediment trap deployments between October 2002 and December 2004. Current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow, temperature, salinity and suspended particle concentration. The composition of the collected particles was fairly constant year-round, dominated by the lithogenic fraction and with OC/N ratios in the range 11–21, suggesting an important terrigenous influence inside the canyon. The results show contrasting dynamic environments in the upper (1600 m depth) and middle (3300 m depth) canyon. High current speeds (spring tides up to 80 cm s−1) and high apparent mass fluxes of particulate matter (mean 65 g m−2 d−1; maximum 265 g m−2 d−1) are permanent at the shallowest station. At the deepest site, fluxes were below 10 g m−2 d−1 most of the time and the annual flux was governed by events of sharp flux increase. Storms affecting the continental shelf during autumn and winter are a major driver of down-canyon dispersal of sediments to the middle canyon and beyond. Important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m, as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth. On three occasions during the study period, significant wave heights of incident storms surpassed 7 m, leading to notable episodes of down-canyon transport that were clearly observed in the middle canyon. During one of these stormy periods (January 2003) a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m. However, a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon. The role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding.

The distribution and composition of phytoplankton assemblages were studied in the Nazaré submarine canyon, during an upwelling event, using high-performance liquid chromatography (HPLC) pigment analysis, complemented by microscopic qualitative observations. High chlorophyll a (Chl a) concentrations were recorded in the canyon head, near the coast, where values greater than 4μgL−1 were observed. In contrast, Chl a was relatively low in offshore regions, with values below 0.5μgL−1. The most abundant accessory pigments were fucoxanthin, peridinin, diadinoxanthin and 19′-hexanoyloxyfucoxanthin. Pigment data information was analyzed using the CHEMTAX software to estimate the contribution of different taxonomic groups to total Chl a. North of the canyon head, an area with high concentration of peridinin-containing dinoflagellates was identified (with presence of chain-forming toxic dinoflagellates). The presence of these organisms was associated with mixed water columns and phosphate values lower than the ones south of the canyon head, where a dominance of diatoms was recorded. The rest of the study region showed a dominance of prymnesiophytes and a significant contribution of cyanobacteria at oceanic stations. This study demonstrates the usefulness of using pigment analysis to study spatial distribution of phytoplankton groups in relation to a complex physical environment.

In 2002 the Portuguese hydrographic office Institute Hidrografico (IHPT) started a program of monitoring of the largest submarine canyon of the European margin: Nazare Canyon. Since it incises a rather sensible continental margin, characterized by the presence of a protected area for marine life (Berlengas marine reserve), the proximity of important routes for maritime traffic and the existence of traditional fishery centers, efforts was conducted to the maintenance of a mooring array equipped with currentmeters/ADCP, which was complemented with multidisciplinary surveys conducted on a regular basis. Here we describe the more recent experience in the monitoring of Nazare Canyon, through Project MONICAN (MONItoring of the Nazare CANyon area), financed by the EEA Grants mechanism. The monitoring system integrates an array of two multiparametric platforms, one coastal meteorological station and two coastal tide gauge stations, all providing real time data transmission. The array of multi-parametric platforms is the central component of this system. Public dissemination of the data collected by the monitoring system is a key aspect of the MONICAN project. The real-time data can be freely accessed through a dedicated web portal. Innovative experiences are being conduct to validate the recent installed systems and test the capability of performing regular observation of the Nazare Canyon area, using low cost sensors on non-dedicated surveys and ships of opportunity. Further developments to take place in the very near future will reinforce the monitoring capacity installed by IHPT in this area.

We describe the development of an operational forecast system for the NAzare Canyon area (W Portugal) which is presently being conducted at Instituto Hidrografico (IHPT). The system integrates a number of numerical models aimed to simulate and forecasts the wave conditions, the circulation promoted in the canyon area by wind forcing, interactions with the deep sea circulation or tides, and the littoral processes. The forecast system is planned to make an extensive use of the real-time observations collected by multi-parametric platforms maintained by IH in the Nazare Canyon area as part being developed sic guidelines for preparing papers for conference proceedings.