Using CHEMTAX to evaluate seasonal and interannual dynamics of the phytoplankton community off the South-west coast of Portugal

Abstract

a b s t r a c t CHEMTAX was used to assess the relative contribution of the main phytoplankton classes to the total concentration of Chlorophyll a (Chl a) from the waters off SW coast of Portugal. Sampling campaigns were carried out during all seasons from 2008 to 2012, at three stations located 2, 10 and 18 km from the coast. Samples were taken from the surface, mid-Secchi and Secchi depth, for the determination of Chl a and other phytoplanktonic pigments by HPLC. Supporting data were also obtained including dissolved inorganic nutrients, salinity, transparency, temperature and upwelling indices. The CHEMTAX results were also related to microscopy counts and also spectral analysis of absorption of other samples from the same sampling campaigns. The pigment results showed that diatoms dominated from early spring to summer, coinciding with upwelling conditions, while cryptophytes, prymnesiophytes and prasinophytes dominated in autumn and winter, coinciding with seasonal stratification. Although the contribution of cyanobacteria to total Chl a was generally low, there were occasional sampling campaigns where it was exceptionally high, but these appeared not to be related to upwelling. Dinoflagellates and chrysophytes were minority groups although the pigment marker peridinin that was used to distinguish dinoflagellates was not adequate for distinguishing all the members of this group. CHEMTAX was particularly useful for discriminating between the smaller (0e20 mm) classes of the microplankton that could not be easily identified by microscopy.

Implementing and Innovating Marine Monitoring Approaches for Assessing Marine Environmental Status

“…Often, the marker pigment used in CHEMTAX for dinoflagellates class is peridinin, which is only present in some of the auto-or mixotrophic species of dinoflagellates (Throndsen, 1997). This might lead to the underestimation in areas where most of the dinoflagellates are heterotrophic (e.g., Goela et al, 2014). In those cases, a more reliable CHEMTAX analysis would involve a careful examination of the typical pigment profiling of the local dinoflagellates community, namely the combinations between different diagnostic pigments, or the search for species specific diagnostic pigments (e.g., Örnólfsdóttir et al, 2003;Smith et al, 2010;Roy et al, 2011).…”

Technical note: Algal Pigment Index 2 in the Atlantic off the southwest Iberian Peninsula: standard and regional algorithms

“…TChl a concentration (monovinyl Chl a + divinyl Chl a + chlorophyllide a + phaeopigments) was determined by high-performance liquid chromatography (HPLC), according to Wright and Jeffrey (1997), herein referred to as TChl a REF HPLC . The protocols adopted for TChl a extraction, identification, and quantification procedures are reported in Goela et al (2014Goela et al ( , 2015.…”

MERIS Phytoplankton Time Series Products from the SW Iberian Peninsula (Sagres) Using Seasonal-Trend Decomposition Based on Loess

“…Generally, the upwelling filaments reach the area when the northerly winds promote upwelling along the west coast, with cold and nutrient upwelled waters flowing counter clockwise around the CSV, and eastwards along the southern coastal shelf [30][31][32]. These events occur mostly during early spring to late summer, and are known to enhance and stimulate biological productivity of these waters [25,26,29,31].…”

“…Three sampling Stations (A, B and C) are located along a north to south transect, perpendicular to the south coast of Sagres at distances of 2, 10, and 18 km offshore, with water depths of 40, 100, and 160 m [19,22], respectively. These Stations are well characterized as they have been used for MERIS validation activities [22][23][24][25][26]. Additionally, this area is an intercalibration site for the North-East Atlantic Ocean section of the WFD [27] that is part of the North-East Atlantic Ocean marine region and of the Bay of Biscay and Iberian Coast sub-region for the MSFD; and is partly located in the Southwest Alentejo and Vicente Coast Natural Park [19,28].…”