Distribution and ecological preferences of diatoms and dinoflagellates in the west Iberian Coastal zone (North Portugal)

The distribution of diatoms and dinoflagellates was studied from August 2002 to October 2003 in the northwest coastal zone of Portugal. Three sampling stations, perpendicular to the coast, were sampled monthly full moon, at high and low tide, near the shore, but before the surf zone. A total of 239 species were identified and quantified during the study period: 218 diatoms and 21 dinoflagellates. Although the phytoplankton community was dominated by marine diatoms, a proliferation of dinoflagellates was observed in late summer. Actinoptychus senarius, Grammatophora marina, Pseudo-nitzschia cf. seriata and Thalassionema nitzschioides were the most common diatoms at the three sampling stations. Canonical Correspondence Analysis (CCA) was used to identify the environmental variables governing the composition and structure of the phytoplankton assemblages and showed that the temporal variation in the species data was mainly determined by the temperature temporal gradient.