CARACTERISTCS AND IMPORTANCE OF PLANKTONIC FLAGELLATES IN MARINE COASTAL AND OCEANIC ECOSYSTEMS

Abstract

Marine flagellates are morphologically and physiologically diverse planktonic organisms including several taxonomic Divisions of the Kingdom Protoctista. The ecological importance of flagellates comes from their diverse metabolic capacity, smal1 size and motility, thus having great competitive advantage in environments with low but continued nutrient inputs. The knowledge of this group has improved over the last 25 years due te development of new techniques and increasing interest; however there is a consensus that the number of undescribed species stil1 exceeds the number of known ones. Difficulties in flagellate studies concerned with their small size, delicate nature of cell covering, shrinking or deformation of preserved cells thus requiring examination of alive cells for cell size, shape, and motility observation. The reliable identification of many species depends on submicroscopic details, requiring electronic microscope thecniques; the complexity of their life cycles also impose difficulties.  Marine flagellates in Brazilian coastal and oceanic waters are poorly known, with few studies conducted up to the present, there we present a review of existing data on the occurrence of flagel1ates over the Brazilian coast. Most reported flagel1ate species are calcified coccolithoforids (>60%) and the remaining groups are Chlorophyceae, Prasinophyccac, Chrysophyccae, Raphidophyceae, Cryptophyta, Euglenophyta and Haptophyta, Flagellatcs (10⁵ and 10⁶cells l^-1) are the predominant organisms in oceanic waters, but also in inshore areas like Lagoa dos Patos estuary, they are relatively more important than microplankton during the year, contributing with 70% of chlorophyll a and particulate primary production. Potentially harmful flagel1ates have been recorded in different sites on the Brazilian coast suggesting that they are widely spread and represent a potential risk to the coastal environment.