STUDY OF VIRIOPLANKTON ABUNDANCE AND MORPHOLOGICAL DIVERSITY IN A BRAZILIAN COASTAL REGION INFLUENCED BY UPWELLING SYSTEM

Marine viruses are among the most common, abundant and diverse biological entities in seawater columns. Despite this, little is yet know about virus abundance and distribution in tropical aquatic ecosystems. Here, we evaluated virus abundance and their relationship to host and environment variables within Arraial do Cabo upwelling system, Rio de Janeiro State, Southeast of Brazil. Seawater samples were collected in four seasonal campaigns from five sampling sites including different areas of human settlement characterized by anthropogenic activity (sewage disposal/port activity) and upwelling phenomena. Virioplankton abundance ranged from 0.79 to 7.95 x 108.part.mL-1, whereas bacterioplankton abundance ranged from 2.6 to 13.4 x 10 7 . cell. mL -1 . Viruses distribution was evaluated in relation to their possible hosts, and viral abundance positively correlated with both bacteria (r = 0.65; p < 0.01) and chlorophyll-a (r = 0.61; p < 0.01). Additionally, a method of concentration using adsorption/elution into electronegative membrane combined to electron microscopy, revealed the presence of bacteriophages, belonging to Myoviridae and Podoviridae families. Principal component analysis showed clear evidence that there is a seasonal influence between Arraial do Cabo biotic and abiotic variables, and that the high abundance of viruses was correlated mainly with nitrogen inorganic forms (NO2- and NO3-), PO43-, chlorophyll-a and bacteria. Thus, our study indicated that viral abundance in Arraial do Cabo coastal region depends on host cell abundance, which appears to be controlled mainly by nutrient availability.