Temporal and spatial variation of Ulva spp. and water properties in the Cabo Frio upwelling region of Brazil

Abstract

Three sites in the Cabo Frio upwelling region were studied to characterize the spatial and temporal variation of environmental factors and Ulva spp. percent cover. The sites during upwelling events showed lower water temperature values and higher nutrient concentration (inorganic nitrogen and temperature around 10 μg-at l −1 and 15°C, respectively) than in the non-upwelling period (inorganic nitrogen and temperature around 4 μg-at l −1 and 22°C, respectively). There was a negative correlation between algal cover and temperature and a positive correlation between algal cover and nutrients at sites affected by upwelling waters. The correlation coefficient between Ulva cover and temperature was lower at the main upwelling site (−0.54) then at the area affected by advected waters (−0.88). The highest Ulva percent cover average was calculated for the site affected by advected upwelling waters and estuarine waters not for the main upwelling site. The horizontal geographic variation of Ulva spp. cover suggested that there was a spatial gradient in algal percent cover correlated to upwelling influence at Cabo Frio shores.