The influence of surface low-salinity waters and cold subsurface water masses on picoplankton and ultraplankton distribution in the continental shelf off Rio de Janeiro, SE Brazil

• Published in: Continental shelf research Vol. 120; pp. 82 - 95
• Main Authors: Moser, G.A.O, Castro, N.O, Takanohashi, R.A, Fernandes, A.M, Pollery, R.C.G, Tenenbaum, D.R, Varela-Guerra, J, Barrera-Alba, J.J, Ciotti, A.M
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2016
• Subjects: Autotrophs; Bacterioplankton; Brackish; Chlorophylls; Coastal; Communities; Continental shelves; Dome; Freshwater; Guanabara bay; Light levels; Mouth; Nutrients; River plumes; Ubatuba bay; ASW, Brazil, Rio de Janeiro; ASW, Brazil, Sao Paulo, Sao Sebastiao; ASW, Brazil, Rio de Janeiro, Sepetiba Bay; PSW, South Atlantic, South Atlantic Central Water; ASW, Brazil, Rio de Janeiro, Guanabara Bay; TW; Dome; SACW; SW; Guanabara bay; DIN; ADCP; DCM; CTD; Bacterioplankton; Ubatuba bay; CW; River plumes; RJ; Nutrients; SP; HPLC
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/j.csr.2016.02.017

The smallest phytoplankton groups named picoplankton and ultraplankton can be responsible for about 50–80% of the primary production rates in oligotrophic waters, due to their high surface/volume ratios that enables them for competitive growth rates relative to bigger cells under low light and low nutrient availability. The role of picoplankton and ultraplankton in coastal dynamic regions is less clear. This work relates the spatial distribution of autotrophic and heterotrophic components of these communities to the different properties of the water masses in the Southeastern Brazilian Continental Shelf, generally considered oligotrophic. Picoplankton and ultraplankton communities were related to nutrients present in the subsurface South Atlantic Central Water and waters with salinities below 35.5 originated from different estuarine systems. The enhance of autotrophs were also associated with a near shore feature related to topographic effects of São Sebastião Island to the local currents, first reported in this article. A core of higher chlorophyll a concentration, associated with the northeastward current flow at approximately 21m depth below the surface, was identified as a dome-like shape. This core dissipated in the subsequent days suggesting that the flow towards NE was no longer a permanent feature two days after its observation. Locally enhancement of the contribution of picoplanktonic and ultraplanktonic autotrophs was observed in the surface and at the deep chlorophyll maximum depth associated with the chlorophyll core. Heterotrophs were more abundant inside and at the mouth of Guanabara Bay as well as inside Sepetiba Bay where light levels were low. [Display omitted] •Picoplankton and ultraplankton spatial distribution.•Mesoscale eddy associated with a SACW dome in subsurface waters.•Influences of coastal bay plumes on the abundance of planktonic organisms.