Environmental forcing on phytoplankton biomass and primary productivity of the coastal ecosystem in Ubatuba region, southern Brazil

Abstract

A time series of chlorophyll a and in situ primary production sampled over a period of 33 days during summer in Ubatuba region, southeastem Brazil, was subjected to multivariate and harmonic analysis. Principal Component Analysis has revealed four factors interpreted as (i) South Atlantic Central Water forcing; (ii) Transient ftontal systems and rain fali forcings; (iii) Wind forcing normal to the coast; (iv) Wind forcing parallel to the coast, as main factors in the variability of the phytoplankton biomass and primary productivity. Splitting of the time series according to four main events which had profound effects on the physicochemical characteristics of the region showed the following variations in the primary productivity integrated over the photic layer (g C m-2 day-1): mixing→stratification period, 0.40 ± 0.11; heavy rainfall, 1.24± 0.28; stratification after rainfall, 0.74± 0.10; stratification→mixing period, 0.90± 0.27; stratification after deep mixing, 0.63 ± 0.28. Harmonic analysis revealed two indistinguishable significant peaks of the phytoplankton biomass - one at a period of 8.25 days and one at a period of 6.6 days, contributing, respectively, about 17 and 32% ofthe total variance. Atmospheric forcing showed a characteristic period,of 200-264 hours while phytoplankton biomass response ranged over the 144-192 hours time scales and primary productivity was best related to the environment 360 hours before. Relative to total nitrogen' and ' biomass primary productivity oscillations were lagged about 96-144 hours. The interruption of steady-state conditions by transient atmospheric ev~nts and wind field intensification are the determining factors driving phytoplankton changes in this coastal environment.

Variação temporal do microfitoplâncton no Canal Estuarino de Santos (SP)

“…O predomínio de nanoflagelados na região costeira de São Paulo é um fato muito comum, como registrado por Aidar-Aragão & Teixeira (1980), Gaeta et al (1999), Gianesella et al (2000) e na revisão realizada por Schimiegelow et al (2008). As densidades observadas por esses autores são semelhantes àque-las obtidas nas duas campanhas amostrais realizadas nesse estudo.…”

Effects of coastal upwelling on the structure of macrofaunal communities in SE Brazil

“…The coastal water (CW) in Ubatuba has a salinity of 32-36 and temperatures of ≥ 25°C (Castro and Miranda, 1998). Since there are only few, small-sized rivers present in the coastal bays, the freshwater and nutrient run-off is minimal, resulting in meso-oligotrophic characteristics of the CW (Castro and Miranda, 1998;Gaeta et al, 1999). Nutrient concentrations (e.g.…”

“…nitrate, ammonium, phosphate) are low during most of the year and the phytoplankton is dominated by nanoflagellates (Aidar et al, 1993;Gaeta et al, 1999). In spring-summer, however, the upwelling of the cold and nutrient-rich SACW (salinity ≤ 36.4 and temperatures ≤ 20°C) to the euphotic zone and higher rainfall can drive sporadic blooms of opportunistic diatoms (Aidar et al, 1993;Castro-Filho et al, 1987;Gaeta et al, 1999). Sporadic nutrient enrichment of the water column may also occur during short-term sediment resuspension events, which are frequent during passage of cold fronts (i.e.…”

“…Furthermore, upwelling conditions during spring-summer are characterized by more stable environmental conditions, i.e. calm winds and hydrodynamics, compared to non-upwelling conditions in the rest of the year, when frequent passage of cold fronts causes stronger hydrodynamic forcing and sediment resuspension in the coastal zone (Gaeta et al, 1999;Mahiques et al, 1998).…”

Efeitos da acidificação dos oceanos nos processos biogeoquímicos em sedimentos costeiros: experimentos in situ e em laboratório

“…A regeneração de nutrientes prevalece durante todo o ano (Braga & Müller, 1998), enquanto que no verão, a intrusão em subsuperfície da massa de água ACAS, fria rica em nutrientes, pode causar esporádicos aumentos na produção nova, com florescimentos de diatomáceas em áreas internas da plataforma continental (Castro--Filho et al, 1987;Aidar et al, 1993;Gaeta et al, 1995;. No entanto, a produtividade primária local é dominada por espécies do nanoplâncton (Sassi & Kutner, 1992;Aidar et al, 1993;Gaeta et al, 1999 …”