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.
Uma série temporal de clorofila a e produção primária obtida em um período de 33 dias durante o verão na região de Ubatuba, sudeste do Brasil, foi submetida à análise multivariada e harmônica. A Análise de Componentes Principais revelou quatro fatores interpretados como (i) Água Central do Atlântico Sul; (ii) Sistemas ftontais transientes e chuvas; (iii) Ventos normais à costa; (iv) Ventos paralelos à costa. Estes fatores atuam como forçantes ambientais na determinação da variabilidade observada na biomassa fitoplanctônica e produtividade primária. A divisão da séríe temporal de acordo com quatro eventos modificadores das características fisicoquímicas da região mostrou a seguinte variabilidade na produção primária integrada (g C m,2 dia,l) na camada eufótica: coluna de água homogênea em processo de estratificação térmica- 0,4O±0, 11; coluna de água estratificada e chuvas intensas- 1,24±0,28; coluna de água misturada em fase de estratificação térmica após intensas chuvas- 0,74:f:0,10; coluna de água estratificada em fase de processo de mistura- 0,90±0,27; coluna de água homogênea em fase de estratifição térmica após intensa mistura- 0,63±0,28. A Análise Harmônica revelou dois picos de biomassa significativos- um com período de 8,25 dias e outro com período de 6,6 dias, contribuindo, res...

No abstract

Observations in the Brazil Current region between 20° and 30°S are revealing many interesting oceanographic features. In the austral winter of 1993, what appears to be an anomalous northward penetration of waters from the Brazil/Malvinas confluence region into the South Brazil Bight was observed (Figure 1).

The main aim of the present study was to evaluate and compare temporal responses of the benthos in 2 continental shelf areas (Cabo Frio and Ubatuba) off the SE Brazilian coast. In Cabo Frio (23°S, 42°W), the western boundary coastal upwelling of the South Atlantic Central Water (SACW) enhances primary productivity, potentially increasing food supply to the benthic communities via sinking of particulate organic carbon (POC). In contrast, POC fluxes in Ubatuba (23°S, 45°W) are expected to be comparatively lower because SACW remains subsurface. We analyzed the temporal and spatial input of phytodetritus (concentration of chlorophyll a in sediments) and the benthic microbial biomass (estimated by ATP-based carbon content in sediments). Median surface chlorophyll concentration was computed for all daily available SeaWiFS images (from 2001 and 2002) to follow chlorophyll a inputs. All parameters used to investigate benthic responses in the study areas showed consistently higher values in Cabo Frio than in Ubatuba. The results showed that benthic response to upwelling may last months, fueling the microbial communities in the Cabo Frio region.KEY WORDS: Benthic-pelagic coupling · Benthic microbial response · SE Brazilian continental shelf Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 291: [35][36][37][38][39][40][41][42] 2005 The present study is part of the DEPROAS (SW Atlantic Continental Shelf Ecosystem Dynamics) project, which aimed to investigate the influence of the cold and nutrient-rich South Atlantic Central Water (SACW) on the marine ecosystem. We compared the benthic responses in Cabo Frio, where there is a seasonal, Ekman-driven coastal upwelling of the SACW during the summer months (Miranda 1982, Matsuura 1986, with Ubatuba, where the SACW is found in summer at shallow subsurface depths (~10 m) (CastroFilho et al. 1987). This seasonal physical pattern in the South Brazilian Bight (SBB) seems to govern a marked biological productivity in the area.In Cabo Frio, phytoplankton biomass ranges from 5 to 12 mg chl a m -3 during the summer months (Gonzalez-Rodriguez 1991), with extreme reported levels reaching 25.5 mg chlorophyll a (chl a) m -3 (Moser & Gianesella-Galvão 1997). The latter levels are comparable to values from Antarctica (25 to 35 mg chl a m -3 ), where primary productivity is concentrated in only 1 period of the year (Karl et al. 1996). In Ubatuba, on the other hand, mean chlorophyll values are lower (0.67 to 2.77 mg chl a m -3 ), even though there is an enhancement of primary production during the summer months (Aidar et al. 1993).The increase in primary production seems to drive some important biological patterns of benthic inhabitants. Ventura et al. (1997) reported strong correlations between the gametogenic cycle of the sea-star Astropecten brasiliensis and the intrusion of SACW in Cabo Frio. These data highlight the influence of SACW in the SBB ecosystem, promoting the enhancement of biological production in the pelagic system (V...

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.