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The western Tropical Atlantic Ocean is a biogeochemically complex region due to the structure of the surface current system and the large freshwater input from the Amazon River coupled with the dynamics of precipitation. Such features make it difficult to understand the dynamics of the carbon cycle, leading to contrasting estimates in sea-air CO2 exchanges in this region. Here we demonstrate that these contrasting estimates occur because the western Tropical Atlantic Ocean can be split in three distinct regions regarding the sea-air CO2 exchanges. The region under the North Brazil Current domain, acting as a weak annual CO2 source to the atmosphere, with low interannual variability. The region under the North Equatorial Current influence, acting as an annual CO2 sink zone, with great temporal variability. The third region is under the Amazon River plume influence, and has greater interannual variability of CO2 exchanges, but it always acts as an ocean CO2 net sink. Despite this large spatial variability, the entire region acts as a net annual CO2 sink of –1.6 ± 1.0 mmol m–2 day–1. Importantly, the Amazon River plume waters drive 87% of the CO2 uptake in the western Tropical Atlantic Ocean. In addition, we found a significant increase trend in sea surface CO2 partial pressure in North Brazil Current and North Equatorial Current waters. Such trends are greater than the increase in atmospheric CO2 partial pressure, revealing the sensitivity of carbon dynamics in these regions against a global climate change scenario. Since several studies have put efforts to elucidate the snapshots sea-air CO2 exchanges, we have expanded our knowledge about their spatial and temporal dynamics. Our findings shed a comprehensive light on the risk of extrapolation in estimating sea-air CO2 exchanges from regional snapshots. Hence, in addition to pointing out questions that still need to be answered on the CO2-carbonate system our study may be useful for the sampling design of future studies in this region. This should significantly improve the performance of complex coupled ocean-biogeochemical models to provide more robust information about the natural behaviour and changes that the western Tropical Atlantic Ocean is experiencing.

We investigated the primary drivers of changes in the partial pressure of carbon dioxide (pCO2) together with the seasonal and interannual variability in the water-air net carbon dioxide flux (FCO2) in the lower estuarine zone surface waters of Patos Lagoon, the largest choked lagoon worldwide. Sampling occurred monthly during May 2017-June 2021 at the estuary’s inner inlet and mouth, which are contrasting hydrodynamic zones in the Patos Lagoon Estuary (PLE). The water pCO2 was mainly controlled by seasonal changes in total alkalinity and total dissolved inorganic carbon. The lower zone experienced periods of CO2 ingassing (austral summer/autumn) and CO2 outgassing (austral winter/spring). During summer/autumn, both protected and sea-exposed areas uptake an average of –15 mmol m−2 d−1 CO2, whereas during winter/spring, CO2 emissions prevail, reaching an average of 22 mmol m−2 d−1 at the inner estuary. Additionally, while much of the CO2 absorbed in summer/autumn is released to the atmosphere in the inner estuarine zone, the summer/autumn CO2 uptake in the estuary mouth is 4-fold higher than the winter/spring CO2 released. Unlike most estuarine systems, the PLE acted as a net CO2 sink of –2 mmol m−2 d−1 during the period investigated. The balance between CO2 uptake and emissions in the PLE was modulated by the combination of wind speed, freshwater discharge, water temperature, and outflow/inflow currents. Furthermore, phytoplankton blooms and strong wind-induced vertical mixing lead to highly variable CO2 exchanges. The highest estuarine CO2 concentration by autochthonous production indicates heterotrophy in estuarine waters. Part of this carbon produced in the estuary is exported to the coast, as evidenced by the high CO2 concentration in the estuary mouth. Therefore, the lower estuarine zone resists increased CO2 concentrations and has overcome regional anthropogenic emissions. The regional FCO2 range and complex PLE biogeochemistry dynamics need ongoing investigation to improve knowledge of regional CO2 exchanges and elucidate the role of large estuaries and coastal bays in the global carbon budget.

Total phosphorus (TP) records reflect variations in input and burial of organic matter (OM) in coastal and shelf sediments . At Antarctic regions , TP levels are often derived from natural sources; however, with emergent human pressure at these regions, anthropogenic sources of TP may play an important role. At the Antarctic Peninsula , Admiralty Bay attracts great scientific and touristic interest, especially during austral summer months, thus being vulnerable to human activities. Currently, only scarce spatial distributions of TP are available for this key region, whereas no vertical distributions have been determined. To fill this gap, we investigated short ( sediment cores in ten areas along Admiralty Bay for TP contents. We produced the first TP vertical distributions and established site-specific background values (from 492 ± 13 to 932 ± 17 μg g −1 ), which are related to hydrodynamics, sedimentology , and natural inputs of P. We observed a gradual surface TP enrichment at all sites, mainly due to input of fresh OM. Benefiting from our background values, we employ the Phosphorus Pollution Index (PPI) to assess possible human impacts . Generally, the increase of PPI suggests natural inputs of P. However, PPI ≥ 1.3 found at the nearby Comandante Ferraz Research Station (Brazil) can be linked to recent (past 2–3 decades) treated sewage inputs in Martel Inlet. We suggest PPI as a proxy for preliminary assessments of anthropogenic impacts in coastal Antarctic regions experiencing increased human pressure.

The Paranaguá Estuarine Complex (PEC) includes the naturally oligotrophic (NO) Mel Island which is surrounded by sea grasses, a naturally eutrophic (NE) Benito Inlet adjacent to mangrove wetlands and the highly impacted eutrophic (IE) Paranaguá Bay, home of one of Brazil's largest ports. The results from this study indicate that reactive As and pyrite increase with sediment depth near Paranaguá port in the IE region. At the NE region, near a mangrove fringe, the reactive As, Fe, Mn and pyrite remained relatively high along the sediment column while near the sea grasses at NO the As contents were low. The degree of trace metal pyritization (DTMP) and the degree of pyritization (DOP) was highest at the IE site, slightly increasing with depth. These baseline results indicate that influence of trophic conditions and presence of marine vegetation may be directly related to As behavior in coastal systems.

In order to assess the effects of Fe-enrichment on the growth and domoic acid (DA) production of the toxigenic diatom Pseudo-nitzschia multiseries, static cultures that received the addition of different iron (Fe) concentrations were maintained for 30 days. Intra- and extracellular DA concentrations were evaluated over time, and growth and chain-formation were compared to those of non-toxic diatoms, Bacillaria sp. Growth rates of P. multiseries (μ = 0.45–0.73 d−1) were similar among cultures containing different Fe concentrations. Likewise, the similar incidence and length of P. multiseries stepped cell chains (usually 2–4; up to 8-cell long) among the treatments reinforces that the cultures were not growth-inhibited under any condition tested, suggesting an efficient Fe acquisition mechanism. Moreover, DA concentrations were significantly higher under the highest Fe concentration, indicating that Fe is required for toxin synthesis. Bacillaria sp. reached comparable growth rates under the same Fe concentrations, except when the dissolved cell contents from a P. multiseries culture was added. The 50–70% reduction in cell density and 70–90% decrease in total chlorophyll-a content of Bacillaria sp. at early stationary growth phase indicates, for the first time, an allelopathic effect of undetermined compounds released by Pseudo-nitzschia to another diatom species.

Levels of trace elements were investigated in feathers of 51 adults and 47 eggshells of brown boobies Sula leucogaster from one bird colony in the Marine National Park of Currais Islands, Brazil, between December 2013 and October 2014. Average concentrations (μg g−1, dry weight) in feathers and eggshells, respectively, were Al 50.62–9.58, As 0.35–2.37, Cd 0.05–0.03, Co 0.38–2.1, Cu 15.12–0.99, Fe 47.47–22.92, Mg 815.71–1116.92, Ni 0.29–11.85, and Zn 94.16–1.98. In both arrays, the average concentration of Mg was the highest among all the elements analyzed, while the lowest was recorded for Cd. As and Ni presented levels at which biological impacts might occur. Zn concentrations were higher than those considered normal in other organs. Levels of Al, Fe, Cu, Zn, and Cd were higher in feathers, whereas higher contents of Mg, Co, Ni, and As occurred in eggshells. The comparison between the elements in eggshells collected at different seasons showed no significant difference (p > 0.05) due, probably, to the lack of temporal variation on foraging behavior and/or on bioavailability of trace elements. Metals and arsenic in feathers and eggshells were mostly not correlated. Future studies on Parana coast should focus on the speciation of the elements, especially As, Ni, and Zn, which proved to be a possible problem for the environment and biota. It is necessary to investigate both matrices, shell and internal contents of the eggs, in order to verify if the differences previously reported in other studies also occur in eggs of brown boobies in the Marine National Park of Currais Islands.

Particulate and dissolved metal concentrations were determined after the largest flood in the last 30 years on the east-west axis of the Paranaguá Estuarine Complex (PEC) and compared to the those of the dry period at two stations. Results confirmed that the flood greatly affected riverine outflows and the behavior of metals in the PEC. In particular, a sharp decrease in salinity was followed by extremely high SPM concentrations leading to a decrease in DO concentrations at both stations. For the dissolved phase, ANOSIM analysis showed a significant dissimilarity at each station between the sampled periods, whereas for the particulate phase this dissimilarity was found only for the samplings taken at the Antonina Station. KD values suggested dissolved Cu behavior was related to the presence of organic complexes and dissolved Mn had sediment resuspension of redox sediments and or/pore water injection as sources. Metal concentrations were lower than in polluted estuaries, though high enrichment factors found after the flood pointed to the influence of anthropogenic sources. In conclusion, the flood's influence was more evident at the Antonina Station, due to its location in the upper estuary, whereas in Paranaguá a high SPM content with low metal concentration was found, following the common pattern generally found in other marine systems subject to heavy rainfall events. Resumo Com o objetivo de avaliar a influência do maior evento de enchente dos últimos 30 anos no Complexo Estuarino de Paranaguá (CEP), ocorrido em 2010, concentrações de metais na fase particulada e dissolvida foram medidas em duas estações amostrais, e comparadas ao período seco. Os resultados confirmaram a influência desse evento no aumento do fluxo dos rios e no comportamento dos metais no CEP. Uma acentuada diminuição na salinidade, concomitante ao aumento de material particulado em suspensão, gerou a diminuição das concentrações de oxigênio dissolvido nas duas estações amostradas. A análise de ANOSIM indicou ausência de similaridade entre ambas as estações e períodos amostrados, enquanto que para a fase particulada essa diferença foi evidente apenas para a estação de Antonina. Os valores do coeficiente de partição (KD) sugeriram um input de manganês dissolvido por meio de processos de oxi-redução. As concentrações de metais registradas foram menores do que as encontradas em estuários poluídos; no entanto, o aumento do Fator de Enriquecimento após o evento de inundação sugeriu a influência de fontes antrópicas. Como conclusão geral, a influência do evento de inundação foi mais evidente na estação de Antonina, principalmente devido a sua localização na parte superior do estuário, enquanto que em Paranaguá o aumento do SPM foi acompanhado de uma diminuição na concentração de metais, seguindo o comportamento de metais registrados em outros estuários após eventos de inundação.

This study addresses the distribution of total phosphorus (TP) and its inorganic (IP) and organic (OP) fractions, grain-size and organic matter of surface and recent sediments, coupled to the behavior of total and dissolved inorganic phosphorus (TP and DIP) of the water column, of the semi-pristine Guaratuba Bay estuary, SE Brazil. Surface sediment samples were taken at 43 sites spread along the estuarine gradient and recent sediments from 3 short (35 cm long) cores from the upper, central and lower portions of the estuary, respectively. Highest TP and IP concentrations of surface sediments were detected within the upper sector and the transition zone between the upper and central sectors, all characterized by fine sediments, low salinities and water depths. In contrast, the lower sector and its narrow and deep tidal channel, subject to more intense tidal forcing, exhibited a higher fraction of sandy sediments with lower TP, IP and OP contents. In spite of the spatial variability in sediment grain size, IP corresponded to the major fraction of TP in all estuarine sectors and both TP and IP correlated significantly with the fine sedimentary (silt + clay) grain-size fraction. The fine surface sediments acted as a trap for IP at the fresh water–low salinity interface, which also corresponded to the region of a DIP sink in surface waters. In general, the short sediment cores showed that TP and IP contents increased from 15 cm depths to the top layer. Published sedimentation rates from additional cores taken at the sites of the short cores of this study, implied that depositional alterations of TP and IP increased during the early 1970s, which corresponded to the onset of anthropogenic disturbances from crop plantations in the lowland plains of the river end-member and urbanization at the estuary’s mouth and along the adjacent coast.

Mangrove sediment cores sampled from Sepetiba Bay (SE Brazil) were covered with tidal water spiked with 75Se, 51Cr and 60Co to evaluate the removal efficiency of these radiotracers by underlying sediments. Variable time-evolution trends were observed along 115 h experiments, with significant differences between removal efficiencies of all radiotracers observed only after 70 h (51Cr > 60Co > 75Se). After an event of 60Co release back to overlying water, there was a general trend of lower 60Co removal than observed for other radiotracers during the period from 20 to 54 h. After this event, alternated periods of higher 60Co and higher 75Se removal trends were observed, attributed to behavioural differences expected for such anionic and cationic radiotracers. While 75Se and 51Cr showed uniform time-evolution curves, as typically found in the literature for most radiotracers, 60Co removal rates presented oscillations, probably due to sensitivity to changes in redox conditions within underlying sediments. Results evidenced the role of mangrove sediments as trace element sinks, which have implications for coastal water quality and for possible uses of such sediments in wastewater treatment systems.

Sediments from Guaratuba Bay (PR, Brazil), a marine protected area, were collected and evaluated for geochemistry and toxicity. High levels of P and acute toxicity were observed in some samples. Concentrations of Cu, Cd, Pb and Zn were relatively low; however, Cd levels eventually exceeded Threshold Effect Level. Toxicities were associated to nutrients and metals enrichment. Results suggest that impacts are incipient and occur only at specific sites, associated to multiple contamination sources. Despite sediments quality seems to range between good and fair, attention is required to land-use planning around Guaratuba Bay and controlling local pollution sources.

Potential influences of the whole benthic organisms' activity (i.e., coupled faunal and microbial effects) on 58Co, 51Cr and 65Zn diffusion into surface mangrove sediment layers (0–6 cm depth) were evaluated in 36 h experiments. Benthic activity indices (BAI) were proposed, calculated as the relative percent difference between untreated sediments and formaldehyde-treated sediments data in relation to untreated sediments data. Benthic activity was estimated as responsible for 32%–44% of total inventories within sediments, being the chromate anion spiked the less affected radiotracer, while 65Zn was the most sensitive. Benthic activity was quantitatively evidenced as a control on trace metal diffusion into the sediments, contributing to determine the sediment role as a metal sink. This influence can also affect metal potential bioavailability, considering that recently diffused metals can be more readily available to biological uptake.

This work investigates the (223)Ra, (224)Ra, (226)Ra and (228)Ra isotope distribution in river, estuarine waters and sediments of the Paranagua Estuarine Complex (PEC). The stratification of the Ra isotopes along water columns indicate differing natural sources. In sediments, the radium isotope activities was inversely proportional to the particle size. The highest concentrations of (223)Ra, (224)Ra, (226)Ra and (228)Ra in the water column were found in the bottom more saline waters and towards the inner of the estuary. These relatively high concentrations towards the bottom of the estuary may be attributed to the influence of tidally driven groundwater source and desorption from particles at the maximum turbidity zone. The apparent river water ages from the radium isotope ratios, (223)Ra/(224)Ra and (223)Ra/(228)Ra, indicate that the principal rivers that flow into the estuary have residence times from between 6 and 11days.

The atmospheric deposition of dissolved trace elements was investigated in two subtropical estuarine systems, located on the coast of Parana, Southeast Brazil. The samples (n = 91) were collected in three periods, from May to September 2010, in four different areas. Trace elements concentrations (Al, Fe, Zn, Mn, Ba, Ca, Mo, V, As, Cu, Co, Ni, Cr and Pb) were determined for dissolved fraction using inductively coupled plasma-mass spectrometry (ICP-MS). pH measurements revealed the occurrence of a slightly acidic precipitation in the investigated points. Among the trace elements, Zn was the most abundant, followed by Al, Fe, Mn, Cu, Ba and V. The analysis of the enrichment factors enabled the identification of the different sources of the analysed elements. The origin of the Al and Fe elements were entirely continental, whereas Zn was primarily associated with human activities. Thus, the atmospheric deposition may be a primary route of exposure to anthropogenic Zn for estuarine biota.

Temporal variability of physicochemical parameters and phytoplankton primary productivity, abundance and composition were investigated at Babitonga Bay, southern Brazil, using a hierarchical sampling design on the scales of months, weeks and days during spring 2012 and summer 2013. Only temperature, respiration rates and concentrations of dissolved oxygen and silicate exhibited significant differences in the greatest timescale (seasons: spring; summer). In contrast, most physicochemical parameters, such as salinity and the concentration of nitrogen compounds, varied mainly among weeks and days. This short-scale variability was similarly observed for the microphytoplankton abundance, ranging from 0.04 to 1.7.106 cells L–1 during a bloom of the diatom Skeletonema costatum. Two major phytoplankton assemblages were associated with high primary production rates: > 30 μm centric diatoms such as Cyclotella spp. and Cymatodiscus sp., in spring; and a summer assemblage dominated by smaller, bloom-forming diatoms (S. costatum and Eucampia cornuta). Primary production ranged from 10.5 to 1793 mg C m–2 d–1 and varied significantly between days and months, being associated with the photosynthetic active radiation level and weather conditions on the sampling day. Abundance of specific plankton taxa appeared controlled by trophic interactions, as revealed for the mixotrophic, toxic dinoflagellate Dinophysis acuminata complex and its prey, the ciliate Mesodinium rubrum. Se investigaron la variabilidad temporal de los parámetros físico-químicos y la producción primaria (PP), abundancia y composición del fitoplancton en la Bahía de Babitonga, sur de Brasil, utilizando un diseño de muestreo jerárquico en las escalas de meses, semanas y días, durante la primavera/2012 y verano/2013. Sólo la temperatura, las tasas de respiración y las concentraciones de oxígeno disuelto y silicato mostraron diferencias significativas en las escalas de tiempo mayores (estaciones: primavera; verano). En contraste, la mayoría de los parámetros fisicoquímicos, tales como la salinidad y la concentración de compuestos de nitrógeno, varió principalmente entre semana y días. Tal variabilidad de corta escala se observó de manera similar para la abundancia de microfitoplancton, oscilando desde 0,04 a 1.7.106 céls. L–1 durante una floración de la diatomea Skeletonema costatum. Se asociaron dos importantes grupos de fitoplancton con altas tasas de PP: diatomeas céntricas > 30 μm como Cyclotella spp. y Cymatodiscus sp., en primavera; y un grupo de verano dominado por pequeñas diatomeas formadoras de floraciones (S. costatum y Eucampia cornuta). La PP varió de 10.5 a 1793 mg C m–2 d–1 y varió significativamente entre días y meses, siendo asociada con el nivel de radiación fotosintética activa y las condiciones meteorológicas en el día de muestreo. La abundancia de taxa específicos de plancton parece controlada por interacciones tróficas, como las revelada para el dinoflagelado tóxico mixotrófico, complejo Dinophysis acuminata y su presa, el ciliado Mesodinium rubrum.

The present study focuses on the nutrient sources and gradients in Paranagua Bay (Southern Brazil), where nutrient inputs are related to losses from fertilizer loading in Paranagua harbour and the discharge of untreated waste water. The input of dissolved inorganic nutrients to the bay from the harbour and city, as well as from river and atmospheric deposition, amounted to 642 t year−1 DIN-N and 92 t year−1 PO4-P. Harbour losses accounted for 6 % of total DIN-N and 39 % of total PO4-P loads to the bay, whereas sewage inputs from the city were responsible for 21 % and 22 %, respectively. River inputs made up 68 % of DIN-N, mainly in the form of nitrate, and 35 % of PO4-P loads, while atmospheric wet deposition was estimated to be in the order of 5 % of DIN-N and 4 % of PO4-P loads. Local maxima in nutrient levels deriving from highly concentrated sewage discharge were observed in front of the harbour and city of Paranagua, but the plumes are diluted rapidly due to short residence times. DIN concentrations are negatively correlated with salinity, indicating the importance of freshwater input as a main factor controlling nitrogen distribution. Elevated phosphate levels in the stratified middle section of the bay may result both from harbour emissions and phosphate remobilization from sediments. Generally lower DIN and PO4 concentrations during the warmer rainy season are supposed to be due to intensified assimilation rates especially in the middle section of the bay where dense phytoplankton blooms are observed. The bay as a whole cannot be classified as being seriously eutrophic, albeit eutrophication symptoms prevail in some restricted locations in front of Paranagua harbour.

An environmental assessment of the estuarine waters of Guaratuba bay, Paraná State, Brazil, is provided through the analysis of physical-chemical, biological and hydrographic dynamics. Twelve stations with a bi-monthly frequency (from October/2002 until August/2003) were sampled during spring and neap tides for the determination of pH, Secchi depth, CO2 saturation, dissolved oxygen, chlorophyll, suspended particulate matter and dissolved inorganic nutrients (nitrate, nitrite, ammonium, phosphate and silicate). Based on the evaluation of six parameters (chlorophyll, Secchi depth, CO2 saturation, dissolved inorganic nitrogen and phosphorus and dissolved oxygen), Guaratuba Bay shows a low to medium trophic status, i.e. from meso- to oligotrophic, and a predominant heterotrophic metabolism, meaning that respiration overcomes primary production. Horizontal stratification was observed during the rainy season, while during the dry season the system showed more homogeneous conditions. Inorganic and/or organic matter in Guaratuba Bay seem to be controlled mainly by the seasonality of precipitation and/ also by ebb and flood tidal phase variations.A dinâmica das variáveis físico-químicas, biológicas e hidrográficas, em escalas temporal e espacial, sua variabilidade e tendências, permite avaliar a qualidade ambiental de estuários. Esse trabalho descreve as flutuações da qualidade de água da Baía de Guaratuba, sul do Estado do Paraná. Foram amostrados doze pontos em campanhas bimensais (outubro/2002 a agosto/2003), em situação de sizígia e de quadratura, para a análise das variáveis pH, transparência, saturação de CO2, oxigênio dissolvido, clorofila-a, material particulado em suspensão e nutrientes inorgânicos dissolvidos (nitrato, nitrito, amônio, fosfato e silicato). Considerando as seis variáveis descritoras da qualidade de água (clorofila-a, profundidade de Secchi, saturação de CO2, fósforo e nitrogênio inorgânicos dissolvidos e oxigênio dissolvido), observou-se que a Baía apresentou estado trófico médio para baixo, i.e. de meso para oligotrófico, e que o seu metabolismo é predominantemente heterotrófico, ou seja, os processos de respiração superam os de produção. Foi verificada uma maior estratificação horizontal durante o período chuvoso e características relativamente mais homogêneas durante a estação mais seca. A qualidade da água na baía de Guaratuba parece ser controlada mais pelos aportes de material inorgânico e/ou orgânico associados a pluviosidade e/ou por variações com as fases de maré vazante e enchente.

Microcosm experiments on the behaviour of Se, Cr and Co were carried out with mangrove sediments from Sepetiba Bay, Brazil. Three 8-cm length sediment cores were covered with tidal water spiked with 75Se, 51Cr and 60Co to evaluate its behaviour within the sediments. Two cores retained almost all activities (99–100 %) within the uppermost centimetre layer, while the third core presented a deeper penetration of all radiotracers, displaying a second activity peak at the 3–4-cm depth interval, which evidenced benthic fauna bioturbation influence. This influence extended the diffusion into depths in which mangrove rhizosphere can retain the elements, suggesting increased retention efficiency. This mechanism of retention enhancement was proposed in addition to previous conceptual models describing trace elements behaviour in mangrove sediments. Increased bioturbation and rhizosphere development will probably increase this effect, while mangrove plant cover losses may promote a less efficient retention of elements recently diffused from tidal water.

The behavior and dynamics of arsenic at Ilha do Mel, Guaraquecaba, and Paranagua, located in the Paranagua Estuarine Complex, Brazil, were investigated in this work. Samples were collected in March, September, and December of 2005. With respect to arsenic behavior, the total concentrations were higher for Paranagua (22.5 ± 2.5 μg L−1) on average, followed by the samples of Guaraquecaba (14.4 ± 3.2 μg L−1) and Ilha do Mel (8.7 ± 1.1 μg L−1). The concentrations found in this work were consistently greater when compared to other estuaries. The results can be attributed to geological factors. Nevertheless, it was also possible to realize that higher concentrations were found in Paranagua, the more impacted environment. These results represent a strong indication that human activities in the area contribute to the enrichment of the estuary with this metalloid. Arsenic was mainly present in the dissolved phase, which corresponded to more than 70% of the total concentration. This behavior can represent a greater residence time of this metalloid in the water column. The marine phytoplankton presence was decisive in dictating the distribution of As in the waters of Paranagua estuary. Organic species, which are considered the less toxic, were found in higher concentrations in the eutrophic areas such as Guaraquecaba and Paranagua. This was a typical behavior during the summer probably due to higher biological activity.

This research presents a comparative study between two Brazilian regions with different characteristics that is the case of the South coastal area Pontal do Sul (ACS PS), located on the Parana State and Costa do Sauipe (ACS CS), located in the Bahia, Brazil. For this, were installed 2 atmospheric corrosion stations (ACS) and exposed 4 specimens of metals (aluminum, carbon steel, galvanized steel and copper) used in distribution networks, and reinforced concrete structures like utility crosshead to test the performance of additives such as silica fume, metakaolin, tire rubber and polymeric fibers, and assess both quantitative and qualitative means of aggression against corrosion from the atmosphere in function of time exposition. During this, there was the monthly monitoring of the levels of chloride and sulfate, as well as meteorological data, in order to obtain subsidies for classification of atmospheric corrosivity. The ACS PS was classified as rural atmosphere, the lowest category of aggressiveness (C1), based on the time of wetness and the concentration of pollutants while ACS CS was described as marine (C 4). The most suitable material for this region was the aluminum, followed by galvanized steel. Already, on ACS PS, copper degraded less than the other, on average.

A study on the trace elements transfer from tidal water to mangrove sediments from Guanabara Bay (southeastern Brazil) was performed in laboratory microcosms. Sediment cores were covered with tidal water spiked with 137Cs, 54Mn and 57Co during 5-h experiments, and water samples were taken at regular intervals to measure uptake kinetics at the sediment–water interface. At the end of the experiments, the uptake and diffusional penetration into the sediments was evaluated. Half-removal times from water to sediments were slightly higher for 137Cs (3.4 ± 1.7 h) than observed for 54Mn (2.3 ± 0.2 h) and 57Co (2.6 ± 1.1 h). After these experiments, all radioisotopes presented decreasing activities with increasing sediment depth, being the distribution of 137Cs indicative of higher diffusion within the upper 2 cm. This study on the removal of 137Cs, 54Mn and 57Co from tidal water by mangrove sediments suggests that while 57Co and 54Mn presented closer behaviors, there was a slightly higher mobility of 137Cs.

The extent in which redox conditions can affect the removal kinetics of 58 Co and 65 Zn from tidal water by mangrove sediments was evaluated in microcosm experiments, simulating a tidal flooding period of 6 h. The average half-removal time ( t 1/2 ) of 58 Co from overlaying water was slightly higher (7.3 h) under an N 2 -purged water column than under an aerated water column (5.4 h). A lower difference was found for 65 Zn (1.9 h vs. 1.5 h, respectively). Average removals of 58 Co activities from water were 54.6% (N 2 treatment) and 43.5% (aeration treatment), whereas these values were 88.0% and 92.7% for 65 Zn, respectively. Very contrasting sorption kinetics of different radiotracers occurred, while more oxidising conditions favoured only a slightly higher removal. Average 58 Co and 65 Zn inventories within sediments were 30.4% and 18.8% higher in the aeration treatment, respectively. A stronger particle-reactive behaviour was found for 65 Zn that was less redox-sensitive and more efficiently removed by sediments than 58 Co.

The aim of this wat was to evaluate the water quality in four tidal creeks of Paraná, Brazil, with different anthropic influences. Samples were collected every three months. Temperature, salinity, pH, alkalinity, total CO2, dissolved O2, nitrite, nitrate, N-ammoniacal, phosphate, silicate, particulate suspended matter, humic matter, total chlorophyll, total and fecal coliform bacteria of surface water were measured in each sample and compared. For all the stations water temperature was lower in winter, but ranged within typically subtropical values. Salinity (7 - 25) and pH (7.08 - 7.91) were higher in Perequê tidal creek indicating that only this tidal creek was strongly influenced by the nearby ocean waters. Lower dissolved O2, reaching anoxic levels along with higher phosphate and N-ammoniacal concentrations and higher total (Foi objetivo da presente pesquisa, avaliar a qualidade da água de quatro gamboas do Paraná, Brasil, que sofrem influências antrópicas distintas. Em cinco coletas trimestrais, foram obtidas, as seguintes variáveis em águas superficiais: temperatura, salinidade, pH, alcalinidade, dióxido de carbono, oxigênio dissolvido, nitrito, nitrato, N-amoniacal, fosfato, silicato, material particulado em suspensão, substâncias húmicas, clorofila total, coliformes totais e coliformes termotolerantes. Os resultados mostraram que a temperatura da água apresentou características tipicamente subtropicais com valores significativamente menores no inverno em todas as estações. A salinidade (7 - 25‰) e o pH (7,08 - 7,91) mais elevados, registrados na Gamboa Perequê, indicaram que somente este curso d´água é influenciado pelo mar adjacente. As quantidades baixas de oxigênio dissolvido, chegando a anoxia, altas de fosfato (8,11 - 208,11 µM), N-amoniacal (0,90 - 75,33 µM), coliformes totais (

The removal of 65Zn from tidal water by underlaying sediment cores collected in a mangrove forest and a tidal creek that drains this forest in Sepetiba Bay (SE Brazil) was investigated. After 30-h experiments in laboratory microcosms, the 65Zn half-removal times from tidal creek and mangrove forest sediments were 8.7 ± 1.8 and 9.2 ± 0.9 h respectively. Depth penetration of 65Zn was mainly restricted to the upper 3 cm in mangrove forest cores, while detectable 65Zn activities were found in all layers (0–7 cm depth) of tidal creek cores. An unexpected 65Zn release back to the overlaying water was observed for one of the tidal creek experiments in the 12–18 h interval (corresponding to a return of 17% of the initial 65Zn activity in overlaying water), suggesting a reversibility of the 65Zn removal process (e.g., by adsorption) in tidal creek sediments. The results indicate that mangrove-vegetated sediments allowed a lower vertical mobility of Zn than observed in creek sediments and mangrove sediments appear to be less susceptible to a reversion in the process of zinc removal from overlaying water, suggesting a greater capacity to retain this metal near the water–sediment interface. This first radiotracer approach on the mangrove sediments removal of Zn from tidal waters supports earlier experimental studies employing stable Zn, contributing for a better understanding of the metal uptake kinetics by such sediments and suggesting that these sediments act as active sinks for trace metals.

Na costa brasileira são escassos os estudos sobre bioacumulação de metais traço que visam acessar o status de contaminação em peixes e organismos filtradores. O objetivo deste trabalho é obter um diagnóstico de quatro estuários de importância social e econômica, passiveis de serem a posteriori submetidos a analise mais aprofundada, para a busca da relação de causa e efeito entre variações naturais da biodiversidade e as ações antrópicas desenvolvidas na costa de Pernambuco, Espírito Santo, Paraná e Rio Grande do Sul. Alguns metais exibiram concentrações que excederam os máximos permitidos pela legislação, revelando a necessidade urgente de um estudo sistemático sobre bioacumulação de metais traço e a forma química que se apresentam. Esse trabalho lança as bases para um programa de monitoramento, pois se trata de um estudo piloto disponibilizando informações de base, que promoveu treinamento de equipes e padronização de procedimentos analíticos e, fornecendo um modelo para programas futuros. Palavras – chave: bioindicadores, metais traço, estuários brasileiros.

Seasonal and spatial dynamics of the microphytobenthic biomass on a subtropical intertidal sand flat (25°32'S; 48°24'W) was investigated monthly from September 1995 to July 1996. Chlorophyll-a and Phaeophytin-a contents, temperature, salinity, inorganic nitrogen and phosphate pore water concentrations and sediment characteristics were assessed in the upper (HW), middle (MW) and lower (LW) sections of the flat. Microphytobenthic biomass content showed a conspicuous seasonal and spatial gradient. Higher chlorophyll-a contents were registered in the HW section of the tidal flat (from 11.78 µg.gsed-1 to 38.18 µg.gsed-1) decreasing towards the LW section (from 6.23 µg.gsed-1 to 18.23 µg.gsed-1). Microphytobenthic seasonality was determined mainly by turbulence of the water column, which was influenced by atmospheric events. The sediment properties and nutrient concentrations had a significant effect on the spatial and seasonal distribution of pigments on the intertidal flat. A dinâmica sazonal e espacial da biomassa microfitobêntica em uma planície arenosa intermareal (25º32'S; 48º24'W) foi investigada mensalmente de setembro de 1995 a julho de 1996. A concentração de clorofila-a e feofitina-a, a temperatura, salinidade, concentração de nitrogênio inorgânico e fosfato na água intersticial, além das características do sedimento, foram inferidas na região superior (HW), mediana (MW) e inferior (LW) da planície. A biomassa microfitobêntica apresentou gradientes sazonal e espacial bem definidos. Maiores concentrações de clorofila-a foram registradas na região superior da planície entre marés (HW, de 11.78 µg.gsed-1 até 38.18 µg.gsed-1), decrescendo em direção a região inferior da planície (LW, de 6.23 µg.gsed-1 a 18.23 µg.gsed-1). A sazonalidade microfitobêntica foi determinada principalmente pela turbulência da coluna de água, influenciada pelos eventos atmosféricos. As propriedades do sedimento e as concentrações de nutrientes foram significantes para a distribuição espacial e sazonal dos pigmentos na planície entre marés.

Concentrations of arsenic and four additional trace elements (Cu, Cr, Ni, and Zn) were determined by inductively coupled plasma-optical emission spectrometry in the muscular tissue of the yellow catfish (Cathorops spixii) and the urutu catfish (Genidens genidens) from Paranagua Estuarine Complex, Brazil (PEC). The PEC can be characterized by an environment of high ecological and economic importance in which preserved areas of rainforest and mangroves coexist with urban activities as ports and industries. The average concentrations (in milligram per kilogram dry weight) of elements in the muscle tissue of C. spixii are as follows: Zn (31), As (17), Cu (1.17), Cr (0.62), and Ni (0.28). Similar concentrations could be found in G. genidens with exception of As: Zn (36), As (4.78), Cu (1.14), Cr (0.51), and Ni (0.14). Fish from the geographic northern rural region (Guaraquecaba-Benito) display higher As concentrations in the muscle tissues than fish found in the south-western (urban) part of the PEC. An international comparison of muscle tissue concentrations of trace elements in fish was made. Except for Ni in C. spixii, a tendency of decrease in element concentration with increasing size (age) of the fish could be observed. According to the National Health Surveillance Agency of Brazil, levels of Cr and As exceeded the permissible limits for seafood. An estimation of the provisional tolerable weekly intake of As was calculated with 109 % for C. spixii and with 29 % for G. genidens.

The aim of this study was to investigate the dynamics of the fluorescent dissolved organic matter (FDOM) in Paranaguá Estuarine System (PES) as to infer about the contribution of allochthonous FDOM to the estuarine waters in relation to tidal condition and seasons. Fluorescence spectroscopy was used for such purpose and DOM characterization through fluorescence emission was performed using excitation wavelengths of λex 350 nm and λex 450 nm, the two main fluorescence groups known to be present in natural DOM. Relations between emission wavelength (λem) and environmental variables, and the relevance of these variables to the different tides and seasons were identified by principal component analysis. The results showed that the first class of fluorophores (λex 350 nm) changed from the river (freshwater) towards the estuary, whilst the second class (λex 450 nm) has a more conservative nature and does not change as significantly as the first. Allochthonous DOM contribution to the estuarine system is intensified during the rainy season, especially in spring tides, whereas in the dry season the ratio of autochthonous DOM to total DOM in PES waters increased. We concluded that the variation of maximum λem of the first class of fluorophores (λex 350 nm) is mainly related to allochthonous contribution, whilst the maximum of emission for the second class of fluorophores (λex 450 nm) is dependent on the contribution of the different sources of organic matter (freshwater and marine water DOM contribution).O objetivo deste estudo foi investigar a dinâmica da matéria orgânica fluorescente (FMOD) no Complexo Estuarino de Paranaguá (CEP) para inferir sobre a contribuição da FMOD alóctone nas águas estuarinas em relação à condição de maré e estações do ano (seca e chuvosa). Empregou-se a técnica de espectroscopia de fluorescência, através da utilização de dois comprimentos de onda de excitação, os quais correspondem a duas classes conhecidas de fluoróforos, λex 350 nm e λex 450 nm, para desta forma determinar o comprimento de onda de máxima emissão (λem) da fluorescência da MOD. Relações entre λem e variáveis ambientais e a relevância das relações nas diferentes condições de maré (sizígia e quadratura) e estações do ano (seca e chuvosa) foram identificadas com o uso de análise de componentes principais. Os resultados demonstraram que a primeira classe de fluoróforos (λex 350 nm) foi alterada durante a transição rio estuário, enquanto a segunda classe (λex 450 nm) apresentou um comportamento mais conservativo. A contribuição da MOD alóctone no estuário foi intensificada durante a estação chuvosa, especialmente durante as marés de sizígia, enquanto na estação seca a MOD autóctone é preponderante na composição da MOD total no CEP. Conclui-se que a variação nos λem da primeira classe de fluoróforos (λex 350 nm) é principalmente relacionada à contribuição alóctone, enquanto as diferenças nos λem da segunda classe (λex 450 nm) estão relacionadas com as flutuações nas contribuições das diferentes fontes de MOD no CEP.

In this work, the density of bacterioplankton, bacterial biomass and environmental variables were monitored in two seasons (summer and winter), two times each month (spring tide and neap tide sampling), over a 12 h period, comprising a tidal cycle (semidiurnal), from subsurface and bottom waters, in a fixed station in the Estuarine Turbidity Maximum Zone (ETMZ) of Paranaguá Bay, Brazil. The data were treated with multivariate analyses methods in order to indentify the key controlling factors of the bacterial community dynamics. The microbial community seemed to be structured by a close relationship with the nutrients concentration, mainly by total phosphorous and nitrate. Regardless of variations throughout the tidal cycles, free-living bacteria had a dominant role on the Paranaguá's Bay ETMZ.

DDT in Biota of Paranaguá Bay, Southern Brazil: Recent Input and Rapid Degradation Gerd Liebezeit &Daniela Brepohl &Juliane Rizzi & Flavia Guebert &Mats Krome &Eunice Machado & Ursula Pijanowska Received: 20 December 2010 /Accepted: 14 January 2011 /Published online: 1 February 2011 # Springer Science+Business Media B.V. 2011 Abstract The presence of recent dichlorodiphenyltri-chloroethane (DDT) inputs is established for Paranaguá Bay biota, i.e. bivalves, fish and one sponge. Values ranged from 6.9 to 156.2 ng ΣDDT/g dry weight. Three fish species analysed showed ΣDDT values from 36.8 to 92.1 ng/g dry weight. The highest contents (up to 156.2 ngΣDDT/g dry weight) were found for mangrove oysters (Crassostrea rhizophorae) at locations affected by sewage discharge from Para-naguá City. Turtles as herbivores were not affected by this input with values of 0.7 and 2.2 ngΣDDT/g dry weight. The areal distribution of samples suggests that usage of DDT is widespread around the bay. Fresh DDT input is degraded to DDE and DDD within approximately 5 months.

Urban sewage is considered one of the most important sources of marine pollution in South America, because most coastal cities do not have proper facilities to treat and dispose of sewage. The Paranagua estuarine system is an important estuarine environment of the South American coast where fishing, urban and tourist activities, industries and the main Brazilian grain shipping port are potential sources of pollution in this area. The anthropogenic input of sedimentary organic matter, represented by sewage contribution, was evaluated by fecal steroid concentrations. The coprostanol levels were comparatively low ( −1 ), except at the sites close to Paranagua city, where the coprostanol concentration reached 2.22 μg g −1 showing strong sewage contamination. Fecal steroid levels were comparable to the lower to midrange concentrations reported for coastal sediments worldwide. The results of this work demonstrated that sewage pollution can be considered a problem for a small part of the Paranagua estuary.

A producao primaria e a biomassa microfitobentica foram avaliadas ao longo do gradiente de energia ambiental da planicie entremares da Ilha Rasa da Cotinga, setor euhalino da Baia de Paranagua, durante quatro mares de quadratura do outono-inverno de 1996 e da primavera-verao de 1996/1997. Os oito experimentos in situ foram realizados com uso de câmaras benticas e a producao primaria foi calculada com base na variacao do oxigenio dissolvido, em duas câmaras translucidas e duas opacas. A hipotese nula de que nao ha diferenca significativa entre os periodos amostrados (sazonalidade) e entre o gradiente de energia ambiental da planicie entremares (espacialidade) foi testada utilizando-se ANOVAs uni e bifatorial. A radiacao fotossinteticamenie ativa - RFA foi considerada para cada sitio amostral. A biomassa foi maior no outono-inverno do que na primavera-verao, enquanto a producao primaria e a RFA foram maiores na primavera-verao. Todos os descritores apresentaram um gradiente crescente da regiao inferior, acima da isobata de I metro, para a regiao mediana e superior da planicie. A importância desta comunidade para o ecossistema estuarino da Baia de Paranagua foi discutida. Spatial and seasonal microphytobenthos primary production in subtropical intertidal flat, Paranagua Bay, Parana-Brasil Abstract The microphytobenthic primary production and biomass were measured on the intertidal fiat of the Rasa da Cotinga island, eurihaline sector of Paranagua Bay, during four neap tides of autumn-winter of 1996 and spring-summer of 1996/1997. The eight in situ experiments were carried with benthic chamber and the primary production was measured by dissolved oxygen variation in two light and two dark incubations. The null hypothesis about no significant differences among the periods (season) and the environmental gradient (spatial) in the intertidal fiat was tested by one and two way ANuVAs. Photosynthetic Active Radiation - PAR was measured at each sampling site. The biomass was higher in the autunm-winter than springsummer, while the primary production and PAR were higher in the spring-summer. All variables showed an increase gradient from lower region, above 1 meter isobath, to median and upper region of the intertidal fiat. The importance of this community in the Paranagua Bay estuarine system was discussed.

The Piraquara river basin (Upper Iguaçu River basin - Brazil) was studied as an ecological system throughout a complete seasonal cycle, comprising the rainy and dry season. Analyzes of 16 physical and chemical water variables (dissolved oxygen, biochemical oxygen demand, temperature, pH, conductivity, total nitrogen, total phosphorus, ortophosphates, nitrite, nitrate, ammonium, reagent silicate, total suspended solids, chlorophyll - a, flow velocity and depth) showed correlations between water composition and watershed physiographic features, and the Principal Component Analysis allowed to evidence spatial gradients and seasonal differences. The sampling points were clustered in patches with homogeneous behavior, according to ecologycal concepts: patch 1, with strong influence of Serra do Mar mountains; patch 2, medium course, under Piraquara Dam influence and patch 3, under wetlands influence. Two main factors of serial discontinuity were identified: the Piraquara dam effect and the influence of wetlands. The watershed zoning based on limnological characteristics seeks to subsidize research and biomonitoring for this public springs area.A bacia hidrográfica do rio Piraquara (Bacia do Alto Rio Iguaçu - PR) foi estudada como sistema ecológico ao longo de um ciclo sazonal completo, abrangendo os períodos seco e chuvoso. Análises de 16 variáveis físicas e químicas da água (oxigênio dissolvido, pH, condutividade, DBO5, temperatura, nitrogênio total, fósforo total, ortofosfato, nitrito, nitrato, amônio, silicato, sólidos totais em suspensão, clorofila-a, profundidade e velocidade da corrente) demonstraram correlações entre a composição da água e as características fisiográficas da bacia. Os gradiente espaciais e as diferenças sazonais foram evidenciadas pela Análise de Componentes Principais, e a bacia foi dividida em trechos de comportamento homogêneo, sendo identificadas descontinuidades seriais: Trecho 1, com forte influência da Serra do Mar; Trecho 2, curso médio do rio, sob influência da Represa do Piraquara e Trecho 3, sob influência das várzeas. O trabalho Pretende subsidiar ações de pesquisa, planejamento e biomonitoramento para este manancial público.

Paranagua Bay, on the coast of Parana State in southeastern Brazil (48°25′W, 25°30′S), is part of a large interconnected subtropical estuarine system that includes the Iguape-Cananeia Bay system on the southern coast of Sao Paulo State. Rather than being an estuary, Paranagua Bay (612 km2) is best defined as an estuarine system comprised of two main water bodies, the Paranagua and Antonina bays (260 km2) and the Laranjeiras and Pinheiros bays (200 km2). The system connects to the open sea through three tidal channels, with the main entrance area around Mel Island (152 km2; Fig. 10.1). The structural properties of the bay are typical for a marine ingression environment. Forced regressions, following sea-level maxima at approx. 120,000 and 5,100 B.P., have formed an upper and a lower geomorphologic zone, represented by a drowned, narrow paleo-valley west of Paranagua City and by wide beach ridge plains east of Paranagua, respectively (Angulo 1992; Angulo and Lessa 1997). An extensive coastal plain surrounds Paranagua Bay and the upper reaches of the bay originate about 50km inland at the piedmont of the Serra do Mar mountain range. Mangrove swamps and marshes mainly fringe the interior of the system, while ocean-exposed areas adjacent to the mouth are composed of extensive sand beaches and some rocky shores (Angulo 1992).

Neste relatorio sao apresentados os dados originais e principais resultados tecnicos obtidos durante os Cruzeiros IV (maio de 1996) a XIV (maio de 1997) do Projeto Vieira. Os cruzeiros tiveram como objetivos principais a captura de vieiras para analise de seu crescimento, mortalidade, reproducao e evolucao temporal da abundância do estoque nos dois bancos anteriormente identificados, bem como a analise das variacoes temporais da temperatura, salinidade, nutrientes inorgânicos dissolvidos e clorofila-a na coluna d’agua, composicao do fitoplâncton e microfitobentos, e caracteristicas sedimentologicas (granulometria e teor de materia orgânica e carbonatos) das respectivas areas. Entre outubro e abril, observou-se a formacao de uma forte termoclina resultante da intrusao da Agua Central do Atlântico Sul (ACAS) sobre a plataforma continental interna. Nos demais meses, a coluna d’agua mostrou-se termicamente bastante homogenea. A salinidade apresentou valores minimos (ao redor de 30) em alguns meses de inverno, sendo que nos demais periodos houve o predominio de salinidades superiores a 36 em toda a coluna. Concentracoes de fosfato, nitrito, nitrato e clorofila-a foram maiores na agua de fundo, sendo que os valores maximos de clorofila-a foram observados justamente durante a intrusao da ACAS sobre a area. O silicato apresentou padroes sazonais e batimetricos muito menos definidos do que os demais nutrientes. Ao longo do periodo observou-se poucas variacoes nas caracteristicas granulometricas dos dois bancos, havendo o predominio de areias finas a muito finas em ambas as areas. Por outro lado, observou-se variacoes sazonais expressivas dos teores de carbonato de calcio e materia orgânica, esta ultima, com valores 8 vezes maiores na primavera e verao em relacao as demais estacoes. Os maiores teores de carbonato de calcio foram observados no outono e inverno. Apos diversas modificacoes, obteve-se performances satisfatorias de captura de vieiras pelo beamtrawl, permitindo o acompanhamento temporal do recurso. Enquanto as abundâncias do estoque no Banco de Sao Francisco apresentaram-se reduzidas porem relativamente estaveis ao longo do tempo, verificou-se que o Banco de Bom Abrigo foi praticamente exaurido entre dezembro/95 e maio/96. Em decorrencia do estado extremamente fragil do recurso, sugere-se que, baseando-se nos resultados complementares a serem obtidos no decorrer do projeto, medidas emergenciais sejam implementadas no sentido de evitar um possivel colapso irreversivel do recurso no sul do Brasil.

Sediment oxygen consumption (SOC) and pelagic primary production were estimated during austral spring (1986), late summer, autumn and winter (1987) in the eutrophic, sub-tropical lagoon of Guarapina, southern Brazil. SOC measurements were conducted by in vitro incubations of intact sediment cores (diameter, 8 cm; volume 0.81) and also in situ with “Bell Jars” (diameter, 60 cm; volume, 551). Primary production in terms of oxygen was estimated from in situ light/dark bottle incubations. SOC rates (g O 2 m −2 day −1 ) were 0.98 ± 1.18 ( n = 8) in spring, 2.26 ± 0.86 ( n = 14) in late summer, 1.95 ± 0.38 ( n = 14) in autumn and 1.49 ± 0.39 ( n = 18) in winter. This corresponds to a mean of approximately 53, 42, 54 and 44%, respectively, of the daily net pelagic primary production. Results obtained from dark incubations with cores and “Bell Jars” agreed extremely well. The former method yielded SOC rates of 1.87 ± 0.60 g O 2 m −2 day −1 ( n = 27) and the latter 2.08 ± 0.97 gO 2 m −2 day −1 ( n = 11). Organic-rich muddy sediments (particulate organic carbon (POC), 8–12%), which are predominant in the lagoon, in contrast to sandy sediments, showed the highest consumption rates. On some occasions, littoral sandy sediments covered with an organic-rich flocculent layer attained similar SOC rates as muddy sediments.

A acidificação dos oceanos, resultado do aumento das emissões de gás carbônico (CO2), por atividades antrópicas, vem causando uma mudança no equilíbrio químico do sistema carbonato e uma consequente diminuição do pH nos oceanos mundiais. Cerca de 30% das emissões antropogênicas de CO2 é absorvida pelo oceano, o que já reduziu o PH em 0,1 unidade em águas superficiais e são esperadas ainda maiores reduções. A escala de mudanças \"toleráveis\" de pH ainda é incerta para muitos organismos e pouco conhecida para muitos processos biológicos, particularmente no sedimento. Este trabalho teve como objetivo quantificar tanto as taxas atuais de remineralização da matéria orgânica e fluxos de nutrientes na interface água-sedimento, como as alterações nessas taxas em resposta a diferentes cenários de acidificação do oceano, usando câmaras de incubação bêntica tanto in situ como em laboratório. Os experimentos in situ e coleta de material para montagem dos experimentos em laboratório foram realizados através de mergulho autônomo, na área rasa de Ubatuba-SP (6-8 m de profundidade). As incubações mostraram alto consumo de O2, variando entre -17 mmol m-2 d-1 em Julho de 2012 e -112 mmol m-2 d-1 em Abril e Junho de 2013. Houve uma dominância da nitrificação, com fluxos entre 0.2 and 0,4 µmol m-2 d-1 (sem variação temporal). As incubações também mostraram fluxos positivos de amônio, sendo os mais altos (1.0 - 1.5 µmol m-2 d-1) observados em Março, Abril e Junho de 2013. No geral, os processos de heterotrofia líquida prevaleceram sobre os processos autotróficos na região de estudo. Esses resultados indicam que os processos que ocorrem nos sedimentos costeiros de Ubatuba são: (1) remineralização aeróbica bêntica, (2) processos de nitrificação maiores que denitrificação e (3) provável excreção de organismos bênticos. O experimento de acidificação in situ indicou um aumento nos fluxos de O2 (de 0.02 para 45 mmol m-2 d-1). Os experimentos com acidificação mostraram efeitos similares: aumento do consumo médio de O2 e liberação de CO2, principalmente na areia. Houve diminuição nos processos de nitrificação em resposta à diminuição do pH. O estudo forneceu resultados importantes e inéditos sobre os processos biogeoquímicos em sedimentos costeiros da região de Ubatuba (SP), assim como os efeitos da acidificação dos oceanos nos processos biogeoquímicos em sedimentos costeiros. Ocean acidification, a result of an increase in carbon dioxide (CO2) anthropic emissions, has caused a change in the chemical balance of the carbonate system and a consequent pH decrease in the world\'s oceans. Approximately 30% of anthropogenic CO2 is absorbed by the ocean, which has already reduced the pH by ∼0.1 units in surface waters (with further reductions expected). The scale of \"tolerable\" pH changes is still uncertain for many organisms and little-known for biological processes, particulary for the sediment. This work aimed to quantify both the current rates of organic matter remineralization and nutrient fluxes at the sediment-water interface and the changes in those rates in response to different ocean acidification scenarios, using benthic incubation chambers both in situ and in the laboratory. The in situ studies and sample collections for laboratory experiments were performed via SCUBA in a shallow area near Ubatuba-SP (6-8 m deep). Incubation experiments showed high oxygen (O2) consumption, ranging from -17 mmol m-2 d-1 in July 2012 to -112 µmol m-2 d-1 in April and June 2013. They also exhibited a dominance of nitrification, with fluxes between 0.2 and 0,4 µmol m-2 d-1 (with no temporal variation). Incubations also exhibited a release of ammonium, with the highest fluxes (1.0 - 1.5 µmol m-2 d-1) in March, April and June 2013. In general, net heterothrophic processes prevailed over autotrophic processes for the study region. The interstitial water parameters (ammonium, phosphate, dissolved iron and total sulfides) exhibited no significant difference between the two kinds of sediment analyzed, silt (station 1) and sand (station 2). These results suggested that the processes occurring in the coastal sediments of Ubatuba are: (1) benthic remineralization mediated by bacterial biota, (2) nitrification prevailed over denitrification and (3) probably excretion by benthic organisms. The experiment in situ indicated an increase in the fluxes of O2 (from -70 to -108 µmol m-2 d-1) and CO2 (from 0.02 to 45 µmol m-2 d-1). The acidification experiments showed a similar effect: a higher O2 average consumption and CO2 release, mostly in the sandy sediment. A decrease in nitrification processes occurred in response to decreased pH. This work has provided a baseline for the biogeochemical processes in coastal sediments in Ubatuba (SP), as well as demonstrated the effects of ocean acidification on biogeochemical processes in coastal sediments.

Os sedimentos marinhos são receptores finais de vários compostos da coluna de água, possuindo uma participação ativa nos ciclos biogeoquímicos. Comunidades microbianas possuem um papel crucial nestes ciclos, sendo responsáveis por grande parte da remineralização da matéria orgânica em sedimentos superficiais. Foram realizados dois experimentos com simulações de processos oceanográficos em microcosmos: Enriquecimento Orgânico, testando a diferença entre a chegada de fitoflagelados e diatomáceas no sedimento e Ressuspensão, simulando a passagem de frente fria. Foram analisados os compostos referentes à qualidade e quantidade da matéria orgânica sedimentar, assim como o fluxo de nutrientes da interface água-sedimento. No Experimento Enriquecimento, as diferentes algas causaram respostas distintas nos processos de degradação da matéria orgânica, aumentando a qualidade e o metabolismo das comunidades presentes, além de modificar os fluxos de nutrientes, sendo notada uma resposta mais rápida nos mecanismos de degradação devido à adição do fitoflagelados. No Experimento Ressuspensão, o distúrbio físico ocasionou uma resposta imediata e significativa na liberação dos nutrientes do sedimento para a interface água-sedimento e alterações nas concentrações de ácidos graxos, principalmente nos dois primeiros dias após a simulação. Logo, os diferentes eventos oceanográficos simulados comprovaram sua influência frente aos processos biogeoquímicos, principalmente na disponibilidade de ácidos graxos e na liberação de nutrientes para a água sobrejacente Marine sediments are the final receivers of many organic compounds from the water column, playing an important role in biogeochemical cycles. Microbial communities are important to these cycles as they remineralize organic matter within surface sediments. Microcosm experiments were conducted to simulate two important oceanographic processes: Organic Enrichment, to test differences between sinking patterns of phytoflagellates and diatoms and Resuspension, simulating the passage of a cold front. The quality and amount of the organic matter was assessed, as well as the nutrient flow between the sediment-water interface. In the Enrichment Experiment, distinctive responses in the degradation processes were noted between treatments where the addition of phytoflagellates increased the quality of the organic matter, caused faster metabolism communities present in the sediment, and modify the patterns of nutrient flux rates. In the Resuspension Experiment, the physical disturbance caused an immediate and significant release of nutrients from the sediment to the sediment-water interface and changed the in the concentrations of fatty acid content most notably during two days after the resuspension event. Thus, the different simulated oceanographic events influenced biogeochemical processes, particularly in the availability of fatty acids and the release of nutrients to the overlying water