Abstract The construction of a data bank concerning metal and metalloid content of bioindicator fish from coastal areas is very important as it can help environmental managers in decision making. In natural conditions, the concentration of elements can be influenced by abiotic parameters such as water salinity. In this study, catfish Cathorops spixii were evaluated concerning the total arsenic (As) concentration in the muscle tissues of individuals subjected to different abiotic conditions in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC), which was recently included on the Ramsar list of wetlands of international importance. Seventy-four catfish were seasonally caught in the northern and southern regions of the CIELC and their hydrochemical parameters were obtained. C. spixii from the southern, best preserved, area showed arsenic concentrations around ten times higher than the maximum limit established for fish intended for human consumption. However, these high concentrations of arsenic could be associated with the abiotic parameters of the water, such as salinity variations, in this area.

THE ESTUARINE ENVIRONMENT AND pH VARIATION: NATURAL LIMTS AND EXPERIMENTAL OBSERVATION OF THE ACIDIFICATION EFFECT ON PHOSPHORUS BIOAVAILABILITY. This study shows the variation of pH in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC). Data from 3 years (2019, 2021, 2022) were obtained in 17 points presenting the following ranges: temperature (14.88-27.05 ºC), pH (7.16-8.40) and DIP (0.20-11.28 µmol L-1) along a saline gradient (0.05-32.09) under different hydrodynamics, biogeochemical processes and anthropogenic influence. The pH buffering capacity due to the presence of weak acid salts in saline water (S ≥ 30) was associated to the lowest DIP, decreasing with low salinity values, confirming the direct correlation among salinity and pH. The highest temperatures in the winter of 2021, corroborated with the abnormal climate event in that year. An in vitro experiment showed results of the interaction of PID and sediments with different textures, with and without the presence of the benthic microbiota under a considerable decreasing of the pH (acidification) in relation to the natural condition of this environment. The P sediment flux characterized Iguape sector as a P sink with or without biota, Ararapira sector as a P source with biota and Cananéia, as P source without biota. The salt water buffered the pH and sediment buffered DIP both associated to the biogeochemical and hydrodynamic processes contribute to the homeostasis in the system.

Abstract The Cananéia-Iguape Estuarine-Lagoon Complex (CIELC) is an extremely productive coastal ecosystem. It encloses the Valo Grande channel, built 160 years ago, which introduces water from the Ribeira River directly into the estuarine system, contributing to important biogeochemical changes in the region. Many nutrients arrive at the estuary through this channel, as well as metals and other slightly soluble elements that become part of the sediments. This study aims to evaluate the processes that govern the distribution of rare earth elements (REE) in the sediments of the complex by using fractionation patterns, anomalies, and the geochemical signature of minerals to evaluate sources, natural levels, and the possible anthropogenic forcing to which CIELC is subjected. ∑REE* ranged from 14.2 to 285 mg kg -1 and showed a distribution related to depositional/textural characteristics influenced by the regional and local lithological setting and a possible contamination. The REE/Al ratio indicated enrichment in the sea adjacent to the estuary and at stations in the Ribeira River and Valo Grande. While the Hf/Al ratio indicated natural enrichment related to the presence of heavy minerals in most of these stations, this ratio fails to justify enrichment at some stations in the northern part of the estuary and the Ribeira River. Fractionation patterns and anomalies allowed us to identify the main heavy minerals related to REE enrichment at CIELC. Cerium (Ce) anomalies showed a possible relation with biologically mediated Ce +3 to Ce +4 oxidation processes in the most productive areas of the estuary. Europium (Eu) anomalies were strongly associated with different mineral assemblies in several CIELC sectors. Abundance, fractionation patterns, and REE anomalies corroborate the categorization of CIELC sediments as part of a pristine system in its southern region and as subject to anthropogenic influences in its northern area.

Abstract Over the last decades, regional climate changes, erosion, and heightened agricultural runoffs have increased nutrient and particle input in rivers, unbalancing the biogeochemical cycle of this suspended material along estuaries. In this context, particle fluxes in the euphotic zone, a very productive layer and important to maintain the food chain and estuarine preservation, require better understanding. This study aims to evaluate particle sedimentation fluxes in the photic zone of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC), considering sectors under different salinities and trophic statuses. A cylindrical sediment trap was installed at the base of the photic layer to measure particle fluxes and photopigments. Meanwhile, water samples were taken to measure temperature, salinity, pH, dissolved oxygen, and nutrients. Valo Grande (a freshwater domain) showed high nutrient concentrations, in which high fluxes of phaeopigments and chlorophyll-b highlighted the contribution of vegetable detritus to particle sinking. In the Batatais mangrove creek, the high fluxes of organic particles (675.32 mg m-2 d-1) and chlorophyll-a (98.40 mg m-2 d-1) evinced a high contribution of microplankton to carbon sinking. During the winter of 2018, flocculation processes were evinced in the flood tide of the Cananéia Bay as an important driver of sedimentation rates, with considerable fluxes of inorganic particles (1161.20 mg m-2 d-1) and chlorophyll-a (83.27 mg m-2 d-1). In the summer of 2019, we observed a lower flux in total particles (451.24 mg m-2 d-1) in a period of haline stratification. In the Ararapira Channel, the lowest organic particle fluxes (<100 mg m-2 d-1) were associated with ultra-oligotrophic conditions, indicating a low influence of microplankton on sinking particles. These findings suggest that freshwater input, tidal variation, and trophic status are relevant controls of sinking particles in different CIELC sectors.

Abstract The Cananéia-Iguape estuarine-lagoon complex (CIELC), located in the State of São Paulo, Brazil, is considered an area of the Biosphere Reserve. However, an artificial channel built in the northern sector of the system (Iguape) has promoted an unnatural input of fresh water into the system, leading to enhanced drainage of terrestrial material into the estuary and influencing silicon biogeochemistry within the complex. This study used the distribution of different fractions of silicon along the system as a proxy for the freshwater input. The samples were collected during August, 2012 (winter) and February 2013 (summer) and analyzed for dissolved silicate, biogenic silica, and lithogenic silica. Dissolved silicate reached values above 200 µmol L -1 in the two seasonal periods, indicating the constant supply of terrestrial material in the northern sector of the system associated with fresh water. Southward, where the system is more preserved (Cananéia-Ararapira), the concentration decreased dramatically. Lithogenic silica (LSi) reached extremely high values of ~700 µmol L -1. Biogenic silica (BSi) showed concentrations up to 120 µmol L -1 with distribution more dependent on assimilation processes and the nature of the biological communities than on the source of fresh water. The availability of different forms of Si revealed remineralization, deposition, adsorption, and uptake mechanisms with different dynamics in the northern and southern sectors of the system, evidencing the environmental impact by the Valo Grande Channel.

Abstract Estuaries are important features for global biogeochemical understanding, due to their highly coupled interaction between sediment and water. In those places, the land-sea transect sometimes has a gradient of physical and chemical characteristics, influencing the availability of nutrients and consequently primary production. This study aimed to observe the benthic aerobic respiration and sediment-water nutrient fluxes in a freshwater to marine transect in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC) on the southeastern Brazilian Coast. This area contains the most pristine mangrove at the limit between tropical and subtropical zones, providing an ideal observatory for ecological research programs. Intact sediment cores were incubated in laboratory to determine fluxes of O2, TCO2, and dissolved nutrients. Three different sites with different salinities were sampled during the four seasons of the year. Sediment characteristics of the sites were compared, showing higher organic matter in the lowest saline (LS) site and higher phytopigments in the highest saline (HS) site, as expected. Benthic aerobic respiration, O2 and CO2 fluxes, ranged from −0.4 to −3.2 mmol m−2h−1 and 0.1 to 1.5 mmol m−2h−1, respectively, and exhibited statistically significant variations between seasons and in a salinity gradient. Dissolved inorganic nitrogen and silicate, ranging from −228.7 to 544.8 μmol m−2h−1 and −205.8 to 4,173.5 μmol m−2h−1, respectively, were generally released from the sediment, whereas phosphate ranged from −25.2 to 29.6 μmol m−2h−1 with more variation in time and space. The LS site was characterized as a nitrogen sink and a silicate and phosphate releaser, and the HS site was characterized as a nitrogen producer and a phosphorus consumer. However, seasonal and spatial variations were observed, and the interaction between space and time factors was always highly significant, indicating that the metabolic behavior of the benthic compartment depends on both trophic and physicochemical conditions.

Abstract The assessment of water quality using multiple abiotic and biological indicators is very important for understanding anthropogenic impacts and the health of the ecosystem. The Olaria is a short river system that flows into the Cananeia estuary. This aquatic system crosses the urban center of the city of Cananeia, where it eventually receives untreated domestic wastewater. This study aims to apply multi-indicators of environmental pollution to understand the influence of the Olaria system on the Cananeia estuary. For this purpose, indicators of water quality and genotoxic and pathological responses in fish were used. Data on salinity, pH, and silicates in surface water indicate a more accentuated continental influence in the inner part of the Olaria river system. Moreover, the data recorded on the inner area of the Olaria system, which presents lower hydrodynamic characteristics and the largest urban population, indicated the presence of dissolved oxygen and nutrients (phosphate [P-PO4 -3], nitrite [N-NO2-], and ammonium [N-NH4+]) at levels that exceed the established limits for water quality by the Brazilian environmental legislation (Conselho Nacional do Meio Ambiente - CONAMA). The presence of Escherichia coli in all analyzed water samples indicates a local or point source of domestic wastewater contamination near the Olaria system. Fish species such as Centropomus undecimalis (Robalo Flexa) and Sphoeroides testudineus (Baiacu Pintado) showed toxicogenetic damage, indicating clastogenic and/or aneugenic exposure in the aquatic environment. Hepatic pathologies such as pyknosis nuclei, inflammation, hepatocyte swelling, and necrosis were found in all specimens evaluated, and C. undecimallis exhibited all these pathological changes. These results highlight the importance of biomonitoring the effects of anthropogenic disturbance on the aquatic biota that frequent the Olaria system and are dependent on the water quality.

Abstract Some fish species can be used as target species and bioindicators of environmental disturbances. In this context, biological indicators such as the length, weight, and height of lapillus otoliths of the ariid species Cathorops spixii and Genidens genidens were considered bioindicators of contamination of the Cananéia-Iguape estuarinelagoon complex (CIELC) in this study. The CIELC is an estuary with spatial and temporal differences regarding its hydrobiochemical properties and this characteristic has been related to changes in biological predictors such as the otolith morphometrics of estuarine fish. Therefore, this study aimed to verify the responses of otolith dimensions to sexual and temporal changes, throughout the CIELC. In total, 163 wild catfish C. spixii and 55 G. genidens were collected during the winter period of 2009, 2017, and 2018 in the CIELC. In general, the weight and length of lapillus otoliths of C. spixii and G. genidens were good metrics adjusted to fish growth. Females of C. spixii were significantly larger than males and subadults and there were no significant differences regarding the sexual approach of G. genidens. The temporal approach showed significant differences between the years for both catfish. C. spixii sampled in 2009 and 2018 showed greater total length (TL) and total weight (TW) when compared with fish from 2014 and 2017 (p < 0.05). G. genidens collected in 2018 had greater TL and TW than the specimens sampled in the other years (p < 0.05). Otolith dimensions seem to have followed this same pattern, since females of C. spixii had higher values for otolith weight, height, and length than males and subadults (p < 0.05). The data obtained in this study can be a potential tool for application combined with other ecological analyses and conservation studies in the CIELC.

RESUMO O presente trabalho teve como objetivo monitorar a dispersão de plumas de efluentes provenientes dos emissários submarinos de Praia Grande e do Rio Itanhaém, por meio do processamento do modelo Delft3D (módulos hidrodinâmico e de qualidade da água) e do modelo Visual Plumes (módulo UM3). A modelagem de campo próximo indicou que as correntes geradas pelo vento foram mais eficientes do que as correntes de maré na diluição inicial das plumas dos emissários; e a modelagem de campo distante, validada qualitativamente, demonstrou que as concentrações dos potenciais poluentes de todas as plumas simuladas não ultrapassam os limites máximos estabelecidos pelo Conselho Nacional do Meio Ambiente quando essas plumas atingem as praias da região de estudo.

ABSTRACT This study’s goal was to monitor the dispersion of effluent plumes from the Praia Grande’s submarine outfalls and from the Itanhaém River by processing the Delft3D model (hydrodynamic and water quality modules) and the Visual Plumes model (UM3 module). The near field modeling indicated that wind-driven currents were more efficient than tidal currents in the initial dilution of the outfalls’ plumes; and the far field modeling, qualitatively validated, demonstrated that the potential pollutants’ concentrations in all the simulated plumes don’t exceed the maximum limits established by the National Environmental Council when these plumes reach the study region’s beaches.

Abstract: The human impact on estuarine regions results in an increasing concentration of trace elements in the environment, exposing aquatic organisms. In this study, Zn, Co, Cr, and As were determined in the muscle tissue of some fish species from Santos-São Vicente (SSV), a recognized polluted region, and in the Cananeia estuary (CAN). Genotoxicity was also determined for the evaluation of the chronic effect on ichthyofauna, to enlarge the bank of environmental data regarding the effects of pollution, and to suggest other fish bioindicator species that may contribute to monitoring programs. The obtained data showed a similar profile of an accumulation of Co and Zn in Micropogonias furnieri and Chaetodipterus faber, where: Santos Bay > CAN > inner area of SSV. A low frequency of micronucleus was observed. However, in general, fish from the inner area of the SSV estuary presented more nuclear abnormalities than fish from Santos Bay and CAN. In the inner area of SSV, Centropomus paralelus and Diapterus rhomneus showed more changes than other fish species. It was possible to consider that the habits of each species, contributed to a different profile of trace element accumulation, followed by the chemical components in the organism offering different vulnerability.

RESUMO O ensino de Ciências foi incorporado aos currículos escolares somente no século XIX. No Brasil-Império o ensino das Ciências Naturais era incipiente, embora ciências já fizessem parte do currículo do ensino secundário desde a criação do Colégio Pedro II, em 1837. Os primeiros cursos de nível superior em Geociências (Geologia, Geofísica, Meteorologia e Oceanografia) começaram a ser criados somente a partir da segunda metade do século passado. Atualmente, há cursos nessas modalidades em todo o país, que enfrentam, contudo, sérios obstáculos para que o ensino evolua de acordo com as necessidades atuais do mercado de trabalho, e das tendências impostas pelo avanço tecnológico. Neste trabalho analisamos entraves e lacunas profissionais no Ensino Superior e destacamos algumas práticas educacionais capazes de melhorar o aprendizado, que poderiam ser universalizadas. É inadiável expandir a área de Geociências nos cursos de formação e capacitação de professores para a Educação Básica; o artigo reúne alguns fatores essenciais para atingir essa meta.

ABSTRACT The teaching of Science was incorporated into school curricula only in the nineteenth century. In Imperial Brazil, the teaching of the natural sciences was incipient, although, since the creation of the Colégio Pedro II in 1837, Science was already part of the curriculum of secondary education. But only in the second half of the last century the earliest courses in Geosciences (Geology, Geophysics, Meteorology, and Oceanography) began to be created. Currently, there are courses in these modalities across the country. However, there are serious obstacles for teaching to evolve in keeping with the current needs of the professional market and the trends imposed by technological advances. In this work, we analyze obstacles and professional gaps in Higher Education, and highlight some educational practices capable of improving learning and which could be universalized. It is no longer possible to put off the expansion of the area of Geosciences in teacher training and qualification courses for Basic Education. This article brings together some essential factors to achieve this goal.

Resumo Os compostos orgânicos dissolvidos encontrados na água do mar oferecem uma indicação de processos biogeoquímicos e influência antropogênica à luz de suas concentrações e comportamentos associados a diferentes áreas oceânicas. Os aportes de rios contribuem com cargas orgânicas para a água do mar de acordo com o nível de influência natural e urbana. Uma diluição deste material é esperada no oceano. Em torno das ilhas oceânicas, a quantidade de matéria orgânica é influenciada pelo ciclo de vida dos organismos marinhos e pela ocupação humana. As proporções de carbono orgânico dissolvido (DOC), nitrogênio orgânico dissolvido (DON), fósforo orgânico dissolvido (DOP) e sua associação com oxigênio dissolvido podem ser utilizadas para avaliar as condições ambientais em termos de impactos naturais e antropogênicos. A informação disponível sobre os compostos orgânicos dissolvidos essenciais (C, N e P) na água do mar é rara. Este estudo busca incentivar o uso de compostos orgânicos dissolvidos na avaliação de impacto ambiental nas áreas costeiras do Brasil. A distribuição espacial de DOC, DON, DOP e ureia foi analisada em quatro regiões: Itamaracá (ITA), Plataforma Interna de Recife (RIS), Ilha Fernando de Noronha (FN) e Porto de Recife (RH), todos em Pernambuco - Brasil. No caso do DOC, os valores obtidos variaram de 51,60 µmol L-1 (0,62 mg L-1) a 358,47 µmol L-1 (4,30 mg L-1), os valores de DOP variaram de 0,01 a 2,16 µm L-1, ambos Apresentando seus valores mais altos em RH, a área mais intensamente urbanizada. Em relação ao DON, um valor extremamente alto de 92,89 µmol L-1, com ureia atingindo 12 µmol L-1, ambos em RH, refletem a descarga orgânica e de esgoto. Às vezes, a concentração de ureia esteve associada ao tratamento precário de esgoto combinado com a atividade turística, como no caso de FN. Nenhuma variação espacial significativa foi observada para DOP tendo em conta todas as estações e regiões, e os valores apresentaram maior variação de FN. Os índices DOC:DON foram superiores a 7 (2-4 vezes a relação Redfield) e revelaram a qualidade da matéria orgânica e a importância do processo local de remineralização, confirmando que a N-limitação aumentou o uso de formas orgânicas, principalmente em FN. As condições oligotróficas preservadas em RIS, Itamaracá e FN foram observadas em relação aos compostos orgânicos dissolvidos (C, N, P), mas no que diz respeito ao FN, são recomendáveis ações de monitoramento efetivas, pois é uma área remota preservada.

Abstract The dissolved organic compounds found in seawater offer an indication of biogeochemical processes and anthropogenic influence in the light of their concentrations and behavior associated with different oceanic areas. River inputs contribute with organic loads to seawater according to the level of natural and urban influence. A dilution of this material is expected toward ocean. Around oceanic islands, the quantity of organic matter results from the life cycle of marine organisms and from human occupation. The ratios of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP) and the association with dissolved oxygen can be used to evaluate the environmental conditions in terms of natural and anthropogenic impacts. Available information about the essential dissolved organic compounds (C, N and P) in seawater is rare. This study seeks to encourage the use of dissolved organic compounds in environmental impact assessment in coastal areas of Brazil. The spatial distribution of DOC, DON, DOP and urea was analyzed in four regions: Itamaracá (ITA), Recife Inner Shelf (RIS), Fernando de Noronha Island (FN) and Recife Harbor (RH), all in Pernambuco State - Brazil. In the case of DOC, the values obtained varied from 51.60 µmol L-1 (0.62 mg L-1) to 358.47 µmol L-1 (4.30 mg L-1), DOP values varied from 0.01 to 2.16 µmol L-1, both presenting their highest values in RH, the most intensely urbanized area. In relation to DON, an extremely high value 92.89 µmol L-1, with urea reaching 12 µmol L-1, both in RH, reflects organic and sanitary discharge. Sometimes the urea concentration was associated with precarious sewage treatment combined with tourist activity, as in the case of FN. No significant spatial variation was observed for DOP taking into account all the stations and regions, and the values presented a greater range of variation in FN. The DOC:DON ratios were higher than 7 (2-4 times the Redfield ratio) and revealed the quality of the organic matter and the importance of the local process of remineralization, confirming that the N-limitation enhanced the use of organic forms, mainly on FN. The preserved oligotrophic conditions of the RIS, Itamaracá and FN were observed in relation to dissolved organic compounds (C, N, P), but, as regards FN, effective monitoring actions are advisable as it is a pristine area.

Resumo As áreas urbanizadas marcam sua presença nos sistemas hidrológicos com alguns sinais biogeoquímicos, incluindo entradas de silício. A influência natural da lixiviação e erosão é feita por contribuição de silicato e, às vezes, o solo agrícola possui microfilóticos e contribui com sílica biogênica. Uma vez no sistema hidrológico, o silício pode integrar os ciclos biogeoquímicos mostrando um equilíbrio ou não entre formas inorgânicas e biológicas que revela uma tendência de processos que ocorrem em cada setor da interface estuarino-marinha. Este estudo tem como objetivo avaliar o impacto de um rio fortemente poluído/urbanizado, cujo aporte pode ser evidenciado por diferentes formas de silício que podem marcar o aporte terrestre, processo de erosão, a presença de espécies de fitoplâncton com estruturas silicosas, principalmente associada a diatomáceas e, também, estudar a pluma do rio espalhando-se na área costeira realizando perfis de silício na região adjacente à foz do rio. A região costeira do Recife está sob influência dos insumos fluviais dos rios Capibaribe e Beberibe verificados pela baixa salinidade observada (mínimo 33,93). A distribuição de formas de silício mostrou variação setorial e os valores máximos foram distintos. O silicato dissolvido atingiu 14,40 µmol L-1, silício litogênico (LSi) no máximo de 25,76 µmol L-1 e sílica biogênica (BSi) atingindo 7,39 µmol L-1 perto da foz do rio em direção ao mar, evidenciando a influência do rio vindo do oeste, alcançando a barreira portuária no final e se propagando no mar em direção ao nordeste. Devido à maior disponibilidade de nutrientes nas estações mais próximas da costa, a produção primária foi incentivada com a evidência de altos valores de clorofila-a associados ao silicato dissolvido (r=0.71) e ao SiB (r=0.44). Nas estações mais distantes da costa, as formas de silício apresentaram concentrações muito baixas e BSi/Clorofila-a mostrou correlação negativa associada a concentrações de clorofila-a, evidenciando a participação de atores não silicosos na produção primária em profundidade média em águas tropicais oligotróficas.

Abstract The urbanized areas mark its presence in the hydrological systems with some biogeochemical signs including silicon inputs. Natural influence of leaching and erosion is done by silicate contribution and sometimes, the agriculturally soil contains microphytoliths and contributes with biogenic silica. Once in the hydrological system, the silicon can integrate the biogeochemical cycles showing a balance or not between inorganic and biological forms that reveals a tendency of processes that occur in each sector of the estuarine-marine interface. This study aims to evaluate the impact of a heavily polluted/urbanized river, whose input can be evidenced by the contribution of different forms of silicon that can evidence the terrestrial contribution, erosion process, the presence of phytoplankton species with siliceous structures, mainly associated to diatoms and also, to study the river plume spreading on the coastal area by undertaking silicon profiles in the region adjacent to the river mouth. The coastal region of Recife is under influence of fluvial inputs from Capibaribe and Beberibe rivers verified by observed low salinity (min. 33.93). The distribution of silicon forms showed sectorial variation, and the maximum values were dissimilar. Dissolved silicate reached 14.40 µmol L-1, lithogenic silicon (LSi) maximum of 25.76 µmol L-1 and biogenic silica (BSi) reaching 7.39 µmol L-1 near the river mouth toward the sea, evidencing the river influence coming from the west, achieving the port barrier at the end and propagating in the sea toward northeast. Due to higher nutrient availability in the stations nearest to the coast, primary production was encouraged with evidencing by high values of chlorophyll-a associated to silicate (r=0.71) and to BSi (r=0.44). In the stations more distant to the coast, the forms of silicon showed very low concentrations and BSi/Chlorophyll-a showed negative correlation associated with chlorophyll-a concentrations evidencing the participation of non-silicon actors in the primary production in medium depth in oligotrophic tropical waters.

Resumo A oligotrofia tem base na baixa disponibilidade de nutrientes inorgânicos, sendo que, normalmente, em águas equatoriais, o teor de nutrientes inorgânicos não é suficiente para sustentar a riqueza de vida observada em alguns lugares especiais nesta latitude. Assim, a compreensão do papel dos componentes orgânicos dissolvidos nos ciclos biogeoquímicos do N e do P poderia esclarecer o suporte da cadeia alimentar em águas equatoriais oligotróficas. Este estudo foi realizado com o objetivo de contribuir ao conhecimento da disponibilidade de nutrientes e participação de componentes orgânicos na condição trófica das águas do entorno de uma ilha equatorial oceânica no Atlântico Sul. A água e o fitoplâncton foram amostrados na franja ocidental do arquipélago Fernando de Noronha, em março de 2015. As condições tropicais oceânicas prevaleceram neste domínio oceânico com altas salinidade (>36,19) e temperatura (>28,30°C). As condições oceânicas garantiram os altos valores de pH (>8,0) e oxigênio dissolvido (>5,00 mL L-1). A alcalinidade mostrou ligeiras variações com menores valores associados à interação biológica. A matéria particulada em suspensão esteve relativamente baixa e a fração orgânica foi associada ao processo produtivo e/ou contribuição da poluição, o que é confirmado principalmente por altas concentrações de DON (~4,00 µmol L-1) associada aos maiores valores de clorofila total na situação de produção primária e, com a ureia em situação de poluição. O conteúdo de ureia atingiu 2,77 µmol L-1 em um ponto de disposição de efluentes quando um evento de contaminação foi observado na região. Os nutrientes inorgânicos disponíveis apresentaram baixas concentrações, com uma média de N-amoniacal de 1,99±0,64 µmol L-1, nitrato com média de 0,13±0,04 µmol L-1, nitrito com média de 0,19±0,13 µmol L-1. O DIN variou de 0,74 a 4,32 µmol L-1, principalmente representado por N-amoniacal. O DOC apresentou valores de 53 a 109 µmol L-1 e, a relação DOC:DON confirmou uma fonte orgânica para o reservatório de N inorgânico a partir da oxidação da matéria orgânica e indicou que os compostos ricos em nitrogênio são reciclados mais rapidamente do que os compostos ricos em carbono. As concentrações totais de clorofila atingiram 0,81 mg m-3 e a notável presença de cianobactérias filamentosas frente à baixa disponibilidade de nitrogênio inorgânico, conduzindo a uma cadeia trófica inicialmente suportada com contribuição do processo de fixação.

Abstract Oligotrophy has its basis in low inorganic nutrient availability and it is generally known that in equatorial waters inorganic nutrient availability is insufficient to sustain the richness of life observed in some special places at this latitude. Thus, the understanding of the organic dissolved component role in N and P biogeochemical cycles could explain the support of the food chain in oligotrophic equatorial waters. This study was undertaken for the purpose of contributing to the knowledge of nutrient availability and the participation of dissolved organic components in the trophic conditions of an oceanic equatorial island in the South Atlantic. Water and phytoplankton were sampled on the western fringe of the Fernando de Noronha Archipelago in March 2015. Tropical oceanic conditions prevailed in this oceanic domain with high salinity (>36.19) and temperatures (>28.30°C). The oceanic conditions assured a high pH and dissolved oxygen levels (>5.00 mL L-1). Alkalinity showed slight variations, its lowest values being associated with biological interaction. Suspended particulate matter was relatively low and its organic fraction was associated with the productive process and/or pollution contribution, which is confirmed mainly by high DON concentrations (~4.00 µmol L-1) with an association with high total chlorophyll in the primary production process and with urea in the pollution situation. The urea content attained 2.77 µmol L-1 at a waste disposal outlet when a contamination event was observed in the region. The available inorganic nutrients showed low concentrations with an N-ammonium average of 1.99±0.64 µmol L-1, nitrate with an average of 0.13±0.04 µmol L-1, and nitrite with an average of 0.19±0.13 µmol L-1. The DIN varied from 0.74 to 4.32 µmol L-1, principally represented by N-ammonium. DOC showed values of from 53 to 109 µmol L-1 and the DOC:DON ratio confirmed the organic source as being an inorganic N pool of oxidized organic matter and indicated that nitrogen-rich compounds are recycled faster than carbon-rich compounds. Total chlorophyll concentrations reached 0.81 mg m-3 and the noteworthy presence of filamentous cyanobacteria despite low inorganic nitrogen availability lead to a trophic chain initially supported with the contribution of a fixation process.

Resumo O principal objetivo deste trabalho é avaliar distribuição sazonal e espacial do carbono orgânico dissolvido (COD), nitrogênio orgânico (NOD), fósforo orgânico dissolvido (POD) e ureia em 10 estações do Parque Estadual Marinho da Laje de Santos (PEMLS). As estações 1 a 4 (mais próximas do continente) e as estações de 5 a 10 (mais próximas do parque marinho), todas na plataforma continental. Os resultados mostram que não foram observadas variações sazonais estatisticamente significativas para o COD e POD, todavia, o COD e o NOD, no período de verão apresentaram um pequeno aumento mostrando o aumento da atividade biológica e a influencia continental. Por outro lado, o NOD apresentou valores elevados em junho (2014 - inverno) e janeiro de 2015, variando de 12.51 a 32.76 µmol L-1, segundo o método de análise ANOVA (p< 0,01). Foram observados baixos valores de NOD em janeiro de 2014 (0,32-8,98 µmol L-1), em um verão anormalmente seco, enquanto que os valores mais elevados foram observados em julho de 2014 (27.50 µmol L-1). Ureia apresentou valores baixos na região do PEMLS e zonas costeiras atingindo 4,00 µmol L-1. Muitas vezes, a concentração de ureia pode estar associada com atividade de mergulho no parque. COD, NOD e ureia apresentaram valores ou diferenças entre as estações no PEMLS (5-10) e aquelas mais costeiras (1-4). O COD nas estações costeiras atingiu 267 µmol L-1, enquanto que no PEMLS, o valor máximo foi de 100 µmol L-1. Nenhuma variação significativa foi observada quanto à distribuição espacial entre as estações costeiras e as do parque para o POD (ANOVA p <0,01). Considerando-se que os compostos orgânicos dissolvidos também podem ser monitorados por meio da avaliação de C, N, P em sua fração orgânica, chegou-se à conclusão que, na região estudada o impacto de águas eutrofizadas sob influência continental e antrópica é mínimo e esses parâmetros poderiam ser monitorados para subsidiar o monitoramento na região.

Abstract The main objective of this work is evaluate seasonal and spatial distribution of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP) and urea in 10 stations of the State Marine Park of Laje de Santos (SMPLS). Stations 1 to 4 (nearest the continent) and the stations 5 to 10 (nearest the marine park) all of them were on the continental shelf. The results show that no statistic significant seasonal variations were found for the DOC and DOP nevertheless DOC and DON in summer period were lightly above the winter period showing the increase in biological activities and continental influence. On the other hand, DON showed high values in June (2014 - winter) to January 2015, ranging from 12.51 to 32.76 µmol L-1 according to the ANOVA method (p <0.01). Low values of DON in January 2014 (0.32 to 8.98 µmol L-1) was observed in a summer unusually dry, while the highest values were observed in July 2014 (27.50 µmol L-1). Urea presented low values in SMPLS region and coastal areas reaching 4.00 µmol L-1. Sometimes, the urea concentration can be associated with diving activity in the park. DOC, DON and urea showed differences between SMPLS stations (5-10) and coastal stations (1-4). DOC coastal stations reached 267 µmol L-1, while the SMPLS the maximum value was 100 µmol L-1. No significant spatial variation between coastal stations and park were observed for the DOP (ANOVA p <0.01). Considering that dissolved organic compounds can also be monitored by means of the evaluation of C, N, P in their organic fraction, it was concluded that in the studied region the impact of eutrophic waters under continental and anthropic influence is minimal and these parameters could be monitored to support monitoring in the region.