Amazon Estuary Research Articles

DIVERSIDADE DE RAIAS DE ÁGUA DOCE (Chondrichthyes : Potamotrygonidae) NO ESTUÁRIO AMAZÔNICO

Um levantamento sobre registros de ocorrência de raias de água doce (Potamotrygonidae) no estuário amazônico foi realizado utilizando-se dados bibliográficos, informações de coleções científicas disponíveis on-line e amostragens de campo. Os resultados indicaram a presença de oito espécies nominais: Plesiotrygon iwamae, Paratrygon aiereba,Potamotrygon humerosa, Potamotrygon motoro, Potamotrygon cf. ocellata, Potamotrygon orbignyi,Potamotrygon scobina e Potamotrygon aff. hystrix. Apenas cinco destas espécies são atualmente consideradas cientificamente válidas. Adicionalmente a estas, foram identificadas ao menos mais duas espécies e um gênero novo queno momento estão em processo de descrição. O número de espécies ocorrentes no estuário amazônico ainda é incerto, podendo variar de cinco a dez dependendo dos avanços e revisões sistemáticos que venham a ser realizados neste grupo de elasmobrânquios.

Palaeolimnological studies and ancient maps confirm secular climate fluctuations in Amazonia

Secular Amazon discharge oscillations were investigated comparing information from ancient cartography, satellite images, palaeovegetation, sediments, anthropology and climate, focusing on the evolution of Marajo Island in the Amazon estuary. Four phases were identified. (1) 800–1200 a.d.: Amazon discharge increased gradually and eastern Marajo was a vegetation-free tidal plain with energy oscillations. (2) 1200–1350 a.d. was a dry period with lower river discharges, lower energy, increasing water salinities and maximum mangrove extension, coinciding with the extinction of chiefdoms in Marajo. (3) 1350–1540 a.d.: Amazon discharge increased rapidly, inducing a dominance of freshwater vegetation, inundation of east Marajo and likely a regional rise of relative sea-level (RSL). (4) 1540–1750 a.d.: RSL decreased, coinciding with an El Nino-related intense drought ca. 1600 a.d. Emergence of eastern Marajo was rapid and completed in the eighteenth century, under RSL stabilization to current values. The approach used provided evidence of intermittent large changes in Amazon climate, and can facilitate the prediction of future regional dynamics.

“44Local Theory”: Nature and the Making of an Amazonian Place

Like nature, culture, and its glamorous sibling global, is one of those deeply compromised words our language will not relinquish. So central to so many anthropological projects, it is unlikely to be transcended; instead it continues to be both fought over and reinvigorated. In this article, I imagine the topography of what we might call a methodology of locality. In trying to understand how we can do our thinking about the local, I begin with a disarmingly transparent question: How, in all its specificity, does this place that holds our attention come into being? Pursuing this puzzle provokes ripples of association that shape interpretation like contour lines on a map, destabilize naturalized binaries, and shadow the unruly series of concentric circles through which a place is tied into multiple worlds. The most proximate circles are also, as Walter Benjamin suggests, immediate sites of danger and confusion. One finds, for example, a dark confluence of whirlpools at the very heart of the story of Igarap6 Guariba, the small place in the Amazon estuary I describe in what follows (see Figure 1).1 There is, for one, the giddying vortex of Brazilian national politics during the 1960s, a trauma that produced the regional dislocations of modernist highway construction, the violating histories of land conflict and expropriation, and the eventual fluorescence of international deforestation discourse.2 Then there are the shifting networks of translocal political economy; the fluctuating markets in forest commodities; and the assertion, breakdown, and reconstitution of forms of governance and control. And then-as we shall see in some detail-there is what has now become the ur-problem of the Amazon: nature. In what follows, I have drawn on the particularities of Igarapd Guariba to offer a reading of the that is also an argument for local theory. By this I mean an analysis generated from the ground of ethnographic specificity, from

Hábitos alimentares de <em>Sotalia fluviatilis</em> no estuário amazônico

In this paper we present an analysis of the fifty S. fluviatilis feeding habits in the Amazonian Estuary. Animals were bycaught by the artisanal fishing fleet between 1996 and 2001. Feeding habits were analyzed by prey occurrence frequency (%F) and number percentage and stomachs contents preys similarity between marine and freshwater fish species present in the Amazonian Estuary. Thirteen fish species were identified (%F= 86.6), the most significant families were Sciaenidae (32%), Trichiuridae (26%) e Ariidae (16%), and four crustaceans species (%F=26). S. fluviatilis feeding habits did not differ by gender and in general, calves had higher prey diversity than juveniles and adults. The similarity was high (0.89) between estuarine S. fluviatilis feeding habits and the fishes species present in the Amazonian Estuary when the environment is mostly marine.

Origens pluriétnicas no cotidiano da pesca na Amazônia: contribuições para projeto de estudo pluridisciplinar

O presente texto é versão de uma conferência proferida no Departamento de Genética da Universidade Federal do Pará (UFPA), no marco do tema Populações amazônicas ontem, hoje e perspectivas para o futuro. Essa conferência enfatizava a relevância das contribuições dos primeiros formadores da sociedade amazônica para a sociedade de hoje e vem agora compor o cenário deste volume temático do Boletim do Museu Goeldi. Os dados apresentados são frutos de trabalhos de campo anteriores da autora em diferentes momentos e lugares da região e associados à pesquisa bibliográfica e à experiência pessoal da autora em diversos 'lugares de pescadores' do litoral, médio Amazonas, estuário amazônico e ilha do Marajó. Este conjunto serviu de base e instrumento para estas reflexões propositivas para novas pesquisas mutidisciplinares, tendo em vista preencher lacunas sobre a história da pesca na Amazônia. Assim, propõese a evocar as origens pluriétnicas da sociedade e cultura que se formaram na Amazônia visando à maior clareza sobre as relações entre os primeiros contingentes formadores da sociedade amazônica e os segmentos sociais contemporâneos. Com isso imagina-se trazer à reflexão o valor das contribuições socioculturais e ambientais daqueles diferentes contigentes sociais e chamar atenção para o legado sociocultural deixado pela ancestralidade indígena que permeia a ocupação humana na região.

Diatom biomass and productivity in oceanic and plume-influenced waters of the western tropical Atlantic ocean

Whereas diatoms (class Bacillariophyceae) often dominate phytoplankton taxa in the Amazon estuary and shelf, their contribution to phytoplankton dynamics and impacts on regional biogeochemistry are poorly understood further offshore in the western tropical Atlantic Ocean (WTAO). Thus, relative contribution of diatoms to phytoplankton biomass and primary production rates and associated environmental conditions were quantified during three month-long cruises in January–February 2001, July–August 2001, and April–May 2003. The upper water column was sampled at 6 light depths (100%, 50%, 25%, 10%, 1% and 0.1% of surface irradiance) at 64 stations between 3° and 14°N latitude and 41° and 58°W longitude. Each station was categorized as ‘oceanic’ or ‘plumewater’, based on principal component analysis of eight physical, chemical and biological variables. All stations were within the North Brazil Current, and plumewater stations were characterized by shallower mixed layers with lower surface salinities and higher dissolved silicon (dSi) concentrations than oceanic stations. The major finding was a much greater role of diatoms in phytoplankton biomass and productivity at plumewater stations relative to oceanic stations. Mean depth-integrated bSi concentrations at the plumewater and oceanic stations were 14.2 and 3.7 mmol m −2, respectively. Mean depth-integrated SiP rates at the plumewater and oceanic stations were 0.17 and 0.02 mmol m −2 h −1, respectively. Based on ratios of SiP and PP rates, and typical Si:C ratios, diatoms contributed on average 29% of primary productivity at plumewater stations and only 3% of primary productivity at oceanic stations. In contrast, phytoplankton biomass (as chlorophyll a concentrations) and primary production (PP) rates (as 14C uptake rates) integrated over the euphotic zone were not significantly different at plumewater and oceanic stations. Chlorophyll a concentrations ranged from 8.5 to 42.4 mg m −2 and 4.0 to 38.0 mg m −2 and PP rates ranged from 2.2 to 11.2 mmol m −2 h −2 and 1.8 to 10.8 mmol m −2 h −2 at plumewater and oceanic stations, respectively. A conservative estimate of annual integrated SiP in offshore waters of Amazon plume between April and August is 0.59 Tmol Si, based on mean SiP rates in plumewaters and satellite-derived estimates of the area of the Amazon plume. In conclusion, river plumewaters dramatically alter the silicon dynamics of the WTAO, forming extensive diatom-dominated phytoplankton blooms that may contribute significantly to the global Si budget as well as contributing to energy and matter flow off of the continental shelf.

Mixed potential for sustainable forest use in the tidal floodplain of the Amazon River

We evaluated the structural and compositional variability between floodplain forest sites in the Amazon estuary. Although tidal floodplain forests have been commonly perceived as a homogenous forest type, comparisons of basal area and stem density show that, from one locale to another, these forests can vary greatly in structure. Comparisons of common diversity indices along with detrended correspondence analysis and indicator species analysis also reveal marked compositional differences. Local structural and compositional differences result in contrasting potential for alternative forest uses such as timber, latex, fruit and seed-oil production. For example, areas with high dominance of palms, important features of the estuarine landscape, tend to have lower potential for timber management. While some previous research in the Amazon estuary has emphasized the forest management for timber, other studies have focused primarily on the importance of non-timber forest products for subsistence and market economies, and for conservation. Our results indicate that contrasting views of the management potential of Amazonian tidal floodplain forests reflect not only heterogeneity of forest use by riverine people, but also the heterogeneity of the forests themselves.

Função de afilamento para Virola surinamensis (Roll.) Warb

Este estudo foi conduzido com o propósito de gerar equação de afilamento para Virola surinamensis (Roll.) Warb, que está entre as espécies mais exportadas pela indústria madeireira do estuário amazônico. Foram testados os modelos de Kozak (1969), Baldwin (1991), Demaerschalk (1972) e Garay (1979). Todos esses modelos estimaram o diâmetro comercial com precisão, porém os três primeiros resultaram em inconsistência ao estimar a altura comercial. O modelo de Garay foi selecionado e utilizado para gerar uma curva de cubagem para a espécie.

Manejo sustentado para floresta de várzea na amazônia oriental

Este estudo teve como objetivo definir opções de colheita em bases sustentadas para florestas de várzea no estuário amazônico. Os dados foram coletados na propriedade florestal da Exportadora de Madeira do Pará Ltda. (Emapa), localizada no Município de Afuá, ao norte do Estado do Pará. A amostragem foi realizada em 29 parcelas de 5.000 m². Foram medidas todas as árvores e palmeiras com dap > 45 cm. As espécies comerciais que apresentaram condições de serem colhidas por terem apresentado os melhores índices fitossociológicos e qualitativos foram: Virola surinamensis, Carapa guianensis e Hymenaea oblongifolia. Entre as espécies potenciais, destacou-se Terminalia dichotoma; e no grupo das espécies não-comerciais, Eschweilera coriacea, Swartizia racemosa e Licania macrophylla. Os resultados indicaram que a floresta pode ser manejada, adotando-se o plano de colheita que utiliza um Quociente de De Liocourt 50% maior do que o original (q = 2,61) e remoção de 30 % da área basal, o que corresponde a um lucro potencial de US$ 3.945,40/ha.

Generation of overtides and compound tides in Amazon estuary

Tidal propagation in estuaries is affected by friction and fresh water discharge, besides changes in the depth and morphology of the channel. Main distortions imply variations in the mean water level and asymmetry. Tidal asymmetry can be important as a mechanism for sediment accumulation and turbidity maximum formation in estuaries, while mean water level changes can affect navigation depths. Data from several gauges stations from the Amazon estuary and the adjacent coast were analyzed and a 2DH hydrodynamic model was configured in a domain covering the continental shelf up to the last section of the river where the tidal signature is observed. Based on data, theoretical and numerical results, the various influences in the generation of estuarine harmonics are presented, including that of fresh water discharge. It is shown that the main overtide, M4, derived from the most important astronomic component in the Amazon estuary, M2, is responsible for the tidal wave asymmetry. This harmonic has its maximum amplitude at the mouth, where minimum depths are found, and then decreases while tide propagates inside the estuary. Also, the numerical results show that the discharge does not affect water level asymmetry; however, the Amazon river discharge plays an important role in the behavior of the horizontal tide. The main compound tide in Amazon estuary, Msf, generated from the combination of the M2 and S2, can be strong enough to provoke neap low waters lower than spring ones. The results show this component increasing while going upstream in the estuary, reaching a maximum and then slightly decaying.

Dimensões humanas do uso e cobertura das terras na Amazônia: uma contribuição do LBA

O entendimento das mudanças em paisagens amazônicas depende de documentação das alterações na cobertura da terra. Este artigo parte de resultados do Experimento de Larga Escala de Biosfera-Atmosfera na Amazônia (LBA) relativos ao tema para focalizar um estudo transversal que analisa as dimensões sociais e biofísicas dessas transformações. As áreas de estudo representam um gradiente de fertilidade de solos e inclui distintos mosaicos de paisagens, desde o estuário Amazônico e a Região Bragantina até o nordeste de Rondônia. Áreas de assentamento rural são enfatizadas, devido a sua relevância social e a seus impactos sobre a cobertura das terras em escala local e regional. Para exemplificar o potencial destes estudos, apresentamos resultados comparativos para Machadinho d'Oeste e Vale do Anari, RO. A análise multitemporal utilizou imagens do satélite Landsat e levantamentos de campo. Proprietários, seringueiros, madeireiros e outros atores locais foram entrevistados sobre seus sistemas de produção e a história de uso das terras. O cálculo de métricas espaciais embasou nossas conclusões. Os resultados indicam que o desenho do assentamento e aspectos institucionais têm um papel importante no processo de alteração da paisagem. A combinação de lotes privados com reservas comuns, manejadas por populações locais, pode produzir efeitos positivos na manutenção de maiores manchas de floresta. A metodologia utilizada oferece potenciais de integração, análise e monitoramento do uso e cobertura das terras na Amazônia, visando fornecer subsídios a políticas que valorizem as dimensões sociais e ambientais do desenvolvimento da região.

Thallium isotope composition of the upper continental crust and rivers—An investigation of the continental sources of dissolved marine thallium

The thallium (Tl) concentrations and isotope compositions of various river and estuarine waters, suspended riverine particulates and loess have been determined. These data are used to evaluate whether weathering reactions are associated with significant Tl isotope fractionation and to estimate the average Tl isotope composition of the upper continental crust as well as the mean Tl concentration and isotope composition of river water. Such parameters provide key constraints on the dissolved Tl fluxes to the oceans from rivers and mineral aerosols. The Tl isotope data for loess and suspended riverine detritus are relatively uniform with a mean of ε 205Tl = −2.0 ± 0.3 (ε 205Tl represents the deviation of the 205Tl/ 203Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 10 4). For waters from four major and eight smaller rivers, the majority were found to have Tl concentrations between 1 and 7 ng/kg. Most have Tl isotope compositions very similar (within ±1.5 ε 205Tl) to that deduced for the upper continental crust, which indicates that no significant Tl isotope fractionation occurs during weathering. Based on these results, it is estimated that rivers have a mean natural Tl concentration and isotope composition of 6 ± 4 ng/kg and ε 205Tl = −2.5 ± 1.0, respectively. In the Amazon estuary, both additions and losses of Tl were observed, and these correlate with variations in Fe and Mn contents. The changes in Tl concentrations have much lower amplitudes, however, and are not associated with significant Tl isotope effects. In the Kalix estuary, the Tl concentrations and isotope compositions can be explained by two-component mixing between river water and a high-salinity end member that is enriched in Tl relative to seawater. These results indicate that Tl can display variable behavior in estuarine systems but large additions and losses of Tl were not observed in the present study.

GOVERNING THE AMAZON TIMBER INDUSTRY FOR MAXIMUM SOCIAL AND ENVIRONMENTAL BENEFITS

ABSTRACT The timber industry in the Brazilian Amazon is currently supplied primarily with timber from private properties. Each year, hundreds of informal contracts are made between Amazon logging companies and small-holders. Loggers receive timber, while farmers receive cash and/or improvements in their road networks. The proposed Brazilian National Forest Programme emphasizes the development of concession-based forestry within an expanded system of National Forests, explicitly avoiding the forests that are occupied by people. It will therefore miss important opportunities for the timber industry to improve the livelihoods of millions of low-income farmers, extractivists, and indigenous people. Recent partnerships between industry and farmers in agricultural settlements demonstrate the pivotal role that progressive timber companies can play in assisting farm communities with their development. Such alliances are favoured by current environmental and agrarian reform policies, including the generous government funding for road construction and housing that accompanies new settlements. Communities in extractive reserves and in the floodplain forests of the Amazon estuary have similarly demonstrated the direct benefits that can accrue to forest residents through control, management, processing, and sale of their wood resources. The policy challenge is to foster a new generation of relationships among the rural poor, timber companies, and environmental and social agencies in order to enhance the How of benefits to the rural poor, while avoiding large-scale logging- and fire-induced impoverishment of Amazon forests.

Phenology, litterfall, growth, and root biomass in a tidal floodplain forest in the Amazon estuary

A dinâmica de floresta sujeita a inundacao parece ser fortemente influenciada pela frequencia e intensidade de disturbios naturais como a inundacao. Em uma antiga floresta sucessional de varzea proxima ao porto de Belem, Brasil, testou-se esta hipotese pela medicao sazonal dos padroes de fenologia, incluindo queda de serrapilheira, em relacao a duas variaveis chaves: chuva e nivel da mare. Em adicao, estimamos o crescimento anual da comunidade florestal pela medicao do incremento do diâmetro de troncos ao longo do tempo e desenvolvimento radicular. Encontrou-se alta correlacao entre florescimento e frutificacao com chuva e nivel da mare, porem as correlacoes entre a queda da serrapilheira e estas variaveis foram geralmente fracas. Ao contrario de nossa hipotese, biomassa de raizes ate 1 m de profundidade nao variou significativamente ao longo do gradiente topografico, e esta foi menor a intermediaria em todos os niveis topograficos do que em outras florestas neotropicais. A queda de serrapilheira e o incremento de troncos foram superiores do que em outras florestas tropicais, indicando uma alta produtividade neste ecossistema.

<a name=top></a>Floristic composition and topographic variation in a tidal floodplain forest in the Amazon Estuary

Floristic composition and topographic variation in a tidal floodplain forest in the Amazon Estuary). Slight topographic variations appear to exert dramatic effects on the structure of forests subject to inundation. In a late successional tidal floodplain forest near the Amazon port of Belem, Brazil, we examined these effects by studying floristic composition along a topographic gradient. We predicted that, relative to high sites, low sites would be characterized by high representation of life forms and taxa characteristic of inundated sites. We found striking variations in floristic composition along a slight topographic gradient. In comparison with topographically high sites, low sites were characterized by a high representation of Palm trees (Arecaceae), low diversity of trees and lianas, and high plant density. These variations appear to reflect edaphic limitations imposed by periodic flooding. The high spatial variation in floristic composition found in this ecosystem suggest caution in implementing intensive forms of agriculture. RESUMO - (Composicao floristica e variacao topografica em uma floresta de varzea no Estuario Amazonico). Pequena variacao topografica aparentemente exerce um dramatico efeito na estrutura florestal sujeita a inundacao. Em uma floresta de varzea em avancado estagio sucessional de perto do porto amazonico de Belem, Brasil, examinamos este efeito estudando a composicao floristica ao longo de um gradiente de topografia. Previamos que, relativo a locais altos, locais baixos seriam caracterizados por alta representacao de formas de vida e taxons caracteristicos de locais inundados. Encontramos impressionantes variacoes ao longo de um ligeiro gradiente de topografia. Em comparacao com locais de topografia alta, locais baixos foram caracterizados por uma alta representacao de palmeiras arboreas (Arecaceae), baixa diversidade de arvores e cipos, e alta densidade de plantas. Esta variacao reflete, aparentemente, limitacoes edaficas impostas pelo alagamento periodico. A alta variacao espacial na composicao floristica encontrada neste ecossistema sugere precaucao na implementacao de formas intensivas de agricultura.

The urban market of Açaí fruit ( Euterpe oleracea Mart.) and rural land use change: Ethnographic insights into the role of price and land tenure constraining agricultural choices in the Amazon estuary

This paper examines the recent development of the acai fruit economy in regional Amazonian urban markets (as a staple food) and more recently among national and international consumers (as a fashion food) and the consequences for agroforestry intensification by Caboclo communities in the Amazon estuary. The paper is based on long-term ethnographic research and field experiments; the acai fruit economy is discussed from agricultural, social, and economic perspectives; attention is given to its historical development, the structure of acai fruit production, its agents, the relationship among themselves and the urban market. Decadal price performance is presented for acai fruit and acai transportation costs and compared to major agropastoral products for the Eastern Amazon region. Dominant views about the ‘economic rationality’ of rural producers' decision-making are discussed. Acai fruit has performed as well as and in some cases surpassed most agro-pastoral products of the Northern region. Economic returns for producers reflect linkages between price signals from urban markets, harvesting decision, and land tenure condition of the producer. Urban markets for the fruit is expanding and bringing new participants to the acai fruit economy further conditioning the ability of rural producers to take advantage of external markets for forest products. Discussion of factors conditioning agricultural development and integration between urban and rural areas conclude the article.

Approaches to Evaluation of Self-Purification in Estuarine Rivers of Souhteast of Amapá State - Brazil

There are a number of reasons that make Amazon estuary an important natural water resource. First, it is biologically productive being the spawning and nursery ground for many important aquatic biota. Second, it serves as receiving waters for wastewater discharges and for navigation use. Third, it has been demonstrating its elevated dilution and self-purification capacity for constituents of the water, principally bacteria, toxic substances, organic material and nutrients. Many cities and small ports of the State of the Amapá located on estuaries and coastal zones are ready affecting their quality through runoff, domestic and industrial wastewater. So, the present research evaluated the water quality in four rivers located close to the periurban areas of Macapá and Santana and rural area of Mazagão municipality. The main objective is to diagnostic the spatial-temporal distribution of some variables and parameters of the water quality, considering important factors as atrophic, hydrologic and climatologic effects in streams sanitation.

River or mangrove? Tracing major organic matter sources in tropical Brazilian coastal waters

The influence of mangrove-fringed tropical estuaries on coastal carbon budgets has been widely recognised. However, a quantitative differentiation between riverine and mangrove-derived inputs to the dissolved (DOM) and microparticulate organic matter (POM) pool of these environments has been hitherto not possible. Based on lignin-derived phenols and stable carbon isotopes a chemical signature for mangrove, terrestrial and marine-derived organic matter was established for a mangrove estuary in North Brazil. A mixing model was applied to calculate the contribution of each of the three sources to the DOM and POM pool in the estuary throughout 18 tidal cycles in the course of one year. Best source assignment for POM was reached with the yield of lignin phenols and δ13C as paired indicators, while the origin of DOM was best identified by the yield of lignin phenols and the acid to aldehyde ratio of vanillyl phenols. Although only about 6% of the fluvial catchment area is covered by mangroves, their contribution to the estuarine DOM and POM pool generally exceeded several times the terrigenic input from the hinterland. This outwelling of mangrove-derived organic matter was enhanced during the rainy season. DOM and POM were exported from the mangrove to the estuary in similar proportions. Most mangrove-POM was rapidly removed from the water column, while mangrove-DOM behaved conservatively. In contrast, terrestrial DOM was almost entirely removed in the outer part of the estuary, which was accompanied by a concomitant increase in terrestrial POM. This seems to be the result of a geochemical barrier zone for this type of DOM in the estuary. Generally, a high proportion of mangrove-DOM was present in the outer part of the estuary, even at high tide. This indicates DOM outwelling from mangroves in adjacent bays or estuaries and points to similar driving forces controlling this process on a regional scale. Mangroves probably play a more important role than rivers for marine carbon budgets along the North Brazilian coast south of the Amazon estuary.

Do mangroves rather than rivers provide nutrients to coastal environments south of the Amazon River? Evidence from long-term flux measurements

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 213:67-77 (2001) - doi:10.3354/meps213067 Do mangroves rather than rivers provide nutrients to coastal environments south of the Amazon River? Evidence from long-term flux measurements Thorsten Dittmar*, Rubén José Lara Zentrum für Marine Tropenökologie, Fahrenheitstr. 6, 28359 Bremen, Germany *Present address: Alfred-Wegener-Institut für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany. E-mail: tdittmar@awi-bremerhaven.de ABSTRACT: Mangroves play an important role in the biogeochemical cycles of coastal and marine ecosystems in the tropics. However, few studies have been carried out to clarify the extent to which mangroves represent a source of nutrients and organic matter for adjacent coastal waters or function, alternatively, as a sink. Here we present results of a long-term nutrient-flux study in one of the world's largest mangrove areas in North Brazil. These are up to now the only published nutrient flux data for Brazilian mangroves, and constitute one of the most comprehensive data sets in this field. Throughout 36 tidal cycles in the course of 1 yr, fluxes of organic carbon (DOC, POC), nitrogen (DON, PON) and dissolved inorganic nutrients (N, Si, P compounds) were determined in a tidal creek connecting a clearly defined area of mangroves (2.2 km2) with the Caeté Estuary. Additionally, a qualitative whole-estuary approach was applied (190 km2 of mangroves). Both methods revealed an outwelling of dissolved organic matter and nutrients from the mangroves, exceeding considerably that of mangroves in other regions of the world. This net export was (annual average, mmol [m2 mangrove]-1 d-1) DOC ‰ 10, DON ‰ 0.7, ammonium ‰ 0.2, silicate ‰ 6 and phosphate ‰ 0.02. Nitrate fluxes were comparatively low. Silicate and phosphate were exported mainly during the dry season and DON during the rainy season. DOC showed no seasonal trend. Especially ammonium fluxes presented strong asymmetries between day and night. Although only ~6% of the fluvial catchment area is covered by mangroves, their nutrient export exceeded that of the hinterland. The annual export from mangroves on a regional scale (6700 km2 from 0°S, 50°W to 3°S, 42°W) was estimated (mol yr-1) as DOC ‰ 30x109, DON ‰ 2x109, ammonium ‰ 0.4x109, silicate ‰ 15 ×109 and phosphate ‰ 0.04x109. Compared with the Amazon River discharge these fluxes are low (1 to 3% of the Amazon fluxes). The nutrient cycles of coastal marine environments are probably mangrove-dominated southeast of the Amazon Estuary, contrary to the river-dominated cycles to the northwest. KEY WORDS: Outwelling · Nutrients · Organic matter · Mangrove · Brazil Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 213. Online publication date: April 04, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Description of Nematopsis mytella n. sp. (Apicomplexa), parasite of the mussel Mytella guyanensis (Mytelidae) from the Amazon estuary and description of its oocysts

Summary Numerous uninucleated phagocytes with several parasitophorous vacuoles (PV) each containing a single oocyst of an apicomplexan gregarine parasite of the mussel Mytella guyanensis (Mytelidae) from the Amazon estuary were described. The phagocytes were in close contact with the gill tissue. Each phagocyte was surrounded by a thin layer composed of electron-lucent material. The plasmalemma of the phagocyte presented numerous microvilli irregularly projected to the surrounding thin layer. The phagocyte cytoplasm was occupied by large light areas, numerous small vesicles and among them a variable number of PV each containing a single oocyst. The oocysts were 11.5 μm long and 8.2 μm wide and the wall was 0.7 μm thick. The apical zone of the wall contained a circular micropyle covered by an operculum attached to the PV membrane by a dense cord. Externally, the oocyst wall was surrounded by numerous, long and anastomosed microfibrils attached to the wall and connected to the PV membrane. Several dense bodies within the PV were observed. Each oocyst contained a single vermiform uninucleated sporozoite. This gregarine was named Nematopsis mytella n. sp. and the morphological characteristics of its oocysts were described. This parasite became the first record of Nematopsis sp. and the first gregarine from the Amazonian mussel.