First Assessment of Carbon Stock in the Belowground Biomass of Brazilian Mangroves

ABSTRACT Studies on belowground roots biomass have increasingly reported the importance of the contribution of this compartment in carbon stock maintenance in mangrove forests. To date, there are no estimates of this contribution in Brazilian mangrove forests, although the country has the second largest area of mangroves worldwide. For this study, trenches dug in fringing forests in Guaratiba State Biological Reserve (Rio de Janeiro, Brazil) were used to evaluate the contribution of the different classes of roots and the vertical stratification of carbon stock. The total carbon stock average in belowground roots biomass in these forests was 104.41 ± 20.73 tC.ha−1. From that, an average of 84.13 ± 21.34 tC.ha−1 corresponded to the carbon stock only in fine roots, which have diameters smaller than 5 mm and are responsible for over 80% of the total belowground biomass. Most of the belowground carbon stock is concentrated in the first 40 cm below the surface (about 70%). The root:shoot ratio in this study is 1.14. These estimates demonstrate that the belowground roots biomass significantly contributes, more than 50%, to the carbon stock in mangrove forests. And the mangrove root biomass can be greater than that of other Brazilian ecosystems.

As consequências do processo de desterritorialização da pesca artesanal na Baía de Sepetiba (RJ, Brasil): um olhar sobre as questões de saúde do trabalhador e o ambiente / Deterritorialization of artisanal fisheries in Sepetiba Bay (State of Rio de Janeiro, Brazil): an overview of occupational health and environmental issues

O trabalho analisa as consequências da desterritorialização na Baía de Sepetiba sobre o processo de trabalho e saúde dos pescadores artesanais daquele território. Por meio do conceito de determinantes sociais em saúde, aproxima os novos vetores de crescimento da região com as condições de vida e saúde destes trabalhadores. Através de entrevistas semiabertas e grupos focais explicitou-se esta relação. Os resultados sugerem uma forte associação entre os empreendimentos portuários e as instalações do programa nuclear da Marinha do Brasil com a pesca extrativa tradicional, contribuindo para o aumento do tempo de navegação e dos riscos ocupacionais inerentes à pesca artesanal. Além dos impactos econômicos e ambientais na produtividade e qualidade do pescado, consequência direta das obras de dragagem e dos novos fluxos de navegação e fundeio estabelecidos e impostos pelo estado.

This paper outlines the consequences of deterritorialization of artisan fishing folk in Sepetiba Bay in the State of Rio de Janeiro on the occupational and health status of this population living in the area. By means of the concept of social determinants in health, it compares the new patterns of growth in the region with the living and occupational health conditions of these workers. This relationship was explained after conducting semi-structured interviews and focus groups. The results point to a strong relationship between the port undertakings and the installations of the nuclear program of the Brazilian Navy with subsistence and extractive fishing, contributing to an increase in the time spent at sea and the inherent occupational risks involved in subsistence fishing. This is in addition to the economic and environmental impacts on the productivity and quality of fishing production, which are a direct consequence of the dredging works and the new navigation and anchoring norms established and imposed by the state.

Suspended matter and nutrient gradients of a small-scale river plume in Sepetiba Bay, SE-Brazil

Coastal river plumes represent one of the final stages of material transport across the land-sea interface. Most studies, however have focused on the behavior of medium to large sized river plumes of coastal-shelf waters, whereas small sized river plumes acting within estuaries have been neglected. This study addressed the behavior of suspended particulate matter (SPM), dissolved inorganic nutrients (DIN, DIP and DSi) and Chlorophyll a (Chl. a) of a small sized river plume derived from the closely lain São Francisco and Guandú river channels, set in the Sepetiba Bay estuary, SE-Brazil. Two surface water sampling campaigns were conducted, one in January 2003 (humid summer conditions) and the other in June 2003 (dry winter conditions). On both occasions, the plumes dispersed in a SE direction towards the inner portion of the bay. The "wet" event plume was more turbid, nutrient rich and dispersed beyond nearshore waters, whereas the "dry" event plume proliferated as a narrow, less turbid and more nutrient poor film alongshore. Both exhibited a marked degree of patchiness, induced by the differential input of materials from the river sources and resuspension processes from the shallow nearshore bottom. The São Francisco river channel was the main source of freshwater, SPM and nutrients, except for ammonia (NH4+-N) derived from domestic effluents of the Guandú river. The mesohaline portion of the estuarine mixing zone of the plumes behaved as a slight source for SPM, DSi and DIP, due to bottom resuspension processes. N:P molar ratios ranged between 80:1 and 20:1 along the estuarine gradient, being higher in the summer than in the winter event, indicating that DIP was the potential nutrient limiting primary production. Chl. a concentrations increased at the outer premises of the plume, suggesting that the short residence times and turbidity of the plume waters, hampered primary production nearshore, particularly during the summer occasion...

A extensão, forma e as concentrações da matéria das plumas de pequena escala geradas pelos canais dos rios São Francisco e Guandu, se diferenciaram consideravelmente entre os eventos de alta e baixa descarga. A pluma durante o evento de alta descarga apresentou maior potencial de fertilização da parte central interna da Baía de Sepetiba, enquanto a pluma de baixa descarga fluvial reteve materiais próximo da costa em área rasa. As plumas foram impactadas por múltiplas fontes de materiais, incluindo o aporte lateral fluvial e os sedimentos do fundo. A baixa profundidade da área foi responsável pelo acoplamento nítido da água e do sedimento. O bombeamento da maré com, provavelmente, o atrito no fundo gerado pelo fluxo fluvial, foram responsáveis pela ressuspensão de matéria em suspensão e a liberação de nutrientes dos sedimentos superficiais. As plumas apresentaram um desacoplamento nítido entre as zonas de turbidez e a clorofila, e um acoplamento entre as zonas de turbidez e de mistura estuarina, geralmente não observado em plumas de médio a grande porte que se proliferam na costa e plataforma continental.

Habitat selection by anchovies (Clupeiformes: Engraulidae) in a tropical bay at Southeastern Brazil

Distribution of anchovies (Clupeiformes, Engraulidae) was described in the Sepetiba Bay, a coastal area of Southeastern Brazil, to assess eventual mechanisms of habitat selection. Two fish sampling programmes were accomplished; one using beach seine (1998/2000) to catch juveniles in sandy beaches, and the other, using seines (1999/2000) to catch adults in deeper bay areas. Six species representing 4 genera were recorded: Anchoa tricolor, Anchoa januaria, Anchoa lyolepis, Cetengraulis edentulus, Engraulis anchoita and Lycengraulis grossidens. Anchoa tricolor and A. januaria were the most abundant species, with the former peaking in the outer bay, while the latter peaking in the inner bay. Adults A. tricolor are target of heavy commercial fisheries in the bay during Spring-Summer, while E. anchoita, an abundant species in the continental shelf, was occasionally caught in large numbers during the Autumn. The habitat selection, by using two different bay areas, was developed by the two most abundant species, a probable mechanism to enable their coexistence.

A distribuição de manjubas (Clupeiformes, Engraulidae) foi descrita na Baía de Sepetiba, uma área costeira do Sudeste do Brasil, para determinar eventuais mecanismos de seleção de habitat. Dois programas de amostragem foram realizados; um usando arrasto de praia (1998/2000) para captura de juvenis, e outro, usando arrasto de fundo (1999/2000) para captura de adultos. Seis espécies representadas por quatro gêneros foram capturadas: Anchoa tricolor, Anchoa januaria, Anchoa lyolepis, Cetengraulis edentulus, Engraulis anchoita e Lycengraulis grossidens. Anchoa tricolor e A. januaria foram as espécies mais abundantes, com a primeira ocorrendo principalmente na zona externa da baía, enquanto a segunda com maior abundância na zona interna. Adultos A. tricolor são alvo de intensas pescarias comercial na baía durante a Primavera-Verão, enquanto E. anchoita, uma abundante espécie na plataforma continental, foi ocasionalmente capturada em grande numero durante o Outono. A seleção de hábitat, através do uso de diferentes áreas da baía, foi desenvolvida pelas duas espécies mais abundantes, um provável mecanismo para permitir a coexistência.