Navegando por Assunto "Tropical estuary"

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Acesso aberto (Open Access)
Distribuição espaço-temporal da comunidade zooplanctônica no estuário do Taperaçu (Bragança-Pará-Brasil): biomassa e produção secundária das principais espécies de copépodos
(Universidade Federal do Pará, 2016-10-25) LEITE, Natália da Rocha.; MONTES, Manuel de Jesus Flores; http://lattes.cnpq.br/2999296486918048; COSTA, Rauquírio André Albuquerque Marinho da; http://lattes.cnpq.br/4504677939464624; https://orcid.org/0000-0003-4461-3936
This study aimed to determine the composition and distribution of zooplankton in the estuary Taperaçu evaluating, in temporal and spatial scales, the contribution of the main species of copepods for biomass and production in terms of organic carbon in the environment under study. Therefore, samples were taken bimonthly (zooplankton and hydrologic variables) from June 2012 to June 2013, in three fixed stations located along the estuary, totaling 45 samples. The zooplankton community was apparently homogeneous. With regard to biological attributes, significant variations related to circadian cycles (day/night) and tidal periods (flood/ebb) were not detected. High values of abundance of Paracalanus quasimodo, Labidocera fluviatilis and Pseudodiaptomus marshi were observed. The absence of a nichtemeral and tidal patterns, was possibly related to the morphodynamic characteristics of the estuary Taperaçu, such as the presence of sandbanks in its central portion, the absence of a river discharge, the small catchment area, low depths and strong tidal currents, which facilitate the processes of horizontal and vertical mixing of the water column. When analyzed on a monthly and spatial scale, it was observed the influence of seasonal periods on the dynamics of these organisms, these being directly related to variations in salinity, turbidity and chlorophyll-a concentrations. The zooplankton community was dominated by copepods, especially Acartia tonsa (22,230.9±46,145.7 ind.m ), Acartia lilljerborgi (4,011.6±10,326.5 ind.m -3 ), P. quasimodo (9,270.7±17,593.3 ind.m -3 ), P. marshi (3,267.3±4,565.1 ind.m-3) and Oithona oswaldocruzi (30,221.9±28,328.4 ind.m-3-3), together with Oikopleura dioica (15,284.6±26,060.6 ind.m-3). The average diversity of species ranged from 2.0±0.6 bits.ind-1 to 3.8±0.4 bits.ind-1, while the evenness ranged from 0.5±0.1 to 0.7±0:03. Overall, the temporal variability (monthly and temporal) and spatial observed in the structure and dynamics of zooplankton population was mainly related to fluctuations in precipitation rates, which directly affect the salinity of the water and consequently the abundance of these organisms. In addition, it was also concluded that the presence of typically marine species such as P. quasimodo and O. dioica may be related to the significant increase in salinity as a result of reduced rainfall in 2012. Biomass and production A. tonsa and A. lilljeborgi were directly related to the local rainfall since, A. tonsa showed high values throughout the period, not only in the rainy season as previously observed in this same estuary. The immature stages (C1-C5) of A. tonsa were the dominant forms, especially the C4 stage (839.88±1518.80 mgC.m), while for A. lilljeborgi the highest values were obtained for adults (1,347.84±499.95 mgC.m-3). The obtained rates of secondary production were higher than those described for other estuaries located around the world, and these results are associated with the high temperatures recorded during the year as well as the observation of water rich in nutrients and particulate organic matter derived from adjacent to mangroves Taperaçu. In general, the results indicate that the influence of climate changes on the hydrological variables especially temperature, salinity, as well as the concentration of chlorophyll-a were the main responsible for the dynamics of mesozooplanctônicas species identified in the estuary of Taperaçu.
Acesso aberto (Open Access)
Modelagem matemática do sistema estuarino dos rios Mojuim e Mocajuba (Pará-BR)
(Universidade Federal do Pará, 2016-02-29) SANTOS, Arthur Souza dos; ROLLNIC, Marcelo; http://lattes.cnpq.br/6585442266149471
The estuaries of Mojuim and Mocajuba rivers are located in the eastern sector of the Amazon Coastal Zone and represent a peculiar and complex environment. They are connected by several channels and are receive influence of the Bay of Marajó and the Atlantic Ocean. The following research aims to implement a hydrodynamic model based on a flexible grid on the of Mojuim and Mocajuba rivers estuarine system; and to analyze the hydrological and hydrodynamic characteristics of the upper estuary of these rivers. The methodology involves the use of D-Flow Flexible Mesh pack a get simulate hydrodynamics patterns into the domain that covers the Mojuim Mocajuba rivers, the canals connecting these rivers, part of the mouth of the Bay of Marajó and the adjacent tidal flats. It was also performed an "in situ" systematic data collection, in which parameters of flow, salinity, turbidity and water level were analyzed during a tidal cycle in sites located at the upper estuary of Mojuim and Mocajuba rivers. In the Mojuim river two seasonal campaigns were made in two different sites and in the Mocajuba river only one campaign were made in the rainy season, however, a tide station was installed in this location that operated for 25 weeks. Part of the sample data were used as input to the hydrodynamic model. The upper estuary of Mocajuba river presented a macrotidal regime with maximum height of 5.8m recorded. In the Mojuim river, a gradual attenuation of the tidal wave is noticeable and, in the collection point and in the upper estuary a one-way flow discharge during the rainy season was observed. A different hydrodynamic pattern between the two rivers was also observed, with ebb speed more intense than floods and their hydrological properties directly influenced by the tide fluctuation. Finally a hydrodynamic model in flexible grid was implemented and calibrated in the researched area, where initial and boundary conditions were assigned, as well as adjustments to the border forcing. The model generated a good representation of the estuary conditions, showing acceptable tidal and hydrodynamic pattern when compared with the "in situ" measurement, once the error between the measured data and modeled data related to the water level were less than 5%, and errors related to transportation are lower than 15%.