Abstract
Between December 17th and 18th of 1998the Soloncy Moura Research Vessel (CEPSUL/ IBAMA) was stationed for 24 hours at the eastern margin of the Arvoredo island, inside of the Arvoredo Biological Marine Reserve (27°19,6'-27°8,6' S and 48°27,1'-48°9,1' W). During this time the temperature and salinity profiles were obtained using a CTD, and water samples were collected for ammonium determination. The biomass in wet weight of the size classed zooplankton, was collected by vertical trawls in 3 strata in the water column. Incubations were executed at 5 meters depth in DBO flasks, of the Salpidae Thalia democratica Oozooids and the phytoplankton collected in the same place. The filtration rates were estimated by the increase of feopigments and growth rates by blastozooids liberation. The temperature and salinity data measured along the 24 hours didn’t show a significant temporal variation, with the Tropical Water occurring at surface and the Subtropical Water below 20 meters depth. The zooplankton biomass presented a clear vertical migration behaviour, with larger concentrations in the intermediary stratum (10 to 20 m) during the day and with a displacement for the superficial stratum (0 to 10 m) at sunset. The ammonium concentration exhibited a similar behaviour in the water column indicating probable regeneration processes and bioconvection of this nutrient. The species Thalia democratica was the dominant organism in the fraction larger than 1000 µm and it was responsible for the highest zooplankton biomass in the samples. The incubation experiments of this species presented an average filtration rate of 176.4 mL.day-1 and growth rate of blastozooids from 8 to 10.3% in length per hour.
Highlights
Between December 17th and 18th of 1998the Soloncy Moura Research Vessel (CEPSUL/ IBAMA) was stationed for 24 hours at the eastern margin of the Arvoredo island, inside of the Arvoredo Biological Marine Reserve (27°19,6'-27°8,6' S and 48°27,1'-48°9,1' W)
The ammonium concentration exhibited a similar behaviour in the water column indicating probable regeneration processes and bioconvection of this nutrient
The species Thalia democratica was the dominant organism in the fraction larger than 1000 μm and it was responsible for the highest zooplankton biomass in the samples
Summary
Entre os dias 17 e 18 de dezembro de 1998 foi realizado um fundeio na margem leste da ilha do Arvoredo, dentro da Reserva Biológica Marinha do Arvoredo (27o19,6'-27o8,6' S e 48o27,1'-48o9,1' W), com o Navio de Pesquisa Soloncy Moura (CEPSUL/IBAMA) (Fig. 1). Os arrastos foram executados a cada 4 horas e em três estratos da coluna de água (0-10, 10-20 e 20-35 m) sendo o material coletado fixado em formol a 4 %. Para as estimativas da taxa de filtração e crescimento da salpa Thalia democratica foram realizadas incubações de 12 horas, em frascos tipo DBO de 300 mL, de Oozooides com estolão e blastozooides em desenvolvimento. As taxas de filtração foram estimadas pelo incremento de feopigmentos medidos por cromatografia líquida de alta eficiência (CLAE) segundo método apresentado para amostras de água. As taxas de crescimento de Thalia democratica foram estimadas pela variação no número e tamanho de blatozooides liberados durante o período de incubação a partir da separação e fixação em formol a 4 % dos organismos presentes nos frascos no fim dos experimentos. Os pesos dos organismos foram estimados mediante a relação comprimento X peso seco da espécie (Fig. 2)
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