Variação espacial e sazonal da produção primária microfitobêntica em uma planície entremarés subtropical, Baía de Paranaguá, Paraná - Brasil<p>doi: 10.50007/2178-4574.2008v37p19

Abstract

RESUMOA produção primária e a biomassa microfitobêntica foram avaliadas ao longo do gradiente de energia ambiental da planície entremarés da Ilha Rasa da Cotinga, setor euhalino da Baía de Paranaguá, durante quatro marés de quadratura do outonoinverno de 1996 e da primavera-verão de 1996/1997. Os oito experimentos in situ foram realizados com uso de câmaras bênticas e a produção primária foi calculada com base na variação do oxigênio dissolvido, em duas câmaras translúcidas e duas opacas. A hipótese nula de que não há diferença significativa entre os períodos amostrados (sazonalidade) e entre o gradiente de energia ambiental da planície entremarés (espacialidade) foi testada utilizando-se ANOVAs uni e bifatorial. A radiação fotossinteticamenie ativa -RFA foi considerada para cada sítio amostral. A biomassa foi maior no outono-inverno do que na primavera-verão, enquanto a produção primária e a RFA foram maiores na primavera-verão. Todos os descritores apresentaram um gradiente crescente da região inferior, acima da isóbata de I metro, para a região mediana e superior da planície. A importância desta comunidade para o ecossistema estuarino da Baía de Paranaguá foi discutida.Palavras-chave: biomassa microfitobêntica, radiação fotossintéticamente ativa, Ilha Rasa da Cotinga.

Microphytobenthic biomass on a subtropical intertidal flat of Paranaguá bay (Southern Brazil): spatio-temporal distribution and the influence of environmental conditions

“…The sediment is an important site for the degradation of organic matter, including the microphytobenthic biomass. However, chlorophyll-a was twice as high as phaeophytin-a during this study, which suggests that the increment of microphytobenthic biomass more than compensated for the effects of the degradation processes and resulted in the good physiological condition of this community (FORD and HONEYWILL, 2002). Spatially, the general seaward increase in the chlorophyll-a:phaeophytin-a ratio suggested a preferential accumulation of phaeopigment at the sheltered sites of the middle and upper flat.…”

“…The lower hydrodynamics of the middle and upper flat areas favour the deposition of fine suspended matter and the stability of the sediment, both important factors for microphytobenthos development. Furthermore, the microphytobenthic primary production was higher at the MW and HW sites than at the LW site and this difference was determined mainly by incident radiation (FONSECA et al, 2008). The constant scouring of the sediment, including microphytobenthic cells and the low light incidence might explain the lower microphytobenthic biomass at the LW, as observed by others (UNDERWOOD and PATERSON, 1993;BLANCHARD et al, 2000).…”

“…These minima may have been favoured by the heavy rainfall -of around 103 mm -which occurred during the month preceding this sampling. Under such conditions, the seston concentration increases in surface water, diminishing the photic zone (BRANDINI and REBELLO, 1990;MIZERKOWSKI et al, 2012) and limiting the development of the microphytobenthos (FONSECA et al, 2008).…”

“…During high tides, the depth of the water column above the intertidal flat varies from 1 to 2 m. Therefore, at high tide, the light that reaches the sediment on the upper and middle flat is more intense than that on the lower flat. This is an important factor in the spatial differences found in the microphytobenthic primary production measured along this flat (FONSECA et al, 2008).…”

“…Along the intertidal flat, different zones are characterised according to the hydrodynamics, tidal range, slope and habitat sequence (REISE, 1985;DYER et al, 2000). Consequently, the upper, middle and lower flats can be distinguished by sediment granulometry and composition that are reflected in the biological community and related biochemical processes MUROLO et al, 2006;FONSECA et al, 2008).…”