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

Abstract

A B S T R A C TSeasonal and spatial dynamics of the microphytobenthic biomass on a subtropical intertidal sand flat (25°32'S; 48°24'W) was investigated monthly from September 1995 to July 1996. Chlorophyll-a and Phaeophytin-a contents, temperature, salinity, inorganic nitrogen and phosphate pore water concentrations and sediment characteristics were assessed in the upper (HW), middle (MW) and lower (LW) sections of the flat. Microphytobenthic biomass content showed a conspicuous seasonal and spatial gradient. Higher chlorophyll-a contents were registered in the HW section of the tidal flat (from 11.78 µg.gsed -1 to 38.18 µg.gsed -1) decreasing towards the LW section (from 6.23 µg.gsed -1 to 18.23 µg.gsed -1 ). Microphytobenthic seasonality was determined mainly by turbulence of the water column, which was influenced by atmospheric events. The sediment properties and nutrient concentrations had a significant effect on the spatial and seasonal distribution of pigments on the intertidal flat. R E S U M OA dinâmica sazonal e espacial da biomassa microfitobêntica em uma planície arenosa intermareal (25º32'S; 48º24'W) foi investigada mensalmente de setembro de 1995 a julho de 1996. A concentração de clorofila-a e feofitina-a, a temperatura, salinidade, concentração de nitrogênio inorgânico e fosfato na água intersticial, além das características do sedimento, foram inferidas na região superior (HW), mediana (MW) e inferior (LW) da planície. A biomassa microfitobêntica apresentou gradientes sazonal e espacial bem definidos. Maiores concentrações de clorofila-a foram registradas na região superior da planície entre marés (HW, de 11.78 µg.gsed -1 até 38.18 µg.gsed -1 ), decrescendo em direção a região inferior da planície (LW, de 6.23 µg.gsed -1 a 18.23 µg.gsed -1 ). A sazonalidade microfitobêntica foi determinada principalmente pela turbulência da coluna de água, influenciada pelos eventos atmosféricos. As propriedades do sedimento e as concentrações de nutrientes foram significantes para a distribuição espacial e sazonal dos pigmentos na planície entre marés.

A Doubling of Microphytobenthos Biomass Coincides with a Tenfold Increase in Denitrifier and Total Bacterial Abundances in Intertidal Sediments of a Temperate Estuary

“…Estuarine MPB biofilms can be extremely variable in time (seasonality) and space (from cm to km), with complex interactions of biotic and abiotic parameters responsible for their patchiness [ 68 ]. Tidal height, sediment type and hydrodynamism [ 69 , 70 ], and intraspecies competition [ 71 , 72 ] are unlikely causes as both samples, from the same sediment type, were taken at the same tidal height and both biofilms contained the same MPB species. However, grazing of MPB, alone or with bacteria, by higher organisms such as grazing benthic deposit feeding invertebrates like harpacticoid copepods [ 73 ], (bacterivorous) nematodes [ 74 , 75 ], polychaetes and bivalves [ 76 ] is a plausible factor.…”