Composição e distribuição do zooplâncton, em um transecto na área continental norte Brasileira (Amazônia-Brasil)

Abstract

Zooplankton has important for the transfer of primary energy of phytoplankton and bacterioplankton to higher trophic levels, has responsible for nutrient recycling and distribution of organic matter in the water column, are relevant to the trophic web structure and ecological balance, which are essential to coastal-marine ecosystems. The main objective of this study was to describe the mesozooplankton community in a perpendicular transect to the coast, positioned coast-ocean, on the Amazon Continental Shelf (PCA) in terms of frequency of occurrence, density, relative abundance and diversity of the main groups in two oceanographic cruises during the dry and wet season and to evaluate the possible relationships between zooplankton abundance and abiotic parameters in the dynamics of mesozooplankton communities. The collection of abiotic data was performed simultaneously the zooplankton collection, with the aid of conical-cylindrical network (300µm mesh opening) in oblique trawls in a transect with 6 sampling stations in the PCA during October 2014 (dry period) and January 2015 (rainy season) on the Amazon Continental Shelf, preservation was carried out on board with 4% formaldehyde, buffered with sodium tetraborate (20g / L). In the dry and wet season, the temperature changed slightly around the average of 28ºC ± 0.32 and 28ºC ± 0.10 respectively., the salinity ranged from 17.80 to 37.71 in the dry season, in the wet season from 10.38 to 37.21, the chlorophyll-a in the dry period had an average of 7.40 μg.L-1 and in the wet season, the average was 8.28 μg.L-1. Was identified (51) taxa, counted from the infrageneric, of which thirty-three (33) are from Copepoda. Regarding the density there was no significant difference (p <0.05) between the averages of the two periods, the species diversity in the dry period, in general, was considered low (between 2.0 and 1.0 bits.ind-¹) and in the rainy period. was considered average (between 2.0 and 3.0 bits.ind-¹). The lowest values were found near the coastal regions. In the dry season, there was an alternation between the abundant groups punctually, Copepoda and Decapoda were considered abundant in most seasons analyzed for the rainy season. In the dry period, four rates were considered too frequent, ten rates were considered frequent and twenty-seven rates were rare. In the wet season, seven rates were very frequent, as frequent nine rates and forty-four rates as rare. Has been concluded that in the area was analyzed, there was a typical zonation of coastal-ocean environments, especially in the wet season, in density, abundance, diversity, but without direct interference of environmental parameters.