Ecologia das comunidades zooplanctônicas costeiras em frente à foz do rio Amazonas: uma abordagem sob o prisma de metacomunidades.

Abstract

Recent advances in theoretical ecology have reorganized the understanding of the relationship between regional and environmental processes on changing the composition and structure of local communities. Zooplankton represents the link in the transfer of energy and particulate organic debris to the other trophic levels of consuming organisms, including species of economic importance such as mollusks, crustaceans and fish. Changes in the planktonic community cause profound structural changes at all trophic levels of the aquatic ecosystem. Due to its dynamic character, high reproduction rates, loss and rapid response to physicochemical changes in the environment. Interactions between Amazonian discharge, wind action and surface ocean currents control pelagic processes in the Brazilian North Coast, and their influence on physicochemical dynamics and patterns, as well as on planktonic biomass on the Amazonian Platform and adjacent oceanic area. The present study covers the area of the Amazon Continental Shelf (PCA), between the mouth of the Amazon River and the mouth of the Pará River, starting from the coastal zone of Marajó Island until near the breaking of the Continental Shelf, covering a radius of approximately 300 km from the coast. Two collection cruises were conducted in April 2013 (Cruise 1 - C1) and October 2013 (Cruise 2 - C2) with stations approximately 10 to 20 miles apart. In each season hydrological variables such as temperature, salinity and chlorophyll-a concentration were collected through a CTD. A total of 107 zooplankton taxa were identified in the 2 cruises conducted in the study area, consisting of 70.1% Holoplanktonic organisms and 29.9% Meroplanktonic organisms. The most abundant group was the copepod, with 60 taxa identified among order, family, genus and species. The density of the identified taxa were well differentiated between the months of collection, the density of meroplankton that in October was twice higher than April. The most common copepod taxa in the two periods studied were: Nauplii (unidentified), Oithona nana, Paracalanus parvus and Subeucalanus pileatus, indicating that these taxa are present throughout the Platform regardless of the time of year. The organisms with higher densities in the total species matrix were Bivalves and Clausocalanus furcatus, with 99,000 and 69,000 ind.m-3 respectively, and Sagitta spp. (48,000 ind.m-3), Gastropoda (46,000 ind.m-3) and Parvocalanus crassirostris, (44,000 ind.m-3). The area has a large seasonal variation in the biodiversity and density of its zooplankton community.