Influência da pluma do Rio Amazonas na distribuição da abundância dos organismos zooplanctônicos na Plataforma Continental Amazônica (Pará, Brasil)

Abstract

The objective of this work was to estimate the abundance of the main zooplankton groups in a transect perpendicular to the coast of the Amazon continental shelf, and to analyze possible relationships with the physicochemical parameters of the water. For this, the samples were collected through an oceanographic cruise held in October 2013. In this cruise were collected 6 points along a transect towards the Atlantic Ocean at distances of 23, 38, 53, 68, 83 and 120 km from the northwestern tip of the island of Marajó. For collections were made the oblique trawls, with a cylindrical-conical plankton network of fifty centimeters of mouth opening and mesh size of 200 micrometers, equipped with a mechanical flowmeter. Individuals were identified to the lowest taxonomic level through a stereoscopic loupe using specific literature. The temperature, salinity and chlorophyll parameters were measured using a CDT support (Conductivity, Temperature and Depth) type Hydrolab DS5X. Two peaks of greatest abundance were recorded, one at point 2 (53,577 ind / m³) under the influence of the Amazon plume (lower salinity and greater chlorophyll), allowing a heterogeneous food chain. And another at point 5 (49,092 ind / m³) without pen influence (higher salinity, and lower chlorophyll), being represented by 92% of copepods. The Holoplankton functional group was more abundant in relation to the Meroplankton, with the Calanoid Order being the largest abundance group (100,977 ind / m³) of the present study, representing 53% of the total abundance.