Size and dry weight of main zooplankton species in Bariri reservoir (SP, Brazil)

Ej González,Jg Tundisi,Matsumura-Tundisi Matsumura-Tundisi

doi:10.1590/s1519-69842008000100010

Abstract

In order to generate a database for secondary production studies in the São Paulo State (Brazil) reservoirs, the size and dry weight of 13 sooplankton species from Bariri reservoir (middle Tietê River) were determined. Diameter and dry weight of eggs from some cladoceran and copepod species were also determined. Sizes varied from 108.6 microm (Keratella tropica) to 2488.6 microm (females of Argyrodiaptomus azevedoi), while dry weights varied between 0.025 microg (K. tropica) and 51.250 microg (females of A. azevedoi). Egg diameters varied between 75.0 microm (Mesocyclops ogunnus) and 171.8 microm (Ceriodaphnia silvestrii), while egg dry-weights varied between 0.074 microg (Acanthocyclops robustus) and 0.865 microg (Bosmina hagmanni). Size and dry weight distribution of the zooplanktonic organisms was not linear in the bariri reservoir.

Highlights

Zooplankton density, expressed as number per area or volume units, does not necessarily provide accurate information about community biomass, because zooplankton consists of a great variety of groups or animal species of a large size range (Matsumura-Tundisi et al, 1989)
There are many studies which register the dry weight of zooplankton from temperate ecosystems (Masundire, 1994), but there are few articles concerning the zooplankton biomass for tropical freshwaters (Matsumura-Tundisi et al, 1989; Infante et al, 1990; Masundire, 1994; Melão and Rocha, 2004; Sendacz et al, 2006)
Comparisons showed four homogeneous groups: N. iheringi and C. silvestrii eggs showed the biggest diameter and no significant differences between them; egg diameters of N. iheringi specimens were different from the rest of the analyzed eggs; C. silvestrii eggs showed no significant differences with the B. hagmanni and N. evaldus egg diameters; and eggs from N. evaldus showed no significant differences with N. cearensis eggs, which showed significatively higher egg diameters than the cyclopoid copepod (A. robustus and M. ogunnus) eggs

Summary

Introduction

Zooplankton density, expressed as number per area or volume units, does not necessarily provide accurate information about community biomass, because zooplankton consists of a great variety of groups or animal species of a large size range (Matsumura-Tundisi et al, 1989). The biomass of the zooplankton species is an important and necessary parameter to calculate the secondary production of this community (Melão and Rocha, 2004). The determination of zooplankton size is an important tool for building the size – weight regressions, which are useful when only size data is available. Due to these reasons, estimation of zooplankton size and dry weight constitutes an important contribution for the study of trophic-web structure in aquatic ecosystems, considering its relationship with the trophic status of the water bodies (Rocha et al, 1995; Pinto-Coelho et al, 2005)

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Results

Conclusion