Journal of Environmental Biology

Seasonal variations of rotifers from the high altitude

Llano reservoir (State of Mexico, Mexico)

M.E. Mu?oz-Colmenares¹, S.S.S. sarma²* and S. Nandini²

¹PCMyL, National Autonomous University of Mexico, Circuito Exterior S/N, Ciudad Universitaria, Delegaci?n Coyoac?n, Mexico City 04510,Mexico

²Laboratory of Aquatic Zoology, National Autonomous University of Mexico, Campus Iztacala, Av. de Los Barrios No.1, AP 314, 54090,

Los Reyes, Tlalnepantla, State of Mexico, Mexico

*Corresponding Author E-mail: ssssarma@gmail.com

Key words

CCA analysis

Llano reservoir

species diversity

Seasonal variations

Publication Data

Paper received : 16.05.2016

Revised received : 07.12.2016

Re-revised received : 18.01.2017

Accepted : 24.02.2017

Abstract

Aim: Llano reservoir is a high altitude waterbody and is of recreational importance in Mexico. It is also a source of revenue through fisheries. Though the reservoir was constructed nearly 6 decades ago, quantitative information on the zooplankton abundance is not available. The aim of the present study was to present data on the seasonal variations of rotifers from the high altitude waterbody Llano dam (State of Mexico) during a one year period.

Methodology: Rotifer sampling was done monthly from 5 different littoral zones for one year (August 2014 to July 2015). Eighty liters of superficial water from the reservoir were concentrated to 200 ml through a plankton net of 50?m pore size and fixed in 4% formalin. Selected physico-chemical parameters (dissolved oxygen, temperature, pH, conductivity and nutrients (NO₃^- and PO4^-3) and Chlorophyll a were also measured.

Results: Temperature varied from 10-20?C and pH 5-8. The reservoir had low turbidity (<3 NTU), nitrates (<60 ?g L^-1), phosphates (<5 ?g L^-1) and chlorophyll a (6-8 ?g L^-1). In all, 84 species of monogonont rotifers (from 18 families and 39 genera) and 13 cladoceran species (from 3 families) were recorded. Aspelta angusta, Eosphora thoa, Trichocerca insulana and Lepadella punctata are new records for Mexico. Polyarthra vulgaris had the highest frequency of occurrence (98%), followed by Trichocerca bidens (90%) and Trichotria tectractis (75%). During April, we recorded the highest density (825 ind. l^-1) of all rotifer species together, meanwhile for the rest of months, the density was low <300 ind. l^-1. Shannon-Wiener index varied from 1.0 to 4.2 bits ind. l^-1, depending on the sampling period. The Sl?deček?s Q_B/T index in this reservoir was generally 1.

Interpretation: In addition to nutrient levels, Chla and Q_B/T, the total rotifer density as a useful measure to determine the trophic status of this waterbody was explored. Our data from nutrients and total rotifer density showed that the Llano reservoir appeared to be oligotrophic

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