CHOICE OF MACROPHYTE SUBSTRATE IN THE USE OF DIATOMS AS INDICATORS OF POND WATER QUALITY ASSESSMENT: PRELIMINARY DATA ON THE CASE OF ALALAY POND (COCHABAMBA, BOLIVIA)

^{1, 2, 3}Eduardo A. Morales & ^{1, 3}Sinziana F. Rivera
¹Herbario Criptogámico Universidad Católica Boliviana, Carrera de Ingeniería Ambiental, Casilla de Correos 5381, Cochabamba, Bolivia.
²Patrick Center for Environmental Research, The Academy of Natural Sciences, PA 19103-1195, Philadelphia, USA.
³Centro de Diagnosis de la Calidad Ambiental, Cochabamba, Bolivia. Calle Andrés Uzeda No. 0358. Cochabamba, Bolivia.

Abstract

Alalay Pond is a 230-hectare, shallow aquatic ecosystem within Cochabamba, the third largest city in Bolivia. With the aim to determine the suitability of epiphytic diatoms for water quality assessment in the pond and to choose a substrate that would hold a representative bioindicator epiphytic community, the macrophytes Schoenoplectus californicus subsp. tatora (Kunth) T. Koyama, Typha dominguensis Pers., Myriophyllum verticillatum L. and Azolla filiculoides Lam. were selected and differences in diatom community composition and structure were tested. Diatoms were collected during four sampling campaigns in the March-September, 2011 period, from three stations contiguous to the pelagic zone and prepared for analysis using standard, internationally used protocols. In all, 27 samples were collected from which 28 taxa characteristic of eutrophic environments were identified and 17 others could not be assigned names from the literature. Although many of the species are shared among sampling sites, the epiphytic communities developing at each station were different in structure and composition. Although, there are marked temporal variations in community features on each of the macrophytes, Shannon-Wiener and Pielou indexes, as well as canonical correspondence analysis, showed no marked differences within a single campaign and station among the 4 macrophytes. Shifts in structure and composition are denoted less commonly by species replacement and more often by changes in percent relative abundance of dominant and rare species. Very few species are restricted to a station or seem to show strong preference for a particular substrate. Taking into account growth, structural and ecological characteristics, as well as some phenological features of the macrophytes, S. californicus subsp. tatora and T. dominguensis are the most suitable substrates for water quality assessments in the pond. As demonstrated by multivariate analyses, among-site and time-scale differences in community composition and structure were attributable to alkalinity, chemical oxygen demand (COD), ammonium-nitrogen, conductivity and dissolved oxygen (DO). More frequent sampling, diversification of substrates and extending the study for a longer period are recommended to establish a monitoring program during any future restoration of the pond.

Full text .PDF