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Acta Nova

On-line version ISSN 1683-0789

Abstract

MORALES, Eduardo A.; RIVERA, Sinziana F.; VILDOZO, Luis H.  and  POL, Anelisse. Harmful algal bloom (HAB) produced by cyanobacteria in Alalay Shallow Lake, Cochabamba, Bolivia. RevActaNova. [online]. 2017, vol.8, n.1, pp. 50-75. ISSN 1683-0789.

We present data collected during June to August, 2016 for the harmful algal bloom (HAB) developing in Alalay shallow lake, Cochabamba Bolivia; bloom that caused the massive kill of fish and birds early in March of the same year. The bloom was continuously dominated by Arthrospira fusiformis, Anabaenopsis milleri and Aphanocapsa sp., three cyanobacteria reportedly highly toxic and which morphological and autecological adaptations, effective use of nutrients, space and light, and the ecological consequences of their physiological activities determined their prevalence in the lake. Atmospheric nitrogen fixation and the recycling of nutrients from the water column and sediments, as well as the reuse of organic matter produced by photosynthetic organisms resulted in algal densities that are seldom reported in the literature. Water chemistry shows that the lake is hypereutrophic and that it has shifted from a nitrogen to a phosphorus limitation. Multivariate analyses showed that although only about 77% of the algal abundance variance is explained by measured water chemistry variables, nitrates, total phosphorus, carbonates, sulfatos, and conductivity are the parameters explaining observed variation in algal abundance in the three selected sampling sites. Such variations confirm previous results obtained by analysis of environmental variables and diatom assemblages, showing that the three sampling points are affected differently by anthropic activities in the drainage basin. The confirmed identity of Arthrospira fusiformis and Anabaenopsis milleri, their high abundance during March and subsequent months, the features of the fish and bird kills, and the historical water chemistry data suggest that the kills were produced by cyanotoxins and not by low dissolved oxygen and presence of hydrogen sulfide, as reported in the local and national press. The results shown here have implications for the development of recuperation and management protocols, aspects that are discussed in the context of our data and reports in the literature.

Keywords : Algal blooms; bluegreen algae; Cyanophyta; cyanotoxins; harmful algae; shallow lakes; urban lakes.

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