RED EUGLENOID BLOOMS: A BIOMARKER OF ENVIRONMENTAL IMPACT IN FLOODED RICE FIELDS

Abstract

The nutrient load introduced into flooded rice fields is one of the main factors
that impact this type of ecosystem, contributing to the development of blooms
of pigmented euglenoids. This study was carried out to investigate the
behavior of red euglenas, a group of pigmented euglenoids, forming blooms in
this type of environment. Sedimented spores in the soil after water drainage,
as well as water samples from vegetative cells in living blooms were collected.
The collected material was inoculated into a culturing medium for microalgae
and incubated for three weeks. The cultures grown in nutrient medium were
used for morphometric analysis to identify the species. In order to characterize
the water environment, chemical and physical parameters were also
monitored "in situ". The results indicated Euglena sanguinea Ehr. as the
bloom-forming species and nitrogen as a key element in the behavior of this
species in this type of ecosystem. It was suggested, however, that more studies
are needed to indicate the use of red euglenas as biomarkers of nitrogen
overload in flooded rice fields.