STRIVE - Environmental Protection Agency

1 Introduction
Occurrences of harmful algal blooms (HABs) have
increased since the 1970s in marine and freshwater
environments worldwide (Hallegraeff 2004). In
continental waters, eutrophication has usually been
associated with the development of high biomass
cyanobacterial blooms. Those dominated by toxic
species have caused a variety of ecological disruptions
and present serious threats towards animal and
human health (Mur et al. 1999). Poisoning incidents of
livestock, wildlife, domestic animals and humans have
been documented after exposure to or consumption
of water contaminated by toxins produced by
cyanobacteria species – compounds also referred to
as ‘cyanotoxins’. The range of symptoms in humans
includes gastroenteritis, fevers, vomiting, rashes, liver
and kidney damage, respiratory irritation but also primary
liver cancer and death (Codd et al. 2005). Intoxications
usually derive from consumption of contaminated
drinking water or from contact during recreational
activities. Cyanotoxins show a wide variety of chemical
forms and have been grouped into several classes
according to their structure and biological activity. The
most commonly encountered cyanobacterial toxins are
the hepatotoxic microcystins, which are produced by
several genera, including, non-exhaustively, planktonic
forms of Anabaena, Microcystis, Oscillatoria, Nostoc
or Anabaenopsis. Structural variability among toxin
variants for each class confer cyanotoxins with a wide
range of toxicity, the most acute forms constituting
potential problems for water body and health managers
worldwide.
Cyanobacteria are ubiquitous components of
phytoplankton assemblages in aquatic environments.
They exhibit a variety of sizes and shapes and have
traditionally been classified into five groups according
to morphological criteria (Mur et al. 1999). The
introduction and application of molecular biology
methodologies have affected the perception of
relationships amongst cyanobacterial taxonomic
groups. Phylogenetic studies based on rDNA analysis
have permitted assessing the evolution of different
morphotypes and determining their lineages, showing
that both polyphyletic and monophyletic groups,
N. Touzet (2008-FS-EH-3-S5)
1
interspersed in various clades, existed among
cyanobacteria (Moore et al. 1998, Wilmotte & Herdman
2001, Abed et al. 2002). The genetic characterisation
of cultured cyanobacteria strains has also provided the
basis for designing taxa-specific molecular markers for
the discrimination of morphologically similar species
in both culture and environmental samples (Zehr et al.
1997, Rudi et al. 1998, Beard et al. 1999, Iteman et al.
2000, Tillet et al. 2001, Zeidner et al. 2003).
The dynamics of natural cyanobacteria populations
have been studied extensively in many countries
due to the potential noxious effects they can elicit.
However, only few studies have investigated their
spatial and temporal distributions at mesoscale levels,
over extensive geographic areas including several
water bodies. Typical limitations to such studies
include sampling, methodological, time and budgetary
constraints. However, the application of regional
approaches for lake water quality assessment,
monitoring and management is increasing.
Regionalisation frameworks applied to sampling
surveys can combine geographical, geological and
hydromorphological data to define contiguous spatial
regions that share similar features, the underlying
assumption being that lake characteristics within
regions are more similar than those of waterbodies
across regions (Gerritsen et al. 2000). Advances in
the field of geographic information systems (GIS) have
permitted water bodies to be placed in better context
with their geomorphologic surroundings and to include
changes in land cover and usage, which can impact
upon water quality (Aspinal & Pearson 2000). Risk
assessments based on such approaches and new
technologies can enable regulatory and managing
bodies to take informed decisions for the development
of guidelines for watershed management. The design
and application of sampling plans have seldom been
considered for aquatic microbial ecology studies. This
limitation in mind, Catherine et al. (2008) applied a
sampling strategy based on regional attributes to
study the distribution of cyanobacteria in lakes within a
geographic area subjected to various land use around
Paris, France.