Xylem 6-Series Multiparameter - Manual (Page 275)

Principles of Operation Section 5
YSI Incorporated Environmental Monitoring Systems Manual 5-37
5.17 PHYCOERYTHRIN-CONTAINING BLUE-
GREEN ALGAE
Introduction
Blue-green algae (BGA), also known as cyanobacteria, are common forms of photosynthetic bacteria
present in most freshwater and marine systems. BGA contain a unique set of accessory pigments of the
phycobiliprotein family that serve a variety of roles for the organism. The primary phycobilin pigments are
phycocyanin (PC) and phycoerythrin (PE) and both happen to have strong fluorescent signatures that do not
interfere significantly with the fluorescence of the chlorophylls. This allows for the in vivo detection of
BGA with minimal interference from other groups of algae. BGA with the PC phycobilin pigment can be
found in both fresh and brackish water environments while BGA with the PE phycobilin pigment is usually
found only in brackish or marine environments.
The monitoring of BGA is of growing interest in a number of research and monitoring fields and of
particular interest is the monitoring of BGA as a public health risk in coastal areas and as an important
primary producer is some oceanic environments. As the rates of eutrophication accelerate due to human
impacts on aquatic ecosystems, harmful algal blooms (HABs) are becoming a more common problem. In
the case of cyanobacterial blooms, some species can produce toxins generally referred to as cyanotoxins
that can cause health risks to humans and animals.
The YSI 6132 sensor, when used in conjunction with YSI 6-series multiparameter sondes, is designed to
detect and monitor the presence of PE-containing BGA in order provide an early warning system for
potentially hazardous conditions as well as thoroughly characterize aquatic environments where PE-
containing BGA exist.
The determination of BGA as an indicator of water quality has historically been carried out using either (a)
extraction of BGA samples followed by analysis of the extracts by fluorometry, HPLC, or a combination of
the two techniques or (b) the automated or manual counting of actual BGA cells in the known volume of
sample water. While accurate, these types of analytical techniques usually are done as part of a “spot
sampling” protocol and almost never yield continuous data with regard to BGA content. The methods are
time-consuming and usually require an experienced, efficient analyst to generate consistently accurate and
reproducible results. Most importantly, the methods do not lend themselves readily to continuous
monitoring of PE-containing BGA, since the analysis of a collection of samples taken at reasonable time
intervals, e.g., every hour, would be extremely tedious.
YSI has developed the YSI 6132 sensor for the determination of PE-containing BGA in spot sampling and
continuous monitoring applications. It is based on an alternative method for the measurement of BGA in
general which overcomes the disadvantages of discrete laboratory methods outlined above, albeit with the
potential loss of accuracy. In this procedure, PE-containing BGA are measured in vivo, i.e., without either
disrupting the cells as in the laboratory extractive analysis procedure or using cell counting techniques as
described above. The YSI 6132 sensor is designed for these in vivo applications and its use allows the
facile collection of large quantities of data in either spot sampling or continuous monitoring applications. It
is important to remember, however, that the results of in vivo analysis will almost certainly not be as
accurate as those from the certified extractive analytical or cell counting procedures.
The limitations of the in vivo method are outlined below and should be carefully considered before making
BGA determinations with your YSI sonde and sensor. Some of the sources of inaccuracy can be
minimized by combining the data from the YSI 6132 with data from standard laboratory analysis of a few
samples acquired during a sampling or monitoring study. However, the in vivo studies will never replace
the standard procedure. Rather, the estimates of BGA concentration from the easy-to-use YSI PE Probe are
designed to complement the more accurate (but more difficult to obtain) results from more traditional
methods of BGA determination. The YSI 6132 sensor is ideally suited for the monitoring the relative
changes (temporally or spatially) in the PE-containing BGA population.