Level
Choosing the taxonomic group (e.g., fish, macroinvertebrates, etc.) should be
based on monitoring program objectives and designated use. Selection may
consider spatial and temporal variability, length of the life cycle, extent of the
home range, and level of taxonomic expertise required for analysis. Other
economics
considerations include ease of sampling, cost, known ecology of
ofimportance, or the ability of tissue to accumulate pollutants for bioassay
1986).
Advantages of monitoring more than one taxonomic group are discussed by
Plafkin et al. (1989) in the
Rapid Bioassessment Protocols for Use in
Streams and Rivers. However, monitoring more than one taxonomic group could
be redundant if objectives do not directly relate to the variables being measured.
Several taxonomic groups are reviewed and relevant sampling issues are dis-
cussed below.
Coliform Bacteria. The transmission of waterborne diseases from both PS and
Bacteria
NPS pollution continues to be a public health threat. Bacteria or other organisms
should be considered in a monitoring program for water supply, contact recre-
ation, and shellfishing where pathogens are a threat. The coliform group of
is often found with other organisms that pose a more serious risk to health.
Coliform bacteria are easily detectable and they are not generally present in
unpolluted waters (National Academy of Sciences 1977). Fecal coliform (FC) and
fecal streptococcus (FS) bacteria are found in the intestinal tract and feces of
humans and other animals and may signal the presence of a pathogen such as
(Thomann and Mueller 1987).
Compared with other organisms, bacteria are highly variable. They have a
relatively short lifespan, cells drift substantially, and cell counts can change
rapidly due to changes in water quality. Bacteria should be monitored at the point
of designated use, such as a water supply intake, shellfishing grounds, or
recreation area for the duration and frequency specified by state or local standards.
A health department should be consulted for pollutant source identification,
monitoring, or interpretation. Laboratory quality control and quality assurance is
essential for reliable coliform bacteria counts.
Explanatory variables for monitoring bacteria include: temperature, salinity,
sunlight, predation, effectsof nutrients or toxins, and time of travel, distance from
source, settling, or resuspension from sediments
and Mueller 1987).
Phytoplankton. Screening-level monitoring may be done with careful, system-
Phytoplankfon
atic observation. Periodic examination of algal
and biomass are basic
techniques for lake monitoring. Some
are less desirable and indicate prob-
lems. Forexample, dominance by blue-green algae can be responsible for noxious
blooms and surface scums. Excessive algal production reduces transparency and
degrades lake quality.
Sampling gear decisions are based on the water column location where samples
should be taken. A trap encloses a volume of water at a discrete depth. Traps may
will be missed.
be preferred since nets are size-selective and smaller
However, towing a net at a constant depth provides a horizontal sample while a
vertical tow samples plankton from a given depth to the surface. Phytoplankton
vary horizontally and vertically and throughout seasons. Therefore, care should
be taken when sampling to avoid missing plankton concentrated in a thin strata.
Chlorophyll a concentration is a measure of algal biomass and
state.
Chlorophyll a is expected to decrease if lake nutrient loading rates are decreased.
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