64
4. Protocol for Aquatic Hazard Assessment
When the eggs of nesting birds are sampled, it is desirable to collect
eggs of species that use a localized feeding area which represents the
study site or Hydrological Unit (see Chapter 6) and will thus reflect the
local conditions of exposure to dietary selenium. Species such as American coots (Fulica americana), grebes (Podilymbus sp.), and dabbling ducks
(Anas sp.) are good choices in this regard. With fish, species that are
resident in the area will suffice. Depending on location, minnows (Cyprinidae), sunfish (Centrarchidae), suckers (Catostomidae), catfish
(Ictaluridae), and trout (Salmonidae) should be readily available and
easy to sample. For some species, particularly cyprinids in streams, it
will probably be necessary to select large individuals in order to obtain
sufficient egg mass for analysis. Migratory species of birds and fish that
could have recently arrived (within 2 weeks) at the study site from
distant locations should be avoided because they may not have had
time to accumulate tissue residues of selenium that reflect local exposure conditions (Heinz et al. 1990).
Data for the Protocol can be from a one-time sampling effort or from
an ongoing monitoring program of considerable duration. If the latter
case exists, I recommend that the most recent data (1-2 years) be used,
since it would yield the best estimate of current hazard. There is no
minimum or maximum number of measurements as long as the specified ecosystem components are sampled (see next section). However,
spatially complete sampling efforts will result in hazard ratings that
reflect the range of habitat types and environmental conditions that
are present. Moreover, the Protocol assesses hazard based on the highest concentrations of selenium found; thus, it is important to take a
sufficient number of samples to detect these upper levels. Hazard estimates generated from robust data sets will also lend credibility to ensuing management actions or follow-up studies, should they be needed.
Eggs are a key component in the assessment because change in reproductive success is the most sensitive biological response for determining
selenium toxicity to fish and aquatic birds (Lemly 1997a). Selenium ingested in the diet is readily transmitted from the parent to developing
eggs, where it can cause teratogenic deformities and embryomortality.
Complete reproductive failure can occur in the absence of observable
toxic effects on the adults (Gillespie and Baumann 1986; Heinz et al.
1987, 1989; Woock et al. 1987; Coyle et al. 1993). The Protocol thus incorporates a sensitive indicator that reflects the mode of toxicity responsible
for the most serious community and ecosystem-level effects.
In order for the assessment to be reliable, the data for selenium
concentrations must also be reliable. Analytical methods used to determine selenium should be sensitive and under strict, documented
quality control. Methods for water and tissues should have limits of
detection in the
SelL range and
Selg range, respectively. This is important because an error of only 1
SelL or 1
4. Protocol for Aquatic Hazard Assessment
When the eggs of nesting birds are sampled, it is desirable to collect
eggs of species that use a localized feeding area which represents the
study site or Hydrological Unit (see Chapter 6) and will thus reflect the
local conditions of exposure to dietary selenium. Species such as American coots (Fulica americana), grebes (Podilymbus sp.), and dabbling ducks
(Anas sp.) are good choices in this regard. With fish, species that are
resident in the area will suffice. Depending on location, minnows (Cyprinidae), sunfish (Centrarchidae), suckers (Catostomidae), catfish
(Ictaluridae), and trout (Salmonidae) should be readily available and
easy to sample. For some species, particularly cyprinids in streams, it
will probably be necessary to select large individuals in order to obtain
sufficient egg mass for analysis. Migratory species of birds and fish that
could have recently arrived (within 2 weeks) at the study site from
distant locations should be avoided because they may not have had
time to accumulate tissue residues of selenium that reflect local exposure conditions (Heinz et al. 1990).
Data for the Protocol can be from a one-time sampling effort or from
an ongoing monitoring program of considerable duration. If the latter
case exists, I recommend that the most recent data (1-2 years) be used,
since it would yield the best estimate of current hazard. There is no
minimum or maximum number of measurements as long as the specified ecosystem components are sampled (see next section). However,
spatially complete sampling efforts will result in hazard ratings that
reflect the range of habitat types and environmental conditions that
are present. Moreover, the Protocol assesses hazard based on the highest concentrations of selenium found; thus, it is important to take a
sufficient number of samples to detect these upper levels. Hazard estimates generated from robust data sets will also lend credibility to ensuing management actions or follow-up studies, should they be needed.
Eggs are a key component in the assessment because change in reproductive success is the most sensitive biological response for determining
selenium toxicity to fish and aquatic birds (Lemly 1997a). Selenium ingested in the diet is readily transmitted from the parent to developing
eggs, where it can cause teratogenic deformities and embryomortality.
Complete reproductive failure can occur in the absence of observable
toxic effects on the adults (Gillespie and Baumann 1986; Heinz et al.
1987, 1989; Woock et al. 1987; Coyle et al. 1993). The Protocol thus incorporates a sensitive indicator that reflects the mode of toxicity responsible
for the most serious community and ecosystem-level effects.
In order for the assessment to be reliable, the data for selenium
concentrations must also be reliable. Analytical methods used to determine selenium should be sensitive and under strict, documented
quality control. Methods for water and tissues should have limits of
detection in the
SelL range and
Selg range, respectively. This is important because an error of only 1
SelL or 1