Cheakamus River Water License Requirements ... - BC Hydro

Cheakamus River Benthic Community Monitoring, Progress Report 15
and all locations during each time series. For the summer series, a description of the
accrual curve is being recorded by analysing samples from the complete time series at
CH4 and CH5, where extremes in biomass were found (low biomass at CH4 and high
biomass at CH5). These analyses are not part of project budgeting but are being done
with anticipation of cost savings elsewhere in the budget. Similar descriptions of accrual
curves will be acquired for the other seasons as budget permits.
Each periphyton sampler is submerged in water depths of 8 – 50 cm in riffle or
run habitat at each site. Once per week for at least 6 weeks, a 2 cm diameter core of
the styrofoam and the adhered biomass is removed using the open end of a 7 dram
plastic vial and analysed for chlorophyll-a concentration using fluorometric procedures
reported by Holm-Hansen et al (1965) and Nusch (1980). These analyses are being run at
the Fisheries and Oceans (DFO) Cultus Lake lab.
On the final sampling day of each series, one additional core is removed from
each substrate and preserved in Lugol's solution for taxonomic identification and
enumeration. The composition of the periphyton communities is determined from cell
counts, by species, made at 500x magnification after settlement in Utermohl chambers.
Only cells containing cytoplasm are being enumerated. A minimum of 100 individuals of
the most abundant species and a minimum of 300 cells in total are counted. Cells of
filamentous taxa are separated from counts of unicellular taxa. Cell counts are
extrapolated to biovolume based on known volumes of algal taxa.
The invertebrate baskets are installed at each location at the same time that the
periphyton substrata are installed. They are placed in riffles or runs in water depths of 15
- 50 cm. The baskets are embedded with the top surface flush with the top of the natural
gravel or they are lodged between larger cobble and boulders where ambient substrate
particle sizes are large. On the day of final periphyton sampling, the baskets are
retrieved. A 250 μm mesh Nitex dip net is placed behind the basket. The complete net
and basket assembly is lifted out of the water and the basket is placed into a collection
bucket. This retrieval method prevents loss of animals. In the collection bucket, the
baskets are opened; the invertebrates are brushed from the gravel and preserved in
10% formalin. In the laboratory, each sample is washed through a 1 mm and 250 μm
mesh sieve to yield a macrobenthos fraction (>1 mm) and a microbenthos fraction (250 um). In this process, all animals are picked from twigs, grasses, clumps of
algae, and other debris and returned to the top sieve. Microbenthos is split into 4 to 16
subsamples using a large plankton splitter with the number of splits increasing with
animal abundance. Sub-samples of microbenthos are enumerated until 200 animals are
counted. If a count of 200 animals is reached part way through the sorting of a subsample,
that entire sub-sample is counted. The complete macrobenthos fraction is
enumerated. Total sample count is the microbenthos subsample count multiplied by the
number of subsample splits plus the count of macrobenthos. The animals are identified
Limnotek/InStream
November 2009