Consultant's Report - Minnesota State Legislature

vigorously using air stones and filtered ufiing a charcoal filter/jet. To keep mussels from
adhering to one another, inert rocks were scattered along the bottom of aquaria as in
Stoeckel and Garton (1993). Aquarium water temperature was held at 12 ± 1 °C in a
water bath to inhibit spawning (Ram et al. 1993, Fisher et al. 1994). Mussels in each
aquarium were fed daily with 30 mL of concentrated Raphidocelis subcapitata (formerly
Selenastrum capricornutum) from a laboratory-maintained culture (US EPA 2002).
Conductivity, temperature and ammonia levels were monitored daily. A 50 - 100 %
water exchange was conducted if total ammonia levels exceeded 2 mg/L. Dead mussels
were removed from holding tan1es daily, although only 2 mussels died during the holding
period (20 April- 12 July 04).
Table 1. Properties ofLake Ossawinnamakee and reconstituted water.
Properties HRW 1
Lake Ossawinnamakee
pH 8.2 8.4
Hardness 171 mg L- 1 (as CaC0 3 ) 163 mg L- 1 (as CaC03)
Alkalinity 110 mg L- 1 (as CaC0 3 ) 126 mg L- 1 (as CaC0 3 )
June Temperature 18 ± 1 0C 2 18 - 21°C 3
1 Hard reconstItuted water (US EPA 2002)
2 Temperature used in exposure experiments
3 Approximate temperature range ofLake Ossawinnamakee, June (Montz, pel's. comm.).
Spawning induction
Spawning was induced by 30-minute exposure of 10 - 20 mm* mussels
(acclimated for 18-h at 18 ± 1°C) to a 5x 10- 4 M solution of serotonin creatinine sulfate
monohydrate (CAS# 61-47-2), as conducted in previous study (Ram et al. 1993, Fisher et
al. 1994, John Lynn, LSD, per. comm.). Males were observed to spawn within 15 - 30
minutes, at which point they were transferred to clean HRW. Mussels that did not spawn
in 30 minutes were assumed to be female and were transferred to clean HRW. Viable
·females spawned in clean HRW after 60 - 90 minutes as observed in previous study
(Ram et al. 1993, Fisher et al. 1994). Gametes were used in subsequent trials within 1.5
h of sperm production. After 15 minutes, to allow fertilization to occur, HRW containing
fertilized eggs was gently aerated (2-3 bubbles/sec) to provide flow to embryos, and
maintained at 17 ± 1°C.
Larval exposure protocols
Studies have demonstrated that the pelagic larval stages ofD. polymorpha may be
the most sensitive stage for control measures (Vanderploeg et al. 1996). In addition,
Fisher et al. (1994) showed that the sensitivity of zebra mussel life stages to different
molluscicides varied, although in most cases the veliger stages were more sensitive than
later stages. Therefore TRV data were derived for D. polymorpha larvae across a range
of developmental stages. Previous studies have shown that laboratory-reared D.
* Smaller mussels did not praduce a suitable stock of gametes, while larger mussels produced gametes of
inconsistent quality.
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