Estimating Water Body Risk of Introduction and Establishment

 

Many factors contribute to the risk of dreissenid introduction and establishment, including environmental parameters (e.g., dissolved calcium, pH), and the extent and types of public use (e.g., total day use, presence of boat ramps and marinas, proximity to transportation corridors, motorized boating, fishing). Total day use of a water body, presence of boat ramps and marinas, water body size and access, motorized boating, fishing, and angling tournaments are important determinants of risk of introduction (Wells et al. 2010). Once introduced, pH and calcium concentrations, considered critical environmental parameters for dreissenid mussel survival and growth (Hincks and Mackie 1997; McMahon 1996), are likely to determine the success of establishment (Wells et al. 2010).

 

In general, dreissenid adults in North America inhabit waters with calcium concentrations greater than or equal to 15 mg Ca2+/L, and populations become dense at concentrations greater than or equal to 21 mg Ca2+/L (McMahon 1996).

 

Dreissenid veligers are found in North America at pH levels between 7.4 and 9.4; pH 8.4 is optimal (McMahon 1996). Adult dreissenid mussel growth is generally limited at pH less than 6.5 to 6.9 and pH greater than 10, because dreissenids lose calcium to the external environment (Hincks and Mackie 1997; McMahon 1996).

 

Water temperature is not expected to limit growth as dreissenids inhabit a wide range of temperatures in North America. They are found in the Great Lakes at temperatures less than 41°F, and in the lower Mississippi where temperatures reach and exceed 86°F (McMahon 1996).

 

Adult and veliger dreissenid survival increases with an increase in calcium concentration (Davis et al. 2015) (Figure 3).

 

Figure 3. Adult and veliger quagga survival versus calcium concentration in experimental water. Survival of adults (after 90 days) and veligers (after 30 days) versus calcium concentrations in experimental water from Tahoe Cave Rock (9ppm), Tahoe Keys (12ppm), Tahoe Ca amended water (15–34ppm), and Lake Mead (72ppm). Logistic regression model fit to data shown for adult (solid line) and veliger (dotted line). Graphic credit: Davis et al. 2015.

 

adult and veliger survival

 

Several entities have developed criteria to determine the levels of dreissenid infestation in the temperature zone of North America and Europe (Mackie and Claudi 2010) (Table 3). Calcium is necessary for shell production, alkalinity signals availability of calcium, and pH influences the form of carbon available—calcium is available in the HCO3 form when pH values are less than 8.2 (Pucherelli et al. 2016).

Fort Peck Lake is categorized as a high-risk water body for dreissenid introduction and establishment based on total fishing pressure, total non-resident fishing pressure, and Ca2+ expressed as mg/L (Wells et al. 2011). The mean Ca2+ for Fort Peck Lake is 47.0, total fishing pressure and non-resident fishing pressure is categorized as high, and the mean pH is 8.6 (minimum of 8.5 and maximum of 8.8) (Wells et al. 2011).

 

Table 3. Criteria used in determining the levels of dreissenid infestation in the temperature zone of North America and Europe (Mackie and Claudi 2010).

Parameter

Adults do not survive long-term

Uncertainty of veliger survival

Moderate infestation level

High infestation level

Calcium (mg/L)

<8 to="" 10="" --8--="">

<15

16–24

≥24

Alkalinity (mg CaCO3/L)

<30

30–55

45–100

≥90

Total hardness (mg CaCO3/L)

<30

30–55

45–100

≥90

pH

<7.0 or="">9.5

7.1–7.5 or 9.0–9.5

7.5–8.0 or 8.8–9/0

8.2–8.8

Mean summer temperature (June 1–August 31) (°F)

<64

64–68 or 83

68–72 or 77–83

72–75

Dissolved oxygen mg/L
(% saturation)

<3 25="" --3--="">

5–7 (25–50%)

7–8 (50–75%)

≥8 (75%)

Conductivity (µS/cm)

<30

<30–60

60–110

≥100

Salinity (mg/L) (ppt)

>10

8–10 (.01)

5–10 (0.005–0.01)

<5 0="" 005="" --5--="">

Secchi depth (m)

<0.1>8

0.1–0.2 or >2.5

0.2–0.4

0.4–2.5

Chlorophyll a (µ/L)

<2.5 or="">25

2.0–2.5 or 20–25

8–20

2.5–8

Total phosphorus (µg/L)

<5 or="">50

5-10 or 30–50

15-25

25-35