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Ecological Preferences
The following environmental parameters are considered as most important for the survival, growth and reproduction of Dreissena spp.: water temperature, dissolved oxygen, pH, calcium concentration, substrate size, depth, transparency, current velocity and salinity.

Water Temperature. The water temperature is very important for the reproduction of dreissenids. Zebra mussel normally begin to spawn at 12oC and above. Spawning peaks at about 15-17oC, which is also the optimum temperature for larval development. 30oC is reported as the upper limit for efficient feeding and adult growth, and 31-33oC as the upper limit for short-term survival. The lower limit for survival of zebra mussels was accepted to be 0oC.

Dissolved Oxygen. Dreissenids are among the least tolerant of low oxygen content of all freshwater bivalves. The lethal lower limit for adult zebra mussels is about 4 mg/l of oxygen, or about 20% of saturation at 18oC. Oxygen saturation of about 80-90% was reported as optimal for zebra mussel occurrence. The oxygen requirements of zebra mussel rose in warm water (25oC and over), and decline in colder water allowing overwintering mussels to survive under ice.

pH. pH regulates calcium uptake in freshwater shellfish. Zebra mussels are generally more vulnerable than other freshwater bivalves to disruption of ion metabolism from reductions in pH level. They have distinct pH-tolerance limits. In the laboratory studies, pH of 7.4 to 9.4 was required for veliger development, and development success peaked at pH of about 8.4 at 18-20oC. Minimum pH requirements for zebra mussel range from 6.5 to 7.5 and maximum pH requirements from 9.0 to 9.5.

Calcium Concentration. Dreissenids require calcium for shell growth and osmoregulation. This element has been recognized as a key factor affecting the mussels' potential distribution, survival, growth and reproduction. It was reported that the ambient calcium concentration of 12 or 15 mg/l is the minimum threshold for reproduction and growth of zebra mussels, and that abundant reproducing populations most probably would become established in concentrations between 20-28 mg/l and above.
Substrate Type. Dreissena larvae need hard substrate to settle on and begin adult life. In lakes with little hard substrate, zebra mussels can settle on sticks, logs, or onto each other, eventually forming large colonies. Native unionids, gastropods and macrophytes are also common substrates for zebra mussel colonization. Over time, adult zebra mussels also start to use soft sediments, but again preferably colonize hard substrate and their density is determined by substrate size.
see different substrates >>>

Water Depth. Water depth may influence on shell morphology, age structure and abundance of Dreissena populations. Young individuals of zebra mussel (at age 1-2) prevail at lower depths, where they can find suitable substrate (vegetation) and higher oxygen content. The abundance of zebra mussel populations is the highest in the littoral and sublittoral zones between 2 and 12 m.

Secchi Disk Depth. The optimal conditions for zebra mussel growth appeared to be Secchi disk depths between 40 and 200 cm. Higher transparency may control zebra mussel distributions by interfering with feeding. The lower limit for survival is 10 cm.

Water current velocity. The dreissenids are found in standing and running waters. They can be established at water current velocity of up to about 1.5 m/sec. The forms living at higher current velocity have better developed byssal apparatus.

Salinity. The salinity can limit the establishment of dreissenids. Zebra mussels were found at water salinity in the range from 0 to 1.9 ‰. The salinity tolerance limits depend on salinity levels, as well as on the rate of change of salinity and on the composition of the salt. At abrupt fluctuation of salinity, zebra mussels die at 5‰; while at gradual increase, they can develop normally at 11‰ and die at 17‰.


 

This website is developed with support from the Bulgarian Science Fund, Ministry of Education, Youth and Science,
within the Project "Assessment and Management of Dreissena spp. Invasions in the Bulgarian Water Bodies",
Contract Number: DO-02-283/2008.

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