[Kenner18]

Originally Posted by Spunt Drag

It can survive for what extended period of time?

There was no clear amount of time that it would survive in the info I researched . Here is the info I had found a few yrs ago .

Salinity:
Ruppia maritima has been found in water ranging from fresh to 32 ppt salinity, but is generally found in waters of 25.0 ppt or less (Phillips 1960).
In vitro rhizome growth and rooting of Ruppia maritima occurred at various salinities using artificial seawater. Rhizome production was most rapid at 0 & 5 ppt as opposed to 10, 15 and 20 ppt salinity. In vitro root production, although requiring an external carbon source, was greatest at 5 and 10 ppt salinity. This study also showed that ex vitro plantings were very successful suggesting that Ruppia maritima would be a good candidate for propagation through in vitro culture (Bird et al. 1993).
When Ruppia maritima from Redfish Bay, Texas, was transferred to outdoor ponds and controlled growth rooms where salinity was artificially increased, in the latter environment, growth continued until 70 ppt salinity in controlled growth rooms. In this same environment, R. maritima tolerated a salinity of 74 ppt, for a brief period.