Keith, I asked about the salinity issue on the Chemistry forum and got an answer about Sulphate being very similar to Molynbendium.
I hope I get this all right....
Sulphate is a major part of Magnesium Sulphate (Epsom Salt).
Molynbendium is absorbed by bryopsis as it grows.
The trick is, Sulphate can be absorbed by the Bryopsis just as it would normally absorb Molynbendium. Unfortunaly for the Bryopsis, Sulphate does not fulfil whatever needs Bryopsis has for the Molybendium. This can result in what would be described as rapid growth of the Bryopsis as it absorbs the Sulphate (instead of Molybendium). The growth should be pulled manually. It is just a matter of time for the Bryopsis to start dying. You should probably increase your Mag levels some more also. Might be just a little bit more needed to kill off your Bryopsis.
I am sure there is more to this, but I believe that this is the general idea.
In my experience (with a very badly infested rock) The bryopsis is slowly dissapearing. But I am having to frequently monitor my Mag levels and have to regularly add more Epsom Salt as the sheer volume of Bryopsis I am fighting is soaking the stuff up like a sponge.
And as for the increased salinity. Epson Salt or any other method of raising your Mag, needs to be accounted for when determining your tanks salinity. (See info between table 2 and table 3.)
http://reefkeeping.com/issues/2006-02/rhf/index.php
Especially when adding the large amounts to our tanks that people are adding. I personally think this increase is the most likely cause of the trouble some people are reporting in their tanks.