Winter arrived in Perthshire last week or it felt like winter as the air temperature plummeted with a high pressure system bringing sun and winds from the north.  Fortunately there was no rain to speak of and the water temperature lags behind the air, so spending several hours a day snorkelling around freshwater lochs was not as uncomfortable as it might have been.  The water was quiet and still and searching the loch floor for rare plants was like looking through a muffling brown fog.  It was a case of breathe in, hold it, dive down fighting the buoyancy in the dry suit but helped by lots of lead, catch a glimpse of a small patch of vegetation, swim as far as the breath allowed, shoot back to the surface, repeat.  We would each do this for an hour or so and then take a turn in the boat, putting in markers for each other around the edge of the loch and continuing around the perimeter until we reached the beginning.  In this high tec world in which we live, we used bamboo canes and balloons to mark out 100m sections – tempered by the use of GPS to record their positions.  Simple but effective.

The plant we were searching, Slender Naiad, is unfortunately so rare that we couldn’t find it in the first two lochs we searched although it had been there in abundance during previous surveys.  We panicked.  Did we really know what we were looking for?  So we called in the plant protection squad, in the guise of a friend and expert freshwater botanist who had worked with us on an earlier project.  Fortunately we found some Naiad in our third loch about half an hour before she arrived, and yes we did know what we were looking for and then there was lots.  It is much easier to find when you have a search pattern clearly imprinted in your eyeballs.  But only two plants in the fourth loch and none in the fifth.  Where has it gone?  And why? 

It is an opportunist plant, a coloniser, with a perhaps unlikely strategy for a plant of this type.  It has heavy pollen and seeds that aren’t dispersed in the water but just fall in the general area where they are produced.  It doesn’t compete well with taller plants and needs a clear space to grow.  This means that beds tend to persist in the same area in a loch rather than cropping up where spaces occur.  And although all these lochs are connected, a large population in one loch doesn’t mean it will colonise another.  It would probably take a large storm at this time of year to disperse the seeds to another area.

Anyhow, it was a very peaceful, if energetic, week and at least partially successful.  More successful than this week’s maerl work which has been cancelled.  Again.  Where engineers are concerned, biologists really are the dust that gets swept under the carpet.