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The Essex Naturalist
tend to be ephemeral in these habitats. Thousands of suitable ponds have been
filled-in in recent decades, have become surrounded by trees, or are now
polluted by agrochemicals or farm slurry. In many areas the alien New Zealand
Pigmyweed, Crassula helmsii, or/and Nuttall's Water-weed, Elodea nuttallii, have
occupied the shallows that they would otherwise frequent, and as already
mentioned, grazing Canada geese are becoming a menace not least, because of
the enrichment they cause. Fisherman also tend to drag out large quantities of
marginal colonies to create clear water.
On the other hand, new gravel pits, agricultural reservoirs and fishing lakes
are being created all over the county, and from initial results, clearly provide an
excellent and as yet largely unexplored habitat. In agricultural reservoirs they
are to be encouraged, and can be profitably introduced, as they rapidly stabilise
the bare sediment and oxygenate the water, and are reputed to exude a variety
of natural mosquitocides. In addition our larger Essex rivers, although they
largely consist of recycled sewage water - the Roding for example yields around
5.7 millions gallons for drinking water and irrigation per year and receives about
the same amount back as filtered sewage - are becoming a more attractive
habitat for some stoneworts. The clearly recognisable solid matter from
untreated sewage, that accumulated as sludge in the central channels during the
1950s and '60s, has now largely decomposed, and Nitella mucronata in particular
is beginning to exploit this newly available niche, providing a valuable
oxygenator for these deeper regions. Although stoneworts prefer calcareous
waters, they have been found in ponds lakes and rivers throughout Essex. If you
look for them you will find them.
Future Recording
Anyone finding a charophyte is encouraged to send me a specimen for
identification. I would prefer to see as much material as posssible as I am trying
to build up a picture of morphological variation. They travel well damp (rather
than wet) in a sealed polythene bag so that they have plenty of oxygen. They rot
rapidly in bags of water! Always try and include some nice young green
unencrusted apical segments, and if present male and female gametangia. Small
scraps may be indeterminate.
In view of the uncertain state of the taxonomy we need to keep pickled
vouchers of as many of our records as we can, in case these require future
revision. The taxonomy of the Chara vulgaris varieties is particularly
unsatisfactory. Unfortunately, what appears to be a set of largely independently
variable characters, has been used to describe taxa given varietal status, and one
commonly finds material that has the characteristics of two or more varieties e.g
the combination longibracteata plus papillata. As the taxonomy is in a state of
flux, I propose that for future recording in Essex we concentrate on the
characters expressed rather than trying to shoehorn forms into the limited set of
varietal taxa available. A useful concept is the term "expression" that has for