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During our brushing out activity on the Bevern
Stream a distinct lack of submerged aquatic vegetation was apparent.
In the riffle and pool systems, which are characteristic of this
watercourse upstream from Clapper's Weir, the only species detected
were water mosses (Fontinalis antipyretica and Eurhynchium riparoides).
These are found in some of the fast water areas on large stones
and boulders. The deeper pools where there is a silt substrate and
slow current do not appear to support any submerged vegetation of
note. A similar situation also pertains to the Northend Stream.
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Strapweed
(Sparganium emersum) near Goldbridge, Newick |
It is difficult to understand why
these two streams suffer from this deprivation when the main river
and other tributaries contain an abundance of submerged flora of
varying species. Factors such as instability of the stream bed in
spate conditions, herbicide pollution etc. may be involved, but
these are not factors peculiar to these two streams alone. There
may just be a lack of seeding of appropriate species.
It has been demonstrated that the
number of invertebrates present is greatly enhanced by the presence
of submerged flora. A survey carried out by Percival and Whitehead
on the rivers Aire, Nidd and Wharfe found a mean of 3,316 invertebrates
per sq. m. in loose stones compared with 243,979 in areas with submerged
vegetation on stones. It would therefore seem reasonable to assume
that an increase in the variety and amounts of submerged water plants
in the streams would improve the habitat for invertebrates and enhance
the ecology.
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| Water Starwort (Callitriche
spp) growing in the Shortbridge Stream |
It was therefore decided to implement
an experimental planting project in the Bevern Stream with continuous
monitoring of the results, subject to Environment Agency and riparian
owner consents. These consents were obtained and valuable advice
was given by Jane Cecil the Environment Agency Fisheries and Ecology
Manager for the Sussex area.
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| Water Crowfoot (Ranunculus
fluitans) at Sheffield Park |
A donor site was identified on the
River Ouse at Sharpsbridge where prolific growths of starwort (Callitriche
sp.), water crowfoot (Ranunculus fluitans) and strapweed (Sparganium
emersum) were available. Permission to harvest in this area was kindly
given by the riparian owner Mr. John Sclater.
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