Poisoned: 400 of Britain's lakes

Many of our most famous waters, from the lochs to the Broads, are
being badly polluted. Environment Editor Geoffrey Lean reports

Published: 11 February 2007

Nearly 400 of Britain's most wildlife-rich lakes are being stifled by
pollution, an official study has found. They include most of the
country's best-known and best-loved expanses of water.

From the Lake District to the Norfolk Broads, from Scotland's
Loch Lomond to Surrey's Frensham Great Pond, from wild
Malham Tarn to suburban Virginia Water, they are being
devastated, mainly by sewage and farming. Some, such as the
haunting Semerwater in the Yorkshire Dales, are so badly affected
that they are virtually dead.

The study, headed by the Environment Agency, covered the 1,047
"most ecologically valuable" of Britain's 14,000 lakes, those either
protected as Sites of Special Scientific Interest (SSSI), or home to
Britain's most endangered species.

It found that 379 of them are so "degraded" that they are in urgent
need of "rehabilitation". It is now joining with other official bodies
to mount a rescue programme of "lake habitat action plans".

"We all take lakes for granted," said Geoff Phillips, an Environment
Agency ecologist who led the study. "Nonetheless, many of them are
severely stressed as a result of human-induced pressures, to an extent
inevitable on a densely populated island."

Historically lakes have received less attention in clean-up campaigns
than rivers, but they are much more vulnerable because their more
stagnant waters allow pollution to collect and do more damage.

Mostly they are being fed to death by sewage and - especially -
wastes and fertilisers from agriculture. These cause weeds and algae
to flourish, soaking up oxygen from the water and suffocating other
life. And, partly as a result, they are often plagued by alien, invasive
species.

Bassenthwaite Lake, in the north of the Lake District, exemplifies
many of the problems. It is theoretically one of the most protected
water bodies in the country - being designated under the EU Habitats
Directive as an SSSI and as part of the Lake District National Park -
and is Britain's main stronghold of a very rare fish, the slim,
blue-green vendace. But it is still struggling to survive, despite efforts
to rescue it.

For decades, it was overfed by effluent from a local sewage works;
this has now been cleaned up, but phosphorous from the past
pollution still lurks in its sediments. And it is still being contaminated
by septic tanks used by houses around its shores.

More pollution comes from the droppings of the sheep that graze its
catchment. And allowing too many sheep on to the fells make things
worse; overgrazing erodes the soil, bringing it -and the wastes - down
into the lake.

Trees are now being planted to help to stabilise the soil, but the waters
produce blooms of blue-green algae, which can be toxic. And they
encourage an invasive species - the Australian swamp stonecrop,
originally introduced to Britain from Tasmania nearly 100 years ago -
which smothers other organisms.

Windermere, to the south, is struggling against another set of perils.
It, too, is polluted by sewage, augmented by a staggering six million
visitors a year. It also receives run-off from cattle farming. Last year,
its blue-green algal blooms were so bad that notices had to be put
up warning people, and their dogs, not to go into the water.

It, too, has a rare fish - the cold-water Arctic char - but as pollution
deprives the depths of the lake of oxygen in summer it is forced to
swim nearer the surface in waters too warm for it to tolerate.
Meanwhile, roach, an invasive species in this lake, flourish in the
balmier temperatures brought by global warming.

The bonny banks of Loch Lomond similarly wash pollution into the
lake from agriculture, and from fertilised golf courses - and it, too,
is polluted by sewage.

Right across the country, the growth of algae is so bad that it has
completely killed off underwater vegetation in many areas, which
in turn destroys invertebrate life and leads to changes in fish
populations. Some, such as Rollesby Broad and Cockshoot Broad,
are being restored, but still suffer from past pollution. Others, such
as Wroxham Broad, remain in deep trouble.

Surrey's Frensham Great Pond, tucked away in the Home Counties
but with an ecology closer to lakes in the northern uplands, receives
too many substances from earth disturbed by road building and
other developments in its catchment area. By contrast, Malham Tarn,
high in the Yorkshire Dales, has been damaged by nature lovers. A
septic tank in a field studies centre on its shores polluted it for years;
it has also been invaded by Canadian pondweed, probably brought
on an angler's rod or a hiker's boots.

Perhaps the saddest story of all is at Semerwater in Wensleydale -
which, by legend, covers a once-thriving city, cursed after turning
away a poor man seeking food. It, said Dr Stewart Clarke, an
ecologist at Natural England, has "suffered massive enrichment"
from the dung of the cattle raised around it. As a result, he said,
"virtually no submerged plants are left in Semerwater any more".

Norfolk Broads

Polluted by sewage. Phosphorous from sewage works remains
in sediment

Frensham Great Pond, Surrey

Threatened by polluted soil disturbed by road building

Malham Tarn, Yorkshire Dales

Plagued by Canadian pondweed, probably introduced by anglers
or hikers

Bassenthwaite Lake, Cumbria

Soil contaminated by sheep droppings has washed into the lake

http://news.independent.co.uk/environment/article2258886.ece