Island Life Magazine Ltd December 2006/January 2007 | Page 46
Meadows beneath the sea
ISLE OF WIGHT - WILDLIFE
sheltered bays and estuaries. The
Isle of Wight plays host to some of
our larger common eelgrass beds,
particularly around Bembridge,
Ryde and Yarmouth.
Seagrass meadows have long
been recognised as very important
habitats.
Seagrasses
provide
a valuable food source for our
counties’ wildfowl, who feed on the
dwarf and narrow-leaved varieties
when the tide is out. Underwater,
the often dense cover of leaves
provides the perfect nursery ground
for juvenile fish and crustaceans like
shrimp and crabs, where they can
shelter and hide from currents and
predators. Many of the juvenile fish,
when they reach adulthood, will
be targeted by commercial fishing
vessels, giving seagrass meadows
an important economic role.
As well as these economically
important species, there are other
inhabitants of seagrass meadows.
Seahorses favour these areas,
anchoring to the plants with their
tails. These elusive creatures have
been discovered in seagrass beds off
Dorset, but not yet in Hampshire or
the Isle of Wight. However, several
have been found washed up on the
shores of the Island, one of which
survived, so we believe they are out
there, just waiting to be discovered.
Seagrasses are not only home for
a myriad species; the meadows
perform other vital functions in
our marine ecosystem. Their roots
stabilise our shores, trapping
sediment and preventing erosion.
By doing so it is thought that this
process also traps carbon in the
seabed, acting as a “sink”, absorbing
excess atmospheric carbon that
contributes to global warming.
Photograph - Steve Trewhella
Grass may not always seem
the most interesting of
refuges for wildlife, but
when it lives in the sea
it certainly becomes so.
Seagrasses, often known
as eelgrasses in the UK, are
the only group of flowering
plants in the world able
to live fully immersed in
seawater.
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There are approximately 60 species
of seagrass, but only three are found
around the coasts of Hampshire and
the Isle of Wight. Dwarf eelgrass
(Zostera noltii) and narrow-leaved
eelgrass (Zostera angustifolia)
live on the shore, where they are
uncovered by the water at low tide.
Common eelgrass (Zostera marina),
which has much longer and broader
leaves than the other two species,
lives fully submerged at depths of
up to 5m, sometimes deeper if the
water is very clear and allows light
to penetrate further.
Like all flowering plants, and
unlike the seaweed more normally
found around our coasts, seagrasses
have roots and so live in sandy or
muddy areas where their roots
can take hold. Our local coasts
have a lot of these habitats, so it
makes us comparatively rich in
what is thought to be a nationally
scarce group of plants. Dwarf and
narrow-leaved eelgrass meadows
are found on the mudflats in
Langstone Harbour as well as other
Sea meadows
in decline
Unfortunately, seagrass habitats
have not had it easy and meadows
have suffered large declines in
size over the last century, with
some disappearing entirely. In the
1930s, ‘wasting disease’, which
is thought to have been caused
by a combination of a rise in sea
temperatures and a parasite,
decimated seagrass beds. This
in turn led to declines in all the
wildlife associated with the beds.
The meadows have started to
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