wildlife is internationally renowned and attracts many visitors to the
islands. Those elements that live on land – such as birds, mammals and
plants – are relatively well known. However, we know a great deal less
about our marine wildlife for the simple reason that it is very difficult
to observe. Two important plants that grow around the coast of Shetland
are eelgrass and maerl. In the right conditions both
eelgrass and maerl can grow to form dense beds which support a wide range
of other marine plants and animals. As a result they make an important
contribution to the biodiversity of the islands.
Shetland Biological Records
Centre is keen to find out more about Shetland’s marine life. Please help
us by recording your sightings of eelgrass and maerl on the survey form at
the bottom of this page and returning it to SBRC.
Photo right - surveying the
eelgrass beds at Whiteness Voe.
EELGRASS - Zostera marina
eelgrass grows in the sea, it is not a seaweed, but a group of marine
flowering plants. However, it is unlikely that you will ever see the
flowers because they are very small and usually hidden at the bottom of
the leaves. Eelgrass grows in shallow coastal seas around the world
generally in water less than 10m deep. It is usually found on sandy or
muddy areas sheltered from strong tides and currents.
Eelgrass is only patchily
distributed around the UK. This is partly due to a wasting disease in the
1930s which wiped out populations in many areas. Although eelgrass is
nationally scarce, in the right conditions it can form dense beds known as
meadows. Other plants that are often found associated with eelgrass
meadows include sugar kelp and bootlace weed, together with burrowing
animals such as razor shells and heart urchins.
of eelgrass are important for a number of reasons. They provide a wide
range of habitats for many other plants and animals, including sheltered
nursery areas for some types of fish. The plant roots form a dense
network which stabilises the seabed, helping to reduce coastal erosion.
In addition, decomposing plants support food chains both inside and
outside the beds.
Only one species of eelgrass
occurs in Shetland, Zostera marina, known locally as ‘Marlie’. At
present three eelgrass beds are known in Shetland, at South Voe, West
Burra, Marlee Loch at the head of Brindister Voe, and in Whiteness Voe.
Photos - eelgrass
is the name given to several species of red seaweeds which have hard
calcium skeletons. It grows as free living nodules on the seafloor and is
one of the slowest growing plants in the North Atlantic, growing only a
few millimetres each year. Maerl tends to grow best in tidal flows
associated with rapids and in sounds between islands, such as in Bluemull
Maerl is found from the
Mediterranean to Scandinavia, although it is a relatively scarce habitat.
It can occur as simply a few scattered nodules, right through to extensive
beds. Maerl beds develop very slowly and are usually made up of a mixture
of live and dead nodules, although the proportion can vary greatly between
areas. Large beds tend to be made up of a bottom layer of dead maerl
gravel overlain by a thin layer of live nodules. It is easy to tell the
difference between the two: live maerl is pink, but this colour fades
gradually when dead.
Both live and dead maerl
provide habitats for a wide range of plants and animals, some of which are
rare and largely confined to maerl beds. Keep a look out for different
species living in and around maerl beds. These may include sugar kelp, an
anemone called Cerianthus lloydii, common sea urchins, hermit crabs
and harbour crabs.
look out for maerl or eelgrass when you are diving. Have you found a few
scattered individuals or been lucky enough to come across a large and well
established bed? As well as looking at the two plants, try and record
other plants and animals that live on or in these habitats, especially if
they appear to be particularly common. For maerl, also have a look at how
much is living (pink) and how much dead (cream coloured).
Please describe the location
of the maerl or eelgrass very carefully - give a grid or chart reference
if possible. And, remember, if you see anything else interesting
underwater, please let us know.
Photos - maerl
SBRC DATA SHEET
The following is the information required for the
eelgrass and maerl survey, please fill in as much as you can. You can
either copy and paste this information into a document or download this
form as an
Adobe Acrobat file (PDF).
Name and address of recorder:
Site name: Date of
Site location: (either OS grid reference or latitude/longitude)
Time of dive Start: Finish:
Underwater visibility: Current speed:
Sketch of dive profile and where the maerl/eel grass has been found:
Please include some indication of the abundance of the plants and how big
an area they cover and for maerl the % of live maerl/dead maerl/other
Sea floor type:
Depth range of habitat:
Other plants or animals present:
Please fill in the form with
as much detail as possible and return to:
Garthspool, Lerwick, Shetland ZE1 0NY Tel. (01595) 694688