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| Maximum depth 0.5 m below loch datum |
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is connected to Kirkwall harbour in the north-east Mainland.
The western side of the lagoon is isolatde from the rest of the lagoon by a concrete walkway which forms the boundary of boating pond. The boating pond connects to the lagoon via a series of pipes and is connected to the harbour by a sluice gate.
There is a very little disturbance from wave action or tidal currents are only significant in the area of sluices.
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Water in silled lagoons is retained at all states of the tide by a barrier
of rock (the ‘sill’). There is usually little tidal rise-and-fall.
Seawater input is regular (i.e. on most tides) and although salinity
may be seasonally variable, it is usually high, except where the level
of the sill is near to high tide level. These lagoons are restricted
to the north and west of Scotland and may occur as sedimentary basins
or in bedrock (where they are called ‘oban’). Muddy areas are
dominated by filamentous green algae, amongst which may be colonies of
rare charophytes, such as foxtail stonewort Lamprothamnium
papulosum. There may be beds of tasselweed Ruppia spp.
and, in the deeper most stable lagoons, eelgrass Zostera marina.
