A toxic algae has bloomed again in waters in Shetland and part of the Western Isles.
The blue-green algae has been found in samples taken by Scottish Environmental Protection Agency at Loch Cliff, Unst, and Loch Langabhat, South Harris.
The algae exist in fresh water in the UK and worldwide and are noticed when their concentrations increase to form blooms and then scums, which look like blue and green paint.
Notices will be posted next to the lochs warning that contact with algal scum should be avoided, and local health boards have been advised of the situation.
People who come into contact with the toxic scums can get skin rashes, eye irritations, vomiting and diarrhoea, fever and pains in muscles and joints.
Toxic algae have in the past also caused deaths of livestock and dogs.
Adjoining landowners and fishing interests have been advised of the situation. At this stage there is no adverse effect on water supplies.
The treatment of water supplies removes the algae and additional treatment may be applied to destroy or remove toxins should they arise. The actions currently taken are precautionary.
The behaviour of toxic algae is erratic as it can appear one day, be dispersed by the wind but re-accumulate at any time.