International Centre for Island Technology Heriot-Watt University (Orkney Campus) Old Academy Stromness Orkney Scotland The distribution of maerl around the Orkney Islands Malcolm Thomson ~SUMARE~

Orkney Islands

20 km ICIT Scapa Flow Wyre Sound Map of Orkney showing the location of ICIT and Wyre Sound, where the first sea trials of the PHANTOM vehicle are to be held.

what is maerl? environmental requirements importance European distribution maerl in Orkney

What is maerl? coralline red seaweed secrete calcium carbonate (CaCO 3 ) coastal distribution long lived living & dead deposits “patchiness”

Environmental requirements water depth/light penetration water movement –tides & waves temperature water chemistry seabed type

Importance of maerl commercial scientific –biodiversity sensitivity / fragility –natural & man-made threats

Commercial value of maerl soil conditioner water purification cosmetic ingredient dietary additive bone surgery agricultural - feed, bedding material

European distribution

Maerl in Orkney ICIT student research –modelling the distribution of maerl SUMARE

Personal accounts RoxAnn acoustic data Admiralty navigation charts Marine Nature Conservation Review (MNCR) Combined data set on maerl distribution Existing data on maerl Occurrence of maerl according to environmental parameters

Figure 1: The distribution of maerl as a function of depth (Admiralty and MNCR data combined)

Figure 2: Distribution of maerl as a function of tidal velocity

Figure 3: Distribution of maerl as a function of wave exposure

Figure 4: Predicted distribution of maerl in Orkney. ( ) indicates where the presence of maerl has since been confirmed.

General trends: < 20m depth moderate tidal velocity ( knots ~ ms -1 ) low - moderate wave exposure

Effectiveness of model Sound of Arisaig –less accurate large scale application living vs dead?? probability data

Figure 4: The probability of finding maerl at a specific point as a function of depth - Admiralty chart data

Figure 4: The probability of finding maerl at a specific point as a function of depth - MNCR data

Figure 5: The probability of finding maerl at a specific point as a function of tidal velocity

Goals of SUMARE re. maerl “to show the advantages of using autonomous technology” in developing a sustainable extraction policy for maerl discrimination of living & dead areas area estimates (patchiness) navigation