Predicting the distribution of maerl

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Predicting the distribution of maerl

• By
• Malcolm Thomson
• International Centre for Island
  TechnologyHeriot-Watt University (Orkney
  Campus)Old AcademyStromness OrkneyScotland

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What is maerl?

• coralline red seaweed
• secrete calcium carbonate (CaCO3)
• coastal distribution
• long lived

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Importance of maerl

• commercial
• scientific
• biodiversity
• sensitivity / fragility
• natural man-made threats

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Maerl habitats

• living dead maerl beds
• small scale patchiness

Video Wyre Sound, Orkney Aug 2000
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Large scale distribution

• water depth (light penetration)
• water movement
• tides waves
• temperature
• water chemistry
• seabed type

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Project SUMARE

• develop models using a priori knowledge to
  delimit the regions where we would expect maerl
  to occur (wp1)

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ICIT model

• water depth
• tidal velocity
• wave exposure

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Existing datasets

• Admiralty data
• MNCR/JNCC
• SUMARE fieldwork
• ICIT student research

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Combined dataset...
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Set of possible conditions

• 11 depth bands
• 4 tidal categories
• 3 exposure categories
• 132 possible scenarios
• 1750 samples
• assign a frequency to each derived from the
  number of occurrences of maerl under each
  different scenario

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Frequency data

• e.g. for the 11-15m depth band

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11-15 m depth band
Frequency
Exposure
Tidal category
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5 km
Red 0-15m, tide 3. exposure 1, 0.174 Gold
0-15m, tide 3, exposure 2, 0.073 Blue0-15m,
tide 3, exposure 3, 0.071 Green 16-20m, tide
3, exposure 1-2 0.070
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Frequency of maerl
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Predictions...

• an idea under what conditions maerl is more
  likely to occur
• a good idea of the conditions where maerl is not
  going to occur

Navigation of AUV