Seaweed on the sandy beaches
of the Outer Hebrides: An
important food source for
coastal fauna
Kyla Orr (PhD student)
Supe...
Introduction: Macroalgae for Biofuel
• Marine biomass suggested as alternative energy source to terrestrial
biomass due to...
Study Area
North Uist
Benbecula
South Uist
Uists, Outer Hebrides -
west coast dominated by
soft shores and shallow
offshor...
Macroalgae subsidies and coastal
communities Detached
seaweed
Birds
Epifauna
(seeking shelter)
BacteriaPOC
Suspension &
de...
Shorebirds and beach-cast
seaweed
y = 0.0055x + 0.0058
R
2
= 0.9107
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 50 100 150
Tot...
76%
20%
4%
0%
On seaweed
On sand
On Rocks
Atwater line
99%
0%1%0%
Low Tide High Tide
Habitat use by birds on sandy
beaches...
Invertebrates and seaweed
• Majority of fauna found in old seaweed at High Water
Springs (HWS), and in sediment at Low Wat...
Conclusions
• Beach-cast seaweed in Outer Hebrides
supports an abundance of macrofauna
• Seaweed is very important feeding...
Project supported by the INTERREG IVA Programme
Managed by SEUPB
Funders
Coordination Centre:
Scottish Association for Mar...
Seaweed On The Sandy Beaches Of The Outer Hebrides -  An Important Food Source For Coastal Fauna [Kyla Orr]
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Seaweed On The Sandy Beaches Of The Outer Hebrides - An Important Food Source For Coastal Fauna [Kyla Orr]

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Seaweed On The Sandy Beaches Of The Outer Hebrides - An Important Food Source For Coastal Fauna [Kyla Orr]

  1. 1. Seaweed on the sandy beaches of the Outer Hebrides: An important food source for coastal fauna Kyla Orr (PhD student) Supervisors: Sheila Heymans, Tom Wilding and David Hughes Scottish Association for Marine ScienceCoordination Centre: Scottish Association for Marine Science, Oban, Scotland T: +44 (0)1631 559000 F: +44 (0)1631 559001 E: biomara@sams.ac.uk W: www.biomara.org Project supported by the INTERREG IVA Programme Managed by SEUPB
  2. 2. Introduction: Macroalgae for Biofuel • Marine biomass suggested as alternative energy source to terrestrial biomass due to its greater productivity and large surface area available for growth • Wild macroalgae productivity is ~2.8 times higher than that for sugarcane; cultured macroalgae ~ 6.5 times more productive than sugarcane (Gao and McKinley, 1994). (1) Harvesting of attached macroalgae Laminaria spp. Vs Ascophyllum nodosum (2) Growth of macroalgae on long-lines (3) Collection of storm-cast kelp Three possible sources of macroalgae for Biofuel: Ecological role and impacts of removal ?
  3. 3. Study Area North Uist Benbecula South Uist Uists, Outer Hebrides - west coast dominated by soft shores and shallow offshore reefs populated with kelp Large casts of seaweed after gales Long history of seaweed collection from shores
  4. 4. Macroalgae subsidies and coastal communities Detached seaweed Birds Epifauna (seeking shelter) BacteriaPOC Suspension & deposit feeders Fishes Crabs Carnivorous invertebrates Invertebrate detritivores Kelp Beach-cast seaweed Floating seaweed
  5. 5. Shorebirds and beach-cast seaweed y = 0.0055x + 0.0058 R 2 = 0.9107 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 50 100 150 Total Number shorebirds meanseaweedcover(m2/m2beach) Normality Test: Kolmogorov-Smirnov test passed (P = 0.8558) Constant Variance Test: Passed (P = 0.0931) Slope significantly different from zero (p<0.0001) Dunlin Sanderling Turnstone Ringed plover Gull, Larus sp. Pied wagtail Starling Oystercatcher
  6. 6. 76% 20% 4% 0% On seaweed On sand On Rocks Atwater line 99% 0%1%0% Low Tide High Tide Habitat use by birds on sandy beaches with seaweed
  7. 7. Invertebrates and seaweed • Majority of fauna found in old seaweed at High Water Springs (HWS), and in sediment at Low Water (LW) • Abundance of fauna appears to increase with decay stage of seaweed • HWS: average 59,617 individuals/m2 seaweed - dominated by oligochaete worms and fly larvae (Oligochaete abundance can reach 1, 000 000 individuals/m2 ) • LW: average 27,747 individuals/m2 -dominated by the polychaete families Capitellidae and Spionidae. Capitellid worms
  8. 8. Conclusions • Beach-cast seaweed in Outer Hebrides supports an abundance of macrofauna • Seaweed is very important feeding ground for migratory shorebirds, as well as breeders relative to other coastal habitats • Trophic interactions still need to be investigated before questions can be answered about harvesting
  9. 9. Project supported by the INTERREG IVA Programme Managed by SEUPB Funders Coordination Centre: Scottish Association for Marine Science, Oban, Scotland T: +44 (0)1631 559000 F: +44 (0)1631 559001 E: biomara@sams.ac.uk W: www.biomara.org Thank-you

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