1. Kelp trawling in Norway

2. Alginates - 20 - 40% of the dry weight
Found in the cell wall and
intercellular space. Make the alga soft and bendable.
Salt from acids, Mannuronic acid
(M) and Guluronic acid (G).
Soluble in water - Na, K, NH4
Not soluble in water - Ca, Cu, Hg

3. Kelp trawling industry
Harvest tons every year (<0.5% of the total biomass).
Value of the algae ca 25 million NOK
Alginat value ca 500 million NOK
Owned by FMC

4. Blue lines: Global
distrubution of
Laminaria hyperborea
Red line: Area where
kelp is trawled

5. In 2001 they opened for trawling in Sør-Trøndelag
Delivery stations: red dots
Factory in Vormedal by Haugesund

6. Color prints on clothing is one of the biggest markets

7. Food items is another.....

8. Pet food is a huge market!
Not only taste but chewing resistance is important.

9. A pint of beer on a hot summer day…..
Or Champagne in one, two, three!

10. The trawl remove the canopy algae
Number of plants per area after trawling.

11. Ecological effects of kelp trawling
1 year +
old
3 year +
old

12. What happen to the epiphytes after trawling?

13. The hapteron is an important hiding place for many organisms.
Edible crabs
Bivalves - Hiatella arctica
Amphipods
Isopods
Brittle stars
Polychaets
Substrate for sessile animals and benthic algae

14. Canopy height and hapteron volume after trawling

15. Cormorants in a kelp forest
The cormorants dives twice as often in a kelp forest than to be expected from the distribution of this habitat. Likewise, half in the pelagic areas. This means that the cormorants are using the kelp forest as a habitat to search for food.

16. The cormorants diet - different cod fish

17. How much fish do the cormorants eat?
Calculation: One bird eats ca 500 g fish every day
cormorants in Norway = 25 tons per day
= 9125 tons fish per year.

18. Reduction in the fish stock as a result of kelp trawling

19. Comparison of disturbance types
Grazing Trawling
Phase Remove recruits Remove canopy
Phase Old forest Young forest
Phase Grazed Regrowth
Leads to Reduced diversity Reduced diversity
Time scale Long (> 40 yrs) Short (5 - 6 yrs)
Area Regional Local

20. Global
use of
algae