This presentation was given at the 2003 Phycological Society of Southern Africa meeting in 2003. The presentation asks whether a seaweed extract (normally used on land plants) can also be used to increase seaweed produciton.

1. Can kelp extract (K ELPAK  ) be useful in seaweed mariculture? Bolton JJ 1 , Robertson-Andersson D, Njobeni A 1 , Leitao D 1 , Anderson RJ 2 and Ruck, K 3 1 Botany Department, U CT 2 Seaweed Unit, M&CM 3 Jacobsbaai Sea Products

5. Gracilaria : weight of tips after 14 days a a b b c

6. Gracilaria : weight of tips after 14 days a a ac b c d

7. Gracilaria : number of branches after 14 days

8. Gracilaria : number of branches after 14 days

13. JSP Kelpak experiments 3 replicates of each treatment EXPT 1: Concentrations of Kelpak (1:5000, 1:2500, 1:500) added to turbot/abalone effluent EXPT 2: Chosen concentration of Kelpak in two types of effluent, with and without fertiliser supplement

14. Gracilaria at JSP: RGR in different Kelpak concns. (Run 1)

15. Temperature in JSP tanks: June/July 2002 (SD, maximum and minimum)

16. CONTROL (no KELPAK)

17. KELPAK @ 1:5000

18. KELPAK @ 1: 2500

19. KELPAK @ 1: 500

20. Gracilaria : Number of branches per 10cm apex (Runs 1 & 2)

22. E ffect s of various K elpak dilutions in turbot effluent on R GR (% d -1 ) o f Ulva at JSP

23. Effects of K elpak in turbot effluent on tissue N of Ulva at JSP

24. Fertiliser treatment As used on I&J farm at Gansbaai 6 parts Maxiphos to 1 part ammonium sul ph ate Added weekly, for 8 hours in non-flowing water in the day (08:30 to 16:30) Concentration in water after fertilization: 575  M ammonium/ 280  M phosphate

25. Effect of 1:2500 Kelpak and fertilizer (separately or combined) in turbot effluent on RGR (% d -1 ) of Ulva lactuca at JSP .

26. Effects of Kelpak (1:2500) and fertilizer in turbot effluent on tissue N (mg N per g) Ulva at JSP.

27. Abalone effluent: RGR’s

28. Abalone effluent: tissue N