The Israeli Journal of Aquaculture - Bamidgeh 54(2), 2002
The Annual Dan Popper Symposium


BIOFILTERS OF THE SEAWEED ULVA LACTUCA IN INTEGRATED MARICULTURE:
WHAT AERATION REALLY DOES TO NUTRIENT UPTAKE,
YIELD AND PROTEIN CONTENT OF THE SEAWEED


Flower E. Msuya¹,² *, Lilach Shauli¹, Amir Neori¹*

1 Israel Oceanographic and Limnological Research, National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel
2 Department of Plant Sciences, Tel Aviv University, Tel Aviv 69987, Israel


Abstract

Cultured seaweed performs better in air-agitated water. Aeration may affect vertical light fields, removal of excess oxygen or nutrient diffusion and uptake. To evaluate these possibilities, the seaweed Ulva lactuca was cultured in tanks (0.6 m³ ,1 m²). Each tank received intensive fishpond effluents at 0.85 m³/h and one of four water agitation regimes and two total ammonia nitrogen (TAN) fluxes. The agitation regimes were: standard aeration, siphon (varying water levels), combined aeration and siphon, and water exchange only (no aeration,no siphon). The TAN fluxes were high (37 g TAN/m²/day) and low (7 g TAN/m²/day).

With high TAN fluxes, TAN was removed at 6.2 g/m²/day with insignificant variation (p=0.11) between agitation treatments. Yields (268 g/m²/day) and protein contents (43% in dw) also varied insignificantly between agitation treatments. With low TAN fluxes, TAN was removed at 3.4 g/m²/day but the variation between agitation treatments was significant (p= 0.04). The yield was higher (335 g/m²/day) and the protein content was lower (36% in dw), both with insignificant variation between agitation treatments.

Agitation enhances nutrient diffusion into the algae, when nutrients are limiting, by reducing the thickness of the boundary layer around the seaweed. The practical message from this study is that with a high nutrient supply, seaweed biofilters can function well with any form of water agitation.

*Corresponding author. E-mail: flowerem@hotmail.com or neori@ocean.org.il

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