Effect of water aeration and nutrient load level on biomass yield, N uptake and protein content of the seaweed Ulva lactuca cultured in seawater tanks
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Date
2008
Authors
Journal Title
Journal ISSN
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Publisher
Springer
Abstract
The effects of 16 different combinations of
nutrient load and agitation on yield, nutrient uptake and
proximate chemical composition of the seaweed Ulva
lactuca cultured in tanks were evaluated. Intensive fishpond
outflow passed through seaweed tanks at four nutrient
loading levels and four water agitation combinations of
water exchange, bottom aeration and frequently changing
water levels (an accelerated tide regime). Specific results
from these outdoor experiments were examined further under
controlled conditions in laboratory experiments. Agitation
treatments affected the performance of U. lactuca only under
TAN (NH3 þ NHþ
4 ) load levels below 4 g N m−2 day−1;
biofiltration of TAN was the parameter most affected.
Biomass yields at each of the four nutrient loading levels
were not significantly different between the agitation treatments.
Protein content increased significantly with increasing
nutrient loading. The agitation treatments had a slight effect
on seaweed protein content only at the lowest nutrient
loading levels. There were no significant differences in
dissolved oxygen concentration, pH, and temperature among
the agitation treatments at all nutrient loading levels. Under
laboratory conditions, growth rates, protein content, and
photosynthetic and biomass yield of the seaweed were
affected by water velocity under low nutrient concentrations.
It is concluded that the effect of air agitation under the conditions of these experiments was not directly related to
photosynthesis, excess dissolved oxygen, or carbon limitation,
but to the diffusion of macro nutrients from the water to
the seaweed. Therefore, once nutrient concentrations are high
enough (above about 4 μM of TAN with the other nutrients
in their corresponding proportions), aeration per se is not
essential for effective growth and biofiltration by seaweeds.
Description
Keywords
Seaweed biofiltration, Water movement, Agitation treatment, Fishpond effluents, Nutrient uptake, Yield
Citation
Msuya F.E. and Neori A. 2008. Factors that determine the performance of the seaweed Ulva lactuca in intensive tank culture. Journal of Applied Phycology 20: 1021-1031