Indirect and direct effects of salinity on the quantity and quality of total amino acids in Ulva ohnoi (Chlorophyta).

Salinity can affect the quantity and quality of total amino acids (TAAs) in seaweeds indirectly by altering growth rates and thereby diluting or concentrating the amino acid content of the biomass, or directly by altering the synthesis of specific amino acids and osmolytes. This study attempted to partition the indirect and direct effects of salinity on the quantity and quality of TAAs in the green seaweed Ulva ohnoi by culturing it under a range of salinities without nutrient limitation. Both the quantity and quality of TAAs varied across the salinity treatments.

Variation in amino acid content and its relationship to nitrogen content and growth rate in Ulva ohnoi (Chlorophyta).

To evaluate the quantitative and qualitative changes in amino acids related to internal nitrogen content and growth rate of Ulva ohnoi, the supply of nitrogen to outdoor cultures of the seaweed was manipulated by simultaneously varying water nitrogen concentrations and renewal rate. Both internal nitrogen content and growth rate varied substantially, and the quantitative and qualitative changes in amino acids were described in the context of three internal nitrogen states: nitrogen-limited, metabolic, and luxury. The nitrogen limited state was defined by increases in all amino acids with increasing nitrogen content and growth up until 1.

Feeding preferences and the nutritional value of tropical algae for the abalone Haliotis asinina.

Understanding the feeding preferences of abalone (high-value marine herbivores) is integral to new species development in aquaculture because of the expected link between preference and performance. Performance relates directly to the nutritional value of algae--or any feedstock--which in turn is driven by the amino acid content and profile, and specifically the content of the limiting essential amino acids. However, the relationship between feeding preferences, consumption and amino acid content of algae have rarely been simultaneously investigated for abalone, and never for the emerging target species Haliotis asinina.