Growth and carrageenan composition of two populations of the New Zealand carrageenophyte Sarcothalia lanceata (Gigartinaceae, Rhodophyta)

Sarcothalia lanceata is a broad-bladed, New Zealand red alga. The tetrasporic life stage contains a lambda-carrageenan that has a strong potential for commercial utilisation. The male and female gametophytic life stages contain kappa-II carrageenan that also has commercial potential. However, fundamental information on the growth and variation in carrageenan content of this species in the wild is necessary to underpin possible aquaculture of this species. Therefore, growth in blade length and width was assessed for male and female gametophytes, and tetrasporophytes in two S. lanceata populations in New Zealand’s South Island, and monthly seawater nutrient and tissue nutrients, and carrageenan constituent sugar levels were analysed. Blade length did not vary significantly over time or between life history phases; however, blade width varied significantly for both factors with most temporal variation occurring in male blades. Analysis of seawater and tissue nutrient levels suggested that these populations are nutrient limited year-round. Constituent sugars varied temporally and between life history phases in most cases. Relative 3,6-anhydrogalactitol peracetate (for the males and females) and galactitol peracetate levels (all life stages) were higher in winter than in summer, while glucitol peracetate and xylitol peracetate levels were generally lower in winter than summer. The distinctive morphologies of the male and female plants of this species mean there is potential to cultivate and then separately harvest male and female plants in addition to tetrasporophytic plants. Male blades contain more 3,6-anhydrogalactitol peracetate and galactitol peracetate than female blades, and their morphology may make them less prone to breakage in an aquaculture situation. Experimentation on spore release and growth and the potential effects of nutrient manipulation on early stages are suggested as the direction of future research.