Temperature as determinant factor on the generation of new strains of Kappaphycus alvarezii (Rhodophyta) cultivated in subtropical waters

The process of domestication of the seaweed Kappaphycus alvarezii (Doty) L.M. Liao (Rhodophyta) has been taking place since 1995 and 1996 with the introduction of a brown tetrasporophyte and a pale brown gametophyte (originated from tetraspore progeny cultivated in laboratory) in the Experimental Marine Farm of the Fisheries Institute, Ubatuba Bay, SAo Paulo State, Brazil. From both original strains, 12 new color strains were generated, but only 8 strains have survived. However, new strains with brown color were not observed during the monitoring period. From 2013 to 2022, the occurrence of spontaneous color strains and data of temperature, salinity and water transparency were recorded on the cultivation site. For data analysis, a binary logistic regression model was used to identify the significant association between the presence of generation of the new strains of K. alvarezii (outcome variable) and abiotic data (predictors), and Receiver Operating Characteristic Curve (ROC curve) was used to investigate the probability of giving rise to new strains. Results showed that temperature was significant (p-value=0.025) for generation of new color strains of K. alvarezii. According to the temperature range (18.3 to 31.8 degrees C) used in the model, the probabilities to originate a new strain was 7.6% in temperature of 15 degrees C and 0.01% at 33 degrees C. The occurrence of new strains of K. alvarezii may contribute to the selection of new cultivars for local mariculture.