<p><i>Kappaphycus alvarezii</i> (Doty) L.M. Liao (Rhodophyta) is a widely studied species that provides raw material for carrageenan production, however, mass production struggles to maintain species viability owing to low genetic variability. New strains of <i>K. alvarezii</i> with different phenotypes have emerged from sea cultivation in Ubatuba bay, southeastern Brazil. The present study aimed to evaluate growth rates, photosynthesis, and pigment and protein concentrations in four <i>K. alvarezii</i> strains, including the brown tetrasporophyte (T-br) and three gametophytic strains: “Edison de Paula” pale-brown gametophyte (E-br), which originated new strains, named light-green (E-lg) and greenish yellow (E-gy) gametophytes. These strains were cultivated in a floating raft system for one year at the Experimental Marine Farm of the Fisheries Institute. T-br tetrasporophyte showed higher growth rates and higher phycobiliprotein concentrations than the gametophytic strains. Maximum electron transport rates (ETR_max) and irradiance saturation (E_k) varied among strains and seasons, and the E-lg and E-gy gametophytes had higher ETR_max and E_k than the T-br tetrasporophyte and E-br gametophyte. Results of principal component analyses (PCA) evidenced three groups: E-lg and E-gy gametophytes with higher ETR_max and E_k, T-br tetrasporophyte and E-br gametophyte formed distinct groups related to phycobiliprotein concentrations. In conclusion, our results corroborate the significant differences between T-br tetrasporophyte and the three gametophytic strains of <i>K. alvarezii,</i> and results of PCA showed two distinct groups of gametophytic strains, although E-lg and E-gy gametophytes were originated from the E-br gametophyte. Furthermore, novel strains are needed to increase genetic diversity and to expand the cultivation of <i>K. alvarezii</i> in the region.</p>