Mariculture of Kappaphycus alvarezii (Rhodophyta, Solieriaceae) color strains in tropical waters of Yucatán, México

Three color strains of the n-carrageenan producing red alga Kappaphycus alvarezii were cultured in Dzilam, Yucata ́n, over a 6-month period using the fixed off bottom monoline culture method to determine the technical viability of producing commercially this seaweed in the tropical waters of the Yucata ́n peninsula. Seawater temperature ranged from 28 to 31 C^o, with a daily fluctuation range between 25.9 and 31.9 C^o. Irradiance showed a strong fluctuation along the study period with maximal recorded irradiance during April (881.8 Amol photon m^-2 s^-1). Ammonia accounted for 55.1–89.8% of total DIN depending on the season, and salinity did not change significantly. Temperature was the only environmental factor that explained 96% of the observed variation in K. alvarezii growth rate (R²=0.96). The highest average growth rates obtained were 6.5±1% day^-1 for the red strain, 7.1±1.8% day^-1 for the brown strain, and 8.1±1.6% day^-1 for green strain during June. Lowest growth rates were obtained during August and September for the green strain (2.0±0.6% day^-1). Despite the significant differences in growth between months no significant differences among color strains were found (P > 0.05). The growth rates of K. alvarezii were exponential during April to June. A 10-fold increase in weight was obtained after 30 days in cultivation for all the colored strains. As propagule weight increased the growth rate was reduced. Further, biomass yield (% weight gained) fluctuated as propagule weight increased and averaged 33.2±8.4% for the green, 35.4±6.0% for the red and 36.3±10.8% for the brown strain after 15 days. The highest carrageenan yield was obtained for the green strain (40.7%), whereas average carrageenan yields for the red strain were 32.7±3.9% and 37.5±1.1% for the brown. This study shows that K. alvarezii can be grown in the tropical waters of the Yucata ́n peninsula during the dry and part of the wet season. This period coincided with the closed season of the main fisheries. Thus, seaweed farming could be proposed as an alternative activity in the area.