In vitro carpospore release and germination in <i>Kappaphycus alvarezii</i> (Doty) Doty from Tawi-Tawi, Philippines

Abstract

In vitro carpospore release and germination experiments in Kappaphycus alvarezii (Doty) Doty farmed in Tawi-Tawi, Philippines, were conducted to develop new mariculture techniques for this carrageenophyte traditionally farmed for many years using cuttings. Carpospore release was assessed over 40 d. Maximum production was attained after fertile branches were exposed to air for a period of 0.5 to 1 h at 240 μmol photons m−2 s−1 and subsequently immersed in seawater at 200 μmol photons m−2 s−1 and at 30 and 35 ppt salinities. Highest average carpospore output from days 1 to 5 was 279,000 carpospore/g wet weight of thallus. Nutrient enrichment (F/2 medium) seems to have little effect on spore release. Carpospore settlement occurred 3–5 days after release. The first branch formed after 26 d in diluted F/2 (F/20) media at 35 ppt salinity and 160 μmol photons m−2 s−1. Low irradiance (7 μmol photons m−2 s−1) and low or high salinities (25, 40 ppt) appeared to inhibit release and germling development. Higher levels of nutrients (F/2, F/20) enhanced growth of contaminants and reduced carpospore viability. Germling growth was highest in the more enriched medium (F/2) (10.57% growth d−1) when compared to F/20 medium (2.26 growth d−1).