Different light and temperature requirements for survival and growth in three species of Kallymeniaceae (Rhodophyta) from the Mediterranean Sea

Abstract

Abstract Laboratory experiments have shown that light and temperature requirements are critical determining factors for thallus survival and growth of three Mediterranean Kallymeniaceae (Rhodophyta): Verlaquea lacerata, Croisettea requienii, and Meredithia microphylla, and explain their current bathymetric and habitat distribution. Verlaquea lacerata is annual and survived more than 1.5 years in culture, while C. requienii and M. microphylla are perennial and survived more than four and nine years in culture, respectively. The maximum survival was observed at 20–50 µmol photon m−2 s−1 and 10 and 12 °C within an 8:16 h light:dark regime for the three species, while a strong decrease in survival was observed at temperatures of 24 and 26 °C, indicating a weak tolerance to warming temperatures in the Mediterranean. The maximum value of the rate of daily marginal extension per initial surface area was similar in the three species: 0.017 day−1 for V. lacerata (10 °C/8:16 h light:dark regime/10 µmol photon m−2 s−1), 0.021 day−1 for C. requienii (18 °C/14:10 h light:dark regime/10 µmol photon m−2 s−1), and 0.017 day−1 for M. microphylla (12 °C/8:16 h light:dark regime/20 µmol photon m−2 s−1). The experiments permitted the establishment of culture conditions for the target species, and the successful culture of marginal fragments indicates the possibility of indefinitely maintaining the species in the laboratory for bioconservation purposes.