Comparing the low‐salinity tolerance of <i><scp>U</scp>lva</i> species distributed in different environments

Abstract

Summary The green macroalgal genus U lva ( U lvales, U lvophyceae, C hlorophyta) is distributed worldwide from marine to freshwater environments. Comparative analyses of hyposalinity tolerance among marine, brackish, and freshwater U lva species were performed by fluorescein diacetate viability counts. The subtidal marine species U lva sp., collected from a depth of 30 m, showed the poorest tolerance to low salinity. This species died in 5 practical salinity units ( PSU ) artificial seawater or freshwater within 1 day. Its closely related species U . linza L . (an intertidal species) and U . prolifera M üller (a brackish species) showed varying tolerances to low salinity. After 7 days of freshwater exposure, the viability of U . linza L . decreased to approximately 20%, while U . prolifera M üller showed nearly 100% viability. The freshwater species U . limnetica I chihara et S himada, not yet found in coastal areas, was highly viable in seawater.