Effects of Deep Seawater on the Growth of a Green Alga, Ulva sp. (Ulvophyceae, Chlorophyta)

doi:2003.18.2.129

Algae > Volume 18(2); 2003 > Article

Algae 2003;18(2): 129-134. doi: https://doi.org/10.4490/ALGAE.2003.18.2.129

Kazuyo Matsuyama, Yukihiko Serisawa, Toshimitsu Nakashima

Marine Ecosystems Research Department, Japan Marine Science and Technology Center, Marine Biosystems Research Center, Chiba University

ABSTRACT

In order to examine the effects of deep seawater (mesopelagic water in the broad sense) on the growth of macro-algae, the growth and nutrient uptake (nitrate and phosphate) of Ulva sp. (Ulvophyceae, Chlorophyta) were investigated by cultivation in deep seawater (taken from 687 m depth at Yaizu, central Japan, in August 2001), surface seawater (taken from 24 m depth), and a combination of the two. Culture experiments were carried out in a continuous water supply system and an intermittent water supply system, in which aerated 500-mL flasks with 4 discs of Ulva sp.(cut sections of ca. 2 cm²)were cultured at 20℃ water temperature, 100 μmol photons m〈sup〉-2〈/sup〉?s〈sup〉-1〈/sup〉light intensity, and a 14:10 light: dark cycle. Nutrient uptake by Ulva sp. was high in all seawater media in both culture systems. The frond area, dry weight, chlorophyll a content, dry weight per unit area, and chlorophyll a content per unit area of Ulva sp. at the end of the experimental period were the highest in deep seawater and the lowest in surface seawater in both culture system. These values, except for dry weight per unit area and chlorophyll a content per unit area, for each seawater media in the intermittent water supply system were higher than those in the continuous water supply system. We conclude that not only deep seawater as the culture medium but also the seawater supply system is important for effective cultivation of macro-algae.

Key words: deep seawater, frond area, growth, nutrient uptake, phosphate, Ulva sp.