| |
Effect of ultraviolet radiation on the bioavailability of marine
diatom-derived low-molecular-weight dissolved organic matter
Takeshi Naganumaa,b Ikuko
Fukaia, Yuki Murakamib,
Toru Nakanec, Shunji Sukizakic
aFaculty
of Applied Biological Science, Hiroshima University, 1-4-4 Kagamiyama,
Higashi-hiroshima, 739-8528 Japan. Telephone: +81-824-24-7986;
FAX: +81-824-22-7059; electronic-mail: takn@ipc.hiroshima-u.ac.jp.
bSchool
of Biosphere Sciences, Hiroshima University, 1-4-4 Kagamiyama,
Higashi-hiroshima, 739-8528 Japan.
cMarine
Biological Research Institute of Japan, 4-3-16 Yutaka-cho, Shinagawa-ku,
Tokyo, 142-0042 Japan |
Abstract
The effect of ultraviolet irradiation on diatom-derived
dissolved organic matter used as a bacterial growth substrate was
investigated. The dissolved organic matter fraction of 100-1000
daltons (low-molecular-weight) was prepared from a culture of a
marine diatom, Chaetoceros sp. This dissolved matter was
then exposed to ultraviolet-A and -B irradiation at naturally occurring
intensities of 0-44 kJ m-2. The
concentration of low molecular weight dissolved organic matter decreased
as ultraviolet irradiation increased, which was a reflection of
photolytic mineralization of the material.
The irradiated organic matter was added to the culture
of a Vibrio strain to assess its bioavailability. Bacterial
growth was enhanced with the irradiated material, which was probably
due to the photolytic production of more bioavailable monomeric
substrates. The loss of the low molecular weight dissolved organic
material concentration was counterbalanced by enhanced bioavailability.
Thus, ultraviolet irradiation of the natural diatom-derived low
molecular weight dissolved organic matter pool may be net-positive
for the growth of marine bacteria.
Keywords: Photolysis; Vibrio sp. Chaetoceros
sp; Bacterial growth
|
