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The red macroalga Delesseria sanguinea as a UVB-sensitive model organism: selective growth reduction by UVB in outdoor experiments and rapid recording of growth rate during and after UV pulses

Published online by Cambridge University Press:  29 August 2001

SHAOJUN PANG
Affiliation:
Alfred-Wegener-Institut für Polar- und Meeresforschung, Wattenmeerstation Sylt, Hafenstrasse 43, 25992 List/Sylt, Germany
IVÁN GOMEZ
Affiliation:
Alfred-Wegener-Institut für Polar- und Meeresforschung, Wattenmeerstation Sylt, Hafenstrasse 43, 25992 List/Sylt, Germany
KLAUS LÜNING
Affiliation:
Alfred-Wegener-Institut für Polar- und Meeresforschung, Wattenmeerstation Sylt, Hafenstrasse 43, 25992 List/Sylt, Germany
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Abstract

The sublittoral red alga Delesseria sanguinea was pre-cultivated in the laboratory in a predominantly green light field at 10 μmol m−2 s−1 (10 °C), with an approximately 0·5% daily increase in blade area. Such pre-cultivated blades were exposed horizontally in flow-through chambers for 5–6 days in April and May to solar radiation reduced to 19% and 11%, respectively, by neutral density screens. In all three experiments, the full solar spectrum (UVB+UVA+PAR) reduced growth rate significantly to 0–50% of values obtained in PAR alone, while this occurred with UVA+PAR in only one experiment. The growth rate of a Delesseria blade may thus be used as a sensitive and reliable biological indicator of UVB in natural solar radiation at a pre-chosen, neutral reduction level. Rapid measurements of growth rate of apical parts of Delesseria blades during and after UVB+UVA pulses of 2, 3 or 6 h duration were performed in the laboratory by measuring thallus area every 2 min by means of a CCD camera coupled to an on-line, computer-aided image analysis system. A single pulse of 2 or 3 h duration administered during the light phase caused a temporary drop in growth rate during and after the pulse, with recovery starting 2·5 h after the end of the pulse and completed by the end of the light phase. A single 6 h pulse at a biologically effective UVB dose (BEDDNA300 nm) of only 0·5 kJ m−2 reduced growth rate by 55% if administered around noon, but halted growth almost completely if supplied at night, when no photoreactivation was possible. The UVB-sensitive behaviour of Delesseria compares well with the highly sensitive phytoplankton alga Emiliania huxleyi whose growth was reported to be halted at a daily, weighted BEDDNA300 nm of 0·4 kJ m−2 administered during 4 days for 3 h in the middle of the light period.

Type
Research Article
Copyright
© 2001 British Phycological Society

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