Seagrass survival during pulsed turbidity events: the effects of light deprivation on the seagrasses Halodule pinifolia and Halophila ovalis

Longstaff, Benjamin J. and Dennison, William Cullen (1999) Seagrass survival during pulsed turbidity events: the effects of light deprivation on the seagrasses Halodule pinifolia and Halophila ovalis. Aquatic Botany, 65 1-4: 105-121. doi:10.1016/S0304-3770(99)00035-2


Author Longstaff, Benjamin J.
Dennison, William Cullen
Title Seagrass survival during pulsed turbidity events: the effects of light deprivation on the seagrasses Halodule pinifolia and Halophila ovalis
Formatted title
Seagrass survival during pulsed turbidity events: the effects of light deprivation on the seagrasses Halodule pinifolia and Halophila ovalis
Journal name Aquatic Botany   Check publisher's open access policy
ISSN 0304-3770
Publication date 1999-11
Sub-type Article (original research)
DOI 10.1016/S0304-3770(99)00035-2
Volume 65
Issue 1-4
Start page 105
End page 121
Total pages 17
Place of publication Amsterdam, Netherlands
Publisher Elsevier Science
Collection year 1999
Language eng
Subject C1
270702 Marine and Estuarine Ecology (incl. Marine Ichthyology)
770300 Marine Environment
Formatted abstract
Pulsed turbidity events caused by factors such as flooding rivers have the potential to seriously impact seagrass communities by depriving the plants of all available light. The effects of light deprivation was investigated on the survival, morphology and physiology of the tropical seagrasses Halodule pinifolia and Halophila ovalis growing in the South-East Gulf of Carpentaria, Australia, a region where pulsed flood events are common. Additionally, physiological and morphological responses to light availability along natural gradients were examined. Responses to both experimental and natural light gradients were investigated for their potential use as indicators of impending seagrass loss during pulsed turbidity events. H. pinifolia was deprived of light for 80 days using in situ shade screens and the following parameters measured at three depths and under the shade screens: biomass, shoot density, canopy height, amino acid content, chlorophyll content, δ13C signature, %C and sugar concentration. The quantity of light was extremely variable, with mean daily irradiances between 9–12 mol photons m−2 day−1, and a range of 0.05–42 mol photons m−2 day−1. H. pinifolia leaf amino acid content increased with increased water depth (from 8 to 18 μmol g fresh wt.), chlorophyll a to b ratio decreased (from 2.4 to 2.1) and δ13C values became more negative (from −9 to −12). H. ovalis displayed little tolerance to light deprivation, with plant death occurring after 38 days in the dark. H. pinifolia showed a high degree of tolerance to light deprivation with no biomass loss before day 38 and complete die-off predicted after 100 days. Shoot density, biomass and canopy height all declined after 38 days. Physiological parameters that responded significantly to the light deprivation were the amino acids which increased (from 20 to 80 μmol g fresh wt.), the chlorophyll a to b ratio which decreased (from 2.5 to 2.1) and the values which became more negative (from −9 to −10). Changes in leaf physiology (e.g. amino acid content, chlorophyll content and δ13C) occurred before morphological changes (e.g. biomass, shoot density, canopy height) or die-off, and were thus considered to be potential indicators of impending seagrass die-off during light deprivation. In conclusion, only long duration (>38 days) pulsed turbidity events would have a detrimental impact on H. pinifolia growing in the Gulf of Carpentaria and that by assessing specific physiological responses, seagrass loss during pulsed turbidity events can predicted.
©1999 Elsevier Science B.V. All rights reserved.
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Agriculture and Food Sciences
 
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Created: Tue, 10 Jun 2008, 14:14:16 EST