Seagrass proliferation precedes mortality during hypo-salinity events: a stress-induced morphometric response

Collier, Catherine J., Villacorta-Rath, Cecilia, van Dijk, Kor-jent, Takahashi, Miwa, and Waycott, Michelle (2014) Seagrass proliferation precedes mortality during hypo-salinity events: a stress-induced morphometric response. PLoS ONE, 9 (4). e94014. pp. 1-11.

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DOI: 10.1371/journal.pone.0094014

View at Publisher Website: http://dx.doi.org/10.1371/journal.pone.0...

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Abstract

Halophytes, such as seagrasses, predominantly form habitats in coastal and estuarine areas. These habitats can be seasonally exposed to hypo-salinity events during watershed runoff exposing them to dramatic salinity shifts and osmotic shock. The manifestation of this osmotic shock on seagrass morphology and phenology was tested in three Indo-Pacific seagrass species, Halophila ovalis, Halodule uninervis and Zostera muelleri, to hypo-salinity ranging from 3 to 36 PSU at 3 PSU increments for 10 weeks. All three species had broad salinity tolerance but demonstrated a moderate hypo-salinity stress response – analogous to a stress induced morphometric response (SIMR). Shoot proliferation occurred at salinities <30 PSU, with the largest increases, up to 400% increase in shoot density, occurring at the sub-lethal salinities <15 PSU, with the specific salinity associated with peak shoot density being variable among species. Resources were not diverted away from leaf growth or shoot development to support the new shoot production. However, at sub-lethal salinities where shoots proliferated, flowering was severely reduced for H. ovalis, the only species to flower during this experiment, demonstrating a diversion of resources away from sexual reproduction to support the investment in new shoots. This SIMR response preceded mortality, which occurred at 3 PSU for H. ovalis and 6 PSU for H. uninervis, while complete mortality was not reached for Z. muelleri. This is the first study to identify a SIMR in seagrasses, being detectable due to the fine resolution of salinity treatments tested. The detection of SIMR demonstrates the need for caution in interpreting in-situ changes in shoot density as shoot proliferation could be interpreted as a healthy or positive plant response to environmental conditions, when in fact it could signal pre-mortality stress.


Item ID:	32817
Item Type:	Article (Research - C1)
ISSN:	1932-6203
Keywords:	floods, flowering, tropical seagrass, shoot density, stress-induced morphometric response, response model, thresholds
Additional Information:	© 2014 Collier et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funders:	Australian's Government National Environmental Research Program (NERP) Tropical Hub
Projects and Grants:	NERP Project 5.3
Research Data:	http://e-atlas.org.au/nerp-te/gbr-jcu-seagrass-vulnerability-5-3
Date Deposited:	30 May 2014 00:33
FoR Codes:	06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060701 Phycology (incl Marine Grasses) @ 60% 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060705 Plant Physiology @ 20% 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050209 Natural Resource Management @ 20%
SEO Codes:	96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 40% 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 40% 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 20%
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