| Limited toxicity of NH(x) pulses on an early and late successional tropical seagrass species: Interactions with pH and light level. | |
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MedLine Citation:
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PMID: 21536012 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Seagrasses have declined at a global scale due to light reduction and toxicity events, caused by eutrophication and increased sediment loading. Although several studies have tested effects of light reduction and toxicants on seagrasses, there is at present no information available on their interacting effects. In a full-factorial 5-day laboratory experiment, we studied short-term interactive effects of light conditions, pH and reduced nitrogen (NH(x)) in the water layer, mimicking pulses of river discharge, on the tropical early successional species Halodule uninervis and the late successional species Thalassia hemprichii. In contrast to recent results reported for the temperate species Zostera marina, increased NH(x) supply did not affect leaf mortality or photochemical efficiency in H. uninervis and in 7 out of 8 treatments for T. hemprichii. However, both tropical species demonstrated striking differences in nitrogen accumulation, free amino acid composition and free NH(3) accumulation. The increase in tissue nitrogen content was two times higher for H. uninervis than for T. hemprichii. Nitrogen stored as free amino acids (especially asparagine) only increased in H. uninervis. High pH only affected T. hemprichii, but only when not shaded, by doubling its free NH(3) concentrations, concomitantly decreasing its photosynthetic efficiency. Our results indicate that the early successional H. uninervis has higher tolerance to high NH(x) loads as compared to the late successional T. hemprichii. H. uninervis was better able to avoid toxic internal NH(x) levels by further assimilating glutamine into asparagine in contrast to T. hemprichii. Moreover, both tropical species seem to cope much better with high NH(x) than the temperate Z. marina. The implications for the distribution and succession of seagrass species under high nutrient loads are discussed. |
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Authors:
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M J A Christianen; T van der Heide; T J Bouma; J G M Roelofs; M M van Katwijk; L P M Lamers |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-4-9 |
Journal Detail:
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Title: Aquatic toxicology (Amsterdam, Netherlands) Volume: 104 ISSN: 1879-1514 ISO Abbreviation: - Publication Date: 2011 Apr |
Date Detail:
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Created Date: 2011-5-3 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8500246 Medline TA: Aquat Toxicol Country: - |
Other Details:
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Languages: ENG Pagination: 73-79 Citation Subset: - |
Copyright Information:
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Copyright © 2011 Elsevier B.V. All rights reserved. |
Affiliation:
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Department of Environmental Science, Institute for Water and Wetland Research, Radboud University Nijmegen, Faculty of Science, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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