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Dugong grazing and turtle cropping: grazing optimization in tropical seagrass systems?

Aragones, Lemnuel; Lawler, I; Foley, William; Marsh, Helene

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Grazing by dugongs and cropping by green turtles have the capacity to alter the subsequent nutritional quality of seagrass regrowth. We examined the effects of simulated light and intensive grazing by dugongs and cropping by turtles on eight nutritionally relevant measures of seagrass chemical composition over two regrowth periods (short-term, 1-4 months; long-term, 11-13 months) at two seagrass communities (a mixed species community with Zostera capricorni, Halophila ovalis, Halodule...[Show more]

dc.contributor.authorAragones, Lemnuel
dc.contributor.authorLawler, I
dc.contributor.authorFoley, William
dc.contributor.authorMarsh, Helene
dc.date.accessioned2015-12-10T22:59:31Z
dc.identifier.issn0029-8549
dc.identifier.urihttp://hdl.handle.net/1885/61123
dc.description.abstractGrazing by dugongs and cropping by green turtles have the capacity to alter the subsequent nutritional quality of seagrass regrowth. We examined the effects of simulated light and intensive grazing by dugongs and cropping by turtles on eight nutritionally relevant measures of seagrass chemical composition over two regrowth periods (short-term, 1-4 months; long-term, 11-13 months) at two seagrass communities (a mixed species community with Zostera capricorni, Halophila ovalis, Halodule uninervis, Cymodocea rotundata and C. serrulate; and a monospecific bed of Halodule uninervis) in tropical Queensland, Australia. The concentrations of organic matter, total nitrogen, total water-soluble carbohydrates, total starch, neutral detergent fiber, acid detergent fiber, acid lignin, as well as the in vitro dry matter digestibility (IVDMD) were measured in the leaves and below-ground parts of each species using near-infrared reflectance spectroscopy (NIRS). Regrowth of preferred species such as H. ovalis and H. uninervis from simulated intensive dugong grazing after a year exhibited increased (by 35 and 25%, respectively, relative to controls) whole-plant N concentrations. Similarly, regrowth of H. ovalis from simulated turtle cropping showed an increase in the leaf N concentration of 30% after a year. However, these gains are tempered by reductions in starch concentrations and increases in fiber. In the short-term, the N concentrations increased while the fiber concentrations decreased. These data provide experimental support for a grazing optimization view of herbivory in the tropical seagrass system, but with feedback in a different manner. Furthermore, we suggest that in areas where grazing is the only major source of natural disturbance, it is likely that there are potential ecosystem level effects if and when numbers of dugongs and turtles are reduced.
dc.publisherSpringer
dc.sourceOecologia
dc.subjectKeywords: lignin; nitrogen; chemical composition; cropping practice; grazing; infrared spectroscopy; light effect; marine mammal; nutritive value; optimization; regrowth; seagrass; turtle; animal; article; Australia; carbohydrate metabolism; dietary fiber; Dugong; Cymodocea; Green turtle; Halodule; Halophila; Nutritional quality; Zostera
dc.titleDugong grazing and turtle cropping: grazing optimization in tropical seagrass systems?
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume149
dc.date.issued2006
local.identifier.absfor060205 - Marine and Estuarine Ecology (incl. Marine Ichthyology)
local.identifier.ariespublicationu9511635xPUB588
local.type.statusPublished Version
local.contributor.affiliationAragones, Lemnuel, James Cook University
local.contributor.affiliationLawler, I, James Cook University
local.contributor.affiliationFoley, William, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationMarsh, Helene, James Cook University
local.description.embargo2037-12-31
local.bibliographicCitation.startpage635
local.bibliographicCitation.lastpage647
local.identifier.doi10.1007/s00442-006-0477-1
dc.date.updated2015-12-10T08:13:37Z
local.identifier.scopusID2-s2.0-33748924346
CollectionsANU Research Publications

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