Responses of the Mediterranean seagrass Posidonia oceanica to hypersaline stress duration and recovery

Marín-Guirao, Lázaro; Sandoval‐Gil, Jose Miguel; Bernardeau-Esteller, Jaime; Ruiz, Juan Manuel García; Sánchez-Lizaso, José Luis

doi:10.1016/j.marenvres.2012.12.001

Cited by 60 publications

(58 citation statements)

References 64 publications

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“…These osmolytes enable seagrasses to exclude Na+ and Cl- ions even at very high concentrations [3], [15]. Exceedance of optimum salinity and disruption of cellular processes affects photosynthetic efficiency and leads to reduced growth rates and morphological changes and eventual mortality [11], [15]–[19].…”

Section: Introductionmentioning

confidence: 99%

“…The duration of exposure affects the level of impact on plant fitness and seagrasses may recover following brief levels of exposure to salinity stress but may fail to recover after prolonged stress [15], [19]. Furthermore, the rate of salinity change affects plant health, with incremental salinity change increasing plant survivorship [11], [12], [19].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the rate of salinity change affects plant health, with incremental salinity change increasing plant survivorship [11], [12], [19]. This is an important consideration when testing plant survivorship as hypo-salinity changes are rarely sudden – even though experimental approaches frequently assume so – but rather they occur gradually as flood waters mix with saline waters [5], [12].…”

Section: Introductionmentioning

confidence: 99%

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Seagrass Proliferation Precedes Mortality during Hypo-Salinity Events: A Stress-Induced Morphometric Response

et al. 2014

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seagrass Proliferation Precedes Mortality during Hypo-Salinity Events: A Stress-Induced Morphometric Response

et al. 2014

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“…, ; Marín‐Guirao et al . ). In contrast to the low inter‐tidal morphotype, which took longer (3–7 h) to reach the minimum values of Ψ w and Ψ π in the acclimation to emersion, the high inter‐tidal morphotype rapidly osmoregulated after 30 min of air exposure.…”

Section: Discussionmentioning

confidence: 97%

“…Ions (Cl − , K + , Na + , Ca 2+ and Mg 2+ ) (mg·g −1 DW) were determined by ionic chromatography according to the methods detailed in Marín‐Guirao et al . ().…”

Section: Methodsmentioning

confidence: 97%

Plant–water relations of intertidal and subtidal seagrasses

et al. 2014

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This work represents the first contribution to (i) examine the changes in plant‐water relations of an inter‐tidal seagrass during air exposure (Zostera noltii), and (ii) compare the water status descriptors between inter‐tidal‐ and subtidal‐adapted species (Cymodocea nodosa, Zostera marina). Two different morphotypes of Z. noltii that develop in the highest and lowest inter‐tidal levels in the Portuguese lagoon of Ria Formosa were exposed to natural emersion periods under laboratory conditions, and the evolution of leaf water relations and osmolytes (ions, proline and non‐structural carbohydrates) was measured. Both morphotypes regulated their water potential (Ψw) by reducing the osmotic potential (Ψπ) through osmolyte accumulation, but only high inter‐tidal plants were able to do this by adjusting the turgor pressure through cell wall hardening. This is a conservative mechanism for osmotic acclimation, which occurred only after long emersion periods (7 h). After a rapid increase in ion concentration under air exposure, the high inter‐tidal morphotype replaced them by more physiologically compatible solutes (proline and non‐structural carbohydrates) to maintain the osmotic adjustment. Altered ionic homeostasis was found in low inter‐tidal plants when exposed to such unnatural, long emersion periods. Osmotic unbalances were also observed during the submerged recovery phase. Descriptors of leaf pressure–volume (P–V) curves and Höfler diagrams were derived for seagrasses for the first time. They support the divergences in water relations observed between inter‐tidal and subtidal seagrasses according to their vertical distribution. More negative water and osmotic potentials and higher rigidity of cell walls (higher elastic modulus, ε) were found to be specific osmotic adaptations of seagrasses to the inter‐tidal.

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Long‐term acclimation to reciprocal light conditions suggests depth‐related selection in the marine foundation speciesPosidonia oceanica

Dattolo

Marín-Guirao

Ruiz

et al. 2017

Ecology and Evolution

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Phenotypic differences among populations of the same species reflect selective responses to ecological gradients produced by variations in abiotic and biotic factors. Moreover, they can also originate from genetic differences among populations, due to a reduced gene flow. In this study, we examined the extent of differences in photo‐acclimative traits of Posidonia oceanica (L.) Delile clones collected above and below the summer thermocline (i.e., −5 and −25 m) in a continuous population extending along the water depth gradient. During a reciprocal light exposure and subsequent recovery in mesocosms, we assessed degree of phenotypic plasticity and local adaptation of plants collected at different depths, by measuring changes in several traits, such as gene expression of target genes, photo‐physiological features, and other fitness‐related traits (i.e., plant morphology, growth, and mortality rates). Samples were also genotyped, using microsatellite markers, in order to evaluate the genetic divergence among plants of the two depths. Measures collected during the study have shown a various degree of phenotypic changes among traits and experimental groups, the amount of phenotypic changes observed was also dependent on the type of light environments considered. Overall plants collected at different depths seem to be able to acclimate to reciprocal light conditions in the experimental time frame, through morphological changes and phenotypic buffering, supported by the plastic regulation of a reduced number of genes. Multivariate analyses indicated that plants cluster better on the base of their depth origin rather than the experimental light conditions applied. The two groups were genetically distinct, but the patterns of phenotypic divergence observed during the experiment support the hypothesis that ecological selection can play a role in the adaptive divergence of P. oceanica clones along the depth gradient.

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Responses of the Mediterranean seagrass Posidonia oceanica to hypersaline stress duration and recovery

Cited by 60 publications

References 64 publications

Seagrass Proliferation Precedes Mortality during Hypo-Salinity Events: A Stress-Induced Morphometric Response

Seagrass Proliferation Precedes Mortality during Hypo-Salinity Events: A Stress-Induced Morphometric Response

Plant–water relations of intertidal and subtidal seagrasses

Long‐term acclimation to reciprocal light conditions suggests depth‐related selection in the marine foundation speciesPosidonia oceanica

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