Impact of light limitation on seagrasses

Ralph, Peter J.; Durako, Michael J.; Enríquez, Susana; Collier, Catherine; Doblin, Martina A.

doi:10.1016/j.jembe.2007.06.017

Cited by 397 publications

(320 citation statements)

References 121 publications

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“…This confirms previous reports that H. ovalis can cope with short-term shading through physiological rather than morphological adaptation . Following the 21-day recovery, the persistence of larger leaves with lower sugar content in shaded than in unshaded plants is consistent with shading triggering a delayed 'light-harvesting' response through increased surface area, as observed in other seagrasses (Ralph et al 2007). The 60% higher initiation of apices with shading was probably a similar light stress response, which increased the potential for leaf production and harvesting of light, although this potential was not realised as there was no difference in the actual branching frequency (conversion of apices into new modules with leaves) between unshaded and shaded plants, and hence no difference in leaf density.…”

Section: Responses To Shadingsupporting

confidence: 75%

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Effects of multiple disturbances in seagrass meadows: shading decreases resilience to grazing

Eklöf

McMahon

Lavery

2009

Mar. Freshwater Res.

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Abstract. Ecosystem shifts are often associated with multiple disturbances, but limited knowledge on the mechanisms involved hampers management. This study investigated how short-term shading affected the resilience of the seagrass Halophila ovalis to grazing by black swans (Cygnus atratus) -a historically dominant grazer currently recovering from hunting and habitat loss -in south-western Australian estuaries, using field surveys and a grazing-shading experiment. Black swans were heterogeneously distributed and, in a high-density site, consumed 23% of seagrass production. Seagrasses recovered rapidly from a single disturbance (i.e. short-term shading or grazing), even though shading alone halved carbohydrate content. When seagrasses were exposed to both disturbances, recovery depended on the type of grazing; where grazing was confined to leaves, leaf densities recovered within 3 weeks, but where grazing was on both leaves and rhizomes there was no recovery. Shading increased the frequency of apex initiation, as did rhizome grazing, but only if the plants had not been shaded. This indicates that shading alters the flow of energy needed to produce apices and leaves following disturbance on rhizomes. Based on the historical swan densities and continuing recurring phytoplankton blooms, management actions reintroducing swans without controlling algal blooms could have an on impact seagrass resilience and associated organisms.

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Section: Responses To Shadingsupporting

confidence: 75%

“…. However, climax species have greater carbohydrate storages (due to thicker rhizomes) and can therefore withstand longer shading (Ralph et al 2007). In contrast, herbivory is a natural and intrinsic disturbance on seagrasses (for a review, see Valentine and Duffy 2006).…”

Section: Introductionmentioning

confidence: 99%

Effects of multiple disturbances in seagrass meadows: shading decreases resilience to grazing

Eklöf

McMahon

Lavery

2009

Mar. Freshwater Res.

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“…Macroalgae cover may reduce the C content of seagrasses for two reasons. First, light reduction by macroalgae mats may contribute to a decrease in photosynthetic activity of seagrasses (Brun et al, 2003;Huntington and Boyer, 2008;Peralta et al, 2002;Ralph et al, 2007). This can cause a subsequent reduction in root and rhizome growth of seagrasses (Hemminga, 1998), as rhizomes and roots are heterotrophic tissues depending on basipetal translocation of photosynthates and oxygen from active photosynthesizing leaves to persist (Zimmerman and Alberte, 1996).…”

Section: Fast Indicator Responses Of Seagrassesmentioning

confidence: 99%

Combined nutrient and macroalgae loads lead to response in seagrass indicator properties

Han

Soissons

Bouma

et al. 2016

Marine Pollution Bulletin

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a b s t r a c t a r t i c l e i n f oExcess nutrients are potential factors that drive phase shifts from seagrasses to macroalgae. We carried out a manipulative field experiment to study the effects of macroalgae Ulva pertusa loading and nutrient addition to the water column on the nitrogen (N) and carbon (C) contents (i.e., fast indicators) as well as on the morphology and structure (i.e., slow indicators) of Zostera marina. Our results showed rapid impact of increased macroalgae and nutrient load on Z. marina C/N ratios. Also, macroalgae addition resulted in a trend of decreasing belowground biomass of seagrasses, and nutrient load significantly decreased above to belowground biomass ratio. Although some morphological/structural variables showed relatively fast responses, the effects of short-term disturbance by macroalgae and nutrients were less often significant than on physiological variables. Monitoring of seagrass physiological indicators may allow for early detection of eutrophication, which may initiate timely management interventions to avert seagrass loss.

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“…Seagrass meadows have higher production relative to unvegetated sediments (Barró n et al 2004;Eyre et al 2011;Hume et al 2011) in part because they have greater primary producer and heterotrophic consumer biomass (Hemminga and Duarte 2000). In addition, changes in ecosystem structure through the development of a seagrass canopy can increase efficiency of light absorption on an ecosystem scale relative to unvegetated sites (Binzer et al 2006;Ralph et al 2007). Finally, seagrass communities affect flow conditions and create a depositional environment (Gacia and Duarte 2001;Hansen and Reidenbach 2012), increase sediment organic content (Fourqurean et al 2012;McGlathery et al 2012;Greiner et al 2013), and change sediment oxygenation through release of oxygen from the roots and rhizomes (Frederiksen and Glud 2006).…”

mentioning

confidence: 99%

Ecosystem metabolism along a colonization gradient of eelgrass (Zostera marina) measured by eddy correlation

Rheuban

Berg

McGlathery

2014

Limnology & Oceanography

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The Virginia coastal bays experienced local extinction of eelgrass (Zostera marina) during the early 1930s, and restoration beginning in 2001 has generated an ecosystem state change from bare to vegetated sediments. Oxygen fluxes were measured seasonally using the eddy correlation technique at three sites representing different stages of seagrass colonization: unvegetated (bare), 5 yr, and 11 yr since seeding. Derived seasonal ecosystem respiration (R) and gross primary production (GPP) increased up to 10-fold and 25-fold, respectively, with meadow age. Although hourly oxygen (O 2 ) fluxes were highly correlated with light at the vegetated sites, no identifiable trends with light were observed at the bare site. The light compensation point where O 2 production and respiration are in balance increased from 46 mmol photons m 22 s 21 to 257 mmol photons m 22 s 21 and 63 mmol photons m 22 s 21 to 472 mmol photons m 22 s 21 at the 5 yr and 11 yr seagrass sites, respectively, with increasing seasonal temperatures from 12.3uC to 27.9uC and 9.3uC to 30.5uC, respectively. This suggests that more light, and thus more O 2 production, is required to offset increasing respiration with both temperature and meadow age. Photosynthesisirradiance curves generated from hourly O 2 fluxes throughout the seasons were used to estimate annual net ecosystem metabolism (NEM). Annual NEM rates at the bare, 5 yr, and 11 yr sites were 27.6, 8.6, and 27.0 mol O 2 m 22 yr 21 , respectively. Although the system went through a period of net autotrophy during early stages of colonization, the ecosystem state change from unvegetated sediments to dense seagrass meadows changed the magnitude of both GPP and R, but not the overall metabolic balance of the system.

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Impact of light limitation on seagrasses

Cited by 397 publications

References 121 publications

Effects of multiple disturbances in seagrass meadows: shading decreases resilience to grazing

Effects of multiple disturbances in seagrass meadows: shading decreases resilience to grazing

Combined nutrient and macroalgae loads lead to response in seagrass indicator properties

Ecosystem metabolism along a colonization gradient of eelgrass (Zostera marina) measured by eddy correlation

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