Gap Dynamics in a Seagrass Landscape

Bell, Susan S.; Robbins, Bradley D.; Jensen, Susan L.

doi:10.1007/s100219900097

Cited by 81 publications

(56 citation statements)

References 49 publications

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“…Most studies have tended to focus on large-scale processes (Bell et al, 1999) in seagrass beds, rather than on ubiquitous but small-scale dynamics. Studies describing seagrass patch dynamics (Almela et al, 2008;Brun et al, 2003b;Campbell and Paling, 2003;Di Carlo and Kenworthy, 2008;Duarte and Sand-Jensen, 1990) focused on plant physiology rather than on the impact of environmental characteristics including local sediment biogeochemistry.…”

Section: Introductionmentioning

confidence: 99%

Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii

et al. 2014

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As a result of anthropogenic disturbances and natural stressors, seagrass beds are often patchy and heterogeneous. The effects of high loads of nutrients and organic matter in patch development and expansion in heterogeneous seagrass beds have, however, poorly been studied. We experimentally assessed the in situ effects of sediment quality on seagrass (Zostera noltii) patch dynamics by studying patch (0.35 m diameter) development and expansion for 4 sediment treatments: control, nutrient addition (NPK), organic matter addition (OM) and a combination (NPK+OM).OM addition strongly increased porewater sulfide concentrations whereas NPK increased porewater ammonium, nitrate and phosphate concentrations. As high nitrate concentrations suppressed sulfide production in NPK+OM, this treatment was biogeochemically comparable to NPK. Sulfide and ammonium concentrations differed within treatments, but over a 77 days period, seagrass patch survival and expansion were impaired by all additions compared to the control treatment.Expansion decreased at porewater ammonium concentrations >2000 mol L -1 .Mother patch biomass was not affected by high porewater ammonium concentrations as a result of its detoxification by higher seagrass densities. Sulfide 2 concentrations >1000 mol L -1 were toxic to both patch expansion and mother patch. We conclude that patch survival and expansion are constrained at high loads of nutrients or organic matter as a result of porewater ammonium or sulfide toxicity.

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Section: Introductionmentioning

confidence: 99%

Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii

et al. 2014

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“…Thalassia hemprichii grew into experimental 0.25 m 2 gaps over 2 yr, but Enhalus acoriodes was predicted to take 10 yr to refill these gaps (Rollon et al 1999). Halodule wrightii beds can fill in small gaps in < 6 mo (Bell et al 1999). Our results showed that Zostera noltii can fill in gaps of 0.13 m 2 in 1 mo.…”

Section: Discussionmentioning

confidence: 57%

Resilience of Zostera noltii to burial or erosion disturbances

Han¹,

Bouma²,

Brun³

et al. 2012

Mar. Ecol. Prog. Ser.

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Dynamic environments like seagrass habitats are characterised by continuous local erosion and burial processes, which may induce seagrass decline if disturbances become too intense or frequent. We aim to quantify for Zostera noltii the resilience of both the edge of a meadow and individual propagules to local-scale burial and erosion events. In a set of mesocosm and in situ manipulation experiments, we varied the frequency (sudden vs. continuous rate) and intensity (different levels; −6 cm erosion to 6 cm burial) of sediment dynamics. Our results showed that the intensity of the disturbance event (−6 up to 6 cm) was negatively correlated with plant survival. Burial frequency also had a significant effect on plant survival, with sudden events having a stronger negative impact than continuous ones. Both experiments, on individual propagules and attached rhizomes at meadow edges, demonstrated a rapid acclimatization of seagrass plants to sediment dynamics within certain levels of disturbance (−6 up to 6 cm). After erosion or burial, all surviving plants in the field and mesocosm experiments were able to relocate their rhizomes to the preferential depth (from 0.3 to 0.8 cm), which was the depth at which the rhizomes of undisturbed plants were most frequently found in the field. In situ manipulation experiments showed that at the edge of the meadow, Z. noltii invaded experimentally created hollows more easily than hills. Overall, our results demonstrate that Z. noltii meadows can rapidly recover by clonal growth after modest sediment disturbance, thereby contributing to the current understanding of seagrass recovery mechanisms following disturbances (e.g. sediment dynamics).

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“…Studies of soft-sediment environments are increasingly addressing spatial variation in the structure and dynamics of benthic communities and populations (e.g., Thrush et al 1997;Bell et al 1999;Kneib 2000) and show that significant spatial variation can occur at several scales. However, only a few studies have considered spatial patterns in detail over benthoscape scales more than several square kilometers in deep-water environments (e.g., Thrush et al 1998Thrush et al , 2001Zajac et al 2000;Kostylev et al 2001;Brown et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Responses of infaunal populations to benthoscape structure and the potentialimportance of transition zones

Zajac

Lewis

Poppe

et al. 2003

Limnology & Oceanography

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Relationships between population abundance and seafloor landscape, or benthoscape, structure were examined for 16 infaunal taxa in eastern Long Island Sound. Based on analyses of a side-scan sonar mosaic, the 19.4-km 2 study area was comprised of six distinct large-scale (Ͼ km 2 ) benthoscape elements, with varying levels of mesoscale (km 2 -m 2 ) and small-scale (Ͻ m 2 ) physical and biological habitat heterogeneity. Transition zones among elements varied from ϳ50 to 200 m in width, comprised ϳ32% of the benthoscape, and added to overall benthoscape heterogeneity. Population abundances of nine taxa varied significantly among the large-scale elements. Most species were found at high abundances only in one benthoscape element, but three had several foci of elevated abundances. Analyses of population responses to habitat heterogeneity at different spatial scales indicated that abundances of eight taxa varied significantly among spatial scales, but the significant scales were mixed among these species. Relatively large residual variations suggest significant amounts of mesoscale spatial variation were unaccounted for, varying from ϳ1 km 2 to several m 2 . Responses to transition zones were mixed as well. Abundances of nine taxa varied significantly among transition zones and interiors of benthoscape elements, most with elevated abundances in transition zones. Our results show that infaunal populations exhibit complex and spatially varying patterns of abundance in relation to benthoscape structure and suggest that mesoscale variation may be particularly critical in this regard. Also, transition zones among benthoscape features add considerably to this variation and may be ecological important areas in seafloor environments.The spatial patterns of benthic communities in relation to seafloor characteristics have been studied by marine ecolo-1 Corresponding author (rzajac@newhaven.edu). AcknowledgmentsWe would like to thank a number of people who provided immeasurable help in the field and laboratory. These include Tom

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Gap Dynamics in a Seagrass Landscape

Cited by 81 publications

References 49 publications

Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii

Toxic effects of increased sediment nutrient and organic matter loading on the seagrass Zostera noltii

Resilience of Zostera noltii to burial or erosion disturbances

Responses of infaunal populations to benthoscape structure and the potentialimportance of transition zones

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