The role of current velocity in structuring eelgrass (Zostera marina L.) meadows

Fonseca, Mark S.; Zieman, Joseph C.; Thayer, Gordon W.; Fisher, John S.

doi:10.1016/0272-7714(83)90123-3

Cited by 249 publications

(154 citation statements)

References 9 publications

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“…Bed edges erode, leading to increased sediment suspension, and current flow may be altered (Walker et al 1989, Fonseca 1996. Given that current patterns and velocities have the potential to shape seagrass beds (Fonseca et al 1983), continual scarring may further degrade and restructure beds, leading to fragmentation of once continuous meadows (see Walker et al 1989). Will the faunal effects observed in our study scale-up linearly, exponentially, or not at all?…”

Section: Discussionmentioning

confidence: 93%

Effects of propeller scarring on macrofaunal use of the seagrass Thalassia testudinum

Uhrin¹,

Holmquist²

2003

Mar. Ecol. Prog. Ser.

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Propeller scarring within seagrass beds is common in shallow coastal waters. Scarring has the potential to fragment seagrass beds, resulting in habitat loss, decreased productivity, and the possibility for further erosion and degradation. We conducted a study in Thalassia testudinum beds in Puerto Rico to determine whether seagrass macrofauna are affected by this disturbance. Four sampling zones (propeller scar, seagrass-scar interface, homogeneous seagrass located 5 m from the scar, and homogeneous seagrass located 10 m from the scar) were compared among 10 replicate seagrass beds. Scarring modified faunal assemblages at the scale of the propeller scar; there was significantly lower total macrofaunal abundance and fewer species in scars. When individual taxa were considered, shrimp and mollusc abundances were lower in scars compared to the other sampling zones. Resident fish abundance was not significantly different among zones. Dominant shrimp species in scars differed from seagrass zones. Crabs and molluscs responded negatively to scarring as indicated by significantly lower densities of these 2 taxa up to 5 m from scars. The extent to which these results 'scale up' remains unknown and future studies should focus on larger, more intensely scarred areas.

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Section: Discussionmentioning

confidence: 93%

Effects of propeller scarring on macrofaunal use of the seagrass Thalassia testudinum

Uhrin¹,

Holmquist²

2003

Mar. Ecol. Prog. Ser.

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“…But sediment motion alone 257 does not govern the presence of plant life. A plant may be able to survive an area with weak 258 sediment motion, but a rapidly scouring bed will cause plants to uproot and will preclude the 259 growth of aquatic vegetation that depends on the substrate for stability (Fonseca et al, 1983). 260 Second, plants have an inherent lodging velocity that defines the flow speed at which the plant 261 material fails.…”

Section: Introduction 18mentioning

confidence: 99%

Effects of Added Vegetation on Sand Bar Stability and Stream Hydrodynamics

2010

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Abstract:Vegetation was added to a fully-developed sandy point bar in the meander of a 5 constructed stream. Significant changes in the flow structure and bed topography were observed. 6As expected, the addition of vegetative resistance decreased the depth-averaged streamwise 7 velocity over the bar and increased it in the open region. In addition, the secondary circulation 8 increased in strength, but became confined to the deepest section of the channel. Over the point 9 bar, the secondary flow was entirely outwards, i.e. towards the outer bank. The changes in flow 10 led to changes in bar shape. Although the region of the bar closest to the inner bank accumulated 11 sediment, erosion of the bar and the removal of plants by scouring was observed at the interface 12 between the planted bar and the open channel. 13

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“…Individual seagrass plants seem able to withstand considerable stress, but the stability of meadows can still be greatly affected by environmental changes (McComb et al 1981). In temperate ecosystems, erosional cycles determined by wind direction, wave and tidal height lead to spatial and temporal changes in seagrass distribution (Fonseca et al 1983, Fonseca & Kenworthy 1987.…”

Section: Introductionmentioning

confidence: 99%

Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

Ramage¹,

Schiel²

1999

Mar. Ecol. Prog. Ser.

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We examined the patch dynamics of the intertidal seagrass Zostera novazelandica on 2 reef platforms in order to understand the processes governing the establishment, maintenance and mortality of patches. The size distribution of patches at 3 tidal heights (low, mid and high shore) was assessed. Eighty patches, ranglng in initial size from 0.1 to 2.4 m2 surface area, were tagged and video image analysis was used bi-monthly for 14 mo to calculate rates of expansion and contraction of these patches. Permanently marked 150 m2 areas of reef were monitored monthly to record patch recruitment and mortality. Initially, 75% of patches were <0.5 m2 All patches decreased in size during winter, probably due to increased wave action, and expanded during spring and summer. The proportional expansion and contraction of patches was independent of initial patch size. At the end of the study the size distribution of patches was similar to the initial distribution. Patch mortality was restricted to those <0.4 m2, of which 60% disappeared during the study. Larger patches suffered partial mortality through fragmentation. No large patches were formed through the amalgamation of smaller patches. Seedlings recruited into small sediment pockets in tidepools during spring, but few survived through summer because of removal by wave action. Experimental perturbation of patches resulted in increased erosion followed by decreased growth rates and, in many small patches, mortality. Removing only seagrass blades, however, resulted in increased production of new shoots relative to controls. Overall, seagrass patches are susceptible to disturbance, successful rclcruitment by seedlings may be rare or at least episodic, and populations are probably long-Lived and depend on slow vegetative growth for maintenance and expansion.

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The role of current velocity in structuring eelgrass (Zostera marina L.) meadows

Cited by 249 publications

References 9 publications

Effects of propeller scarring on macrofaunal use of the seagrass Thalassia testudinum

Effects of propeller scarring on macrofaunal use of the seagrass Thalassia testudinum

Effects of Added Vegetation on Sand Bar Stability and Stream Hydrodynamics

Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

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