Experimental evidence that herbivory increases shoot density and productivity in a subtropical turtlegrass ( Thalassia testudinum  ) meadow

Valentine, John F.; Heck, Kenneth L.; Busby, Jill; Webb, D. P.

doi:10.1007/s004420050300

Cited by 113 publications

(95 citation statements)

References 74 publications

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“…Recovery of the trimmed patches was in agreement with findings that the significant portion of total plant biomass is below ground, which acts as a nutrient store and rapidly produces new shoots in response to trimming (Sohn & Policansky 1977, Valentine et al 1997. The enhanced ramet density in trimmed patches is typical of plants that experience infrequent but severe damage (Grime 1979).…”

Section: Discussionsupporting

confidence: 85%

“…Like Halodule wrightii, Z. novazelandica grows by basal elongation of the meristemic region (Kuo & McComb 1989), and ramets react to cropping by producing new ramets (Mitchell 1987). Grazing of Thalassia testudinum by sea urchins has been shown to have no negative effect on seagrass biomass due to a compensatory increase in the number of short shoots during the growing season (Valentine et al 1997). I n conclusion, the rate of p a t c h expansion a n d contraction is regulated b y physical factors on t h e intertidal platforms of Kaikoura.…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

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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“…Valdez and Villalobos, 1978;Bauer, 1980;Weil et al, 1984;Benedetti-Cecchi and Cinelli, 1995;Turon et al, 1995;Falcon et al, 1996). Sea urchins are known to control the abundance and distribution of algae and can therefore have a profound influence on the structure of benthic communities (Andrew, 1989;Vadas, 1990;Vadas and Elner, 1992;Valentine et al, 1997). At Madeira Island (Portugal, north-east Atlantic), sea urchin ecology has not previously been studied in detail, although it is referred to by Augier (1985), Wirtz (1995Wirtz ( , 1998 and Bianchi et al (1998).…”

Section: Introductionmentioning

confidence: 99%

Algal cover and sea urchin spatial distribution at Madeira Island (NE Atlantic)

et al. 2001

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SUMMARY: This study describes sea urchin spatial distribution in relation to environmental factors, and the relationship between Diadema antillarum density and algal abundance. Twenty-three transects around Madeira Island were surveyed by scuba divers, and sea urchin density and algal cover were determined in situ. Sampling sites along these transects were characterised in terms of distance from the tide line, water depth, substratum type, bottom declivity and water turbulence. Diadema antillarum was the dominant sea urchin species. Paracentrotus lividus and Arbacia lixula occurred at shallower depths (2-6 m), contrasting with the distribution of Sphaerechinus granularis, which occurs among D. antillarum (4-20 m). Surveys found two alternative types of communities on rocky shores: 1) a community with high algal cover and low numbers of sea urchins, along the north and south-west coasts and; 2) a community with little algal cover and high densities of sea urchins, along the south-east coast. Macroalgal cover and D. antillarum densities were inversely correlated (adjusted R 2 =75.6%; n = 429; p<0.05). The results showed that water turbulence was the most important factor limiting the distribution of D. antillarum on rocky substrates. We propose a multiple non-linear regression model (using backward stepwise analysis) to explain D. antillarum abundance on the rocky shores: D. antillarum/m 2 (√√)= 0.121 -0.209 distance from shore (in m) (√√) + 2.052 water depth (in m) (√√) -1.778 water turbulence level (√√) -0.007 water turbulence level 4 (√√); where √√ indicates data are square-root transformed (adjusted R 2 = 60.99%; n = 454; p<0.05).

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“…High rates of herbivory have been found to confer resilience by causing a high turnover of plant tissue, resulting in reduced buildup of epiphytic material (Christianen et al, 2012). This herbivory also results in plants increasing their aboveground net production (Valentine et al, 1997;Duarte and Chiscano, 1999). Processes that influence the rate of this herbivory therefore have the potential to result in cascading feedbacks to the wider seagrass meadow .…”

Section: Introductionmentioning

confidence: 99%

Habitat Configuration Alters Herbivory across the Tropical Seascape

et al. 2017

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There exists increasing evidence that top-down ecological processes, such as herbivory are key in controlling marine ecosystems and their community structure. Herbivory has the potential to be altered by numerous environmental and ecological factors that operate at a variety of temporal and spatial scales, one such spatial factor is the influence of the marine landscape. We know little about how ecological processes, such as herbivory change throughout the marine landscape and how the effects of these processes cascade. This is because most landscape scale studies observe species richness and abundance patterns. In terrestrial systems the landscape is well documented to influence ecological processes, but empirical evidence of this is limited in marine systems. In tropical seagrass meadows direct herbivory by parrotfish can be readily observed due to the clear hemispherical bite marks they leave on the seagrass. As with herbivory in other systems, this leaf consumption is thought to assist with leaf turnover, positively influencing leaf growth. Changes in its rate and extent are therefore likely to influence the characteristics of the plant. The faunal communities of seagrass meadows alter with respect to changes in the landscape, particularly with respect to connectivity to adjacent habitats. It might therefore be expected that a key ecological process, such as herbivory will change with respect to habitat configuration and have cascading impacts upon the status of the seagrass. In the present study we examined indirect evidence of parrotfish grazing throughout the marine landscape and assessed this relative to plant condition. Seagrasses in locations of close proximity to mangroves were found to have double the amount of parrotfish grazing than sites away from mangroves. Evidence of herbivory was also found to be strongly and significantly negatively correlated to the abundance of plant attached epicover. The decreased epicover in the presence of elevated herbivory suggests increased leaf turnover. These results indicate that seagrass may have higher levels of ecosystem resilience in the presence of mangroves. Our research highlights how ecological processes can change throughout the marine landscape with cascade impacts on the resilience of the system.

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Experimental evidence that herbivory increases shoot density and productivity in a subtropical turtlegrass ( Thalassia testudinum ) meadow

Cited by 113 publications

References 74 publications

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

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

Algal cover and sea urchin spatial distribution at Madeira Island (NE Atlantic)

Habitat Configuration Alters Herbivory across the Tropical Seascape

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