The effects of sea urchin grazing and drift algal blooms on a subtropical seagrass bed community

Maciá, Silvia

doi:10.1016/s0022-0981(99)00172-0

Cited by 45 publications

(32 citation statements)

References 25 publications

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“…Aboveground primary production increased in response to grazing by the sea urchin Lytechinus variegatus in the northeastern Gulf of Mexico and during the summer in the Florida Keys (Valentine et al 1997(Valentine et al , 2000. The former increase in productivity was a result of a significant increase in shoot density in response to grazing, which is opposite to both the trend in our study for a decrease in shoot density and the significant decrease in shoot density in T. testudinum grazed by L. variegatus during winter in Biscayne Bay, Florida (Maciá 2000). Parrotfish grazing on T. testudinum in the northern Florida Keys did not significantly decrease standing biomass, although parrotfish consumed substantial quantities of seagrass blades (Kirsch et al 2002).…”

Section: Effects Of Grazing On Structure and Productivity In Thalassicontrasting

confidence: 95%

Simulated green turtle grazing affects structure and productivity of seagrass pastures

Moran¹,

Bjorndal

2005

Mar. Ecol. Prog. Ser.

117

118

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The seagrass Thalassia testudinum evolved under much greater grazing pressure than exists today because overexploitation by humans caused the severe decline of green turtles Chelonia mydas, the major seagrass herbivore in the Caribbean. Understanding the effects of grazing on the structure and function of seagrass ecosystems is critical to evaluating how ecosystem processes have changed since the major herbivore was essentially removed from modern Caribbean seagrass systems. We evaluated effects of grazing on the structure and productivity of T. testudinum pastures by simulating green turtle grazing in 3 × 3 m plots for 16 mo in the central Bahamas and comparing these clipped plots to adjacent control (unclipped) plots. Simulated grazing affected the physical structure of T. testudinum plots, resulting in a system with reduced structural complexity. Simulated grazing resulted in compensatory growth in T. testudinum. Clipped plots maintained levels of growth comparable to unclipped plots over the 16 mo clipping trial, and specific mass growth was significantly elevated in clipped plots, even without simulating the nutrient return from green turtle feces and urine. The green turtle grazing pattern of re-cropping T. testudinum plots is sustainable for long periodsat least 16 mo. We estimated a range of carrying capacities of T. testudinum for green turtles of 1567 to 3748 kg turtle ha -1. Our study provides a foundation for reconstruction models and restoration plans for Caribbean seagrass ecosystems.

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Section: Effects Of Grazing On Structure and Productivity In Thalassicontrasting

confidence: 95%

Simulated green turtle grazing affects structure and productivity of seagrass pastures

Moran¹,

Bjorndal

2005

Mar. Ecol. Prog. Ser.

117

118

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“…In their study on the effects of Ulva rigida on Zostera noltii, Brun et al (2003) suggest different explanations for the lack of a significant effect on growth, including a net transfer of dissolved organic carbon from U. rigida to Z. noltii that would help to offset reduced photosynthesis, as well as a mobilization of non-structural carbohydrates in both the above-and belowground tissues of Z. noltii to meet carbon demands. The effects of macroalgae on other species of seagrasses similarly find variation in the intensity of response (Holmquist 1997, Maciá 2000, Cummins et al 2004, Irlandi et al 2004). It is not clear whether the inconsistencies in these results are due to the response of different seagrass species or to differences in the stress caused by different macroalgal species, or some environmental factor such as light, temperature, or water flow.…”

Section: Discussionmentioning

confidence: 94%

Multi-year study of the effects of Ulva sp. blooms on eelgrass Zostera marina

Olyarnik

Stachowicz²

2012

Mar. Ecol. Prog. Ser.

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Macroalgal blooms have contributed to declines in foundation species such as corals and seagrasses across the globe. Most studies of macroalgal bloom effects on seagrasses focus on the short-term effects, and have been conducted in locations that already begun the shift to macroalgal dominance, usually due to eutrophication. Our goal was to determine the degree to which the timing and magnitude of ephemeral, green macroalgal blooms (Ulva sp.) vary in Bodega Bay, California, USA, where there is little evidence for eutrophication, and how such blooms affect eelgrass Zostera marina. Over 38 mo, we conducted (1) an unmanipulated control treatment, and 3 manipulative treatments: (2) Ulva removal, (3) ambient Ulva, and (4) doubleambient Ulva ('2×'). We observed 4 blooms of varying magnitude and duration, ranging from < 0.5 to > 4 kg m −2. It was only during the largest bloom in 2006 (peak density 8 times that of the smallest observed bloom) that we saw a significant effect on eelgrass, resulting in declines in shoot density of > 50% that persisted for 4 to 6 mo. During this time, the 2× treatment reduced shoot biomass by up to 90%, an effect that persisted for up to 9 mo. Ulva did not affect rates of individual shoot growth, reproductive shoot density, epiphyte load, or sediment organic content at any time during the experiment, suggesting the effect occurs through shoot mortality and reduced shoot production. Interannual variation in the magnitude timing and duration of algal blooms is large and can dramatically alter the effects of blooms on eelgrass. These factors must be considered when interpreting the results of experimental algal additions.

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“…We collected samples by removing all of the algae from ten haphazardly placed 0.04 m 2 quadrats (Maciá 2000) laid on the substratum. This quadrat size provided a representative sample of the macroalgal community while minimizing variation and impacts on the benthic community.…”

Section: Study Sitementioning

confidence: 99%

Habitat-dependent growth in a Caribbean sea urchin Tripneustes ventricosus: the importance of food type

Maciá

Robinson

2008

Helgol Mar Res

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The sea urchin Tripneustes ventricosus is a common, yet relatively poorly known, grazer of seagrass beds and coral reefs throughout the Caribbean. We compared the size and abundance of urchins between adjacent seagrass and coral reef habitats (where macroalgae are the dominant primary producers). We also conducted a laboratory experiment comparing the growth rate of juvenile urchins fed a diet of either macroalgae or seagrass. Reef urchins had signiWcantly larger test diameter than those in the seagrass on some sampling dates. This size diVerence may be at least partially explained by diet, because laboratory-reared urchins fed macroalgae grew signiWcantly faster than those fed seagrass. The seagrass population, however, was stable over time, whereas the reef population exhibited strong Xuctuations in abundance. Overall, our study indicates that both the seagrass and coral reef habitats are capable of supporting healthy, reproductive populations of T. ventricosus. Each, however, appears to oVer a distinct advantage: faster growth on the reef and greater population stability in the seagrass.

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The effects of sea urchin grazing and drift algal blooms on a subtropical seagrass bed community

Cited by 45 publications

References 25 publications

Simulated green turtle grazing affects structure and productivity of seagrass pastures

Simulated green turtle grazing affects structure and productivity of seagrass pastures

Multi-year study of the effects of Ulva sp. blooms on eelgrass Zostera marina

Habitat-dependent growth in a Caribbean sea urchin Tripneustes ventricosus: the importance of food type

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