Asymmetric patterns of recovery in two habitat forming seagrass species following simulated overgrazing by urchins

• Main Authors: Burnell, Owen., Connell, Sean., Irving, Andrew D., Russell, Bayden.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Netherlands : Elsevier 2013
• Subjects: LIBRARY OF CONGRESS NEEDED; Pure basic research; 960802 Coastal and Estuarine Flora; Fauna and Biodiversity; 960808 Marine Flora; 969999 Environment not elsewhere classified; 050102 Ecosystem Function; 050104 Landscape Ecology; 050211 Wildlife and Habitat Management; Amphibolis antarctica > Habitat loss > Herbivory > Meristem > Phase shift > Posidonia sinuosa; Journal Article. Refereed; Scholarly Journal; Antarc*; Antarctica
• Online Access: http://hdl.cqu.edu.au/10018/1014063

The persistence of seagrass meadows reflects variation in factors that influence their productivity and consumption. Sea urchins (Amblypneustes pallidus) can over-graze seagrass (Amphibolis antarctica) to create sparse meadows in South Australia, but this effect is not observed in adjacent Posidonia sinuosa meadows despite greater densities of inhabiting urchins. To test the effect of urchin grazing on seagrass biomass, we elevated the density of urchins in meadows of A. antarctica and P. sinuosa and quantified seagrass decline. Urchins removed similar amounts of biomass from both seagrass species, but the loss of leaf meristems was 11-times greater in A. antarctica than in P. sinuosa. In a second experiment to assess the recovery of seagrass, we simulated urchin grazing by clipping seagrass to mimic impacts measured in the first experiment, as well as completely removing all above ground biomass in one treatment. Following simulated grazing, P. sinuosa showed a rapid trajectory toward recovery, while A. antarctica meadows continued to decline relative to control treatments. While both A. antarctica and P. sinuosa were susceptible to heavy grazing loss, consumption of the exposed meristems of A. antarctica appears to reduce its capacity to recover, which may increase its vulnerability to long-term habitat phase-shifts and associated cascading ecosystem changes.