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Marine Ecology Progress Series

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MEPS 511:83-91 (2014)  -  DOI:

Herbivory in a subtropical seagrass ecosystem: separating the functional role of different grazers

Ameer Ebrahim1, Andrew D. Olds1,3,*, Paul S. Maxwell1, Kylie A. Pitt1, Dana D. Burfeind1,2, Rod M. Connolly1

1Australian Rivers Institute - Coast and Estuaries, School of Environment, Griffith University, Gold Coast, Queensland 4222, Australia
2School of Biological Sciences, University of Queensland, St Lucia, Queensland 4072, Australia
3Present address: School of Science and Engineering, University of the Sunshine Coast, Maroochydore, Queensland 4558, Australia
*Corresponding author:

ABSTRACT: Seagrass meadows provide many important ecosystem services, but they are threatened by human activities and are in decline globally. In particular, eutrophication arising from human activities promotes algal growth, which negatively affects seagrass. Herbivores consume algae and can, therefore, reduce eutrophication effects, but they may also consume seagrass. Little is known, however, about grazer-epiphyte-seagrass interactions in subtropical seagrass in the Indo-Pacific. We used a 5 wk exclusion experiment to quantify the influence of different grazers in seagrass (dominated by Zostera muelleri) in Moreton Bay, eastern Australia. Our results show that herbivory does indeed affect seagrass-epiphyte dynamics in this region and that different grazers can exert different effects in seagrass ecosystems. In particular, exclusion of small mesograzers (i.e. amphipods and juvenile shrimp) caused epiphyte biomass to increase by up to 233%. Exclusion of medium mesograzers (i.e. small fish and prawns) resulted in increases of up to 10% in seagrass cover, 53% in shoot height and 29% in shoot density. Large mesograzers (i.e. adult fish) and macrograzers (i.e. turtles and dugong) did not appear to play a role in the study system. These results demonstrate that mesograzers can be important in controlling epiphytic algae in subtropical Indo-Pacific seagrass, and show that different mesograzers can affect seagrass-epiphyte dynamics in different ways. It is critical that the functional effects of different herbivores be considered when implementing programs for seagrass conservation and restoration.

KEY WORDS: Seagrass · Epiphytes · Herbivory · Mesograzers · Fish · Invertebrates · Moreton Bay · Australia

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Cite this article as: Ebrahim A, Olds AD, Maxwell PS, Pitt KA, Burfeind DD, Connolly RM (2014) Herbivory in a subtropical seagrass ecosystem: separating the functional role of different grazers. Mar Ecol Prog Ser 511:83-91.

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