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Consumer depletion alters seagrass resistance to an invasive macroalga

Caronni, Sarah and Calabretti, Chiara and Delaria, Maria Anna and Bernardi, Giuseppe and Navone, Augusto and Occhipinti Ambrogi, Anna and Panzalis, Pieraugusto and Ceccherelli, Giulia (2015) Consumer depletion alters seagrass resistance to an invasive macroalga. PLoS One, Vol. 10 (2), p. 18. ISSN 1932-6203. Article.

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DOI: 10.1371/journal.pone.0115858

Abstract

Few field studies have investigated how changes at one trophic level can affect the invasibility of other trophic levels. We examined the hypothesis that the spread of an introduced alga in disturbed seagrass beds with degraded canopies depends on the depletion of large consumers. We mimicked the degradation of seagrass canopies by clipping shoot density and reducing leaf length, simulating natural and anthropogenic stressors such as fish overgrazing and water quality. Caulerpa racemosa was transplanted into each plot and large consumers were excluded from half of them using cages. Potential cage artifacts were assessed by measuring irradiance, scouring by leaf movement, water flow, and sedimentation. Algal invasion of the seagrass bed differed based on the size of consumers. The alga had higher cover and size under the cages, where the seagrass was characterized by reduced shoot density and canopy height. Furthermore, canopy height had a significant effect depending on canopy density. The alteration of seagrass canopies increased the spread of C. racemosa only when large consumers were absent. Our results suggest that protecting declining habitats and/or restoring fish populations will limit the expansion of C. racemosa. Because MPAs also enhance the abundance and size of fish consuming seagrass they can indirectly promote algal invasion. The effects of MPAs on invasive species are context dependent and require balancing opposing forces, such as the conservation of seagrass canopy structure and the protection of fish grazing the seagrass.

Item Type:Article
ID Code:10923
Status:Published
Refereed:Yes
Uncontrolled Keywords:Caulerpa racemosa, seagrass, algal invasion, MPAs
Subjects:Area 05 - Scienze biologiche > BIO/07 Ecologia
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Scienze della Natura e del Territorio
Publisher:Public Library of Science
ISSN:1932-6203
Copyright Holders:© 2015 Caronni et al.
Deposited On:05 Jun 2015 18:07

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