Presenter: Adrianna Hernandez (UCLA)
Description:
Turbinaria ornata is a rapidly-expanding macroalga considered an alternative stable state on coral reefs of Moorea, French Polynesia. T. ornata expansion may be accelerated by reduced herbivory and increased nutrient availability, two critical and well-established drivers of macroalgal dominance on tropical reefs. In French Polynesia, most studies report T. ornata has expanded its habitat by occupying hard substrate in shallow reef zones; however, recent observations at deeper depths suggest a recent vertical expansion. To investigate factors that limit depth distribution, we conducted a 3-factor fully-crossed transplant experiment using small T. ornata thalli (~5cm). We experimentally manipulated depth (Turbinaria zone (TZ) <1m and below TZ (BTZ) at 4m), nutrient supply (+/- slow release fertilizer) and herbivory (+/- cages), and measured growth as change in weight and height. Small T. ornata gained an average of 0.05 ∓ 0.04 SE g over 7 days when protected from herbivores and lost 0.21 ∓ 0.07 SE g over 7 days when exposed to herbivores (ANOVA, p = 0.002 for herbivory). We found no significant effects of depth, nutrients, or their interactions. Small T. ornata grew taller in the TZ with an average change in height of 0.58 ∓ 0.08 SE cm over 7 days while the BTZ thalli only gained an average of 0.34 ∓ 0.04 SE cm over 7 days (PERMANOVA, p = 0.0079 for zone). Height did not vary with nutrients or herbivory. Overall, we did not find either nutrients or herbivory limited the depth distribution of T. ornat, despite the well-established importance of these factors in controlling macroalgal distributions. Thus, we speculate that vertical expansion may continue on reefs of Moorea, but that expansion may only occur at the border of existing patches, which, as an alternative stable state, may provide highly localized protection from herbivores.
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Full list of Authors
- Nicholas Durgadeen (University of the Virgin Islands)
- Julianna Limon (University of California Santa Cruz)
- Caitlin Fong (National Center for Ecological Analysis and Synthesis)
- Peggy Fong (University of California Los Angeles)
- Paul Barber (University of California Los Angeles)
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VERTICAL EXPANSION OF TURBINARIA ORNATA, AN ALTERNATIVE STABLE STATE USUALLY RESTRICTED TO SHALLOW ZONES OF CORAL REEFS, IS NOT LIMITED BY NUTRIENTS OR HERBIVORY ON JUVENILE THALLI
Category
Scientific Session > ME - Marine Ecology and Biodiversity > ME11 Impacts of ecological interactions on marine ecosystem dynamics and biodiversity: New insights from theory, models, and field measurements
Description
Presentation Preference: Poster
Supporting Program: None
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