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DIVERSITY AND HABITAT OF AMERICAN SĀMOA’S MESOPHOTIC CORAL ECOSYSTEMS: IMPLICATIONS TO THE DEEP REFUGE HYPOTHESIS
File under embargo until 2022-01-29
|Title:||DIVERSITY AND HABITAT OF AMERICAN SĀMOA’S MESOPHOTIC CORAL ECOSYSTEMS: IMPLICATIONS TO THE DEEP REFUGE HYPOTHESIS|
|Contributors:||Toonen, Robert J. (advisor)|
Marine Biology (department)
show 3 moremarine protected areas
new species records
|Publisher:||University of Hawai'i at Manoa|
|Abstract:||Over a century of study in American Sāmoa has built a foundation of coral reef ecology within the region. However, this work has been restricted to shallow coral reefs (SCRs; < 30 m) until recently, where a few studies have started describing American Sāmoa’s mesophotic coral ecosystems (MCEs). MCEs are defined as coral reef communities with zooxanthellate corals and associated biotic assemblages between 30–150 m depth. Mapping efforts within the territory have documented habitat characteristics for SCRs, as well as MCEs. I estimate that American Sāmoa has 451.5 km2 of marine habitat between the shoreline and 150 m depth while mesophotic depths represent 357.5 km2 or 79% of the total area. Approximately 56 km2 (12.4%) of the marine habitat above 150 m is under various levels of protection through a system of local, territorial, and federal marine protected areas. Of this, 21.7 km2 (6%) includes mesophotic depths. With only a handful of studies conducted and the majority of MCEs in American Sāmoa unexplored, there remain significant information gaps in understanding the basic biodiversity and ecology of the region. |
To address the gap in biodiversity knowledge, I present an annotated checklist of the stony corals (Scleractinia, Milleporidae, Stylasteridae, and Helioporidae) of American Sāmoa. A total of 377 valid species have been reported from American Sāmoa with 342 species considered either present (251) or possibly present (91). Of these 342 species, 66 have a recorded geographical range extension, and 90 have been reported from mesophotic depths (30–150 m). Additionally, four new species records (Acanthastrea subechinata, Favites paraflexuosus, Echinophyllia echinoporoides, Turbinaria irregularis) are presented. Coral species of concern include species listed under the U.S. Endangered Species Act (ESA) and the International Union for Conservation of Nature’s (IUCN) Red List of threatened species. Approximately 17.5% of the species present or possibly present are categorized as threatened by IUCN compared to 27% of the species globally. American Sāmoa has seven ESA-listed species, including Acropora globiceps, Acropora jacquelineae, Acropora retusa, Acropora speciosa, Fimbriaphyllia paradivisa, and Isopora crateriformis. There are two additional species possibly present, Pavona diffluens and Porites napopora.
The deep reef refuge hypothesis postulates that mesophotic coral ecosystems (MCEs) serve as a refuge for shallow coral reef (SCR) species during times of disturbance at shallow depths. This hypothesis requires that MCEs are protected as disturbance decreases with depth, and there is species overlap across depth that allow MCE species to provide propagules to SCRs. I analyzed stony coral communities across MCEs and SCRs to describe the community similarity and species overlap across communities. This research estimates that an additional 57 species are yet to be discovered in American Sāmoa and MCE habitats may be the largest source of those species. MCE communities were found to be distinct and a subset of SCR communities. Species overlap included 63 species with 12 deep exclusive species and 209 shallow exclusive species. Of the these, 19 species may have the greatest potential to serve as reseeding species. Two protected species include Acropora speciosa as an occasional deep specialist and Fimbriaphyllia paradivisa as a deep exclusive species. Based on distinct communities and a limited number of species overlap with the greatest potential to serve as a refuge, we propose utilizing a broader framework by developing a generalized refuge hypothesis to include SCRs species contribution to MCEs that can enable better conservation planning. Overall, the upper MCE in American Sāmoa does not serve as a reseeding refuge for the SCR community or any habitat with SCRs, but there are several species that may serve as a species-specific refuge.
|Rights:||All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.|
|Appears in Collections:||
Ph.D. - Marine Biology|
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