Dissertation
Refuge in the deep? Assessing the potential of mesophotic coral ecosystems to act as refugia for shallow coral reef fishes in the Hawaiian Islands
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/111014
Abstract
Coral reefs are increasingly under threat, necessitating an emphasis to identify coral reefs with reduced susceptibilities to local and/or global anthropogenic impacts. Mesophotic coral reefs (MCEs; >30m) are proposed as potential refugia and/or propagule sources, yet little information is known about deep reefs’ abilities to harbor, replenish, or conserve shallow species. In this dissertation, I examine the plausibility of MCEs to act as refugia for shallow reef fishes in the Hawaiian Islands. Chapter One explores reef fish community structure and habitat composition along a 3-50m gradient in West Hawaii. Reef fish communities change gradually with depth, with >78% of species observed at mesophotic depths (>30m) found at shallow depths. Changes in community structure are linked closely with feeding behavior, with shallow reefs dominated by herbivores, while mesophotic reefs are dominated by invertivore and planktivore trophic assemblages. Changes in fish assemblages are tied to indirect effects of depth and available coral habitat, as deeper reefs contain more patchily-distributed habitat. Chapter Two examines mechanisms underlying herbivorous fish distributions using a suite of observational and experimental field and laboratory techniques. Herbivorous fishes are not limited by food resources at MCE depths, as MCE algae had similar nutritional content, species assemblages, and appears to be highly palatable from algal choice experiments. Instead, changes with depth are likely the result of top-down, non-consumptive predation effects and behavioral choices. Chapter Three undertakes a critical analysis of the deep refugia hypothesis for coral reef fishes across the Main Hawaiian Islands. Upper MCEs (30-60m) may act as refugia for shallow reef fishes, as we found they are more thermally stable and >70% of reef fishes encountered were shallow species. Conversely, MCEs contain reduced densities of reef fishes and communities are comprised almost solely of invertivore and planktivore trophic groups. The near-absence of herbivorous fishes below 30m indicate MCEs will have a limited capacity to re-seed shallow reefs with species of ecological or economic importance. Overall, MCEs may act as refugia for biodiversity conservation but their ability to restock shallow reef fish communities will result in fundamentally different community compositions that shift towards smaller-bodied and less economically/ecologically valuable species.
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Details
- Title
- Refuge in the deep? Assessing the potential of mesophotic coral ecosystems to act as refugia for shallow coral reef fishes in the Hawaiian Islands
- Creators
- Corinne Nicole Kane
- Contributors
- Brian N Tissot (Advisor)Cheryl B Schultz (Committee Member)Stephen M Henderson (Committee Member)Mark A Hixon (Committee Member)Randall K Kosaki (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 152
- Identifiers
- 99900581624701842
- Language
- English
- Resource Type
- Dissertation