| 研究実績の概要 |
This study demonstrates the indirect effects of ocean acidification on benthic macroherbivores and the habitat. This year's main objective was to identify benthic macroherbivore species that are vulnerable to ocean acidification. Carbonate chemistry conditions in the study sites at Shikine-jima have continued to be monitored (including their pH, temperature, salinity, and total alkalinity), with our two sites representing present-day and future end-of-the-century conditions. From initial surveys, the most vulnerable taxa appears to be sea urchins, which despite being able to survive under ocean acidification conditions, are demonstrating clear changes in their physiology and ecological role. The two most abundant sea urchins (Diadema setosum and Echinometra sp.) were collected from the sites, their biological traits were measured, and aquarium experiments were run. These included measurements of their size, gonadal content, respiration and feeding rates. Overall, these indicated that the sea urchins were negatively affected by ocean acidification resulting in fewer, smaller individuals. Additionally, we further measured the physical structure of their tests and spines (in order to assess their calcification / dissolution responses) using microCT and FTIR, as well as their gut microbiota (16S metabarcoding) in order to assess their health. It is likely that these negative impacts on the benthic macroherbivores will have indirect effects on the habitat of the community (this will be the focus in the subsequent years).
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| 今後の研究の推進方策 |
In the future, while continuing to identify other vulnerable benthic macroherbivores (and measure their biological traits), we will focus on assessing the effects of ocean acidification on algal habitats. These will involve assessments of their photophysiology (using a diving PAM), community productivity (in-situ chamber measurements), food quality (CN ratios/fatty-acid). Following this, we will investigate the indirect role of ocean acidification on algal habitats via effects on the benthic macroherbivores. This will involve assessments using feeding trials (to assess food preference), food-web analyses, as well as recruitment experiments to assess community structure dynamics (with and without grazer-exclusion cages). Taken together, this should help our research demonstrate how ocean acidification will negatively impact the ability of benthic macroherbivores to control algal habitats and how this functional loss will play an important role in causing algal habitats to shift into undesirable degraded states.
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