Piscine browsing increases from shallow reefs to upper mesophotic coral habitats of the Bolinao-Anda Reef Complex, northwestern Philippines

The consumption of macroalgae by browsing fishes is viewed as a key process in coral reef ecosystems. However, the majority of studies on piscine browsing have been conducted in shallow reefs, limiting our understanding of this ecological process in Mesophotic Coral Ecosystems (MCEs: >30m). This study used Sargassum assays and remote underwater videos to examine differences in the rates and agents of macroalgal browsing across four depth bands (0–10m, 11–20m, 31–40m, 41–50m) in the Bolinao-Anda Reef Complex (BARC), Philippines. Assays deployed over 4 days revealed differences in macroalgal biomass loss among depth bands, with 2-fold higher macroalgal loss at the deepest depth band (41–50m; 24.0 g 4 d⁻¹) compared to shallower (0–40m) depth bands (18.6–20.0 g 4 d⁻¹). Video observations from shorter-term (3h) assays revealed that Naso unicornis and N. lituratus, were responsible for ∼98 % of total bites on Sargassum assays across all depth bands. Bite rates for both species were consistently higher in the deepest (41–50m) depth band (N. unicornis: 23.1 bites 3 h⁻¹; N. lituratus: 84.9 bites 3 h⁻¹) compared to shallower (0–40m) depth bands (N. unicornis: 8.5–15.5 bites 3 h⁻¹; N. lituratus: 10.2–23.0 bites 3 h⁻¹). Further, browsing fishes were 38.5–61.4 % larger in the deeper (31–50m) compared to the shallower (0–20m) depth bands. Contrary to previous studies, results show that browsing increased with depth in the BARC and suggest that piscine herbivores may limit the accumulation of macroalgae biomass in upper MCEs in this reef system.

Marine Environmental Research

Marine Environmental Research

212

1879-0291

N/A

N/A

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