Community Structure of Chitons (Polyplacophora) in Open and Sheltered Intertidal Habitats on The Boulder Beach of Magarizaki, Tomioka Peninsula, Amakusa, Japan
DOI:
https://doi.org/10.35800/4cnp2d58Keywords:
Chiton; exposed and sheltered intertidal habitats; Japan; Magarizaki boulder beach; community structureAbstract
The intertidal zone of the boulder Magarizaki beach in Amakusa, Japan, is a dynamic coastal ecosystem that serves as a critical habitat for chitons (Polyplacophora) as grazers and ecological indicators. This study aims to identify chiton species and determine their community structure in exposed and sheltered intertidal habitats. The study was conducted in August–September 2025 using quadrat sampling and purposive sampling techniques at two locations. Identification was based on the literature Marine Mollusks in Japan and the WoRMS database. Analyses included species density, relative density, the Shannon–Wiener index (H’), Pielou index (J’), Simpson’s dominance (D), and Bray–Curtis similarity. Five chiton species were found: Acanthochitona defilippii, Acanthochitona achates, Acanthopleura japonica, Ischnochiton comptus, and Lepidozona coreanica. Open habitats contained four species (A. defilippii, A. achates, I. comptus, L. coreanica), while sheltered habitats contained three species (A. defilippii, A. japonica, L. coreanica). The open habitat showed H' = 0.762 (low), J' = 0.549 (moderate), and D = 0.507 (moderate), while the sheltered habitat showed H' = 0.159 (low), J' = 0.144 (low), and D = 0.940 (high). The similarity between the two communities was low, at 0.375 (37.5%). Overall, although diversity in both habitats was low, the open habitat had a better community balance compared to the sheltered habitat, which was dominated by certain species.
Keywords: Chiton, exposed and sheltered intertidal habitats, Japan, Magarizaki boulder beach, community structure
Abstrak
Zona intertidal pantai berbatu boulder Magarizaki, Amakusa, Jepang merupakan ekosistem pesisir dinamis yang menjadi habitat penting bagi chiton (Polyplacophora) sebagai grazer dan indikator ekologi. Penelitian ini bertujuan mengidentifikasi spesies chiton dan menentukan struktur komunitasnya pada habitat intertidal terbuka (exposed) dan terlindung (sheltered). Penelitian dilakukan pada Agustus-September 2025 dengan metode quadrat sampling dan teknik purposive sampling di dua lokasi. Identifikasi mengacu pada literatur Marine Mollusks in Japan dan basis data WoRMS. Analisis meliputi kepadatan spesies, kepadatan relatif, indeks Shannon–Wiener (H'), Pielou (J'), dominansi Simpson (D), dan similaritas Bray–Curtis. Ditemukan lima spesies chiton: Acanthochitona defilippii, Acanthochitona achates, Acanthopleura japonica, Ischnochiton comptus, dan Lepidozona coreanica. Habitat terbuka memiliki empat spesies (A. defilippii, A. achates, I. comptus, L. coreanica), sedangkan habitat terlindung memiliki tiga spesies (A. defilippii, A. japonica, L. coreanica). Habitat terbuka menunjukkan H' = 0,762 (rendah), J' = 0,549 (sedang), dan D = 0,507 (sedang), sedangkan habitat terlindung H' = 0,159 (rendah), J' = 0,144 (rendah), dan D = 0,940 (tinggi). Similaritas kedua komunitas rendah, yaitu 0,375 (37,5%). Secara keseluruhan, meski keanekaragaman di kedua habitat rendah, habitat terbuka memiliki keseimbangan komunitas lebih baik dibandingkan habitat terlindung yang didominasi spesies tertentu.
Kata kunci: Chiton, habitat intertidal terbuka dan terlindung, Jepang, pantai boulder Magarizaki, struktur komunitas
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