Gastropod Assemblage and Biofilm Abundance on Rocky Shores of Southern Antique, Panay, Philippines

Authors

• Mia Jane D. Geneblaza, Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, Miagao, Iloilo 5023, PhilippinesFollow
• Karen A. Villarta-Lane, Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, Miagao, Iloilo 5023, PhilippinesFollow

Publication Date

12-1-2025

Abstract

The gastropod assemblage and biofilm abundance, measured as chlorophyll a levels, were examined at 3 rocky shore sites in southern Antique, Panay, Philippines, in February 2024 to address significant gaps in current knowledge and help better understand the ecological dynamics of rocky intertidal zones. A total of 14 families comprising 22 genera and 31 species were identified from the area. The family Littorinidae was the most speciesrich, comprising 9 species. Among these, the scabra periwinkle Littoraria scabra (Philippi 1846) was the most abundant, comprising on average 50.17% of the total abundance across sites. Other identified gastropod families included Muricidae (5 species), Neritidae (3), Calliostomatidae, and Collumbellidae (2 each), and the following families with 1 species each: Cerithiidae, Conidae, Cypraeidae, Fasciolariidae, Lottiidae, Pisaniidae, Planaxidae, and Pleurotomariidae. The sites showed moderate diversity (H′) and dominance (D), each with 1 dominant species, but low evenness (E), indicating community instability. Overall, gastropod density ranged from 13 to 33 ind. 0.25 m−² across sites. Mid-shore zones generally had the highest densities, with 85 ind. 0.25 m−² at Site 1 and 31 ind. 0.25 m−² at Site 3, except at Site 2, where the highest density was observed at the high shore (52.90 ind. 0.25 m−²). Using the cold methanol method, chlorophyll a concentration was revealed to differ between sites (p < 0.05). Results showed greater concentration on the lower shore (overall mean = 233.01 μg cm⁻²) than on the higher shore (overall mean = 18.12 μg cm⁻²). Pearson correlation analysis revealed a strong positive relationship (r = 0.97) between mean chlorophyll a concentration and gastropod grazer abundance across sites. However, within individual sites, there were varying negative correlation values (r = −0.31 to −0.79) found to be statistically insignificant at a p > 0.05 level of significance. Results suggest insufficient evidence to assert a definitive relationship between gastropod abundance and chlorophyll a concentration. Further studies need to be conducted over a longer period of time and include other ecological factors to validate the findings of this research.

Recommended Citation

Geneblaza, Mia Jane D. and Villarta-Lane, Karen A. (2025) "Gastropod Assemblage and Biofilm Abundance on Rocky Shores of Southern Antique, Panay, Philippines," The Philippine Agricultural Scientist: Vol. 108: No. 4, Article 9.
Available at: https://www.ukdr.uplb.edu.ph/pas/vol108/iss4/9