Spatial Distribution of Gastropod Community and it’s Association with Seagrass Habitat in Manokwari Coastal West Papua

Abstract

Seagrass vegetation in Manokwari coastal waters was classified as mixed vegetation and gastropods featured as one major animal in the seagrass ecosystem. The purpose of this study were (1) to know and analyze the influence of physicalchemical water and substrat texture on the species competition, frequency, percent cover and density of seagrass, and (2) to determine and assess the effect of seagrass habitat complexity on the density, diversity, eveness and distribution of gastropods species. From four observation sites (Rendani, Wosi, Briosi, and Padarni), eight seagrass species were identified, i.e: Cymodocea rotundata, C. serrulata, Halodule pinifolia H. uninervis, Halophila ovalis, Syringodium isoetifolium, and Thalassia hemprichii, while Enhalus acoroides were founded at outside of quadrant at Rendani, Wosi and Padarni. Frequency, cover and density of individuals of each seagrass species showed a high value for C. rotundata, T. hemprichii in Rendani , Briosi, Padarni and H. uninervis, H. pinifolia in Wosi. A total of 229 gastropods species were observed, with Padarni as site with the highest gastropod abundance. Briosi featured the highest diversity of gastropod species, whilst Padarni the lowest, and gastropod community were generally in stable condition. Several species of gastropod showed clustered distribution, but most of species showed uniform distribution. The analysis result of Correspondent Analysis (CA) showed correspondence between Nerita chameleon and Clithon oualaniensis with H. ovalis in Rendani and with C.rotundata and C.serrulata in Briosi. In Wosi, showing Hastula acumen corresponds to H. uninervis and H. pinifolia, while Nassarius (Plicarcularia) globosus dominant in Padarni corresponds to H. pinifolia on sandy mud substrates, which are influenced by high temperature and high organic materials.

Ekosistem lamun yang ada di perairan pesisir pada daerah yang dangkal merupakan ekosistem yang kompleks dan memiliki fungsi yang penting bagi berbagai organisme yang berasosiasi. Salah satu organisme yang berasosiasi dan dominan ditemukan dalam ekosistem lamun adalah gastropoda, yang sangat berperan dalam rantai makanan. Saat ini keberadaan habitat lamun dan gastropoda di Perairan Pesisir Manokwari terancam karena degradasi lingkungan dan dimanfaatkan oleh masyarakat setempat. Hal tersebut yang melatarbelakangi penelitian ini, yang dilaksanakan pada empat lokasi yakni Pesisir Rendani, Pesisir Wosi, Pesisir Briosi dan Pesisir Padarni. Adapun tujuan penelitian ini adalah: (1) Mengetahui dan menganalisis pengaruh parameter fisika-kimia perairan dan tekstur substrat terhadap komposisi spesies, frekuensi, persen tutupan dan kerapatan lamun, (2) Mengetahui dan mengkaji pengaruh kompleksitas habitat padang lamun terhadap kepadatan, keanekaragaman dan keseragaman serta distribusi spesies gastopoda.