Keanekaragaman Serangga Air di Danau Lau Kawar Akibat Erupsi Gunung Sinabung Kecamatan Simpang Empat, Kabupaten Karo

Abstract

Lau Kawar Lake was affected by the eruption of Mount Sinabung that causing changes in water conditions and aquatic biota life, one of which was water insects. Water insects have the ability to respond changes in water conditions so they can be used as a bioindicator of a water. The aims of this study were to record diversity, diversity index (H’), evenness index (E) of water insects and to correlate the diversity index with the water abiotic factors. This study was conducted at July 2019. The purposive random sampling method were use to determined the research region based on activities around lake water body. Ecology parameter included relative density, frequency, diversity index, evenness index. Abiotic parameters measured included water temperature, substrate type, pH, dissolved oxygen (DO), oxygen saturation, BOD5, nitrate (NO3), phosphate (PO4) and organic substrate content. The Pearson correlation index were conducting using SPSS ver. 22.00 software. Before the eruption, 32 genera of water insects were known from 8 ordo and 13 families. Two genera were discovered from this research from Ophiogomphus and Crocothemis genera. Diversity index before the eruption measured ranging from 0.49-0.84 while after the eruption ranging from 0.55-0.92.The correlation analysis found that before the eruption, the phosphate, nitrate and organic content were very strong correlated with diversity index while after eruption the found that dissolved oxygen and oxygen saturation were very strong correlated.

Danau Lau Kawar yang terdampak erupsi Gunung Sinabung menyebabkan perubahan kondisi perairan serta kehidupan biota air seperti serangga air. Serangga air dapat dijadikan sebagai bioindikator perairan karena kemampuannya merespon kondisi perairan. Penelitian yang telah dilaksanakan pada bulan Juli 2019 bertujuan untuk mengetahui keanekaragaman, nilai indeks keanekaragaman (H’) dan keseragaman (E) serangga air serta menganalisis hubungan indeks keanekaragaman dengan faktor fisik-kimia perairan di Danau Lau Kawar.Lokasi penelitian ditentukan menggunakan metode purposive random sampling berdasarkan aktifitas disekitar danau. Analisis data meliputi kepadatan, kerapatan relatif, frekuensi kehadiran, indeks keanekaragaman dan keseragaman. Parameter fisik-kimia perairan yang diukur meliputi temperatur air, tipe substrat, pH, oksigen terlarut(DO), kejenuhan oksigen, BOD5, kandungan nitrat (NO3), fosfat (PO4) dan kadar organik substrat. Penelitian ini mendapatkan 2 genus baru serangga air setelah erupsi gunung yakni Ophiogomphus dan Crocothemis. Nilai indeks keanekaragaman setelah erupsi berkisar 0,55-0,92. Hasil uji korelasi terhadap indeks keanekaragaman sebelum erupsi didapatkan kandungan fosfat, nitrat dan organik substrat berkorelasi sangat kuat, sedangkan setelah erupsi didapatkan oksigen terlarut dan kejenuhan oksigen berkorelasi sangat kuat.