Keanekaragaman Plankton dan Hubungannya dengan Kualitas Perairan Muara Sungai Asahan

Abstract

This study deals with The diversity of Plankton and Its relations with the Quality of Sungai Asahan Mouth’s Waters, the research has been conducted on August 2009. Sample was taken from three stations with three depth namely 0 m (surface), depth of end line in light penetration, depth under end line of light penetration, and three repetitions. In defining the points of taking sample is by adopting purposive random sampling. Sample of plankton was taken there using a net plankton tool. For identification of plankton sample was completed at Ecology Laboratory, Biology Department, Faculty of Mathematics and Natural Sciences, North Sumatra University Medan. The outcome there were obtained 12 plankton class comprising 5 pytho-plankton Class and 7 Zooplankton Class. The highest abundantly rate, relative dense and the emerging frequency found on station 3 there are Coscinodiscus genus, Coscinodiscaceae Class is 13591,83 individu/l, 14,59% and 100%, The totality highest abundantly rate on Stasion 3 of 93142,85 individu/l. Where as the totality lowest abundantly rate was noted on station 1 of 19102.041 individu/l. The highest diversities index rate was found on station 3 noted 2.92 whereas the lowest diversities rate noted on station 1 of 2.48. The highest equality index rate found on station 1 was noted 0.48 while the lowest equality rate was found on station 3 with 0.78. The highest similarities index rate was found on station 1 noted 74.285% whereas the lowest similarities index rate was found on station 1 and 3 with 59.793%. The variance analysis inter stations showed its diversity index rate and abundantly plankton between Station 1 and 2, Station 1 and 3, Station 2 and 3 there is no significantly difference indicated this community is resemblance. Still, the variance analysis between its depth showed its diversity index rate and abundantly plankton inter depth 0 m (surface) with the depth of end line light penetration, for the depth under end line of light penetration there is no significant difference, whereas between the depth 0 m (surface) with the depth under end line of light penetration is significantly different. The analysis correlation of Pearson on physical and chemical properties of waters over the abundantly plankton index rate showed that temperature, light penetration, light intensity, TDS, pH, salinity, DO, and phosphate correlated positively, whereas TSS, BOD5, COD and nitrate correlated negatively. The quality of water based its diversities index rate is classified into a moderate polluted.

Penelitian yang berjudul Keanekaragaman Plankton dan Hubungannya dengan Kualitas Perairan Muara Sungai Asahan telah dilakukan pada bulan Agustus 2009. Pengambilan sampel dilakukan di tiga stasiun penelitian, tiga kedalaman yaitu kedalaman 0 m (permukaan), kedalaman batas penetrasi cahaya, kedalaman di bawah batas penetrasi cahaya, dan tiga kali ulangan. Penentuan titik pengambilan sampel dilakukan dengan menggunakan metode Purporsive Random Sampling. Sampel plankton diambil dengan menggunakan alat plankton net. Identifikasi sampel plankton dilakukan di Laboratorium Ekologi, Departemen Biologi Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Sumatera Utara Medan. Hasil penelitian didapat sebanyak 12 kelas plankton yang terdiri dari 5 kelas fitoplankton dan 7 kelas zooplankton. Nilai kelimpahan, kepadatan relatif dan frekuensi kehadiran tertinggi terdapat pada stasiun 3 yaitu dari genus Coscinodiscus, kelas Coscinodiscaceae sebesar 13591,83 individu/l, 14,59 % dan 100 %. Total kelimpahan tertinggi terdapat pada Stasiun 3 sebesar 93142,85 individu/l. Sedangkan total nilai kelimpahan terendah terdapat pada stasiun 1 sebesar 19102,041 individu/l. Nilai indeks keanekaragaman tertinggi terdapat pada stasiun 3 sebesar 2,92 sedangkan nilai keanekaragaman terendah terdapat pada stasiun 1 sebesar 2,48 Nilai indeks keseragaman tertinggi terdapat pada stasiun 1 sebesar 0,48 sedangkan nilai keseragaman terendah terdapat pada stasiun 3 sebesar 0,78. Nilai indeks similaritas tertinggi terdapat pada stasiun 1 dengan 2 sebesar 74,285% sedangkan nilai indeks similariras terendah terdapat pada stasiun 1 dengan 3 sebesar 59,793%. Analisis varian antar stasiun menunjukkan nilai indeks keanekaragaman dan kelimpahan plankton antara stasiun 1 dengan 2, Stasiun 1 dengan 3, Stasiun 2 dengan 3 tidak ada perbedaan yang nyata, artinya komunitas ini mirip. Sedangkan analisis varian antar kedalaman menunjukkan nilai indeks keanekaragaman dan kelimpahan plankton antara kedalaman 0 m (permukaan) dengan kedalaman batas penetrasi cahaya, dan dengan kedalaman di bawah batas penetrasi cahaya tidak ada perbedaan yang nyata, sedangkan antara kedalaman 0 m (permukaan) dengan kedalaman di bawah batas penetrasi cahaya adalah beda nyata. Analisis korelasi Pearson sifat fisika-kimia perairan terhadap nilai indeks kelimpahan plankton menunjukkan bahwa suhu, penetasi cahaya, intensitas cahaya, TDS, pH, salinitas, DO, dan fosfat berkorelasi positif, sedangkan TSS, BOD5, COD dan nitrat berkorelasi negatif. Kualitas air berdasarkan nilai indeks keanekaragaman masuk kategori tercemar sedang.