ANALISIS HUBUNGAN KELIMPAHAN FITOPLANKTON DENGAN KANDUNGAN NITRAT DAN FOSFAT DI PERAIRAN MOROSARI, DEMAK Relationship Analysis of Phytoplankton Abundance to Nitrate and Phosphate in the Morosari Waters, Demak - Nasution, Afiah; Widyorini, Niniek; Purwanti, Frida (Fakultas Perikanan dan Ilmu Kelautan, Universitas Diponegoro, 2019)
ABSTRAK Morosari terletak di kecamatan Sayung, Demak dimana terdapat pemukiman penduduk, kegiatan pariwisata dan perikanan. Aktivitas ini dapat memengaruhi keberadaan organisme di perairan, khususnya fitoplankton. Penelitian ini bertujuan untuk mengetahui kelimpahan fitoplankton, kandungan nitrat dan fosfat, serta hubungan antara kelimpahan fitoplankton dengan kandungan nitrat dan fosfat di perairan Morosari. Penelitian ini mengacu pada penelitian deskriptif korelasional dengan metode pengambilan sampel acak sistematik dan analisis data dengan analisis regresi dan korelasi Pearson. Penelitian ini berlangsung selama enam bulan dengan pengambilan sampel dilakukan pada bulan Mei 2018 yang berlangsung selama tiga minggu berturut-turut. Data yang diukur meliputi parameter fisika-kimia (temperatur air, kecerahan, kedalaman, arus, pH, salinitas, DO, bahan organik, nitrat dan fosfat) serta kelimpahan fitoplankton, indeks keanekaragaman, keseragaman, dan dominansi. Hasil penelitian menunjukkan bahwa kelimpahan fitoplankton tertinggi yaitu dari kelas Bacillariophyceae sebesar 4.362 ind/l, terendah dari kelas Dinophyceae sebesar 163 ind/l, dengan jenis tertinggi yaitu Chaetoceros sp sebesar 1.022 ind/l, dan jenis terendah yaitu Micractinium sp sebesar 7 ind/l. Kandungan nitrat di perairan Morosari berkisar antara 3,99 – 7,09 mg/l, dengan rata-rata keseluruhan sebesar 5,11 mg/l (Eutrofik). Kandungan fosfat berkisar antara 0,01 – 1,13 mg/l, dengan rata-rata keseluruhan sebesar 0,18 mg/l (Eutrofik). Hubungan kelimpahan fitoplankton dengan kandungan nitrat tergolong kategori lemah namun pasti (0,26), sedangkan dengan kandungan fosfat tergolong kuat (0,70) pada taraf kepercayaan 95%. ABSTRACT Morosari located in the sub-district of Sayung, Demak where residential areas, tourism industries and fisheries activities were existed. These activities could affecting the presence of organisms in the waters, especially phytoplankton. This research aimed to determine the abundance of phytoplankton, the content value of nitrate and phosphate, and the relationship of phytoplankton abundance to the content of nitrate and phosphate in the Morosari waters. This research refers to correlational descriptive research with the systematic random sampling method, and the analysis of relationship carried out by regression analysis. This research has been conducted for six months with sampling started in May 2018 for three weeks consecutively. The data measured included physical-chemical parameters (temperature of water, transparency, depth, current, pH, salinity, DO, organic matter, nitrate and phosphate) as well as abundance, diversity, uniformity, and dominance index. The results showed that the highest phytoplankton abundance was from the Bacillariophyceae class (4.362 ind/l), the lowest was Dinophyceae class (163 ind/l), with the highest species was Chaetoceros sp (1.022 ind/l), and the lowest species was Micractinium sp (7 ind/l). The nitrate content in the Morosari waters ranges from 3.99 - 7.09 mg/l, with an overall average of 5.11 mg/l (Eutrophic). Phosphate content ranged from 0.01 - 1.13 mg/l, with an overall average of 0.18 mg/l (Eutrophic). The abundance of phytoplankton with nitrate content was classified as weak but definite(0.26), while phosphate content was strong (0.70) at 95% confidence level.