| dc.description.abstract | Abstrak: Perairan Pulau Harapan, Kepulauan Seribu, menghadapi tekanan
antropogenik yang berpotensi meningkatkan konsentrasi unsur hara dan memicu
eutrofikasi. Penelitian ini bertujuan menganalisis kandungan nitrat dan fosfat,
mengidentifikasi jenis dan kelimpahan fitoplankton, serta mengkaji hubungan
keduanya. Pengambilan data dilakukan pada Februari, Mei, Agustus, dan
November 2025 di empat Stasiun. Nitrat dan fosfat dianalisis secara
spektrofotometri, sedangkan fitoplankton diidentifikasi dan dihitung
menggunakan Sedgwick–Rafter Counting Chamber. Konsentrasi nitrat berkisar
0,018–0,070 mg/L dan fosfat 0,010–0,023 mg/L. Nitrat melampaui baku mutu
selama seluruh periode pengamatan, sedangkan fosfat mulai Mei. Fitoplankton
didominasi Bacillariophyceae, dengan 7–18 taksa dan kelimpahan 1,0–9,8 × 106
sel/L. Fosfat menunjukkan hubungan lebih kuat terhadap kelimpahan fitoplankton
(R² = 0,1555) dibandingkan nitrat (R² = 0,0079). Rasio Redfield menunjukkan nitrat
sebagai unsur hara pembatas.
Abstract: Pulau Harapan, Kepulauan Seribu, is subject to anthropogenic pressures that
may increase nutrient concentrations. This study aimed to determine nitrate and
phosphate concentrations, identify phytoplankton composition and abundance, and
their relationships. Data were collected in February, May, August, and November
2025 at four stations. Nitrate and phosphate were analyzed spectrophotometrically,
while phytoplankton were enumerated using a Sedgwick–Rafter Counting
Chamber. Nitrate ranged from 0.018–0.070 mg/L and phosphate from 0.010–0.023
mg/L. Nitrate exceeded the seawater standard throughout observations, whereas
phosphate exceeded the standard from May onward. Phytoplankton were
dominated by Bacillariophyceae, with 7–18 taxa and abundances of 1.0–9.8 × 106
cells/L. PCA explained 51.68% of variance. Regression showed a stronger
relationship between phosphate and abundance (R² = 0.1555) than nitrate (R² =
0.0079). The N:P ratio remained below 16, indicating nitrate limitation. | |
