Hubungan Produktivitas Primer Fitoplankton dengan Distribusi Nutrien di Waduk Sermo, Kulon Progo

ZULFA SYAFIYA, Ludmilla Fitri Untari, S.Si., M.Sc.

2025 | Skripsi | BIOLOGI

Waduk Sermo sebagai satu di antara area rekreasi dan sumber air di Kulon Progo terletak sangat dekat pemukiman warga. Aktivitas manusia serta pengalihan area di sekitar Waduk Sermo menjadi pertanian berpotensi meningkatkan laju erosi, sedimentasi, dan masukan-masukan nutrien ke dalam waduk. Lahan pertanian tersebar di daerah tangkapan air Waduk Sermo membentuk aliran limpasan permukaan dikala musim hujan yang berpotensi membawa nutrien berlebih masuk ke badan air. Akumulasi nutrien yang terbawa limpasan permukaan dari pupuk berlebih pertanian ke dalam perairan, akan direspon oleh komunitas fitoplankton. Penelitian dilakukan pada bulan dasarian III (10 hari terakhir) bulan Oktober di Waduk Sermo didapat hasil bahwa nilai produktivitas primer berkisar 137-1035 gC/m3/tahun, mengindikasikan status trofik eutrofik dengan hubungan positif antara produktivitas primer fitoplankton dan distribusi nutrien. Konsentrasi nutrien lebih tinggi di dekat inlet akibat limpasan dari aktivitas antropogenik dan berkurang menuju outlet akibat proses pengenceran, sedimentasi, atau asimilasi. Distribusi nutrien secara vertikal ditemukan bahwa nitrat dan fosfat lebih banyak terkonsentrasi di lapisan hipolimnion karena dekomposisi organik. Distribusi nutrien secara spasial memiliki keterkaitan signifikan dengan kelimpahan fitoplankton, terutama alga koloni yang merespons kadar nutrien dan parameter fisikokimia. Komunitas fitoplankton di Waduk Sermo cenderung melimpah, dengan indeks dominansi yang bergantung pada kondisi fisikokimia,  ketersediaan nutrien, dan variasi spasial.

Sermo Reservoir as one of the recreational areas and water sources in Kulon Progo is located very close to residential areas. Human activities and the conversion of the area around the reservoir to agriculture land have the potential to increase the rate of erosion, sedimentation, and nutrient inputs into the reservoir. Agricultural land scattered in the Sermo Reservoir catchment area forms surface runoff during the rainy season that has the potential to carry excess nutrients into the water body. The accumulation of nutrients carried by surface runoff from excess agricultural fertilizers into the waters will be responded to by the phytoplankton community. Research conducted in the third dasarian month (last 10 days) of October in Sermo Reservoir found that primary productivity values ranged from 137-1035 gC/m3/year, indicating eutrophic trophic status with a positive relationship between phytoplankton primary productivity and nutrient distribution. Nutrient concentrations were higher near the inlet due to higher anthropogenic activities and decreased towards the outlet due to dilution, sedimentation or assimilation processes. Vertical nutrient distribution found that nitrate and phosphate were more concentrated in the hypolimnion layer due to organic decomposition. The spatial distribution of nutrients was significantly related to phytoplankton abundance, especially colonial algae that respond to nutrient levels and physicochemical parameters. The phytoplankton community in Sermo Reservoir tends to be abundant, with dominance patterns varying depending on physicochemical conditions, nutrient availability, and spatial variation.

Kata Kunci : algal bloom, eutrofikasi, distribusi nutrien, produktivitas primer