Efektivitas Pemberian Pupuk Organik Cair Terhadap Laju Pertumbuhan Spirulina platensis Sebagai Bioremediasi Logam Berat Tembaga (Cu)

Abstract

Pencemaran perairan merupakan masalah lingkungan besar di dunia, termasuk di Indonesia, logam berat seperti tembaga (Cu) dari limbah industri, pertanian, dan domestik menyebabkan toksisitas tinggi, bioakumulasi, dan gangguan ekosistem akuatik serta kesehatan manusia. Metode remediasi fisika-kimia seperti filtrasi dan adsorpsi efektif tetapi mahal dan berisiko sekunder, sehingga bioremediasi menggunakan mikroalga seperti Spirulina platensis menjadi alternatif ramah lingkungan karena kemampuan biosorpsi dan bioakumulasi logam. Namun demikian, media kultur konvensional seperti walne mahal, sehingga pupuk organik cair (POC) dari fermentasi limbah ikan patin diusulkan sebagai pengganti. Hal ini disebabkan POC lebih ekonomis dan kaya nutrisi organik (N, P, K) untuk mendukung pertumbuhan mikroalga dan bioremediasi Cu sambil memanfaatkan limbah untuk ekonomi sirkular. Tujuan penelitian ini adalah menganalisis efek pemberian pupuk organik cair terhadap laju pertumbuhan Spirulina platensis sebagai bioremediasi logam berat tembaga (Cu) melalui kajian pengaruh konsentrasi POC terhadap parameter pertumbuhan (laju pertumbuhan spesifik, kepadatan sel, kandungan klorofil-a, indeks ekologis, warna media), efisiensi bioremediasi (penurunan konsentrasi Cu, bioaccumulation factor), persentase sel lisis, dan kualitas air kultur (suhu, salinitas, pH, DO, TAN, nitrat, ortofosfat). Penelitian dilaksanakan pada Juni hingga Agustus 2025 di Laboratorium Lingkungan Akuakultur IPB, menggunakan rancangan acak lengkap dengan lima perlakuan, yaitu P0(-) walne tanpa Cu, P0(+) walne + Cu 5 mg/L, P1 POC 5 ml/L + Cu 5 mg/L, P2 POC 7,5 ml/L + Cu 5 mg/L, P3 POC 10 ml/L + Cu 5 mg/L dengan tiga ulangan. POC dibuat dari fermentasi limbah ikan patin selama 14 hari dengan MOL kulit nanas, kultur S. platensis dimulai dengan inokulum 10-20% volume media 1 L, aerasi kontinu, dan pencahayaan LED kontinu 36 watt. Sterilisasi dilakukan dengan autoklaf dan klorin, pengamatan mencakup kepadatan sel menggunakan haemocytometer, laju pertumbuhan spesifik harian, indeks ekologis Shannon-Wiener, klorofil-a dengan spektrofotometer metode Lichtenthaler, warna media skala visual, konsentrasi Cu dengan AAS, sel lisis mikroskop, dan kualitas air dengan alat multiparameter; data dianalisis ANOVA dan uji Duncan (p<0.05). Kinerja pertumbuhan S. platensis menunjukkan perbedaan nyata antar perlakuan, dengan konsentrasi 7,5 ml/L (P2) memberikan laju pertumbuhan spesifik tertinggi 31,78±2,55%/hari, kepadatan sel puncak 13,75×104 sel/mL pada hari ke-7, dan klorofil-a 31,60±7,06 µg/mL; indeks keanekaragaman (H') 0, keseragaman (E) 0, dominansi (D) 1 menunjukkan kultur monospesies. Efisiensi bioremediasi Cu tertinggi pada P2 sebesar 80,64% dengan bioaccumulation factor 8477 dan penurunan Cu hingga 0,968 mg/L. Persentase sel lisis terendah pada P2 (7,8%) dibanding P0(+) (3,.8%), sementara kualitas air stabil dengan suhu 25-28°C, salinitas 17-20 g L-1, pH 7,8-8,6, DO 4,5-7,5 mg L-1, TAN turun hingga 0,11-0,37 mg L-1, nitrat turun hingga 0,11-0,54 mg L-1, dan ortofosfat fluktuatif 0,29-1,55 dengan penurunan tajam pada hari ke-7 akibat asimilasi alga. Mikroalga seperti S. platensis efektif sebagai agen bioremediasi karena kemampuan mengikat logam melalui eksopolisakarida dan antioksidan, dengan POC pada konsentrasi optimal 7,5 ml/L meningkatkan pertumbuhan melalui nutrisi mudah diasimilasi, mengurangi stres toksik Cu, dan mempertahankan kultur monospesies melalui sterilitas ketat. Kandungan klorofil-a dan warna media mencerminkan respons fisiologis terhadap nutrisi dan Cu, di mana konsentrasi tinggi menyebabkan eutrofikasi mini dan penurunan performa, sementara parameter air seperti pH dan DO mendukung fotosintesis optimal; pengamatan sel lisis rendah menunjukkan toleransi tinggi, dan efisiensi bioremediasi meningkat dengan biomassa yang lebih besar. Pemberian pupuk organik cair efektif meningkatkan laju pertumbuhan S. platensis dan kinerja bioremediasi logam berat tembaga (Cu). Konsentrasi POC 7,5 ml/L memberikan hasil terbaik pada semua parameter, mendukung pendekatan berkelanjutan dan ekonomi sirkular melalui pemanfaatan limbah ikan.

Water pollution is a major environmental problem worldwide, including in Indonesia. Heavy metals such as copper (Cu) from industrial, agricultural, and domestic waste cause high toxicity, bioaccumulation, and disruption of aquatic ecosystems and human health. Physical-chemical remediation methods such as filtration and adsorption are effective but expensive and pose secondary risks, making bioremediation using microalgae such as Spirulina platensis an environmentally friendly alternative due to its biosorption and bioaccumulation capabilities. However, conventional culture media such as walnut shells are expensive, so liquid organic fertilizer (POC) from fermented catfish waste is proposed as a substitute. This is because POC is more economical and rich in organic nutrients (N, P, K) to support microalgae growth and Cu bioremediation while utilizing waste for a circular economy. The objective of this study was to analyze the effect of liquid organic fertilizer application on the growth rate of S. platensis as a bioremediation of copper (Cu) heavy metals through a study of the effect of POC concentration on growth parameters (specific growth rate, cell density, chlorophyll-a content, ecological index, medium color), bioremediation efficiency (Cu concentration reduction, bioaccumulation factor), percentage of lysed cells, and culture water quality (temperature, salinity, pH, DO, TAN, nitrate, orthophosphate). The study was conducted from June to August 2025 at the IPB Aquaculture Environment Laboratory, using a completely randomized design with five treatments, namely P0(-) walne without Cu, P0(+) walne + Cu 5 mg/L, P1 POC 5 ml/L + Cu 5 mg/L, P2 POC 7.5 ml/L + Cu 5 mg/L, P3 POC 10 ml/L + Cu 5 mg/L with three replicates. POC was produced from the fermentation of catfish waste for 14 days with pineapple skin MOL, S. platensis culture was started with an inoculum of 10-20% of 1 L media volume, continuous aeration, and continuous 36-watt LED lighting. Sterilization was performed using an autoclave and chlorine. Observations included cell density using a hemocytometer, daily specific growth rate, Shannon Wiener ecological index, chlorophyll-a using the Lichtenthaler spectrophotometer method, visual scale media color, Cu concentration using AAS, lysed cells under a microscope, and water quality using a multiparameter device. data were analyzed using ANOVA and Duncan's test (p<0.05). The growth performance of S. platensis showed significant differences between treatments, with a concentration of 7.5 ml/L (P2) giving the highest specific growth rate of 31.78±2.55%/day, peak cell density of 13.75×104 cells/mL on day 7, and chlorophyll-a of 31.60±7.06 µg/mL; diversity index (H') 0, evenness (E) 0, dominance (D) 1 indicated a monospecific culture. The highest Cu bioremediation efficiency was observed in P2 at 80.64% with a bioaccumulation factor of 8477 and a reduction in Cu to 0.968 mg/L. The lowest percentage of cell lysis was at P2 (7.8%) compared to P0(+) (3.8%), while water quality was stable at a temperature of 25-28°C, salinity of 17-20 g L-1, pH of 7.8-8.6, DO of 4.5-7.5 mg L-1, TAN decreased to 0.11-0.37 mg L-1, nitrate decreased to 0.11-0.54 mg L-1, and orthophosphate fluctuated between 0.29-1.55 with a sharp decrease on day 7 due to algal assimilation. Microalgae such as S. platensis are effective as bioremediation agents due to their ability to bind metals through exopolysaccharides and antioxidants, with POC at an optimal concentration of 7.5 ml/L enhancing growth through easily assimilated nutrients, reducing Cu toxic stress, and maintaining monospecific cultures through strict sterility. Chlorophyll-a content and medium color reflect physiological responses to nutrients and Cu, where high concentrations cause mini-eutrophication and reduced performance, while water parameters such as pH and DO support optimal photosynthesis; low cell lysis observations indicate high tolerance, and bioremediation efficiency increases with larger biomass. The application of liquid organic fertilizer effectively increases the growth rate of S. platensis and the bioremediation performance of copper (Cu) heavy metals. A POC concentration of 7.5 ml/L yields the best results across all parameters, supporting a sustainable and circular economy approach through the utilization of fish waste.