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KAJIAN PERTUMBUHAN TERUMBU KARANG JENIS PORITES BERDASARKAN ANTHROPOGENIC CAUSES DAN NATURAL CAUSES
DI KABUPATEN TAPANULI TENGAH
ABSTRAK
Penelitian pertumbuhan terumbu karang jenis porites di pulau Ungge kabupaten Tapanuli Tengah telah dilakukan berdasarkan rekaman lingkaran tahunan 1997-2012, dengan tujuan untuk mengetahui kandungan logam berat, struktur dan morfologi terumbu karang, pengaruh aktivitas manusia (Anthropogenic Causes) dan aktivitas alam (Natural Causes). Metode yang digunakan berupa pengujian dissolved oxygen (DO), Biochemical oxygen demand (BOD), kandungan logam berat pada air sungai dan air laut di lima stasiun dengan Titrimetri dan Inductively coupled plasma (ICP). Struktur dan morfologi terumbu karang dengan Rongent sinar-x, Thin slice, Atomic absorption spectrometer (AAS), difraksi (XRD), scanning electron mikroscope (SEM), dispersive X-Ray (EDX), Transmission electron microscopy (TEM), Thin slice, spektofotometer UV-Vis. Hasil analisa air sungai dan air laut diatas baku mutu sehingga telah tercemar logam berat Cu dan Fe. Hasil analisis mineralogi pada terumbu karang jenis porites menunjukkan CaCo3 aragonit 99,67 %, sistem kristal orthorhombik, didominasi O, C, Ca,
terdapat logam berat Cu, Fe. Pertumbuhan terumbu karang pada musim kemarau menunjukkan low density (LD) ditemukan mikrit 2% dan kalsit 8% dengan porositas 55% - 60%, tipe cavity, nilai absorbansi sebesar 0,441. Sebaliknya pertumbuhan pada musim hujan high density (HD) mikrit 8% dan kalsit 12% dengan porositas ± 35-43% , nilai absorbansi sebesar 0,549. Faktor aktivitas antropogenic causes tahun 2012 jumlah kenaikan penduduk tertinggi sebesar 7,7 % dari tahun sebelumnya, terjadi degradasi penurunan pertumbuhan terumbu karang sebesar 62,5 %. Tahun 2007 peningkatan jumlah industri tertinggi mencapai 81,5% menunjukkan pertumbuhan terumbu karang sebesar 7,5 mm dibawah pertumbuhan rata-rata 9,1 mm. Faktor aktivitas natural causes tahun 1998 saat iklim ekstrim menunjukkan suhu udara naik 0,5 0C dan suhu air laut 29,89 0C naik mencapai 0,90 C dari tahun sebelumnya, pertumbuhan terumbu karang mengalami penurunan 1 mm sebesar 10,5 % dari tahun sebelumnya. Tahun 2010 curah hujan tertinggi mencapai 455,4 mm naik 19,3 % teramati pertumbuhan terumbu karang 8,5 mm dibawah nilai rata-rata 9,1 mm. Tahun 1997, 1998, 2001 gempa bumi dengan magnitude < 3 skala Richter pertumbuhan terumbu karang diatas nilai rata-rata 9,1 mm. Tahun 2005 terjadi gempa bumi dengan frekuensi perulangan 33 dalam setahun magnitude tertinggi 6,8 skala Richer, teramati terjadi penurunan pertumbuhan terumbu karang 6,5 mm turun 23,1 % dari tahun sebelumnya. Hal ini menunjukkan telah terjadi degradasi pertumbuhan terumbu karang jenis porites di kabupaten Tapanuli Tengah disebabkan faktor anthropogenic causes dan natural causes .
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RESEACH OF THE PORITES CORAL REEF GROWTH BASED ON NATURAL CAUSES AND ANTHROPOGENIC CAUSES IN CENTRAL
TAPANULI SUB REGION
ABSTRACT
A research about the growth of coral reef, Porites type in Ungge Island, North Tapanuli regency based on the record of annual ring. The research purpose is to investigate the composition of hard metal, structure and morphology of coral reef, anthropogenic causes, and natural causes.The research method used the testing of dissolved oxygen (DO) and biochemical oxygen demand (BOD) to know composition of hard metals on the river and sea water at 5 stations by titrimetri and inductively coupled plasma (ICP). Structure and morphology of coral reef is observed by using X-Ray Rontgen, Thin Slice, atomic absorption spectrometer (AAS), X-Diffraction (XRD), scanning electron microscope (SEM), X-Ray dispersion (EDX), transmission electron microscopy (TEM), and UV-Vis. Analysis result of DO and BOD testing more than national standard showed that river and sea water had been contaminated by hard metals Cu and Fe. Analysis result of mineralogy on the coral reef pirotes type showed that there are hard metal Cu and Fe founded in CaCo3 aragonit 99,67% which its orthorhombic crystal system
is dominated by O, C, and Ca element. The growth of coral reef at dry season showed low density, its micrit is 2% and calsit is 8% with its porosity 55% - 60% belong to cavity type, and absorbance value 0.411. Meanwhile, the growth at rainy season at high density, its micrit is 8% and calsit is 12% with its porosity 35% - 43% and absrobance value 0.549. Factor of antropogenic causes in 2012 with the highest population increase about 7.7% from the previous year caused degradation in growth of coral reef about 62.5%. in 2007, development of the number of industrial business about 81.5 % caused the growth of coral reef being 7.5 mm, it is below of average growth of 9.1 mm. Factor of natural causes, in 1988 when extreame climate occured in which air temperature rose 0.5 and temperature of sea water was 29.89 , it rose 0.9 from previous year, the growth of coral reef decreased 1 mm, about 10.5% from previous year. In 2010 with the highest rainfall intensity reached 455.4 mm, increase 19.3%, the growth of coral reef was 8.5 mm, it is below of standard value 9.1 mm. Years 1997, 1998, 2001, earthquake occured with magnitude < 3 SR caused the growth of coral reef was above average value 9.1 mm. In 2005, an earthquake with repetition frequency of 33 times/year and highest magnitude 6.8 SR caused decline in growth of coral reef 6.5 mm, decreased 23.1% from previous year. Concludedthat degradation of coral reef porites type central Tapanuli caused by anthropogenic causes, natural causes.
