SURFACE OCEAN RADIOCARBON FROM A PORITES CORAL RECORD IN THE GREAT BARRIER REEF: 1945–2017

ABSTRACT We present a high-resolution seawater radiocarbon (Δ14C) record from a Porites coral collected from Masthead Island in the southern Great Barrier Reef (GBR) covering the years 1945–2017. The Δ14C values from 1945–1953 (pre-bomb era) averaged –49‰. As a result of bomb-produced 14C in the atmosphere, Δ14C values started to rise rapidly from 1959, levelled off at ∼131‰ in the late 1970s and gradually decreased to ∼40.3‰ by 2017 due to the decrease in the air-sea 14C gradient and the overturning of the 14C ocean reservoir (i.e., surface ocean to subsurface ocean; atmosphere to surface ocean). The Masthead Island record is in agreement with previous 14C coral records from the southern GBR. A comparison between surface ocean and atmospheric Δ14C suggests that, since 2010, the main reservoir of bomb-derived 14C has shifted from the atmosphere to the surface ocean, potentially resulting in reversed 14C flux in regions where the CO2 gradient is favorable. The high-resolution Masthead coral Δ14C sheds light on long-term variability in air-sea exchange and GBR regional ocean dynamics associated with climate change and in conjunction with the previous records provides a robust seawater 14C reference series to date other carbonate samples.

Bakteri Simbion Karang Porites dari Perairan Gunungkidul, Yogyakarta dan Aktivitas Antibakteri terhadap Bakteri Patogen Staphylococcus aureus dan Escherichia coli

Porites merupakan genus karang yang memiliki persebaran luas di Indonesia, termasuk perairan Gunungkidul, Yogyakarta. Penelitian menunjukkan bahwa bakteri simbion karang Porites memiliki potensi antibakteri dalam menanggulangi bakteri patogen. Penelitian ini betujuan untuk mengetahui jenis bakteri simbion karang Porites dari Perairan Gunungkidul Yogyakarta yang memiliki aktivitas antibakteri patogen S. aureus dan E. coli. Bakteri simbion diisolasi dari fragmen jaringan karang dengan pengenceran bertingkat, kemudian uji aktivitas antibakteri dilakukan dengan menggunakan metode overlay dan difusi paperdisk. Delapan dari 64 isolat aktif menghambat kedua bakteri patogen Staphylococcus aureus dan Escherichia coli. Dua diantaranya merupakan isolat unggul yang menunjukkan aktivitas antibakteri paling baik. Kedua isolat selanjutnya diidentifikasi karakteristik molekular DNA dengan sekuen gen 16S rRNA. Hasil identifikasi 16S rRNA menunjukkan isolat GKP1.4.3 memiliki kesamaan 99% dengan Bacillus pumilus strain NBRC 12092, dan isolat GKP3.2.2 memiliki kesamaan 99% dengan Vibrio natriegens strain NBRC 15636.Porites is a coral which has distributed widely in Indonesia, including Gunungkidul Waters, Yogyakarta. Research has shown that Porites coral symbiont bacteria have antibacterial potency against pathogenic bacteria.This study aims to determine the type of Porites coral symbiont bacteria collected from the waters of Gunungkidul Yogyakarta which has antibacterial activity of S. aureus and E. coli. Bacteria symbionts were isolated from coral tissue fragments by serial dillution method, while antibacterial activity was performed by using overlay and paperdisk diffusion method. Eight of the 64 active isolates inhibited both pathogenic bacteria S. aureus and E. coli. Two of 8 isolates showed stronger antibacterial activity. The two isolates subsequently identified the molecular characteristics of DNA with the 16S rRNA gene sequence. The identification of 16S rRNA showed that GKP1.4.3 isolate had 99% similarity with Bacillus pumilus strain NBRC 12092, and GKP3.2.2 isolate had 99% similarity with Vibrio natriegens strain NBRC 15636.