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Abstract. Wijaya A, Zakiyah U, Sambah AB, Setyohadi D. 2020. Spatio-temporal variability of temperature and chlorophyll-a concentration of sea surface in Bali Strait, Indonesia. Biodiversitas 21: 5283-5290. The Bali Strait is influenced by seasonal and inter-annual systems. El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are climate variabilities that affect water conditions. The knowledge about influence of ENSO and IOD variations on the fertility of waters in the Bali Strait is still lacking. The purpose of this study was to determine the effect of seasonal and inter-annual variability on the variability of Sea Surface Temperature (SST) and Sea Surface Chlorophyll-a (SSC) in the Bali Strait. This study applied SST and SSC data collected from the Aqua/Terra MODIS satellite, as well as the ENSO and IOD indices during March 2000-December 2019. The results described that the effect of ENSO on SST and SSC was low and IOD on SST and SSC was quite high. The effect was quite high between IOD and SST anomaly of-0.401. Seasonal variations indicate the abundance of high SSC and low SST in the southeast monsoon (JJA) which characterizes upwelling. Meanwhile, in the northwest monsoon (DJF), SSC was low and SST was high which characterizes downwelling. This condition cannot separate from the monsoonal process that occurred in the Bali Strait. The inter-annual variation showed that in the strong El Nino period and IOD (+) triggers a negative SST anomaly and a positive SSC results in strong upwelling, while in the strong La Nina period and strong IOD (-) triggers a positive SST anomaly and a negative SSC results in downwelling. The inter-annual variability of SSC influenced by IOD rather than ENSO. This condition indicates that the ENSO/IOD event changes the period of SSC concentration.

ABSTRAKPulau Sempu adalah satu-satunya cagar alam yang berada di Kabupaten Malang yang memiliki terumbu karang dengan luasan kurang dari 10 ha yang mampu bertahan dari banyaknya ancaman yang berpotensi merusaknya. Faktor lingkungan secara alamiah telah menyeleksi keanekaragaman diwilayah perairan P. Sempu, yakni hanya 9 life form karang keras yang berperan sebagai penyangga ekosistem terumbu karang di wilayah ini. Mengetahui distribusi ukuran koloni karang sama pentingnya mengetahui umur koloni karang keras untuk melihat kondisi ekosistem terumbu karang pada suatu perairan. Klas frekuensi koloni karang keras akan memberikan informasi mengenai kemampuan kompetisi, masa pubersitas dan tentu kemampuan regenerasi. Pengambilan data luasan karang dilakukan di 4 stasium (Watu Mejo 1, Watu Mejo 2, Teluk Semut 1 dan Teluk Semut 2) menggunakan kuadrat transek 1 x 1 m sepanjang 50 m pada kedalaman 5m. Berdasarkan penelitian didapatkan luasan total tertinggi pada Acropora Branching (ACB) adalah 145.811,67 cm 2 dan terenda pada karang jamur (CMR) 414,35 cm 2 . Life form karang dapat dijadikan rujukan awal menilai kesehatan ekosistem terumbu karang. Dominan karang dengan life form massive dapat diartikan kawasan tersebut memiliki kondisi lingkungan yang penuh tekanan semisal sedimentasi tinggi, arus kuat maupun sering terekspos udara. Ukuran karang di P. Sempu rerata menunjukkan > 5 cm 2 yang berarti sudah dewasa dan mampu melakukan reproduksi, sedangkan rekruitmen sangat rendah dengan indikasi sedikitnya jumlah luasan karang kurang dari 4 cm 2 .Kata kunci: cagar alam, bentuk pertumbuhan, reproduksi, konservasi, karang keras ABSTRACTThe abundance of coral reef in Sempu Island nature reserve was under 10 ha, in which they were a winner from environment and human threats. The environment has big role to select scleractinian coral in this area that resulted 9 coral life form as the main foundation of coral reef in Sempu nature reserve area. Knowing the coral size distribution as important to know of coral age in term determining the health of coral reef ecosystem. Class frequency of colony size gave the key information of coral competition, puberty and regeneration ability. We choose 4 station (Watu Mejo 1, Watu Mejo 2, Teluk Semut 1 dan Teluk Semut 2) to take data. Data colony size was taken by 1 x1 m quadrat along 50 m in 5 m depth. The highest colony size was Acropora branching (ACB) about 145,811.67 cm 2 and the lowest one was mushroom coral (CMR) about 414.35 cm 2 . Life form of coral can be early detection of coral reef health. Dominance of massive coral means the coral reef under the high sedimentation, strong current or exposed by air frequently. The coral colony size in Sempu nature reserve showed > 5 cm 2 that indicate they were in maturity and have capability for reproduction but the coral recruitment was very low due to few number of coral has less than 4 cm 2 in colony size.

This study aims to find scientific data concerning distribution pattern of R. argyrotaenia, catch composition of R. argyrotaenia including length frequency data, fishing peak season, spawning season, and abiotic characteristics of aquatic environment, such as life of R. argyrotaenia. The findings indicate that distribution pattern of R. argyrotaenia during rainy season (January-April) is scattered in main river, tributary, and marsh (flood plain), during dry season (May-August), position of fish is in main river and tributary, while in transitional months (September-December), fish is concentrated in main river. Fishing peak season occurs in April, May, June, and July reaching average haul range of 9.98 kg/month + 0.62-12.63 kg/month + 1.08. Based on Analysis of Progression Model by utilizing FISAT II on length-based data of R. argyrotaenia, there found three cohorts by average length of 65.76 ISSN 2157-6092 2014 www.macrothink.org/jee 118 mm + 9.0, 116.13 mm + 15.0, and 156.63 mm + 4.7. Referred to analysis of the Von Bartalanffy growth curve, it is known that inital spawning season of R. argyrotaenia alleged that the peak spawning season occurs in September, October, November and December reaching value of Linf=173.25, K=0.510/year, and t0=0.02. R. argyrotaenia lives in habitat where average temperature is 25.5 oC + 0.12 -31.6 oC + 0.12, current speed of 0.06 ms-1+ 0.02 -0.27ms-1 + 0.02, pH of 4.23 + 0.03 -6.74 + 0.05, and DO of 4.2 mg l-1 + 0.06 -7.5 mg l-1 + 0.10. Journal of Environment and Ecology

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