Antibacterial Activity of Microalgae Dunaliella salina, Tetraselmis chuii and Isochrysis galbana Against Aquatic Pathogens

Recently, expanded consideration has been paid to the business and potentiality of microalgae. Some microalgae are at present being studied for their capacity to find important metabolites for the drug industry or aquacultural applications. Concerning these biotechnological challenges, there is a consistent exertion accommodated in both finding and taking advantage of new microalgal assets and fostering their putative business results or modern valorizations. The crude methanol extracts of three microalgae, Dunaliella salina, Tetraselmis chuii, and Isochrysis galbana, have been investigated for antibacterial activity using the disk diffusion method against aquatic pathogens of fish, shrimp, and shellfish e.g. Pseudomonas fluorescence and Vibrio harveyi. This research aimed to analyze the antibacterial activity of crude extract of these microalgae against aquatic pathogens. The disk diffusion method was used to investigate the antibacterial activity. The result showed that only T. chuii has the inhibition zone for both tested bacteria P. fluorescence and V. harveyi with the inhibition zone of 3.0 ± 0.6 mm on 100 µg. g–1 of extract concentration and 4.20 ± 1.1 mm against P. fluorescence on 10000 µg. g–1 of extract concentration. While D. salina and I. galbana have inhibition zone only for V. harveyi with the inhibition zone of 4.4 ± 0.6 mm and 3.2 ± 0.7 mm on 10000 µg. g–1 of extract concentration. These three microalgae may have potential use in aquatic pathogens as antimicrobial agents. It would be possible to develop biologically active compounds of microalgae as a functional feed for aquaculture.

Exploration of Plastic-Degrading Bacteria From Marina Beach, Semarang, Central Java

Plastic waste has threatens the environment and affect to the economic and tourism sectors, marine life, coastal ecosystems and human health. World Wide Fund for Nature (WWF) states that 85% of waste in the oceans is plastic. The Ministry of Environment and Forestry also noted that Indonesia experienced an increase in plastic waste from 14% in 2013 to 16% in 2016. By 2020 the volume of plastic waste in Indonesia predicted to reach 67.8 million tons. Plastic waste takes 100-500 years to completely decompose. An alternative solution is to involve microorganisms to decompose plastic polymers. However, plastic waste reducing bacteria isolated from coastal ecosystem has not been much explored. In this study, an exploration of natural bacteria that degrades plastic waste from coastal ecosystems is carried out. Plastic samples were collected from the Marina Beach Semarang, Central Java. Plastic samples were taken from a depth of 0-10 cm in three coastal ecosystems: coastal sand sediments, rocks and mangroves. Samples then isolated and screened to obtain bacteria that have the potential to degrade polyethylene. Selected bacteria were identified by biochemical physiology according to the method of Cappuccino and Sherman and classified to genus level according to Bergey's Manual of Determinative Bacteriology and Bergey's Manual of Systematic Bacteriology. The results showed that three genera of bacteria had high polyethylene degradation potential with the speed of degradation: Enterobacteriaceae 0.0091%; Moraxella spp. 0.0066%; and Pseudomonas spp. 0.0076% per week.

Producing Active Secondary Metabolite Against Pathogenic Vibrio spp. by Actinobacteria-Sodium Alginate Co-Culture

Vibrio vulnificus, Vibrio parahaemolyticus and Vibrio harveyi have been found in aquatic environments and suspected as the primary trigger of WFD (White Feces Disease) outbreaks in aquaculture. This Vibrio spp. has an antibiotic resistance to Ampicillin, Co-Amoxiclav, Amoxicillin, Azithromycin, Actinobacteria and Ciprofloxacin HCL. Actinobacteria and alginate have been reported to increase the marine biota resistance against diseases through prebiotic and probiotic mechanisms. This study aims to discover and increase the secondary metabolite production of Actinobacteria-Alginate and its ability as anti-vibrio. Alginate extraction in the samples dated September 2020 originally from Teluk Awur Bays, Jepara, Central Java, Indonesia (33.73±1.84%) was considerably higher than in May 2021 (22.67±0.3%). Samples were taken from sediment and mangrove root. Actinobacteria strains are macroscopically and microscopically similar to the genus Streptomyces. The most well-known antibiotics were produced by Streptomyces spp. The anti-vibrio test was carried out by Kirby-Bauer disc diffusion. The results were observed by measuring the inhibition zone surrounding the paper disc using a digital calliper. Co-culture strain 90 together with alginate have an approved antibacterial activity against all Vibrio spp. in the concentration of 10.disc-1 mg and 5 mg.disc-1. Co-culture Actinobacteria with alginate has remarkably changed the green-yellow color to olive green/dark red-orange (strains 3, 62, 63, 72, and 90), indicating the transformation of the formation alginate with pigments into other compounds through the biosynthetic pathway. Therefore, alginate enables to support of Actinobacteria by induction the active secondary metabolite as an anti-vibrio to counteract the bacterial pathogen diseases.

Biodegradation of Polyethylene Microplastic using Culturable Coral-Associated Bacteria Isolated from Corals of Karimunjawa National Park

Polyethylene is a plastic material that was globally produced and is well known as a non-degradable pollutant product. Plastic pollution, primarily microplastics, have been distributed to coral reef ecosystems, where these areas are ecosystems with high productivity. Karimunjawa National Park in Indonesia is one of the protected areas for coral reef ecosystem habitat in Central Java, threatened by microplastic contamination. Recent studies have shown that coral-associated bacteria have an adequate ability to degrade marine pollutant materials. No one has reported that the use of indigenous coral-associated bacteria has the potential for microplastic biodegradation, especially low-density polyethylene microplastic materials. Hence, the objective of this study was to find the potential of microplastic biodegradation agents derived from coral-associated bacteria in Karimunjawa National Park area. Various coral life-forms were isolated in July 2020 from conservation areas and areas with anthropogenic influences. Bacterial isolates were screened using tributyrin and polycaprolactone as substrates to reveal potential microplastic degradation enzymes. The total isolation results obtained 92 bacterial isolates, and then from the result of enzyme screening, there were 7 active bacteria and only 1 bacteria that potential to degrade polyethylene. LBC 1 showed that strain could degrade by 2.25±0.0684 % low-density polyethylene microplastic pellet by incubating bacterial growth until the stationary phase. Identification of LBC 1 strain was carried out by extracting DNA and bacterial 16S rRNA sequences. Bacterial gene identification refers to Bacillus paramycoides with a similarity level in the National Center Biotechnology Information database of 99.44%. These results prove that hard coral association bacteria can degrade low-density polyethylene microplastics.

Marine bacterium Seonamhaeicola algicola strain CC1 as a potential source for the antioxidant carotenoid, zeaxanthin

Currently, there are only six species in the genus Seonamhaeicola, i.e., Seonamhaeicola aphaedonensis, S. algicola, S. marinus, S. acroporae, S. maritimus, and S. sediminis. These bacteria have typical yellow or orange color. Among the identified strains, only S. marinus that had been reported to have a yellow polyene flexirubin pigment. However, the presence of carotenoid pigments has not been reported in this genus. Recently, we successfully isolated a new strain, S. algicola strain CC1, bacterium that was found in association with a red seaweed, Halymenia sp., collected from the coast of South Malang, Indonesia. The strain was grown well in the Zobell marine agar 2216E producing yellowish pigments. According to the 16S rRNA sequencing analysis and BLAST search, the strain is closely related to S. algicola strain Gy8, with 99.78% identity. The pigment composition was separated and analyzed by a high-performance liquid chromatography with tandem mass spectrometry detection (HPLC-MS/MS) and the strain was found to produce zeaxanthin as the major component, which appeared at a retention time (tR) of 28.89 min, showing a typical mass spectrum with a molecular ion at m/z 568.5 [M]+ and four product ions at m/z 261.4 [M−307]+, 476.6 [M−92]+, 429.3 [M−139]+, and 536.5 [M− 32]+. Other carotenoids, including zeaxanthin cis isomers, β-cryptoxanthin, β-carotene cis isomer, and β-carotene, are as minor components. The novel and noteworthy finding of this report is the identification of a Seonamhaeicola species that produces carotenoids and can be used as a source of zeaxanthin.

Observed features of the water masses in the Halmahera Sea in November 2016

Halmahera Sea is one of the locations in the eastern route of Indonesian Throughflow (ITF), where high salinity water is mainly transported by the ITF. The description of water mass in the Halmahera Sea from the perspective of water mass, and related mixing is important. It is not only useful for understanding water mass features, but it can also be used to determine the strength of the turbulent mixing, and so allow how it relates to the water transformation. Here, we report the water mass properties and estimation of mixing quantities in the Halmahera Sea from the CTD profiles based on recent onboard observations during the IOCAS cruise in November 2016. The water mass analysis was done by examining the characteristics of water types in the Temperature-Salinity (T-S) diagram. The mixing estimation uses the density profile derived from temperature and salinity profiles and the quantification of vertical turbulence observed by density overturn. Halmahera Sea is to be found as the location where the thermocline salinity changes abruptly, it is shown from the erosion of salinity maximum in the density of 22-26σθ decreased from the north to the south of the basin. It is associated with strong mixing with spots of higher vertical diffusivity in the thermocline and intermediate layer. In the upper layer, the mixed layer depth in the Halmahera Sea is relatively shallow with an average of about 16.95 m and it is associated with weak wind stress during this month.

Prediction of Salinity Based on Meteorological Data Using the Backpropagation Neural Network Method

Salinity is the level of salt dissolved in water. The salinity level of seawater can affect the hydrological balance and climate change. The salinity level of seawater in each area varies depending on the influencing factors, that is evaporation and precipitation (rainfall). One way to find out the salinity level is by taking seawater samples, which requires a long time and costs a lot. In this study, the salinity level of seawater can be predicted by utilizing time series data patterns from evaporation and precipitation using artificial neural network learning, namely the backpropagation neural network. The evaporation and precipitation data used were derived from the ECMWF dataset, while the salinity data were derived from NOAA where each data was taken at the coordinate point of 9,625 113,625 in the south of Java island. Seawater salinity, evaporation, and precipitation data were formed into a 7-day time series data. This study conducted several backpropagation architectural experiments, that is the learning rate, hidden layer, and the number of nodes in the hidden layer to obtain the best results. The results of the seawater salinity prediction were obtained at a MAPE value of 2.063% with a model architecture using 14 input layers, 2 hidden layers with 10 nodes and 2 nodes, 1 output layer, and a learning rate of 0.7. Predicted sea water salinity data ranging from 33 to 35 ppt. Therefore, the prediction system for seawater salinity using the backpropagation method can be said to be good in providing information about the salinity level of sea water on the island of Java.

The Status of Seagrass Health: Supporting Sustainable Small-Scale Fisheries in Misool Marine Protected Area, Raja Ampat, Indonesia

Seagrass plays an important role in aquatic resources, such as to support the sustainable management of small-scale fisheries, ensuring the availability of seagrass stocks for generations of local communities to cultivate in a sustainable manner. The purpose of this study is to provide information on the seagrass health status to support sustainable small-scale fisheries in the South Misool Regional Waters Conservation Areas which is located within the Raja Ampat Marine Protected Area of West Papua. The research was conducted in January 2019 in the Yefgag, Yellu and Harapan Jaya island. A total of ten quadratic transects measuring 1x1 m were laid perpendicularly to the coastline adapted from the seagrass watch method to collect the seagrass data, i.e. the species and the frequency of seagrass found, the dominance and the percentage of seagrass cover. Additional data on fish species were collected by interviewing the local fishermen directly. The relationship between seagrass cover and the number of fish species was analyzed. Th results showed that there were eight species of seagrass found in three observation stations, i.e. Halophila ovalis, Halodule uninervis, Halodule pinifolia, Halophila minor, Syringodium isoetifolium, Cymodocea serrulata, Cymodocea rotundata and Enhalus acoroides. According to the standard criteria for the health status of seagrass beds, the three locations are classified as less rich/less healthy. It because the seagrass coverage was in the range of 30-59%. The relationship between the percentage of seagrass cover and the number of fish species resulted equation of Y = 15,923x + 0,3174 with R2 = 0,763. It means that the percentage of seagrass cover affects the abundance of fish species by 76,3% with the remaining being influenced by other variables, such as water quality.

Difference in Diet and Water Quality Influencing the Growth of the Newly Introduced Penaeus merguiensis Larva Culture

The water quality found on the surface is usually better than that accumulated at the seabed and more bottomless sea. When recycled, water usually brings many materials along the path, all the way to reaching its end. Water quality varies from place to place, season, and different types of rock and soil it passes through also influences the possessed quality. By employing Penaeus merguiensis larvae produced by the Marine Research Center Hatchery owned by Jepara's government, this study analyzes varying effects in three nominal salinities (28, 32, and 36 ppt) and types of diets (Diet A: 100% live feed; Diet B: 100% FRIPPAK; Diet C: a combination of Diet A and Diet C, 50 % each) and finds the optimum water quality parameters such as dissolved oxygen, pH, and temperature on the growth of the newly introduced Penaeus merguiensis larvae. The results show that two nominals of water salinities (28 and 32 ppt) with Diet A works well, supporting the growth from most Zoea to Postlarvae-1: Zoea-1 at 28 ppt with Diet A; Zoea-2 at 32 ppt with Diet A; Zoea-3 at 32 ppt with Diet A; Mysis-1 at 28 ppt with Diet A; Mysis-2 at 28 ppt with Diet C; Mysis-3 at 28 ppt with Diet A; Postlarva-1 at 28 ppt with Diet A. All shrimp prefers temperature ranging from 31-32.4 °C with dissolved oxygen of 4.9-5.74 ppm and pH 7.0-8.1.

Potential Study of Tidal Stream Turbine Farm at Toyapakeh Strait, Bali

In 2015, Bali Province is mandated by ESDM ministry to become the National Region of Clean Energy, promoting efforts to explore new source of electricity namely tidal stream energy. Previous works have demonstrated that Toyapakeh Strait contains a promising tidal stream resource, with a high stream in a long period. In this study, hydrodynamic modelling and power production analysis is conducted to evaluate this potential with an aim to meet energy demand of Tiga Nusa Cluster Islands. Twenty-one Gen5 KHPS turbines are employed in this study, at an optimized location, 8.72°S, 115.44°E, which contains the highest energy potential. Financial analysis, with 25-year return period of investment and 3.60% interest rate, resulting levelized cost of energy (LCOE) of Rp 6,100.kWh-1. This value is higher than the national and regional selling nominal, in other word the energy cost of tidal stream turbine is relatively high in this location. Nearly 46% of energy cost is spent for turbine fabrication, and from the sensitivity analysis, cutting half the turbine costs may reduce the price by Rp 1,400.kWh-1 while increasing the amount of installed turbine is less significant. Despite of the high prices, the study shows that Toyapakeh Strait holds a promising resource of tidal stream energy.