Eastern Java Sea Research Articles

The Red Snapper Fishery in the Eastern Java Sea and Its Fishery Management Recommendation

Abstract For decades, the red snapper fishery has been considered a potential demersal fishery in the east part of Java Sea. The fluctuating fishing effort caused the biomass of red snapper has a fluctuate every year. The study’s goal is to analyze the changing conditions of the red snapper fishery in the east part of Java Sea as a basis for developing management recommendations. The production and efforts data were collected from Brondong Nusantara Fishing Port from 2008 to 2021. The data was analyzed using a non-equilibrium surplus production model and depicted using Kobe Plot to know the change direction of red snapper fishery. The result shows that red snapper fishery in the east part of Java Sea has been overfishing with the abundance of biomass has been overfished. This study’s recommendations for fisheries management are to limit fishing efforts and allowable catch in order to improve the red snapper fishery in the east part of Java Sea.

Characteristics and Distribution of Chemical-Biological Parameters in The Seawaters of Eastern Java Sea

The Java Sea is influenced by the west and east monsoons, which have an impact on hydrodynamic processes and chemical-biological water quality. Chemical-biological parameters play an important role in the food chain cycle that occurs in these waters. The quality of the eastern Java Sea waters is still limited by chemical-biological parameters, so the characteristics and distribution of these waters can be comprehensively known. chemical-biological. This study aimed to analyze the characteristics and distribution of nitrate, phosphate, oxygen, chlorophyll-A, and NPP parameters in the eastern Java Sea waters. This study used secondary data with daily temporal resolution from January to December 2020. Spatial analysis uses the climatological averaging method for 6 months as a statistical representative of the west monsoon and east monsoon. For each parameter, a vertical analysis was conducted to compare parameter values between the coastal waters of Tuban, Java Sea, and Banjarmasin Waters. Correlation analysis between parameters was conducted using the Pearson correlation method. Nitrate, phosphate, oxygen, chlorophyll-A, and NPP concentrations have temporal and spatial variability. Monsoon factors in Indonesia have a strong influence on the variability of nitrate, phosphate, oxygen, chlorophyll- A, and NPP concentrations. During the east monsoon, the concentration of chemical-biological parameters decreases, while in the west monsoon, the concentration increases and reaches its highest value. Generally, high concentrations occur in the northern and southern parts of the study site, around the coastal areas of Java and Kalimantan. Key Word: Chemical-Biological Parameters, Java Sea, Tuban Waters

Population Dynamic Parameters and Length Based Spawning Potential Ratio (LB-SPR) of Red Snapper (Lutjanus malabaricus) in The Eastern Java Sea

Decision in fisheries management must be made based on the best scientific evidence available. In the poor data fisheries, the fish length data can be useful to determine the status of fish population after its exploitation. The target species of the studied fisheries is the red snapper (Lutjanus malabaricus) in the eastern Java Sea. This study aims to analyze the stock status of red snapper in the eastern Java Sea using Length Based Spawning Potential Ratio (LB-SPR) method. Data collection was done from November 2020 until April 2021. This study separated the analysis of the population dynamic parameters between male and female fish. The growth parameters of male fish was Lt = 92.20 (1 – e−0.27(t-0.07)), with natural mortality (M) of 0.35, fishing mortality (F) of 0.63, and total mortality (Z) of 0.98 per-year. Whereas for female fish, Lt = 91.09 (1 – e−0.29(t-0.44)), with M of 0.38, F of 1.40, and Z of 1.78. The exploitation rate (E) for males was 0.64, and for the female was 0.79. The spawning potential ratio (SPR) was 17%, below the limit reference point of 30% SPR. The current utilization rate of the red snapper in the eastern Java Sea must be reduced to ensure its sustainability.

The Identity of Homoioplax haswelli (Miers, 1884) (Crustacea: Decapoda: Brachyura).

The brachyuran crab Pseudorhombila haswelli Miers, 1884, described on the basis of two juveniles from the Arafura Sea, is a poorly known species of uncertain systematic position. It was made the type and only species of Homoioplax Rathbun, 1914, and assigned to the Prionoplacinae (Goneplacidae). Subsequent revisions of the goneplacids showed Prionoplacinae to be a junior synonym of Eucratopsinae Stimpson, 1871, as a member of the Panopeidae Ortmann, 1893, but no one has re-evaluated the position of Homoioplax. As a result, Homoioplax has remained in the Panopeidae as the only Indo-West Pacific representative of the family. This study assesses the systematic status of Homoioplax haswelli based on a re-examination of the type and other material of the species. Homoioplax haswelli is here attributed to Carcinoplax H. Milne Edwards, 1852 (Goneplacidae), justifying the recognition of the species described by Miers as C. haswelli. Moreover, Carcinoplax haswelli is shown to be a senior synonym of C. sinica Chen, 1984, described from the South China Sea. Therefore, C. haswelli is now known to range from southern Taiwan and the Philippines, through the South China Sea, northern Vietnam, the eastern waters of Singapore to the Madura Straits in eastern Java and Arafura Sea, northern Australia, at 25-187 m, but usually less than 100 m depth.

Influences of Physical Processes and Anthropogenic Influx on Biogeochemical Cycle in the Java Sea: Numerical Model Experiment

Three-dimensional coupled physical-biogeochemical model was utilized in order to investigate the influence of physical processes to biogeochemical cycle in the Java Sea. The biogeochemical model was consisted of nitrate, ammonium, phosphate, phytoplankton, zooplankton, pelagic detritus and benthic detritus. The coupled model could reproduce the basic condition of seasonal variability of surface Chl a distribution consistently with satellite data. Model results and satellite data clearly showed seasonal variability of Chl a distributions, influenced by monsoon, through water exchange with adjacent seas and nutrient supply from rivers discharges. Phytoplankton blooming during southeast monsoon is higher in general than northwest monsoon, due to upwelling event in the eastern Java Sea. On the other side, the role of nutrient riverine input during northwest monsoon (rainy season) is only limited in the region near river mouths or coastal regions. The calculated annual new productions (Rnew) suggested that the regenerated production is predominant in the Java Sea, except for some regions (e.g: Jakarta Bay and south-coast of Kalimantan) that is influenced by human activities in the land (anthropogenic perturbation). The anthropogenic impact through riverine input triggers high primary production in the regions, while it subsequently uptakes atmospheric CO2 in particular monsoon season. However, as a consequence of high sea surface temperature in the tropical region, annually the entire Java Sea acts as a source for CO2 even though the Java Sea is a net autotrophic.

A NUMERICAL MODELING STUDY ON UPWELLING MECHANISM IN SOUTHERN MAKASSAR STRAIT

<p><strong><em>ABSTRACT</em></strong></p> <p><em>While it has been well documented in the previous studies that upwelling events in the southern Makassar Strait (MAK) during the Southeast Monsoon (SEM) period are associated with low sea surface temperature (SST) and high chlorophyll-a (Chl-a) concentrations in the seawater, the dynamic and physical processes that trigger these upwelling events are still less well understood. In the present study we proposed a mechanism of the upwelling event using a numerical model of the Regional Ocean Modeling System (ROMS). Model validations showed a high correlation of SST climatology between the model and the NOAA-AVHRR satellite data. Moreover, </em><em>velocity fields of the Indonesian Throughflow (ITF) Makassar in Libani Channel was well reproduced by proposed model, revealing an intensification of the flow centered near 120 m depth, which is in good agreement with the observation data. </em><em>The model demonstrated that during the SEM period strong southeasterly winds that blow over southern Sulawesi Island can increase high vertical diffusivity and heat loss through heat flux. Hence, these physical processes lead to increased vertical mixing that, in turn, generates low SST, as a proxy of upwelling event. Furthermore, the upwelling process is enhanced by the ITF Makassar jet that creates large circular eddies flow due to complex topographic within the triangle area of southern Makassar - eastern Java Sea - western Flores Sea. The eddies generate the area of convergence offshore along the ITF pathways and divergence area in the coastal waters close to southern Sulawesi Island. Model experiment with closing/opening Selayar Strait revealed a change of intensity and area of upwelling, suggesting that the Selayar Island forms a barrier for the outflow from MAK to northern part of Flores Sea.</em><em> </em></p> <p><em> </em></p> <strong><em>Keywords: </em></strong><em>Upwelling, ITF Makassar, SE monsoon winds, ROMS-AGRIF, Makassar Strait.</em>

A NUMERICAL MODELING STUDY ON UPWELLING MECHANISM IN SOUTHERN MAKASSAR STRAIT

ABSTRACT While it has been well documented in the previous studies that upwelling events in the southern Makassar Strait (MAK) during the Southeast Monsoon (SEM) period are associated with low sea surface temperature (SST) and high chlorophyll-a (Chl-a) concentrations in the seawater, the dynamic and physical processes that trigger these upwelling events are still less well understood. In the present study we proposed a mechanism of the upwelling event using a numerical model of the Regional Ocean Modeling System (ROMS). Model validations showed a high correlation of SST climatology between the model and the NOAA-AVHRR satellite data. Moreover, velocity fields of the Indonesian Throughflow (ITF) Makassar in Libani Channel was well reproduced by proposed model, revealing an intensification of the flow centered near 120 m depth, which is in good agreement with the observation data. The model demonstrated that during the SEM period strong southeasterly winds that blow over southern Sulawesi Island can increase high vertical diffusivity and heat loss through heat flux. Hence, these physical processes lead to increased vertical mixing that, in turn, generates low SST, as a proxy of upwelling event. Furthermore, the upwelling process is enhanced by the ITF Makassar jet that creates large circular eddies flow due to complex topographic within the triangle area of southern Makassar - eastern Java Sea - western Flores Sea. The eddies generate the area of convergence offshore along the ITF pathways and divergence area in the coastal waters close to southern Sulawesi Island. Model experiment with closing/opening Selayar Strait revealed a change of intensity and area of upwelling, suggesting that the Selayar Island forms a barrier for the outflow from MAK to northern part of Flores Sea. Keywords: Upwelling, ITF Makassar, SE monsoon winds, ROMS-AGRIF, Makassar Strait.

Recorders of reef environment histories: stable isotopes in corals, giant clams, and calcareous algae

Time-series δ18O and δ13C records from cohabiting massive coralPorites australiensis and giant clamTridacna gigas from the Great Barrier Reed of Australia, and from calcareous green algae in a core through modernHalimeda bioherm accreting in the eastern Java Sea, provide insights into the complex links between environmental factors and stable isotopes imprinted in these reef skeletal materials. The aragonitic coral and giant clam offer 20 years and 15 years of growth history, respectively. The giant clam yields mean δ18O and δ13C values of-0.5±0.5‰ and 2.2±0.2‰ (n=67), which agree well with the predicted equilibrium values. The coral yields mean δ18O and δ13C values of-5.6±0.5‰ and-1.8±0.7‰ (n=84), offering a striking example of kinetic and metabolic fractionation effects. Although both the coral and giant clam harbor symbionts and were exposed to a uniform ambient environment during their growth histories, their distinct isotopic compositions demonstrate dissimilar calcification pathways. The δ18O records contain periodicities corresponding to the alternating annual density bands revealed by X-radiography and optical transmitted light. Attenuation of the δ18O seasonal amplitudes occurring in the giant clam record 8 years after skeletal growth commenced is attributed to a changeover from fast to slow growth rates. Extreme seasonal δ18O amplitudes of up to 2.2‰ discerned in both the coral and giant clam records exceed the equivalent seasonal temperature contrast in the reef environment, and are caused by the combined effect of rainfall and evaporation during the monsoon and dry seasons, respectively. Thus in addition of being useful temperature recorders, reef skeletal material of sufficient longevity, such asPorites andTridacna, may also indicate rainfall variations. Changing growth rates, determined from the annual growth bands, may exert a primary control on the coral δ13C record which shows a remarkable negative shift of 1.7‰ over its growth history, by comparison with only 0.15‰ negative shift in the contemporaneous giant clam record. Use of coral δ13C records as proxies of fossil fuel CO2 uptake by the ocean must be regarded with caution. The δ18O and δ13C records fromHalimeda are remarkably uniform over 1000 years of bioherm accretion history (δ18O=-1.7±0.2‰; δ13C=3.9±0.1‰,n=28), in spite of variable Mg-calcite cements present in the utricles. Most of the cement infilling is probably syndepositional, and both theHalimeda aragonite and the Mg-calcite cements containign 12.3 mole % MgCO3 are deposited in isotopic equilibrium. Therefore, in favorable circumstances these algal skeletal remains may act as the shallow water analogs of benthic foraminifera in deep sea sediments in recording ambient sea water isotopic composition and temperature.

Morphology and sedimentology of Halimeda bioherms from the eastern Java Sea (Indonesia)

Halimeda bioherms, occurring primarily along the western and southern margins of Kalukalukuang Bank in the eastern Java Sea, display a wide variety of thicknesses and shapes. In general, high-frequency forms of the northern bank are replaced by thicker and lower frequency forms along the deeper southern margin. Sidescan sonar data suggest aperiodic reworking of shallow bioherm crests of the northern bank into features suggestive of bedforms. These features are not associated with deeper bioherms of the southern bank. Cores from the bioherms indicate that they consist mostly of disarticulated Halimeda plates set in a lime mud matrix composed largely of Halimeda fragments and foraminifera tests. Carbon-14 dating shows that, with exception of some deep southern bank examples, bioherms are actively accreting. Results of mineralogy and elemental chemistry on piston core PC-12 suggest cyclic variations in Mg-calcite (cement in Halimeda utricles), which may be related to periodic excursions of cold Pacific throughflow water onto the bank. Composition of the Mg-calcite (8.6 mole-%) suggests a temperature of formation of about 22 °C, which is 7 °C below average surface water temperatures. The carbon and oxygen isotope compositions of both aragonite and Mg-calcite phases are remarkably homogeneous, but were inconclusive with regard to the cold-water intrusion hypothesis. However, a lack of reef-building corals below a depth of ∼15 m, abundance of Halimeda bioherms on the western margin of K-Bank, where upwelling is predicted, extensive boring of sedimentary particles by endolithic boring algae, and high nutrient values of water at the thermocline (50–70 m deep) all support the incursion of cold, nutrient-rich water onto the bank. Upwelling and nutrient overloading are suggested as explanations for remarkable algal growth at the expense of reef-building corals.

Seismic characteristics and accretion history of Halimeda bioherms on Kalukalukuang Bank, eastern Java Sea (Indonesia)

Extensive areas of Halimeda bioherms similar to those described by Orme et al. (1978), Orme (1985), Davies and Marshall (1985), and Phipps et al. (1985) from Australia's Great Barrier Reef have formed on Kalukalukuang Bank (K-Bank) 50 km east of the Sunda Shelf margin in the easter Java Sea. K-Bank is an isolated limestone platform whose top slopes southward from a water depth of about 20 m at the north to about 100 m at the south (≈30 km). It occurs in a bidirectional monsoonal wind regime and a predominantly southerly flowing current from Makassar Strait. The water column around K-Bank has a well developed shallow thermocline (50 m to 150 m). K-Bank has a relatively flat top with marginal banks of suspected Pleistocene origin as interpreted from seismic relationships. A reconnaissancelevel survey grid of high-resolution seismic profiles indicates that Halimeda bioherms are restricted to the bank margins with the exception of the eastern margin. Bioherms either extend to the steep margin of the platforms or are separated from the platform edge by banks of coral and coralline algae. The morphology of the Halimeda bioherms varies from steep-sided, elongate ridges in the northern bank area, through coalescing symmetrical mounds with partly infilled valleys, to broad undulating areas similar to those described by Orme (1985) from the Great Barrier Reef. High-resolution seismic records indicate erosional episodes in the high-relief areas, an interpretation that seems to be supported by accumulation rates calculated from C14 dates of cores. Thicknesses of Halimeda accumulation above a prominent reflector considered as Pleitocene, vary from around 20 m in the north to a maximum of over 50 m in the southwest. Accumulation rates obtained from dating of two cores to-ward the north of K-Bank, average 0.294 m/100 yr for core VC4 and a maximum of 0.59 m/100 yr in a part of core PC12. Dating of material from the top 30 cm of a deep bioherm (≈100 m) in the southwest of K-Bank, indicates that the growth rate of these bioherms has slowed markedly, presumably because of increasing water depth (decreasing light) over the Holocene transgression.

Morphology of largeHalimeda bioherms, eastern Java sea (Indonesia): A side-scan sonar study

The most extensive and thickestHalimeda bioherms reported from modern seas occur along both open and protected margins of Kalukalukuang Bank, eastern Java Sea (Indonesia). Seismic profiles suggest these features average 20 to 30 m thick (maximum ∼ 50 m) and developed over large areas by coalescence of individual mounds. Bioherm morphologies range from numerous small mounds (∼ 10–20 m diameter) through “hay-stack” features (∼ 100 m diameter) to broad swells. Some modern bank bioherms display surface forms that appear related to onbank flow from Makassar Strait. Upwelling of cold, nutritive water is likely responsible for unusualHalimeda productivity and large bioherm development.

Halimeda bioherms of the eastern Java Sea, Indonesia

Extensive areas of coalescing bioherms composed primarily of disarticulated Halimeda plates occur on a large carbonate bank (Kalukalukuang Bank) located 50 to 70 km east of the central Sunda Shelf margin (eastern Java Sea, Indonesia). High-resolution seismic profiles suggest that these features attain maximum thicknesses of up to 52 m above an acoustically reflective surface interpreted as the top of the Pleistocene. Piston cores and vibracores from the bioherms indicate a composition of Halimeda packstone containing varying amounts of foraminifera-rich carbonate mud. A shell lag occurs at their base above the Pleistocene(?) surface. Seismic stratigraphy of the bioherms suggests that they generally developed as individual mounds that accreted both vertically and laterally until they coalesced to form composite features. Discordant reflectors are common and probably represent morphological modifications associated with high-energy events, current scour, or local mass movement. Halimeda bioherms occur in water depths ≥20 m on both exposed and reef-protected bank margins, unlike the only other recorded modern examples, which occur in the lagoonal facies behind the northern Great Barrier ribbon reefs of Australia. Their presence and rapid growth rates (to 5.9 m/1000 yr as determined from carbon-14 dating of piston core subsamples) are possibly related to upwelling of deep, nutrient-rich, south-moving water from Makassar Strait.

Organic Geochemistry as Aid to Exploration in Eastern Java Sea: ABSTRACT

Organic Geochemistry as Aid to Exploration in Eastern Java Sea: ABSTRACT

Structural Framework of Sunda Shelf

The Sunda Shelf is one of the most extensive continental shelves of the world. In June-July 1971 a geophysical survey was conducted over the southern part of the shelf (Java Sea). Water depth, sediment thickness, and the gravity and magnetic fields were measured continuously. Expendable radiosonobuoys permitted seismic refraction measurements. These geophysical data, supplemented by data from earlier studies of the northern Sunda Shelf and geologic data from land areas, provide a comprehensive picture of the structural framework of the entire Shelf. The seismic reflection profiles show that the Sunda Shelf consists of three major units: the northern Sunda Shelf basinal area, the Singapore platform, and the Java Sea basinal area. In the northern unit are two large sedimentary basins (the Brunei and Gulf of Thailand basins) separated by the Natuna Ridge. In the Java Sea are several other basins separated by uplifts. The basins in the western Java Sea are approximately circular and seem to result from tensional forces, whereas those in the eastern Java Sea are narrow and long and appear to be the result of compressional forces. Radiosonobuoys revealed small basement features and resolved many strata having different seismic velocities. Faults are abundant throughout the Sunda Shelf and clearly control the distribution and shapes of the basins. The faults strike north-south in the western Java Sea and northeast-southwest in the eastern Java Sea. A major discontinuity trending north-south (termed here the Natuna rift in the northern Sunda Shelf and the Billiton depression in the western Java Sea) cuts the structures of the entire Sunda Shelf and continues southward across central Java to the deep-ocean floor. Analysis of magnetic anomalies shows that the region can be divided into several distinct magnetic provinces that do not everywhere follow the major structural units mapped by the seismic reflection data. These magnetic provinces coincide with corresponding provinces of lithic units. The gravity field over the central and southern Sunda Shelf averages about +30 mgal. Local gravity anomalies with relative amplitude of 10-25 mgal are superimposed on the regional background level. Although the local gravity anomalies were helpful in resolving the upper crustal structures, the cause for the high regional gravity is unknown. All of the geophysical studies serve to outline the distribution pattern of sediment-filled basins and intervening ridges and platforms beyond the level of understanding reached by early workers through inferences based upon the geology of the land areas, and beyond the scant publications of oil companies within the restricted areas of their concessions. These regional results may be helpful both for understanding the general structure of the Sunda Shelf and for denoting the areas with the greatest future oil potential. The main structural elements are interpreted as the result of past interaction between lithospheric plates.