Flores Sea Research Articles

The Fishing Ground of Large Pelagic Fish during the Southeast Monsoon in Indonesian Fisheries Management Area-713

Large pelagic fish (LPF hereafter) is an important group of fishes targeted by local fishermen in the Indonesian Fisheries Management Area-713 (IFMA-713). This IFMA includes the Makassar Strait, Flores Sea, Bali Sea, and Gulf of Bone. The objective of this study was to identify the preferred oceanographic conditions based on LPF fishing grounds in the study area. The experimental fishing was conducted from April to September 2018 by using local commercial fisheries (pole and line and purse seine). The fishing base of pole and line vessels operating in the Gulf of Bone was at Murante fish landing site, Luwu Regency, South Sulawesi. On the other hand, the fishing base of purse seine vessels operating in the Makassar Strait was at Siddo fish landing site, Barru Regency, also in South Sulawesi. Oceanographic factors such as sea surface temperature (SST), sea surface chlorophyll-a (SSC) concentration, and depth were derived from satellite data. The LPF fishing grounds were analysed and visualize using Geographic Information System (GIS) techniques. Based on the results, LPF distributions tended to be the highest in specific oceanographic conditions, including SST of 30.0 - 31.0 °C and SSC of 0.20 - 0.30 mg.m−3. They were mostly found in nearshore and offshore areas (maximum depth of about 2,000 m). The selected oceanographic factors played an important role in explaining the LPF fishing grounds. This information could be used for spatial prediction of potential LPF fishing zones in relation to the fish distribution and abundance during the Southeast monsoon in the IFMA-713.

Two-phase structure of tropical hydroclimate during Heinrich Stadial 1 and its global implications

Previous studies have proposed that the two-phase structure of Heinrich Stadial 1 (HS1) is a ubiquitous feature. However, few studies have focused on the internal structure of HS1 over a tropical domain; thus, the interhemispheric ocean-atmosphere teleconnections during HS1 are poorly defined. Here, we present high-resolution sedimentological, geochemical, and palaeoceanographic records from the core CG2 in the southern South China Sea (SCS), off the northern Sunda Shelf. The core continuously spans 9.0–22.0 ky BP. The records suggest two episodes of increased monsoon rainfall during the pre-HS1 (∼19.0–18.0 ky BP) and in the early HS1 (17.5–16.1 ky BP), along with a weaker monsoon rainfall during the late HS1 (16.1–14.7 ky BP). In contrast, a lower precipitation over the Flores Sea occurred during the early HS1, off the southern Sunda Shelf, followed by an enhanced precipitation runoff during the late HS1 (Muller et al., 2012). Notably, these two different precipitation phases characterise a southward Intertropical Convergence Zone (ITCZ) shift over the Sunda Shelf during HS1. These changes are also consistent with other monsoon records, as well as other available data from the tropical to high latitudes of both hemispheres, supporting the global scope of the twofold HS1. We propose that the two episodes of intense monsoon rainfall over the northern Sunda Shelf during the pre-HS1 and the early HS1 observed in our study are closely linked to two different melting events associated with European ice sheet (EIS) retreat. We further propose that the subsequent maximum Atlantic meridional overturning circulation (AMOC) reduction and the migration of the ITCZ to its southernmost position during the late HS1 are tightly connected with the destabilization of the marine-terminating ice-streams of the Laurentide ice sheet (LIS) in the North Atlantic. Tropical positive feedbacks during HS1, in turn, should have played an important role in sustaining the AMOC reduction and Northern Hemisphere (NH) stadial conditions, by continuously lowering the salinity of the low-latitude currents in the Atlantic Ocean. In addition, the tropical ITCZ appears to have been a key bridge in promoting interhemispheric climate connections, by which North Atlantic cooling was rapidly linked to increased Southern Ocean surface westerlies. This, in turn, drove upwelling and CO2 ventilation from the Southern Ocean, and thereby facilitated deglacial warming. Finally, these findings show that tropical climate variation is an important component of deglacial climate changes; understanding how it responds to millennial events like HS1 may help us better understand global teleconnections.

Short-Term Variation of the Surface Flow Pattern South of Lombok Strait Observed from the Himawari-8 Sea Surface Temperature

Spatial and temporal information on oceanic flow is fundamental to oceanography and crucial for marine-related social activities. This study attempts to describe the short-term surface flow variation in the area south of the Lombok Strait in the northern summer using the hourly Himawari-8 sea surface temperature (SST). Although the uncertainty of this temperature is relatively high (about 0.6 ∘ C), it could be used to discuss the flow variation with high spatial resolution because sufficient SST differences are found between the areas north and south of the strait. The maximum cross-correlation (MCC) method is used to estimate the surface velocity. The Himawari-8 SST clearly shows Flores Sea water intruding into the Indian Ocean with the high-SST water forming a warm thermal plume on a tidal cycle. This thermal plume flows southward at a speed of about 2 m / s . The Himawari-8 SST indicates a southward flow from the Lombok Strait to the Indian Ocean, which blocks the South Java Current flowing eastward along the southern coast of Nusa Tenggara. Although the satellite data is limited to the surface, we found it useful for understanding the spatial and temporal variations in the surface flow field.

Interannual variability of Indonesian throughflow in the Flores Sea

The main branch of Indonesian Throughflow (ITF) from Makassar Strait passes through Flores Sea. The variance of ITF transport volume was influenced by climate phenomenon such as El Nino Southern Oscillation (ENSO). This research was conducted to describe the relationship between the ENSO and the ITF transport variability. This relationship was explored using data from INDESO model 2008-2015. The variability of transport volume was analyzied using continous wavelet transform and band-pass analysis. Water circulation was analyzed by summing up the average of water current and sea temperatures. The Flores ITF was a portion of Makassar ITF and Eastern ITF that enter via Lifamatola Passage. The flow in the upper layer was intensified during the west monsoon while in the thermocline layer was intensified during the east monsoon. Flores ITF moved along the northern part of Flores Island and was dominated by zonal velocity component.

Upper circulation in Bone Bay and its relation to biogeochemical distribution: from observation and model

The surrounding waters and the physical mechanisms within the ocean are playing a major role to bring nutrients to Bone Bay, field observation in October 2014 and analysis of numerical modeling were conducted in order to understand the pattern of water circulation, as well as the variability of seawater transport and its impacts to the biogeochemical distribution. The results of the observation show that the distribution of salinity is lower in locations closest to the gulf (Transect A) and higher towards the furthest locations from the gulf (Transect D), followed by the pattern of other parameters (temperature, dissolved oxygen, and chlorophyll-a). This happened due to the low current speed in the Flores Sea during the time of observation hence no water flowed into the gulf which was dominated by freshwater from rivers. It is confirmed by the transport model that shows that seawater is transported strongly to the north from January to March and due to the topography at the mouth of the gulf, the water accumulates and forms an eddy which transports water to the south in April until the next few months. This explains the distribution of phytoplankton and zooplankton inside the gulf from January to March.

Deglacial Warming and Hydroclimate Variability in the Central Indonesian Archipelago

AbstractWe present centennial‐scale records of sea surface temperature and oxygen isotopes from the Celebes Sea, Makassar Strait, Flores Sea, and northwestern Banda Sea, which provide new insights into the variability of Indonesian hydroclimate over the past 25 kyr. Deglacial warming was generally gradual with an amplitude of 3–4 °C. Statistical evaluation of the temperature data suggests that the onset of deglacial sea surface temperatures warming in the tropical Indonesian Sea occurred earlier than the global atmospheric CO2 rise. In contrast to previous terrestrial precipitation records, our ice volume‐corrected δ18O of seawater (δ18Osw) does not support widespread aridity in central Indonesia during the last glacial period. While δ18Osw was substantially enriched during Heinrich Stadial 1 and the Younger Dryas, δ18Osw values were only ~0.2‰ heavier during the Last Glacial Maximum than during the Holocene. Heavier δ18Osw during Heinrich Stadial 1 and the Younger Dryas either reflects a decline in precipitation amount and/or increased δ18O of rainfall in central Indonesia, both likely caused by a southward displacement of the tropical rain belt. Comparison of the Celebes Sea, Makassar Strait, Flores Sea, and Banda Sea records suggests that rainfall isotope and/or amount changes were comparable over Borneo and Sulawesi during the last termination.

Mycale (Oxymycale) klausjanusorum sp. nov. (Porifera: Demospongiae: Poecilosclerida) from Flores Sea deep water, Indonesia.

A new species of the large genus Mycale Gray, 1867 is described, dredged from approximately 300 m depth in the Flores Sea region between the islands of Salayar and Bahuluang, Central Indonesia, during cruises of the Indonesian-Dutch Snellius II Expedition in 1984. Because its megascleres include oxeas the new species is classified as a member of the subgenus Oxymycale Hentschel, 1929, proposed to be named M. (O.) klausjanusorum sp. nov. to honour renowned colleagues Klaus Rützler and Jean ('Janus') Vacelet. It is characterized by an ectosomal skeleton consisting of bouquets of subtylostyle megascleres protruding beyond an ectosomal tangential confused layer of oxeas, which in turn rests on robust choanosomal bundles of mixed oxea and subtylostyle megascleres. The combination of two categories of megascleres, differentiated not only in size but also in morphology, the larger one of which is arranged in ectosomal bouquets, is a unique feature in the genus Mycale. A high diversity of the microscleres and large upper size of the anisochelae (up to 189 µm) are additional features of the new species. The subgenus Oxymycale is reviewed and its status as a monophyletic group of Mycale is discussed.

Foraminifera spatial analysis as bioindicator in Java Sea to Flores Sea

Foraminifera is potential bioindicator to understand the modern and ancient marine environment and have been widely used as bioindicator. Java Sea to Flores Sea are productive area influenced by physical and chemical reactions from nature and human activity, so that their characteristics are important to recognize. The aim of this research is to determine oceanography condition of Java Sea to Flores Sea covers the depth, temperature, thermocline, and upwelling according to foraminifera analysis. The method used were inventory and species analysis from 12 stations along study area. The analysis was conducted based on species and abundance. Foraminifera species which are warm water bioindicators are Globigerinoides rubra and Globigerinoides sacculifera, upwelling bioindicators are Globigerina bulloides and Globorotalia menardii, and shallow thermocline bioindicators are Pulleniatina obliqueloculata and Neogloboquadrina dutertrei. The result show that Java Sea has more benthonic species and abundance because of its shallow depth while Flores Sea has more planktonic species and abundance because of its deep depth and part of open ocean. In Flores Sea the abundance of warm water species bioindicators fall significantly and high abundance of upwelling and shallow thermocline species bioindicators indicates that there are upwelling phenomenon with shallow thermocline, thin mix layer, and high productivity.

ON THE OCCURRENCE OF UPWELLING IN THE SOUTHERN MAKASSAR STRAIT

The possibility of upwelling occuring off the coast of Sulawesi in the Southern Makassar Strait has been discussed by earlier workers (see e.g. Veen 1953, and Wyrtki 1961). Surface salinity data show higher values in June or July along the southwest coast of Sulawesi than the rest area to the west of it. The months June and July coincide with the southeast monsoon in the area. It is believed that the presence of such high salinity could only be due to the process of upwelling. As already mentioned in these works (e.g. by Wyrtki, 1961) during the southeast monsoon, the west-going surface currents coming from the Northern Makassar Strait and the Flores Sea pass the area, and flow into the Java Sea. It is thought that part of the water masses transported by the currents originate from subsurface layer off Makassar coast.

SPATIAL-TEMPORAL DISTRIBUTION OF CHLOROPHYLL-A IN SOUTHERN PART OF THE MAKASSAR STRAIT

Surface chlorophyll-a (Chl-a) distribution have been analyzed with seasonal variation during southeast monsoon in southern part of Makassar Strait and Flores Sea. Satellite data of Landsat-8 is applied to this study to formulate the distribution of chlorophyll concentration during monsoonal wind period. The distribution of chlorophyll concentration was normally peaked condition in August during southeast monsoon. Satellite data showed that a slowdown in the rise of the distribution of chlorophyll in September with a lower concentration than normal is likely due to a weakening the strength of southeast trade winds during June – July – August 2016. Further analysis shows that the southern part of the Makassar strait is likely occurrence of upwelling characterized by increase in surface chlorophyll concentrations were identified as the potential area of fishing ground.

Estimation of Tsunami Inundation and Disaster Mitigation in Bulukumba, Indonesia

The study aims to determine the potential of earthquake that could lead to tsunamis in the Flores Sea. Furthermore, based on the potential of earthquake magnitude, can be known high run-up of tsunami in the southern coastal region of Bulukumba regency. The height run-up of tsunami can show the vulnerability of tsunami impact and eects spatially based on the eect of land function in the southern coastal area of Bulukumba Regency. To plan an eective mitigation scenario in the southern coastal area of Bulukumba Regency can be based on the vulnerability of tsunami impacts and eects. This study uses secondary data consisting of three data. The condition of land function and the density of community infrastructure is obtained basedon RTRW data of Bulukumba District and Satellite Bing Maps image data; historical data of earthquake events inthe Flores Sea from 1927 to 2016 from the USGS site, and BMKG; as well as topographic data. Field check activityon land function condition is done as a form of conformity of secondary data. The results showed that the potential of seismicity in the Flores Sea is high, with magnitude (M 7 SR) potentially causing tsunamis around it, not least Bulukumba Regency, South Sulawesi Province, Indonesia. The area of tsunami inundation in Bulukumba Regency is 13.617 km2. The coastal area of Ujungbulu sub-district is a dense residential area that has the highest risk to the tsunami with an estimated 3,331 km2 inundation. Land cover in Bontotiro sub-district dominated by vegetation with kerapatandengan interval distance of more than 3 m is seen able to reduce the tsunami with a height of 17 m and 25 m. Tsunami disaster mitigation scenario in Bulukumba regency is to make coastal area as conservation area of coastal forest (mangrove plant) that function as green belt of tsunamiwave holder.

Upwelling Dynamic Based on Satellite and INDESO Data in the Flores Sea

Upwelling phenomenon is crucial to be forecasted, mainly concerning the information of potential fishery areas. Utilization of calibrated model for recorded upwelling such as INDESO gives benefit for historical result up to the present time. The aim of this study is to estimate areas and seasons of upwelling occurrences in the Flores Sea using data assimilation of satellite and modeling result. This study uses sea surface temperature, chlorophyll-a data from level 3 of MODIS image and sea surface height from satellite Jason-2 monthly for three years (2014-2016) and INDESO model data for sea surface temperature, sea surface height, and chlorophyll-a daily for three years (2014-2016). The upwelling is indicated by declining of sea surface temperature, sea surface height and increasing of chlorophyll-a. Verification is conducted by comparing the model result with recorded MODIS satellite image. The result shows that the area of southern Makassar Strait having occurrences of upwelling phenomenon every year starting in June, extended to July and August. The strongest upwelling occurred in 2015 covering more or less the area of 23,000 km2. The relation of monthly data of satellite has significantly correlated with daily data of INDESO model

APLIKASI TEKNOLOGI PENGOLAHAN AIR ASIN DESA TARUPA KECAMATAN TAKA BONERATE KABUPATEN SELAYAR

Takabonerate is one of the 23 regencies in South Sulawesi where it is locates at the southern parth of South Sulawesi Province and it is surrounded by flores sea. As maritime regency, its mainland is 1,188.28 km2 (5.23%) and the sea is approximately 21,138.41 km2 (94.68%). It has 126 islands wich consist of small and big islands. Tarupa village’s a subdistrict located in a tidy and peat area. The community living in tarupa use surface water of river as the main clean water resource. The surface water is influenced by the tide of sea water. The surface water taste is very salty (TDS12000ppm). The use of rain water as the second alternative is very limited, i.e it is only in rainy season. To deal with the chronic problem, such as the lack of clean water supply, it needs an appropriate water treatment technology. The suitable water treatment system is a combination of conventional and advanced technology. Desalination, such as Reverse Osmosis must be involved to reduce salinity of the raw water. A complete process includes the pretreatment and advance treatment. The pretreatment are oxidation and some common filtrations. The advance treatment is a molecular filtration using a membran which the principal is reverse osmosis pressure. If the pilot water treatment plant is avalaible in Tarupa in Takabonerate, the clean water supply will not be a serious problem. Generally, it can also play an important role to increase the social level of community in South Sulawesi.. Kata Kunci : Teknologi, pengolahan, air asin, reverse osmosis, air minum.

CHARACTERISTICS AND VARIABILITY OF THE FLORES ITF AND ITS COHERENCE WITH THE SOUTH JAVA COASTAL CURRENT

Characteristics and transport variability of the Indonesian Throughflow (ITF) in the western Flores Sea (FS) and its coherency with the South Java Coastal Current (SJCC) fluctuation are investigated using validated ocean general circulation model output (2008-2014) from the INDESO configuration. The results show that near-surface circulation in the study area is characterized by two distinct regimes: strong southwestward ITF flow and quasi-transient anti-cyclonic eddies. Vertical dimension of ITF crossing 7.5°S is about 112 km width, 250 m depth, and high velocity core at thermocline >0.3 m/s. Transport volume estimates along this latitude is -4.95 Sv (southward). Bifurcation of ITF flow appears north offshore Lombok Island where -2.92 Sv flowing into Lombok Strait and the rest flowing eastward into FS. Meanwhile, vertical dimension of SJCC crossing 114°E is about 89 km width, 120 m depth, and high velocity core at sub-surface >0.35 m/s. Mean transport of SJCC is +2.65 Sv. Coherency between Flores ITF and SJCC transport variability on intra-seasonal scales is significantly high, e.g., on 30 day period (coher=0.92) and phase-lags of 0.6-day with SJCC leading to Flores ITF. This result confirmed previous studies, related to intrusion of coastally trapped Kelvin waves into Flores Sea via Lombok Strait. Keywords: Indonesian Throughflow, western Flores Sea, South Java Coastal Current

Present status of 137Cs in seawaters of the Lombok Strait and the Flores Sea at the Indonesia Through Flow (ITF) following the Fukushima accident

Due to thermocline and surface water from the western equatorial Pacific Ocean, which are transported to the Indian Ocean, Indonesian marine waters play an important role in the global ocean circulation. The objective of this study was to assess the spatial distribution of 137Cs in the Lombok Strait as part of a national monitoring program concerning the possible impacts of radionuclides released as a result of the Fukushima accident. Sampling was conducted in the Flores sea and Lombok Strait on 15 to 24 November 2013. Measurements for the Lombok strait showed that 137Cs concentrations at surface layer, thermocline layer and 1000m depth were 0.27Bqm−3; 0.42Bqm−3 and <MDA (0.01Bqm−3), respectively. The water concentration of 134Cs at all monitoring stations were under MDA (0.01Bqm−3). The results the study indicate that the radiocesium input was from global fallout.

Gymnocranius obesus, a new large-eye seabream from the Coral Triangle

Two previously recorded new species of the large-eye seabream genus Gymnocranius (Gymnocranius sp. D and Gymnocranius sp. E) remain undescribed. Here we describe Gymnocranius sp. E as Gymnocranius obesus sp. nov. This new species is morphologically distinct from all other known species under Gymnocranius by the following combination of characters: relatively deep body, with ratio of standard length to body depth 2.2–2.4; protruding large eye, with eye diameter about equal to or slightly larger than inter-orbital width; caudal fin moderately forked; no blue spots or wavy blue lines on cheek and snout in adults; fourth transversal dark bar on flank running from the sixth spine of the dorsal fin to the origin of the anal fin; anal, caudal and dorsal fins drab with yellowish to yellow margins. Gymnocranius obesus sp. nov. is distinct from G. griseus, with which it has been previously confused by a relatively larger head, scales above lateral line without dark basal patch, and a smaller number of front scales on the dorsal side of the head. Gymnocranius obesus sp. nov. is genetically distinct from its closest known relative, Gymnocranius sp. D by 104 diagnostic nucleotide characters, which translates into a 9.6% sequence divergence at the mitochondrial cytochrome b gene. Gymnocranius obesus sp. nov. reaches a length of at least 295mm. Its distribution, from the Ryukyu Islands to Bali, including Taiwan and the Flores Sea, mostly coincides with the western half of the Coral Triangle.

First record of blurred smooth lanternshark, Etmopterus bigelowi from Indonesia

The blurred smooth lanternshark, Etmopterus bigelowi Shirai and Tachikawa, 1993 was recorded for the first time from Indonesian waters based on two specimens collected from a deepwater shark fishery operated in the Flores Sea, eastern Indonesia. This is also the second confirmed record of Etmopterus species from this country.

Karakteristik Morfologi Dasar Laut dan Hubungannya dengan Ketebalan Sedimen dan Kecepatan Arus di Selat Flores, Selat Lamakera, Selat Boling, dan Selat Alor

&lt;strong&gt;Characteristics of Sea Bottom Morphology and Their Relationships with Sediment Thickness and Current Speed in the Straits of Flores, Lamakera, Boling, and Alor. &lt;/strong&gt; The morphology of the seabed of a strait may affect sedimentary deposits and current speeds in the strait. The Straits of Flores, Lamakera, Boling, and Alor connect the Flores Sea and Savu Sea in East Nusa Tenggara Province. This study aimed to determine the characteristics of seabed morphology and its relation to sediment thickness and current speed in the straits. Single Beam Echosounder and SubBottom Profiler were used to measure depth of waters and subsurface. The results showed that the seabed of the Flores Strait was basin-shaped at a depth of about 250 m, while the seabed at the connections between the Straits of Boling, Lamakera, and Alor was a ridge leading to the Flores Sea and Savu Sea with depths up to 3,000 m. The thickness of the sedimentary sediments in the Flores Strait reached 50 m, while in the Straits of Boling, Lamakera, and Alor sedimentary deposits were not visible. In the Flores Strait which was characterized by narrow strait, the current speed ranged from 0.3 to 3.8 m/s. The descriptions of subsurface conditions in these straits can be used for navigation of ships that will cross the straits, especially vessels of more than 2,000 tons. The narrow strait morphology causes the mass of water in this region to have a high current speed. Therefore, the sedimentation occurs only in the Flores Strait due to its basin-shaped seabed.

Prediction of Potential Fishing Zones for Skipjack Tuna During the Northwest Monsoon Using Remotely Sensed Satellite Data

One of economically important fish in the Bay of Bone is Skipjack tuna which their distribution and migration are influenced by surrounding environment. This study aims to investigate the relationship between skipjack tuna and their environments, and to predict potential fishing zones (PFZs) for the fish in the Bone Bay-Flores Sea using satellite-based oceanography and catch data. Generalized additive models (GAMs) were used to assess the relationship. A generalized linear model(GLM) constructed from GAMs was used for prediction. Monthly mean sea surface temperature (SST) and chlorophyll-a during the northwest monsoon (December-January) together with catch data were used for the year 2012-2013. We used the GAMs to assess the effect of the environment variables on skipjack tuna CPUE (catch per unit effort). The best GLM was selected to predict skipjack tuna abundance. Results indicated that the highest CPUEs (fish/trip) occurred in areas where SST and chlorophyll-a ranged from 29.5°-31.5°C and 0.15 - 0.25 mg m-3, respectively. The PFZs for skipjack were closely related to the spatial distribution of the optimum oceanographic conditions and these mainly developed in three locations, northern area of Bone Bay in December, in the middle area of the bay (4°-5.5°S and 120.5°-121.5°E) during January and moved to the Flores Sea in February. The movement of skipjack concentration was consistent with the fishery data. This suggests that the dynamics of the optimum oceanographic signatures provided a good indicator for predicting feeding grounds as hotspot areas for skipjack tuna in Bone Bay-Flores Sea during northwest monsoon. Keywords: skipjack tuna, potential fishing zones, satellite based-oceanographic data, Northwest monsoon

Status of [formula omitted] concentrations in sea water at the inlets of the Indonesian Through Flow (ITF)

There is a lack of available data on 137Cs water concentrations at the Indonesian Through Flow (ITF). The data is required for evaluation of the possible impact of the Fukushima accident in Indonesia’s marine environment. 137Cs monitoring at inlets of ITF were conducted in order to address this possible impact. Monitoring was performed by the Baruna Jaya III research vessel during the Sail Morotai campaign of 2012. Surface sea water (0–10 m depth) samples were collected at 7 stations. The AMP (Ammonium molybdophosphate) method was used for separating radiocesium from seawater. The radiocesium were measured by a HPGe detector of gamma spectrometer system. The measured concentrations of 137Cs in the Flores Sea ranged between 0.29–0.30 Bq m−3. At another inlet of the ITF in the Halmahera Sea which the concentration of 137Cs were founded varied between 0.20–0.38 Bq m−3. The water concentrations of 137Cs in the Lifamatola Passage, at the Eastern of Sulawesi, ranged between 0.20–0.30 Bq m−3. There was no detection of 134Cs at any of the monitoring stations. The result showed that the input 137Cs from the Pacific Ocean to Indonesian Seas was not from Fukushima but was characteristic of global fallout in the Pacific Ocean.