Island Waters Research Articles

Vertical and Horizontal Variability of Chlorophyll-a and Its Relationship with Environmental Parameters in the Waters of Sangihe and Talaud Islands, North Sulawesi, Indonesia

The chlorophyll-a is an important biological parameter that could act as a proxy to indicate the abundance of phytoplankton and the primary productivity of an aquatic ecosystem. This paper investigates the vertical and horizontal variability of chlorophyll-a in the waters of Sangihe and Talaud Islands, Indonesia, and its correlation with water environmental parameters. In this study, the distribution of chlorophyll-a, temperature, salinity, and nutrients (NO3 and PO4) from the surface to a depth of 200 m (photic zone) was measured at 29 research stations. The results showed that the distribution of chlorophyll-a in the waters of the Sangihe-Talaud Islands was varied vertically and horizontally. The waters around the Sangihe Islands generally exhibited a higher chlorophyll-a distribution and shallower Deep Chlorophyll Maxima compared to the water around the Talaud Islands. The concentration of chlorophyll-a varied between 0.0017 and 1.2155 mg.m-3, with most of the water column in Sangihe-Talaud considered oligotrophic, although some stations or depths were mesotrophic or slightly eutrophic. The maximum chlorophyll-a concentration was found in the sub-surface layer at depths between 46 and 101 m. The low N:P ratio (<16) and N:Si ratio (<1) indicate that the water columns of Sangihe-Talaud, up to a depth of 200m, were N-limited. Based on the GAM analysis, chlorophyll-a concentration in Sangihe-Talaud waters was primarily regulated by temperature, salinity, and the N:P ratio, with weak influence from phosphate and the N:Si ratio. The analysis also suggests that primary productivity in Sangihe-Talaud is sensitive to temperature changes, indicating its vulnerability to future warming events.

Isolation and identification of bacterial pathogens causing ice-ice disease in Eucheuma cottonii seaweed at Seira Island Waters, Tanimbar Islands District, Maluku, Indonesia

Abstract. Tuhumury NC, Sahetapy JMF, Matakupan J. 2024. Isolation and identification of bacterial pathogens causing ice-ice disease in Eucheuma cottonii seaweed at Seira Island Waters, Tanimbar Islands District, Maluku, Indonesia. Biodiversitas 25: 964-970. Seaweed cultivation has proven to be beneficial and enhances the well-being of communities. Production of seaweed in the waters of Maluku has increased despite facing the problem of ice-ice disease. Therefore, this research aimed to isolate and identify bacteria on the Eucheuma cottonii seaweed species affected by ice-ice disease in the waters of Seira Island, Tanimbar Islands District, Maluku. It was conducted in August 2023 at three observation stations, and water quality samples were collected in situ at all three stations, including temperature, salinity, pH, dissolved oxygen (DO), and turbidity. Furthermore, bacterial isolation and identification were carried out at the Laboratory of Marine Aquaculture, Ambon. Bacteria isolation and purification were performed on TCBS media using the streak plate technique, while identification used the API 20E test. The results showed that water quality parameters supported seaweed growth. Four bacteria that caused ice-ice disease in the waters of Seira were identified as Vibrio alginolyticus, Vibrio fluvalis, Vibrio cholerae, and Aeromonas caviae. Moreover, all four bacteria found were gram-negative and pathogenic. Bacteria belonging to the genera Vibrio and Aeromonas have been proven to cause infections in marine organisms, including seaweed. In conclusion, four types of bacteria were identified in seaweed affected by ice-ice disease.

Noncontact Automatic Water-Level Assessment and Prediction in an Urban Water Stream Channel of a Volcanic Island Using Deep Learning

Traditional methods for water-level measurement usually employ permanent structures, such as a scale built into the water system, which is costly and laborious and can wash away with water. This research proposes a low-cost, automatic water-level estimator that can appraise the level without disturbing water flow or affecting the environment. The estimator was developed for urban areas of a volcanic island water channel, using machine learning to evaluate images captured by a low-cost remote monitoring system. For this purpose, images from over one year were collected. For better performance, captured images were processed by converting them to a proposed color space, named HLE, composed of hue, lightness, and edge. Multiple residual neural network architectures were examined. The best-performing model was ResNeXt, which achieved a mean absolute error of 1.14 cm using squeeze and excitation and data augmentation. An explainability analysis was carried out for transparency and a visual explanation. In addition, models were developed to predict water levels. Three models successfully forecasted the subsequent water levels for 10, 60, and 120 min, with mean absolute errors of 1.76 cm, 2.09 cm, and 2.34 cm, respectively. The models could follow slow and fast transitions, leading to a potential flooding risk-assessment mechanism.

Investigation of an Antifouling Compound from Sponge Siphonodictyon coralliphagum

Marine fouling is attaching organisms to objects floating or submerged in seashores, such as ships, docks, and offshore structures. The impact caused is the reduced lifespan of the thing attached to the biofouling. In addition, there was a spread of invasive species. The government and industries in the United States spend over 6.5 million dollars annually on their budget to overcome this problem. So far, the prevention of marine biofouling is using antifouling paint on ships and submerged structures. One of them is organotin tributyltin (TBT) proven effective for preventing fouling; however, it is not environmentally friendly. Sponge Siphonodictyon coralliphagum growing in Salibabu Island waters, Talaud Islands, with previously shown activities against prokaryotes, was collected and extracted by maceration using ethanol as a solvent. The extract was then added to the base paint with several compositions of 5%, 10%, and 25% applied to the paving block surface. Positive control uses paint with copper additives. The objects are then immersed in the seashore below subtidal depths. The observation was carried out every seven days until day 28. The paving block was observed on day 90 after immersion. Significant results were obtained where macrofouling was only able to grow in negative control and positive control. The extract sponge S. coralliphagum has vigorous antifouling activity against marine biofouling. Furthermore, the extract was fractionated using liquid chromatography and continued by testing their activity against Gram-positive and negative bacteria. Further investigation of NMR spectra from the active fraction to prokaryotic cells shows a cyclic aliphatic compound with several keto-enol functional and methyl aliphatic groups on their chain.

Analisis Aspek Ekobiologi Ikan Kakatua (Scaridae) di Perairan Pulau Tikus Kota Bengkulu

The large potential of marine fisheries owned by the City of Bengkulu can be an economic source for the local community. The fish potential comes from pelagic fish and reef fish. One of the reef fish is the parrot fish (Scaridae). Parrot fish in Bengkulu City are obtained from Tikus Island which are sold on Malabero Beach. The purpose of this study was to analyze the ecobiological aspects of parrot fish (Scaridae) in Tikus Island waters, Bengkulu City. The results of this study are expected to provide information in the form of valid data regarding the ecobiological aspects of parrot fish (Scaridae) in Tikus Island waters, Bengkulu City. In this study, data collection to look at ecological or environmental aspects was carried out by direct observation in the field at 3 stations, while biological aspects, namely food habits (amount/type of food), were observed through a microscope in the laboratory. The results of water parameter measurements, namely the temperature at station 1 ranged from 28-29 0C, station 2 is 29 0C, station 3 is 29 0C. pH value at station 1 is 7.0-7.3, station 2 is 7.3-7.7, station 3 is 6.5-7.1. Salinity values at station 1 is 31 ppt, station 2 is 30 ppt and station 3 is 31 ppt. Dissolved oxygen (DO) at station 1 ranged from 5.6-6.3 mg/L, station 2 5.2-5.3 mg/L and station 3 5.6-6.1 mg/L. The water brightness at station 1 is 9.2 m, at station 2 is 6.6 m and at station 3 is 7.4 m. Current velocity at station 1 ranges from 0.09-0.11 m/s, station 2 are 0.08-0.14 m/s, and at station 3 ranges from 0.05-0.09 m/s. Water depth at station 1 is 9.2 m, station 2 is 7.3 and station 3 is 7.5 m. These results indicate that Tikus Island water have a good environment for survival and habitat of parrot fish (Scaridae) or other marine biota. Furthermore, the biological aspects studied are food habits. Based on the identification results, 4 groups of food types were found in the parrot fish stomach, namely phytoplankton, zooplankton, sand coral, and were not identified. The percentage of food groups found from phytoplankton, zooplankton, sand coral, and not identified were 53%, 3%, 15%, 29%, respectively.

Reef fish community structure in the waters of small islands Central Bangka Regency

This study aimed to analyze the community structure of reef fish in the small island waters of Central Bangka. The research was conducted in March 2022 in the waters of Bebuar Island, Ketugar Island, Ketawai Island, and Gusung Asam Central Bangka Regency, Bangka Belitung Islands Province. The coral reef survey method uses purposive sampling and the coral reef fish visual census with data analysis of abundance, diversity index, uniformity, and dominance. In-site water quality measurements included six parameters: temperature, salinity, current, brightness, depth, and pH. The results showed that coral reef cover from 44.60 - 87.00% with the medium to very good category. The abundance of reef fish from 1 to 3 individuals/m2 was dominated by 18 species of the Pomacentridae family. The reef fish diversity index ranged from 2.47 to 2.90, including the medium category. The uniformity index value ranged from 0.79 - 0.94, including the high category, indicating that the species found were evenly distributed across all stations. The dominance index value ranges from 0.07 to 0.15, including low, where no species dominates significantly and the fish are evenly distributed. Temperature, brightness, pH, and salinity are factors that support the growth of coral and reef fish. A water current speed of 0.05 – 0.20 m/s is quite helpful in cleaning coral reefs from mud and can supply oxygen. Water conditions were categorized as good and fulfilled the seawater quality standards.

Integration of Different Storage Technologies towards Sustainable Development—A Case Study in a Greek Island

The necessity for transitioning to renewable energy sources and the intermittent nature of the natural variables lead to the integration of storage units into these projects. In this research paper, wind turbines and solar modules are combined with pumped hydro storage, batteries, and green hydrogen. Energy management strategies are described for five different scenarios of hybrid renewable energy systems, based on single or hybrid storage technologies. The motivation is driven by grid stability issues and the limited access to fresh water in the Greek islands. A RES-based desalination unit is introduced into the hybrid system for access to low-cost fresh water. The comparison of single and hybrid storage methods, the exploitation of seawater for the simultaneous fulfillment of water for domestic and agricultural purposes, and the evaluation of different energy, economic, and environmental indices are the innovative aspects of this research work. The results show that pumped hydro storage systems can cover the energy and water demand at the minimum possible price, 0.215 EUR/kWh and 1.257 EUR/m3, while hybrid storage technologies provide better results in the loss of load probability, payback period and CO2 emissions. For the pumped hydro–hydrogen hybrid storage system, these values are 21.40%, 10.87 years, and 2297 tn/year, respectively.

Soil Erosion Characteristics in Tropical Island Watersheds Based on CSLE Model: Discussion of Driving Mechanisms

Previous research has primarily focused on soil erosion issues in arid and semi-arid regions, with a limited understanding of soil erosion mechanisms in tropical areas. Additionally, there is a lack of a holistic perspective to determine the spatial attribution of soil erosion. The conversion of tropical rainforests into economically driven plantations, like rubber and pulpwood, has resulted in distinct soil erosion characteristics in specific regions. To enhance our knowledge of soil erosion patterns and mechanisms in tropical regions, it is necessary to examine soil erosion in the three major watersheds of Hainan Island from 1991 to 2021, which encompass significant geographical features such as tropical island water sources and tropical rainforest national parks. The study employed the China Soil Loss Equation (CSLE) model, slope trend analysis, Pearson correlation analysis, land-use transfer matrix, and spatial attribution analysis to examine soil erosion under different scenarios. The research results indicate that scenarios driven by the combination of natural and human factors have the greatest impact on soil erosion changes in the entire study area. Co-driven increases affected 53.56% of the area, while co-driven decreases affected 21.74%. The 31-year soil erosion showed an overall increasing trend. Human factors were identified as the primary drivers of increased soil erosion in the Nandu River basin, while a combination of climate and anthropogenic factors influenced the decrease in soil erosion. In the Changhua River basin, climate and human activities contributed to the soil erosion increase, while human activities primarily caused the decrease in soil erosion. In the Wanquan River basin, climate intensified soil erosion, whereas human activities mitigated it. This study underscores the significant combined impact of human activities and natural factors on soil erosion in tropical regions. It emphasizes the importance of considering human-induced factors when implementing soil erosion control measures in tropical regions.

Review of amphipods of the family Pleustidae Buchholz, 1874 (Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). III. Subfamily Pleustoidinae Bousfield & Hendrycks, 1994.

The taxonomic analysis of subfamily Pleustoidinae Bousfield & Hendrycks, 1994 is performed. A review of subfamily Pleustoidinae from the shelf of Sakhalin Island and adjacent water area based on all literature and own data is provided. The diagnoses of the subfamily Pleustoidinae and the genus Pleustoides Gurjanova, 1972 have been clarified. Based on new material, the new species Pleustoides tridens sp. nov. is described from the shelf of Sakhalin Island. The species P. ochoticus Gurjanova, 1972 is re-described and its status is clarified. A key to the amphipod of the genus Pleustoides is given.

Identifikasi Kesesuaian Ekologi Permukiman Kampung Air Pulau Kemaro Sebagai Sumber Belajar Geomorfologi Fluvial

The objective of this study is to identify the ecological attributes of the settlements in Kemaro Island Water Village as well as assess their appropriateness as educational resources for geography course material on the topic of fluvial geomorphology in class X, SMA N 5, Palembang. The research employed a descriptive-qualitative approach, utilizing various methods for data collection such as interviews, observation, and documentation. The findings of the study indicate that Kemaro Island is a geographical feature characterized by its location as a bar or sediment situated within the central area of a channel or river flow. Kemaro Island exhibits ecological characteristics in the form of a distinctive Water Village, where individuals reside along the Musi riverbank. The primary occupations of the local community residing on Kemaro Island encompass fishing, diving, boat operation, and agricultural pursuits. The agricultural practitioners residing on Kemaro Island employ a method of rice cultivation that capitalizes on the tidal nature of the nearby river water. Kemaro Island exhibits considerable potential for utilization as a tourism destination. The water landscape of Kemaro Island possesses ecological characteristics that can serve as a valuable educational resource for studying fluvial geomorphology within an environmental context. Hence, it is anticipated that social studies Geography teachers could use the Kemaro Island Kampung Air area as an educational resource for social studies Geography, with the aim of enhancing students' understanding of the local environment

The dynamics of arabesque greenling fishery off south Kuril Islands

The purpose of this work was to characterize the biological and commercial indicators of arabesque greenling in the Kunashir Strait during 1998–2022.The basic material for the article was the data collected during the net fishery of arabesque greenling by the fleet of small-tonnage vessels of the Japanese fishing cooperative in the city of Rausu in the eastern (Russian) zone of the Kunashir Strait.Results: It is shown that the stock resources of arabesque greenling in the waters of the southern Kuril Islands have been declining during for a long period of time. Despite a short-term growth of catch per effort in 2018–2021, in 2022 there was again a decrease of fishery indicators. The negative trend of catch per effort is directly associated with the features of dynamics of arabesque greenling resources distributed in Kunashir Strait and in the Sea of Okhotsk waters of Hokkaido.Practical significance: The new information makes it possible to determine the current trends in total biomass changing for commercial fish and to clarify the fishery capabilities of the area in the nearest future.

Condition of Coral Reefs and Abundance of Coral Fishes of the Chaetodontidae Family in the Waters of Sironjong Gadang Island, Pesisir Selatan District, West Sumatra Province

Sironjong Gadang Island is one of the islands in the Mandeh Tourism area in Pesisir Selatan Regency, West Sumatra, Indonesia. One of the ecosystems affected by tourism activities is coral reefs. Monitoring the coral reefs' condition and the abundance of coral fish in the Chaetdontidae family is carried out to find out this. This research uses survey research methods. The temperature measurement results obtained an average of 30.2oC, current speed measurements received an average of 0.12 m/s, salinity measurements obtained an average of 30 ppt, and brightness measurements show that the brightness of these waters is 9 m. Tide measurements in the waters of Sironjong Gadang Island, carried out on March 7–8, 2023, are double daily tides (semi diurnal tide). Then, the results from the coral reef cover of Sironjong Gadang Island waters obtained a percentage ranging from 2.34 - 12.83%, with an average rate of live coral reef cover of 5.96%, which is included in the poor category. Furthermore, the results at each research station in the waters of Sironjong Gadang Island showed that 54 coralfish individuals were found, with the number of coralfish at each depth ranging from 4 - 10 individuals. The most common types of coral fish are species. Acuminate had 18 individuals; the fewest types of coral fish found were Chaetodon trifasciatus and C. tristichous, each numbering two individuals. There is a solid relationship between live coral reef cover and the abundance of coral fish in the Chaetodontidae family, where live coral reef cover influences the plenty of coral fish by 61.11%, which means that the higher the percentage of live coral cover, the higher the value of coral fish abundance.

Hazard Zoning of Harmful Algal Bloom Disasters in Zhejiang Coastal Waters Using GIS: 1933-2021

The coastal waters of Zhejiang Province in China experience a high incidence of harmful algal blooms (HABs). It is therefore important to carry out hazard zoning to prevent and mitigate these HAB disasters. According to the historical record data of HAB disasters from 1933 to 2021, the frequency, duration, area and algal toxicity of HAB occurrences can be used as evaluation indicators. A method for hazard zoning of HAB disasters and a method for verifying the rationality of the zoning results are proposed. The hazard zoning results of HAB disasters in the coastal waters of Zhejiang from 1933 to 2021 (H1933-2021) show that very-high hazard degree areas of coastal waters of Zhejiang Province were found in Shengshan waters, the eastern waters of Zhujiajian and Nanji Islands' waters. Due to the influence of marine environmental factors, the spatial distribution of hazard degree of HAB disasters is dynamic, so it is recommended that the hazard zoning of HAB disasters be carried out once every five years. The rationality of the zoning results from 2017 to 2021 is verified, showing that the hazard zoning method of HAB disasters proposed in this study has a good rationality and credibility. This study utilized a qualitative approach to visually identify the spatial distribution of hazard degree zoning of HAB disasters in the Zhejiang Province coastal waters over the last 88 years. This has provided useful information to help prevent and mitigate HAB disasters and guide mariculture and coastal tourism planning.

Trophic levels of reef fish community in Badul Island waters after Sunda Strait tsunami

The Sunda Strait tsunami in December 2018 damaged coral reef ecosystems in the Banten coastal area, including Badul Island waters. This condition potentially affects directly to the trophic level of the reef fish community. The purpose of this study was to determine the trophic level of the reef fish community in the waters of Badul Island after a tsunami. The research was conducted in April 2022 at four sampling stations (North, West, South and East) in the Badul Island waters. Reef fish survey using Underwater Visual Census with a 50 m line transect at a depth of 3 – 5 m. Reef fish identified during the study were grouped based on trophic level (carnivore, planktivore, omnivore, herbivore and corallivore). From this research identify 264 individu with 30 species from 17 Family of reef fish. Small waters area around Badul Island made possible reef fish from 4 sampling stations still in same population. The highest abundance of reef fish was found on the west side of Badul Island (128 ind/250 m2). Number species of reef fish founded the highest in East side with 14 species. The highest abundance of reef fish, based on trophic level, was approximately 74 ind/250 m2 of carnivore fish on the western side of the island.

Larval presence and settlement of the American lobster (Homarus americanus) in a changing southern New England estuary

During the late 1980s and early 1990s, the American lobster (Homarus americanus) fishery boomed in southern New England, but starting in the early 2000s lobsters declined in the nearshore regions and the fishery retracted. While previous research has focused on the causes for the declining numbers of adult lobsters in the region as well as lobster settlement, lobster larvae were not sampled in Rhode Island waters. Additionally research was mixed on the origin of lobster larvae found inshore. To examine larval presence in coastal Rhode Island, weekly net tows were conducted at the mouth of Narragansett Bay during summer from 2019 to 2021, and light traps were deployed in 2020 and 2021. Time series segmentation and generalized linear models assessed trends and connections between lobsters caught in trawl surveys, commercial landings data, lobster settlement data, bottom water temperatures, and climate indices. Larval supply to Narragansett Bay is very low and mostly concentrated in the East Passage where ocean water flows into the bay, suggesting that a failure in larval supply from offshore sources is harming local population levels. Time series segmentation and models indicate that declines in lobster settlement followed the decline in adult lobsters in coastal Rhode Island, not Narragansett Bay. Altogether, the data suggest that larval lobster are transported inshore from spawning stock outside the bay. Present circulation patterns combined with the movement of lobsters into deeper waters has made the transport of larvae to Narragansett Bay unlikely.

Monitoring coral reef conditions in the Biorock Pemuteran rehabilitation area during the 2016 coral bleaching

Pemuteran is well-known for its community-based coral reef conservation activities utilising Biorock technology, through the application of low voltage electricity. The main objective of this research is to assess the condition of coral reefs and fish communities within the Biorock area in Pemuteran, Bali. Data collection was implemented in June 2016 at the bleaching event, employing the Point Intercept Transect (PIT) method, and the Underwater Visual Census (UVCs) method. The benthic community composition at both research stations was dominated by dead coral with algae (Biorock Pemuteran 48.9%, Menjangan Island 51%). Both research locations exhibited branching coral and massive coral as the predominant coral lifeforms. Observational findings reveal noticeable differences in the community structure of coral fish between Biorock Pemuteran and Menjangan Island waters. A total of 11,260 individuals covering 120 fish species across 21 families. Higher fish abundance in Menjangan Island (1,326 ± 224 ind/250 m2) compared to Biorock Pemuteran (551 ± 235 ind/250 m2). The condition of coral reefs at both research locations is included in the poor category (0 – 24.9%). The reef fish community in both Biorock Pemuteran and Menjangan Island is in a stable condition with low dominance level and a moderate to high diversity.

Seasonal acoustic presence of marine mammals at the South Orkney Islands, Scotia Sea.

Increased knowledge about marine mammal seasonal distribution and species assemblage from the South Orkney Islands waters is needed for the development of management regulations of the commercial fishery for Antarctic krill (Euphausia superba) in this region. Passive acoustic monitoring (PAM) data were collected during the autumn and winter seasons in two consecutive years (2016, 2017), which represented highly contrasting environmental conditions due to the 2016 El Niño event. We explored differences in seasonal patterns in marine mammal acoustic presence between the two years in context of environmental cues and climate variability. Acoustic signals from five baleen whale species, two pinniped species and odontocete species were detected and separated into guilds. Although species diversity remained stable over time, the ice-avoiding and ice-affiliated species dominated before and after the onset of winter, respectively, and thus demonstrating a shift in guild composition related to season. Herein, we provide novel information about local marine mammal species diversity, community structure and residency times in a krill hotspot. Our study also demonstrates the utility of PAM data and its usefulness in providing new insights into the marine mammal habitat use and responses to environmental conditions, which are essential knowledge for the future development of a sustainable fishery management in a changing ecosystem.

Prevalence of Chinook salmon is higher for southern than for northern resident killer whales in summer hot-spot feeding areas.

Differences in the availability of prey may explain the low numbers of southern resident killer whales and the increase in northern resident killer whales in British Columbia and Washington State. However, in-situ data on the availability of their preferred prey (Chinook salmon, Oncorhynchus tshawytscha) in the core feeding areas used by these two populations of fish-eating killer whales have been lacking to test this hypothesis. We used multi-frequency echosounders (38, 70, 120, and 200 kHz) to estimate densities of adult Chinook (age-4+, > 81 cm) within 16 hot-spot feeding areas used by resident killer whales during summer 2020 in the Salish Sea and North Island Waters. We found Chinook were generally concentrated within 50 m from the bottom in the deep waters, and tended to be absent near the surface in the shallow waters (< 50 m). In general, the densities of Chinook we encountered were highest as the fish entered the Salish Sea (from Swiftsure Bank in the south) and Johnstone Strait (from Queen Charlotte Strait to the north)-and declined as fish migrated eastward along the shoreline of Vancouver Island. Median densities of Chinook for all sampled areas combined were 0.4 ind.·1000 m-2 in northern resident foraging areas, and 0.9 ind.·1000 m-2 in southern resident killer whale areas (p < 0.05, Mann-Whitney U test). Thus, Chinook salmon were twice as prevalent within the hot-spot feeding areas of southern versus northern resident killer whales. This implies that southern resident killer whales have greater access to Chinook salmon compared to northern residents during summer-and that any food shortage southern residents may be encountering is occurring at other times of year, or elsewhere in their range.

Dynamics of Chlorophyll-a Concentration in Ternate Island Waters and Its Effect on Yellowfin Tuna Production

This research was conducted from May to August 2023, with the aim of assessing the distribution of chlorophyll-a concentration and its effect on yellowfin tuna production in Ternate Island waters. The use of experimental fishing methods in collecting research data and data analysis in the form of abundance analysis, exponential regression, cross correlation, and General Aditive Models is expected to answer the research objectives. The results showed that the fluctuation of yellowfin tuna fish catch was similar to the abundance of fish stocks with the highest catch in June (14 229 kg) followed by July (11 142 kg), August (10 764 kg) and May (8 001 kg). The catch of yellowfin tuna fish is spread over a range of chlorophyll-a concentrations between 0.06 mg m-3 to 0.32 mg m-3, with an average monthly chlorophyll-a concentration of 0.22 mg m-3. Chlorophyll-a conditions in Ternate Island waters are quite fluctuating and significantly affect the catch of yellowfin tuna fish with a very strong correlation coefficient of 0.87. The results of General Aditive Models analysis found that the chlorophyll-a concentration value for potential yellowfin tuna fishing areas is &gt; 0.01 mg m-3 with a correlation distance or time leg is in week 15.

Correlation of some water quality parameters and Pb in sediment to gastropod diversity in Ambon Island Waters

The coastal waters of Ambon Island have quite diverse ecosystems that allow for the presence of various organisms, one of which is gastropods. This study aims to analyze the correlation of some water parameters and Pb in sediment to the diversity of gastropods. The research method was carried out by observing the density, water quality parameters, and Pb metal in sediments. Water parameters were measured in situ and analyzed in the laboratory. The distribution of gastropods was analyzed through Principal Component Analysis (PCA). At the same time, the correlation analysis was carried out using the Pearson correlation approach using SPSS v.16. The results showed that the types of gastropods with the highest density in the waters of Ambon Island were Terebralia sulcata, Hebra corticata, and Nerita patula. While the species with the lowest density value were Nassarius olivaceus, Polinices didyma, Lunella cinerea, Conus eburneus, Cypraea isabella, Vexillum plicarium, and Columbella scripta. The Shannon-Wienner Diversity Index ranges from 1.253–2.622, and the diversity index ranges from 0.083-0.207. It was included in the low category caused by the disturbance of water pollution and Pb metal in sediments. Meanwhile, the dominance index ranged from 0.098 to 0.511 indicating species dominance at several observation stations. The waters' physical-chemical parameters strongly correlating with gastropod diversity are DO and Pb, with respective correlation values ​​of r = 0.656 and r = -0.785.