Phytoplankton species composition and abundance in the Lembeh Strait waters was studied in four cruises of April 2013, May 2014, June 2012 and October 2015, during the period of monsoon transition time of SE monsoon. With data obtained the seasonal alternations of phytoplankton community structures and its driving factors were discussed. A total of 416 taxa belonging to 5 classes of phytoplankton were recorded in the four month surveys. Phytoplankton density was averaged 2 348 cell/L and diatoms and dinoflagellates had the most diversified species. Cyanobacterium was characterized by its low species numbers but high abundance in the waters of Lembeh Strait. Total phytoplankton abundance occurred low in April and October in the monsoon transition period and it raised high in May and June during the SE monsoon. Frequently occurred species were pelagic diatoms in addition to cyanobacterium Trichodesmium. Abundance and diversity of phytoplankton significantly differed seasonally. The diatoms Thalassionema and Pseudo-nitzschia, and cyanobacterium Trichodesmium contributed most to the community dissimilarities. Due to potentially higher nutrient supply in the south of Lembeh Strait, diatoms and dinoflagellates showed higher densities in the south than in the north of the strait. Though, cyanobacterium preferred distributing much evenly in all waters, it had higher density in the southern Lembeh Strait. Total phytoplankton abundance is quite low compared with the Jakarta Bay and some bays in China. Analysis showed that nutrients from upwelling forced by SE monsoon are the key factor varying the monthly phytoplankton abundances. Due to its primitive nature state, Lembeh water can be an ideal location for the study of pelagic ecosystem under merely the influence of macro environment changes with lower background noise from human activities.

Two field observations were conducted around the Lembeh Strait in September 2015 and 2016, respectively. Evidences indicate that seawater around the Lembeh Strait is consisted of North Pacific Tropical Water (NPTW), North Pacific Intermediate Water (NPIW), North Pacific Tropical Intermediate Water (NPTIW) and Antarctic Intermediate Water (AAIW). Around the Lembeh Strait, there exist some north-south differences in terms of water mass properties. NPTIW is only found in the southern Lembeh Strait. Water mass with the salinity of 34.6 is only detected at 200–240 m between NPTW and NPTIW in the southern Lembeh Strait, and results from the process of mixing between the saltier water transported from the South Pacific Ocean and the lighter water from the North Pacific Ocean and Sulawesi Sea. According to the analysis on mixing layer depth, it is indicated that there exists an onshore surface current in the northern Lembeh Strait and the surface current in the Lembeh Strait is southward. These dramatic differences of water masses demonstrate that the less water exchange has been occurred between the north and south of Lembeh Strait. In 2015, the positive wind stress curl covering the northern Lembeh Strait induces the shoaling of thermocline and deepening of NPIW, which show that the north-south difference of air-sea system is possible of inducing north-south differences of seawater properties.

Fish species composition and spatio-temporal variability of the community were studied in a tropical seagrass meadow located in a lagoon in the eastern part of North Sulawesi. The diversity of fish community in the seagrass meadows was relatively high, with the Shannon-Wiener index ranging from 1.57 to 3.69. The family Apogonidae was the most dominant in abundance (8.27 ind./(100 m²)) and biomass (28.49 g/(100 m²)). At the species level, Apogon lateralis and Sphaeramia orbicularis were the most dominant species in abundance and biomass, respectively. For spatial distribution on species, the end, middle and mouth of the lagoon clustered together as a whole, which may be due to the substrate types found in those zones. The fish species, fish abundance and fish biomass were greater in the dry and wet seasons than in the transition season, which is explained by the strong monsoon, which provides a more suitable environment and food for the fish. The maximum length of 93.10% of the captured species was less than their length at maturity, indicating that seagrass meadows are nursery habitats for many fishes. Therefore, protection of the seagrass meadows is essential for fisheries and sustainable resource utilization.

The community structure of zooplankton has been conducted in the Lembeh Strait in Bitung and Wori Beach in Manado, North Sulawesi in October 2015. Sampling of this research was conducted in 22 sampling sites along the strait. Zooplankton samples were collected from 22 stations, by NORPAC 300 μm net that was vertically hauled from maximum 10 m depth up to the surface water. The samples were poured into the bottle with formalin of 4% as preservative. The results showed that there were 43 taxa of zooplankton. The abundance of zooplankton was between 21.216–4 193.776 ind./m³. The dominant taxa were copepod, especially Calanoida. The composition of zooplankton was relatively similar in all stations. We showed the abundance, dominance, composition and distribution of zooplankton at this research. More extensive studies concerning zooplankton is required to understand zooplankton biodiversity as a whole especially on the geographical and spatial distribution to describe population and community dynamic in the Lembeh Strait and Wori Beach.

Three specimens of the serranid fish (Serranidae), Plectranthias kamii Randall, 1980 were collected from fish market, Bitung, North Sulawesi on May and June 2010. Some morphological characters P. kamii is closely related to P. sheni, P. megalophthalmus, P. retrofasciatus, P. rubrifasciatus, P. knappi, P. helenae, P. pelicieri, P. jothyi, P. retrofasciatus and P. randalli in sharing of body width, upper jaw length, pelvic spine length and orbit diameter. Meristic count characters of P. kamii differ from P. sheni, P. pilicieri, P. megalophthalmus, P. retrofasciatus and P. rubrifasciatus in having more numerous dorsal spine (18 vs. 15–17) and below lateral line (33–34 vs. 29–33) and differ from P. megalophthalmus and P. rubrifasciatus in having more numerous pored scales in lateral line (13 vs. 14–15) and shorter of anal spine. The present anthiine fish collected from Bitung, Indonesia was described as new record and bringing the total number of species of this genus known in Indonesia to seven.

Due to the elevated atmospheric carbon dioxide, ocean acidification (OA) has recently emerged as a research theme in marine biology due to an expected deleterious effect of altered seawater chemistry on calcification. A system simulating future OA scenario is crucial for OA-related studies. Here, we designed an OA-simulated system (OASys) with three solenoid-controlled CO₂ gas channels. The OASys can adjust the pH of the seawater by bubbling CO₂ gas into seawaters via feedback systems. The OASys is very simple in structure with an integrated design and is new-user friendly with the instruction. Moreover, the OASys can monitor and record real-time pH values and can maintain pH levels within 0.02 pH unit. In a 15-d experiment, the OASys was applied to simulate OA in which the expected target pH values were 8.00, 7.80 and 7.60 to study the calcifying response of Galaxea fascicularis. The results showed daily mean seawater pH values held at pH 8.00±0.01, 7.80±0.01 and 7.61±0.01 over 15 d. Correspondingly, the coral calcification of G. fascicularis gradually decreased with reduced pH.

Anthropogenic impacts and natural disturbances have been intense recently in the global scale, affecting the composition of coral reef benthic communities from coral to algal dominated reefs. However, this condition does not always occur considering corals are able to recover when the stressors falter. This study aims to investigate the change in coral reef benthic communities and the relationship among benthic categories. The study was carried out in 2014 and 2016 at five sites, three sites in the Lembeh Strait and two sites in Likupang, North Sulawesi Province. Underwater Photo Transect (UPT) was used at depth of around 4–6 m in slope areas. The result indicated that the benthic communities were slightly changing: the percent covers of hard corals, sponges, soft corals, macroalgae and substrate categories were not significantly different between the years but category of others, particularly seasonally growing hydroid, increased significantly, occupying the available substrates and overtopping other benthos surrounding. The study also found that there was a significant relationship between the change in benthic gradient and the number of hard coral colonies: when the composition becomes less complex, the number of colony declines. In contrast, the hard coral diversity remained unchanged, suggesting the coral reefs apparently have an ecological resilience (sustainable species diversity) against the change although ecological complexity declines. In addition, the hard coral cover was significantly correlated with soft coral and sponge covers, which did not change significantly among the years. In general, the coral reefs in North Sulawesi might experience a temporary blip due to the increasing percent cover of others, and be predicted to recover as there was no indication of soft corals and sponges to increase significantly. However, it is necessary to investigate the dynamic of benthic communities in different depth gradients to gain a comprehensive understanding as the communities respond differently to the light intensity.

Mangrove ecosystems are sites with high biodiversity of benthic fauna, and fiddler crabs (genus Uca) are common benthic fauna in mangroves. The North Sulawesi in Indonesia has a good condition of mangrove while the information of the fiddler crabs is still limited. Manual samplings were conducted in wet, dry and transient seasons at a mangrove in Kema, North Sulawesi to investigate the species composition, density and distribution pattern of fiddler crabs. A total of 168 individuals, subjected to eight species of genus Uca crabs were collected at the mangrove, with U. triangularis having the highest abundance and U. annulipes having the lowest abundance. The densities of fiddle crabs were 27.56 ind./m², 32.89 ind./m² and 14.22 ind./m² at the seaward, middle and landward zones, respectively, and the density was higher in dry and wet seasons than in transient season.

Oil droplet size distribution (ODSD) plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study ODSD under different experimental conditions in a laboratory water tank observed by two high-speed cameras in March and April 2017. The correlation formulas Oh=10.2Re^–1 and Oh=39.2Re^–1 (Re represents Reynolds number and Oh represents Ohnesorge number) were established to distinguish the boundaries of the three instability regimes in dimensionless space based on the experimental results. The oil droplet sizes from the experimental data showed an excellent match to the Rosin–Rammler distribution function with determination coefficients ranging from 0.86 to 1.00 for Lvda 10-1 oil. This paper also explored the influence factors on and change rules of oil droplet size. The volume median diameter d₅₀ decreased steadily with increasing jet velocity, and a sharp decrease occurred in the laminar-breakup regime. At Weber numbers (We) <100, the orifice diameter and oil viscosity appeared to have a large influence on the mean droplet diameter. At 100<We<1 000, the oil viscosity appeared to have a larger influence on the relative mean droplet diameter.

In the identifying process of an oil spill accident, manual integral and artificial visual comparison are commonly used at present to determine the oil spill sources, these methods are time-consuming and easily affected by human factors. Therefore, it is difficult to achieve the purpose of rapid identification of an oil spill accident. In this paper, an intelligent method of automatic recognition, integration and calculation of diagnostic ratio of Gas Chromatography-Mass Spectrometer (GC/MS) spectrum are established. Firstly, four hundreds of samples collected around the world were analyzed using a standard method and Retention time locking technology (RTL) was applied to reduce the change of retention time of GC/MS spectrum. Secondly, the automatic identification, integration of n-alkanes, biomarker compounds, polycyclic aromatic hydrocarbons and calculation of the diagnostic ratios were realized by MATLAB software. Finally, a database of oil fingerprints were established and applied successfully in a spill oil accident. Based on the new method and database, we could acquire the diagnostic ratios of an oil sample and find out the suspected oil within a few minutes. This method and database can improve the efficiency in spilled oil identification.