Phytoplankton biodiversity and the inverted paradox

Earth’s aquatic food webs are overwhelmingly supported by planktonic microalgae that live in the sunlit water column where only a minimum number of physical niches are readily identifiable. Despite this paucity of environmental differentiation, these “phytoplankton” populations exhibit a rich biodiversity, an observation not easily reconciled with broadly accepted rules of resource-based competitive exclusion. This conundrum is referred to as the “Paradox of the Plankton”. Consideration of physical distancing between nutrient depletion zones around individual phytoplankton, however, suggests a competition-neutral resource landscape. Application of neutral theory to the sheer number of phytoplankton in physically-mixed water masses yields a prediction of astronomical biodiversity, suggesting the inverted paradox: Why are there so few phytoplankton species? Here, we introduce a trophic constraint on phytoplankton that, when combined with stochastic principals of ecological drift, predicts only modest levels of diversity in an otherwise competition-neutral landscape. Our “trophic exclusion” principle predicts diversity to be independent of population size and yields a species richness across cell-size classes that is consistent with broad oceanographic survey observations.

Numerical Study on Multiple-Blade-Rate Unsteady Propeller Forces for Underwater Vehicles

The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces. Introduction The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.

CHARACTERISTICS OF ANTICYCLONIC EDDY FORMED AT THE PACIFIC COAST OF THE SOUTHERN KURIL ISLANDS IN THE SPRING 1999

Based on the analysis of oceanographic survey materials and sea surface temperature satellite observations, the conditions of formation and characteristics of the anticyclonic eddy located in the region of the South Kuril Islands in the spring of 1999 were studied. It was shown that it separated from the subarctic front as result of its interaction with the Oyashio current stream in the second half of March and ceased to exist in mid-June, which is also confirmed by observations of the concentration of chlorophyll-a. In contrast the eddies formed as a result of meandering of the warm Kuroshio and Tsugaru currents, the eddy core, located at depths of 150–300 m, was characterized by lower values of temperature and salinity (4°–4.6°С and 33.55–33.65 е.п.с.) and low current velocities ( about 10 cm/s). The eddy was rather weakly distinguished in the density field both on horizontal and vertical distributions, as well as according to satellite altimetry data.

Observation and numerical modeling of physical oceanography in the Balikpapan Bay, East Kalimantan: preliminary results

The Indonesian government plans to move the capital city from Jakarta to Penajam Paser Utara (PPU) which is the upstream area of Balikpapan Bay, East Kalimantan. There are several activities in the planned new capital city that potentially affect the condition of land and marine ecosystems, including clearing new land for housing and agriculture as well as expanding mining and petroleum areas. Directly or indirectly, these activities could affect the oceanographic conditions of Balikpapan Bay. For this reason, in order to obtain an up-to-date picture of Balikpapan Bay, an oceanographic survey was conducted in early March 2020. In addition, to support the analysis of marine dynamics in these waters and their predictions in the future, numerical simulations of hydrodynamic modeling were also carried out. Oceanographic observations indicate significant water stratification in the area about 20 km from the mouth of the bay. This result is also well illustrated in the hydrodynamic model numerical simulation, where there is a water loop at the confluence between salt and fresh water masses from two rivers 18-20 km from the mouth of Balikpapan Bay. Keywords:The national capital city of IndonesiaBalikpapan BayPhysical oceanography ObservationCoastal and marine Ecosystem

Evaluation of the Implementation of Information Technology-Based Survey Practice and Hydro-Oceanographic Mapping Practices

Practice Training Survey is an activity in the teaching and learning process for one or more subjects to provide the knowledge and skills of the Hydrographic profession. The purpose of this study was to find out the implementation of the Hydro-Oceanographic Survey and Mapping Practice as a means of developing knowledge and skills for the achievement of education that would use Information Technology facilities. The method used by the kirkpatick model. This model uses four levels, namely: level of satisfaction, level of understanding, behavior change and impact produced. Thus, the implementation of Survey Practice and Mapping Practices become more effective. In order for the Implementation of the Practice Survey and Hydro-Oceanographic Mapping to be able to equip students with behaviors that support the assignment.

A new sponge species of the genus Antho (Demospongiae, Microcionidae) from the Tyrrhenian deep Sea

The use of ROVs has greatly enhanced the possibility of obtaining information on living deep sponge communities (Bertolino et al. 2015). The aim of this work is to describe a new Mediterranean species, Antho (Plocamia) sarasiri sp. nov. (Microcionidae Carter, 1875), characterized by dumbbell spicules making up the framework of the choanosomal skeleton (Van Soest et al. 2013). Samples were collected by ROV during an oceanographic survey in September 2012 on board of the R/V ‘Astrea’ (ISPRA) in “Secca P.ta Fetovaia” (42°43’29.54”N 10° 9’31.64”E) (Elba Island, Tyrrhenian Sea) at 70 m depth. We compared our sample with additional material collected by Sarà & Siribelli (1960, 1962).

PHENOMENA INTRUSI DASAR DI TELUK HURUN LAMPUNG

Research aimed to learn and know the bottom intrusion mechanism in Hurun Bay Lampung. Three kinds surveys were conducted consist of mooring survey, synoptic oceanographic survey and 25 hour survey. The monitoring data of water temperature indicated that at Hurun Bay occurred bottom intrusion from middle February until early July. The mass water was colder, more saline and contained less DO than the overlaying water. These phenomena may be caused by eastern monsoon from Java Sea to Lampung Bay and Hurun Bay. Vertical profile distribution showed that there are significant different in temperature, salinity and DO between surface and bottom layer. Along bottom deeper than 22m were identified as a termocline layer which was colder and more saline and contained less DO. Result of 25 hour survey resumed that the lowest DO in this water mass appeared in early July and it propagated from offshore to the coast with velocity 0.07 m/s. This condition will be a treatment for marine cultivation stakeholder in this area.Key words : Bottom Intrusion, Hypoxia

Performance Improvements in Oceanographic Survey Ship USNS SUMNER (TAGS 61)

Data are presented on the performance trials of the USNS SUMNER with a comparison of ship performance before and after the addition of a skeg. The USNS SUMNER (T-AGS 61) was one of six T-AGS 60 (PATHFINDER) Class oceanographic survey ships operated by the Military Sealift Command (MSC) for the Naval Oceanographic Office (NAVO). The primary mission of these ships is to conduct surveys of ocean bottom regions. The T-AGS 60 Class ships are mono-hulls with wide, flat stern areas that provide very little lateral projected surface area. Previous model tests and ship trials of USNS MARY SEARS (T-AGS 65) demonstrated that the ship is directionally unstable. The addition of a skeg improved directional stability of the model and MARY SEARS. Spiral maneuvers with the USNS SUMNER demonstrated similar results in pre- and post-test trials. Details of the performance calculations of the USNS SUMNER are provided with uncertainty estimates. By comparison of the ship data without the skeg to the data with the skeg, the relative difference in power averaged 28 % higher without the skeg over a speed range of 4 – 15 knots. The average speed is 6.5 % lower for the ship without the skeg at the same shaft speed.