Characterization of Mediterranean magnetotactic bacteria

Magnetotactic bacteria are a diverse group of motile prokaryotes that are ubiquitous in aquatic habitats and cosmopolitan in distribution. In this study, we collected magnetotactic bacteria from the Mediterranean Sea. A remarkable diversity of morphotypes was observed, including multicellular types that seemed to differ from those previously found in North and South America. Another interesting organism was one with magnetosomes arranged in a six-stranded bundle which occupied one third of the cell width. The magnetosome bundle was evident even under optic microscopy. These cells were connected together and swam as a linear entire unit. Magnetosomes did not always align up to form a straight linear chain. A chain composed of rectangle magnetosomes bent at a posi- tion with an oval crystal. High resolution transmission electron microscopy analysis of the crystal at the pivotal position suggested uncompleted formation of the crystal. This is the first report of Mediterranean magnetotactic bacteria, which should be useful for studies of biogeochemical cycling and geohistory of the Mediterranean Sea.     

Morphological and phylogenetic diversity of magnetotactic bacteria and multicellular magnetotactic prokaryotes from a mangrove ecosystem in the Sanya River,South China

Journal of Oceanology and Limnology - Magnetotactic bacteria (MTB) are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular...     

Characterization and diversity of magnetotactic bacteria from sediments of Caroline Seamount in the Western Pacific Ocean

Journal of Oceanology and Limnology - Magnetotactic bacteria(MTB) are a group of microorganisms capable of orientating and swimming along magnetic fields because they contain intracellular...     

Observations on a magnetotactic bacteria-grazing ciliate in sediment from the intertidal zone of Huiquan Bay,China

Journal of Oceanology and Limnology - Magnetotactic bacteria(MTB) are a group of prokaryotes having the ability to orient and swim along geomagnetic fi eld lines because they contain intracellular...     

CHARACTERIZATION OF FINE-GRAINED TURBIDITE DEPOSITS FROM THE SOUTH CHINA SEA SEDIMENT CORES

Two depositional processes controlled the muddy sediments in the South China Sea Basin. Bathyal sediments depositional rate was 7.66 cm/la in the northern continental slope of the Basin where turbidity current was almost nonexistent. In the northern margin of the Basin, abyssal sediment depositional rate was 5.05cm/ka and turbidity current occurrence averaged 0.22 per 1000 years. Turbidite was found in the middle of the Basin. Over half of the muddy sediments in the deep sea basin were deposited by turbidity currents, and had typically graded bedding, and contents of organic matter, calcareous material and micropaleontologic species inconsistent with the environment.     

Occurrence and microscopic analyses of multicellular magnetotactic prokaryotes from coastal sediments in the Yellow Sea

Multicellular magnetotactic prokaryotes(MMPs) are a group of aggregates composed of 7-45 gram-negative cells synthesizing intracellular magnetic crystals.Although they are thought to be globally distributed,MMPs have been observed only in marine environments in America and Europe.Most MMPs share a rosette-like morphology and biomineralize iron sulfide crystals.In the present study,abundant MMPs were observed,with a density of 26 ind./cm3,in the sediments of a coastal lagoon,Lake Yuehu,in the Yellow Sea.Optical microscopy showed that all of them were rosette shaped with a diameter of 5.5±0.8 mm.Transmission electron microscopy revealed that these MMPs were composed of 10-16 ovoid cells and flagellated peritrichously.High-resolution transmission electron microscopy and energy dispersive X-ray analysis indicated that they biomineralized bullet-shaped magnetite crystals in highly organized parallel chains within which the magnetosomes were oriented in the same direction.This is the first report of MMPs from Asia and demonstrates the ubiquitous distribution of MMPs.     

Study on the dominant species of Pteropoda in East China Sea

1 INTRODUCTION Pteropoda is a group of marine pelagic mol- lusks, which belongs to Opisthobranchia of Gastro- poda. Although Pteropoda is not a major group in pelagic zooplankton in terms of abundance and number of species, their ecological characters are…     

An isopycnic-coordinate internal tide model and its application to the South China Sea

A three-dimensional isopycnic-coordinate ocean model for the study of internal tides is presented. In this model, the ocean interior is viewed as a stack of isopycnic layers, each characterized by a constant density. The isopycnic coordinate performs well at tracking the depth variance of the thermocline, and is suitable for simulation of internal tides. This model consists of external and internal modes, and barotropic and baroclinic motions are calculated in the two modes, respectively. The capability of simulating internal tides was verified by comparing model results with an analytical solution. The model was then applied to the simulation of internal tides in the South China Sea (SCS) with the forcing of M2 and K1 tidal constituents. The results show that internal tides in the SCS are mainly generated in the Luzon Strait. The generated M2 internal tides propagate away in three different directions (branches). The branch with the widest tidal beam propagates eastward into the Pacific Ocean, the most energetic branch propagates westward toward Dongsha Island, and the least energetic branch propagates southwestward into the basin of the SCS. The generated K1 internal tides propagate in two different directions (branches). One branch propagates eastward into the Pacific Ocean, and the other branch propagates southwestward into the SCS basin. The steepening process of internal tides due to shoaling effects is described briefly. Meridionally integrated westward energy fluxes into the SCS are comparable to the meridionally integrated eastward energy fluxes into the Pacific Ocean.     

Determination of the heating efficiency of magnetotactic bacteria in alternating magnetic field

Journal of Oceanology and Limnology - Magnetotactic bacteria (MTB) intact cells have been applied in magnetic hyperthermia therapy of tumor, showing great efficiency in heating for tumor cell...     

Temporal variations in internal tide multimodal structure on the continental shelf,South China Sea

Temporal variations in multimodal structures of diurnal (D ₁) and semidiurnal (D ₂) internal tides were investigated on the continental slope of the Dongsha Plateau, based on 2-month moored acoustic Doppler current profiler observations. Harmonic analysis indicated that the D ₁ components (K ₁ and O ₁) dominated the internal tide field. The vertical structure of the K ₁ constituent presented a first-mode structure while the M ₂ constituent seemed to exhibit a high-mode structure. Amplitude spectra analysis of the current data revealed differences in baroclinic current amplitudes between different water depths. Temporal variations in modal structures ware analyzed, based on the D ₁ and D ₂ baroclinic tides extracted from the baroclinic velocity field with band-pass filters. Analysis showed that the magnitude of the D ₁ internal tide current was much larger than the D ₂ current, and temporal variations in the modal structure of the D ₁ internal tide occurred on an approximately fortnightly cycle. The EOF analyses revealed temporal transformation of multimodal structures for D ₁ and D ₂ internal tides. The enhancement of the D 1 internal tide was mainly due to the superposition of K ₁ and O ₁, according to the temporal variation of coherent kinetic energy.     

FIVE RED TIDE SPECIES IN GENUS PROROCENTRUM INCLUDING THE DESCRIPTION OF PROROCENTRUM DONGHAIENSE LU SP. NOV. FROM THE EAST CHINA SEA

A new planktonic dinoflagellate, Prorocentrum donghaiense I_a sp. nov., is described in the present paper. The water sample was collected from the Changjiang Estuary, the East China Sea. The species identification is based on shape, size, surface micro-morphology, ornamentation of thecal plates and the architecture of the pel‘iflagellar area and the intercalary bands as seen by fight and scanning electron microscope. Prorocentrum donghaiense Lu sp. nov. is compared with other prorocentrum species with respect to morphological characteristics and bloom behavior. It is not known whether Prorocentrum donghaiense Lu sp. nov produces phycotoxins like some other Prorocentrum species. Four other red tide species in the family Prorocentraceae (Dinophyceae), namely P. balticum, P. minimum, P.micans, P. triestinum, were examined and identified by light and scanning electron microscope. They have been recorded as bloom-forming species. Some aggregates of Prorocentrum are observed at the end of blooms. An event of strong discoloration caused by P. donghaiense could be detected by satellite sensor in the East China Sea in the late spring, of 1995.     

Optimal salinity for dominant copepods in the East China Sea, determined using a yield density model

From 1997 to 2000, four field surveys were conducted in the East China Sea (ECS) (23°30′–33°00′N, 118°30′–128°00′E). A field data yield density model was used to determine the optimal salinities for 19 dominant copepod species to establish the relationship between surface salinities and abundance of those species. In addition, ecological groups of the copepods were classified based on optimal salinity and geographical distribution. The results indicate that the yield density model is suitable for determining the relationship between salinity and abundance. Cosmocalanus darwini, Euchaeta rimana, Pleuromamma gracilis, Rhincalanus cornutus, Scolecithrix danae and Pareucalanus attenuatus were determined as oceanic species, with optimal salinities of >34.0. They were stenohaline and mainly distributed in waters influenced by the Kuroshio or Taiwan warm current. Temora discaudata, T. stylifera and Canthocalanus pauper were nearshore species with optimal salinities of <33.0 and most abundant in coastal waters. The remaining 10 species, including Undinula vulgaris and Subeucalanus subcrassus, were offshore species, with optimal salinity ranging from 33.0–34.0. They were widely distributed in nearshore, offshore and oceanic waters but mainly in the mixed water of the ECS.     

Purification and Characterization of an Alkaline Protease from Micrococcus sp.Isolated from the South China Sea

Protease is wildly used in various fields,such as food,medicine,washing,leather,cosmetics and other industrial fields.In this study,an alkaline protease secreted by Micrococcus NH54PC02 isolated from the South China Sea was purified and characterized.The growth curve and enzyme activity curve indicated that the cell reached a maximum concentration at the 30 th hour and the enzyme activity reached the maximum value at the 36 th hour.The protease was purified with 3 steps involving ammonium sulfate precipitation,ion-exchange chromatography and hydrophobic chromatography with 8.22-fold increase in specific activity and 23.68% increase in the recovery.The molecular mass of the protease was estimated to be 25 k Da by SDS-PAGE analysis.The optimum temperature and p H for the protease activity were 50℃ and pH 10.0,respectively.The protease showed a strong stability in a wide range of pH values ranging from 6.0–11.0,and maintained 90% enzyme activity in strong alkaline environment with p H 11.0.Inhibitor trials indicated that the protease might be serine protease.But it also possessed the characteristic of metalloprotease as it could be strongly inhibited by EDTA and strongly stimulated by Mn~(2+).Evaluation of matrix-assisted laser desorption ionization/time-of-flight MS(MALDI-TOF-TOF/MS) showed that the protease might belong to the peptidase S8 family.     

A new species of Parodontophora (Nematoda: Axonolaimidae) from the intertidal zone of the East China Sea

This study described a new species of free-living nematode discovered in the intertidal mudflat of Ximen Island,East China Sea.The new species,designated Parodontophora longiamphidata sp.nov.,was characterized by a cylindrical body with tapering extremeties;cuticle smooth without somatic setae;four short cephalic setae;cylindrical buccal cavity with six clawlike teeth at the top of stoma;pharynx cylindrical with widened base;amphidial fovea crook-shaped with elongated scalariform branch extending past level of base of pharynx and ventral gland;ventral gland cell long-oval shaped located posterior to pharyngo-intestinal junction;excretory pore at level of middle of buccal cavity;tail conico-cylindrical with enlarged tip;three caudal gland cells,male spicules arched with cephalic proximal end and tapered distal end;gubernaculum with dorso-caudal apophysis;female with two opposed outstretched ovaries;and vulva at slightly post-midpoint of body length.This new species was close to P.wuleidaowanensis Zhang,2005 and P.polita Gerlach,1955 in terms of long amphidial fovea branch.The newly found species was easily distinguishable from the two documented;its amphidial fovea branch(255–290 μm versus 72–106 and 125–150 μm) was obviously longer.Key to the Parodontophora species with a longer amphidial fovea branch was given.     

Pseudolella major sp. nov.(Axonolaimidae,Nematoda) from the intertidal zone of the East China Sea

A new species of free-living nematode, Pseudolella major sp. nov. is described from the intertidal mudflats of Ximen Island in the East China Sea. Pseudolella major sp. nov. is characterized as follows: body length ~1 300 μm; short cephalic setae, 2–3 μm long; amphidial fovea loop-shaped with elongated ventral branch; ventral branch 50–60 μm long and extending past the base of buccal cavity; buccal cavity cylindrical with arching or spherical base; three heavy outwardly-curving odontia with blunt tips located at anterior of buccal cavity; pharynx short with posterior bulb; ventral gland cell elongate oval-shaped, located posterior to pharyngo-intestinal junction; excretory pore situated at the level of the middle of buccal cavity; tail conical to cylindrical; spicules arched, with double-cephalate proximal end; gubernaculum with a strong dorsal caudal apophysis.     

Oncholaimus zhangi sp. nov. (Oncholaimidae,Nematoda) from the intertidal zone of the East China Sea

A new species of free-living marine nematode is described from intertidal sediment of the East China Sea.The new species belongs to the Oncholaimidae family.Oncholaimus zhangi sp.nov.is characterized by males having a large ventral swelling situated just posterior to the middle of the tail,no precloacal papilla,and a row of 6–7 ventral genital setae.The tails of both males and females are similar,being conico-cylindrical in shape.The new species is distinguished from other closely related species by the presence of a prominent ventral swelling at the tail of males and a similar tail shape in both sexes.About 110valid species in this genus have been recorded to date.     

Dissolved organic matter and its role in red tide succession in the East China Sea in spring

Dissolved fluorescent organic matter was measured using fluorescence excitation-emission matrix spectroscopy at three temporal points during a Synechococcus bloom after diatom bloom dispersion in spring, 2007. Carbohydrate and dissolved organic carbon were also analyzed. The relationship between organic matter and red tide succession was examined. The results show that after the diatom bloom, tyrosine-like fluorescence B intensity was very high within the water column and exhibited a negative correlation wi...     

The impact of atmospheric deposition of cadmium on dominant algal species in the East China Sea

Cadmium(Cd) mainly derived from anthropogenic emissions can be transported through atmospheric pathway to marine ecosystem,affecting the phytoplankton community and primary productivity.In this study,we identified the toxicity threshold of Cd for phytoplankton under seawater conditions of the coastal East China Sea(ECS) through both laboratory and in situ mesocosm incubation experiments.The mesocosm experiment showed that Cd in low concentration(0.003 μg per μg chl a) was conducive to the growth of natural community and increased chl a productivity.In high concentration(0.03 μg per μg chl a) Cd acted as an inhibiting factor which decreased the total chl a productivity.The diatom community was found to be more sensitive to Cd toxicity than dinoflagellate,as the low concentration Cd showed toxicity to diatom but enhanced dinoflagellate growth.We noticed that the soluble Cd estimated from atmosphere deposition to the coastal ECS was below the toxicity threshold and the Cd deposition might promote phytoplankton growth in this region.In our laboratory experiments,adding Cd,similar to aerosol deposition,stimulated the growth of both dominant algal species Prorocentrum donghaiense Lu(dinoflagellate) and Skeletonema costatum(diatom).Adding Cd on a higher level inhibited the growth of both the species,but Skeletonema costatum seemed obviously more sensitive to toxicity.This indicates the potential impact of atmospheric deposition Cd on phytoplankton community succession in the ECS.     

Long-Term Characterization of Sea Conditions in the East China Sea Using Significant Wave Height and Wind Speed

In this study, the statistical characterization of sea conditions in the East China Sea(ECS) is investigated by analyzing a significant wave height and wind speed data at a 6-hour interval for 30 years(1980–2009), which was simulated and computed using the WAVEWATCH Ⅲ(WW3) model. The monthly variations of these parameters showed that the significant wave height and wind speed have minimum values of 0.73 m and 5.15 ms~(-1) and 1.73 m and 8.24 ms~(-1) in the month of May and December, respectively. The annual, seasonal, and monthly mean sea state characterizations showed that the slight sea generally prevailed in the ECS and had nearly the highest occurrence in all seasons and months. Additionally, the moderate sea prevailed in the winter months of December and January, while the smooth(wavelets) sea prevailed in May. Furthermore, the spatial variation of sea states showed that the calm and smooth sea had the largest occurrences in the northern ECS. The slight sea occurred mostly(above 30%) in parts of the ECS and the surrounding locations, while higher occurrences of the rough and very rough seas were distributed in waters between the southwest ECS and the northeast South China Sea(SCS). The occurrences of the phenomenal sea conditions are insignificant and are distributed in the northwest Pacific and its upper region, which includes the Southern Kyushu-Palau Ridge and Ryukyu Trench.     

Variation of bacteria biomass and its possible controlling factors in the East China Sea

Two surveys were performed for determining bacteria biomass (BB), temperature, salinity, chlorophyll a (chl-a) and nutrient concentrations at 11 stations with three sampling depths in the high-incidence regions of red tide in the East China Sea (ECS) in the spring of 2006. Temperature and salinity increased from nearshore to offshore region and from high latitude to low latitude in the two cruises of 2006. BB were between 0.3–5.2 mgC m⁻³ (about 2.1 mgC m⁻³ on average) and 0.2–6.0 mgC m⁻³ (about 2.7 mgC m⁻³ on average) respectively in the two cruises. BB in the surface layer decreased from the Changjiang River estuary to high sea and from low latitude to high latitude. The results showed that bacterial growth was regulated by temperature, primary production and inorganic nutrient concentrations depending on different hydrographic conditions. In the surface and middle layers where the primary production can supply enough organic substrate, temperature was the main factor to control bacteria biomass. BB showed a good correlation between the surface and middle layers in both cruises. The distribution of nutrients during both cruises showed a similar decreasing trend from nearshore region and high latitude to offshore region and low latitude. High BB values were mainly recorded from samples in the middle layer where chl-a concentrations were also high, indicating primary production being strongly correlated with temperature over the ECS shelf. In the offshore area, phosphate and silicate became limiting factors for phytoplankton growth with indirect influence on BB. Bacteria played an important role in nitrogen regeneration process turning organic nitrogen to inorganic forms such as NH₄ ⁺. The increasing ratio of NH₄ ⁺/DIN could be a proof of that.