Detection of localized methylmercury contamination by use of the mussel adductor muscle in Minamata Bay and Kagoshima Bay, Japan

Expression characteristics and functional analysis of Krüppel-like factor 4 in adductor muscle and mantle of Zhikong scallop Chlamys farreri

Krüppel-like factor 4 (KLF4) is an important transcription factor involving in formation and maintenance of muscles in mammals. However, no data are available on KLF4 function in shellfish muscles which play vital roles in the movement, stress response, and physiology in shellfish. In the present study, we revealed that the Klf4 mRNA of Zhikong scallop Chlamys farreri was expressed in most tissues, which has high level in adductor muscle, mantle, kidney, and testis. Positive signals of the Klf4 mRNA and protein were visible in all skeletal muscle fibers of adductor muscle, and all the cells of C. farreri mantle. Furthermore, the knockdown of Klf4 mRNA in adductor muscle and mantle by means of in vivo RNA interference led to some different phenotypes, including disordered arrangement of muscle fibers in adductor muscle and mantle, abnormal structures of skeletal muscles, and reduced muscle fibers under endepidermis of mantle. Our findings demonstrated that Klf4 plays important roles in maintenance of muscle functions in C. farreri adductor muscle and mantle, and suggested that its regulatory way in skeletal muscle may be different from the smooth muscle in shellfish.

Are vent crab behavioral preferences adaptations for habitat choice?

Hydrothermal vent organisms are adapted to their extreme and patchily distributed habitats. They are expected to have evolved mechanisms that keep them in their specific habitation. Since little is known about the recruitment or habitat selection of HV organisms such as brachyurans, we examined the properties of several hydrothermal vent-associated cues on the behavior of the hydrothermal vent (HV) crab Xenograpsus testudinatus in the laboratory that were contrasted by the offering of non-vent cues. This crab species is endemic and dominates the vent fauna of Turtle Island off the NE coast of Taiwan. HV crabs were separately and in combination offered the following vent-specific cues: (1) sulfuric sediment, (3) air-bubbling, (4) elevated temperature, (5) dead settled zooplankton, (7) other crabs, and (8) shade. The non-vent-specific cues were: (2) quarz sediment, (6) dead fish, (8) light. These cues were provided on either side of a two-choice chamber. The movement of individual crabs was monitored: as initial and final choices, and as the proportion of time the crabs spent in each compartment (resident time). Cues were offered alone and no such cue as a control in the same set-up. Sulfuric sediments and dead fish were significantly more attractive to females, and other crabs irrespective of gender were significantly more attractive to males. When compared to expected distributions, crabs, irrespective of gender, significantly avoided light and tended to select other crabs, air-bubbling, sulfuric sediment, elevated temperature, dead fish, dead zooplankton, and quarz sediments in the order of decreasing importance. Data do not support the hypothesis that dead settled zooplankton was particularly attractive nor that the other gender was selected. A combination of several vent-associated cues (sulfuric sediment, elevated temperature, air-bubbling) facilitated the strongest attraction to the crabs as reflected by all response variables. The 'first choice' responses were always consistent with the side of the choice compartment in which they spent the longest amount of time (resident time), but not with the 'final choice' of crabs, suggesting that the 'resident time' in addition to their 'first choice' is more reliable than just the 'final choice'. The present results provide the first indication that several vent-associated habitat cues function as attractors for HV crabs. Habitat choice is also reflected by crab larval distribution in the field which tend to stay near the bottom not to be carried away from their specific habitat.

Aeshnid dragonfly larvae as bioindicators of methylmercury contamination in aquatic systems impacted by elevated sulfate loading

Methylmercury (MeHg) levels in dragonfly larvae and water were measured over two years in aquatic systems impacted to varying degrees by sulfate releases related to iron mining activity. This study examined the impact of elevated sulfate loads on MeHg concentrations and tested the use of MeHg in dragonfly larvae as an indicator of MeHg levels in a range of aquatic systems including 16 river/stream sites and two lakes. MeHg concentrations in aeshnid dragonfly larvae were positively correlated (R(2) = 0.46, p < 0.01) to peak MeHg concentrations in the dissolved phase for the combined years of 2012 and 2013. This relation was strong in 2012 (R(2) = 0.85, p < 0.01), but showed no correlation in 2013 (R(2) = 0.02, p > 0.05). MeHg in dragonfly larvae were not elevated at the highest sulfate sites, but rather the reverse was generally observed. Record rainfall events in 2012 and above average rainfall in 2013 likely delivered the majority of Hg and MeHg to these systems via interflow and activated groundwater flow through reduced sediments. As a result, the impacts of elevated sulfate releases due to mining activities were not apparent in these systems where little of the sulfate is reduced. Lower bioaccumulation factors for MeHg in aeshnid dragonfly larvae were observed with increasing dissolved organic carbon (DOC) concentrations. This finding is consistent with previous studies showing that MeHg in high DOC systems is less bioavailable; an equilibrium model shows that more MeHg being associated with DOC rather than algae at the base of the food chain readily explains the lower bioaccumulation factors.

Hg bioaccumulation in marine copepods around hydrothermal vents and the adjacent marine environment in northeastern Taiwan

The Hg concentration in seawater and copepod samples collected from the area around hydrothermal vents at Kueishan Island and the adjacent marine environment in northeastern Taiwan were analyzed to study Hg bioaccumulation in copepods living in polluted and clean marine environments. The seawater collected from the hydrothermal vent area had an extremely high concentration of dissolved Hg, 50.6-256 ng l(-1). There was slightly higher Hg content in the copepods, 0.08-0.88 μg g(-1). The dissolved Hg concentration in the hydrothermal vent seawater was two to three orders of magnitude higher than that in the adjacent environment. The bioconcentration factor of the studied copepods ranged within 10(3)-10(6), and showed higher dissolved concentration as the bioconcentration factor was lower. A substantial abundance, but with less copepod diversity was recorded in the seawater around the hydrothermal vent area. Temora turbinata was the species of opportunity under the hydrothermal vent influence.

Mercury distribution in seawater of Kagoshima Bay near the active Volcano, Mt. Sakurajima in Japan

Kagoshima bay has a highly active volcano in its center. In the filtered seawater and suspended matter collected from 200-m deep fumaroles at the bottom of the inner bay, the geometric mean concentrations of total mercury were 7.6 and 65.0 ng/L, respectively. The surface seawater collected at the inner bay had a higher concentration of mercury when compared to that in the bay entrance (average: 1.0 vs. 0.5 ng/L). In July, however, no such difference was observed. The fumaroles seem to contribute to relatively high concentrations of mercury in the inner bay except in summer, when thermal cline is formed.

Spatial variations of mercury in sediment of Minamata Bay, Japan

Mercury-contaminated effluent was discharged into Minamata Bay from a chemical plant over a period of approximately 40 years until 1968. In October 1977, the Minamata Bay Pollution Prevention Project was initiated to dispose of sedimentary sludge containing mercury concentrations higher than 25 mg kg(-1). In March 1990, the project was completed. In an effort to estimate current contamination in the bay, the vertical and horizontal distributions of mercury in sediment were investigated. Sediment core samples were collected on June 26, 2002 at 16 locations in Minamata Bay and Fukuro Bay located in the southern part of Minamata Bay. The sediment in Fukuro Bay had not been dredged. The total mercury concentration in surface sediment was 1.4-4.3 mg kg(-1) (2.9+/-0.9 mg kg(-1), n=9) for the dredged area of Minamata Bay and 0.3-4.8 mg kg(-1) (3.6+/-1.6 mg kg(-1), n=4) for Fukuro Bay. In the lower layers of long cores taken from both areas, the total mercury concentration decreased with depth and finally showed relatively uniform low values. These values can be considered to represent the background concentration absent of anthropogenic influence, which was estimated for the study area to be 0.068+/-0.012 mg kg(-1) (n=10). From the surface, the total mercury concentration in Fukuro Bay increased with depth and reached a maximum at 8-14 cm. In Minamata Bay, several centimeters from the surface the total mercury concentration did not change significantly having considerably higher values than the background level. At six stations, the methylmercury concentration was determined. Although the vertical variations were similar to those for total mercury, Fukuro Bay sediment showed a higher concentration of methylmercury than Minamata Bay sediment.

Essential and toxic elements in seafood available in poland from different geographical regions

The concentrations of 15 elements (Cu, Fe, Mn, Zn, Co, Ni, Cr, Se, Cd, Pb, Hg, Ca, Na, K, and Mg) were determined in the edible parts of shellfish on sale in the local market in Gdańsk. The samples consisted of three groups--crustaceans, molluscs, and surimi--that are processed to different degrees. For the purposes of this analysis, they were dried, homogenized, and digested in an automatic microwave system. The samples were analyzed quantitatively for Cu, Zn, Fe, Mn, Co, Ni, Cr, Mg, Na, K, and Ca (F-AAS), Cd and Pb (GF-AAS), Se (HG-AAS), and Hg (CV-AAS). The elemental levels detected in shellfish were compared to those in cod, herring, pork, beef, chicken, and eggs. The recommended dietary allowance (RDA) of essential elements and the provisional tolerable weekly intake (PTWI) of toxic elements were estimated. With factor analysis of the data, taxonomically different groups of raw and processed shellfish could be distinguished.

Bioaccumulation of mercury in a vestimentiferan worm living in Kagoshima Bay, Japan

The present study reports on the mercury concentrations of the vestimentiferan worm, Lamellibrachia satsuma, (Annelida: Pogonophora) found near hydrothermal vents at a depth of 80-100 m in the northern parts of Kagoshima Bay. The vestimentiferan worms had total mercury concentrations of 238 ng/g in the anterior muscle of the body and 164 ng/g in the posterior trophosome. Methylmercury constituted only 7.6% of total mercury detected anteriorly and 16.3% posteriorly. The mean total mercury concentration in filtrated ambient seawater of the worm habitat was 1.1 ng/l. The worm should accumulate mercury in seawater by a one-step into the anterior and posterior parts as 2.2 x 10(%) and 1.5 x 10(5) times those of the filtered ambient seawater, respectively. The bioaccumulation factor of mercury by the worms with only their respiration would be actually larger than that by other marine animals through food webs. The high bioaccumulation factor of mercury in the worms suggest the following two possibilities: (i) the biological half-life of organomercury in the worm could be exceptionally long; or (ii) the lifetime of vestimentiferan worms examined in the present study could be extremely long. Various metals in one specimen of the worm were analyzed by using ICP-MS, and then gold as well as silver were detected in the worm. Gold was detected for the first time from marine animals.