Experimental Study of Invasion and Biofouling of Freshwater Mussel <i>Limnoperna fortunei</i>

Golden mussel Limnoperna fortunei(Dunker 1857) is a filter-collector species of fresh water mussel originating from southern China. In the water transfer tunnels from the East River to Shenzhen and Hong Kong, golden mussels attach to the walls of pipelines and gates, causing serious biofouling, increased flow resistance, and resulted in corrosion of the tunnel wall. Golden mussel has very high environmental adaptability and may colonize habitats with low dissolved oxygen and a wide range of trophic levels. The colonization process of the species on solid surface was studied in the Xizhijiang River, a tributary of the East River and the main water resource of Shenzhen from March 2010 to April 2011. The results showed that the golden mussel completed three generations and reproduced six cohorts per year in the tropic zone. Water temperature was the controlling factor for the growth rate and maturity of each cohort. Based on the results, an ecological method for controlling the invasion of golden mussels in water transfer tunnels was proposed.

Assessment of heavy metal accumulation in freshwater fish of Dongting Lake,China:Effects of feeding habits,habitat preferences and body size

We measured the concentrations of Cr,Fe,Ni,Cu,Zn,Cd,Pb and Hg,and the stable isotope ratios(δ^(13)C and δ^(15)N)in 87 fish samples within 12 economic fish species collected from the Dongting Lake,the second largest freshwater lake in China.With few exceptions in concentration of Cr,most of fish species showed lower concentrations of the 8 metals than legislation thresholds.Piscivorous fishes had significantly higher values of δ^(15)N(possessing higher trophic level)and metal concentrations than planktivorous and herbivorous fishes.Moreover,demersal fishes showed higher concentrations of Cu,Zn,Cd and Pb than pelagic and benthopelagic fishes.We found positive correlations between concentrations of Fe,Pb and Hg and δ^(15)N ratio,confirming the biomagnification of the three metals through trophic transfer.In contrast,fishes showed clear growth dilution effect for Ni,Zn,Cu,Pb and Hg,indicated by the negative correlations between their concentrations and fish weight or length.Multiple regression analysis demonstrated that growth dilution and biomagnification effects simultaneously governed the metal concentrations in fish muscle,and the two effects'importance varied among different metals.The human health risk assessment indicated that all 8 metals gave target hazard quotient(THQ)values<1.0,i.e.,the estimated daily intake(EDI)of metals did not exceed the oral reference dose(Rf D),indicating a safe consumption of these fish species for consumer.Our study provides comprehensive approaches to better understand the determining processes and potential risk of heavy metals in freshwater lake fishes.

Bioaccumulation and human health risk assessment of trace metals in the freshwater mussel Cristaria plicata in Dongting Lake, China

Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in Dongting Lake, China and the human health risks of mussel consumption are largely unknown. We investigated the concentrations of 15 trace metals and metalloids in surface water, sediments, and C. plicata organs(foot, gill, mantle, and visceral mass) and quantified the bioaccumulation and human health risk of these trace metals in specimens collected from Dongting Lake. The concentrations of most metals in surface water exceeded previously published background values. In contrast, the concentrations of most metals in sediments showed a decreasing trend. Overall, the metal concentrations in the gill and visceral masses of C. plicata were higher than those in the foot and mantle, and higher bioaccumulation capacities were observed for essential metals than for nonessential metals. The mean concentrations of the trace elements Zn, Pb, Cd, As, Cu, and Cr in C. plicata foot samples were lower than the threshold values established by international and Chinese organizations. The estimated daily intake(EDI) values of the essential metal Mn in C. plicata foot was higher than the recommended tolerable daily intake(TDI) values for juveniles. Only Mn for juveniles and As for both juveniles and adults may pose noncarcinogenic health risks through foot consumption. The hazard index(HI) values for adults and juveniles were higher than 1, suggesting significant risks of noncarcinogenic effects to humans by exposure to multiple metals.

The assemblage characteristics of benthic macroinvertebrates in the Yalutsangpo River, the highest major river in the world

Aquatic ecosystems of highland rivers are different from those of low altitude rivers because of the specific topography and environmental parameters associated with high altitudes. Yalutsangpo, the upper course of the Brahmaputra River, is the highest major river in the world, flowing from west to east across Tibet, China and pouring into India. Macroinvertebrates were sampled from Yalutsangpo and its tributaries, the Lhasa, Niyang, and Parlong Tsangpo Rivers, from October 2009 to June 2010, to study characters of the highland aquatic ecosystem. Altogether, 110 macroinvertebrate taxa belonging to 57 families and 102 genera were identified from the basin. The biodiversity and composition of macroinvertebrate assemblages were strongly affected by altitude gradients. Local diversity represented by taxa richness and the improved Shannon-Wiener index were high at altitudes of 3,300-3,700 m, among which suitability of habitat was higher due to the better integrated environmental condi- tions of water temperature, dissolved oxygen, and aquatic vegetation, etc. Macroinvertebrates were grouped into shredders, scrapers, predators, collector-filterers, and collector-gatherers according to their feeding behaviors. It was found that the distributions of the functional feeding groups varied with habitat altitudes. Shredders were present at altitudes of 2,900-4,400m, while scrapers mainly inhabited altitudes of 3,500-4,500 m, and collector-filterers preferred 3,500-4,000 m. Even though the local taxa richness was not high at each site, the taxonomic composition and density of the assemblages varied greatly among the different sites, resulting in much higher regional diversity compared to thelowland river with similar flow and substrate conditions. The regional cumulative taxa richness of Yalutsangpo decreased and more families were lost as the altitude increased. However, some families that were newly present as the altitude increased were essential for sustaining the high regional biodiversity. The ordination diagram obtained from Detrended Correspondence Analysis indi- cated that altitude, fiver pattern, riverbed structures, bank structures, and flow conditions were the main factors that influenced the macroinvertebrate assemblages in the Yalutsangpo basin.

Macrozoobenthic assemblages in relation to environments of the Yangtze-isolated lakes

Eutrophication can shift lakes from a clear, macrophyte-dominated state state, and different habitat to a turbid, algae-dominated condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis （DCA） revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals, m2 and 1.69 g dry weight.m-2, respec- tively. Macrozoobenthic assemblage was characterized by dominance of scrapers （i.e. gastropods）. In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals.m^2 and 1.38g dry weight.m-2, respectively. Macrozoobenthic assemblage was character- ized by dominance of collector-gatherers （i.e. oligo- chaetes）. Wet biomass of submersed macrophytes （BMac） and phytoplankton chlorophyll a concentration （Chla） were demonstrated as the key factor structuring macro- zoobenthic assemblages in macrophytic and algal lakes, respectively.