Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary, South China

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and chemical partitioning in the sediment cores of the Pearl River Estuary (PRE) were studied. The concentrations of total metals, AVS, and SEM in the sediment cores were generally low in the river outlet area, increased along the seaward direction, and decreased again at the seaward boundary of the estuary. The amounts of AVS were generally greater in deeper sediments than in surface sediments. SEM/AVS was > 1 in the surface sediments and in the river outlet cores. The ratio was < 1 in the sediments down the profiles, suggesting that AVS might play a major role in binding heavy metals in the deep sediments of the PRE. The SEM may contain different chemical forms of trace metals in the sediments, depending on the metal reaction with 1 M cold HCl in the AVS procedure compared with the results of the sequential chemical extraction. The SEM/AVS ratio prediction may overestimate trace metal availability even in the sediments with high AVS concentrations. (c) 2004 Elsevier Inc. All rights reserved.

Parentage determination of an isolated Yangtze finless porpoise population Neophocaena phocaenoides asiaeorientalis in the Yangtze Tian-e-Zhou Baiji National Natural Reserve based on molecular data

Reproductive behaviors are poorly known for the Yangtze finless porpoise Neophocaena phocaenoides asiaeorientalis. In this study, the parentage of an isolated Yangtze finless porpoise population inhabiting the Yangtze Tian-e-Zhou Baiji National Natural Reserve is determined by analysis of microsatellite loci and mitochondrial DNA (mtDNA) control region sequences, and the porpoise's reproductive behaviors are studied. Overall 4 full parentage assignments and additional 3 single parentage assignments were determined for the population of 23 individuals. The analysis shows that their estimated reproductive cycle is shorter than that reported previously and there probably exists an overlapping between gestation and lactation period. The Study also shows that the female does not show fidelity to a particular male for breeding and vice versa, the oldest males did not monopolize mating and the dominance rank could not be so strict for the porpoise society. Moreover, the porpoise's mating pattern and relatedness among candidate parents are discussed here. These results provide important information for making guidelines of management and conservation for this protected population.

Evoked-potential audiogram of the Yangtze finless porpoise Neophocaena phocaenoides asiaeorientalis (L)

Evoked-potential audiograms were obtained in two (one male and one female) Yangtze finless porpoises, Neophocaena phocaenoides asiaseorientalis. Sinusoidal amplitude-modulated 20-ms tone bursts were used as probes with recording envelope-following evoked potentials. A frequency range of 8 to 152 kHz was investigated. The range of greatest sensitivity covered frequencies from 45 to 139 kHz, and the lowest thresholds of 47.2 and 48.5 dB re: 1 μ Pa were found at a frequency of 54 kHz in the two subjects, respectively. At lower frequencies, threshold increased with a rate of around 14 dB/octave, and threshold steeply increased at 152 kHz. © 2005 Acoustical Society of America.

Echolocation signals of the free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis)

This paper describes the high-frequency echolocation signals from free-ranging Yangtze finless porpoise in the Tian-e-zhou Baiji National Natural Reserve in Hubei Province, China. Signal analysis showed that the Yangtze finless porpoise clicks are typical high-frequency narrow-band (relative width of the frequency spectrum Q=6.6 &PLUSMN; 1.56, N=548) ultrasonic pulses. The peak frequencies of the typical clicks range from 87 to 145 kHz with an average of 125 &PLUSMN; 6.92 kHz. The durations range from 30 to 122 μ s with an average of 68 &PLUSMN; 14.12 μ s. The characteristics of the signals are similar to those of other members of the Phocoenidae as well as the distantly related delphinids, Cephalorhynchus spp. Comparison of these signals to those of the baiji (Lipotes vexillifer), who occupies habitat similar to that of the Yangtze finless porpoise, showed that the peak frequencies of clicks produced by the Yangtze finless porpoise are remarkably higher than those produced by the baiji. Difference in peak frequency between the two species is probably linked to the different size of prefer-red prey fish. Clear double-pulse and multi-pulse reverberation structures of clicks are noticed, and there is no indication of any low-frequency (< 70 kHz) components during the recording period. © 2005 Acoustical Society of America.

Distribution of the macroinvertebrate communities in the Xiangxi River system and relationships with environmental factors

Surveys of macroinvertebrates were carried out in the Xiangxi River system during July of 2001. Among the 121 taxa collected, Ephemeroptera, Trichoptera, and Diptera dominated (41.7, 26.0, and 24.5% of the total relative abundance, respectively). Two-way indictor species analysis and detrended correspondence analysis divided the 49 sites into four groups based on species composition and relative abundance. Canonical correspondence analysis indicated that elevation, SiO2, pH, conductivity, hardness, and NO2-N were significant environmental factors affecting the distribution of macroinvertebrates.

Mobilization potential of heavy metals: A comparison between river and lake sediments

Toxic metals introduced into aquatic environments by human activities accumulation in sediments. A common notion is that the association of metals with acid volatile sulfides (AVS) affords a mechanism for partitioning metals from water to solid phase, thereby reducing biological availability. However, variation in environmental conditions can mobilize the sediment-bound metal and result in adverse environmental impacts. The AVS levels and the effect of AVS on the fate of Cu, Cd, Zn, Ni in sediments in the the Changjiang River, a suboxic river with sandy bottom sediment and the Donghu Lake, a anoxic lake with muddy sediment in China, were compared through aeration, static adsorption and release experiments in laboratory. Sips isotherm equation, kinetic equation and grade ion exchange theory were used to describe the heavy metal adsorb and release process. The results showed that AVS level in the lake sediment are higher than that of the river. Heavy metals in the overlying water can transfer to sediments incessantly as long as the sediment remains undisturbed. The metal release process is mainly related to AVS oxidation in lake sediment while also related to Org-C and Fe-Mn oxyhydroxide oxidation in river sediment. The effect of sulfides on Zn and Ni is high, followed by Cd, and Cu is easy bound to Org-C. AVS plays a major role in controlling metals activity in lake sediment and its presence increase the adsorption capacity both of the lake and river sediments.

Species richness in a riparian plant community along the banks of the Xiangxi River, the Three Gorges region

The distribution of vascular plant species richness along an altitudinal gradient and their relationships with environmental variables, including slope, aspect, bank (flooding) height, and river width of the Xiangxi River, Hubei Province, were examined. Total vascular plant species richness changed with elevation: it increased at lower elevations, reached a maximum in the midreaches and decreased thereafter. In particular, tree and herbaceous species richness were related to altitude. Correlation analysis (Kendall's tau) between species richness and environmental variables indicated that the change in species richness in the riparian zone was determined by riparian environmental factors and characteristics of regional vegetation distribution along the altitudinal gradient. The low species richness at lower elevations resulted from seasonal flooding and human activities - agriculture and fuel collection - and the higher. Species richness ill (he midreaches reflected transitional zones ill natural vegetation types that had had little disturbance. These results oil species distribution in the riparian community could he utilized as a reference for restoration efforts to improve water quality of the emerging reservoir resulting from the Three Gorges Hydroelectric Dam project.

Benthic algae of the Xiangxi River, China

From June 2000 to June 2002, four sites on the mainstem of the Xiangxi River and one site on each of its major tributaries were sampled 16 times each for benthic algae. All total, 223 taxa (most to species and variety levels) were found (193 Bacillariophyta, 20 Chlorophyta, nine Cyanophyta and one Xanthophyta). The diatoms Cocconeis placentula, Achnanthes linearis, and Diatoma vulgare dominated the system, with relative abundance of 33.3%, 18.8%, and 6.4%, respectively. The abundances of all the other taxa were under 5%, and 210 taxa collectively contributed less than 1% of the total abundance. Taxa diversity peaked in winter and reached a minimum in summer. Species richness varied considerably but was not significantly different over time. Maximum algal density occurred in later winter/spring (1.4 x 10(9) ind./m(2)) but was not significantly different from the minimum density, which occurred in August. Chlorophyll a showed similar seasonal fluctuation but also was not significantly different over time. Canonical correspondence analysis demonstrated that water hardness, depth, conductivity, and alkalinity had important influences on variation of epilithic algae in the Xiangxi River system.

Comparative ontogenetic behavior and migration of kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, from the Amur River

We conducted laboratory experiments with kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, to develop a conceptual model of early behavior. We daily observed embryos (first life phase after hatching) and larvae (period initiating exogenous feeding) to day-30 (late larvae) for preference of bright habitat and cover, swimming distance above the bottom, up- and downstream movement, and diel activity. Day-0 embryos of both species strongly preferred bright, open habitat and initiated a strong, downstream migration that lasted 4 days (3 day peak) for kaluga and 3 days (2 day peak) for Amur sturgeon. Kaluga migrants swam far above the bottom (150 cm) on only 1 day and moved day and night; Amur sturgeon migrants swam far above the bottom (median 130 cm) during 3 days and were more nocturnal than kaluga. Post-migrant embryos of both species moved day and night, but Amur sturgeon used dark, cover habitat and swam closer to the bottom than kaluga. The larva period of both species began on day 7 (cumulative temperature degree-days, 192.0 for kaluga and 171.5 for Amur sturgeon). Larvae of both species preferred open habitat. Kaluga larvae strongly preferred bright habitat, initially swam far above the bottom (median 50-105 cm), and migrated downstream at night during days 10-16 (7-day migration). Amur sturgeon larvae strongly avoided illumination, had a mixed response to white substrate, swam 20-30 cm above the bottom during most days, and during days 12-34 (most of the larva period) moved downstream mostly at night (23-day migration). The embryo-larva migration style of the two species likely shows convergence of non-related species for a common style in response to environmental selection in the Amur River. The embryo-larva migration style of Amur sturgeon is unique among Acipenser yet studied.

Garra tengchongensis, a new cyprinid species from the Upper Irrawaddy River basin in Yunnan, China (Pisces : Teleostei)

Garra tengchongensis, a new cyprinid species from the upper Irrawaddy River basin in Tengchong county, Yunnan province, China, is differentiated from all other Chinese and Southeast Asian Garra species except G. kempi by having a combination of the following characters: two pairs of barbels, no proboscis on snout, 12 circumpeduncular scales and 37-42 lateral line scales. Garra tengchongensis is distinguished from G. kempi in having a cylindrical anterior body, a deeper body, a smaller mental adhesive disc, a scaled breast and belly, and a blunt snout.

Distribution of epilithic algae in the Xiangxi River system and their relationships with environmental factors

The spatial pattern of epilithic algae in the Xiangxi River system was studied in relation to several environmental factors by two-way indictor species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA). Eighty-nine taxa including diatoms, green algae, and blue-green algae were observed. Diatoms were dominant, and Cocconeis placentula, Cymbella minuta, Diatoma vulgare, and Gomphonema angustatum appeared in most of sampling sites. By TWINSPAN and DCA, thirty-one sites were divided into three groups based on composition and relative richness of benthic algae. CCA indicated that SiO2, pH, total phosphorus, Ca2+, velocity, elevation, and Cl- were significant environmental factors affecting the distribution of algae communities. In this minimal subset, SiO2 and pH were the most influential variables.

A non-linear perturbation model considering catchment wetness and its application in river flow forecasting

A non-linear perturbation model for river flow forecasting is developed, based on consideration of catchment wetness using an antecedent precipitation index (API). Catchment seasonality, of the form accounted for in the linear perturbation model (the LPM), and non-linear behaviour both in the runoff generation mechanism and in the flow routing processes are represented by a constrained nan-linear model, the NLPM-API. A total of ten catchments, across a range of climatic conditions and catchment area magnitudes, located in China and in other countries, were selected for testing daily rainfall-runoff forecasting with this model. It was found that the NLPM-API model was significantly more efficient than the original linear perturbation model (the LPM). However, restric tion of explicit nan-linearity to the runoff generation process, in the simpler LPM-API form of the model, did not produce a significantly lower value of the efficiency in flood forecasting, in terms of the model efficiency index R-2. (C) 1997 Elsevier Science B.V.

WATER-QUALITY CHANGES AND EFFECTS ON FISH POPULATIONS IN THE HANJIANG RIVER, CHINA, FOLLOWING HYDROELECTRIC DAM CONSTRUCTION

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

SESTON IN A SEASONALLY FLOODED LAKE OF THE CENTRAL CHANGJIANG RIVER (CHINA)

Seston was studied during inundation in a seasonally flooded lake of Changjiang River system (Lake Chenhu, Hanyang, P.R. China). Particulate organic matter (POM), particulate inorganic matter (PIM), particulate organic carbon (POC) and particulate organic nitrogen (PON) concentrations were highest upon initial inflow of river water, as a result of the riverine transport of allochthonous seston into the lake, and during the initial draining phase, coinciding with the postflood development of phytoplankton biomass and accumulation of detritus from the decomposition of the inundated vegetation grown during the preceding period of exposure. However seston concentrations were lowest shortly after the termination of flood inflow, presumably due to sedimentation and river water dilution. Seston food quality, based on POM : PIM, C : N and Algal-AFDW : POM ratios, was higher during the early high water phase than during the filling and draining phases.