Food web of benthic macro invertebrates in a large Yangtze River-connected lake: the role of flood disturbance

This Study was conducted in Lake Dongtinghu, a large river-connected lake on the Yangtze River flood-plain, China. Our goal was to determine trophic relationships among benthic macroinvertebrates, as well as the effects of flood disturbance on the benthic food web of a river-connected lake. Macroinvertebrates in the lake fed mainly on detritus and plankton (both zooplankton and phytoplankton). Food web Structure in Lake Dongtinghu was characterized by molluscs as the dominant group, low connectance, high level of omnivory. based oil detritus and primary production, and most ingestion concentrating on a few links. Our analyses showed that flood disturbance is an important factor affecting the benthic food web in Lake Dongtinghu. The numbers of species and functional feeding groups (FFGs), and the density and biomass of macroinvertebrates decreased significantly during flooding. Connectance was higher during the flood season than in other seasons, indicating that floods have a strong effect on connectance in this Yangtze River-connected lake. Flood effects on the benthic web were also evident in the decrease of niche overlaps within and anion, FFGs. Our results provide useful information regarding biodiversity conservation on the Yangtze floodplain. Reconstructing and maintaining natural and regular flow regimes between Yangtze lakes and the river is essential for restoration of macroinvertebrates on the floodplain.

Microcystin accumulation in freshwater bivalves from Lake Taihu, China, and the potential risk to human consumption

The potential risk through ingestion of microcystins (MC) in contaminated mollusks has not been well studied. The present paper studied seasonal changes of MC content (determined by liquid chromatography-mass spectrometry) in various organs of three species of bivalves (Cristaria plicata, Hyriopsis cumingii, and Lamprotula leai) in Lake Taihu, China, where toxic cyanobacterial blooms occurred. Coinciding with peaks of seston MC (maximum, 5.7 mu g/L) and MC in cyanobacterial blooms (maximum, 0.534 mg/g), most organs showed sharp MC peaks during the summer, indicating both fast uptake and fast depuration by bivalves. Because hepatopancreas and intestine had considerably higher MC content than other organs, they are the most dangerous for human consumption. Both the present and previous studies show that the hepatopancreatic MC and total tissue MC often are correlated in various aquatic invertebrates. During the peak of the cyanobacterial blooms, C. plicata had higher hepatopancreatic MC content than the other bivalves, whereas H. cumingii had higher intestinal MC content than the other bivalves. Estimated daily intakes for humans from the consumption of whole tissues of the three bivalves were 0.48 to 0.94 mu g MC-LR equivalent/kg body weight (12- to 23.5-fold the tolerable daily intake value proposed by the World Health Organization), which indicates a high risk for humans consuming these bivalves.

Bioaccumulation of the hepatotoxic microcystins in various organs of a freshwater snail from a subtropical Chinese lake, Taihu lake, with dense toxic microcystis blooms

In this paper, we describe the seasonal dynamics of three common microcystins (MCs MC-RR, MC-YR, and MC-LR) in the whole body, hepatopancreas, intestine, gonad, foot, remaining tissue, and offspring of a freshwater snail, Bellamya aeruginosa, from Gonghu Bay of Lake Taihu, China, where dense toxic Microcystis blooms occur in the warm seasons. Microcystins were determined by liquid chromatography electrospray ionization mass spectrum. Microcystin (MC-RR + MC-YR + MC-LR) content of the offspring and gonad showed high positive correlation, indicating that microcystins could transfer from adult females to their young with physiological connection. This study is the first to report the presence of microcystins in the offspring of the adult snail. The majority of the toxins were present in the intestine (53.6%) and hepatopancreas (29.9%), whereas other tissues contained only 16.5%. If intestines are excluded, up to 64.3% of the toxin burden was allocated in the hepatopancreas. The microcystin content in the intestine, hepatopancreas, and gonad were correlated with the biomass of Microcystis and intracellular and extracellular toxins. Of the analyzed foot samples, 18.2% were above the tolerable daily microcystin intake recommended by the World Health Organization (WHO) for human consumption. This result indicates that public health warnings regarding human ingestion of snails from Taihu Lake are warranted. In addition, further studies are needed to evaluate the occurrence by Microcystis in relation to spatial and temporal changes in water quality.

In situ studies on the bioaccumulation of microcystins in the phytoplanktivorous silver carp (Hypophthalmichthys molitrix) stocked in Lake Taihu with dense toxic Microcystis blooms

The phytoplanktivorous silver carp is an important biomanipulation fish to control cyanobacterial blooms and is also a food fish with the greatest production in China. The accumulation of the hepatotoxic microcystins (MCs) determined by LC-MS in various organs of silver carp was studied monthly in Lake Taihu dominated by toxic Microcystis aeruginosa. Average recoveries of spiked fish samples were 78% for MC-RR and 81% for MC-LR. The highest content of MCs was found in the intestine (97.48 mu g g(-1) DW), followed by liver (6.84 mu g g(-1) DW), kidney (4.8 8 mu g g(-1) DW) and blood (1.54 mu g g(-1) DW), and the annual mean MC content was in the order of intestine > liver > kidney > blood > muscle > spleen > gallbladder > gill. Silver carp could effectively ingest toxic Microcystis cells (up to 84.4% of total phytoplankton in gut contents), but showed fast growth (from 141 g to 1759 g in I year in mean weight). Silver carp accumulated less microcystins in liver than other animals in the same site or other fish from different water bodies at similar level of toxin ingestion. There was possible inhibition of the transportation of the most toxic MC-LR across the gutwall. Muscle of silver carp in Lake Taihu should not be consumed during period of dense Microcystis blooms while viscera were risky for consumption in more months. (c) 2006 Elsevier B.V. All rights reserved.

Food web of macroinvertebrate community in a Yangtze shallow lake: trophic basis and pathways

No detailed food web research on macroinvertebrate community of lacustrine ecosystem was reported in China. The present study is the first attempt on the subject in Lake Biandantang, a macrophytic lake in Hubei Province. Food webs of the macroinvertebrate community were compiled bimonthly from March, 2002 to March, 2003. Dietary information was obtained from gut analysis. Linkage strength was quantified by combining estimates of energy flow (secondary production) with data of gut analysis. The macroinvertebrate community of Lake Biandantang was based heavily on detritus. Quantitative food webs showed the total ingestion ranged from 6930 to 36,340 mg dry mass m(-2) bimonthly. The ingestion of macroinvertebrate community was higher in the months with optimum temperature than that in other periods with higher or lower temperature. Through comparison, many patterns in benthic food web of Lake Biandantang are consistent with other detritus-based webs, such as stream webs, but different greatly from those based on autochthonous primary production (e.g. pelagic systems). It suggests that the trophic basis of the web is essential in shaping food web structure.

Seasonal dynamics of the hepatotoxic microcystins in various organs of four freshwater bivalves from the large eutrophic Lake Taihu of subtropical China and the risk to human consumption

So far, little is known on the distribution of hepatotoxic microcystin (MC) in various organs of bivalves, and there is no study on MC accumulation in bivalves from Chinese waters. Distribution pattern and seasonal dynamics of MC-LR, -YR and -RR in various organs (hepatopancreas, intestine, visceral mass, gill, foot, and rest) of four edible freshwater mussels (Anodonta woodiana, Hyriopsis cumingii, Cristaria plicata, and Lamprotula leai) were studied monthly during Oct. 2003-Sep. 2004 in Lake Taihu with toxic cyanobacterial blooms in the summer. Qualitative and quantitative determinations of MCs in the organs were done by LC-MS and HPLC. The major toxins were present in the hepatopancreas (45.5-55.4%), followed by visceral mass with substantial amount of gonad (27.6-35.5%), whereas gill and foot were the least (1.8-5.1%). The maximum MC contents in the hepatopancreas, intestine, visceral mass, gill, foot, and rest were 38.48, 20.65, 1.70, 0.64, 0.58, and 0.61 mu g/g DW, respectively. There were rather good positive correlation in MC contents between intestines and hepatopancreas of the four bivalves (r = 0.75-0.97, p < 0.05). There appeared to be positive correlations between the maximum MC content in the hepatopancreas and the delta(13)C (r = 0.919) or delta(15)N (r = 0.878) of the foot, indicating that the different MC content in the hepatopancreas might be due to different food ingestion. A glutathione (GSH) conjugate of MC-LR was also detected in the foot sample of C. plicata. Among the foot samples analyzed, 54% were above the provisional WHO tolerable daily intake (TDI) level, and the mean daily intakes from the four bivalves were 8-23.5 times the TDI value when the bivalves are eaten as a whole, suggesting the high risk of consuming bivalves in Lake Taihu. (C) 2005 Wiley Periodicals, Inc.

Bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in the foodweb of Ya-Er Lake area, China

Bioaccumulation of PCDD/F in the foodweb was investigated in the Ya-Er Lake area, which was heavily polluted by PCDD/F. The high concentrations of PCDD/F in sediment can be transferred and bioaccumulated by aquatic organisms and humans through various pathways. Benthonic invertebrate animals and aquatic plants with a lot of fibers in the root can accumulate PCDD/F from sediment and water. Snail (Bellamya aeruginosa), shrimp (Macrobranchium sp.) and freshwater mussel (Acuticosta chinensis (Lea)) took up PCDD/F from the water and maintained the emission patterns, whereas fish tended to selectively accumulate 2,3,7,8-substituted isomers. The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by PCDD/F due to ingestion of fish and other aquatic organisms from sediment. The residual concentration in breast milk depended on the original concentration of PCDD/F in the food. A resident in Ya-Er Lake area showed a daily intake of PCDD/ F of about 9.14 pg TEQ/kg body weight/day. This is higher than the tolerable daily intake (TDI) for PCDD/F (1 pg TEQ/kg body weight/day), which was recommended by the World Health Organization (WHO). (C) 2001 Elsevier Science Ltd. All rights reserved.

Evidence of host blood feeding by the monogenean, Ancyrocephalus mogurndae (Monogenea : Ancyrocephalidae) from the gills of the mandarin fish, Siniperca chuatsi

By examining iron contents, it is demonstrated that the monogenean Ancyrocephalus mogurndae (Yamaguti, 1940) feeds on the blood of its host, the mandarin fish Siniperca chuatsi (Basilewsky). The iron content and then the quantity of blood necessary to produce this amount of iron are found different in young and fully-matured worms. Young worms contain higher levels of iron and estimated amount of blood. It is suggested that A. mogurndae may start to feed on host blood as attached on gills, and the amount of blood ingested by young worms may vary from 0.01 to 1.00 mu l before reproduction. The difference between young and fully-matured worms may be accounted for by the elimination of haematin and change of food composition in matured worms and may also be affected by reproduction. Experimental infections of the monogenean may provide supportive information for explaining the difference, and further studies should also examine the effect of immune components in host blood ol mucus on the intestines of the parasite.

Analysis of nephroloxic and carcinogenic aristolochic acids in Aristolochia plants by capillary electrophoresis with electrochemical detection at a carbon fiber microdisk electrode

Aristolochic acids (AAs) are the main bioactive ingredients in the most of Aristolochia plants, which are used to make dietary supplements, slimming pills and Traditional Chinese Medicines (TCMs). Excessive ingestion of AAs can lead to serious nephropathy. Therefore, quantitative analysis and quality control for the plants containing AAs is of great importance. In this paper, capillary electrophoresis (CE) with electrochemical detection (ED) at a 33 mu m carbon fiber microdisk electrode (CFE) has been applied to detect AA-I and AA-II in Aristolochia plants. Under the optimum conditions: detection potential at 1.20 V, 2.0 x 10(-2) mol L-1 phosphate buffer solution (PBS) (pH 10.0), injection time 25 s at a height of 17 cm and separation voltage at 12.5 kV, the AA-I and AA-II were baseline separated within 5 min. Low detection limits for AA-I and AA-II were 4.0 x 10(-8) mol L-1 and 1.0 x 10(-7) mol L-1, respectively. Wide linear ranges were from 4.0 x 10(-8) mol L-1 to 1.9 x 10(-5) mol L-1 and 1.0 X 10(-7) mol L-1 to 5.0 x 10(-5) mol L-1 for AA-I and AA-II, respectively. The proposed method has been successfully applied to analyze AAs contents in plant extracts. The results indicated that the contents of AAs in each part of Aristolochia debilis Sieb. Et Zucc.

Feeding and egg production of the planktonic copepod Calanus sinicus in spring and autumn in the Yellow Sea, China

Shipboard incubations were conducted in spring (April) and autumn (October/November) 2006 to measure the feeding and egg production rates (EPR) of Calanus sinicus in the Yellow Sea, China. The ingestion rate (2.08-11.46 and 0.26-3.70 mu g C female(-1) day(-1) in spring and autumn, respectively) was positively correlated with microplankton carbon concentrations. In the northern part of the Yellow Sea, feeding on microplankton easily covers the respiratory and production requirements, whereas in the southern part in spring and in the frontal zone in autumn, C. sinicus must ingest alternative food sources. Low ingestion rates, no egg production and the dominance of the fifth copepodite (CV) stage indicated that C. sinicus was in quiescence inside the Yellow Sea Cold Bottom Water (YSCBW) area in autumn. Calanus sinicus ingested ciliates preferentially over other components of the microplankton. The EPR (0.16-12.6 eggs female(-1) day(-1) in spring and 11.4 eggs female(-1) day(-1) at only one station in autumn) increased with ciliate standing stock. Gross growth efficiency (GGE) was 13.4% (3-39%) in spring, which was correlated with the proportion of ciliates in the diet. These results indicate that ciliates have higher nutrient quality than other food items, but the low GGE indicates that the diet of C. sinicus is nutritionally incomplete.

Application of rotifer Brachionus plicatilis in detecting the toxicity of harmful algae

The toxicity of seven major HAB (harmful algal bloom) species/strains, Prorocentrum donghaiense, Phaeocystis globosa, Prorocentrum micans, Alexandrium tamarense (AT-6, non-PSP producer), Alexandrium lusitanicum, Alexandrum tamarense (ATHK) and Heterosigma akashiwo were studied against rotifer Brachionus plicatilis under laboratory conditions. The results show that P. donghaiense, P. globosa, P. micans, A. tamarense (AT-6), or A. lusitanicum could maintain the individual survival and reproduction, as well as the population increase of the rotifer, but the individual reproduction would decrease when exposed to these five algae at higher densities for nine days; H. akashiwo could decrease the individual survival and reproduction, as well as population increase of the rotifer, which is similar to that of the starvation group, indicating that starvation might be its one lethal factor except for the algal toxins; A. tamarense (ATHK) has strong lethal effect on the rotifer with 48h LC50 at 800 cells/mL. The experiment on ingestion ability indicated by gut pigment change shows that P. donghaiense, P. globosa, P. micans, A. tamarense (AT-6) and A. lusitanicum can be taken by the rotifers as food, but A. tamarense (ATHK) or H. akashiwo can be ingested by the rotifers. The results indicate that all the indexes of individual survival and reproduction, population increase, gut pigment change of the rotifers are good and convenient to be used to reflect the toxicities of HAB species. Therefore, rotifer is suggested as one of the toxicity testing organisms in detecting the toxicity of harmful algae.

Experimental study on the impact of dinoflagellate Alexandrium species on populations of the rotifer Brachionus plicatilis

To investigate harmful effects of the dinoflagellate Alexandrium species on microzooplankton, the rotifer Brachionus plicatilis was chosen as an assay species, and tested with 10 strains of Alexandrium including one known non-PSP-producer (Alexandrium tamarense, AT-6). HPLC analysis confirmed the PSP-content of the various strains: Alexandrium lusitanicum, Alexandrium minutum and Alexandrium tamarense (ATHK, AT5-1, AT5-3, ATC102, ATC103) used in the experiment were PSP-producers. No PSP toxins were detected in the strains Alexandrium sp1, Alexandrium sp2. Exposing rotifer populations to the densities of 2000 cells ml(-1) of each of these 10 Alexandrium strains revealed that the (non-PSP) A. tarnarense (AT-6) and two other PSP-producing algae: A. lusitanicum, A. minutum, did not appear to adversely impact rotifer populations. Rotifers exposed to these three strains were able to maintain their population numbers, and in some cases, increase them. Although some increases in rotifer population growth following exposures to these three algal species were noted, the rate was less than for the non-exposed control rotifer groups. In contrast, the remaining seven algal strains (A. tamarense ATHK, AT5-1, AT5-3, ATC102, ATC103; also Alexandrium sp1 and Alexandrium sp2) all have adverse effects on the rotifers. Dosing rotifers with respective algal cell densities of 2000 cells ml-1 each, for Alexandrium spl, Alexandrium sp2, and A. tamarense strains ATHK and ATC103 showed mean lethal time (LT50) on rotifer populations of 21, 28, 29, and 36h, respectively. The remaining three species (A. tamarense strains AT5-1, AT5-3, ATC102) caused respective mean rotifer LT50S of 56, 56, and 71 h, compared to 160 h for the unexposed "starved control" rotifers. Experiments to determine ingestion rates for the rotifers, based on changes in their Chlorophyll a content, showed that the rotifers could feed on A. lusitanicum, A. minutum and A. tamarense strain AT-6, but could graze to little or no extent upon algal cells of the other seven strains. The effects on rotifers exposed to different cell densities, fractions, and growth phases of A. tamarense algal culture were respectively compared. It was found that only the whole algal cells had lethal effects, with strongest impact being shown by the early exponential growth phase of A. tamarense. The results indicate that some toxic mechanism(s), other than PSP and present in whole algal cells, might be responsible for the adverse effects on the exposed rotifers. (C) 2004 Elsevier B.V. All rights reserved.