Size effects of suspended particles on gill damage in green-lipped mussel Perna viridis

The green-lipped mussels Perna viridis were exposed to <500 μm suspended solids (SS) with concentrations of 0 (control), 250, 500, 750 and 1000 mg/L for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significantly higher damages to the cilia on the frontal surface of the gill filaments than that on the abfrontal surface in both demibranchs. Percent ciliary depletion varied with SS concentrations and time. No sign of recovery of the gill filaments was observed after the mussels were transferred to clean seawater. In a second experiment, mussels were exposed to SS with size range from <63, >125–<250 and >250–<500 μm at 600 mg/L, together with a control (0 mg/L) for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significant ciliary damages in both the ascending and descending lamellae under the three particle size groups as compared with the control. Percent depletion of frontal cilia was most serious for the >250–<500 μm size group and least for the <63 μm size group. However, percent depletion of abfrontal cilia was most serious for the >125–<250 μm size group and least for the <63 μm size group. No recovery of ciliary damages was observed. The effects of particle size of suspended sediments on the morphological damages of gill filaments in the green-lipped mussels were discussed.     

Size effects of suspended particles on gill damage in green-lipped mussel Perna viridis

The green-lipped mussels Perna viridis were exposed to <500 μm suspended solids (SS) with concentrations of 0 (control), 250, 500, 750 and 1000 mg/L for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significantly higher damages to the cilia on the frontal surface of the gill filaments than that on the abfrontal surface in both demibranchs. Percent ciliary depletion varied with SS concentrations and time. No sign of recovery of the gill filaments was observed after the mussels were transferred to clean seawater. In a second experiment, mussels were exposed to SS with size range from <63, >125–<250 and >250–<500 μm at 600 mg/L, together with a control (0 mg/L) for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significant ciliary damages in both the ascending and descending lamellae under the three particle size groups as compared with the control. Percent depletion of frontal cilia was most serious for the >250–<500 μm size group and least for the <63 μm size group. However, percent depletion of abfrontal cilia was most serious for the >125–<250 μm size group and least for the <63 μm size group. No recovery of ciliary damages was observed. The effects of particle size of suspended sediments on the morphological damages of gill filaments in the green-lipped mussels were discussed.     

Immune responses to combined effect of hypoxia and high temperature in the green-lipped mussel Perna viridis

Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O2 l(-1), 6.0 mg O2 l(-1)) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O2 l(-1)) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.     

Immune responses to combined effect of hypoxia and high temperature in the green-lipped mussel Perna viridis

Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O₂ l⁻¹, 6.0 mg O₂ l⁻¹) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O₂ l⁻¹) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.     

Turbidity and suspended solids variations downstream of a regulating reservoir

A controlled reservoir release from Llyn Celyn to the Afon Tryweryn, Wales, U.K., has been used to study suspended load and turbidity variations. Turbidity was monitored continuously at two sites and 235 suspended solids samples were obtained at these and three additional sites during the passage of the release wave. The results are compared with data for a natural tributary flood event. The reservoir release data relate to sediment source depletion and reflects changing sources along the channel. Close to the dam, fine organic matter dominates the seston which scanning electron microscopy revealed to be predominantly allochthonous organic matter, with algal fragments and inorganic diatom frustules, derived from the periphyton of the channel bed. Coulter Counter analysis showed the seston to be relatively coarse with a median particle-size of 20 μm. Within 3 km of the dam, however, minerogenic particles dominate the sediment load of which more than 90 per cent is finer than 10 μm. This represents the flushing of channel-bed accumulations derived from tributary sources. The relationships between suspended sediment concentration and turbidity during the release are characterized by a marked, anticlockwise hysteresis. This contrasts with the clockwise hysteresis for the tributary flood event, but the different relationships cannot be explained by particle-size variations alone; seston composition also appears to be an important control.     

Effect of size, tissue parts and location on six biochemical markers in the green-lipped mussel, Perna viridis

The effect of size and tissue parts as well as site locations on a suite of six anti-oxidative biochemical markers, viz. the enzyme degrading neural transmitters acetylcholinesterase (AChE), the Phase II transforming enzyme glutathione-S-transferase (GST), the anti-oxidative enzymes superoxide dismutase (SOD) and catalase (CAT), the lipid metabolite malondialdehyde (MDA) and the ratio of CAT/MDA, in the bivalve mollusc, Perna viridis, was studied. Field mussels were collected from the piers of University of Science and Technology (UST), Pak Sha Wan or Hebe Haven (PS) and Sai Kung (SK) in Port Shelter, Hong Kong. Statistically, ANOVA showed that the activity of all six biochemical markers were generally tissue dependent, size independent and location dependent. Tukey multi comparison test indicated that the biochemical activities fell into two groups, with SK the highest activity group in most cases. The significance of these findings in relation to long-term coastal water biomonitoring is discussed.     

Potential of turbidity monitoring for measuring the transport of suspended solids in streams

Investigating the transport of suspended solids by water sampling usually leads to an underestimation of loads and an unrealistically high sampling frequency is required to properly characterize temporal trends. An alternative method is to use in situ optical turbidimeters to estimate the suspended solids concentration; however, the relationship between turbidity and suspended solids concentration is potentially confounded by variations in particle size, particle composition and water colour. Field measurements, and laboratory measurements using the type of natural material suspended in streamwater, were made to quantify the influences of these factors on nephelometric turbidity (Hach 2100A) and attenuance turbidity (Partech 7000 3RP MKII). The attenuance turbidity was approximately 2.5 times higher than nephelometric turbidity. The turbidity instruments were most sensitive to dispersions with a median diameter of 1.2-1.4γm. Particle size variation can cause the turbidity to vary by a factor of four for the same concentration of suspended solids. However, the numerous close correlations between turbidity and suspended solids concentration reported previously suggests that either the particle size variations are not usually great, or that particle size variations are often associated with variations in suspended solids concentration. For the same concentration and particle size, organic particles gave attenuance turbidity values two to three times higher than mineral particles. However, shortterm temporal variations from purely organic to purely mineral particle loads are rare in nature, so variations in the percentage of organic matter in the paniculate load will not confound turbidity to this extent. Coloured dissolved organic matter is unlikely to alter the turbidity reading by more than 10%. An adequate relationship between turbidity measured in the field and suspended solids concentration should be expected in most situations. Some variance can be tolerated because a continuous estimate of suspended solids concentration overcomes the problem of infrequent sampling, which is the greatest source of error in the estimation of stream sediment loads.     

The combined effects of oxygen availability and salinity on physiological responses and scope for growth in the green-lipped mussel Perna viridis

Mussels were maintained for 4 weeks under different combinations of dissolved oxygen concentration (1.5, 3.0 and 6.0 mg O₂ l⁻¹) and salinity (15, 20, 25 and 30) in a 3 × 4 factorial design experiment. Clearance rate (CR), absorption efficiency (AE), respiration rate (RR) and scope for growth (SFG) decreased with decreasing salinity and dissolved oxygen concentration (DO), while excretion rate (ER) increased with decreasing salinity and increasing DO. The O:N ratio was <10 at salinities of 15 and 20, irrespective of DO levels. SFG was negative in most of the treatments, except for those under 6.0 mg O₂ l⁻¹ or at a salinity of 30 when DO was lower. The results may help explain the distribution pattern of Perna viridis in Hong Kong waters and provide guidelines for mussel culture site selection.     

The combined effects of oxygen availability and salinity on physiological responses and scope for growth in the green-lipped mussel Perna viridis

Mussels were maintained for 4 weeks under different combinations of dissolved oxygen concentration (1.5, 3.0 and 6.0 mg O2 l(-1)) and salinity (15, 20, 25 and 30) in a 3×4 factorial design experiment. Clearance rate (CR), absorption efficiency (AE), respiration rate (RR) and scope for growth (SFG) decreased with decreasing salinity and dissolved oxygen concentration (DO), while excretion rate (ER) increased with decreasing salinity and increasing DO. The O:N ratio was <10 at salinities of 15 and 20, irrespective of DO levels. SFG was negative in most of the treatments, except for those under 6.0 mg O2 l(-1) or at a salinity of 30 when DO was lower. The results may help explain the distribution pattern of Perna viridis in Hong Kong waters and provide guidelines for mussel culture site selection.     

The effects of hydrological factors on river suspended solids contamination from a colliery in South Wales

Suspended solids contamination caused by runoff below a working colliery in the Upper Clydach catchment in South Wales, U.K., was investigated in relation to hydrological controls. Field studies over a 16 month period found that concentrations below the colliery ranged from 4 to 8028 mg 1^?1. Simple correlation and linear regression analysis of spot and storm event samples taken below the colliery gave a correlation coefficient of 0·39 between flow and suspended solids concentration. Because of the lack of explained variance, a multiple linear regression model of within-storm concentrations was derived using four selected independent variables. X₁ the time relation of the sample to the storm peak; log X₂ the stormflow at the time of sampling; log X₃ the baseflow at the time of sampling; and log X₄ an index of the storm intensity. Analysis of the entire dataset gave an R² of 0·34. When the results from three atypical events were excluded however, the R² value improved to 0·65. Beta coefficients indicated that rising limb conditions (X₁) and intense storms (log X₄) along with dry antecedent conditions (log X₃) represent the worst combination of hydrological factors for producing suspended solids contamination.     

Influences of ammonia-nitrogen and dissolved oxygen on lysosomal integrity in green-lipped mussel Perna viridis: laboratory evaluation and field validation in Victoria Harbour, Hong Kong

Lysosomal integrity in mussels has been applied as a biomarker to detect the pollution of trace organics and metals in the natural environments. However, few studies have examined the effects of water quality on the response of lysosomal integrity, in particular total ammonia-nitrogen (TAN) and dissolved oxygen (DO). This study demonstrated that high level of TAN (2.0 mg/l) and low DO (2.5 mg O₂/l) could significantly reduce the lysosomal integrity in green-lipped mussel Perna viridis, respectively by 33% and 38%, whereas the mussel lysosomal integrity decreased by 70% in the combined treatment of TAN and low DO under laboratory conditions after one week. The mussel lysosomal integrity of all treatment groups could return to the control level after a three week recovery period. In the field validation in Victoria Harbour, Hong Kong during an one-year study period, lysosomal integrity in P. viridis identified the cleanest site east to the harbour, where the lowest TAN and highest DO concentrations were found. While lysosomal integrity in mussels seemed not affected by seasonal changes, approximately 40% of the variation of this biomarker could be attributable to the changes in TAN and DO in seawater. In conclusion, the response of the mussel lysosomal integrity can be confounded by both TAN and DO prevailing in the natural environments and thus caution must be exercised in relating the observed changes in lysosomal integrity to any specific pollutant in coastal water quality monitoring studies.     

Uptake and depuration of PAHs and chlorinated pesticides by semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis)

Semi-batch seawater experiments were conducted to follow the uptake and release of selected PAHs (anthracene, fluorathene, pyrene and B[a]P) and organochlorine pesticides (-HCH, aldrin, dieldrin, p,p′-DDT) in semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis). Mathematical models were applied to describe the uptake and elimination curves of the contaminants for SPMDs, and kinetic parameters, such as uptake rate constants, and equilibrium triolein/water partitioning coefficients were calculated. SPMD data showed a good fit to estimate rate constant and partition coefficient equations, but only those contaminants which partitioned mainly in the dissolved phase (-HCH and dieldrin) were well explained for mussels. Poor conformity of the other contaminants indicated mussels uptake by routes other than diffusion, such as ingestion of algae. An apparent equilibrium state was only noted for -HCH in mussels. Aldrin was not detected in mussels in the first few days of exposure, indicating potential metabolism of this compound. B[a]P was not detected in the triolein of SPMDs, which suggests that the membrane may act as a reservoir. Loss of spiked B[a]P from the triolein was evident in a depuration experiment, which may indicate transfer to the membrane. Rate constants for mussels were higher than those for SPMDs, but the reverse was true for partition coefficients. Overall, mussels and SPMDs had similar uptake rates for all compounds in this study, excluding p,p′-DDT and dieldrin. Contaminant elimination took place more rapidly in mussels, implying that SPMDs are better candidates for detecting episodic discharge of organic contaminants.     

Transport and delivery of suspended solids, nitrogen and phosphorus from various sources to freshwaters in the UK

Sources of nutrients and suspended solids (SS) are diverse in origin and dynamic with respect to their transport pathways and delivery to surface and groundwaters. Three broad source groups can be identified based on their hydrological and compositional characteristics. Consented discharges from point sources are generally continuous and highly concentrated relative to receiving waters while non-point (diffuse) sources are generally more dilute with SS and phosphorus in particular tending to have a high transport dependence upon hydrological (storm) events. A third group with properties that are intermediate include overflows from septic systems, seepages from farmyards or road/track runoff. This grouping automatically introduces a strong temporal and spatial variability in the relative contribution individual group sources make to the total quantity of nutrients and SS delivered to freshwaters. This spatial or temporal variability in either effluent volumes or composition is generally not considered when predicting impacts, which can be highly significant in headwater streams. Complete compositional data for individual sources (especially the intermediary group) are also often lacking when apportioning source contributions in catchments, being simply lumped into average export coefficients. Better definition of intermediary sources would help to more accurately define the relative contribution of different sources and enable cost-effective river basin management planning as required under the Water Framework Directive.     

Biomonitoring of heavy metals and trace organics using the intertidal mussel Perna viridis in Hong Kong coastal waters

This paper presents the results of a 6-year (1998–2003) survey of trace toxics in the intertidal mussel Perna viridis conducted by the Hong Kong Environmental Protection Department. Concentrations of heavy metals and trace organics were measured in the soft bodies of P. viridis collected from five sites in Hong Kong waters, i.e. Wu Kai Sha (Tolo Harbour), Ma Wan (Northwest), Tsim Sha Tsui (Victoria Harbour), Tai Tam (Hong Kong South) and Lamma Island (Southern Waters) in order to establish the spatial patterns of contaminants in mussels. Among the metals analysed, Cd showed a significant concentration gradient in Hong Kong waters. The levels of Cd in P. viridis were significantly higher at Ma Wan as compared to the other sites studied. Ma Wan also had relatively higher concentrations of Pb. Mn concentrations were particularly prominent at Wu Kai Sha. Significantly higher concentrations of Hg and Cu were recorded at Tai Tam and Tsim Sha Tsui. Tai Tam and Wu Kai Sha had higher levels of V; whereas higher Ni concentrations were recorded at Lamma Island and Tai Tam. No clear spatial patterns for Al, As, Cr, Fe and Zn were observed.

Higher concentrations of PAHs in P. viridis were observed around urban centres impacted by sewage discharges (e.g. Tsim Sha Tsui); whereas higher PCB levels were found not only in Tsim Sha Tsui but also in less urbanised areas such as Lamma Island and Tai Tam, suggesting that these may be due to non-sewage related inputs. The study also shows that Northwest and Southern waters are subject to a higher degree of DDT pollution compared with other sites. Of the 17 dioxin compounds analysed, positive data were mostly recorded for two compounds which are of low toxicity (i.e. OCDD and 1,2,3,4,6,7,8-HpCDD) whereas the most toxic congeners (i.e. 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD) were not detected in the 6 years of monitoring. In general, the levels of OCDD in P. viridis were found to be higher in Tai Tam and Lamma Island in Southern Waters of Hong Kong.

This study found that the levels of some highly toxic heavy metals (i.e. Cd, Hg and Pb) in the mussel P. viridis did not exceed the recommended limits for shellfish as food in Hong Kong (i.e. Cd: 2.0 ppm; Hg: 0.5 ppm; Pb: 6.0 ppm wet weight). The levels of As and Ni in P. viridis were also well below the action limits set by the US FDA (i.e. As: 86 ppm; Ni: 80 ppm wet weight). DDT and PCB contaminations in P. viridis were below the concentrations of concern. Compared with data obtained in the 1980s, the current levels of DDTs in P. viridis were 4–16 times lower; whereas Pb concentrations recorded in Tsim Sha Tsui have also been lowered significantly. This is mainly related to reduction in local and regional pollution sources in the past 20 years.     

Using an integrated model to track the fate and transport of suspended solids and heavy metals in the tidal wetlands

An integrated two-dimensional depth-average numerical model was developed to simulate hydrodynamics and to track the fate and transport of contaminants in the Erh-Chung Flood Way wetland in northem Tai...     

Recovery and concentration of suspended solids in the upper rhone river by continuous flow centrifugation

Six stations along the Rhône River from the Rhône Glacier to Lake Geneva were sampled by continuous flow centrifuge for recovery of suspended sediment. The samples were taken four times in the year in both 1982 and 1983. In addition, the mouth of the river was sampled in a like manner every two weeks during 1982 until August 1983. Concentration of sediment and composition did not vary as a function of depth or location across the river. Concentrations varied in time and as a function of flow and samples showed both increasing concentration in suspension and an increase in the proportion of finer particles moving downstream from source to mouth. Only slight variations in texture could be observed down the river as a function of time and appeared to relate to freezing and melting of the Rhône and other headwater glaciers as the primary sediment source. Little variation was observed annually in the texture and composition of the sediment at the river mouth despite large changes in concentration between the high flow summer and low flow winter discharges. These findings are consistent with a well-mixed system in which the suspended sediments are directly related to the primary supply of material from the glaciers.     

Exposure and time dependent DNA strand breakage in hepatopancreas of green-lipped mussels (Perna viridis) exposed to Aroclor 1254, and mixtures of B[a]P and Aroclor 1254

Green-lipped mussels (Perna viridis) were exposed to Aroclor 1254 (0.5, 5 and 50 microgl(-1)) and a mixture of benzo[a]pyrene (B[a]P) and Aroclor 1254 (0.3+0.5 and 3+5 microgl(-1)) for 12 days. On day 0, 1, 3, 6 and 12, the levels of DNA strand breaks in the mussel hepatopancreas were monitored using an alkaline unwinding assay. The results were compared to the findings of a previous study in which the levels of DNA strand breakage in the same species were measured following exposure to various concentrations of B[a]P (0.3, 3 and 30 microgl(-1)). The results indicated that Aroclor 1254 at a concentration 相似文献   

Comparative effects of the blue green algae Nodularia spumigena and a lysed extract on detoxification and antioxidant enzymes in the green lipped mussel (Perna viridis)

Nodularia spumigena periodically proliferates to cause toxic algal blooms with some aquatic animals enduring and consuming high densities of the blue green algae or toxic lysis. N. spumigena contains toxic compounds such as nodularin and lipopolysaccharides. This current work investigates physiological effects of exposure from bloom conditions of N. spumigena cells and a post-bloom lysis. Biochemical and antioxidative biomarkers were comparatively studied over an acute 3-day exposure. In general, a post-bloom N. spumigena lysis caused opposite physiological responses to bloom densities of N. spumigena. Specifically, increases in glutathione (GSH) and glutathione peroxidase (GPx) and decreases in glutathione S-transferase (GST) were observed from the N. spumigena lysis. In contrast, N. spumigena cell densities decreased GSH and increased GST and lipid peroxidation (LPO) in mussels. Findings also suggest that at different stages of a toxic bloom, exposure may result in toxic stress to specific organs in the mussel.