H.A. Jenner

The valve movement response of mussels: a tool in biological monitoring

Biological sensors are becoming more important to monitor the quality of the aquatic environment. In this paper the valve movement response of freshwater (Dreissena polymorpha) and marine (Mytilus edulis) mussels is presented as a tool in monitoring studies. Examples of various methods for data storage and data treatment are presented, elucidating easier operation and lower detection limits. Several applications are mentioned, including an early warning system based on this valve movement response of mussels.

Chlorination by-products in chlorinated cooling water of some European coastal power stations

Chlorination by-products (CBPs) are formed as a result of the cnlorination of power station cooling water for anti-fouling purposes. Their production was studied at 10 coastal power stations in the UK, France and The Netherlands. Three categories of CBPs were determined: trihalomethanes; haloacetonitriles; and halophenols. Bromoform was the CBP most abundantly present in the effluents of all 10 power stations. At a mean chlorine dosage of 0.5–1.5 mg/litre (as Cl2) the mean bromoform concentration was 16.32 ± 2.10 μg/litre. The CBP found in second highest concentrations was dibromoacetonitrile (DBAN) with mean concentrations of 1.48 ± 0.56 μg/litre. Other CBPs detected were dibromochloromethane, bromodichloromethane and 2,4,6-trichlorophenol; concentrations of these three compounds were very low (< 1 μg/litre). At those sites at which bromoform was measured in the dispersing effluent plume it was found to behave as a conservative parameter (Significant direct correlation with plume ΔT).

The greening of the coasts: review of the Perna viridis success story.

The green mussel Perna viridis has been receiving a lot of attention from workers working in the research areas of intertidal ecology, aquaculture, pollution monitoring, biofouling, zoogeography and invasion biology. P. viridis is a remarkable species in terms of its ability to reach very high biomass levels, to withstand environmental fluctuations, to concentrate a variety of organic and inorganic environmental pollutants, to colonise artificial marine habitats and to invade new geographic territories. This review collates data available on salient aspects of the distribution, biology and ecology of P. viridis. It is argued that the remarkable success of P. viridis as an invasive species basically stems from its long larval duration, fast growth rate, high fecundity, early maturity, high productivity and ability to withstand fluctuating environmental conditions (temperature, salinity, water turbidity and pollutants). Relevant aspects of the data are compared with the data available for a similar species Perna perna, which too is an invasive species, but to a more limited extent.

How effective is intermittent chlorination to control adult mussel fouling in cooling water systems

Mussel control in cooling water systems is generally achieved by means of chlorination. Chlorine is applied continuously or intermittently, depending on cost and discharge criteria. In this paper, we examined whether mussels will be able to survive intermittent chlorination because of their ability to close their valves during periods of chlorination. Experiments were carried out using three common species of mussels: a freshwater mussel, Dreissena polymorpha, a brackish water mussel, Mytilopsis leucophaeata and a marine mussel, Mytilus edulis. The mussels were subjected to continuous or intermittent (4 h chlorination followed by 4 h no chlorination) chlorination at concentrations varying from 1 to 3 mg l(-1) and their responses (lethal and sublethal) were compared to those of control mussels. In addition, shell valve activity of mussels was monitored using a Mussel-monitor. Data clearly indicate that mussels shut their valves as soon as chlorine is detected in the environment and open only after chlorine dosing is stopped. However, under continuous chlorination mussels are constrained to keep the shell valves shut continuously. The mussels subjected to continuous chlorination at 1 mg l(-1) showed 100% mortality after 588 h (D. polymorpha), 966 h (Mytilus edulis) and 1104 h (Mytilopsis leucophaeata), while those subjected to intermittent chlorination at 1 mg l(-1) showed very little or no mortality during the same periods. Filtration rate, foot activity index and shell valve movement of D. polymorpha, Mytilopsis leucophaeata and Mytilus edulis decreased more than 90% at 1 mg l(-1) chlorine residual when compared to control. However, mussels subjected to intermittent chlorination showed a similar reduction (about 90%) in filtration rate, foot activity index and shell valve movement during chlorination and 3% during breaks in chlorination. The data indicate that intermittent chlorination between 1 and 3 mg l(-1) applied at 4 h on and 4 h off cycle is unlikely to control biofouling if mussels are the dominant fouling organisms.

Reproduction, growth rate and culture potential of the green mussel, Perna viridis (L.) in Edaiyur backwaters, east coast of India.

Abstract The green mussel Perna viridis is an edible mollusc with enormous culture potential. This paper presents data on the reproduction, spat settlement and growth rate of P. viridis in Edaiyur backwaters on the east coast of India. The mussels exhibit two spawning periods and temperature appears to regulate the onset of reproductive events. Spat settlement densities are greater in the adjacent coastal waters as compared to the backwaters. Growth rate data show that the mussels reach an average shell length of 83 mm in 1 year. The results also show that shell and meat weight exhibit different seasonal patterns of growth in Edaiyur backwaters. In rope culture, marketable size (50–60 mm shell length) was achieved in about 6 months with an annual production of 47 kg m −1 and biomass (wet meat weight) of 22 kg m −1 . The annual production values in Edaiyur backwaters are relatively higher than those reported from other parts of India. The present study suggests that Edaiyur backwaters represent a potential site for successful cultivation of P. viridis considering the availability of sustainable wild stocks of P. viridis and abundance of seed along with favourable environmental conditions.

Chlorination and mussel control in the cooling conduits of a tropical coastal power station

Abstract The rationale for the present study has been the continued problem of biofouling in the cooling conduits of Madras Atomic Power Station (Kalpakkam), in spite of intermittent chlorination used as a fouling control measure. A diver-assisted inspection of the tunnel proved that the green mussel, Perna viridis (L.) was the major component of the fouling community inside the cooling conduits. Maximum biomass value recorded was 211 kg/m 2 , observed inside the forebay shaft at a depth of 22.5 m. The total biomass of fouling in the entire tunnel system was estimated to be 578 tonnes, of which the contribution by P.viridis alone was 411 tonnes. High-level chlorination, followed by continuous low-level chlorination brought large quantities of sessile biomass from the tunnel to travelling water screens (TWS). A total biomass of about 187 tonnes of fouling debris was collected from TWS during February 1988 to January 1990. Of these, P.viridis accounted for 164 tonnes. The sizefrequency distribution of P.viridis collected on the TWS clearly showed that the appearance of young mussels (0–2 cm shell length) was correlated with the breeding pattern of green mussels in the adjacent coastal waters. The present study showed that intermittent chlorination is an ineffective method for mussel control in the power station cooling conduits. Continuous high-level chlorination is useful for dislodging established mussel communities from intake tunnels.

Duckweed Lemna minor as a tool for testing toxicity of coal residues and polluted sediments

Duckweed, Lemna minor, was used for testing single elements and leachates of coal ashes and sediments by expressing growth as surface coverage. The EC50 for the elements Cd, Cu, Zn, As(III), As(V), Se(IV), Se(VI), SeO2 were 0.86, 2.2, 4.4, 8.4, 297, 21, 67, 37 μM, respectively. Leachates were tested of pulverized coal fuel ash (PFA), including “low NOx” ashes, coal gasification slag (CGS), and, as a reference, the polluted sediments of a canal. The concentrations of elements in leachates of “low NOx” PFA were higher than those in leachates of conventional PFA. The leaching of anions from PFA was more quickly than the cations. CGS showed an absolutely minimal element leaching. Comparison of the effects of conventional PFA with sediments from Rotterdam harbor, River Rhine, and the canal shows PFA to be the far less toxic one. The sediment samples from the canal demonstrated strong growth inhibition, probably due to high zinc concentrations originating from industrial activity.

Tolerance of five species of tropical marine mussels to continuous chlorination

The paper examines the relative lethal and sublethal response of five important tropical marine mussels (Perna viridis, Perna perna, Brachidontes striatulus, Brachidontes variabilis and Modiolus philippinarum) to different chlorine concentrations varying from 0.25 to 15 mg l(-1). The mussels were observed to co-exist in the cooling water circuits of a coastal power station that adopted intermittent chlorination as a fouling control technique. The five mussel species showed, in response to chlorination, 100% mortality at significantly different exposure times, indicating significant species-specific variability in chlorine tolerance. For example, at 1 mg l(-1) residual chlorine, B. variabilis and P. viridis took 288 and 816 h, respectively, to achieve 100% mortality. The time taken for 100% mortality decreased with increasing chlorine residual concentration. The effect of mussel size (= mussel age) of P. viridis, P. perna, B. striatulus and M. philippinarum on mortality was significant between 1 and 5 mg l(-1) residual chlorine, with larger mussels showing greater resistance than smaller ones. All mussel species showed progressive reduction in physiological activities when chlorine residuals were increased from 0 to 1 mg l(-1). However, species-specific differences in the relative rate of physiological activities were observed. Accordingly, relative reduction in physiological activities in response to chlorination was the lowest in P. viridis and the highest in B. variabilis. The data clearly indicate significant differences in the lethal and sublethal responses of the five mussel species to chlorination. The results, therefore, suggest that for effective fouling control, chlorine treatment against mussels has to be employed judiciously, depending on the mussel species involved.

Factors influencing the upper temperature tolerances of three mussel species in a brackish water canal: Size, season and laboratory protocols

Mussels are the most problematic organisms encountered in the water intake systems of electrical power plants. Various fouling control measures are adopted, among which heat treatment is considered the relatively more attractive from economic and ecological points of view. Thermal tolerance experiments were carried out to determine the effects of mussel size (2 – 20 mm shell length), season (breeding vs non-breeding), nutritional status (fed vs non-fed), acclimation temperature (5 – 25°C) and acclimation salinity (1 – 35‰) on the mortality pattern of three important mussel species, viz. a freshwater mussel Dreissena polymorpha, a brackish water mussel Mytilopsis leucophaeata and a marine mussel Mytilus edulis under different temperatures (36 – 41°C). The mussels in the 10 mm size group exposed to 36°C showed 100% mortality after 38 min (D. polymorpha), 84 min (M. edulis) and 213 min (M. leucophaeata). The effect of mussel size on M. edulis and M. leucophaeata mortality at different temperatures was significant, with the largest size group of mussels showing greater resistance, while no significant size-dependence was observed in the case of D. polymorpha. All the three mussel species collected during the non-breeding season (November – April) were more tolerant (by about 40 – 45%) to temperature than those collected during breeding season (June – October). Nutritional status had no significant influence on the thermal tolerance of the three mussels; fed and non-fed mussels showed 100% mortality at comparable rates. Acclimation temperature had a significant effect on the mortality of all three species. Survival time at any given target temperature increased with increasing acclimation temperature. The acclimation salinity showed no significant effect on the thermal tolerance of the three mussel species. In comparison, M. leucophaeata was more tolerant to high temperature stress than the other two species. The present studies clearly show that various factors can influence the mortality of D. polymorpha, M. edulis and M. leucophaeata to elevated temperatures. The results, therefore, suggest that if heat treatment were to be used as a control measure for these mussels, it has to be employed judiciously, depending on the mussel species, mussel size, breeding season, water temperature and salinity.

Effects of low-level chlorination on zebra mussel, Dreissena polymorpha

Mortality pattern of different size groups (5-20 mm shell lengths) of the zebra mussel Dreissena polymorpha (Pallas), was studied in the laboratory under different chlorine concentrations (0.25-3.0 mgl(-1)). Results showed that exposure time for 100% mortality of mussels significantly decreased with increasing chlorine concentration. For example, mussels in the 10mm size group exposed to 0.25mg l(-1) chlorine residual took 1080h to reach 100% mortality whereas those exposed to 3 mg l(-1) chlorine took 252 h. All size groups (between 5 and 20 mm shell length) took identical exposure time to reach 100% mortality at given chlorine concentration (between 1 and 3mg l(-1)). The effect of acclimation temperature on D. polymorpha mortality in the presence of chlorine was significant. For example, 1026 h is required to reach 95% mortality using 0.5mg l(-1) residual chlorine at 10 degrees C, compared to 456h at 0.50 mg l(-1) chlorine and 25 degrees C. Resistance of D. polymorpha to chlorine appeared to be lower than that for other mussel species in The Netherlands viz., Mytilus edulis L. and Mytilopsis leucophaeata (Conrad). The present study also suggests that 100% mortality data for European populations of D. polymorpha at different chlorine concentrations are similar to those for the North American populations.