Presence Of Effluent Research Articles

Battle of the Bites: The Effect of Sewage Effluent Exposure on Mosquitofish Biocontrol of Mosquitoes in Residential Louisiana.

Mosquitofish, Gambusia affinis, are eponymous larval mosquito predators. Their ability to colonize and survive in habitats that are uninhabitable by other potential predators allows them to naturally manage larval mosquito populations in most ground pools they are present in. However, effluent from residential onsite wastewater treatment systems (OWTSs) appears to limit the presence of fish predators. This is especially problematic in Louisiana, where regulations allow the discharge of OWTS effluent into open drainage conveyances. To determine the effect of effluent on the capacity of mosquitofish for biocontrol in contaminated areas, we assessed the body condition metrics of populations from two effluent-exposed sites and two sites not exposed to effluent, determined the lethal effect of effluent-contaminated drainage water on fish, and measured the prey consumption rates in the presence of effluent. Female fish collected from effluent-impacted sites had a reduced somatic body condition and most females examined displayed masculinized anal fins resembling the male gonopodium structure. This trait was not seen in fish collected from the control sites and has not yet been documented in association with OWTSs or in the state of Louisiana. Fish from the control sites survived at effluent-contaminated water levels < 70%, and the prey clearance rates increased with dilution. Onsite wastewater treatment system effluent has significant effects on both the short- and long-term persistence of mosquitofish, their body composition, reproductive health, and larval mosquito consumption. These effects likely release mosquito larvae from suppression and may increase the threat of mosquito-transmitted pathogens in effluent-contaminated locations.

Simultaneous enhanced removal of pharmaceuticals and hormone from wastewaters using series combinations of ultra-violet irradiation, bioremediation, and adsorption technologies

Pharmaceuticals and hormones presence in effluent of conventional municipal wastewater treatment plants (WWTPs) have been widely reported. Medicinal mushrooms such as Ganoderma species and bentonite clay were recently found to have promising results in wastewater treatment with potential advantages in the removal of pharmaceuticals. Here we investigated a hybrid treatment comprising of three separate processes (no chemicals) i.e., UV irradiation, biological, adsorption (bentonite + dolomite) in a series to enhance the simultaneous removal pharmaceuticals and hormone from wastewaters (real and synthetic). In this study, fungal species Ganoderma lucidum (GLSB) and Ganoderma neo-japonicum (GJSG) are used separately in bioreactors. The work investigated removal efficiencies of four (4) pharmaceuticals and a hormone. The results showed that all investigated pharmaceuticals and hormone were removed in hybrid treatment during 54.5 h treatment. Both GLSB and GJSG reactor series treatments achieved maximum removal in both synthetic and real domestic wastewater. Overall, this study provides promising suggestions for the upgrade and design of WWTPs to simultaneous complete removal of pharmaceuticals and hormone. Present study is a beginning for future development of sustainable tertiary hybrid treatment process in addition to existing WWTPs processes to completely remove the emerging pollutants.

Assessing the impact of wastewater treatment works effluent on downstream water quality

The impact of wastewater treatment works (WwTW) effluent on downstream river water quality is of increasing concern, particularly owing to the presence in effluents of a range of trace substances. In the case of contamination by metals the question of bioavailability has recently been accounted for in setting water quality standards for several metals. In the UK over the past decade the Chemical Investigations Programme (CIP) has generated upstream and downstream river quality data as well as associated WwTW effluent monitoring for over 600 sites, for the main contaminants of regulatory interest under the Water Framework Directive. Data presented here show that at a local level WwTW discharges have little impact for many contaminants. Soluble reactive phosphorus, hexabromocyclododecane (HBCDD), cypermethrin, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been shown to be the principal substances where downstream concentrations were at least 10 % larger than the upstream value. Otherwise, poor compliance with riverine water quality standards tends to be associated with contamination at the river catchment scale, with corresponding implications for the nature of remedial actions that are likely to be successful. Compliance with water quality criteria for metals, taking account of bioavailability, is high overall.

Natural and Anthropogenic Geochemical Tracers to Investigate Residence Times and Groundwater–Surface-Water Interactions in an Urban Alluvial Aquifer

A multi-component geochemical dataset was collected from groundwater and surface-water bodies associated with the urban Fountain Creek alluvial aquifer, Colorado, USA, to facilitate analysis of recharge sources, geochemical interactions, and groundwater-residence times. Results indicate that groundwater can be separated into three distinct geochemical zones based on location within the flow system and proximity to surface water, and these zones can be used to infer sources of recharge and groundwater movement through the aquifer. Rare-earth-element concentrations and detections of wastewater-indicator compounds indicate the presence of effluent from wastewater-treatment plants in both groundwater and surface water. Effluent presence in groundwater indicates that streams in the area lose to groundwater in some seasons and are a source of focused groundwater recharge. Distributions of pharmaceuticals and wastewater-indicator compounds also inform an understanding of groundwater–surface-water interactions. Noble-gas isotopes corroborate rare-earth-element data in indicating geochemical evolution within the aquifer from recharge area to discharge area and qualitatively indicate variable groundwater-residence times and mixing with pre-modern groundwater. Quantitative groundwater-residence times calculated from 3H/3He, SF6, and lumped-parameter modeling generally are less than 20 years, but the presence of mixing with older groundwater of an unknown age is also indicated at selected locations. Future investigations would benefit by including groundwater-age tracers suited to quantification of mixing for both young (years to decades) and old (centuries and millennia) groundwater. This multi-faceted analysis facilitated development of a conceptual model for the investigated groundwater-flow system and illustrates the application of an encompassing suite of analytes in exploring hydrologic and geochemical interactions in complex systems.

Label-Free Ultrasensitive and Environment-Friendly Immunosensor Based on a Silica Optical Fiber for the Determination of Ciprofloxacin in Wastewater Samples.

Emerging contaminants, including pharmaceutical compounds, are receiving research attention as a result of their widespread presence in effluents and wastewater treatment plants (WWTPs). The antibiotic ciprofloxacin (CIP) is extensively employed to treat infections in animal and human medicine. Both CIP and its metabolites are common contaminants found in WWTPs. In this study, a label-free ultrasensitive U-bent optical fiber-based immunosensor for the determination of CIP in wastewater samples was developed using the properties of the conducting polymer polyaniline (PANI). The anti-CIP immunoglobulin G (IgG) was deposited on a silica optical fiber surface previously functionalized with PANI. Scanning electron microscopy and micro-Raman spectroscopy were used to investigate the surface of the immunosensor. The analysis of CIP in wastewater was performed without the use of an organic solvent or sample preparation steps, with only the sample dilution in saline buffer (pH = 7.4). The linear range for CIP was from 0.01 to 10,000 ng L-1. The detection limit was 3.30 × 10-3 ng L-1 and the quantification limit was 0.01 ng L-1. The immunosensor provided a high average recovery of 91% after spiking wastewater samples with CIP at a concentration of 9,100 ng L-1. The method was applied in triplicate to wastewater samples from Quebec (Canada), obtaining concentrations of 549 and 267 ng L-1. A comparison with a reference method showed no significant difference (t-test at 95% confidence). The new technique developed is selective, allowing a quantitative analysis of CIP in wastewater.

COPPER IMPROVES THE PRODUCTION OF LACCASE BY Pleurotus sajor-caju WITH ABILITY TO GROW ON EFFLUENTS OF THE CITRUS INDUSTRY

This research is aimed to evaluate the effect of copper on biomass growth, laccase activity and isoenzymes composition of Pleurotus sajor-caju, and its ability to grow on effluents of the citrus industry. The inhibitory effect of copper on growth was evidenced especially after 14 days of culture in the presence of the highest concentration of copper (1 mM) reducing almost three times its growth. The highest enzyme activity was reached at the 10th day of treatment, with ~ 53 U/L for the medium without copper and ~ 121 and ~ 68 U/L for medium supplemented with 0.5 and 1mM, respectively. Laccases in cell-free extracts obtained from culture added with copper showed to be more stable for more time at temperature changes. The optimum temperature for laccase activity increased from 50 to 60 oC by effect of copper while the optimal pH was 5 in all experiments. In gels, it was possible to observe two isoenzymes of 65 and 35 kDa whose expression varied according to incubation time. Moreover, the isoenzyme of low molecular weight was induced by the presence of effluent in solid medium. P. sajor-caju had the ability to grow on effluents from the citrus industry, showing tolerance and potential for waste treatment, constituting a possible alternative to biodegrade and reduce the contaminating impact of effluents.

Biomonitors to evaluate the toxic potential of urban solid waste landfill leachate

The accentuated increase in the production of solid urban waste (SUW) and the consequent accumulation of leachate in landfills increase the risk of environmental contamination. Biomonitors are used to assess the toxicity of pollutants on living organisms. In this study, the pollutant potential of leachate from SUW from a deactivated landfill was evaluated by bioassays with Lactuca sativa L. and Lycopersicon esculentum Mill., and the relationship between chemical characteristics of the effluent and biological parameters was analyzed. The effluent was tested in its raw form and diluted in distilled water at concentrations of 75 and 50%. The percentage of germination, root growth (RG), mitotic index (MI), chromosomal abnormalities index (CAI), and micronuclei frequency (MCN) were analyzed. In the presence of effluent, germination and MI decreased, while RG, CAI and MCN frequencies increased in relation to the negative control (distilled water) for both species. Lead, iron and zinc presented negative relation with seed germination for both species, with RG of L. sativa and MI of L. esculentum, as well as a positive relation with MCN frequency in the studied species. Because of its larger chromosomes, L. sativa is a more suitable biomonitor of SUW leachate toxicity than L. esculentum. Even though the landfill is deactivated, it is necessary to treat this effluent, in order to minimize environmental impacts.

Photo-biological degradation of Bisphenol A, UV/ZnO/Iodide process at the center of biological reactor

The goal of this study is to achieve zero waste with UV/Iodide/ZnO (UIZ)-based photocatalytic-biological reactor (IPBR) containing baffles was devised to degrade Bisphenol A (BPA), completely. Degradation efficiency of the UIZ, UV/Iodide, UV/ZnO, and only UV processes were determined as 97.4%, 78.4%, 71.4% and 51% respectively (reaction time: 30 min, BPA concentration: 200 mg L−1 and pH 7). According to additional study, the optimal Molar ratio was obtained 0.87:1:50 of Iodide /ZnO/BPA. Analyzing effluents of the UIZ reactor by liquid chromatography–mass spectroscopy after 5, and 10 min reaction time revealed that BPA decomposes to ring-shaped compounds convert to linear compounds within 10 min reaction time. Pseudo first-order kinetic model demonstrated that the observed rate constant (kobs) increased from 0.0728 to 0.1186 min-1 and the observed BPA degradation rate (robs) increases from 3.64 to 23.72 mg L-1 min-1 with increasing the BPA concentration. Meantime, the EEO (Electrical energy per order) values calculated according to the kinetics model results decreased from 11.60 to 7.12 kWh m-3, respectively (with the increase of BPA concentration from 50 to 200 mg L-1). Analysis of effluent dilution effect and toxicity assessment on Escherichia coli exhibited that no growth inhibition in presence of effluents that have been extracted after 10 min BPA degradation even after long incubation periods. Finally, feeding effluents of the UIZ photoreactor to biological treatment helped to reduce COD levels of 100, 200 and 300 mg L-1 BPA solutions to almost zero after 5, 9, 14 h aeration, respectively. Therefore, the proposed photo catalyst-biologic process is a promising technology for complete treatment of BPA containing wastewaters.

REMOVAL OF BPA FROM LANDFILL LEACHATES USING FENTON-ADSORPTION PROCESS

The objective of this investigation was to identify and quantify the presence of Bisphenol-A (BPA) in raw and treated leachates with the Fenton-adsorption process. BPA is used as a monomer to produce epoxy resins and it is a compound classified as endocrine disruptor. For this reason, it is important to quantify its presence in effluents that will be disposed to the environment to avoid damage to human health and other organisms. The Fenton-adsorption process consisted in the implementation of an advanced oxidation using H2O2 and FeSO4 applied to the raw leachate and subsequently the application of the adsorption process through a column packed with activated carbon. The quantification of BPA was carried out by gas chromatography coupled to mass spectrometry, using liquid-liquid and liquid-solid extraction methods. A recovery percentage study was carried out to validate the extraction methods. Finally, it was found that the leached evaluated contained >12 mg L-1 and at the end of the treatment its concentration was <0.0174 mg L-1.

Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river

Abstract. Anthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (14N, 15N) are often used to trace the sources of N fueling aquatic primary production, but effective use of this approach requires obtaining a reliable isotopic ratio for phytoplankton. In this study, we tested the use of flow cytometry to isolate phytoplankton from bulk particulate organic matter (POM) in a portion of the Sacramento River, California, during river-scale nutrient manipulation experiments that involved halting wastewater discharges high in ammonium (NH4+). Field samples were collected using a Lagrangian approach, allowing us to measure changes in phytoplankton N source in the presence and absence of wastewater-derived NH4+. Comparison of δ15N-POM and δ15N-phytoplankton (δ15N-PHY) revealed that their δ15N values followed broadly similar trends. However, after 3 days of downstream travel in the presence of wastewater treatment plant (WWTP) effluent, δ15N-POM and δ15N-PHY in the Sacramento River differed by as much as 7 ‰. Using a stable isotope mixing model approach, we estimated that in the presence of effluent between 40 and 90 % of phytoplankton N was derived from NH4+ after 3 days of downstream transport. An apparent gradual increase over time in the proportion of NH4+ in the phytoplankton N pool suggests that either very low phytoplankton growth rates resulted in an N turnover time that exceeded the travel time sampled during this study, or a portion of the phytoplankton community continued to access nitrate even in the presence of elevated NH4+ concentrations.

Detection of pathogenic Campylobacter, E. coli O157:H7 and Salmonella spp. in wastewater by PCR assay.

The aim of this study was the evaluation of the occurrence of pathogenic Campylobacter, Escherichia coli O157:H7, E. coli virulence genes and Salmonella spp. in different wastewater treatment plants (WWTPs) using a method based on an enrichment step and PCR. This method was sensitive enough to detect low levels (∼2CFU100ml(-1) of raw sewage) of all the investigated pathogens. In the WWTP samples, E. coli O157:H7 DNA and the eae gene were never found, but 33% of influents and effluents exhibited amplicons corresponding to Shiga-like toxin I. Twenty-five percent of the influent and 8% of the effluent exhibited the presence of Shiga-like toxin II. Campylobacter jejuni and C. coli DNA were identified in 50 and 25% of the influents and in 8 and 25% of the effluents, respectively. Salmonella spp. DNA was present in all the samples. Considering the results obtained, the method tested here offers a reliable and expeditious tool for evaluating the efficiency of the effluent treatment in order to mitigate contamination risk. Influent contamination by Salmonella spp. and Campylobacter spp. provides indirect information about their circulation; moreover, their presence in effluents underlines the role of WWTPs in the contamination of the receiving surface waters, which affects public health directly or indirectly.

Occurrence and Removal of Selected Pharmaceuticals and Personal Care Products in Three Wastewater-Treatment Plants

Residues of pharmaceuticals and personal care products (PPCPs) have been detected in surface waters. Incomplete removal of these compounds by wastewater-treatment plants (WWTPs) results in their presence in effluents and finally in surface waters. The occurrence and removal of four PPCPs was investigated in three WWTPs in Mississippi, USA, during a period of 1 year. Influent and effluent were sampled from the three WWTPs. Upstream and downstream samples of the WWTPs were also collected. All four PPCPs were detected in all influents where sulfamethoxazole showed the highest concentration levels with a median concentration of 1,640 ng/L, and carbamazepine was detected at the lowest level with a median concentration of 132 ng/L. Different PPCPs were removed to different extents varying from 99 to 100 %. Gemfibrozil showed the highest removal rates (73-100 %), whereas carbamazepine showed the lowest (-99 to -30 %). Secondary activated sludge in oxidation-ditch process showed remarkable PPCP-specific removal rates. Galaxolide was removed more than the other PPCPs, and sulfamethoxazole showed the least removal. Galaxolide was found to be a predominant PPCP in effluent among the PPCPs studied, and it was detected in all downstream (14.1-428.2 ng/L) and upstream (4.1-60.0 ng/L) samples. Sulfamethoxazole was removed more during the summer than the winter season. A clear increase of PPCP concentrations was observed in most downstream samples compared with upstream samples suggesting that discharges from WWTPs are the major source of PPCPs in surface waters.

A fly ash particles media filter for decentralized wastewater treatment systems

The contribution of this work is twofold: (i) estimation of the hydraulic operation of a coal combustion byproduct (CCBs) through its physical filtration by developing a physical model, and in broader terms, (ii) promoting the transformation of native disposal materials into beneficial materials. We developed an experiment which examines fly ash as a CCBs for its hydraulic performance, and runs in four main stages: First, fly ash in its natural state is tested in the laboratory to check if its effective size and uniformity coefficient match with recommendations in the literature; Then, fly ash of effective grain size as recommended in the literature is derived; Further, a physical model comprised of such a derived fly ash media filter and which supports horizontal flow of the effluent is developed; Finally, the hydraulic performance of the physical model comprised of derived fly ash in presence of effluent is evaluated and proved that fly ash is an appropriate media filter for hydraulic performance. The work clearly highlights the potential of the easy to reach and costless native fly ash as a media filter for treatment of wastewater which we consider a viable future work.

Soluble microbial products (SMPs) release in activated sludge systems: a review

This review discusses the characterization, production and implications of soluble microbial products (SMPs) in biological wastewater treatment. The precise definition of SMPs is open to talk about, but is currently regarded as “the pool of organic compounds that are released into solution from substrate metabolism and biomass decay”'. Some of the SMPs have been identified as humic acids, polysaccharides, proteins, amino acids, antibiotics, extracellular enzymes and structural components of cells and products of energy metabolism. They adversely affect the kinetic activity, flocculating and settling properties of sludge. This review outlines some important findings with regard to biodegradability and treatability of SMPs and also the effect of process parameters on their production. As SMPs are produced during biological treatment process, their trace amounts normally remain in the effluent that defines the highest COD removal efficiency. Their presence in effluent represents a high potential risk of toxic by-product formation during chlorine disinfection. Studies have indicated that among all wastewater post-treatment processes, the adsorption by granular activated carbon combined with biologically induced degradation is the most effective method for removal of SMPs. However, it may be concludes that the knowledge regarding SMPs is still under progress and more work is required to fully understand their contribution to the treatment process.

Early release of macrophage migration inhibitory factor after liver ischemia and reperfusion injury in rats

Macrophage migration inhibitory factor (MIF) is an important mediator of ischemia/reperfusion (I/R) injury in heart, brain and intestine. We previously demonstrated that MIF was released during warm/cold ischemia in vitro. However, the role of MIF in liver I/R injury remains unclear. We aimed to test the hypothesis that MIF acts as an early proinflammatory cytokine and could mediate the inflammatory injury in liver I/R. Rats (n=6 per group) were subjected to 90min warm ischemia followed by 0.5h, 6h and 24h reperfusion, respectively to liver transplantation (LTx) after 6h of cold ischemia followed by 24h of reperfusion. The expression of MIF, its receptor (cluster of differentiation 74 (CD74)) and the downstream inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)) were analyzed. Peritoneal macrophages were cultured for 6h alone or in the presence of effluent from cold-preserved livers or effluent depleted of MIF. Warm I/R increased hepatic MIF-mRNA and protein expression. MIF-protein was released into peripheral circulation in vivo with a maximum at 0.5h after reperfusion. Induction of MIF-expression was associated with the expression of proinflammatory cytokines and its receptor in both models. MIF released by isolated cold preserved livers, induced TNF-α and IL-1β production by cultured peritoneal macrophages. Intrahepatic upregulation of MIF, release into systemic circulation and the associated upregulation of the proinflammatory mediators suggest a role of MIF in mediating the inflammatory response to I/R injury. Blocking experiments will help to elucidate its role as potential molecular target for preventing hepatic I/R injury.

Substance Flow Analysis and Source Mapping of Chemical UV-filters

Chemical ultraviolet (UV)-filters are used in sunscreens to protect the skin from harmful UV radiation which may otherwise cause sunburns and skin cancer. Commonly used chemical UV-filters are known to cause endocrine disrupting effects in both aquatic and terrestrial animals as well as in human skin cells. Here, source mapping and substance flow analysis were applied to find the sources of six UV-filters (oxybenzone, avobenzone, 4-methylbenzylidene camphor, octyl methoxycinnamate, octyl dimethyl PABA and homosalate) and to identify the most dominant flows of these substances in Denmark. Urban water, composed of wastewater and surface waters, was found to be the primary recipient of UV-filters, whereby wastewater received an estimated 8.5–65 tonnes and surface waters received 7.1–51 tonnes in 2005. In wastewater treatment plants, their sorption onto sludge is perceived to be an important process and presence in effluents can be expected due to a lack of biodegradability. In addition, the use of UV-filters is expected to continue to increase significantly. Not all filters (e.g., octyl dimethyl PABA and homosalate) are used in Denmark. For example, 4-MBC is mainly associated with self-tanning liquids and private import of sunscreens.

The Use of Seaweed and Sugarcane Bagasse for the Biological Treatment of Metal-contaminated Waters Under Sulfate-reducing Conditions

When wetlands reach maximum treatment capacity to remove heavy metals, removal can still take place through precipitation as sulfide because of the biological reduction of sulfate. To achieve this goal, anaerobic conditions must be attained, a sulfate source must exist, and an adequate substrate for sulfate-reducing bacteria (SRB) is also required. In the present work, two ligneous-cellulosic materials, a brown seaweed and sugarcane bagasse, have been selected as substrates for SRB growth. Experiments were simultaneously conducted in continuous operation in two columns (0.57 L each), one containing the ligneous-cellulosic material plus inoculum and another containing only the ligneous-cellulosic material. In this work, the removal of cadmium and zinc was studied because of their presence in effluents from mining/metallurgy operations. Results obtained indicated that the inoculated reactor was able to treat the effluent more efficiently than the noninoculated reactor considering the time course of the tests.

Treatment of saline wastewaters from marine‐products processing factories by activated sludge reactor

An activated sludge reactor, operated at room temperature (20–30° C) was used to treat saline wastewaters generated by marine‐products industries. The system was operated continuously and the influence of the organic loading rates (OLRs), varying from 250 to 1000 mg COD 1−1 day−1, on chemical oxygen demand (COD) removal was investigated. The system, inoculated with NaCl‐acclimated culture, removed up to 98% and 88% of the influent COD concentrations at OLRs of 250 and 1000 mg COD l−1 day−1, respectively. Since the organic pollution is essentially composed of proteins, microorganisms, which produced proteolytic enzymes, were isolated from the activated sludge culture. One bacterium with the highest protease activity, identified as Bacillus cereus, was chosen for protease production in fishery wastewaters of different concentrations containing combined heads and viscera powder. Protease synthesis was strongly enhanced when cells were cultivated in two times diluted fishery wastewaters. The enhancement of protease synthesis could have been due to the presence in effluent of organic matters or salts, which stimulated the growth of the strain and protease production.

Crayfish induce a defensive shell shape in a freshwater snail

Abstract. This study was undertaken to determine whether intraspecific variation in shell morphology of the freshwater snail Elimia (=Goniobasis) livescens is caused by predator‐induced morphological changes. Juvenile snails from 3 populations were grown in the presence of effluent from predatory crayfish feeding on conspecific snails or in effluent from conspecific snails only. Snails from one population, Clear Creek, exhibited a predator‐induced morphology; they grew a narrow body whorl when exposed to the effluent from crayfish. Experimental feeding trials with crayfish and snails from Clear Creek were conducted to determine whether a narrow body whorl reduced predation in the presence of the crayfish Orconectes propinquus. In the feeding trials, snails with a narrow body whorl were eaten less frequently than snails with wider shells. However, there was no difference in overall size (length) between snails that were eaten and those that were not. Thus, juvenile snails from Clear Creek exposed to the presence of crayfish were induced to develop relatively narrow shells, which reduce the risk of successful attack by these crayfish. Hence the induced shell morphology is probably a defense against predation by crayfish.

Cardiac and behavioural responses of mussels to risk of predation by dogwhelks

We used noninvasive, infrared phototransducers to record continuously the heartbeat of common mussels,Mytilus edulis , experiencing successive phases of interaction with the predatory gastropod Nucella lapillus, from initial threat to attack and consumption. Coupling physiological monitoring with behavioural analysis allowed us to investigate in detail the responses of mussels to predation threat. Compared to values of normal feeding activity, heart rate increased significantly when mussels were in the presence of effluent from dogwhelks. When attacked by dogwhelks, mussels increased their heart rate further, together with the rate of valve gaping. Considering the heart rate as a reliable estimator of respiratory function, these cardiac responses might be a mechanism to compensate for increased energy demand in order to cope with predation hazard. If so, the theoretical importance of trading off energy balance against risk of predation is supported by our results. Cardiac and behavioural responses varied throughout the attack according to the penetration method adopted by dogwhelks. When mussels were attacked through a drilled hole, heart rate tended to increase and periods of cardiac pausing appeared close to the point of death. In contrast, mussels attacked by penetration between the valves showed decreasing heart rate throughout the attack, together with relatively earlier cessation of valve gaping and appearance of cardiac pausing. These differences clearly support the hypothesis that dogwhelks penetrating between the valves are able to induce muscular paralysis of prey by injecting toxins.