Upper temperature tolerances of exotic brackish-water mussel, Mytilopsis leucophaeata (Conrad): an experimental study

The dark false mussel, Mytilopsis leucophaeata is an important mussel colonising the brackish-water systems of temperate and subtropical regions. Of late it has earned notoriety as a biofouling species in industrial cooling water systems. However, there are no published data on the temperature tolerance of this species. This paper presents data on the upper temperature tolerance of this mussel from the view point of biofouling control using thermal methods. In addition to mortality, response of physiological activities such as oxygen consumption, filtration rate, foot activity and byssus thread production were also studied at temperatures varying from 5 to 35 degrees C. Experiments were also carried out to understand the effect of mussel size, breeding condition, nutritional status and acclimation conditions (temperature and salinity) on the mortality pattern. The physiological activities were significantly reduced at temperatures beyond 27.5 degrees C and ceased at 35 degrees C. In 20 mm size group mussels exposed to 37 degrees C, 50% mortality was observed after 85 min and 100% mortality after 113 min. The effect of mussel size on mortality at different temperatures was significant, with the larger size group mussels showing greater resistance. M. leucophaeata collected during the non-breeding season (December-April) were more tolerant to temperature than those collected during the breeding season (June-October). Nutritional status of the mussel had no significant influence on the thermal tolerance of the mussel: fed and starved (non-fed) mussels succumbed to temperature at comparable rates. The effect of acclimation temperature and acclimation salinity on M. leucophaeata mortality at different temperatures was significant. Survival time increased with increasing acclimation temperature and decreased with increasing salinity. In comparison with other co-occurring species such as Mytilus edulis and Dreissena polymorpha, M. leucophaeata appears to be more tolerant to high temperature stress.     

Lethal and sub-lethal effects of chlorination on green mussel Perna viridis in the context of biofouling control in a power plant cooling water system.

Continuous chlorination is a widely followed cooling water treatment practice used in the power industry to combat biofouling. The green mussel Perna viridis is one of the dominant fouling organisms ( > 70%) in the Madras Atomic Power Station. Mortality pattern as well as physiological responses such as oxygen consumption, filtration rate, byssus thread production and faecal matter production of three different size groups of this mussel were studied at different chlorination concentrations. At 0.7 mg l(-1) residual chlorine, 3-4 cm size mussels showed 100% mortality in 553.3 h while 8-9 cm size group mussels died within 588 h. At a relatively high level of residual chlorine (9.1 mg l(-1)), 100% mortality in 3-4 cm and 8-9 cm size groups took 94 and 114 h, respectively. All physiological activities studied showed a progressive reduction as chlorine residuals were increased from 0 to 0.55 mg l(-1). The data indicated that the green mussel can sense a residual chlorine level as low as < 0.15 mg l(-1) and complete valve closure occurs only at 0.55 mg l(-1). The paper also shows that the sub-lethal physiological responses are better indices than lethal responses in planning chlorination strategies.     

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.     

Environmental tolerance of Caprella mutica: implications for its distribution as a marine non-native species

Physiological tolerances limit the distribution of marine species, with geographical ranges being set by environmental factors, such as temperature and salinity, which affect the rates of vital processes and survival of marine ectotherms. The physiological tolerances of the non-native marine amphipod Caprella mutica were investigated in laboratory experiments. Adult C. mutica were collected from a fish farm on the west coast of Scotland and exposed to a range of temperatures and salinities for 48 h. C. mutica were tolerant of a broad range of temperature and salinity conditions, with 100% mortality at 30 degrees C (48 h LT50, 28.3+/-0.4 degrees C), and salinities lower than 16 (48 h LC50, 18.7+/-0.2). Although lethargic at low temperatures (2 degrees C), no mortality was observed, and the species is known to survive at temperatures as low as -1.8 degrees C. The upper LC(50) was greater than the highest salinity tested (40), thus it is unlikely that salinity will limit the distribution of C. mutica in open coastal waters. However, the species will be excluded from brackish water environments such as the heads of sea lochs or estuaries. The physiological tolerances of C. mutica are beyond the physical conditions experienced in its native or introduced range and are thus unlikely to be the primary factors limiting its present distribution and future spread.     

不同光-暗周期对企鹅珍珠贝足丝分泌的影响

企鹅珍珠贝(Pteria penguin)是生产附壳珍珠的大型海水经济贝类,依靠强壮的足丝将自身固定在硬质基质上,抵抗水流的冲击和抵御被捕食。足丝分泌和形状易受环境影响,本实验研究了三种光-暗周期(全黑暗组、6h光-暗组、12h光-暗组)对企鹅珍珠贝足丝分泌、足丝直径和足丝拉力的影响。结果表明:光照条件下6h光-暗组和12h光-暗组企鹅珍珠贝足丝首次附着率和足丝分泌数量显著低于全黑暗组(P<0.05);光照条件下几乎不分泌足丝,光照严重抑制了足丝分泌,抑制率最高可达100%,恢复黑暗条件后企鹅珍珠贝重新分泌足丝,且分泌数量增加,最多每小时增加(1.94±1.00)根;不同光-暗周期条件下企鹅珍珠贝0~24h、24~48h、48~72h期间足丝首次附着率和足丝分泌数量无显著性差异(P>0.05)。全黑暗条件下足丝远端直径(0.45±0.09)mm和近端直径(0.38±0.09)mm存在显著性差异(P<0.05),足丝直径发生改变;但不同光-暗周期条件下,企鹅珍珠贝足丝远端、中端和近端直径无显著性差异(P>0.05)。全黑暗组、6h光-暗组、12h光-暗组中,企鹅珍珠贝单根足丝拉力分别为(3.40±2.76)N、(2.68±1.10)N、(3.86±2.05)N,三种光-暗周期条件下足丝的拉力无显著性差异(P>0.05)。综上,光照会显著抑制企鹅珍珠贝足丝的分泌,但一旦恢复黑暗条件,企鹅珍珠贝可重新分泌足丝,新足丝的拉力和直径不受影响;不同光-暗周期不会对企鹅珍珠贝的足丝附着、足丝直径和足丝拉力造成显著性影响。研究结果可以为企鹅珍珠贝的野外吊养和游离珠生产提供基础资料。     

Mussel colonization of a high flow artificial benthic habitat: byssogenesis holds the key

Water flow is an important characteristic determining the settlement and growth of macro-invertebrates in the marine environment. Intake systems of coastal power stations offer a unique opportunity to study the effect of water flow on benthic organisms under field conditions. The cooling water intake system of a tropical coastal power station is used as an experimental facility to study the effect of flow on the recruitment and growth of three mussel species, viz, Brachidontes variabilis, B. striatulus, and Modiolus philippinarum. The study was prompted by earlier observation that these mussels were numerically abundant in the biofouling community present inside the seawater intake tunnel of the power station, even though their occurrence in the benthic community in the coastal waters outside was only nominal. Recruitment data showed that the three mussel species very successfully colonised surfaces exposed to the intake mouth (characterised by relatively high flow) of the power station. Significant difference was observed in the recruitment recorded at the intake point and the ambient environment outside. Under high flow condition, the growth rates of all the three mussel species were uniformly enhanced. It is argued that recruitment of the different species is related to the number of byssus threads produced by each mussel and the strength of the byssus threads. The results indicate that byssus number and byssus strength of the mussels are important criteria that decide successful colonization and establishment in high flow environments.     

Effect of temperature and size on metallothionein synthesis in the gill of Mytilus galloprovincialis exposed to cadmium

Although the degree of metal contamination is expected to be a primary determinant of metallothionein (MT) induction in marine mussels, at least at polluted sites, variability caused by temperature, and biotic factors such as size, may need to be considered when interpreting field data. To test the effects of these variables, mussels, Mytilus galloprovincialis, of different sizes (small: 3.5 +/- 0.5 cm and large: 5.2 +/- 0.7 cm) were exposed to Cd (100 microg l(-1)) at different water temperatures (5, 18 and 25 degrees C) for 34 days. Resultant Cd and MT concentrations in gills were shown to be size dependent and increased significantly with temperature. At the highest temperature tested (25 degrees C) there appears to be a disproportionate effect on Cd accumulation, which raises MT synthesis to exceptionally high levels. The effect of size on MT concentrations was also temperature-dependent: at 18 and 25 degrees C, large mussels exhibited higher MT levels than smaller individuals, whilst at 5 degrees C there were no significant differences between contaminated and control mussels, in either size-group, as a result of the reduced level of MT production at this temperature. When considering the use of MT levels in mussels as a biochemical indicator of metal contamination, the potential influence of factors such as size and temperature on MT-metal relationships needs to be considered. Samples should be of uniform size as far as possible, and collection should be limited to a fixed season (avoiding climatic extremes) to ensure that the effects of these factors on baseline levels of MT is minimised.     

厦门港船蛆Teredo navalis数量的时空变化

本文根据1984年3月至1985年2月在厦门港中挂放杉木、松木和柯木试板,研究该港船蛆Teredo navalis数量的时空变化,并讨论了不同污损生物、水温、盐度等对船蛆密度的影响。     

Effects of the toxic dinoflagellate Alexandrium tamarense on the greenshell mussel Perna canaliculus

Abstract

Oxygen consumption, grazing rate, and byssus production of the greenshell mussel Perna canaliculus were measured following exposure to bloom concentrations (10⁶ cells l^?1 ) of a toxic clone of the dinoflagellate AIexandrium tamarense (GT429), using anon‐toxic clone of the same species (PLY173) as control. Following feeding for 1 h on GT429, mussels (dry weight 54–127 mg) showed significantly increased oxygen uptake at 15°C (0.08 μl O₂ (mg dry tissue weight)^?1 ) compared with control mussels. However, following 24 h recovery, oxygen uptake was similar to initial values in all experimental conditions. The grazing rate of P. canaliculus fed upon toxic clone GT429 was 4.58 ± 0.76 cells mg^?1 h^?1 compared with 1.99 ± 0.47 cells mg^?1 h^?1 for PLY173. On exposure to A. tamarense, mussels maintained normal opening behaviour and there was no change in the byssus production over 24 h. It was concluded that P. canaliculus showed no dramatic physiological effects following short‐term feeding on the toxic strain of A. tamarense. During 2 weeks’ exposure to twice daily bloom concentrations of GT429, there was no mussel mortality. Toxicity in the tissues was 1295 μg STX equivalent per 100 g tissue, levels at which these mussels would be unsuitable for human or animal consumption.     

Total oxyradical scavenging capacity and cell membrane stability of haemocytes of the Arctic scallop,Chlamys islandicus,following benzo(a)pyrene exposure

Industrial activities, notably oil and gas industries, are expanding in the Arctic. Most of the biomarkers were developed using temperate organisms living at temperatures above 10 degrees C. Little is known about the biomarker responses of organisms living between -1.88 and 5 degrees C. Therefore, assessment of the toxicity of chemicals to cold-water adapted species is required. In this study, the Arctic scallop, Chlamys islandicus, was selected as a key species for bio-monitoring because of wide distribution in Arctic waters and its commercial value. Test animals, stored in seawater at 2 degrees C, were injected with benzo(a)pyrene (diluted in cod liver oil 5 mg ml(-1)) in the adductor muscle every 24 h for four days giving a final dose of 0, 74 and 90.6 mg kg(-1) wet weight for control, low and high dose, respectively. The biomarkers used were total oxyradical scavenging capacity (TOSC) in the digestive gland and cell membrane stability of haemocytes. TOSC values were significantly reduced (ca. 30%) in exposed groups (P < 0.05), indicating a depletion in oxyradical molecular scavengers. The antioxidant defences appeared to be overwhelmed by the reactive oxygen species as the plasma membranes of haemocytes were destabilised (P < 0.05) probably due to lipid peroxidation. These data indicate that reactive oxygen species (ROS) were produced by Arctic scallops via the metabolisation of benzo(a)pyrene at 2 degrees C.     

Temperature-dependent physiological response of Carcinus maenas exposed to copper

The effect of temperature on the heart rate (fH) of Carcinus maenas exposed to a sublethal nominal concentration (0.5 mg l(-1)) of copper is reported. Adult, intermoult males (4 cm carapace width) were collected from Stavanger Fjord (Norway) in August (seawater TEMPERATURE=17 degrees C) and maintained in the laboratory (fed ad libitum) at 5, 15 and 25 degrees C for 7 days. Following this holding period, crabs were exposed to waterborne copper at the same temperature. After 3 days of exposure, individual fH was measured using the non-invasive Computer Aided Physiological MONitoring system (CAPMON) method. Copper-exposed individuals demonstrated significantly increased fH compared with controls at 5 and 25 degrees C (P<0.01). It is inferred that physiological function in C. maenas may be more vulnerable to copper contamination at seasonal temperature extremes (5 and 25 degrees C) than at the 'standard' test temperature (15 degrees C). Additionally, cardiac arrest observed at 5 degrees C is interpreted as a physiological response to limit copper uptake while the erratic fH in the 25 degrees C group reflected enhanced copper toxicity.     

A growth model for a hyalid amphipod Hyale perieri in the coastal water of Alexandria (Egypt)

Abstract-The growth rate of the hyalid amphipod Hyale perieri was studied on the bases of Ikeda'sgrowth model which is based on the inter moult period (IP) and moult increament (ΔBL). To applythis approach, laboratory experiments were carried out at three temperatures regimes (15℃, 20℃,25℃) to gain accurate data of IP and BL. The total number of specimens used in this study was 86 at15℃, 24 at 20℃ and 70 at 25℃. The number of flagellar segments of both antennae of the Hyaleperieri could not be used as an index of growth (instar criterion). The obtained results indicated that,the predicted IP of the specimens was inversely related to temperature and in good agreement with theobserved values at the experimental temperatures. IP data obtained from laboratory-reared specimes arecombined with ΔBL data to establish a growth model for Hyale perieri from its release from the mar-supium (1.64 mm BL) to the maximum size (12.67 mm BL) as a function of temperature. The maxi-mum numbers of consecutive moults     

莱州湾夏季浮游桡足类的摄食研究

于１９９７年７月有（１９－２４日）和小湖（２６－３０日）期间在莱州湾对不同大小桡足类自然群体（大型：〉５００ｍｍ,小型：２００－５００ｍｍ）的分布及肠道色素含量进行了现场测定,并在一个４８ｈ连续观测站（Ａ４）进行了肠道排空率和摄食节律实验。结果表明,浮动物肠道色素含量随个体的增大而增加,大型桡足类存在着一定的昼夜摄食节律,摄食高峰出现在夜间,小型桡足类摄食切律不明显。Ａ４站测得的桡足类摄食结果表明     

天津厚蟹对盐度和温度的耐受性

研究了天津厚蟹Helice tientsinensis对盐度和温度的耐受性。天津厚蟹对盐度的耐受能力极强,在温度9~34℃盐度为0的淡水介质中均能存活96h以上;在10℃、20℃及30℃的高渗介质中暴露96h后,天津厚蟹全部存活的盐度分别是65、56和50,全部死亡的盐度分别为83、74和68。天津厚蟹对低温的耐受力较强,在0、30和50盐度水平下,耐受低温的能力差别较大,能耐受96h的最低温度分别是9℃、2℃和6℃。天津厚蟹对高温也有较强的耐受能力,在0、30和50盐度水平下,分别在34℃、36℃和35℃下能耐受96h;盐度50温度38℃时,在开始的24h内无死亡,但48h后死亡率急剧上升,同样规律也出现在30和0溶液中,前者温度是39℃,后者为35℃。研究结果还表明盐度和温度的交互效应显著,二者的交互作用对天津厚蟹的存活亦有显著性影响(P0.05),温度升高(从10℃到20℃再到30℃)致使其耐盐能力显著下降,而盐度的剧烈变化(从30到50或从30到0)也致使其耐温能力显著下降。     

Low-temperature incubation of walleye pollock (Theragra chalcogramma) eggs from the southeast Bering Sea shelf and Shelikof Strait, Gulf of Alaska

To determine the effect of low water temperature on development, walleye pollock (Theragra chalcogramma) eggs from the Bering Sea were reared at −0.6°C, 0.4°C, 2.0°C, and 3.8°C. One group of eggs was reared at 3.9°C under a diel light cycle (14 h light, 10 h dark) to observe the effect of light on development and hatching. Development was normal for all temperatures except −0.6°C; abnormal development of the tail and lack of development of eyes occurred in some embryos. Time to 50% hatch was 820, 620, and 424 h at 0.4°C, 2.0°C, and 3.8°C. Eggs incubated in diel light at 3.9°C developed at the same rate as eggs incubated in constant dark at 3.8°C, but required an additional 72 h to reach 50% hatch. A piece-wise regression model was generated to predict egg age for incubation temperatures of −0.6°C to 3.8°C. For temperatures recorded in the southeastern Bering Sea 1995–1998, the model predicted incubation periods for walleye pollock eggs that varied by 13 days between the warmest and coldest years.Walleye pollock eggs from Shelikof Strait, Alaska, were incubated at 0.2°C, 1.8°C, and 2.8°C. Development was normal for all temperatures. A piece-wise regression model (as above) was generated for incubation temperatures 0.2–2.8°C. When the regression models were compared, Bering Sea eggs (1.4–1.7 mm in diameter), required more time for development prior to hatch than Shelikof Strait eggs (1.2–1.3 mm in diameter) at 1.8°C and 2.8°C. However, for temperatures 0.2–2.0°C, Bering Sea walleye pollock began hatching earlier and at a developmentally younger age than Shelikof Strait walleye pollock.     

Effects of temperature on scope for growth and accumulation of Cd, Co, Cu and Pb by the marine bivalve Mytilus edulis

In many aquatic organisms including Mytilus edulis, the role of temperature on bioaccumulation of metals is still not clearly understood. In this study, uptake and accumulation of Cu, Co, Cd and Pb in mussels were investigated at different temperatures (6-26 degrees C). Results from exposure of isolated gills showed a positive relationship between temperature and metal uptake. But in whole organism experiments, only the accumulations of non-essential metals (Cd, Pb) showed a similar trend while the two essential metals Co and Cu were independent and inversely related to temperature, respectively. With exception of Cu, elimination process appeared to be independent of temperature. The study also showed that neither changes in scope for growth (SFG) of mussels nor chemical speciation could fully account for the observed temperature-effects. Overall, these results suggest that fundamentally (i.e. at epithelial membranes), temperature-effects on uptake are largely due to changes in solution chemistry and physical kinetics, which favours higher uptake at high temperature. But at whole organism level, complex physiological responses appears to mask the relationship, particularly for biologically essential metals like copper.     

印度洋深海热液区贻贝足丝结构和性能特征研究

贻贝营半固着生活,依靠足丝将自己牢固地黏附在底物上.足丝的结构和性能对贻贝的正常生命活动至关重要.为研究热液区极端环境下深海贻贝足丝的结构和性能,采集了印度洋龙旂深海热液区的贻贝(Bathymodiolus marisindicus)足丝,对其力学特性、结构特征和组分进行了分析.力学性能测试发现与近海贻贝(Mytilu...     

The combined effect of copper and hydrocarbons on the length growth of Mytilus edulis

The combined effect of copper and North Sea crude oil is tested on juvenile Mytilus edulis. Dissolved CuSO₄ x 5H₂O is added to the seawater in concentrations of 3 and 6 μg Cu litre^-1. Crude oil, microencapsulated in a gelatine/acacia structure, is added in concentrations of 1·5 and 3·0 mg oil litre^-1. The shell length growth is measured every 24 h with laser diffraction. Linear effects were observed for single components within 24 h of exposure and significant antagonistic interaction appeared within 48 h. Reduced growth rate coincided with reduced filtering and defaecation, and reduced byssus production.     

Ecophysiological Studies of the Adriatic Seaweed, Fucus virsoides

Abstract. The Adriatic brown macroalga Fucus virsoides (DON.) J. Ac (Fucales, Phaeophyceae) was investigated with particular respect to basic physiological features such as photosynthesis, dark carbon fixation, and respiration. Values obtained are expressed in various reference systems. Chemical composition of the fronds and physiological activity (photosynthesis/dark fixation along with the respective carboxytating enzymes (ribulose-1,5-bisphophate carboxylase and phosphoenol-pyruvate carboxykinase) show longitudinal profiles. Temperature characteristics of photosynthesis in long-term adapted specimens indicate reduced productivity at temperatures exceeding 20 °C. Photosynthesis during atmospheric exposure is markedly increased under moderate desiccation. Photosynthetic rates steadily decline under reduced salinity of the incubation medium, while respiration is stimulated. Net primary productivity of a F. virsoides stand at 15 °C ambient average temperature, tidal exposure for maximally 2–3 hours and light-dark regime = 12: 12 is calculated as 4.8-5.4 g C m^-2d-1. Culture experiments with polluted incubation media provide evidence that excessive nutrients including nitrate and phosphate as well as high concentrations of heavy metals (Zn, Co, Mn) cause severe growth-rate reduction which may account for the steady decrease of F. virsoides in its natural habitat. The results are discussed with emphasis on the autecology of F. virsoides and its relationships to Atlantic representatives of the genus.     

Growth performance and physiological parameters of the second generation selected and control groups of Pinctada martensii

In May of 2007,the second generation selected (SS) and control (SC) groups of pearl oyster Pinctada martensii were established by selecting 10% breeders with the largest and mean shell length,respectively,from the first generation selected group.Growth performance of the SS and SC groups were compared on the basis of measurement data at Days 8,18,60,95,195 and 365.On Day 365,100 individuals (60.0–75.0 mm at shell length) were sampled from each group and then subjected to the experiment where physiological parameters such as filtrate rate,oxygen consumption and ammonia excretion were measured at 15,20,25 and 30°C.The results show that the SS group had significantly larger mean shell length and shell height than the SC group at Days 8,18,60,95,195 and 365 (P <0.05).The genetic gains at different ages varied from 6.0% to 17.0% for shell length and 5.7% to 14.6% for shell height,respectively.At 15,20,25 and 30 ° C,the SS groups had significantly larger filtrate rate than the SC group (P <0.05).At 15 and 25 °C,the differences in oxygen consumption rate between the SS and SC groups were not significant (P >0.05).At 20 and 30 °C,however,the oxygen consumption rate of the SS group was significantly larger than the SC group (P <0.05).At 15,20,25 and 30 °C,there were no significant differences in ammonia excretion rate between the SS and SC groups (P >0.05).The present results indicate that there existed considerable genetic variability in the base population and a further selection could be likely fruitful.Mass selection for faster growth might produce animals that had higher intake of metabolizable energy by virtue of faster filtrating behavior.