Effect Temperature And Salinity On The Toxicity Arsenic To Three .
MARINE ECOLOGY - PROGRESS SERIESMar. Ecol. Prog. Ser.Published July 11Effect of temperature and salinity on the toxicity ofarsenic to three estuarine invertebrates(Corophium v01utator, Macoma balthica,Tubifexcostatus)V. Bryant, D. M. Newbery, D. S. McLusky & R. CampbellDepartment of Biological Science, The University, Stirling, Scotland FK9 4LA, United KingdomABSTRACT: Acute toxicity of pentavalent arsenic to 3 estuarine invertebrates (Corophium volutator,Macoma balthica, Tubitex costatus) has been studied at 3 temperatures (5, 10, 15OC) and a range ofsalinities (5 to 35 %o, in 5 %O increments), at time intervals u p to 384 h. Median survival times decreasedas temperature and concentrat onof arsenic increased, but salinity changes had no significant effect.From analysis of variance, significant factors and their interactions were n c l u d e din response surfacemodels for C. volutator and M. balthica separately. Results are compared with the limited datapreviously published. It is emphasized that environmental temperature should be considered whenevaluating toxicity of arsenic in the estuarine environment.INTRODUCTIONAlthough organisms generally encounter high concentrations of arsenic only as a result of anthropogenicactivities, there is a lack of information about its toxicity. Acute toxicity data for arsenic for marine animalsare limited and no information is available on theeffects of temperature and salinity on the toxicity ofarsenic, although these environmental variables areknown to significantly affect the toxicity of other heavymetals such as cadmium (Theede et al. 1979),mercury(Vernberg et al. 1974) and chromium (Bryant et al.1984). Unlu & Fowler (1979) studied the effect of temperature, salinity, arsenic concentration and body sizeon arsenic accumulation and elimination processes onthe mussel Mytilus galloprovincalis. They found thatincreased temperature enhanced both uptake and lossof arsenic. Mussels in low salinity seawater accumulated 3 times more arsenic than those held at fullstrength seawater, but arsenic loss was much lessaffected by salinity.The present study was undertaken to establish theeffect of salinity and temperature on arsenic toxicity to3 species of invertebrates which are of ecologicalimportance in European estuaries: the amphipodCorophium volutator Pallas, the bivalve MacomaO Inter-Research/Printed in F. R. Germanybalthica (L.) and the oligochaete annelid Tubifexcostatus (Claparede).The latter is commonly found inorganically-enriched estuarine sediments and hasbeen found living close to an arsenic discharge in anestuary (Mance pers. comm.). The levels of arsenicused in the experiments reflect the concentrationswhich have been measured in Mance's study in agrossly polluted area rather than the low level of2 pg 1-l or ppb which is a typical value for nearshoreMediterranean waters (Fowler & Unlu 1978).MATERIALS AND METHODSCorophium volutator and Macoma balthica were collected from the 'unpolluted' Tay estuary, at Tayport,which has a salinity range of 11 to 32 %O (Khayrallah &Jones 1975). Tubifex costatus was collected from theForth estuary at Alloa and Cambus, which has a salinity range of 4 to 15 % (McLusky et al. 1980); this area issubject to organic enrichment but not to metal enrichment. Experiments were conducted in a constant temperature room at 5, 10, 15 "C ( 0.5 C"), with a regimeof 12 h light, 12 h darkness. The acute toxicity of pentavalent arsenic (as sodium arsenate) was determinedusing static tests following standard protocol (Anony-
Mar. Ecol. Prog. Ser 24: 129-137, 1985130mous 1980). Stock solutions of Analar gradeNaHAsO,.?H,O were prepared in water of the appropriate salinity, and nominal concentrations of test solution obtained by dilution. Saline solutions were prepared by dilution of natural seawater with deionizedwater; 35 %O salinity was prepared by the addition ofGerrard's sea salt to natural seawater.The experiment for Corophium volutatorhad a 3 X 8X 5 factorial design, with temperatures of 5, 10 and15"C, arsenic concentrations of 1, 2, 4, 8 , 16, 32, 64 and128 ppm ( controls) a n d salinities of 5 , 10, 15, 25 and35 %o. The experimental design for Macoma balthicawas a 3 X 7 X 3 factorial with the same temperaturesas above, arsenic concentrations of 15, 30, 60, 125, 250,500 a n d 1,000 ppm ( controls) and salinities of 15, 25and 35 %o. The experiment for Tubifex costatus had a3 X 3 X 3 factorial design with the same temperaturesas above, arsenic concentrations of 250, 500 and1,000 ppm ( controls) and salinities of 5, 15 a n d 25 %.M. balthica is unable to survive salinities of less than15 Yw, a n d T. costatus is unable to survive salinitiesabove 25 %o for longer than 24 h. Animals were fullyacclimated to the appropriate salinity and temperaturecombination for 5 d before testing. Experiments wereconducted at the appropriate season (e.g. 5 C experiments in winter). The oxygen concentration, pH, temperature and salinity in the test vessels were monitoredregularly. Over a 24 h period p H did not vary by morethan 0.5 in any vessel, and dissolved oxygen did notdrop below 75 % of air saturation. Twenty individualsof each species were used for each combination oflevels of temperature, salinity and arsenic. Sterile sandwas provided as substrate in all test vessels and nofood was provided throughout the experiment. Vesselswere examined, dead specimens removed and testsolutions changed daily for 384 h. Arsenic concentrations are nominal concentrations.At each time interval the cumulative % mortalitywas calculated following the method of Lloyd (1979).This value (expressed as probits) was plotted as afunction of time (expressed logarithmically) directlyonto logarithmic-probability graph paper for each ofthe concentrations of arsenic used. A straight line wasfitted by eye to each set of data, giving greater weightto those values between 25 and 75 % response. Timefor 50 % mortality, the median period of survival(LT,,), was then read from the graph (Litchfield 1949).Concentration-response curves were plotted on double-log paper using the LT,, values calculated for eacharsenic concentration at each temperature and salinitycombination, and a straight line fitted through the databy eye. (The data were sufficiently close to a linear fitnot to warrant regression analysis.) The median lethalconcentration (LC,,) for time periods of 24, 48, 96, 192and 384 h was read from each graph.STATISTICAL ANALYSISThree-factor analysis of variance of untransformedLT,, values was partitioned into linear and quadraticeffects for the main factors (temperature, concentrationand salinity) and their second order interactions. Sincethere were no replicates, the third order interactionwas taken as the error term (Davies 1979). Corophiumvolutator and Macoma balthica data were analysedseparately. Those terms which were significant atP 9 0.01 were included in a response surface model foreach species [Tubifexcostatus data could not be analysed in a similar way because the data set for thisspecies was incomplete]. Coefficients for the termswere found by multiple regression and the resultingequations used to draw isopleths of LT,,. Theseresponse surface models were used only to displaysignificant effects and their interactions in a graphicalform. We make no inferences about the precise biological meaning of the numerical values of the coefficients(see Schnute & McKennell 1984), nor do w e attempt tolocate response optima from these equations.Table 1. Corophium volutator. Median survlval times, LT,, ( h ) , derived graphically at 5, 10 and 15"C, 5 to 35%0,and arsenicconcentrations of 1 to 128 ppmConcentration(PP )12481632641285%5 "C10%o 15%a 25%35%0320 384 384 384 384175 384 384 384 384175300 384 38434017520023023027017090140145 13058100115115130467670909066365046705x010 C10% 1 5 % 25%a 35% 384 384 384 384 384165 380 384330310140 28029024026085130150115 11262807474966030565266333042483418172429305%a15 "C1O%o 1 5 % 25%35Yw3502401609054382915310 384 220220200 170115140 27
Bryant et al.: Tox cityof arsenic to three estuarine nvertebrateslog concentrationlog concentrationppm131ppmFig. 1. Corophium volutator. Change in median survival time. LT,, (h), with increasing concentration of arsenic at: (a) 3temperature levels; (b)5 salinity levels/lRESULTSCorophium volutatorMedian survival time (LT,,) of Corophium volutatordecreased with increasing arsenic concentration for allcombinations of temperature a n d salinity (Table l ;Fig. 1). At any one concentration LT,, generally decreased with increasing temperature but it altered verylittle with increasing salinity. This pattern of arsenictoxicity is illustrated well by the combined effect oftemperature and salinity on median survival time atthe concentration of 16 ppm (Fig. 2).Median lethal concentrations (LC5,) of arsenic toCorophium volutator under all experimental conditions tested are shown in Table 2. At all salinitiestested, 48h LC,, values were all greater than 96 hvalues, which were in turn greater than 192h values.The small effect that salinity has on the toxicity ofarsenic a t salinities greater than 10 %O compared to theeffect of temperature is clearly demonstrated in Fig. 3.The analysis of variance of median survival timesdata for Corophium volutator3, shows that thelinear effects of both temperature and arsenic concentration, and the quadratic effect of concentration sig-l35 i 2. ity on,Temperature C volulator, Effect of temperature and salinhsurvival time, LT,, (h), at arsenic concentration16 P P j
Mar. Ecol. Prog. Ser. 24: 129-137, 1985Table 2. Corophium volutator. Median lethal concentrations, LC,, of arsenic (pprn), at 5, 10 and 15 "C, and 5 to 35 %Ofor exposuretimes of 48 to 192 hExposuretime (h)5Yw10%5 "C15960 25%3.5%5%nificantly affected median survival time, but that thelinear and quadratic effects of salinity had no significant effect on median survival time. In addition none ofthe interactive terms was significant at the 1 % level(P 0.01), indicating no important 2-way interactionsbetween temperature, concentration and salinity. Theresponse surface equation was:where T temperature ("C); C concentration ofarsenic (ppm). As no interaction terms were significant, isopleth diagrams are not shown. The C and C*terms together approximate a hyperbolic (Schnute &McKinnell 1984) decrease in LT5, with concentration(Fig. 1). An optimum in LT,, with concentration is notinferred.Macoma balthicaFor each of the combinations of salinity and temperature, median survival time (LT,,) of Macoma balthicadecreased with increasing arsenic concentration(Table 4; Fig. 4). The combined effect of temperatureand salinity levels on LT,, at the arsenic concentrationof 15 ppm (Fig. 5) illustrates the general pattern ofresponse. Median survival time decreased withincreasing temperature, but increasing salinity had10%10 C15% 25%35%5%15 "C10%0 15560 25%35%little effect at all arsenic concentrations; a result similar to that obtained for Corophium volutator.Median lethal concentrations LC,, for Macomabalthica (Table 5) show that all 96 h values were atleast 4 tlmes greater than the 192h values. Althoughthere was some variation in LC,, with changing salinity, there was no clear trend, whilst temperature had afar greater effect on LC,,.Analysis of variance of the median survival times(Table 6) highlighted significant linear effects of temperature and concentration and a quadratic effect ofconcentration. Both linear and quadratic effects ofsalinity were not significant ( P 0.01). However, thelinear-linear interaction between concentration andtemperature was significant ( P 0.01), indicating thatthe effect of each of these variables on LT5, alters withthe level of the other variable. The response surfaceequation was: LT,, 404.1 - 15.73 T - 0.7026 C0.0003883 C*0.01432 TC(2)(R2 78.9 % ; F 12.43; df 4 , 58, P 0.001)where T, C temperature and concentration respectively (as for the Corophium model above).Fig. 6 shows the response surface isopleths for theeffect of concentration and temperature on LT,, valuesfor Macoma balthica at 15 %O salin ty.Maximum LTsovalues occur at combinations of low levels of bothtemperature and arsenic concentration. As tempera-mm000-g'O-V1l5OcFig. 3 Corophiurn volutator. Effect of temperature and s a l n i t yo n m e d a nlethal concentration, LC,, of arsenlc (ppm), at exposure times of
Bryant et a l . : T o x c oft y arsenic to three estuarine invertebrates133Table 3. Corophium volutator. Analysis of variance of effects of 8 arsenic concentrations, 5 salinities and 3 temperatures onmedian survival times. DF: degrees of freedom; MS. mean sum of squares; F: ratio of treatment mean square to error mean SS2Source of var atlonTemperatureTT2NS737,100407,500146 8181.16.118,09913,8501.612.76NSNSTemperature X 4.730.730.910.91NSNSNSTemperature X 870.42Temperature X concentration X salinity centration X salinityCS"FSignificant at P S 0.001;'NSNSNSNSSignificant at P 0.05; NS Not significantture increases the effect of arsenic concentration isprogressively diminished (Fig. 6) (i.e. a given increasein concentration reduces LT,, more at low temperaturelevels than at high temperature levels). High temperature therefore ameliorates the effect of arsenic concentration. It should also b e noted that the contour slopesappear steeper when concentration is plotted on alogarithmic scale rather than a linear scale, but therelative differences with respect to temperature d o notchange the X axis.The response surface isopleths (temperature versusconcentration) at salinity levels of 15, 25 and 35 %OTable 4. Macoma balthica. Median survival times, LTs0 (h), derived graphically at 5, 10 a n d 15"C, 15 to 3 5 L , a n d arsenicconcentrations of 15 to 1000 p p mConcentration(PP )153060125250500100015%5 "C25%35% 384270170140906642 384340260250195170105 384 3843302101701209015%010 C25%35%015%15 O 53619014012595855850
Mar. Ecol. Prog. Ser. 24: 129-137. 1985logconcentrationppmlogconcentration ppmFig. 4 . Macorna balthica. Change in median survival time, LT,, ( h ) ,with increasing concentration of arsenlc at: (a) 3 temperaturelevels; (b) 3 salinity levelswere very similar, confirming the lack of a significantlinear or quadratic effect of salinity on median survivaltime.Tubifex costatusFrom the median survival times obtained for Tubifexcostatus it is seen that more than 50 % of the individu-5Y)15rernperature CFig. 5. Macoma balthiEffect of temperature and salinity on median s u r v v a l time,LT,, ( h ) , at arsenic concentration 15 ppmals survived for over 384 h in concentrations of arsenicof 250 ppm under all combinations of temperature andsalinity levels (Table 7). Arsenic was only toxic at veryhigh concentrations (500 to 1,000 ppm) at all temperature and salinity levels. At all combinations of arsenicconcentration and salinity, 50 % mortality occurredsooner at 15 "C than at 5 "C. At 500 ppm, LT,, values at10 C were intermediate between those at 5 and 15 Cexcept at the 5 %O salinity level. Median survival timeswere greater at 5 %O than at other salinities at 5 and15"C, but at 10 C highest LT,, median survival timeswere recorded at the 25 O/oo salinity level. LC5, valuescould not be derived as only 2 concentrations providedmedian lethal estimates. A tentative conclusion drawn
135Bryant et al.: Toxicity of arsenic to three estuarine invertebratesTable 5. Macoma balthlca. Median lethal concentrations LC,, of arsenic (ppm) at 5, 10 and 15 C and 15 to 35 O/m for exposuretimes of 48 to 192 hExposuretime (h)5 "C25%15%035%015OL10 C25%35%015%15 "C25%35%0influenced Tubifex costatus in a similar manner. Nosignificant effect of salinity on median survival timewas observed for any of the 3 species, with theseranges of arsenic concentrations ( l ppm). Medianlethal concentrations of arsenic for C. volutator werelower at 5 %o S at both 5 and 10 C than at the rest of thesalinity range tested (10 to 35 %O S). Although C. volutator can osmoregulate over a salinity range of 2 to50 %o, its preferred range is 10 to 30 %o (McLusky 1968).The lower LC,, values recorded at 5 %O may be due tofrom these limited data is that temperature has a greater effect than salinity on the toxicity of arsenic to T.costatus with maximal survival at 5 "C in all salinities.DISCUSSIONHigh arsenic concentrations and high temperaturessignificantly decreased the median survival times ofboth Corophiurn volutator and Macoma balthica, andTable 6. Macoma balthica. Analysis of variance of effects of 7 arsenic concentrations, 3 salinities and 3 temperatures on mediansurv valtimes. DF: degrees of freedom; MS: mean sum of squares; F: ratio of treatment mean square to error mean 114,9511,4003.010.85NSNSTemperature X .163.790.28NSNS0.020.070.010.61NSNSNSNSSource of variationTemperature X salinityTST2STS2PS2Concentration X salinityCSC2SCS2C2S21111Temperature X concentration'Significant at P S 0.001;salinity (error)4462Total"X'Significant at P S 0.05; NS Not significant25.56115.58.191994.81,636.82F.NS. . m
Mar. Ecol. Prog. Ser. 24: 129-137. 1985I53060125250Concentratlon5001000ppmFig. 6. Macoma balthica. Response surface showing combined effect of arsenic concentration and temperature onmedian survival time, LTso (h), at 15 %Oanimals experiencing osmoregulatory stress at this salinity.Temperature and arsenic concentration appeared toaffect median survival times of Corophium volutatorina simpler way than they did on Macoma balthica, withonly the latter responding to a n interaction betweenarsenic concentration a n d temperature.T h e variance accounted for by the multiple regression analysis was 79 % for Macoma balthica, indicating that the experimental model provided a fair fit tothe untransformed test results and that it was a reasonable predictive model of the effects of temperature a n darsenic concentration on median survival times. In thecase of Corophium volutatorthe analysis accounted forjust over two-thirds of the variance, leaving almostone-third of the variance unexplained.Lloyd (1979) a n d Franklin (1980) state that a linearrelationship between log concentration and logresponse indicates that the test organism has nomethod of detoxification for the pollutant. Such a relationship held for all 3 species studied here. Comparingthe species' responses, Corophium volutatorwas moresensitive to arsenic than Macoma balthica, whereasTubifex costatus was relatively resistant to arsenic,living for over 384 h in 250 ppm. The effect of arsenicconcentration on median survival time, in relation tosalinity and temperature, for C. volutator and M. balthica is markedly different from the effect of chromiumconcentration on median survival times for the samespecies under similar ranges of temperature a n d salinity. Bryant et al. (1984) found that both increasingtemperature and decreasing salinity significantlydecreased the effect of chromium on median survivaltime.A defect in medium term toxicity testing may b estarvation in the later stages of the experiment. However in this study no deaths were recorded in Macomabalthica and Corophium volutator controls. McLusky(1967) showed that starvation caused a decrease insurvival time of C. volutator at salinities of 5 to 35 Y&only after 860 h. Therefore it was considered that starvation would not be a problem in these experiments of384 h duration.Temperature changes do clearly influence the effectof arsenic concentration on these species, suggestingthat a temperature-dependent process such as respiration may be disrupted by arsenic. Pentavalent arsenicis known to compete with phosphate ions in the process of oxidative phosphorylation (Dept. of Env. 1982),and since this latter process is temperature dependentit could explain the present results.The way In which variations in salinity affect heavymetal toxicity is not clear, but it is probably related tothe impairment of the osmoregulatory ability of anorganism (Schmidt-Nielsen 19747. Thus the fact thatarsenic toxicity to Corophium volutator and Macomabalthica is not influenced by salinity indicates thatarsenic does not affect osmoregulatory processesdirectly. An explanation for the lack of a salinity effectmay be due to arsenic being provided as the anionarsenate, unlike studies with cadmium, zinc etc.,where the metal is provided a s a cation, a n d in thisform competes with calcium and magnesium at uptakesites for osmoregulation (Phillips 1980).Sorensen (1976) showed that percentage survival inthe green sunfish Lepomis cyanellus (a freshwaterteleost) decreased, and its mean arsenic uptakeincreased, as temperature, arsenic concentration andTable 7 Tubifex costatus. Median survival times, LT,, ( h ) , derived graphically at 5, 10 and lS C, 5 to 25%, and arsenicconcentrations of 250 to 1000 ppmConcentration(PP )25050010005%5 "C15%25%5% 384220125 384130100 384170120 384966410 C15% 3841156815 "C25%0 384160805 %015% 38415068 38485642.59 38411042
Bryant et al.: Toxicity of arsenic to three estuarine invertebratestime of exposure were increased. There appear, however, to be no previous reports on the interactionsbetween salinity, temperature and arsenic concentration affecting survival times with which our studymight be directly compared.As arsenic in sea water occurs principally asarsenate (Unlu & Fowler 1979), sodium arsenate wasused as the source of arsenic in this study. Medianlethal concentrations (LC,,) values from previousstudies on arsenic toxicity to marine molluscs refer totrivalent arsenic as sodium arsenite, and are thus notdirectly comparable with this study where pentavalentarsenic as sodium arsenate was used. A 96hvalueof 3.49 pprn trivalent arsenic was recorded forArgopecten irradians at a temperature of 20 C andsalinity of 25 Ym (Nelson et al. 19?6), and 48h LCSoof7.7 pprn trivalent arsenic for Crassostrea virginica at atemperature of 26 "C a n d a salinity of 25 %O (Calabreseet al. 1973). Both 96h and 48h LC,, values for Macomabalthica of 8 5 a n d 520 pprn pentavalent arsenic at atemperature of 15 C a n d a salinity of 25 960, are muchhigher.The 96h LC,, values for Corophium volutatorrangedfrom 6 to 60 pprn pentavalent arsenic depending ontemperature. These values are comparable with a 96hLCSo of 24.7 pprn trivalent arsenic obtained forPenaeus setiferous by Curtis et al. (1979). Howeverboth these crustaceans have 96h LC50values considerably higher than that of 0.508 pprn trivalent arsenic forthe copepod Acartia clausi (U.S. E.P.A. 1980).These differences reflect either the different effectsof trivalent a n d pentavalent arsenic on median survival time or the greater tolerance of the estuarinespecies tested in this study compared with the marinespecies previously observed. It is, nevertheless, essential to consider the effects of temperature when assessing toxic effects of arsenic on the survival of aquaticanimals.Acknowledgements. This study was supported financially bythe WRc Environment, Stevenage and Medmenham. It is apleasure to thank G . Mance for his advice and support, andM. Burnett for typing the manuscript.LITERATURE CITEDAnonymous (1980).SCA Biological Methods. Working Group7.4. Acute toxicity tests in seawater TTP31 (Revise IV).Standing Committee of Analysts, LondonBryant, V., McLusky, D. S. Roddie, K., Newbery, D. M. (1984).Effect of temperature and salinity on the toxicity ofchromium to three estuarine invertebrates (Corophiumvolutator, Macoma balthica, Nereis diversicolor). Mar.Ecol. Prog. Ser. 20: 137-149Calabrese, A., Collier, R. S. Nelson. D. A., MacInnes, J. R.(1973). The toxicity of heavy metals to embryos of theAmerican oyster Crassostrea virginica. Mar. Biol. 18:162-166Curtis, M. W., Copeland, T L., Ward, C . H. (1979). Acutetoxicity of 12 industrial chemicals to freshwater and saltwater organisms. Water Res. 13: 137-161Department of the Environment (1982). Arsenic-bearingwastes. Waste management paper no. 20. Her Majesty'sStationery Office. LondonDavies, 0. L. (1979). T h e design a n d analysis of industrialexperiments. Longman, New YorkFowler, S. W., Unlu, M. Y (1978). Factors affecting bioaccumulation and elimination of arsenic in the shrimp Lysmata setlcaudata Chemosphere 9: 711-720Franklin, F. L (1980). Assessing the toxicity of industrialwastes, with particular reference to variations in sensitivity of test animals. MAFF Fish. Res. Tech. Rep. 61: 1-10Khayrallah, N . , Jones, A. M. (1975).A survey of the benthos ofthe Tay estuary. Proc. R. Soc. Edinb. (B) 75: 113-135Litchfield, J . T. Jr. (1949). A method for rapid graphic solutionof time-percent curves. J. Pharmac. Exp. Ther. 97: 3 9 9 4 0 8Lloyd, R. (1979). Toxicity tests with aquatic organisms Lecture presented at the Sixth FAO/SIDA Workshop of Aquatic Pollution in relation to the protection of livingresources. FAO, Rome, TF-RAD 112 (SWE) (Suppl 1):165-178McLusky. D. S. (1967). Some effects of salinity o n the survival.moulting a n d growth of Corophium volutator. J. mar. biol.Ass. U.K. 47: 607-617McLusky, D. S. (1968). Aspects of osmotic and ionic regulation in Corophium volutator. J. mar biol. Ass. U.K. 48:769-781McLusky, D. S , Teare, M,, Phizacklea, P. (1980). Effects ofdomestic and industrial pollution on distribution andabundance of aquatic oligochaeta from the Forth estuary.Helgolander Meeresunters. 33: 384-392Nelson, D . A., Calabrese, A., Nelson, B. A., MacInnes, J. R.,Wenzloff, D. R. (1976). Biological effects of heavy metalson luvenile Bay Scallops, Argopecton irradians, in shortterm exposures. Bull. environ. Contam. Toxicol. 16:275-282Phillips, D. J. H. (1980). Ecological cycling, Part 1. In. Nriagu,J. 0. (ed.) Cadmium in the environment. Wiley-Interscience, New York, p. 450-483Schmidt-Nielsen, B. (1974). Osmoregulation: effect of salinityand heavy metals. Fedn. Proc. Fed. Am. Socs. exp. Biol. 33:2137-2146Schnute. J., McKinnell. S. (1984). A biologically meaningfulapproach to response surface analysis. Can. J. Fish. aquat.Sci. 41: 936-953Sorensen, E. M. B. (1976).Thermal effects of the accumulationof arsenic in green sunfish, Lepomis cyanellus. Arch. Env.Contam. Toxicol. 4: 8-17Theede, H., Scholz, N., Fischer, H. (1979). Temperature andsalinity effects on the acute toxicity of cadmium toLaomedea loveni (Hydrozoa). Mar. Ecol. Prog. Ser. 1:13-19Unlu, M. Y., Fowler, S. W. (1979). Factors affecting the flux ofarsenic through the mussel Mytilus galloprovincalis. Mar.Blol. 51: 209-219U.S. Environmental Protection Agency (1980).Ambient waterquality criteria for arsenic. Ref. No. PB82-117327Vernberg, W. B., De Coursey, P. J., O'Hara, J. (1974). Multipleenvironmental factors effects on physiology of the fiddlercrab, Uca pugilator. In: Vernberg, F. J., Vernberg, W. B.(ed.) Pollution a n d ph.ysiology of marine organisms.Academic Press. New York, p. 381-425This paper was submitted to the editor; it was accepted for printing o n April 25, 1985
The small effect that salinity has on the toxicity of arsenic at salinities greater than 10 %O compared to the effect of temperature is clearly demonstrated in Fig. 3. The analysis of variance of median survival times Temperature C data for Corophium volutator 3, shows that the i , 2. hj volulator, Effect of temperature and salin-
salinity of water by hydrometer. Similarly salty water refracts more than freshwater and this property is the reason for measuring salinity of water by refract meter. As the property of variation of microwave emissivity with temperature and salinity of sea surface, salinity sensor is mounted on NASA’s Aquarius Instrument satellite (June
4.3.1 Effect of Temperature at pH 4.5 57 4.3.2 Effect of Temperature at pH 5.0 58 4.3.3 Effect of Temperature at pH 5.5 59 4.3.4 Effect of Temperature at pH 6.0 60 4.3.5 Effect of Temperature at pH 6.5 61 4.3.6 Combination Effect of Temperature on Enzymatic Hydrolysis 62
32-34 ppt. Salinity data was collected using a Dual Scale Sea Water Salinity Refractometer, recorded in tandem with temperature data. The seawater inside the trays was taken from the same source, and no pumps were used, causing salinity recordings to have little to no effect on experimental data excluding days affected by equipment
The aim of the present work was to study the effect of salinity and water stress on plant performance in different giant reed clones. To this end, two separate experiments were carried out. Firstly, a study with both stresses was performed (experiment 1). This experiment aimed to determine the effects of salinity and water stress on
Modelig Low Salinity Waterflood and Low Salinity Surfactant flooding". But other than that there are no specific geologic structures other than a difference in absolute permeability between the regions. The horizontal grid-sensitivity of the system and how it affects fluid flow, dispersion, and production will be emphasized in this study.
dissolved in root zone soil moisture to adversely a ect the plant growth (Rengasamy, Chittleborough, & . of soil salinity levels and mapping of salinity a ected areas (Katsaros, Vachon, Liu, & Black, 2002). . 2005). High resolution optical datasets are mostly available on commercial and paid basis and almost all currently active SAR .
A method and apparatus are described for disposing of salt byproduct from a zero liquid operation, such as a zero liquid discharge desalination plant. The present method and apparatus concern a power generation plant, comprising a salinity gradient power unit (SGPU) comprising a high salinity feed, a low salinity feed, and a mixed water output.
an accounting policy. In making that judgment, management considers, first the requirement of other IFRS standards dealing with similar issues, and the concepts in the IASB’s framework. It also may consider the accounting standards of other standard-setting bodies. International Financial Reporting Standards Australian Accounting Standards
