The effect of temperature on the respiratory electron transport system in marine plankton

Deep-SeaResearch, 1975,Vol. 22, pp. 237 to 249.PergamonPress. Printedin Great Britain.

The effect of temperature on the respiratory electron transport system in marine plankton T. T. PACKARD,* A. H. DEVOL* and F. D. KING* (Received 10 February 1974; in revised form 20 September 1974; accepted 5 October 1974)

Abstract--The effect of temperature on the respiratory electron transport system in plankton was studied in plankton populations between 10 and 45°N lat in the eastern Pacific Ocean. The results yielded Arrhenius activation energies of 15'8 ± 2'8 kcal mole-1 for microplankton, 16 kcal mole-1 for epipelagic zooplankton and 13'2 kcal mole-1 for bathypelagic zooplankton. The differences among these values were not statistically significant. The respiratory electron transport activity and the Arrhenius activation energy in the microplankton from the euphotic zone ranged from 0"12 to 0.65 Izl 02 1-i h-X and from 11-7 to 21.9 kcal mole-x, respectively.Neither parameter varied systematically with temperature. INTRODUCTION

TEMPERATURE is potentially an important modulator of oceanic rate processes. It varies by nearly 32°C from --1-7°C in Antarctic waters to greater than 30°C in tropical waters, a difference which, if the normal dependence of metabolism on temperature were obeyed, would alter biological rates by as much as a factor of 10. On this basis, one would expect organisms in polar waters to move and respire much slower than their counterparts in southern waters, but this difference in metabolism is not observed (SOMERO, GIESE and WOHLSCHLAG, 1968). Marine organisms apparently have developed adaptive mechanisms that increase metabolic efficiency at low temperature and decrease it at high temperature, thus achieving homeostatic control over their enzyme reactions. The fact that light, nutrient salt concentration and advection are, apparently, far more important than temperature in regulating phytoplankton productivity is indirect evidence of the effectiveness of this homeostasis (EPPLEY, 1972). Several mechanisms could be employed to achieve this regulation; cells could develop insulating thermal barriers (KNIPPRATH and MEAD, 1966), they could increase their metabolic rate, or they could alter their biochemistry. Homotherms employ the first two mechanisms, but true poikilothermic adaption must be accomplished by other means, most likely by biochemical changes. These changes could be effected by using alternate pathways (HOCHACHKA and HAYS, 1962) or by regulating the concentration of active enzymes (JORGENSEN, 1968); but because the first mechanism requires duplication of function and the second assumes identical kinetic and thermodynamic properties in 'cold' and 'warm' adapted enzyme systems, these two mechanisms are most probably not utilized (HOCHACHKA and SOMERO, 1971). More likely, adaptation is accomplished by modifying the structure and, consequently, the kinetic and thermodynamic properties of the enzymes. As an example of this mechanism, low temperature depression of catalytic activity could be compensated for by increasing the effective *Department of Oceanography, University of Washington, Seattle, Washington 98195, U.S.A.

237

238

T.T. PACKARD,A. H. DEVOLand F- D. KING

enzyme activity through either an increase in the enzyme substrate affinity (decreasing the Michaelis constant, Kin) or by decreasing the free energy of activation (Low, BADAand SOMERO,1973). Both of these mechanisms, operating separately or together, would be effective in accelerating a metabolic rate when it would otherwise be depressed by low temperature. At high temperatures the enzyme could assume a structure characterized by a low enzyme-substrate affinity (high Kin) or a high free energy of activation (AGq-). A change in either property would effectively decrease the activity of the enzyme at these temperatures. Adaptive shifts in the Km associated with environmental temperature have been observed (HOcHACI-IKAand SOMERO,1968 ; SOML~O and HOCnACnKA, 1968; 1969; SorvmRo, 1969a, b), but HOCHACnKA and SOMERO (1971) observe that the Km shift alone cannot account for temperature adaptation. They suggest that the Arrhenius activation energy, Ea, might play a role in the adaptive process because of its role in decreasing AG4-. This suggestion has been supported by the results of HAZ[L (1972), SOMERO, GmSE and WOHLSCHLAG (1968) and Lvo~qs and RAISON (1970); but not by the results of HOCHACHKA and SO~RO, 1968), although the latter tend to de-emphasize their findings in their subsequent review (Hochachka and Somero). In comparing a number of poikilothermic and homeothermic organisms, Low, BADAand SOMERO(1973) show, although they do not emphasize it, that Ea correlates well with adaptation temperature of each species. Thus, changes in E~ appear to be part of the mechanism of temperature adaption, although clarification of this role is still needed. In this paper, we report measurements of the E~ for the activity of the respiratory electron transport system (ETS) in assemblages of planktonic organisms from the surface and deep waters of the northeastern Pacific Ocean. The temperature of these waters ranged from 2 to 27°C. Because these habitat temperatures are relatively stable, we expected to observe a change in E, from about 4 kcal mole -1 at 2°C to about 20 kcal mole -1 at 27°C, as predicted by the data of HAZEL (1972), SOMERO, GIESE and WOHLSCHLAG(1968) and Low, BADA and SOMERO(1973). Our expectations were not realized. METHODS

Activity of the respiratory electron transport system (ETS) Microplankton ETS activity was measured by the method of PACr~,RD (1971) using controls based on boiled homogenates. Zooplankton ETS was measured by macerating part of a zooplankton sample in a blender for 1 min at 0 to 4°C, grinding an aliquot of the macerated sample with a glass fiber filter in a Teflon-glass tissue grinder for 2 min at 0 to 4°C and analyzing the resulting homogenate for ETS activity by the same method used for the phytoplankton samples. 'Microplankton' in this paper refers to the material that passes through a 202%tm net and is removed by a Gelman glass fiber filter (Type A with a mean pore size of 0.3 ~m); it contains microzooplankton and bacteria but is largely comprised of phytoplankton (PACKARD, HARMON and Bouct-mR, in press). Zooplankton, in this paper, refers to material caught in a l-m, 202-~tm net, towed at 15 m min-1; it does not include the microzooplankton and the swift maerozooplankton.

Arrhenius activation energy (Ea) Arrhenius plots were constructed from the results of the temperature dependence

The effectof temperatureon the respiratoryelectrontransport systemin marineplankton 239 experiments by graphing the natural logarithms of the ETS activity against the reciprocal of the absolute temperature (PATTON, 1968). The regression line and the standard deviation of the slope were calculated by the method of least squares. The Arrhenius activation energy was then calculated from the slope of the regression line by the equation:

E a = --RS, where R is the gas constant (1.987 kcal mole -x) and S is the slope of the Arrhenius plot. Ea is expressed in units of kcal mole -1.

Chlorophyll a The SCOR/UNESCO method was used, although the absorbance was measured at 665 rather than 663 nm. Particulate carbon (PC) A 1 to 5-1iter sample was first filtered through a 202-Ezm net to remove the macrozooplankton and then through a Gelman glass fiber filter. The filter was then fumed for 0.5 min in HCI vapors to remove inorganic carbonates, desiccated at 60°C for 24 h, and stored frozen in small glass vials until analysis. The carbon was then determined gravimetrically on a Mettler microblance (Type M554) after combustion in a Coleman Carbon-Hydrogen Analyzer (Model 33). The precision of the analysis was -4-7 ~g at the 40 ~tg level (RIcI-IARI)Sand DEVOL, 1973). Parliculate nitrogen (PN) From 4 to 12 liters of seawater were first filtered through a 202-~m net to remove the macrozooplankton and then were filtered through a Gelmann glass fiber filter. The filter was desiccated and stored as described above. The nitrogen was determined volumetrically in a Coleman Nitrogen Analyzer as described by BARSO^TE and DUGDALE (1965). Temperature dependence experiments The experiments were performed without preincubation in an array of water baths held to within -4- 0.05 of the experimental temperature. Thermal equilibration occurred within 30 s, which made preincubation unnecessary. RESULTS Variations of microplankton ETS activity and the PC/PN ratio with latitude and temperature ETS activity, particulate carbon, and particulate nitrogen were measured in seawater samples from the California Current and the Tropical Surface Water (WVRTIO, 1967) of the northeast Pacific Ocean between 10 and 45°N. The sample locations and the results are shown in Fig. 1 and Table I. Regression analysis indicates that neither the ETS activity, nor the specific ETS activity (ETS/PC and ETS/PN), nor the PC/PN ratio is correlated with temperature or latitude at the 95 % level. The biological properties do differ, however, from the northern to the southern end of the region studied, but the differences only become significant when the two water

0"49 0.27 0"37 0-19 0.23 0'15 0-30 0"31 0.35

0.31 0.65 0.12 0"35 0.30

1 2 3 4 5 6 7 8 9

10 11 12 13 14

(Ezl O, h -11 -~)

ETS activity

84 47 47 60 56

141 162 229 123 133 126 131 318 210

(tzg 1-*)

Carbon

0-04 0.02

0.52 0"42 0.53 Tropical Surface Water 0.09

California Current

(Ezg 1-~)

Chlorophyll-a

8'3 5 "3 4 "4 7-0 4-8

15.8 12-5 14.6 12-3 14.4 10.4 12.5 30.1 17-6

(Izg 1-x)

Nitrogen

3'703 13.766 2 "532 5"750 5-411

1 "553 1-679 1.607 1-537 1 '729 1-159 2.267 0.962 1.648

([zl 02 h -x ~.g-*)

ETS/PC

37-47 122.08 27 "05 49.29 63"13

13-87 21 "76 25"21 15.36 15 "97 14"04 23 "76 10-17 19.66

(Ezl O~ h -x F.g-1)

ETS/PN

10"12 8 -84 10 "68 8-57 11 "67

8'92 12"96 15"68 10"00 9 '24 12"12 10"48 10-56 11 "93

PC/PN

Table 1. Respiratory electron transport (ETS) activity at sea surface temperature (Table 3), particulate carbon (PC), chlorophyll a, and particulate nitrogen (PN) data in surface seawater samples from the northeast Pacific Ocean. The origin of each sample is shown by experiment number in Fig. 1.

z

o

.>

¢.)

to

0.30

0.35

California Current (Experiments 1-9)

Tropical Surface Water (Experiments 10-14) 59.4

174.8

Carbon (gg l -~)

ETS Activity

(~1 O, h -~ 1-t)

0.05

0.49

(ttg 1-x)

Chlorophyll-a

6.0

15-6

(~g 1-x)

Nitrogen

ETS/PN

6-23

1-57

59.80

17.76

(~1 02 h -z tLg-~) (txlOa h - t izg-~)

EI'S/PC

9.98

11-32

PC/PN

Table 2. Comparison of ETS activity, particulate carbon ( P C ) , and particulate nitrogen (PN) in microplankton samples from the California Current and the Tropical Surface Water of the northeast Pacific Ocean.

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Fig. 1. Location of the experiments described in Tables 1-3. The stations were occupied on cruise 66 of the R.V.T.G. Thompsonfrom the University of Washington. masses are compared (Table 2). The California Current Water is distinguishable from the Tropical Surface Water by its significantly higher (95 % level) carbon, nitrogen and specific ETS activity.

Variations of Ea with latitude and temperature To characterize the temperature dependence of microplankton ETS activity, seawater samples were analyzed at temperatures ranging from 7 to 50°C. Arrhenius plots (Figs. 2-4) were constructed and activation energies (Ea) were calculated from the slope of the regression lines (Table 3). Figure 2 shows the temperature dependence of microplankton ETS activity in northern California Current Waters. The temperature of maximum ETS activity in experiment 4 was 40°C and the E a was 15.0 kcal mole -1. Experiment 2 yielded an E~ of 14.2 kcal mole-L Microplankton from southern California Current Waters exhibited similar characteristics (Fig. 3); both experiments 8 and 9 yielded 40°C as the temperature of maximum ETS activity, and Ea values of 15.7 and 13.4 kcal mole -1 (Table 3). The plankton sample for experiments 8 and 9 was drawn from 16°C seawater, whereas the one used in experiments 2 and 4 was drawn from 12°C seawater. At the southern limit of these experiments, where the seawater temperature was greater than 27°C (Table 3), the temperature characteristics became somewhat erratic (Fig 4). The temperature of maximum activity increased slightly to 43°C and E~ ranges from 11.7 kcal mole -1 in experiment 13 to 21.9 kcal mole -1 in experiment 14. The results of experiments 11 and 12 fell between these values. The variability in these experiments cannot be explained readily; there

(°C)

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1

2 3 4 5 6 7

8 9 10 11 12 13 14

15 16

17

Seawater temperature

4- 0-41 4- 0.31 4- 0"69 ~ 0"59 4- 0.78 4- 0.54 4- 0-56

4- 0.29 i 0-25 4- 0.18 -4- 0.35 4- 0-47 4- 0"15

16"8 4- 0-63

15"2 4- 1-39 13.2 4- 0"69

15"7 13-4 16'6 13"8 19.4 11"7 21.9

14.2 13.0 15.0 16.0 19.9 17"2

14"3 4- 0-11

(kcal mole -~)

Activation energy

43

39 39

40 40 40 35 43 43 43

-40 40 40 30 40

35

(°C)

Temperature of max. activity

Diatoms (Nitchia seriata and Skeletonema costatum) and Ciliates Dinoflagellatcs (Prorocentrum sp. and Peridinium sp.) Coccolithophorids (Pontosphaera sp.) and Diatoms (Ch. concavicornis) Diatoms (Chaetoceros sp. and Rhizosolenia sp.) and Coccolithophorids (Pontosphaera sp.) Coccolithophorids (Pontosphaera sp.) DinoflageUates (Ceratium sp. and Peridinium sp.) and Silicoflagellates (Dictyocha sp.) Coccolithophorids (Pontosphaera sp.) and Diatoms (Bacteriastrum sp.) Coccolithophorids (Pontosphaera sp.) Coccolithophorids Coccolithophorids Ciliates, Dinoflagellatcs (Noctiluca sp. and Ceratium longipes) and Diatoms (Rhizosolenia sp.) Copepods (Euchaeta sp., Eucalanus sp. and Oithona sp.) Foraminifera, Pteropods and Copepods (Euchirella sp., Phyllopus sp. and Metridia sp.) Foraminifera, Copepods (Onacaea sp., Acrocalanus sp., Clausocalanus sp. and Paracalanus sp.)

Coccolithophorids (Pontosphaera huxleyi and Acanthoica sp.), Silicoflagellates ( Distephanus speculum) and Diatoms ( Coscinodiscus marginatas and Navicula sp.) Diatoms (Rhizosolenia alata and Chaetoceros concavicornis)

Dominant organisms

Table 3. Arrhenius activation energies and the temperature o f maximum activity for the respiratory electron transport activity from microplankton and zooplankton. The origin o f each sample is shown by experiment number in Fig. 1. Each activation energy is accompanied by its standard deviation which is, in turn, a reflection of the variability around the slope o f the Arrhenius plot. The dominant organisms were determined from formalin preserved samples (5 % formalin buffered with 1 m M borate, p H 8.0). The microplankton samples were sedimented in 100-ml settling chambers for 24 h and were counted with an inverted microscope.

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244

T . T . PACKARD, A. H. DEVOL and F. D. KrNo

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30 45 TEMP (*C)

60

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- 2.001 3.0

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3.2 3.4 3.6 VTEI~P xlO3 (*K)

3.8

Fig. 2. The temperature dependence of the ETS activity in natural microplankton assemblages from the northern part of the California Current. The maximum ETS activity occurred at 40°C; the E, from the Arrhenius plot (fight) is 14-2 kcal mole -1 for experiment 2 and 15 kcal mole -1 for experiment 4. Sea surface temperatures were 11 and 12°C (Table 3). See Table 3 for the dominant organisms in each sample.

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1.00,

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MICROPLANKTON 2.00

o.so I-

1.60

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-2.00

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3.2 3,4 3.6 I/TEMP XIO 3 ( ° K )

3.8

Fig. 3. The temperature dependence of the ETS activity in natural microplankton assemblages from the southern part of the California Cknrent waters (Punta Eugenia). The maximum ETS activity occurred at 40°C; the Eo values for experiments 8 and 9 wore 15.7 and 13-4 kcal mole -1. Seawater temperatures were 16.5 and 16.9°C (Table 3). The dominant organisms in each sample are also given in Table 3.

The effect of temperature on the respiratory electron transport system in marine plankton

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=

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3,6

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Fig. 4. The temperature dependence of the ETS activity in natural microplankton assemblages from the eastern tropical Pacific Ocean (Fig. 1). The maximum ETS activity occurred at 43°C; the E, values for experiment 13 and 14 were 11.7 and 21-9 kcal mole -1. The seawater temperatures were 27.6 and 27.4°C (Table 3). The dominant organisms in each sample are also given in Table 3.

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45

60

-5,00 ~ 3.0

3.2

3.4 3.6 I/TEMP XlO 3 (°K }

3.8

Fig. 5. The temperature dependence of the ETS activity in a natural assemblage of zooplankton in the upper 100 m of the eastern tropical Pacific Ocean (Fig. 1). The maximum ETS activity occurred at 39°C; the E, values, for experiments 15 and 17 were 15.2 and 16"8 kcal mole -1. The seawater temperature ranged from 14°C at 100 m to 27°C at the surface. Copepods dominated experiment 17 (Table 3).

246

T.T. PACKARD, A. H. DEVOL and F. D. KING

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3.8

Fig. 6. The temperaturedependence of the ETS activity in a natural assemblage of zooplankton from the bathypelagic waters(2000-3000 m) of eastern tropicalPacificOcean. The maximumETS activity occurred at 39°C; the E, was 13.2 kcal mole-L The seawater temperature between 2000 and 3000 m was 2°C (Table 3). Foraminifera, pteropods, and copepods dominated the sample (Table 3). were changes in the taxonomic composition of the populations (Table 3), but they were not systematically associated with the variations in E=. Two zooplankton samples from the upper 100 m (experiments 15 and 17) and one from the bathypelagic waters between 2000 and 3000 m (experiment 16) were also analyzed (Table 3). The E= ranged from 13.2 (bathypelagic zooplankton) to 16.8 and the temperature of maximum ETS activity ranged from 39 to 43°C; neither result was significantly different from the results of the microplankton experiments. When the activation energies derived from all experiments are plotted against temperature (Fig. 7), the graph reveals no significant dependence of E= upon temperature. The mean for all values above 20°C (Tropical Surface Water) is 16.5 kcal mole -1 with a standard deviation of -t- 1.5. The mean values between 8 and 20°C (California Current) is 15.5 kcal mole -1 i 0.6. The two values are not significantly different from each other. A regression line, fitted by the method of least squares, is described by the equation: E= -----0.118 × Temp + 13.7, but the slope is significantly different from zero only at the 70% level. DISCUSSION

The specific ETS activities in the California Current and the Tropical Surface Water are significantly different from each other. The difference cannot be explained on the basis of the temperature difference alone, because the correlation with temperature is only significant at the 90% level. An obvious alternative explanation is that

The effectof temperature on the respiratory electron transport systemin marine plankton 247

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(°C)

Fig. 7. The dependence of E, for ETS activity on environmental temperature. Microplankton and zooplankton samples are represented by dots (O) and circles (<3), respectively.The average temperature in the upper 100 m was used to plot the zooplankton data from experiments 16 and 18. The regression line, E, = 0.118°C + 13"7, was fitted by the method of least squares. The slope is significantlydifferent from zero only at the 70 % level. the detritus in the California Current Water is higher by a factor of 3 than the:detritus in the Tropical Surface Water. The ETS/PC ratio is much lower in both water masses than it is in the Baja California upwelling area (PAcI~ARD, HARMON and BOUCHEg, in press), so detritus is undoubtedly a factor, but whether it or the temperature difference is more important cannot be determined from this data suite. Specific activities from below 10 and above 20°C as well as an independent measurement of the ratio of vital to detrital carbon are needed to resolve this question. JOgOENSEN (1968) and HOCHACHr,~ and SOMEgO (1971) predicted an increase in the enzyme concentration in cold adapted organisms. In terms of nitrogen and carbon, this increase would be reflected in a decrease in the PC/PN ratio in cold adapted plankton. In this study, the PC/PN ratio ranges from 8.9 to 15.7 with a mean value of 10-8 and a standard deviation of 1.9. Regression analysis does not show a significant dependence of the ratio on either temperature or latitude. The activation energies observed in this study range from I 1.7 to 21.9 kcal mole -1, which is similar to the range of E, value of a variety of enzymes in poikilothermic aquatic organisms (HOCHACHKAand SOMERO,1971) and is also similar to the E, range for succinate dehydrogenase in homeothermic organisms (S[ZER, 1943; DOMBgAOI, CSANX'Iand DOMSAN, 1966). These values, like most other Eo determinations, are subject to the error discussed by GIBSON (1953), because they are not corrected for enthalpy of activation (AH:k). This omission introduces a 10% over-estimation of E,, but for the purpose of relating E, to habitat temperature, this error is incomequential. HAZEL (1972) suggests that E~ values would increase with habitat temperature, but regression analysis of the data in Table 3 reveals a correlation at only the 70% level and thus does not support his findings. The temperature of the maximum ETS activity reported here should not be interpreted as an absolute property of plankton ETS activity. The observed temperature of any enzymic reaction is a function not only of the properties of the enzyme

248

T.T. PACKARD,A. H. DEVOLand F. D. KaNO

substrate interactions, but also of the incubation time. As the incubation time decreases the observed optimum should actually increase because enzyme denaturization is being minimized. For comparative studies using a standardized technique, variations in the observed optimum are useful because they reflect variations in the true optimum temperature of the enzyme reaction. If there were a large difference in the optimum temperature of plankton ETS activity it would have been observed in our experiments. Since no significant variations occurred in either the optimal temperature or the Ea, we conclude that the temperature dependence of both mieroplankton and zooplankton is the same and is independent of habitat temperature.

Acknowledgement--We thank T. G. OWENSfor analyzing the carbon samples, JuHo VIDAL for identifying the zooplankton, PAMELAMASSEVfor typing the manuscript, and W. T. McCARThYfor reading it. This work was supported by NSF grants GA 34615 and GA 10084 and by ONR contract N.00014-67-A-0103-0014 and is contribution No. 826 from the Department of Oceanography, University of Washington, Seattle. REFERENCES B~SDA~ R. J. and R. C. DUODALE (1965) Rapid conversion of organic nitrogen to N~ for mass spectrometry: an automated Dumas procedure. Analytical Biochemistry, 13, 1-5. DOMaRAm G. A., I. CsAma and G. Y. DO~LSAN(1966) The analysis of changes in the activation energy of succinate dehydrogenase, as influenced by some antitumour agents. Biochemical Pharmacology, 15, 508-511. EPeLEY R. W. (1972) Temperature and phytoplankton growth in the sea. Fishery Bulletin, 70, 1063-1085. GmsoN K. D. (1953) True and apparent activation energies of enzymatic reactions. Biochimica et Biophysica Acta, 10, 221-229. HAZEL J. R. (1972) The effect of temperature acclimation upon succinate dehydrogenase activity from the epaxial muscle of the common goldfish (Carassius auratus L.)--I. Properties of the enzyme and the effect of lipid extraction. Comparative Biochemistry and Physiology, 43, 837-861. HOCI~ACnKAP. W. and F. R. HAYES(1962) The effect of temperature acclimation on pathways of glucose metabolism in the trout. Canadian Journal of Zoology, 410, 261-270. HOCnACnKA P. W. and G. N. SoMrmo (1968) The adaption of enzymes to temperature. Comparative Biochemistry and Physiology, 27, 659-668. HOCrlACHKA P. W. and G. N. SOMm~O(1971) Biochemical adaption to the environment. In: Fish physiology, W. S. HOAR and D. J. RANDALL,editors, Academic Press, Vol. VI, pp. 99-165. JORG~NSEN E. G. (1968) The adaptation of plankton algae. II. Aspects of the temperature adaption of Skeletonema costatum. Physioiogia Plantarum, 21, 423--427. KNn'PRAXH W. G. and J. F. M~AO (1966) The effect of environmental temperature on the fatty acid composition and on the in vivo incorporation of 1-a4C-acetate in goldfish (Carassius auratus, L.). Lipids, 3, 121-128. Low P. S., J. L. BADAand G. N. SOMERO(1973) Temperature adaption of enzymes: roles of free energy, the enthalpy, and the entropy of activation. Proceedings of the National Academy of Sciences, U.S.A., 70, 420-432. LYONS J. M. and J. K. RAISON(1970) A temperature-induced transition in mitochondrial oxidation: contrasts between cold and warm-blooded animals. Comparative Biochemistry and Physiology, 37, 405-411. PACg.AnD T. T. (1971) The measurement of respiratory electron transport activity in marine plankton. Journal of Marine Research, 29, 235-244. PACK~,D T. T., D. HARMON and J. Boucrmn (in press) Respiratory electron transport activity in plankton from upwelled waters. Tethys. PATTON A. R. (1968) Biochemical energetics and kinetics, W. B. Saunders, 116 pp. RIer~atDs F. A. and A. H. DEVOL (1973) Organic matter in anoxic environments, In:

Proceedings of the international symposium of hydrochemistry and biochemistry, E. INGERSON,editor, The Clark Company, II, pp. 481--489.

The effect of temperature on the respiratory electron transport system in marine plankton 249 Stzr~ I. W. (1943) The effects of temperature on enzyme kinetics. Advances in Enzymology, 3, 35-62. SOMERO G. N. (1969a) Enzymatic mechanisms of temperature compensation: immediate and evolutionary effects of temperature on enzymes of aquatic poikilotherms. American Naturalist, 103, 517-530. So~_~o G. N. (1969b) Pyruvate kinase variants of the Alaska king crab: evidence for a temperature-dependent interconversion between two forms having distinct and adaptivekinetic properties. Biochemical Journal, 114, 237-241. S o , R e G. N., A. C. Gw~sEand D. E. WOHLSCHLAG(1968) Cold adaptation of the Antarctic fish, Trematomus bernacchii. Comparative Biochemistry and Physiology, 26, 223-233. SOM~O G. N. and P. W. HOCnACHKA(1968) The effect of temperature on catalytic and regulatory functions of pyruvate kinases of the rainbow trout and the Antarctic fish, Trematomus bernacchii. BiochemicalJournal, 110, 395-400. S o ~ o G. N. and P. W. HOCHACHKA(1969) Isoenzymes and short-term temperature compensation in poikilotherms: activation of lactate dehydrogenase isoenzymes by temperature decreases. Nature, 223, 194--195. WYRTKX K. (1967) Circulation and water masses in the eastern equatorial Pacific Ocean. International Journal of Limnoiogy and Oceanography, 1, 117-147.