•J ••'•

IC/75/15BHEPOET

distribution)

In te rna t iona l Atomic Energy Agency

and

Rations Educational Sc ien t i f i c and Cultural Organization

<^0pTEENATIOlJAL CENTRE FOE THEORETICAL FKTSICS

£/Dmk&{ * j < " PKHJAffif PRODUCTION STUDIES IS HEATED WATEH:

A general discussion on C measurements in thermally polluted waters

and r e su l t s from a p i l o t study on the Swedish east coast *

B. Ostrdm *•

International Centre for Theoretical Physics, Trieste, Italy.

Introduction

On behalf of the nat ional Svedish Environment Protect ion Board,

a cer ta in nuclear power plant , Simpevarp on the Swedish east coast , was

selected to serve as a test area for an investigation of the changes in primaryproduction due to thermal pollution. Since the primary production is the

first l ini in the marine food web, a determination of the change at this

level should provide a parameter for a continuous monitoring of disturbances

in the ecosystem caused by thermal pollution. To determine the production,t n e in situ method by Steeman Nielsen (1958) vas applied. With this method a knowii

amount of CT 0,, is'added to a water sample in a stoppered transparent bottle.

The bottle is then put back In the position where the sample was taken from,and

the photosynthetic CO- uptake is allowed to take place for half a solar

day, from noon to sunset. The cellular material is then collected on a

0.2 pore size filter and the radioactivity of the filter is measured. Thelit

thus determined amount of C incorporated into the cellular material

corresponds to the production which can subsequently be calculated. The

production of each sample is calculated in units of milligrams of carbon per

cubic metre and day. From a series of depths at one location, the values

can be integrated to give the production under one square metre of water

surface, the unit accordingly being milligrams of carbon per square metre.

ABSTHACT

Primary production studies Save been carried out in the cooling vater

of a nuclear power plant at Simpevarp on the Swedish Baltic coast. Followingl i t

the method developed by Professor E. Steeman Hielsen, the uptake of C 0,, in-

corporated into cellular tissue vas measured by a Geieer-Muller counter, and

the correlated production rate determined. In this paper both a discussion on

the principal problems connected to production studies in heated water and the

results from the pilot study- at Simpevarp are given.

JCHAMABE - TRIESTE

November 1975

• To be submitted for publication.

*• On leave of absence fromiFishery Board of Sweden, Hydrographic Department,

Box !iO31, liOOUO CHSteborg, Sweden.

Physical-chemical-biological interactions

The -̂ntliesis of different inorganic compounds forming organic compounds

is called'primary production'^ since it is the first or primary step forward

from inorganic dead material to living organic material. Some of this

organic material is used in nature to form new, generally more complex,

organic material; this process is called secondary production. However, for

the formation of the primary organic material, a supply of energy is necessary-

The dominating energy source for the primary production Is the sun which

supplies the energy by radiative transfer in the visible wavelength range.

The phytoplankton,being the primary producers In the sea,need not

only carbon dioxide , water and energy for their growth but also nutrients

and growth factors. The formation of proteins requires nitrogen,and the •

cell plasma requires phosphorus; the nutrient requirements for this

formation is met by the uptake of nitrogen and phosphate froa the water. The

growth factors vary between different species from noneat all to several,

often complex, compounds- Growth factors may be metal ions or organic

-2-

compounds such, as vitamins. Probably a large number of the growth factors

are BE yet unknown:. .

A part of the primarily produced aaterial is broken down again upon

death and decay of the species. The breakdown is normally catalysed by

•bacteria and resultB in a recycling of material in that nitrate and phosphate

Is again set free into the water. Also various organic compounds are formed

during this process. Another part of the primarily produced material is

consumed by the secondary producers, the zooplankton. Some of the nutrients

are then recycled to the water by excretions. Another fraction Is carried

on into the marine food web in the form of this zooplankton body tissue. In

the sea the number of atoms relation between the elements carbon, nitrogen and

phosphorus in planktonic tissue is found to be on an average

C : B : P 106 16 : 1 U)

Assuming that the proteinous material is grouped approximately as carbohydrate,

ammonia and phosphate, the important photosynthetic reaction can be written,

basedon a stoiehiometric calculation, as the combination of carbon dioxide,

nitrate, phosphate and water, in the following way:

106 C0 2 + 16 + 122 H£0

tb)

Upon death and decay, the decomposition of this material, in the presence

of oxygen, can be considered as the reverse reaction to (la) with bacteria

acting as catalyser.

Primaiy production in heated vater

Studies of primary production in heated water offer certain physical

problems to be dealt with because of the unnatural constraint put on the

ecosystem by thermal pollution. These are;

-3-

1. Direct biotic temperature effects,

2. building up of thermocllne,

3. dissolved gases, • .

•t. light conditions,

5. onset of fog,

6. altered Ice conditions,

7- climate changes,

which are dealt with below.

Dividing animals, plants and protista into groups of themophlles,

mesophiles and psychrophiles, indicates that temperature itself has a certain

influence upon the organisms. The affinity for certain temperature Intervals

is connected to the biochemical activity within the cells, often related to

the stability of enzymes-

In general the biochemical reactions are faster in higher temperatures

than in lower, within the limits of stability of compounds. It could there-

fore be expected that the primary production,involving the basic processes

in the bicsynthetic machinery building up plant tissue,should proceed at a faster

rate at a high temperature than at a low. The central process-Involved, the

photosynthesis, is of course dependent on^fenergy supply in the form of light

in the visible region rather than on high temperature,which Is equal to energy

in the infra-red region. However, from experience it can be Judged that the

photosynthesis is governed by both light and heat.

The light conditions in the autumn, when plant production normally

ceases, are usually sufficient to keep up production. The decline is a

result of several co-operating factors, but light alone is normally not

limiting. Instead, in an undisturbed system, it is usually the onset of

colder weather in the late autumn that brings production to an end. How, If

the temperature is increased by artificial means, the temperature conditions

are fulfilled for a continued high production extending into the vinter

months.

An effect of the heating of water is that the vojume is changed. Any

increase above I*°C is accompanied by an increase in volume. This thermal

expansion is equal to a decrease in density since the mass is conserved. There-

fore, vans vater is lighter than cold water and it forms a layer floating

on top of the water column close to the surface. Due to its buoyancy the

warmer top layer will not easily mix with the underlying water, unless strong

stirring forces are applied. The formation and presence of such a warm top

layer is proposed to be a necessary condition for a maintained primary

-U

production. Vithout this top layer the plankton species

responsible for the production vould be mixed down into the darker deep water,

oat of reach for the solar radiation. When the layer is formed the thermoelice

dividing it from the colder water below will prevent intermixing and thereby

help keep the plankton species in the upper photic layer, .available to the

solar light energy. An additional heating of tlie vater will contribute to

the maintenance of a warmer top layer, after the breakdown and mixing due

to winter cooling in unheated water, has taken place, and thereby provide the

necessary conditions for a prolonged production season.

The dissolved gases will be considered in somewhat more detail than other

factors of physical nature affecting the production in heated water. The

reasons are two: Firstly the dissolving capacity of the water for different

gases is highly dependent on temperature. Secondly two of the more important

gases in the marine environment, carbon dioxide and oxygen,are directly involved

in the primary production. Carbon dioxide is consumed and converted into

organic material while oxygen is produced during the photosynthetic process.

For a normal sea water at the surface the gases of the air are in

direct contact with and can freely go into a solution or leave the solution

until an equilibrium of the partial pressures exists. However, since the

diffusion across the interface is a process on molecular scale, it CBTI be a

question of several days before a new equilibrium is achieved after a change

in one of the phases. In other words, the exchange of gases across the air-

water interface is free but slow.

The relation between solubility and temperature for most gases in sea

water is such that cold water can dissolve more gas than wane water can. So

taking cold water which is saturated with respect to dissolved gases and

heating it,means that the gases are driven cut of the water. This is what

happens when cooling water passes through the power plant. However, this

process is not fast, e.g. normally,_gas bubbles are not formed, instead the

water remains over-saturated. First, when the water comes in contact with the

air at the surface is the excess gas given away to the air and the equilibrium

at the new temperature is established. As a consequence of this, the

vater later on will become somewhat under-saturated when it is cooled off to

its original temperature.

Considering carbon dioxide alone.it is one of the dissolved gases

normally in equilibrium with the air content. Carbon dioxide is not more than

3 parts per 10000 in the air. However, in the marine environment it plays ar.

Important role in spite of its low concentration. The solubility of carbon

- 5 -

dioxide does not have the same simple e^uilibritmi relation to air as other

gases have. The reason is that carton dioxide reacts with water to form

carbonic acid which dissociates into hydrogen, bicarbonate and carbonate ions.

How,more carbon dioxide can be digsolved.vhich again reacts with the water and

so on until a new equilibrium is formed which is dependent also on the. ionic

forms. Proportionally much more carbon dioxide can therefore be dissolved

in water before reaching equilibri™, compared with gases that do not dissociate.

Carbon dioxide is also consumed in the above-mentioned photosynthetie

process where COg and water are utilised to form carbohydrate with

visible light as the energy supply. Carbon dioxide though, is" in most cases

in ten-fold excess of the amount used for photosynthesis. Only in extreme cases

will the carbon dioxide be limiting to growth. In fact,the situation in the

heated water from a power plant might offer the specific conditions required.

Since the carbon dioxide content has a certain relation to pH value and since

the pH is raised during the production, in a thermally polluted area, in

bright sunlight, in shallow water and with a heavy primary phytoplankton production

there might create a situation where carbon dioxide is depleted.

Oxygen is one of the gases that will become over-saturated when the

water is heated at the passage through the power plant cooling syBtem. Oxygen

is also involved in quite a different way in being produced in the water through

the photosynthetic process. As this production takes place within the water,

at the depths reached by visible l ight , i t will cause an over-saturation.

During periods of intense production this over-saturation can be considerable.

The oxygen over-saturation observed in thermally polluted 'Vater Is thus often

a combined effect of direct heating and production. In general, over-saturation

of oxygen is a greater drawback in nature than under-^arturation i s . Complete

consumption of the oxygen, which of course is detrimental to the animal l i fe

at that location,is restricted to certain stagnant areas, mostly in deep vater,

whereas over-saturation of oxygen causing damage to the marine l i fe is a wide-

spread phenomena in the upper photic lone of the seas during periods of high

primary production.

Light is the energy form driving the photosynthesis on which al l plant

l ife on earth is dependent. In the marine environment the penetration of

light into the water is dependent on several factors. However, temperature

itself does not affect light penetration to a measurable extent. Instead,

secondary effects may have an influence. The higher water temperature will

increase the solubility of most solid compounds, which in turn may increase the

absorption of light. The high temperature will stimulate a high biological

activity with the formation of partieulate matter and light scattering and

-6-

shading as a consequence. The increased phytoplankton growth may ultimately

reach a level -where self-shading occurs, thereby limiting a further increase

in the protraction. In general, hovever, light should not be limiting to

plant growth at shallow vater depths ,• even under the extreme conditions of

heated water. Evaporation of waxer is promoted by high water temperature.

The air above the surface of heated vater may easily achieve the saturation

value for water vapour. If such air is cooled, water vapour vill immediately

condense to form droplets and the formation of fog can be seen. Although the

fog might be a serious practical drawback for certain activities at sea, it

will not necessarily affect the production in the water. Fog vill probably

decrease the amount of available light but,on the other hand,will appear

mostly when the direct solar radiation is absent for other reasons, so this

effect is probably marginal. A direct effect of the additional heat to the

vater vill be a delayed or prevented ice coverage. The main consequence of

this will be an important change of light conditions. An ice cover which in

turn is covered by snow will provide a practically opaque top, in normal

winter conditions .leaving the water below in almost complete darkness. The

absence of ice, on the other hand, will expose the water to daylight and

thereby provide the energy conditions required for a continued production,

particularly in shallow water.

Climate can be considered to be the long-time aspect of the

weather. It has been argued that a continued outlet of heated water may lead

to a local change of climate. Although such a change may be serious to aany

human activities,only the production aspects vill he considered here. The

effects an the ecosystem iu the long run a.re difficult to foresee. The time

for stabilization and reaching of a steady state is probably in most cases

longer than artificially heated water outlets have existed in man's

history. The effects considered so far are mainly the direct, physical

changes connected to the increased water temperature. It is r,e« tiir.e to

deal with the different biological responses to these effects. These

responses might in some cases appear immediately, whereas others will develop

during several years. For example,can the number of decomposing bacteria

be expected to closely follow the increased temperature and supply of organic

material, while the disappearance of certain fish species may take several

years. The rich branching of the marine food web and the long pathways of

interaction between different phenomena vill provide a long time for the

formation of some of the responses. And after they are recognized, still more

time is required to achieve a steady state. Bear: r.p in rind the presumption

that we are dealing with a continuous outlet of heated water, and the knowledgenay

th&- a nuclear plant is likely to have closing-down periods, a steady statejfnever

be achieved. This implies that the long-time aspects of the heated vater

outlet is a repeatedly disturbed ecosystem in an ever changing state of

unbalance.

The pilot study at Simpevarp

Determination of the primary production rate using C has been

carried out vith approximately 2 week intervals since Ray 1975 at two stations

near Simpevarp. One station is in Haimefjerden a semi-enclosed basin outside

the cooling water outlet from the nuclear power plant Oscarshamnsverket, in

the heated outlet water. The other station is at Tallskar near the intake

of cooling vater to the power plant, in vater which is unaffected by the heat

from the power plant. Due to the relatively short time for the passage of the

cooling water through the reactor, the measurements will be carried out on

samples from, in practice, the same water before and after heating. The water

depth at both locations, being coastal bays, is only about 5 metres. The

production is determined at depths of 0,1,2,3 and It.metres. Dark bottles for

determination of the dark production are applied at depths of 0, 2 and h metres.

Results and discussion

The measurements of primary production at Simpevarp will continue

also in the near future. The data obtained so far are presented in diagram

form below. An integration of the data has been carried out in the vertical

at each station and then in time. From this operation the production rates

at the two stations can be estimated to "be 17.6 gC/m in heated water and

to be 12.1 gC/nf- in unheated water, for a period extending from 17 May 1975

to 20 August 1975, i.e. for approximately 3 months of the production

season. The continued measurements will provide data for an estimation of the

annual p ro ducti on,

The value in the unheated vater is a high value for production in this

area. This is probably caused by the close vicinity to the coast since,

for many reasons, there is usually a gradient of increased production towards

the coast in natural waters. The fact that both intake and outlet measurements

are carried out in shallov bays with a vater depth of approximately 5 u will

give a very high light exposure rate and thereby contribute to a high production.

-8-

There is also a possibility of influence from the pcwer plant, In toat the

wwter movement towards the cooling water inlet might provide a. somewhat better

nutrient situation, through a continuous supply from the outer area, compared

to a completely unaffected area.

PThe relation — ss 1.5,vbi«h means that the primary production in

ISheated water is 1.5 times that of uDheated vater during the measurement

period. The possible causes of this are touched upon in the preceding text.

All the biological responses to the physical changes mentioned are certainly

not known. The control of growth in nature is normally a blade-edge balance

between interacting mechanisms. Grazing, stimulation by growth factors,

repression by chemical agents, may serve as examples. That heat alone should

increase the growth rate by 50$ is not very nicely. Some observations indicate

that the zooplankton are to a. large extent injured or dead after the passage

through the power plant, while the phytoplankton for the most part are functionally

and constitutionally unaffected. Kov, it has become evident that not only

phytoplankton control the zooplankton by constituting the available food and

that zooplaakton control the phytoplankton by grazing, but also that there

are more sophisticated ways, basically chemical, to maintain the very delicate

balance between different species. However, if e large part of the zooplanktonthrough

are Btruek out by passing^the cooling system, the mutual control mechanism is

disturbed and an abnormal growth can take place, larger animals such as fish,

Jelly fish etc.,will often get crushed during the passage through the plant,

and,for example,sea gulls can be seen feeding on this material outside the

outlet. But this also means that nutrients are brought back to the water

which might further promote growth of the phytoplankton,resulting in a higher

production.

Since higher organisms are more complicated than lower organisms,

such as plants, there is also e possibility that the intact part of the zoo-

plankton becomes functionally inactivated by the sudden temperature increase

during the pa£Bage,whereas the phytoplankton can immediately benefit from

the, in their case, improved conditions.

Conclusively, the considerably higher production rate in • heated

water compared withthe unheated indicates a strong local perturbation of the

ecosystem balance caused by the outlet of cooling water. It also indicates

that primary production measurements can be a useful tool to monitor these

perturbations et an early stage.

. ACKHOWLEDGMEHTE

The work was carried out on behalf of the national Swedish

Environment Protection Board. The first measurements with C labelling

were carried out by the author, while the later, greater part of this work <

which is gratefully acknowledged, has "been carefully carried out by BiS. ,

H&fcan Sten"ba.ck, The author would like to thank Professor Abdus 3a]am, the

International Atomic Energy Agency and UffESCO for hospitality at the

International Centre for Theoretical Physics, Trieste, where a. part of the

theoretical research has been carried out. The stay at the ICTP was made

possible by a grant from the Swedish National Board for Technical Development.

-9--10-

LITERATURE

Genera l

Listed below is l i te ra ture not specifically cited in the tex t , 'but of

general reference character for those interested in looking into the offsete of

thermal pollution. These effects are relevant to the entire aquatic ecosystem

and thus not res t r ic ted to primary production.

J . Clark and W. Brownwell, 1973. Electric pover plants in the coastal

zone: Environmental issues, American Lit toral Society Special Publication

Ho .7.

W. Drost-Hansen and A. Thorhaug, 197*1, Biologically allowable thermal

pollution l imi t s , Parts 1 and 2, US Environmental Protection Agency Report

EPA-660/3-7i*-003.

Effects of heated effluents on aquatic organisms and other aspects

of water pollution, 1971, Central Electrici ty Generating Board Information

Services, Ref.Ro. CE Bit.213.

Freshwater and estuarine studies of the effects of industry, 1972,

Proc. Boy. Soc. Series B, No.J,06l.

J.W. Gibbons and E.H. Sharitz (Eds.), 1971*, Thermal ecology, US Atomic

Energy Commission, Techn. Inf. Centre.

A.B. Lindo, e t a l . , 1973, Cooling water discharges and their relation

to the environment, Union Internationale des Producteurs et Distributeurs

d'Energle Eleetrique, Paris , Congrea de la Haye, Nuclear Energy Study

Committee Paper 10.

J. Jtargon, 1973, Index bibliography of thermal effects l i t e ra tu re ,

Oak Ridge national Laboratory, Nuclear Information Centre, Report Bo.ORNL/NSIC/110.

E.C. Kaney and B.W. Menzel, 1969, Heated effluents and effects on

aquatic l i fe with emphasis on f ishes- A bibliography, Cornell University

Water Resources and Marine Services Centre, Philadelphia Electric Company

and Ichtyological Associates, Bulletin Bo.3.

M. Roessler and D.C. Jabt>, 197^, Studies of effects of thermal

pollution in Biscayne Bay, Florida, US Environmental Protection Agency Report

EPA-66Q/3-TU-O11+ -

-11-

The pilot study

Literature of relevance to the performance and calculations of the

primary production measurements Is l i s t ed below.

K. Buch, 1951, Das Kohlensaure Gleiehqewichts-System in Meervasser,

Havsforsknings Ins t i tu te ts Skrift JTo.151, Helsinki.

H.W. Harvey, 1966, The Chemistry and Fer t i l i ty of Sea Waters (Cambridge

University Press).

B. Hstrom, 197^, An algorithm for the computation of primary

production, Botaniea Marina, Vol.17.

E. Steeman Hielsen, 1953, Experimental methods for measuring Organic

production in the sea, Eapp. et Proc. Verb. Vol.lUlt, Interaat . Couns.

Explor, Sea.

-12-

* • «

FIGUBE CAPTIONS

Figs.1-7 These figures show the primary production close to the

inlet (fine line) and the outlet (thick line) of cooling

vater to a nuclear power plant on the Swedish Baltic

coast, latitude approximately 57 north. The valueslU

are obtained by C labelling of the water, in situ

exposure and subsequent radioactivity measurement of

the organisms. The data are calculated in units of

carbon converted from inorganic C0p into organic cellular

tissue per solar day and vater volume. Each figure

represents a measurement occasion and the respective

dates in 1975 w e given on the figure.

Fig.8 This figure Bhows the vertical Integration of Figs.1-7

giving the primary production per unit area in the upper

h metres of the vster column. Subsequent integration

along the time axis allows the estimation of

the increased primary production in units of carbon,

giving information on an effect of continuous outlet

of heated water-

-i

fft*

25

Primary production |mg C/m* and day]50 75 100

Simpevarp

750517

heated waternot heated water

Depth {meter]

- 1 4 -

f Depth [meter]

Primary production [mg C/m3 and day!

100

heated waternot heated water

1 i

* Depth {meter]

Primary production Jmg C/ffl* and day]

50 75 100

Simpevarp750617

heated waternot heated water

I*

"hfi. 1 . 3 Ft

I*

f Depth [meter]

Prbnary production Jmg C/im3 and day!

50 75 100

Simpevarp750701

heated waternot heated water

-it-

1 -

Primary production imgC/m* and day]

50 75 100

Simpevarp750722

heated water ,not heated water

-4.V-

Primary production jrng C/m 3 and dayl

100

Simpevarp

750805

heated water

not heated water

[Depth [meter]

11

Primary production fmgCyAn" and day]

25 50 75 100

\

Depth {mater]

Simpewrp750820

heatednot heated water

CURRENT 1CTP PUffRINTS Mt^

f Primary production Tmg C/m* and day]

260240220200180160140120100806040200

heated waternot heated water

MAY JUNE JULYi

1975AUG. Day number

120 130 140 150 160 170 180 190 200 210 220 230 240

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; .C : PATI and ABDUS EALAM: Mirroi fermioni,the J/^pulticks acu Kolar-mine events.

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