the oxygen content of interstitial water in sandy shores

The Oxygen Content of Interstitial Water in Sandy ShoresAuthor(s): A. E. BrafieldSource: Journal of Animal Ecology, Vol. 33, No. 1 (Feb., 1964), pp. 97-116Published by: British Ecological SocietyStable URL: http://www.jstor.org/stable/2351 .

Accessed: 01/05/2014 17:44

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal ofAnimal Ecology.

http://www.jstor.org

This content downloaded from 130.132.123.28 on Thu, 1 May 2014 17:44:28 PMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=briteco

http://www.jstor.org/stable/2351?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


97

THE OXYGEN CONTENT OF INTERSTITIAL WATER IN SANDY SHORES

BY A. E. BRAFIELD

Queen Mary College, University of London*

Several field investigations have been made into the nature and variations of environ- mental factors in the beach, both physical and chemical. The classical survey of such factors was made by Bruce (1928a, b). Other authors, for example Reid (1932), Perkins (1957), Chapman (1949) and Webb & Hill (1958), have studied specific factors in more detail than Bruce, such as salinity, the black layer, thixotropy, and the relationships between sand grain size, pore space, and drainage. Investigations into the oxygen content of the interstitial water, however, are rare.

The scarcity of data concerning the oxygen content of the interstitial water is clearly demonstrated by the fact that Deboutteville (1960) in his extensive volume on the fauna and ecological factors of both freshwater and marine beaches, is compelled to deal with the oxygen content of the latter in one sentence: 'Le taux d'oxygene dissous dans les eaux interstitielles ou souterraines littorales est encore fort mal connu.' The oxygen regime existing in lakeside beaches is rather better understood, chiefly as a result of the studies by Wiszniewski (1934), Pennak (1940, 1951) and Angelier (1953). Unfortunately these workers gave few details of their methods of analysis. Nor did they report other features such as the grain size distributions of the beaches studied.

A summary of studies on the oxygen content of marine beaches is given in Table 1. All except those of Jones (1955) are rather imperfect, either because the method of collecting the water sample was such that atmospheric oxygen was allowed to invade the sample, so causing errors of unknown size, or because the method of analysis failed to take into account the sources of error arising from the possible presence of chemical pollutants in the beach. The temperature of the samples was not always given. Jones (1955) used a reliable method, but a rather lengthy and cumbersome one. He gave few details of the physical characteristics of the beaches.

Consequently it was considered necessary in the present work on the oxygen content of the interstitial water of marine beaches to attempt three main objects. Firstly, to devise a reliable method whereby samples of interstitial water could be collected without exposing them to the air at any stage. Secondly, to establish a reliable method of determining the amount of dissolved oxygen in an interstitial water sample. Such a method, which takes due account of all the potentially disturbing factors, was devised and used in nearly all the studies undertaken. Thirdly, using these methods of collection and oxygen determination, to make accurate investigations of the oxygen content of a number of beaches under differing conditions, in an attempt to discover the relative importance of the various factors which affect the oxygen content and control its level.

THE COLLECTION OF INTERSTITIAL WATER SAMPLES

To obtain accurate values for the oxygen content of the interstitial water of beaches a precise sampling procedure is necessary. Ideally the water samples should be kept out

* Present address: Queen Elizabeth College, University of London.



98 Oxygen in sandy shores

of contact with the air at all stages, to avoid errors arising from the invasion of atmospheric oxygen. This is particularly important when the oxygen content may be small. A reliable sampling method should also ensure that as little sand and silt as possible is

Table 1. Summary of the methods and results of previous work on the oxygen content of marine beaches

Author Method of Locality Depth of Oxygen content Details of sand analysis samples (ml/l)

Bruce Winkler as Port Erin, Below 10 cm 1-81 Sand black below (1928b) modified by Isle of Man 10 cm; 95 % of

Fox (1905) sample between 025 and 0125 mm

Borden Unmodified Batten Bay, 30 cm 002-027 (35 values) Sand black below (1931) Winkler Plymouth half an inch

Thamdrup Winkler as Skalling - 000-294, average Sand black or grey; (1935) modified by peninsula, 1 30 (23 values from usually 85-95 % of

Alsterberg Denmark 11 sites) sample between 0-5 (1926) and 0-1 mm

Pearse, Unmodified Beaufort, 017-5 cm at Averages 1P90, 1-01, About 950% of Humm & Winkler North 1 in. (2-5 cm) 028, 0-29, 0-20, 0-35, sample between Wharton Carolina intervals 000 and 000 05 and 0-1 mm (1942) respectively

Pennak Unmodified Two beaches (Distance from (1942) Winkler at Woods water's edge in

Hole, Mass. parentheses) Nobska 8 cm Average 5 04 (0 cm), 'Only small

average 4-83 (100 cm), quantities of organic 2d17 (175 cm), 4-97 matter' (200 cm)

Penzance 8 cm 1 40 (0 cm), 0-56 'Much particulate (100 cm), 0-49 organic matter' (150 cm)

Angelier Unmodified Baie du Troc, - Average 2-8 (1953) Winkler Banyuls

Ishida Unmodified Four beaches 4 cm 0-35 and 1P05; 3-62, (1953) Winkler in Japan 5-46, 5-46 and 4-95;

1-54 and 2-26; 4-54 and 5-27 respectively

Jones Winkler as Three beaches (195-5) modified by in Yorkshire

Alsterberg Robin Hood's 7-5-15 cm 0-11-035 (12 values) (1926) Bay

Filey Sands 7 5-15 cm 0-27, 0 33, 0-22, 0-24 Old Harbour, 7-5-15 cm 0 35, 0-27, 0-24, 0 33 More silt and Scarborough organic matter than

the other two beaches

collected with the water, to minimize the interference of disturbing chemicals in the oxygen estimation. Furthermore the water should be drawn only from the required depth, and not from any better oxygenated water which may be lying above. Finally the



A. E. BRAFIELD 99

apparatus should be strong enough to penetrate beaches containing stones and shingle as well as sand and mud.

No method which has been encountered in the literature fulfils all these requirements. Bruce (1928b) drained the interstitial water from a quantity of sand obtained by taking a vertical core sample with a brass cork borer. No allowance for the invasion of atmospheric oxygen was made. Borden (1931) used an iron tube closed at the lower end, bearing a double row of holes near the bottom and a spiral spike to aid penetration. Her method involved errors arising from the invasion of atmospheric oxygen which she estimated and found to be considerable. Cole (1932), working on freshwater lakes, used a glass cylinder bearing a long glass tube at the upper end and a cone of 'alundum' over the lower end. Water filtered through the cone and rose in the tube, under paraffin oil, owing to the difference between the air pressure in the tube and that of the surrounding water. On a beach, where there is an insufficient head of water, the method could not be applied. Wiszniewski (1934), also working on freshwater lakes, collected interstitial water by means of a pipette covered with gauze, later transferring the samples to bottles. It is not clear whether air was completely excluded at all stages. Pennak (1940), investi- gating the beaches of Wisconsin lakes, used a very similar method of collection. Thamdrup (1935) used a cumbersome and rather complex apparatus. He was not able to guarantee the level from which each sample had been collected, nor was air excluded at all stages. Pearse, Humm & Wharton (1942) made some measurements of the oxygen content of beaches, but gave no details of the sampling methods used. Neither did Angelier (1953). Ishida (1953) used a glass tube with the lower end covered with a piece of silk. Water collecting in the tube was removed with syringes for analysis. Apparently no attempt was made to exclude air. Finally, Jones (1955) used a narrow steel cannula attached to a syringe. The lower end of the former was open, and bore a brass wire carrying a cup of solder below the opening, to assist penetration and to prevent sand being rammed into the cannula. A pellet of cotton wool lying between the cup and the lower end of the cannula acted as a filter of some of the silt. The apparatus excludes air at all stages, but is of limited strength and reliability, and could probably not be used on very stony beaches.

Originally a brass apparatus was used in the present work, consisting of a tube 40 cm long, of 0 5 cm internal diameter. The lower end bore a brass cone which assisted penetration into the sand. A brass rod passed through the tube, bearing a tightly fitting plug. Four holes piercing the tube permitted the entry of interstitial water when the apparatus was pushed into the sand and the plunger slowly withdrawn. A strip of bolting silk, bound and glued round the base of the apparatus, over the holes, prevented the entry of all but the finest grains of sand. When the plunger plug became worn it would be removed and a new one fixed. Plugs were made either of nylon or of polytetrafluoroethylene (trade name 'fuon'). The latter is a tough self-lubricating material, which was found to retain a tight fit for longer than other materials. Samples obtained with this apparatus were ejected into small glass phials and taken from these into a Fox & Wingfield syringe pipette for oxygen determination. This brass sampling apparatus was not entirely reliable, and an improved sampler was devised and used in all later work.

This apparatus (Fig. la) is composed of three stainless steel sections-a connecting tube (A), a filtering cylinder (C), and a penetration cone (F), which screw together. Holes pierce the lower end of the cylinder (D), allowing interstitial water to enter the latter when the apparatus is in use in the beach. The cone helps penetration into the sand. When assembling the apparatus for use the cylinder is filled with cotton wool and then screwed into the cone. A ring of brass gauze (B) is placed on a ledge at the lower end of




the connecting tube and clamped in place as the cylinder is screwed tight. The cotton wool serves to filter off the fine sand and silt. The gauze keeps the cotton wool in place. The cone is pierced with holes to match those at the base of the cylinder, so that water may be drawn into the very bottom of the latter, thereby preventing the presence of a dead space of air in the region E in Fig. 1, from which oxygen might invade the water as it was being collected. The cylinder, being open at both ends, can easily be emptied of dirty cotton wool. The channel in the connecting tube is narrow to minimize the volume of the apparatus. The holes in the cone are larger than the corresponding ones in the cylinder, so that when the cone is tightly screwed up it is unlikely that the two sets of holes will not correspond.

When assembled the apparatus is pushed vertically into the sand to the required depth. As the holes are all close to one another water may be collected from the required depth

(c)

A

B A c

D

Do 0 (b)

FIG. 1. (a) The apparatus used for withdrawing interstitial water samples. (b) The device whereby identical amounts of reagents are drawn into the syringe pipette with each turn

of the head screw. (c) The apparatus (a) in position in a beach (see text for details).

precisely. If the beach is rippled, with surface water lying in the furrows, the apparatus is inserted through a ridge to avoid better oxygenated water running down beside the cylinder and entering the system. It is also possible that water is drawn up from greater depths, but this is unlikely. And as such a small sample is taken it seems reasonable to assume that all the water in a sample has come from the desired position.

The sampling procedure is as follows. When the apparatus is assembled and in the required position in the beach a short length of rubber tubing carrying a screw clip (C in Fig. lc) is pushed on to the upper end, and the nozzle of a 10 ml syringe inserted in the upper end of the tubing. The clip is unscrewed and the syringe plunger withdrawn. Water is thereby drawn from the beach into the syringe, together with the air which was present in the apparatus. The clip is closed, the syringe detached at B, and the air within it totally expelled. (The eccentric position of the nozzle allows all air to be easily expelled



A. E. BRAFIELD 101

if the syringe is held in the appropriate position.) The syringe is then re-inserted in the tubing and filled with water by opening the clip and withdrawing the plunger. The clip is then screwed up tightly and the syringe and tubing detached at D. Another syringe, tubing and clip can then be used to take another sample. By this method water samples can be collected in the syringes without coming into contact with the air at any stage, and are generally free of fine sand and suspended matter. The apparatus is extremely strong and can readily be forced into compact shingle beaches. The rubber tubing on the sample syringes is of such a size that the capillary nozzle of a Fox & Wingfield syringe pipette fits tightly into it. Consequently when a sample is to be analysed the syringe pipette can be inserted into the rubber tubing on a syringe, the clip opened, and the appropriate amount of interstitial water withdrawn.

THE MEASUREMENT OF THE DISSOLVED OXYGEN

A chemical method of oxygen analysis was used, because tonometric and gasometric methods are not suitable for use in the field. Polarographic methods are not yet suffi- ciently developed for reliable field use because they cannot be calibrated in a suitable way to reveal dissolved oxygen levels as distinct from the general electrical potential occurring in a chemically polluted beach. A modification of the method devised by Winkler (1888) was used, the tests being conducted with the syringe pipette devised by Krogh and modified by Fox & Wingfield (1938), both because air is excluded at all stages and because a water sample of about 1.5 ml is sufficient. Samples of interstitial water can conveniently be drawn into this syringe pipette from the sampling syringes described above. The apparatus proved robust enough to stand use on the beach, and so the modification described by Whitney (1938), which is stronger but more bulky, was not used. The apparatus of Barnes (1953) is also bulky, and that of Harper (1953) does not exclude air at all stages.

In Winkler's method of analysis each atom of dissolved oxygen in the water sample finally liberates a molecule of iodine. The iodine is titrated against sodium thiosulphate solution, using starch as indicator. Titrations were generally done in the field, using an Agla microburette. It is essential that determinations of the oxygen content of the interstitial water be conducted immediately the samples are obtained, for delay brings changes in the amount of iodine liberated. Nor is it adequate to liberate the iodine immediately but conduct the actual titration later, for the amount of iodine present steadily decreases.

Various substances which are frequently present in the polluted water of badly drained beaches can interfere with the Winkler reactions, causing inaccuracies. Nitrite catalyses the liberation of iodine from the iodide, causing readings to be too high. It can be eliminated by adding sodium azide to the alkaline iodide solution (Alsterberg 1925). Ferric salts also exaggerate the apparent amount of oxygen present by interacting with the iodide. This can be avoided by using phosphoric acid, instead of sulphuric acid as suggested by Winkler, for the final acidification (A.B.C.M.-S.A.C. Committee 1957). Phosphoric acid also avoids the production of free iodine which occurs when an alkaline iodide solution mixes with sulphuric acid (Fox & Wingfield 1938), and so was used in the present work. Sulphides and ferrous iron, on the other hand, cause readings to be too low; the sulphides by decreasing the amount of iodine liberated, and the ferrous iron by reducing the manganic hydroxide back to manganous hydroxide (the late J. H. Oliver, personal communication). Alsterberg (1926) dealt with the effect of sulphides by a lengthy and cumbersome method involving bromine.




None of these modifications was thought adequate for the present work because several pollutants, in relatively large quantities, may be expected in a badly drained marine beach. And the application of more than one modification would limit the usefulness of the method as a whole. Consequently a variety of the 'iodine-difference' method was used, because it can accommodate all the factors which might interfere with the Winkler reactions and lead to inaccurate results. In this procedure identical quantities of a solution of potassium iodide are added to each of two identical water samples, one of which is then subjected to the normal Winkler procedure, the other to a 'blank' test in which one of the Winkler reagents is omitted. In the present work distilled water was substituted for the manganous chloride in this test. Now since in the 'blank' there is no iodine equivalent to the dissolved oxygen, and since the alteration in the amount of iodine by the disturbing substances (whether a resultant increase or decrease) is the same in both cases, the difference between the two titres is exactly equivalent to the amount of dissolved oxygen.

The iodine may be added to the original sample before it is split into two identical parts for analysis (Beadle 1958), or it may be incorporated in the alkaline iodide solution (Adams, Barnett & Keller 1943). As in the present work only small samples of interstitial water were available it was considered impracticable to add a drop of iodine solution to the sample first and guarantee complete and rapid mixing such that identical amounts would be taken into the syringe pipette in the Winkler test and in the 'blank'. Iodine was therefore included in the alkaline iodide solution, 1 ml of iodine solution (4 g of iodine and 6 g of potassium iodide to 100 ml with distilled water) being added to 25 ml of the alkaline iodide solution. The concentrations of other reagents were as recommended by Fox & Wingfield (1938). As it was essential that identical quantities of iodine be added in the Winkler test and in the 'blank' a device was fitted to the syringe pipette which ensured that the iodized alkaline iodide solution was taken in by precisely two turns of the head screw in each and every case. This fitting, devised by Professor H. Munro Fox and described here with his permission, is shown in Fig. 1(b). At each turn of the head screw the spring-loaded catch B slips into the cavity C. It can be removed and the head screw turned again by pulling out the upper end of the catch (A). The device is firmly clamped between the two lock nuts of the syringe pipette in such a way that the catch contacts the cavity when the head screw is fully screwed in. Water is easily drawn from the sampling syringes into the syringe pipette, a complete test (a Winkler test and a 'blank') being carried out with each syringe. The Winkler test is always done first, since once it is completed invasion of oxygen from the air need no longer be avoided, as the 'blank' is not concerned with the dissolved oxygen.

Ohle (1953) found that in fresh water containing much suspended matter the amount of free iodine left in the 'blank' became progressively less the longer the interval between adding the alkaline iodide solution and the acid. Therefore, the longer this interval the greater the apparent amount of oxygen. Ohle considered this to be due to the fact that in the Winkler test particulate matter was carried down with the precipitate and that its reducing effect on the iodine and hypoiodite was thereby diminished in comparison with the 'blank', where the absence of a precipitate allowed the reducing effect to continue unchecked. Beadle (1958) has shown that this source of error is not eliminated by reducing the time taken over the operation to a minimum. In the present work with sea water, however, it has been found that a precipitate is produced in the 'blank' also, probably due to the formation of calcium and magnesium salts. Thus in the case of sea water a precipitate occurs in both the Winkler test and the 'blank' and consequently Ohle's source of error does not arise.



A. E. BRAFIELD 103

To make accurate determinations of dissolved oxygen two further points must be borne in mind. Firstly the water samples must be clear of suspended material before conducting a Winkler test, and secondly allowance should be made for oxygen dissolved in the reagents. With regard to the first point it was fortunate that samples collected by the method described earlier did not need preliminary clarification, though an efficient chemical method exists in which suspended matter is cleared by flocculation (Beadle 1958). An alternative method also inhibits bacterial utilization of oxygen (Ellis, Westfall & Ellis 1948). The latter hazard was avoided in the present work by conducting the tests immediately the samples were collected.

A correction for the oxygen dissolved in the reagents must be made when the Fox & Wingfield syringe pipette is used, because the volume of the reagents is large compared with the volume of the water sample. The correction becomes increasingly significant at lower oxygen concentrations such as those found in the present work. Two methods were used to determine the volume of sodium thiosulphate which must be deducted from the final titre to allow for oxygen in the reagents. The first involved calculating the volume of the syringe pipette occupied by the reagents and applying the figure of 5-4 ml of oxygen per litre of reagents quoted by Fox & Wingfield (1937). The result suggested that in the present work 0-008 ml of N/80 sodium thiosulphate is used in allowing for the oxygen dissolved in the reagents. In the second method Winkler tests were conducted using firstly normal reagents and secondly reagents made up in nitrogenated water. The mean difference between the two sets of titres then represented the sodium thiosulphate used in allowing for the reagent oxygen. This was found to be 0 003 ml, much less than the value of 0-008 ml obtained by the first method. The discrepancy could be explained if the reagents used in the present work were not fully aerated. In any event, in this work 0 003 ml of sodium thiosulphate has been deducted from the total titre in oxygen determinations to allow for oxygen in the reagents. When using the iodine-difference method this correction is deducted from the Winkler test titre but not from the 'blank' titre, for there is no iodine corresponding to dissolved oxygen in the 'blank'.

A COMPARATIVE STUDY OF VARIED BEACHES (ISLES OF SCILLY)

The Isles of Scilly were chosen for this comparative investigation because they afford a wide variety of suitable beaches within a relatively small area, and because laboratory space and boat transport were readily available, thanks to the kindness of Professor L. A. Harvey. Four sites on St Mary's were investigated. Porthloo (station A) is largely a rocky bay slightly protected in spite of its westerly aspect by a narrow islet at either end. A central expanse of sand among the rocks was studied. Between Porthloo and the harbour of Hugh Town lies a sandy bay (station B) which at the time was covered with the fine black debris of decomposing Zostera. Two stations in the harbour itself were investigated. One, an area of fine mud in the lee of the jetty (station C) and the other an expanse of gravel near the centre of the harbour bay (station D). On Bryher two sites were studied, the small bay below the freshwater lake called the Pool (station E) and a smooth mound of firm sand among the flats exposed at low water below the Town (station F). Tresco also afforded two stations-the very extensive sand flats in Pentle Bay (station G) and the steep sandy upper shore in the sheltered harbour of Old Grimsby (station H). A sandy region behind Moths Lodge (station I) and a rather muddy area below Lower Town (station J) were studied on St Martin's.




Methods At each station the depth at which a grey or black discoloration of the sand appeared

was measured. In all cases the temperature at a depth of 5 cm was recorded at the time of sampling. Notes were made on the nature of any surface water present. On flat beaches this was usually in the form of ribbon pools between the sand ripples, but irregular pools occurred on muddy and less exposed areas. Small rivulets were common on sloping beaches, and at station H these were probably of fresh water. The significance of this will be discussed later.

Samples of interstitial water for oxygen determinations were obtained in these earlier studies by means of the original brass apparatus. They were taken from a depth of 5 cm except at station J. At this site a black layer began at a depth of 1-2 cm but ended at 5-6 cm owing to the existence below this depth of very coarse gravel. In this case samples were taken from 3 5 cm. Samples were immediately ejected from the apparatus into small glass specimen tubes, thus allowing contamination by atmospheric oxygen, but it will be shown that this source of error was negligible when the following precautions were taken. (Ejecting the water under various oils had proved unsatisfactory.) The tip of the apparatus was inserted into the tube when ejecting the sample, and the plunger depressed slowly and evenly so that the water flowed from the holes in the apparatus rather than spurting out and thereby encouraging aeration. The water rose above the level of the holes almost immediately, and thereafter the area of the air/water interface was equal only to the cross- sectional area of the tube minus that of the sampler. When the water surface reached the top of the tube the apparatus was withdrawn without ceasing the flow of water from it, thereby filling the tube completely. The latter was then corked, care being taken to exclude air bubbles.

Harvey (1955) quotes an equation for the invasion of atmospheric oxygen into water, which takes into account water temperature; oxygen concentration of the water when saturated with air at the temperature and salinity in question; oxygen concentration of the sample; interface area; and the length of time during which invasion can occur. Substituting for these terms values of 180 C, 6 ml/l, 0 ml/l, 0 5 cm2, and 30 sec, respectively yields a value for oxygen invasion of 0-00078 ml of oxygen. This was considered negligible.

Titrations were conducted in the field, always within 10 min of collection. Several samples were titrated at each station, and an average taken. Ordinary Winkler tests were used in these studies as the 'iodine-difference' technique had not yet been perfected. Probably small inaccuracies occurred as a result but it is not felt that they were of great significance in this instance, because all samples were treated similarly and the aim of this investigation was primarily comparative.

Samples for grain size analysis were collected from a depth of 5 cm. They were not allowed to become dry as this might affect the degree of aggregation of the finer particles. In the laboratory the samples were sieved with a little fresh water because the weight of the sea water salts is added to that of the grades if they are not leached out. Square- meshed sieves with mesh sizes of 4, 2, 1, 0 5, 025, 0d125 and 0-062 mm were used in suc- cession. Sieves conforming with the Wentworth scale were used in deference to the plea by Morgans (1956) for standardization. Material retained by each sieve was washed into a petri dish and the dishes were placed in an oven at 105? C overnight. The fractions were then weighed. The cloudy water passing the finest sieve was filtered through a dried and weighed filter paper to collect the material with a grain diameter of less than 0062 mm. This fraction could then be weighed without removing it from the filter paper.



A. E. BRAFIELD 105

The weight of each fraction was expressed as a percentage of the whole sample and from these results a cumulative percentage curve was drawn for each sample (Fig. 2). To simplify statistical treatment the concept of the phi scale was adopted, which sub- stitutes a logarithm for each particle diameter, thereby equating the unequal intervals of the Wentworth scale and allowing the cumulative curve to be plotted on normal graph paper instead of semi-logarithmic paper without changing the shape of the curve (see Morgans 1956). The median, Md# (the phi value corresponding to the 50% level) can be transposed to a diameter in mm and as such to a certain extent represents in one figure the characteristics of the whole beach sample. Half the substrate is of smaller particles than the median and half of larger particles. A measure of the slope of the curve is the phi quartile deviation, QD#. It is equal to i(Q3#-Q1l) where Q3# and Q1# are the phi values for the third and first quartiles (i.e. at the 75 % and 25 % levels respectively). If QD# is small, nearly all the sample is of one grain size, but if large several grain sizes are prominent (for the significance of differences in this statistic for various beaches see p. 109).

No systematic digging or sieving was done to find the species inhabiting each station in this investigation, but when turned up in the course of measuring the depth of the black

100-

CL-Ai'~~ /

75 - 0

* 1/ ~~~~~~~~~F Y.50

-

25-

P H I, SCALE

FIG. 2. The cumulative curves for substrate samples from the ten sampling stations in the Isles of Scilly.

layer or the sand depth their presence was recorded. If Arenicola marina (L.) was present at a station, however, it could hardly be overlooked, and Scoloplos armiger (Muller) always seems plentiful if it is present at all. Absence records for these two polychaetes are therefore probably reliable.

All the sites studied were situated in the lower half of the shore, below mid-tide level, but none was at low water mark. The sand temperature at a depth of 5 cm varied between 16-8 and 19.70 C. Most sites had been exposed by the receding tide for about 3 h, though one (E) had only been exposed for about 30 min and another (D) for over 6 h. This variability in time of sampling was unavoidable, but is unfortunate because in this respect the results are not strictly comparable, for in some beaches the oxygen level may change as the exposure period progresses.

Results The results are summarized in Table 2. The sites have been arranged in order from the

lowest oxygen level to the highest. Values for the oxygen content of the interstitial water are not given in ml per litre but as percentages of the air saturation level (5 5 ml/l at



0

Table 2. Summarized results of the Scilly Isles investigation

Oxygen level Sloping Particle size analysis Fauna Site (percentage of Black layer Surface water or flat r -A - -- r

air saturation) beach Mdb Q3b Q1b QDO % fine Scoloplos Arenicola 'Clean sand sand lamellibranchs' Z

Range Mean A 0 0-00 0-0 Grey-2 cm Pools persisted Flat +2-55 +2-80 +2 25 0 27 98 2 Frequent Occasional - E 15-40 3 0 Black-I cm Pools persisted Flat +0 15 +0 95 -0 90 092 7-2 Abundant Abundant - C 30-4 0 3-5 Black-I cm Pools persisted Flat +2 60 +3-35 +1 00 1 17 71 7 Abundant Frequent - J 7-0-10 0 8-5 Black-1-2 cm Pools persisted Flat +1-45 +2 40 -0 15 1P27 37 1 Abundant - - G 105-120 115 Grey-4 cm Pools drained Flat +140 +190 080 055 185 Occasional - Dosinia, Tellina

later B 75-255 165 Clean Thixotropic at Sloping +260 +290 +225 032 940 - - -

first, dilatant later 0

D 190-240 21 5 Clean No pools Sloping -0 65 +040 -1 60 100 3 4 - - - F 25 5-415 33 5 Clean No pools Sloping -0 45 +0 45 -1-25 0 85 3 7 - - Dosinia I 27-0-52-0 39 5 Clean Very little water, Flat +0 55 +1 10 +005 0-52 5 0 - - Dosinia, Ensis

quickly drained H 640-97 5 81 5 Clean No pools Sloping +0 10 +060 -055 057 2 6 - - Tellina



A. E. BRAFIELD 107

18.50 C and a salinity of 34%O), which were considered adequate for this essentially comparative study. Depths shown in the column headed 'Black layer' indicate the depths at which the discoloration of the sand, if any, began. Values in the column headed '% fine sand' show the percentage of the total sample from each site which passed the sieve with a mesh of 0-25 mm. The species indicated in the final columns are Scoloplos armiger, Arenicola marina, Dosinia exoleta (L.) and D. lupinus (L.), Tellina tenuis da Costa and Ensis arcuatus (Jeffreys).

To find the degree of correlation between the oxygen level and the various factors revealed by the grade analysis, the stations were ranked according to each of these factors, and Spearman's rank correlation coefficient calculated in each case. This coefficient is defined by R= =1_- " where VLd2 is the sum of the squares of the rank differences and n the number of stations. Table 3 shows the values of the coefficient for the

Table 3. Spearman's rank correlation coefficient when oxygen level (ranked from low values to high) is correlated with various parameters

The parameters in the left-hand column are all ranked from high values to low except for the last two, which are ranked as stated; values for t marked * are significant at the 5 % level; that marked #* is significant at the 1 Y. level.

R t

q value at 50% on cumulative curve (Mdq) +0-51 1-68 Mdq omitted 4 mm and 2 mm fractions +0-61 2-20 q value at 75 % on cumulative curve (Q3q) +0-57 1-96 Q3q omitting 4 mm and 2 mm fractions +0 73 3.01* q value at 90% on cumulative curve +0-71 2.84* 100 minus cumulative % at +2q ('Y% fine sand') +0-76 3-34** 100 minus cumulative % at +3qb +0 35 1-06 QDqb +0 09 0-26 QDq ranked 'extremes to centre' +0 54 1-82 Grading of original entire samples by eye, ranked

'fine' to 'coarse' +0 64 2-36*

factors correlated. (The coefficient has a value of + 1 for perfect positive correlation and -1 for perfect negative correlation.) This table also contains the results (column t) of testing the significance of the correlation coefficients by means of the 't test', for which t=Ry,/n-2, with (n-2) degrees of freedom where n is the number of stations. The ranking of QDO from 'extremes to centre' in Table 3 was arrived at by ranking the station with the lowest QDO value 1, that with the highest 2, that with the lowest but one 3, that with the highest but one 4, and so on. The value of this ranking and correlationis discussed on p. 109. Since the most significant correlation in the table is that for the oxygen level and the percentage fine sand these two are plotted against each other in Fig. 3.

For reasons which will be made apparent later the rankings for oxygen level, percentage fine sand, and QDO (ranked 'extreme to centre') were correlated simultaneously in order to estimate the extent of their mutual correlation. This was achieved by calculating the coefficient of concordance, W (see Kendall 1955). In this instance W = 087, which is a significant value, as W varies between 0 and +1, the value of the coefficient increasing with the measure of agreement between the rankings.




Conclusions It has been shown that the temperature did not vary significantly during the course of

the investigation, and so it is unlikely that it affected the oxygen levels being measured. One possible influence, however, is the presence in some cases of rivulets of surface water. At stations B and H these were almost certainly highly oxygenated streams, raising the oxygen content of the interstitial water to a higher level than usual for sands of such a grain size distribution. At station B 9400 of the sand was finer than 0-25 mm, yet the oxygen level was as high as 16-5 00 and the sand was clean; and 81F5 % at station H seems a very high level of oxygenation under any circumstances. The influence on interstitial water of overlying streams is problematical. Reid (1932) considered that the salinity of interstitial water at depths exceeding 1 ft (30 cm) is unaffected by overlying freshwater streams at low tide, but at these two stations in the present investigation such streams have almost certainly affected the oxygen content of the interstitial water at a depth of 5 cm.

100_

0

-50 -

io 0

Z - 0 z

a 0 Q0_ <- O

0 0 50 100

?/ FINE SAND

FIG. 3. The relationship between the oxygen concentration of the interstitial water and the percentage fine sand in the substrate samples, Isles of Scilly. Solid circles indicate beaches

where the sand was blackened.

Well drained beaches may be expected to have better oxygenated interstitial water than poorly drained ones, and this supposition is supported by the results in Table 2, where the presence of surface water pools can be considered as a criterion of drainage. At stations with low oxygen levels the surface pools persist throughout the intertidal period, poor drainage preventing their disappearance. As the drainage improves (and the oxygen level rises) the pools are able to drain away. An interesting intermediate stage is seen in station B, where the surface sand contained a high proportion of water at first, but much less later in the exposure period. Also, as a rule, sloping beaches were better drained and better oxygenated than flat ones. It is also clear from Table 2 that beaches of blackened sand contain less oxygen than those of clean sand. Moreover it can be seen that as the depth of the onset of the black layer increases, the oxygen content of the interstitial water also increases.

The chief factor controlling the oxygen content seems to be revealed by the grain size analyses. The most significant correlation is between the oxygen and the percentage of fine sand. Correlations with the very fine sand and the silt and clay fractions are rather



A. E. BRAFIELD 109

surprisingly low. The correlation with grading by eye is more significant than those with the phi values at the median and third quartile. Correlations with the latter two features are improved if the coarser grades are ignored, which is rather to be expected.

Fig. 3 shows the close relationship between oxygen level and percentage fine sand. It seems that if the amount of fine sand in a beach exceeds 10 % the oxygen content cannot rise above approximately 20 % of the air saturation level. There is no limit to the oxygen level, however, if there is less than 10 % fine sand. The shape of this graph bears a striking resemblance to one of Webb & Hill (1958, p. 412) in which the drainage time of a certain quantity of water through a sand sample is plotted against the percentage of the sample passing a 90 mesh to the inch sieve (equivalent to a 0-28 mm mesh). The drainage time increased sharply once there was 20 % or more fine sand in the sample. The fine sand of Fig. 3 is the amount passing a 0-25 mm mesh sieve, and so the sizes of the two fractions in question are practically identical. It is interesting to note that the percentage of this grain size in a sample bears almost the same relationship to the oxygen level of the interstitial water in a beach (Fig. 3) as it does to drainage time (Webb & Hill 1958). This supports the contention that drainage is a vital factor controlling the oxygen level of a beach.

Porosity, and therefore drainage, is also affected by the relative sizes of the grains present. It is true that interstitial space will be small (porosity low), and consequently drainage poor, if nearly all a sand is of the same grain size; but porosity will also be low if a wide range of grain sizes are present, as the smallest grains will then occupy spaces between the largest. This may explain the good correlation (R = +0 54) between oxygen level and QDO when the latter is ranked 'extremes to centre', since in this ranking an attempt is made to allow simultaneously for both the factors just described. (It will be recalled that a low value for QDO indicates a sample largely of one grain size group, a high value one containing a wide range of grain sizes.) This is a further demonstration that it is chiefly drainage which controls the oxygen content of interstitial water. The high value found for the coefficient of concordance when oxygen level, percentage fine sand, and the phi quartile deviation are ranked and correlated simultaneously supports this view.

VARIATIONS IN OXYGEN CONTENT WITH DEPTH, EXPOSURE PERIOD,

AND SEASON (WHITSTABLE, KENT)

This section considers investigations made at Whitstable, Kent, using the improved sampling technique and the 'iodine-difference' modification of the Winkler test described earlier. The topography of the locality has been described by Newell (1954). The region which received most attention was the expanse of sandy flats west of the harbour. Samples were collected from a point (station A) at about the centre of these flats, a little below mid-tide level. In addition samples were collected from three other regions. A sand sample was collected from each of these four sites and treated as in the Scilly Isles survey. The resultant cumulative curves are shown in Fig. 4(a).

Results obtained from station A are presented in Table 4. The second column shows the length of time the site had been exposed by the tide at the time of sampling. The depth at which the black layer began is shown in the final column. Sand temperatures were taken at a depth of 5 cm.

It can be seen from Table 4 that the thin film of water which overlies the flats throughout the period of tidal exposure is always fully aerated, and often there is more oxygen




present than in air-saturated water. At a depth of only 2 cm, however, the oxygen content is very low, generally about 1 4 ml/l. At a depth of 5 cm in the blackened sand, there is even less oxygen, frequently only about 0 3 ml/l. There is therefore a very rapid decline in oxygen as the depth increases. Table 1 shows that a similar decline was noted by

75-

BZ V.50

- C A

25 A

LA I I I I

-2 -1 0 +1 +2 +3 +4 -2 -1 0 +1 +2 +3 +4 PHI SCALE

FIG. 4. The cumulative curves for substrate samples from (a) the four sampling stations at Whitstable, Kent, and (b) the three in Jersey.

Pearse et al. (1942). The extremely low oxygen content at a depth of only 5 cm is not the result of respiration by the fauna but rather represents the effects of the complex relationship between the bacteria present in blackened sand and chemical reduction processes.

The results obtained in January 1961 are drawn together in Fig. 5, and show that immediately after the station was exposed by the ebbing tide the surface water was

Table 4. The oxygen content of the interstitial water of the sandflats at station A, Whitstable

Hours Temperature Oxygen content (ml/l) Depth of Date exposed in ?C A black

by the - Surface Interstitial water at layer tide Surface Sand water & (cm)

water 2 cm 5 cm

16 Aug. 1960 i 19-2 18-5 5-45 - 029 i-2 2j - 18-8 - - 012, 0-12

23 Sept. 1960 2 - 14-4 - - 0-68, 0-34, 0-40 2-3 24 Sept. 1960 1 - 13-8 - - 0-12, 0-23, 0-17 2-3

2j 16-5 153 10-90 1-06, 1-62 0-17 8 Jan. 1961 1% 4-1 3-8 7-35 1-45, 1-40 0-51 3-4 9 Jan. 1961 i 3-2 3-5 8-03 0-95, 1-06 0-51 3-4

21 5-6 4-9 9-92 2-45 0-56 10 Jan. 1961 i 5-6 4-9 6-12 0-95, 0-79 - 3-4

2 7-1 6-2 9-14 1-45, 1-85 -

saturated with air, but thereafter the oxygen content rose even higher. There is little doubt that this represents the photosynthetic activity of naviculoid diatoms and the like, which migrate up to the surface water as the tide recedes (Aleem 1949), and can be seen lying in masses in the ripple marks on all but the dullest days. It is of interest that in spite of this high oxygen concentration at the surface the oxygen content of the interstitial



A. E. BRAFIELD 111

water at a depth of 5 cm remains unaltered. Even as little as 2 cm below the surface the oxygen content increased only slightly.

At a depth of 5 cm the average oxygen content was 0 26 ml/I in the summer of 1960, and 0 53 ml/I in the following winter. An oxygen concentration of 0 26 ml/I represents 4 6 % of the air saturation level (5 72 ml/I at 170 C and a salinity of 32%o); and 0 53 ml/I represents 7T2 % of the air saturation level (7 26 ml/I at 50 C and a salinity of 32%o). The salinity value is deduced from data obtained on the Whitstable flats by Perkins (1958). The salinity of the interstitial water probably varies very little, though the salinity of the surface water might change during the exposure period as a result of evaporation. That more oxygen is present in the interstitial water in winter than in summer is probably connected with the fact that the depth at which the black layer begins is greater in winter than summer. Oxygen content was shown to be related to the depth of the black layer in the comparison between different beaches in the Scilly Isles. Perkins (1957) has pointed out that the depth of this layer varies seasonally in the flats at Whitstable. This is an effect

10A

lo-/

Z 6 A

6 A

0~~~~~~~

2-

0

0

12 3 HOURS

FIG. 5. Changes in the oxygen concentration at station A, Whitstable, with the length of time the site had been exposed by the tide. Triangles-surface water, circles-interstitial

water at a depth of 2 cm, squares-interstitial water at a depth of 5 cm.

of temperature variation. The relationship between the black layer and temperature over a period of about 2 years at station A is shown in Fig. 6.

The other sites at Whitstable can now be briefly considered. Station B was situated in an area of sloping shingle near the top of the shore, which is densely populated by the polychaete Nerine cirratulus (Della Chiaje). No black layer occurs at any level, and no surface water persists during the period of tidal exposure. In fact the water table sinks considerably during this period. The temperature of the interstitial water varied between 17 and 180 C while samples were being collected. The oxygen content of samples collected from 5 cm below the surface of the water table are shown in Table 5. The station was re- covered by the sea immediately after the last samples were taken. It can be seen that the oxygen content declined steadily throughout the exposure period. Joyner (1960) found the salinity of the interstitial water of this area to be relatively constant at about 31 5%,. The oxygen content of air-saturated water at this salinity, and at 17 5? C, is about 5 7 ml/I and so the average oxygen content of the interstitial water (3 93 ml/l) was 69 % of the

H J.A.E.




air saturation level. This unusually high oxygen content is probably due to the coarseness of the beach (see Fig. 4a).

Station C was some distance lower down the shore than B, in an area of fine sand interspersed with occasional large stones. No black layer was present, but surface water persisted throughout the period of tidal exposure. Samples from a depth of 5 cm had

0 _

~2

0I 4

30 _

ui ~ ~ 'i

u 10 ,

AM J J ASO N DiJ F M A M J J A'S O N'Df|J MONTHS

FIG. 6. Variations in the depth at which the black layer commenced at station A, Whitstable, over a period of 22 months, together with the corresponding variations in temperature. The temperatures of the air, sea, surface water and sand at a depth of 5 cm were taken, the

range of these four being shown for each occasion.

oxygen concentrations of 068, 056 and 062 ml/I. At the time of sampling the temperature at a depth of 5 cm was 17.70 C, and the receding tide had just left the site.

Station D was situated in a low mound of sand near mean low water mark. From it the tip of the harbour jetty had a compass bearing of 66?, and a conspicuous windmill inland 154?. Below 1 cm the sand was blackened and contained many shell fragments. Although

Table 5. The oxygen content of interstitial water samples from station B, Whitstable

Hours Oxygen content Approximate depth exposed (ml/l) of the water table

by the tide (cm)

i 446, 451 0 4 4-18, 3-85 40 5 3 73, 3-62, 3-79 45 8 328 50

of relatively coarse grade the presence of firm London clay at a depth of 40 cm severely restricted drainage, and irregular pools of surface water persisted throughout the period of tidal exposure. Samples taken from 5 cm, after the site had been exposed by the tide for about half an hour, had oxygen concentrations of 0-45, 0-29, 023 and 0-29 ml/l. The temperature at a depth of 5 cm was 18.50 C at the time of sampling. Petricola pholadi- formis Lamarck and Saccoglossus sp. are common in this area.

The results of studies at Whitstable are summarized in Table 6. The oxygen concentra-



A. E. BRAFIELD 113

tion for station A is the average of the summer values only, for comparison with the other sites. Average temperatures at the four stations varied between 16 1 and 18.50 C. The third column shows the percentage of the sand sample passing the sieve with a mesh of 0-25 mm. From Table 6 it can be seen that, at least as far as these four sites are concerned, the interstitial water is very poorly oxygenated in flat, blackened, badly drained beaches with a high percentage of fine sand. In the sloping, well-drained beach of coarse grade, however, the interstitial water was relatively well oxygenated. These findings

Table 6. Summary of the study of the oxygen content of the interstitial water at four varied sites at Whitstable, Kent

Average oxygen Percentage Presence of Presence of Flat or Station concentration fine sand a black layer surface water sloping

(ml/l)

A 0-26 95 50 Present Persisted Flat D 0-31 50 75 Present Persisted Flat C 0-62 23-75 None Persisted Flat B 3-93 4-00 None None Sloping

correspond closely with those of the Scilly Isles survey. It has also been found that at a depth of 5 cm the sand flats represented by station A (inhabited by the polychaete Nephthys hombergi Lamarck) are very poorly oxygenated, that the oxygen content is consistently low throughout the period of tidal exposure, and that the oxygen concentration is less in summer than in winter.

DISCUSSION

The foregoing studies reveal that the oxygen content of marine beaches is generally extremely low. This seems to be chiefly an effect of poor drainage, a suggestion that has been supported by considerations of the persistence of surface water during the period of tidal exposure, and the incidence of the black layer. Well-drained beaches, such as sloping beaches of coarse grade, seem to be the only ones where oxygen is present in the interstitial water in appreciable quantities. It has also been shown that a very reliable indicator of oxygen level seems to be the amount of fine sand (sand grains smaller in diameter than 0-25 mm) present in a beach, as beaches containing more than about 10 % fine sand seem to be very poorly oxygenated, and only if there is less than 10% can the oxygen level rise above about 20% of the air saturation level.

This suggestion is supported by the studies at Whitstable (see Table 6), and results obtained during a short investigation in Jersey, which are summarized in Table 7. (Station A in Jersey was situated in a broad expanse of flat, firm sand shoreward of La Rocco Tower, near La Pulente. Rocky outcrops only partly sheltered the site from the full force of westerly breakers. After being exposed for 1 h the water table was 5 cm below the surface of the sand, and after 3 h 40 cm below. Consequently samples were collected from depths of 10 and 45 cm respectively. Station B was in St Aubin's Bay, in an area very similar in appearance to the flats at Whitstable. Nephthys hombergi, Arenicola marina, Scoloplos armiger, Cardium edule L., and Macoma balthica (L.) were common here. Station C was in the Royal Bay of Grouville, near Gorey, in a flat area of rather coarse sand with prominent ripple marks. Nephthys cirrosa Ehlers and Solen marginatus Pulteney occurred at this site. All samples at stations B and C were taken from 5 cm.




Cumulative curves obtained from grain size analyses are shown in Fig. 4(b). All three sites were at about mid-tide level.

The black discoloration which occurs in badly drained beaches deficient in oxygen is due to the presence of ferrous sulphide. The complex relationships controlling the black layer have been reviewed by Perkins (1957). The sharp upper limit of the black layer represents a position of equilibrium between the sulphide-producing reactions within the beach and the oxidizing effects of the well-oxygenated surface water and the sea. This explains why the black layer is more marked, and commences nearer the surface of the sand, in beaches which are poorly drained and in which the oxygen content is low. The highest oxygen content found in a discoloured beach in the Scilly Isles represented 11f5 % of the air saturation level (about 0-63 ml oxygen per litre). The highest oxygen content found elsewhere in black sands was 0-48 ml/l (Jersey, station B). On the other hand it seems that oxygen is rarely absent altogether from marine beaches, even in blackened sand.

Seasonal variations in temperature affect the depth of the black layer (see Fig. 6) both by their influence on the rate of the chemical reactions involved and by their effect on the

Table 7. Summarized results of the investigation in Jersey

Hours Temperature Oxygen Average 0 fine Black Surface Station exposed at depth content oxygen sand layer water

by the tide of 5 cm (ml/l) content (OC)

A 1 19-1 0-51, 0-51 0-52 75-5 Clean Present, some 3 17-6 0-56, 0.51 drained later

B X 17 4 0 40, 0-51 0 48 85 75 Black Present, 43 - 0-51, 0-51 below persisted

2-3 cm

C i 18-8 0 62, 0 56 0-42 28 0 Grey or Present, 2 - 029, 023 black persisted 3 21-0 0 40, 0 40 below

2-4 cm

abundance of bacteria (Perkins 1957). It was therefore not surprising to find that in summer at Whitstable, when the black layer was very near the surface of the flats, the oxygen concentration of the interstitial water was appreciably lower than in winter, when the black layer began at a greater depth.

The oxygen concentrations found in beaches in the present work are broadly similar to those found by other workers, reviewed at the outset. But it was pointed out then that these earlier investigations, excepting those of Jones (1955), were rather unreliable, either because faulty collecting devices were used or because inadequate methods were employed in determining the amount of dissolved oxygen. Jones (1955) obtained values for the oxygen content of the interstitial water at Robin Hood's Bay of the same order as those obtained in the present work for the sand flats at Whitstable (station A). He also found that the oxygen level did not rise or fall as the period of tidal exposure advanced. On the Whitstable flats and in Jersey a similar situation was encountered, the oxygen level remaining relatively constant throughout the period of tidal exposure. Probably the oxygen level falls during this period only in well-drained beaches of coarse grade such as that of station B at Whitstable.



A. E. BRAFIELD 115

ACKNOWLEDGMENTS

I am deeply indebted to Professor H. Munro Fox, F.R.S., for much advice and encourage- ment during this work. I would also like to thank Professor J. E. Smith, F.R.S., for kindly providing facilities at Whitstable and in Jersey. The work was carried out while in receipt of a grant from the Department of Scientific and Industrial Research.

SUMMARY

1. Methods are described whereby small samples of interstitial water may be collected from a beach without contacting the atmosphere at any stage and whereby the oxygen content of such samples may be accurately determined.

2. A comparative study of a variety of beaches shows that drainage is the most significant of the factors which affect the oxygen content of the interstitial water. The most reliable criterion of drainage in this context appears to be the percentage of a substrate sample composed of grains less than 0-25 mm in diameter.

3. Precise investigations of the oxygen content of beaches at Whitstable and in Jersey were made. In particular the oxygen content of the sand flats at Whitstable has been studied, with respect to changes in the oxygen concentration associated with depth in the beach, the length of time the area has been exposed by the tide, and the season.

REFERENCES

Adams, R. C., Barnett, R. E. & Keller, D. E. (1943). Field and laboratory determination of dissolved oxygen. Proc. Amer. Soc. Test. Mater. 43, 1240-57.

Aleem, A. A. (1949). Distribution and ecology of British littoral diatoms. Ph.D. thesis, University of London.

Alsterberg, G. (1925). Methoden zur Bestimmung von in Wasser gelosten elementaren Sauerstoff bei Gegenwart von salpetriger Saure. Biochem. Z. 159, 36-47.

Alsterberg, G. (1926). Der Winklersche Bestimmungsmethode fur in Wasser gelosten elementaren Sauer- stoff sowie ihre Anwendung bei Anwesenheit oxydierbarer Substanzen. Biochem. Z. 170, 30-75.

Angelier, E. (1953). Recherches 6cologiques et biogeographiques sur la faune des sables submerges. Arch. Zool. exp. gin. 90, 37-162.

Association of British Chemical Manufacturers and the Society for Analytical Chemistry (1957). Deter- mination of oxygen demand. Analyst, 82, 683-708.

Barnes, H. (1953). A double syringe-pipette for dissolved oxygen estimations. Analyst, 78, 501-3. Beadle, L. C. (1958). Measurement of dissolved oxygen in swamp waters. Further modification of the

Winkler method. J. Exp. Biol. 35, 556-66. Borden, M. A. (1931). A study of the respiration and of the function of haemoglobin in Planorbis corneus

and Arenicola marina. J. Mar. Biol. Ass. U.K. 17, 709-38. Bruce, J. R. (1928a). Physical factors on the sandy beach. Part I. Tidal, climatic and edaphic. J.

Mar. Biol. Ass. U.K. 15, 535-52. Bruce, J. R. (1928b). Physical factors on the sandy beach. Part II. Chemical changes. J. Mar. Biol.

Ass. U.K. 15, 553-65. Chapman, G. (1949). The thixotropy and dilatancy of a marine soil. J. Mar. Biol. Ass. U.K. 28, 123-40. Cole, A. E. (1932). Method for determining the dissolved oxygen content of the mud at the bottom of a

pond. Ecology, 13, 51-3. Deboutteville, C. D. (1960). Biologie des Eaux Souterraines Littorales et Continentales. Paris. Ellis, M. M., Westfall, B. A. & Ellis, M. D. (1948). Determination of water quality. Res. Rep. U.S.

Fish. Serv., No. 9. Fox, C. J. J. (1905). On the determination of the atmospheric gases dissolved in sea-water. Publ. Circ.

Cons. Explor. Mer, 21, 1-24. Fox, H. M. & Wingfield, C. A. (1937). The activity and metabolism of poikilothermal animals in different

latitudes. Part II. Proc. Zool. Soc. Lond. (A) (1937), 275-82. Fox, H. M. & Wingfield, C. A. (1938). A portable apparatus for the determination of oxygen dissolved

in a small volume of water. J. Exp. Biol. 15, 437-45.




Harper, E. L. (1953). Semimicrodetermination of dissolved oxygen. Analyt. Chem. 25, 187-8. Harvey, H. W. (1955). The Chemistry and Fertility of Sea Waters. Cambridge. Ishida, S. (1953). Oxygen content of water in contact with sand. J. Coll. Arts Sci., Chiba, 1, 95-100. Jones, J. D. (1955). Observations on the respiratory physiology and on the haemoglobin of the polychaete

genus Nephthys, with special reference to N. hombergii (Aud. et M.-Edw.). J. Exp. Biol. 32, 110-25. Joyner, A. (1960). Studies on Nerine cirratulus (Delle Chiaje). Ph.D. thesis, University of London. Kendall, M. G. (1955). Rank Correlation Methods. London. Morgans, J. F. C. (1956). Notes on the analysis of shallow-water soft substrata. J. Anim. Ecol. 25,

367-87. Newell, G. E. (1954). The marine fauna of Whitstable. Ann. Mag. Nat. Hist., ser. 12, 7, 321-50. Ohle, W. (1953). Die chemische und die elektrochemische Bestimmung des molekular gelosten Sauerstoffs

der Binnengewasser. Mitt. int. Ver. Limnol. 3, 1-44. Pearse, A. S., Humm, H. J. & Wharton, G. W. (1942). Ecology of sand beaches at Beaufort, N.C. Ecol.

Monogr. 12, 135-90. Pennak, R. W. (1940). Ecology of the microscopic metazoa inhabiting the sandy beaches of some Wis-

consin lakes. Ecol. Monogr. 10, 537-615. Pennak, R. W. (1942). Ecology of some copepods inhabiting intertidal beaches near Woods Hole, Massa-

chusetts. Ecology, 23, 446-56. Pennak, R. W. (1951). Comparative ecology of the interstitial fauna of fresh-water and marine beaches.

Annee biol. 27, 449-80. Perkins, E. J. (1957). The blackened sulphide-containing layer of marine soils, with special reference to

that found at Whitstable, Kent. Ann. Mag. Nat. Hist., ser. 12, 10, 25-35. Perkins, E. J. (1958). The microfauna of the shore, being a description of a qualitative and quantitative

survey carried out during a period of two years at Whitstable, Kent. Ph.D. thesis, University of London.

Reid, EH. M. (1932). Salinity interchange between salt water in sand and overflowing fresh water at low tide. J. Mar. Biol. Ass. U.K. 18,299-306.

Thamdrup, H. M. (1935). Beitrage zur Okologie der Wattenfauna. Medd. Komm. Havundersog., Kbh., Ser. Fisk. 10, 2, 1-125.

Webb, J. E. & Hill, M. B. (1958). The ecology of Lagos Lagoon. Phil. Trans. (B), 241, 307-419. Whitney, R. J. (1938). A syringe pipette method for the determination of oxygen in the field. J. Exp.

Biol. 15, 564-70. Winkler, L. W. (1888). Die Bestimmung des im Wasser gelosten Sauerstoffes. Ber. dtsch. chem. Ges.

21, 2843-54. Wiszniewski, J. (1934). Recherches ecologiques sur le psammon et specialement sur les rotifbres psam-

miques. Arch. Hydrob. Rybact. 8, 162-272.



the oxygen content of interstitial water in sandy shores

Documents