The shingle foreshore lagoon system of Shingle Street

THE SHINGLE-FORESHORE/LAGOON SYSTEM OF SHINGLE STREET, SUFFOLK: A PRELIMINARY SURVEY R . S. K . BARNES a n d S. E .

HEATH

Introduction Of the 900 km of shingle coast surrounding England and Wales, only a few areas are sufficiently extensive to support characteristic communities of ammals and plants and to make detailed study profitable. Orfordness and the Shingle Street region immediately south of the end of the spit together form one such area, but Shingle Street, being rather inaccessible and remote, has not received the attention which it deserves, except from a small number of geographers and botanists. Unfortunately, such studies as have been carried out have approached the habitat piecemeal and their results are widelv scattered in the literature.

The purpose of this short exploratory study was in part to compile and compare existmg reports on the geomorphological history and ecology of the region and in part to update existing published information, particularly in respect of the series of coastal lagoons situated between the mouth of the Ore and Bawdsey. Detailed information on the area is in the possession of S . E . H . : only an outline will be published here. Field work was carried out in the summer of 1979 and hence most results are restricted to spot checks on current status. Hopefully, the results will initiate and stimulate further, more detailed studies of the ecology of this fascinating region which is included in a Grade 1 Site of Special Scientific Interest (see Ratcliffe, 1977).

Shingle Street itself forms part of the parish of Bawdsey and lies roughly half way between Aldeburgh and Felixstowe (Fig. 1). Originally it was an ideal spot for smuggling activity, the only access to 'civilization' being 3 km to the south, across the barren shingle to East Lane. DĂźring World War II, a road connection was built from Hollesley which has contributed to the exploration, inhabitation, but also deterioration of the area from a naturalist's point of view.

Shingle Street stands on a soft substratum, mainly alluvium, red crag and London clay, overlain by shingle (Boswell, 1928). The shingle, formed mainly of flint but also with the occasional quartz, quartzite, ironstone, chert, gnt and sandstone (Boswell, 1928), falls within the cobble and pebble sizerange on the Wentworth Scale (4â&#x20AC;&#x201D;75mm diameter; - 2 to more than - 6 </>*).

It has been derived (a) from offshore supplies at times during which sea level was lower than at present, and (b) more recently, from glacial material on the East Anglian sea bed and material eroded from cliffs to the north.

Most of the major forms in which coastal shingle occurs have been recorded from the Shingle Street region (Oliver 1912; Randall, 1977a, b, c). *It is customary, when describing particle sizes of sediments, to use the 4> scale, where <t> = - I o g 2 d, d being the particle diameter in mm. For a 2 mm particle, <t> = - 1 , for example, and for a 0.5 mm particle <f> = 1.

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The intertidal zone is formed by a classic fringing shingle beach. To the north, an elongate spit—Orfordness—has developed in part as a series of apposition beaches, where shingle has piled up in front of the spit and then has been driven landwards by storm waves. Uninterrupted longshore drift has caused a lengthening of Orfordness southwards (Barnes, 1977; Randall, 1977c). Cobb (1958) has described a cyclic process in this development, shingle moving both with and against the overall southward movement of beach material and forming bars some of which enclose lagoons. Finally, the orientation of some of the shingle ridges at Shingle Street suggests that they have developed offshore as bars and have been moved onshore (Carr, 1972). The ways in which the influences of winds, magnitude of fetch (Randall, 1973), local currents, and tidal currents and waves (Kidson et al., 1958; Kidson &'Carr, 1959) interact to produce the complex movement of shingle in this region of the Suffolk coast have been studied to varying extents. The movement of masses of shingle onshore and the effects of waves acting at different tidal heights produce characteristic banks of shingle, with finer particles in the fulls and coarser ones in the swales.

Typically, shingle is mainly deposited or removed during storms the last two major ones to affect Shingle Street being in 1893 and 1953. More minor movements of shingle nevertheless occur continually, and even small storms may sweep away years of successful Vegetation growth or deposit new shingle masses. Hence lt is necessary to monitor shingle formations at frequent intervals to assess the effects of these physiographic changes on a system Only for the last 40 years is detailed information on changes in the Shingle Street coastline available.

Exposure to coastal winds and salt, and the inability of shingle to retain water and lts dissolved salts makes a shingle substrate inhospitable to plants Various studies have described the botany of shingle systems, including that of Shingle Street (see Randall, 19776, c and references cited therein). In summary, they indicate that the succession of plant colonization is controlled by the length of time for which the shingle has been left undisturbed by storm waves, etc. and by the extent to which the interstices between the pebbles have accumulated fine material (both inorganic and organic, e.g. atmosphenc dust and humus). The sequence of plant cover which can be correlated with these factors and the ways in which plant species have adapted to the various conditions appear closely similar in the different areas studied, although each system does display individual features.

Often it is the accumulation of drift material which enriches the barren shingle sufficiently to permit initial plant colonization. At Shingle Street, sea beet, Beta maritima, is the pioneer colonist of the storm shelf, and by increasing the surface stability it allows the sea pea, Lathyrus japonicus, another pioneer species, to invade. These two species build up a reservoir of organic material which in turn provides a medium in which the runners of grasses can spread vegetatively. The most common plant at Shingle Street, the oat-grass, Arrhenatherum elatius, is typical of this stage. Stability and fine-fraction content are thereby increased still further, permitting curled dock, Rumex crispus, annual meadow-grass, Poa annua, sea-campion, Silene maritima, short-lived composites and—eventually—biting stonecrop, Sedum Trans. Suffolk Nat. Soc. 18 part 2.

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acre, red fescue, Festuca rubra, stinking groundsel, Senecio viscosus and various mosses to colonize. These stages probably reflect habitats that have been undisturbed for 20-70 years and are those most characteristic of Shingle Street.

Finally, these species give way to various waste-ground plants (such as nettles, Urtica dioica and spear thistle, Cirsium vulgare) and sea pink, Armeria maritima, and ultimately to a climax heath Vegetation of low shrubs, but the Shingle Street succession appears to be interrupted before this climax stage. Several species characterizing the climax Vegetation were present 10-15 years ago (Bingley, 1979, personal communication) and their absence today probably reflects human pressure on the habitat more than it does any 'natural' cause.

Damp areas around the lagoons, of course, support a different flora, dominated by salt-marsh plants where fluxes of sea water and tidally-related fluctuations in water level occur, and by semi-aquatic reed-, sedge-, and rush-like species in the more isolated lagoons.

Geomorphological history of Shingle Street The following is a summary compilation of the more important dates in the history of the shingle features at Shingle Street based on a variety of published sources.

B.C. Drillings at Havergate Island have produced shingle material with an estimated in situ age of 8,000 years; an exposed peat bed in the River Ore, containing shingle, was datable at 5,390 Âą 110 years; and peat samples from the Aldeburgh marshes contained shingle 3,460 Âą 100 years old (Carr, 1970, 1972; Carr & Baker, 1968). Clearly, then, shingle has been a feature of this Stretch of coast for many millenia.

1-1890 A.D. Green (1961) presents information on the growth of Orfordness since the Ist Century B.C.; by the 12th or 13th Century A.D. the spit had reached as far south as the River Butley. The first historical reference to shingle dates from 1165, during the construction of Orford Castle (Boswell, 1928). Several early maps of this coastline (back to 1530) survive and have been discussed by Kidson (1963), Anon (1966), Carr (1969) and Randall (1973) in relation to the southerly growth of the spit (see also Carr, 1972).

1890 to the present 1893 Violent storms deposit large quantities of shingle on beach, spit is reduced in length by up to 2 km.

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1904 Ordnance Survey records shingle for the first time, Lagoons 0, 2 and 3 are embryonic, Lagoon 5 is complete.

1924 Shingle continues to accumulate on foreshore, Lagoons 6 and 7 are embryonic, Lagoons 0, 2 and 3 are complete.

1940 Lagoon 6 is complete, Shingle Street is evacuated and the area used for military purposes (R.A.F. practices, anti-mine device testing, etc.), Lagoons 0, 5 and 6 possibly deepened by excavation.

1942 Detailed aerial photographs available from now onwards.

1945 Reinhabitation of Shingle Street.

1945-48 Rapid landward movement of shingle, infilling of Lagoons 2 and 3 begins.

1948-51 Formation of a lagoon on the spit, indicating a northerly movement of shingle into the mouth of the estuary.

1952 More infilling of the larger lagoons by landward movement of shingle.

1953 Storm surge greatly modifies coastline, Lagoon 3 nearly disappeared, after this date shingle deposition slows and less material is moved.

1954, 1957 Temporary 'noses' on the Shingle Street side of spit arc.

1955, 1957 Strong NE and E winds cause erosion seawards.

1956 Lagoon 3 only an ephemeral feature.

1961 Lagoon 7 isolated from sea.

1961-70 Ridge develops—maximum length 175 m—north of Lagoon 7.

1970 Shingle ridge—now only 80 m—encroaches on Lagoon 7, Lagoon 7 some 90 m from sea, Lagoon 2 disappears.

1973 Ridge north of Lagoon 7 partially encloses an embryonic Lagoon 8, no movement of shingle on to beach from offshore.

1978 Lagoon 7 with connection to sea, Anglian Water Authority seals the opening.

1979 Lagoon 7 open to the sea again, 'Lagoon 8' a salt-marsh fringed arm of the sea.

Maps illustrating many of these changes are given by Cobb (1958), Kidson (1963), Carr (1969, 1972) and Randall (1973, 19776), whilst changes in the hydrography are documented by Carr (1972) and Kidson et al. (1958). An oblique aerial photograph of Lagoons 6 and 7 and 'Lagoon 8' is given on page l l o f Barnes (1979).

The Shingle Street Lagoons Introduction Lagoons and their enclosing barriers form 13 per cent of the world's coastline, although they are rare in Britain and in Europe generally (Barnes, 1980).

Only around Europe's relatively tideless seas (e.g. the Mediterranean, Baltic, Black and Caspian) are lagoons a characteristic coastal feature. Basically, this results from the fact that high tidal ranges create a high-energy environment in which the low-lying barriers necessary for the isolation of bodies of salt or brackish water from the adjacent sea do not persist for long. Throughout the world as a whole, sand is the most usual barrier-forming material; but in Trans. Suffolk Nat. Soc.

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Britain, correlated with the high-energy regime, such few lagoons as do occur are most often enclosed within shingle ridges. Notable British examples of this type of habitat are associated with the shingle ridges of south-western England (The Fleet, Dorset; Slapton Ley (now freshwater), Devon; Swanpool, Cornwall; etc.) and Suffolk (Shingle Street). Only the Swanpool lagoon near Falmouth, Cornwall, has been studied in any detail (Barnes et al., 1971; Dorey et al., 1973; Little et al., 1973; Barnes et al., 1979; Crawford et al., 1979).

Typically, lagoons retain a connection with the .adjacent sea through a narrow entrance/outlet Channel (Barnes, 1980); but movement of sand or shingle may block this Channel with the result that the lagoon may evolve into a coastal freshwater lake, as for.example has happened at Slapton in Devon.

Complete enclosure does not necessarily mean that a lagoon ceases to be influenced by the sea however. Small lagoons situated within permeable shingle barriers, for example those at Porlock in Somerset, may receive an influx of sea water by percolation through the shingle at high tide, and then lose water back to the sea again at low tide; i.e. although spatially isolated, they are not hydrographically separate. The lagoons at Shingle Street fall partly into this category.

Besides their inherent interest as 'natural aquaria', the Shingle Street lagoons are interesting, therefore, on a number of scientific counts: they are examples of a habitat generally rare in Britain; they are examples of lagoons enclosed by shingle, a system rare on a world scale; and they are systems without a direct connection to the adjacent sea, again a Situation relatively little studied on a world scale. Being small (the largest lagoon semi-enclosed with the landâ&#x20AC;&#x201D;the Lagoa dos Patos, Brazilâ&#x20AC;&#x201D;is 265 km long), they are also ephemeral, and from what has been said above (p. 172) it is obvious that the different lagoons have been subject to varying alteration over the last fifty years. The effects of these physiographic changes are also of considerable scientific interest.

The numbering system used to identify the various Shingle Street lagoons (Fig. 1) dates from Cobb (1958) who adapted the unpublished system evolved

by F. J. Bingley. Several minor changes have occurred since 1958, however, particularly in relation to Lagoons 5 and 6. Lagoon 5 is now only represented by three remnants, which can be termed A, B and C; whilst Lagoons 6a and 6 b have merged to form one water mass, separable into two main basins 6S(outh) and 6N(orth). Lagoons 2 and 3 are no longer extant. Information is provided below on the current status of the remaining lagoons in respect of (a) seepage, by percolation, into the lagoons, (b) depth, salinity and temperature fluctuations of their waters, (c) the particle-size spectrum and organic content of their sediments, and (d) the nature of their macrofauna. These data were obtained from only a few samples taken in the summer of 1979 and cannot, therefore, be taken as constituting anything other than a 'spot check'.

Methods Very simple seepage tests were made as the main aim was to prove or disprove significant exchange. Readings were taken from a stick, placed and left in the Trans. Suffolk Nat. Soc. 18 part 2.

174 Suffolk Natural History, Vol. 18, Part 2 substratum throughout the test. A lagoon's water level was marked as zero the beginning of the period of Observation and then used as a reference poin Salinity was measured by means of both an Endeco Refractometer/ Salinometer and an Electronic Switchgear Ltd Salinity/Temperature Bridge.

The particle-size fractions of thefinersediments were assessed by the method based on Stoke's Law relating the settling velocity of a particle i water to its size (Briggs, 1977). A 20 g sample of dried Sediment was su pended in a column of 1,000 ml distilled water, to which had been added drops of detergent, and then leftto settle. At time intervals of 29 sec., 1 m 56 sec., 7 mins. 44 sec., 31 min., 2 hr 3 min., 8 hr 10 min., and 32 h samples were withdrawn from a depth 10 cm below the water surface, we dried and then weighed. By appropriate arithmetic manipulation, the quantity of various size-fractions in the original sample was obtained (see Briggs, 1977).

Organic content of the Sediment was determined by incinerating a weighed and dried sample for 12 hr at 700°C in a muffle furnace. Decomposition carbonates was corrected byfloodingwith ammonium carbonate Solution as described by Barnes (1974). Organic content is expressed below both as percentage of the total sample and as a percentage of thefinefraction.

Information on the macrofauna was obtained by inserting a bottom-less Sandwich box (cross-sectional area 300 cm2, depth 6 cm) into the sediment, sliding a metal plate under the box, and then sieving the Contents through 0 and 1.0 mm mesh sieves. In addition, sweeps through the water with a were made.

Results Seepage Fig. 2 shows that sea water does percolate into Lagoons 1, 4, 6S and 7 du high tide in the adjacent sea. If Lagoon 0 is subject to seepage from the s then the quantity of water which exchanges must be small. It is evident from the presence of a drift line around the lagoon that the water level does var but personal communications from local residents indicate that this is ä seasonal Variation related to the evaporation/precipitation -elationship.

Lagoon 1 reaches its maximum volume some 2Vi hr after high tide, up which time seepage can be observed along the north-easterly shore. Similarly, water can be observed entering Lagoon 4 along the entire eastern shor fluctuations in water level lagging some 2.75 hr behind those in the se During storms the sea can also be observed splashing directly into this lagoo over the separating shingleridge.Both Lagoons 1 and 4 have very clear wate which may in part be a result of regulär flushing.

The results from Lagoons 6S and 6N are more problematic. Water is continuous through both parts of the system, yet seepage tests indicate a degree of autonomy (assuming no interference with the measuring sticks).

Lagoon 6N shows some seepage, very much delayed, whilst 6S varies in wate level quite considerably, with a delay of some 3 hr. Indirect seepage from Lagoon 7 is possible. Lagoon 7 is currently open to the sea and consequen Trans. Suffolk Nat. Soc. 18 part 2.

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exchanges large quantities of tidal water. Nevertheless, seepage exchanges still occur. At low tide in the adjacent sea, water can be seen pouring out of the lagoon over alluvial deposits underlying the shingle (see also Fig. 2).

Lagoons 5A and 5/1 show no significant increase or decrease in water level corresponding to external tidal fluctuations.

Water depth, temperature and salinity All the lagoons are shallow, the deepest being Lagoon 4 at some 1.5 m depth and accordingly temperature Variation is quite marked. During a day during which the air temperature rose from 15°C to 21.5°C, the increase in water temperature of the lagoons varied between 1.5°C and 5°C over the same period Those which maintained their temperatures most constant were as might be expected, those with large exchanges and greater depths Boyden & Russell (1972) provide a record of salinity Variation in the Shingle Street Lagoons during 1966/67. They document a wide ränge particularly for Lagoons 0 and 1, but several of the readings taken in 1979 lie well outside the ranges which they quote (Table 1). Lagoons 0 and 1 possessed much higher sahnities in the summer of 1979 than at any time in 1966/67.

Table 1 Salinity of the water in the various lagoons (parts per thousand of dissolved salts)

Lagoon

21/22.viii.79

22.ix.79

0 1 4 5A 5B

33 27 26 12 11 24 24 /

40 32.5 32 23 16 32 \ 31 ) 34.5

6S

6N 7

Range in Boyden & Russell, 1972 3.8- 8.5 13.8-19.4 28.5-33.2 / / 20.4-31.6 29.7-35.0

Another stnking feature of the 1979 results is the marked increase in salinity between the two sets of readings. Evaporation can only have contributed to a very small extent to this increase and the cause must be largely conjectural. The only possibility which occurs to the authors is that salt deposited in the shingle by sea spray was washed out and into the lagoons by raintall. It is certamly not unreasonable to assume that salt may at times accumulate in shingle as a result of the evaporation of spray and splashes nor that summer ram may then leach the salt into the lagoonal basins It is questionable, however, whether such a process could provide the large « a n t l t , n L ° f S 3 l t r e q U l r e d t o r a i s e t h e s a I i n i t y o f - f orexample, Lagoon0from 33 to 4 0 % 0 ( = parts per thousand of dissolved salts), even though the water level at the time was low. The phenomenon is the more mystifying in that the maximum salinity recorded for Lagoon 0 by Boyden & Russell was Trans. Suffolk Nat. Soc.

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8.5째7cc ! It should be pointed out that the same salinity values were obtained f r o m both salinometers. Additional evidence that our high values of salinity recorded are not necessarily aberrant is available from the unpublished series of spot measurements made by Cambridge University undergraduates over the period 1956-67. These records indicate a maximum salinity in the Order of 35-38%c for Lagoons 0, 1 and 6; a r채nge of 6 62%o for Lagoon 5; and a r채nge of 31-35%c for the now vanished Lagoon 2. Clearly f u r t h e r study of salinity fluctuations in the lagoons is required.

Particle-size and organic content ofthe

sediments

Characteristically, lagoons are floored by fine floccules of soft water-laden sediment, but one might expect that lagoons enclosed within shingle formations would have substrata dominated by coarser materials. Clearly this is the case at Shingle Street (Table 2). Indeed, with the exception of Lagoon 7, it is not immediately obvious from where those fine particles which are present have come. Lagoon 7 receives a tidal influx of silt-laden sea water and during periods of slack water this may settle out: accordingly, it shows the largest non-shingle sediment fraction of these lagoons. The others average only 2.3 per cent (by weight) silts and clays, and the well flushed Lagoon 4 is floored almost entirely by gravel and pebbles. Of the isolated lagoons, the relatively undisturbed Lagoons 0 (except around the edge) and 5 contain most silt; and the suggestion above that Lagoon 6S receives considerable seepage whilst 6N does not is borne out by the Observation that 6N has more than five times more silt in its sediments than does 6S. It is possible, however, that 6S but not 6N has been artificially excavated to provide material for the construction of sea-walls or other defense systems.

Table 2 Particle-size distribution of the lagoonal sediments (in %)

Lagoon

>0 cf>

0-4 0

4-5 <t> 5-6 <f> 6-7 0

7-8 0

8-9 0

<9 0

O(EAST) 0 (NORTH) 1 4 5A 5B 6S 6N 7

89 79 90 98 78 87 90 90 75

11 15 8 1 19 9 10 8 19

0 1.7 0.4 0.2 0.4 1.3 0.2 0.6 1.0

0 0.2 0.5 0.05 0 0 0 0.2 0

0 0.4 0.4 0.05 0 0 0 0.2 0.5

0 0.8 0.1 0.7 0.9 0.3 0 0.4 1.0

0 2.5 1.0 0.3 1.8 2.1 0.2 0.8 2.9

0 0.2 0 0.1 0 0 0 0 0

The organic matter associated with lagoonal sediments derives from several sources: living benthic algae; detritus formed from the breakdown of aquatic and semi-aquatic macrophytes; dead organisms; and a r채nge of living micro-organisms. The organic content of the lagoonal sediments is displayed Trans. Suffolk Nat. Soc.

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in Table 3 There is a significant correlation between total organic content coeffitienTo 8*V p t n n n

^

T ™

,ag

°°nS

( S p e a r m a n

rank

— i a S

coefficient 0.85; P < 0 . 0 1 ) , and this suggests that most of the organic matter is ~ e d ^ . s size fraction. Moreover, calculations from the data in 2 a n d 3 s h o w t h a t with the exception of Lagoon 4 all the organic 1S P ? V 1 , d e d ' ? a S S ° a a t , o n W l t h Particles of less than 1 mm dia^ r meter. T h e most plausible Interpretation of this is that in the well flushed pCJ T " 0 ° f t h e ° r 8 a n i c m a t t e r is diatoms I S W the form of diatoms, etc. on the surface of the shingle, whilst in the other lagoons the E C TU?r uh f r ° V i d e S t h e baS1C f o o d s o u r c e o f macrofauna is almost entirely in the form of what can loosely be termed detritus (plus, of course any ed.ble matenal from or associated with the larger living plan s) L r f h T l e V O P U d a q U a t ' C " ° r a ° f L a 8 ° ° n ° ( N ) i s Presumably refponsib e lor the higher organic status of this lagoon's sediments.

Table 3 Organic content of the lagoonal sediments (in < Lagoon 0 (EAST) 0 (NORTH) 1 4 5A 5B

6S 6N 7

Total % organic matter 0.3 3 1 1.5 0.6 2.6 0.6

0.2 1.2 2.8

Organic content f fine fraction ( < 1 mm)

0

2 15 15 23

12 5 2

11

11

Macrofauna Although atypical in their surroundmg and flooring material, the Shingle s u PPort a characterS Ä ' i h C Part'al,eXCeptl0n of Lag°on lstically north-west European lagoonal fauna, dominated by the detritus-

f 7 n t ? J T T r ] ] U ? H y d r ° h l a V e n t r o s a a n d t h e i s ° P ° d crustacean Idotea chehpes = /. vindts), and by the suspension-feeding lagoon cockle Cemstoderma glaucum. Lagoon 4 with its near sea-water salinity and regulär exchange o f tidal water through seepage possesses a fauna with many elements otherw.se occurnng in pools on rocky shores and absent from the other lagoons; e.g. the amphipod crustacean Dexamine spinosa, the chiton Lepidochitona cinerea and the brittle-star Amphipholts squamata Unpublished faunal records accumulated by Cambridge Universitv undergraduates over the period 1956-67 indicate that each lagoon supported a highly individual fauna with several species restricted to one particular lagoon, but this cursory survey was not a b l e - n o r indeed was it d e s i g n e d - t o connrm the presence o f these 'specialities'. The data presented in Table 4 can only be taken as a guide to the more common and abundant species Trans. Suffolk

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Table 4 Macrofauna recorded from the Shingle Street lagoons. Numbers indicate approximate abundance per m2 and ticks indicate presence.

O(E) O(N) 1 Nematodes Enoplus brevis jx Annelids oligochaetes jy» Nereis diversicolor 30 Arenicola marina v* MoIIuscs Lepidochitona cinerea Hydrobia ventrosa 2,700 13,800 few Littorina saxatilis Cerastoderma glaucum 500 300 Abra tenuis 200 Crustaceans copepods Gammarus duebeni Dexamine spinosa Idotea chelipes 30 5,600 v* Praunus flexuosus Palaemonetes varians Insects chironomid larvae f mosquito larvae Ephydra sp.

Sigara stagnalis/selecta Ochthebius marinus Echinoderms Amphipholis squamata Fish Gasterosteus aculeatus

4

5A

5B

6N

v

6S

v» 1,000

150 200

30

700 7,900

450 abund. abund. i^»

abund.

30

700

tS i^» t-» is0

j*» ^ ^

^ ^

1 400

Other records: Larvae of Eristalis aeneus (Insecta: Diptera) were obtained from the westem margin of Lagoon 0.

The differential abundance of Hydrobia, Idotea, etc. largely conforms to that which one might predict on the basis of the detrital content of the Sediments, although Lagoon 6 is here anomalous. The data, however, are insufficient to permit speculation on this point. In spite of the preliminary nature of these data, it is nevertheless apparent that the Shingle Street lagoons d o show faunal differences, do possess environments with differing degrees of fluctuation in water level, salinity, etc., and do show a number of typical and unusual lagoonal features. Further study of these systems would not only be interesting in its own right, but may well contribute to an understanding of lagoonal biology in general.

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Acknowledgements We are most grateful to Drs. M. J. Bishop, W. A. Foster and R. M. Warwick for identifying various animal material, to Mr. J. J. Clark for assistance in the laboratory, to Mrs. H. P. Barnes for transporting equipment to the field, and to E n c Walker and Lydia Vulliamy for providing shelter during the 'field work.

References Anon. (1966). Orford Ness: A selection of Maps mainly by John Norden presented to James Alfred Steers. Cambridge, Heffer.

Barnes, R. S. K. (1974). Estuarine Biology. London, Arnold.

Barnes, R. S. K. (1977). Introduction: The coastline. In: Barnes R S K (Ed.), The Coastline, pp. 3-27. London, Wiley.

Barnes, Richard (1979). The Natural History ofBritain and Northern Europe: Coasts and Estuaries. London, Hodder & Stoughton.

Barnes, R. S. K. (1980). Coastal Lagoons. Cambridge, Cambridge University Press.

Barnes, R. S. K., Dorey, A. E. & Little, C. (1971). An ecological study of a pool subject to varying salinity (Swanpool, Falmouth). An introductory account of the topography, fauna and flora. J. anim. Ecol 40 709 Barnes, R. S. K., Williams, A. J., Little, C. & Dorey, A. E.'(1979) An ecological study of the Swanpool, Falmouth IV. Population fluctuations of some dominant macrofauna. In: Jefferies, R. L. & Davy, A. J. (Ed.), Ecological Processes in Coastal Environments, pp. 177-97 Oxford Blackwell.

Boswell, P. G. H. (1928). The Geology ofthe Country around Woodbridge Felixstowe and Orford. London, H.M.S.O./Memoirs of the Geological Survey of England and Wales, Explanation of Sheets 208 and 225 Boyden, C. R. & Russell, P. J. C. (1972). The distribution and habitat ränge of the brackish water cockle (Cardium (Cerastoderma) glaucum) in the British Isles. J. anim. Ecol. 41, 719.

Briggs, D. (1977). Sediments. London, Butterworths.

Carr, A. P. (1969). The growth of Orford spit: cartographic and historical evidence from the sixteenth Century. Geogr. J. 135, 28.

Carr, A. P. (1970). The evolution of Orford Ness, Suffolk before 1600 A D • geornorphological evidence. Zeit, für Geomorph. (N.S.), 14, 289.

Carr, A. P. (1972). Aspects of spit development and decay: the estuarv ofthe River Ore, Suffolk. Fld Stud. 3, 633.

Carr, A. P. & Baker, R. E. (1968). Orford, Suffolk: evidence for the evolution of the area during the Quaternary. Trans. Inst. Br. Geogr. 45, Cobb, R. T. (1958). Shingle Street, Suffolk: a brief geographical introduction. Rep. Fld Stud. Coun. 3 (1956/57), 31.

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R. S. K. Barnes Department of Zoology and St. Catharine's College, Cambridge, CB2 IRL. S. E. Heath 35 Milvain Avenue, Newcastle-upon-Tyne 4.

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