405

R app. P.-v. Réun. Cons. int. Explor. M er, 172: 405-417. 1978.

T H E B E N T H O S O F T H E W E S T E R N N O R T H SEA

A. D. M cI n t y r e

M arine Laboratory, P.O .Aberdeen AB9

IN T R O D U C T IO N

The object of this review is to consider the knowledge available on the benthos of the western North Sea, in particular with respect to any changes which may have taken place in recent years, and to examine this in relation to fisheries.

The area covered is the east coast of the United Kingdom from the continental edge north of Shetland to the eastern boundary of the English Channel, and extending out roughly to the centre of the North Sea. Some material on the German Bight is included thanks to assistance and information contributed by Dr. E. Rachor. When data from the North Sea are sparse, relevant illustrative material from other regions is introduced.

This review excludes the organisms of rocky areas and concentrates on those living on the level sea bottom, i.e. on and in sediments ranging from gravel through sand to mud. Even in this somewhat restric­tive sense the [benthos consists of a vast assemblage of organisms from viruses and bacteria to the largest molluscs and crustaceans, and it is helpful to divide this assemblage into groups for detailed consideration. Using a number of criteria such as the sampling methods and the processing techniques, we can arrive at the loose division shown in Table 167. I t may be useful to consider separately on the one hand macro­fauna which are normally sampled with grabs and large corers and retained on sieves of 1/2- 1 mm mesh, and on the other hand those benthic organisms which because of their large size or active movement are best sampled by towed gear, and for which sieves are not usually needed: shrimps, prawns, crabs, and the large molluscs and echinoderms. Also included in the benthos are the meiofauna, which are for the most part metazoan organisms passing through the screens normally used for macrofauna, and finally, most nu­merous of all, the benthic micro-organisms - a con­glomerate of Protozoa, bacteria, viruses, etc., which require special techniques for sampling and study. While these categories are clearly not mutually ex-

Box 101, V ictoria Road,8DB, Scotland

elusive or rigidly separable, they do represent a useful division of the benthos if only in operational terms of sampling and study techniques, and in reviewing knowledge of the benthos in the areas in question we may begin by looking more closely at each of these in turn.

MICROBENTHOS

There are very few studies of microbenthos in the area under consideration. In shallow water, benthic microalgae may contribute a significant part of the primary production, as for example on the tidal flats of the Waddensea where microflora annual production of more than 100gC/m2 has been measured (Gadée and Hegeman, 1974). Also, some Protozoa such as Ciliata may be numerous as scavengers and predators (Fenchel, 1968). Bacteria, which are well known to be critical in the recycling of nutrients, have been studied in the German Bight where the maximum wet weight biomass in the upper 2 mm of sediment was calculated as 48 mg/m2. (Hickel and Gunkel, 1968). The microbenthos form an essential link in the food chain. They are ingested and to some extent utilized by those larger organisms which take in sediment and detritus while some microbenthic in­dividuals such as algae and larger Protozoa are selec­tively preyed upon. However, the microbenthos can hardly be said to constitute an important direct food for fish in general.

MEIOBENTHOS

This category comprises the smaller metazoans, al­though some of the larger Protozoa such as certain Foraminifera and Ciliata are often included. Table 168 lists the relevant taxa and many of these occur in very small numbers. Figure 314 illustrates the numbers of various groups typically found in different habitats per unit area, and it is clear that nematodes and copepods are overwhelmingly the dominant animals, with Turbellaria and Gastrotricha usually at least

406 A. D. McIntyre

Table 167. One possible way of classifying benthos by size

Category Size Biologicalfeatures

Samplingtechniques

Taxonom icposition

M icrobenthos......................... Pass High rates of Plating and Bacteria, virusesfinest respiration culturing. yeasts, fungisieves and

reproductionCores o f less

than 2 cm diam eter

actinomycetes blue-greens M ost protozoa Some algae

M eiobenthos........................... M edium Cores of Large protozoa0-5-1-0

mm sieves

respiration rates. Two or more

generations per year

2-10 cm diam eter

Small m etazoa

M acrobenthos........................ Retained Low respiration rates. Grabs sampling M edium-sizedon

0-5-1-0 m m sieves

Two or less generations

per year. M ostly infauna

at least about 1/10 m 2

m etazoa

M egabenthos......................... H andpickedfrom

samples

As above, mostly epifauna

Towed gear, trawls, dredge

Large m etazoa

well represented. In some localities generally in iso­lated samples or small areas, other groups such as Tardigrada and Archiannelida may be abundant. The precise role of meiofauna in the marine ecosystem is at present the subject of intensive investigation and discussion by specialists. Meiobenthic organisms are present often in densities of millions of individuals per m 2 (Table 169), but may be only a few tenths of a gram dry weight. The turnover per unit weight may be an order of magnitude higher than that of some macrobenthos, so that in energetic terms the

Table 168. Marine meiofauna taxa

T axa which are all or m ainly meiofauna

T axa which have m any meiofauna representatives

O rder Foraminifera Class TurbellariaSub-class Ciliata Class PolychaetaPhylum Kinorhyncha Class OligochaetaSub-class M ystacocaridaPhylum Gnathostomulida T axa which have aPhylum T ard igrada few specialised species inPhylum Rotifera the meiofaunaClassPhylumClassClassClassClass

AcaridaGastrotrichaArchiannelidaCopepodaN em atodaOstracoda

PhylumPhylumPhylumClassClassClassPhylumClassPhylumClass

CoelenterataNem ertiniPriapuloideaSolenogastresGastropodaScaphopodaBrachiopodaH olothuroideaBryozoaAscidiacea

meiofauna may be more im portant than its dry weight would suggest. In the context of the food web however, although young fish feed for a short time on benthic copepods and Crangon take in and apparently digest nematodes, it has yet to be demonstrated that the direct importance of meiofauna as fish food is anything but minimal.

MACROBENTHOS

This category includes the bulk by weight of the standing stock of infauna. I t consists in the North Sea mainly of polychaetes, bivalve molluscs, echinoderms, and small crustaceans. These organisms clearly made up an important part of the food of the main demersal fish.

MEGABENTHOS

This heading is used here (for want of a better term) to refer to the larger benthic animals which are not adequately sampled by grabs. I t includes a varied group, ranging from the large burrowing ane­mones which are too sparsely distributed and too deeply embedded to be taken by light macrofauna gear, to the active epifauna such as shrimps, prawns, hermit crabs, and large starfish which avoid the grabs. These organisms are extremely difficult to sample quantitatively even by towed gear, yet some of them also form a critical part of the food of demersal fish.

The benthos of the western North Sea 407

In tertida l Sand (Scotland)

0 200 £00 600

NEMATODAC0PEP0DA

NAUPLIITURBELLARIA

GASTR0TRICHATARDIGRADA

ARCHIANNELIDAC0ELEN7ERATA

P0LYCHAETA

Mud (In d ia )

1200 600

Intertidal

2£00 1800

NEMATODA COPEPODA

NAUPULII KINORHYNCHA

OSTRACODA OTHERS

Subtidal Mud (N.Sea)at 100m depth

300 600 900 1200 1500

rNEMATODACOPEPODANAUPLIITURBELLARIAPOLYCHAETAKINORHYNCHAOSTRACODA

1800 i

Numbers of Meiofauna groups /1 0 cm 2Quantitive comparison of meiofauna from various habitats

Figure 314.

by less than 5°C; and finally his infralittoral étage, with temperature variations of more than 10°C, is limited at most points along the U.K. coast and out into the southern North Sea by about 40 m isobath. Without fully committing ourselves to this system, we may conveniently use it in the present context to discuss the data available on the western North Sea. These data are sparse, and differences of ap­proach by various workers make it difficult to present a coherent picture, but an attempt is made below a t least to indicate the general structure of the com­munities.

THE INFRALITTORAL ÉTAGE

This region has been most extensively studied, being relatively accessible, and it contains the widest varia­tion in sediment types. I t may be conveniently split into intertidal and subtidal regions.

R E V IE W O F BENTHOS

There are several possible approaches by which the information on benthos may be summarized, the most obvious being in terms of some biological considera­tion such as communities, or of sediment types, or of hydrographic factors, and each of these approaches has both attractions and drawbacks. Glémarec (1973) has proposed a system of “ étages” , based on the tem­perature and on the thermal stability of the water column. This recognizes three divisions: an infra­littoral étage in shallow water along the shores which is eurythermal and of great seasonal and daily ampli­tude ; a coastal étage which although still eurythermal is of weak seasonal amplitude (< 10°C) and varies slowly; and an open sea étage below a strong ther- mocline for a large part of the year and which for the benthos is a stenothermal environment.

He has applied this system to the North Sea (Fig. 315) where his open sea étage corresponds to the region deeper than about 100 m where the temperature is always less than 10°C and varies little; his coastal étage lies roughly between 40 and 100 m depth, with the temperature always less than 12°C and varying

Table 169. Numbers and estimated dry weight of total meiofauna from typical habitats

Numbers par m 2 Dry weight per m 2

Intertidal Sand 2 - 58x 105 up to 1-7 gM ud 4 -1 18x 105 u p to 11-2 g

Subtidal Sand 1- 26x 105 up to 7-1 g(shelf) M ud 1- 20x 105 up to 1-1 g

60-

OPEN SEA ETAGE

■ 59-

FLADENGROUND

SKAGERRAK

COASTALETAGE

56-

. FARN

DOGGER

INFRALITTORALETAGE

52-

Figure 315.

408 A. D. M cIntyre

Table 170. Numbers of meiofauna per 10 cm2 at 4 intertidal sandy locations on the western North Sea coast, with data from the English Channel and the Scottish west coast for comparison

Firth o f F irth o f Yorkshire Tham es English ScottishForth Forth Estuary Channel W. Coast

Seaton Sands1 Seafield Sands1 Filey Bay2 W hitstable3 W hitsand Bay4 Firemore Bay5

N em atoda ................ 3242 4335 819 2926 198 1576C opepoda ................ 60 2 20 152 170 1921T u rbellaria 860 77 42 - 8 170G astro tricha 332 7450 18 — 10 73O thers ...................... 23 0 52 197 7 40

T o ta ls ....................... 4517 11864 951 3275 393 3780

1 M idtide level, summer, from M cIntyre (unpublished).2 M idtide level, summer, from G ray and Rieger, 1971.3 Annual m ean, from E. S. Perkins, see M cIntyre and M urison, 1973.4 M ean low water, annual mean, from Harris, 1972.5 M ean low w ater neaps, annual mean, from M cIntyre and M urison, 1973.

Intertidal regionsConsidering first the meiobenthos, information is

sparse in the region under consideration so that in summarizing recent work on U.K. intertidal zones in Table 170, data from the English Channel and the Scottish west coast has been included for comparison. The only other comprehensive work on the North Sea proper is that of Schmidt (1968) who recorded inter­tidal sand meiofauna densities at Sylt of 131-375 individuals per 10 cm2. Table 170 indicates the range of diversity and the structure of the community found in sandy habitats and confirms that nematodes and copepods tend to dominate the fauna on clean beaches while in polluted areas such as Seafield in the Firth of Forth and those described by Gray (1971) in north­east England, the situation seems more variable, and gastrotrichs are sometimes dominant while oligochae- tes may occur in relatively large numbers (194 per 10 cm2). Biomass data are not available from most of these surveys, but for Firemore Bay the dry weight of total meiofauna in the zone referred to in Table 170 is about 1 g/m 2, and this value may be used to place the rest of the counts roughly in perspective. I t would seem at present unwise to generalize about the struc­ture of intertidal sand meiofauna communities until further areas have been studied quantitatively. This reservation applies even more to intertidal mud. While the limited data available again indicate that nema­todes and copepods are predominant, it appears that other groups such as ostracods may become abundant in softer sediments (McIntyre, 1969).

This suggests that differences in the texture of the sediment may be reflected in fundamental changes in community structure. The sand meiofauna is essen­tially interstitial and many of the organisms can pene­trate deep into beach sand and can live and move in the spaces without displacing the sand grains, occur­

ring commonly down to a depth of 30 cm or more. O f eleven species of copepods common on one Scottish beach for example, all except one were of the “inter­stitial” rather than the “ benthic” type (McIntyre and Murison, 1973). However, as the deposit becomes finer and the interstices are filled up, living space and ventilation are reduced. Thus in predominantly muddy grounds the meiofauna is confined to the top few centimetres and the composition of the population is much changed, with the appearance of relatively large “benthic” copepods and ostracods as well as nematodes which can push through the sediment.

The significance of these observations for commer­cial fisheries is that while the juveniles of some im ­portant flatfish species feed on meiofauna (Edwards and Steele, 1968), they tend to select the larger “ benthic” species rather than the small “ interstitial” forms, so that meiofauna are likely to be a more im portant fish food on grounds with fine deposits.

Considering the intertidal macrofauna, most of the western North Sea beaches are exposed to wave action, and samples from such beaches on the north coast of Scotland and in Yorkshire (Table 171) show that the biomass is low and that the fauna consist almost entirely of polychaetes and amphipods. In more sheltered areas a richer fauna may be expected, and observations by Stephen (1929) suggest this is so al­though biomass data are not available. In the southern North Sea, in the Dutch, German, and Danish Wad- densea, shelter from wave action together with high nutrient input produce on the mud flats ideal con­ditions for macrofauna development. Although the number of species may not be greater than in more exposed regions, the num ber of individuals and bio­mass (Table 172) can be very high. Linke (1939) quotes values of hundreds of g/m 2 wet weight for the infauna of the German Waddensea, and Smidt (1951)

The benthos of the western North Sea 409

Table 171. Intertidal macrofauna of exposed sandy beaches. Numbers of individuals and dry weights mg per m 2, and total number of species found

Dunnet Bay1 Sandside Bay1 Strathy Bay1 Stoup Beck Sands2No. W t. Spp. No. W t. Spp. No. W t. Spp. No. W t. Spp.

M ollusca................ 0 0 0 0 0 0 5 0-28 1 0 0 0Polychaeta ............ 240 0-44 4 268 1-44 6 48 0-28 4 581 2-04 5C rustacea.............. 320 0-11 4 300 0-11 8 240 0-06 3 1733 0-68 7O th ers .................... 16 0-02 1 16 + 2 5 + 1 4 0-24 1

T o ta ls ..................... 576 0-57 9 584 1-55 16 298 0-62 9 2318 2-96 13

1 N ortheast coast of Scotland. Refers to region below M .T .L . Screen used, 0-5 mm. From Eleftheriou and M cIntyre (unpublished).2 English coast-Yorkshire. Calculated from Gray and Rieger, 1971. Screen used, 0-2 mm.

records similar figures for the Danish Waddensea. The work of Beukema (1974) confirms these high figures for the Dutch Waddensea. He records a mean value of 19-7 g/m2 ash-free dry weight from samples in the years 1970-1973, distributed among the animal groups as follows:

Large Mya Arenicola Cardium Macoma

6-2 5-0 2-1 1-8

O ther O ther Crustacea Totalmolluscs worms

1-0 1-9 1-7 19-7

The deep-living species, large Mya arenaria and Arenicola marina, made up 57% of the weight, while of the species living in the top 10-15 cm, Cardium edule and Macoma baltica made up 11 % and 9% respec­tively.

These intertidal sandy areas are the shoreward

extensions of flatfish nursery grounds, and in suitable situations the juvenile flatfish move up onto the shore with the rising tide to feed. A variety of other animals, particularly various crustaceans, make similar immi­grations and it is only during the high tide period that a megafauna may be found on the surface of intertidal sediments. At other times the megafauna present are mainly deep burrowing species (e.g. bivalve molluscs and polychaetes) which must be enumerated by specially large quadrat counts.

Subtidal regionsFor the subtidal meiofauna, populations of sand in

shallow water can be as high as in the intertidal zone, and the same major taxa occur. As the water deepens the sediments tend to become finer, and the density and diversity decrease. Data from other areas suggest that the 55-60 m contour often divides a rich shallow water fauna from a sparse deep water one (Wigley and McIntyre, 1964; Soyer, 1971). In the western

Table 172. Intertidal macrofauna of sheltered flats. Number of individuals per m2, total number of species (in brackets) and overall biomass in German Waddensea. Sieves used: 1-0 mm in Cardium zone, 0-5 mm in others. (Selected from Linke, 1939)

Scoloplos variation Pygospio variation Scrobicularia variation Corophium variation

Scoloplos Arenicola Pygospio Cardium Scrobicularia Mya Heteromastus Corophiumzone zone zone zone zone zone zone zone

Lam ellibranchiata .G astropoda.............Po lychae ta ..............C ru stacea ................O th e rs ......................

T otalindiv iduals..............

Overall community biomass(wet w eight)...........

768(1)1792(4)2560(3)

- - 630(2) 1082400(1) 528(3) - 1292(1)516(1) 5376(1) 63665(2) 1200(1) 88(1) 264(1) 1292(1)301(3) 23314(2) 105(3) 27600(2) 2640(4) 5544(3) 323(1)

11696(1) - 35(1) 400(1) - - 44251(1)

~

2112(1)(Oligochaeta)

16796(1)(Oligochaeta)

12513(5) 28690(3) 64435(8) 1111600(5) 5368(9) 5808(4) 67184(5)

30 g/m 2 300 g/m 2 1200 g/m 2 40 g/m 2

410 A. D. M cIntyre

Table 173. The Infralittoral Étage. Numbers of individuals and dry weights in g/m2 and numbers of species for various depths and sediments off the Scottish east coast. Screen used, 1-3 mm. For details see McIntyre (1958)

D epth 10-20 m D epth 20-35 m D epth 36-42 mAberdeen Coast St. Andrews Aberdeen Coast St. Andrews

Coast CoastCoarse sand Fine sand Coarse sand Fine sand

No. D ry Spp. No. D ry Spp. No. D ry Spp. No. D ry Spp.wt. wt. wt. wt.

M oray F irth (South Bank) Coarse sand

No. D ry Spp. wt.

M oray Firth (South Bank) Shell gravel

No. D ry Spp. wt.

L am ellibranchiata . 752 ] 22 451 II 14 566 ) 18 615 ]I 21 189 ]I 18 161 ] 201 4-71 1 1-01 1 2-26 ! 1-69 1 1-03 } 1-53O ther mollusca . . . 9 J 2 1 11 1 13 J 4 6 11 5 2 1f 3 17 j 3

Polychaeta .............. 415 2-46 38 304 0-91 29 224 1-27 40 280 0-71 42 249 1-72 31 530 1-33 44

E ch inoderm ata .. . . 232 1-48 7 23 2-25 5 79 1-25 9 65 1-80 8 144 0-77 5 120 0-04 4

C rustacea ................ 118 I 18 42 1I 10 34 I 18 27 1I 8 53 I 13 53 I 121\ 0-16 0-02 1!• 1-07 1 0-81 1 0-06 > 15-26*

O th ers ...................... 31 1 7 3 JI 4 74 J 6 14 JI 8 3 ) 3 45 \ 9

T o ta ls ....................... 1557 8-81 94 824 4-19 63 990 5-85 95 1007 4-91 92 640 3-58 73 926 18-16 92

* H igh values due to Ammodytes marinus.

North Sea the only information on meiofauna from the subtidal infralittoral étage refers to nematodes (Warwick and Buchanan, 1970) from off Northumber­land, and no weights are given, but Stripp and Gerlach (1969) summarize the meiofauna from the sandy sediments of the Venus gallina community at 22-27 m depth in the German Bight, which averages 266 individuals (mostly nematodes) per 10 cm2, with a wet weight biomass of 0-33 mg.

For macrofauna in this étage, data are available over several stretches of coast, and are summarized in Table 173. The im portant groups are clearly bivalve molluscs, polychaetes, echinoderms, and Cru­stacea, with molluscs most important in shallow water.

O ff NE England, information is available on the species composition of the communities on the coast of Northumberland (Buchanan, 1963), bu t weights are not given. Farther south, the benthos has been studied by Blegvad (1922) and in more detail by Davies (1923, 1925), who indicate that very high densities of fish food may be found in patches (par­ticularly of the bivalve Mactra) on the Dogger Bank. Community biomass data are not published, but Birkett (1954) quotes maximum values as high as 250 Mactra per m 2 with a biomass of 41 g dry wt/m2, for Mactra patches. Towards the German coast this com­munity occurs on firmer sand where it is dominated by another mollusc, Tellina tenuis, and has a mean

Table 174. The Coastal Étage. Numbers of individuals and dry weights in g/m2 and numbers of species for various depths and sediments in the western North Sea from summer surveys

M oray F irth Coast1

No. W t. r Spp.

Aberdeenshire Coast2

No. W t. Spp.

N orthum berland Coast3

No. W t. Spp.

“ Ekofisk” 4

No. Spp.

L am ellibranchiata .............. 265 Ï 13 572 18 35 0-19 5 18 6O ther m ollusca................... 13 1 3 38 ( 1 ?! 4 5 0-02 3 14 5Polychaeta............................ 323 1-08 29 338 1-40 23 910 1-78 42 2357* 20E chinoderm ata................... 35 1-31 4 78 2-87 7 1 1-08 2 72 4C ru stacea ............................. 63 \ 7 93 12 99 1-31 10 21 4O thers .................................... 55 1 6 185-f

> U'Oj8 15 0-14 4 237 5

T o ta ls ..................................... 754 3-24 62 1304 6-61 72 1065 4-52 66 2719 44

1 Sandy m ud a t 59-70 m depth. 1-3 m m screen used. From M cIntyre, 1958.2 Silty sand a t 46 m depth. 1-3 m m screen used. From M cIntyre, 1958.3 Fine sandy silt a t 80 m depth. 0-5 m m screen used. From Buchanan and Warwick, 1974.4 Sampling centred on 56°32'N 03°13'E, medium-fine sand a t 69 m depth. 1 m m screen used. From Dicks, 1976. * 94 % were Myriochele heeri.f Large num bers o f Phoronis no t included.

The benthos of the western North Sea 411

Table 175. The Open Sea Étage. Numbers of individuals and dry weights in g/m2 of the main group of macro­fauna and meiofauna at position 58°20'N, 00°30'E, depth 55 fath.

M acrofauna (0-5 m m sieve)

Num ber W eight Spp. M eiofauna N um ber W eight

Foram inifera............. 310+ 0-83 3+ N em atoda .................. 1845000 0-50

Bivalvia...................... 543 j 1-048 K inorhyncha............. 9000 0-02

O ther mollusca . . . . 202 6 O stracoda .................. 5000 0-09

O stracoda.................. 212 3 C opepoda.................. 52000 0-10

C um acea.................... 27 [ 0-285 N au p lii....................... 11000 0-01

T anaidacea ............... 120 4 Polychaeta................. 10000 0-07

A m phipoda............... 214 1 8 Bivalvia...................... 18000 0-09

Polychaeta ................. 965 3-74 38 O th ers ......................... 9000 0-06

Echinoderm ata........ 171 0-07 4O ther g roups........... 20 0-46 6

T o ta l ........................... 2 784 6-42 85 T o ta l ........................... 1959000 0-94

G rand Total 1961 784 individuals weighing 7-36 g per m 2

num ber of macrofauna individuals of 375/m2 and a wet weight of 16 g/m2 (Stripp and Gerlach, 1969).

TH E COASTAL ÉTAGE

This includes several types of deposit from mud to muddy sand. Again meiofauna observations are sparse, and the work of Warwick and Buchanan (1970) on nematodes gives an estimate of over 815000 individuals per m 2 and suggests that sediment type is the im­portant factor for this group rather than depth of water.

Observations on the macrofauna include a study of the Amphiura chiajei community off Northumberland (Buchanan, 1963), and details of the fauna of the deeper muddy channels inshore and the outer silty parts of the coastal sand farther north (McIntyre, 1958), as well as observations from the Ekofisk Ground in the centre of the North Sea (Dicks, 1976). The type of macrofauna community found is set out in Table 174, showing that in the shallow part of this étage the fauna is well mixed, but that as deeper water is approached, polychaetes tend to dominate. The dry weights (not including “ Ekofisk)” are in the range 3 to 7 g/m2.

For the megafauna, information is available on the natant epifauna off the Northumberland coast from Allen (1966). He showed that it consisted largely of caridean shrimps and he studied the distribution and biology of 13 species, but he did not give quantitative details of density and biomass.

TH E OPEN SEA ÉTAGE

Most of the quantitative data from the deeper parts of the North Sea refer to the Fladen Ground, which may be taken as reasonably representative of the region as a whole (McIntyre, 1961, 1964). The bottom is

predominantly of coarse silt (particle size 0-05- 0-02 mm), and the meiofauna is composed largely of nematodes, which make up 61 %—9 7 % of the indivi­duals and 43%-75% of the dry weight, with copepods and ostracods next in importance. The mean numbers and dry weight biomass over a year are given in Table 175.

The macrofauna held by a 0-5 mm sieve is domi­nated numerically by Foraminifera, the most obvious species being Saccammina spherica. Among the metazoa, Polychaeta is the dominant group, making up about 58% of the total weight and represented by some 38 species. Molluscs are next in importance, mostly small bivalves, followed by Crustacea, chiefly small amphipods and tanaids. An indication of the com­position and density of the macrofauna and of its dry weight biomass is given in Table 175.

Farther north, in the deep water east of Shetland, the benthos is dominated in places by the polychaete Ditrupa subulata (Stephen, 1923), but detailed infor­mation in these areas is lacking.

CHANGES IN T H E BENTHOS

Meiobenthos has been the subject of quantitative research only in recent years, and the megafauna for which long-term data are available are mainly com­mercial species which are being dealt with elsewhere in this symposium, so consideration of long-term changes will be confined here mainly to the macro­fauna.

Records of benthos in the western North Sea extend back into the last century, and the older data usually refer to selected taxonomic groups and to relatively localised coastal areas. There are extensive data for example from the St. Andrews area, from the region northeast of England covered by the Dove Marine Laboratory and from Whitstable in the Thames

412 A. D. McIntyre

estuary (Newell, 1954). Older records of this kind can be compared with modern surveys in the same areas in an attem pt to detect changes in terms of presence or absence of species. However, such efforts usually prove to be of little value. A new survey inevitably uncovers new species, and in most cases it is difficult to decide if these have simply been missed in the earlier survey or are genuinely new introduc­tions. In polluted areas it may be possible to detect reduction in species density and ultimately in biomass, bu t these changes are usually unequivocal only in zones of gross pollution, beyond which apparent changes are often open to dispute.

From the fisheries point of view the most im portant benthos changes are likely to be those introducing either a major quantitative alteration in the biomass or a shift to a new population structure which has some significance to the predators. Detection of such changes ideally entails quantitative records, and the investigator is thus restricted in his time scale to the period from about 1910 when the first effective quantitative work began.

Two sorts of record are relevant. The first is a con­tinuous and extended time series, which is most valuable because it gives an indication of year-to-year variability. The second is a broken series, which may am ount to as little as a collection of two sets of observations from the same site or community made a t intervals of several years, but a t least allowing some comparison of change with time. Because such in ­formation is sparse in the western North Sea, relevant data from a much wider area have been brought together and these are set out below.

CONTINUOUS TIME SERIES

Western North Sea

In a four-year study (1971-1974) off the northeast coast of England, Buchanan et al. (1974) showed that a benthic mud association at 80 m depth maintained substantial stability in terms of species, but that the num ber of individuals more than doubled.

German Bight (see also contributions by Ziegelmeier and by Rachor and Gerlach in this volume).

Initial data collected from this area by Petersen grab are available for the years 1922-1924 from Hag- meier (1925), who also made a macrobenthic survey north of the East Friesian Islands between 1925 and 1929 (Hagmeier, 1930). In 1949, Hagmeier’s initial survey was continued on a more exact basis in the form of duplicate samples from a Van Veen grab at about 20 stations in spring and autum n (Ziegelmeier, 1963). Fluctuations in numbers of animals recorded in all these studies were attributed partly to spatfall

variations which gave rise to short-term population peaks, often associated with increases in predatory species. Later, Stripp (1969) surveyed the inner part of the German Bight, while grounds northwest of Hel­goland were sampled by Stripp and Gerlach (1969).

The latter grounds were regularly revisited there­after in connection with the effects of acid-iron waste dumping (Rachor, 1972). Finally, Dörjes and his colleagues have made a series of studies of animal- sediment relationships in several areas of the German Bight (Reineck et al., 1968; Dörjes et al., 1969 and1970).

Although the studies listed above are not all directly related, they do, taken together, provide a valuable record of the benthos of the German Bight over a long period. In a shallow water area such as this, where extreme winter temperatures and severe gales can influence the bottom, short-term stability (from one season to another or even one year to another) cannot be expected in the benthic fauna. Rachor and Gerlach (this volume) document substantial short­term changes in some small polychaetes and crusta­ceans which could be explained by such influence, while Ziegelmeier (1963) cites low temperatures as a direct cause of destruction of Echinocardium cordatum in shallow coastal areas in some years. Contrasting with these fluctuations, a few species do seem to show definite trends. A clear decline is evident in oysters from the Helgoland oyster bank. This community was studied by Caspers (1950), who states that oyster stocks flourished there, particularly between 1875 and 1886, but there was later a gradual decline, probably due to overfishing, so that by 1924 the fishery was no longer profitable. Later, Ziegelmeier (1963) notes a steady reduction in the numbers of Hydrobia ulvae at a station east of Helgoland between the start of his surveys in 1949 (when numbers of individuals of 35000 per m 2 were recorded) and the year 1967, after which few live specimens were found in the area. Finally Dörjes et al. (1969), comparing their data with those of Linke (1939) and Schuster (1952), name Bodotria scorpoides, Eriocheir sinensis, Cancer pagurus, and Ophiura texturata as missing or declining species, and Chaetozone setosa, Retusa obsuta, and Cirratulus sp. as new to the area.

However, in general the data from the German Bight do not indicate that any large-scale overall change in the fauna has taken place in recent decades.

Limfjord

Perhaps the most extensive time series of benthic data in existence refers to the Limfjord, where grab samples were collected for a period of almost 40 years between 1911 and 1950, in 9 of the Broads (Blegvad, 1951). The published data show mean dry weights

The benthos of the western North Sea 413

per m 2 separately for the main species for most of the years, often with values for spring and autumn. The overall picture shows a downward trend in the most im portant burrowing forms (polychaetes and some soft-shelled lamellibranchs). The mean weight for 1928-1954 was about one quarter to one half of the earlier period, and indeed from 1933 to 1950 there were few instances of the rich year classes of animals which were a feature of the years before 1930. No single explanation has been put forward for this down­ward trend, but a num ber of factors were considered. The disappearance of eel grass postera about 1933 was discussed but not thought to be relevant. Three con­secutive severe ice winters between 1939 and 1942 were seen as important contributors, a t least in the later period. More intensive fishing, particularly the use of trawls from powerful motor boats, were also thought relevant. Higher populations of small pre­datory fish might have had a further effect.

Information is also available on the megabenthos of the Limfjord. Poulsen (1951) lists 17 species of large invertebrates caught mainly by eel-seine and examines their fluctuations in the period 1928-1950. Again the severe winters of 1939-1942 are suggested as a factor of importance, and overfishing of the com­mercial species also seems relevant.

Scottish West Coasta. The bivalve mollusc Tellina tenuis was studied by Stephen (1953) in the Clyde in Kames Bay more or less continuously between 1926 and 1951. He was concerned mainly with spat survival, but he con­sidered that he could detect changes in two important aspects. First, very large spatfalls found frequently in the early part of the period did not occur after 1940, and second, the structure of the population changed, so that in the later years older and larger individuals were present.

b. Populations of Tellina tenuis have been examined in another part of the Clyde (Hunterston Sands) by Barnett (1971) since 1960 in an uninterrupted series of observations which are still continuing. He has also looked, but not so continuously, at several other species of molluscs and small crustaceans in the same area, and in associated work, a meiobenthic harpacticoid has been studied (Barnett, 1972). The object has been to examine the effects of a heated effluent from a power station, and Barnett has been able to demon­strate that certain functions of the populations near the outfall have changed compared with control po­pulations nearby. Growth rates and the timing of the breeding cycle in particular were affected, but it was not possible to demonstrate significant changes in the structure of the populations.

800

700

600

500

“ A 00

fe 300-QE3 200

100

N um bers o f Te llina tenuis

Spring & A u tum n 1 9 6 5 -1 9 7 2

s___ A

1965 1966 1967 1968 1969 1970 1971 1972

Figure 316.

c. In a sea loch system on the Scottish west coast the effect on the softbottom benthos of pulp-mill effluent was studied by Pearson (1972). He was able to follow changes in the benthos and later to demonstrate that these could be correlated with changes in the effluent. Similar effects have been reported from Sweden. (Rosenberg, 1971).

d. Records are also available for the sand ecosystem of an exposed bay at Firemore in Loch Ewe on the Scottish west coast, where intertidal and subtidal benthos have been examined since 1965 and from which data are available on Tellina tenuis on the beach, meiofauna on the beach, and general macrofauna in the subtidal zone. For Tellina tenuis (see Fig. 316) the trend in population numbers has been downwards since 1965, and a study of the age structure of the population suggests that there has been no major recruitment to the intertidal zone since 1963. In years for which additional information is available, recruit­ment failure can apparently be explained in such terms as heavy predation, failure of gonad maturation, or adverse weather a t the time of settlement (M cIn­tyre, 1970). However, these are local effects and the populations of these species on other parts of the coast were not always affected in the same way. The year 1963 did, however, seem to be a good spawning year for all areas for which records are available.

For total subtidal macrobenthos of this bay the samples showed that although for the most part the same species were found, there were considerable changes in their relative density in the community from year to year over an eight-year period. Some important species declined in numbers for a year or two then recovered, and such changes could apparently be accounted for by variations in predation pressure by fish which were the dominant predators. The data so far do not suggest any definite trend.

Meiofauna was also studied on this beach more or less continuously for eight years, and the data show that although the population was much reduced in

414 A. D. M cIntyre

one year due to sediment movements caused by severe gales, recovery was rapid and no significant overall change was detected in the total population or in the relative abundance of the various taxa (McIntyre and Murison, 1973).

INTERRUPTED OBSERVATIONS

North Sea

a. In the Helgoland region, Heincke (1894) recorded Cardium fasciatum as one of the commonest molluscs of the area, bu t later surveys by Gaspers (1939) and Ziegelmeier (1963) suggest a marked decline.

b. Studies on the benthos from the deeper parts of the northern North Sea in the early twenties have already been mentioned (Stephen, 1923), and further studies in the late fifties in the Fladen area (McIntyre, 1961) give a comparison for that region at an in ­terval of more than 30 years. The earlier data are rather sparse and refer only to numbers of individ­uals, but comparisons of the two surveys — making allowance for the differences in techniques - do not suggest any major change has taken place.

c. Surveys made on the Dogger Bank by Davies from1921 to 1923 and by Ursin in 1950/1951 are discussed by Birkett (1953) in the light of his own work in that area. He agrees that there are differences between the results of the earlier and later surveys, but points out that differences in the seasonal timing of the surveys, and in the type of collecting gear used, could explain most of the apparent faunistic changes.

d. Ursin (1960) has brought together all available observations on echinoderms in the central North Sea between 1872 and 1955, and states that within this period, nine species have decreased or disappeared, while five have increased in abundance. Some of the changes may be the effect of the cold winter of 1947, while some of the others could be associated with known temperature changes, but Ursin considers that in general the rare species have become more rare and the abundant ones more abundant. He suggests however that the distribution of echinoderms is tied up not so much with temperature, salinity, and soil as with particular plankton assemblages and water masses, so that the changes may indicate increased dominance of Sagitta setosa in water in the central North Sea.

e. Repeated observations are often available in areas of commercial interest. Thus the oyster banks round the Friesian Islands were surveyed from 1869 to 1891 (Möbius, 1893) and later by Hagmeier and Kändler (1927), and the data do not suggest that any signi­

ficant change has taken place between the two sur­veys, allowing for later improved techniques of sampling.

f. On the east coast of England the intertidal sand fauna of Robin Hood’s Bay was examined in the 1950’s by Coleman and Segrove (1955) and this study was repeated nearly 20 years later (Gray and Rieger,1971). The later survey showed a higher population level and biomass but essentially the same community, and the differences were attributed to improved sampling techniques.

Irish Sea

The composition and distribution of sand fauna in Port Erin Bay in the Isle of M an (Irish Sea) was described in 1900, while in the early thirties Moore (1933) brought together observations for the years 1930-1933 and made comparisons with the earlier data. He pointed out that with the notable exception of two polychaete worms (Arenicola marina and Lanice conchilega), the sand fauna had greatly changed. Two lamellibranch molluscs (Mactra corallina and Spisula solida) had disappeared from the Bay, and several species had retreated from the intertidal zone but were still found in deeper water. Two species of the poly­chaete Nephtys had retreated from the beach but had been replaced by a third species of the same genus. A num ber of species not recorded in the earlier summary were im portant components of the popu­lation 30 years later, but these were mainly mud living forms and were associated with a patch of muddy sand which appeared in the Bay as a result of harbour construction.

English Channel

A number of studies have been made in the English Channel from 1948 onwards by N. A. Holme, and he has been able to compare his data with those collected by earlier workers. Comparing his own data of 1950 around the Eddystone with a survey by Allen in 1899, he finds no reason to suppose a major change has occurred in 50 years in that area except that the scaphopod mollusc Dentalium entalis has disappeared (Holme, 1953).

In Great West Bay (Holme, 1950) no major quali­tative change seemed to be detectable in the 25 years since 1923, and quantitatively (apart from a possible decline in numbers of the molluscs Spisula and Abra alba) there was no evidence of change in overall abundance.

Off Plymouth (although as in all these comparisons, quantitative conclusions are difficult because of dif­ferences in gear, techniques, and exact locations) there

The benthos of the western North Sea 415

is the suggestion of a decline in numbers of certain benthic invertebrates in the 27 years covered, parti­cularly the lamellibranchs Abra alba and Cultellus pellucidus and the sea urchin Echinocardium cordatum. Overall density of lamellibranchs had declined to about 36% of their earlier value.

In the western English Channel, work at present in progress with dredge and underwater TV shows a remarkable decline in the Ophiothrix fragilus offshore in the Plymouth area. This species has largely dis­appeared from the dense beds found by Vevers 20 years earlier.

In his recent work in the Channel as a whole, Holme feels (although he is not able to quantify this) that there is a scarcity of young bottom stages of many molluscs and perhaps of other invertebrates, which may indicate declining populations which are not being replaced at a sufficient rate to maintain stocks. He considers this may be part of the well- known picture of reduced fertility in the Channel (Holme, 1966).

Finally, after the severe winter of 1962/1963, when the sea temperature a t Weymouth and Pool Bay were 4° to 5°C below the mean and held at or below 3°C for a month or so, Holme (1967) examined the benthos there and compared it with his surveys of 1958 and 1959. He found the majority of species survived with perhaps some reduction in numbers, but the molluscs Venus verrucosa and Venerupis rhomboïdes suffered heavy mortality and Pecten maximus was wiped out. These are all species at the extreme limits of their geo­graphical range in an area which is subject to pro­nounced hydrographical changes.

D ISC U SSIO N

In summarizing these data it is clear first of all that it is sometimes possible to detect significant changes in the benthos, but that in such cases the changes are usually attributable to specific identifiable events such as severe winters, or environmental changes brought about by man. These changes tend to be restricted to certain species or to be geographic­ally localized, and their significance to fisheries can usually be determined.

In circumstances where identifiable events are not evident, the most straightforward long-term evidence from surveys on the English Channel Eddystone grounds in 1899 and 1950, the Fladen Ground in1922 and 1959, and on the Yorkshire intertidal sand fauna in 1950 and 1969, does not show any detectable difference. We do not know what occurred between the surveys, but the sparse evidence points to a long­term stability in the benthos there at these times.

The remaining evidence is more confused. There

are suggestions that mean weights of benthos in some Danish waters were lower after 1928 and rich year classes were fewer after 1933; that spatfalls of Tellina tenuis on the Scottish west coast were smaller after 1940; that certain species in the German Bight have declined during the present century; that in the English Channel off Plymouth certain brittle stars have declined in the past 20 years and lamellibranchs in the same area have declined between 1923 and 1950, while in a wider area of the Channel there is a suggestion of reduced recruitment of lamellibranchs in recent years. These data are most unsatisfactory in their vagueness and lack of statistical rigour, bu t the one consistent feature seems to be that where we have information covering a long period and indicating a possible change, that change seems to be generally one of reduction.

However, apart from the German Bight data, such changes were not observed in the North Sea proper, and all we can say from the meagre benthic infor­mation on the North Sea is that there is no conclusive evidence of long-term change. Present available studies of the benthos therefore have very little to contribute to the explanation of the discussed changes in the fish stocks in the North Sea, but it might be useful to conclude with a brief consideration of what sort of changes might be important in a fisheries context and how these might be monitored in the future.

Microfauna and meiofauna react quickly to environ­mental pressures and, although they may be of less direct relevance to fisheries, may be useful in pro­viding an early warning of potential changes. For example, on a Scottish beach subject to eutrophica­tion, but where a diverse macrofauna flourished, dramatic alterations in the meiofauna populations (reduction in copepods, increase in nematodes) have been observed, which could be the first indication of a pollution effect (McIntyre, 1977).

Macrofauna data covering a num ber of years are available from a flatfish nursery ground on the Scottish west coast (McIntyre and Eleftheriou, 1968; Steele et al., 1970). These show that over a four-year period (1965-1968) the numerically abundant species in the community were also those most important as fish food, and included quite a small number of species,1 lamellibranch, 3 polychaetes, 4 amphipods, and2 cumaceans being particularly important. Over the study period, although the amphipods remained re­latively stable, the other species showed considerable fluctuations, the population of the polychaete Spio filicornis for example being almost eliminated. Since detailed observations had been made on the predation of fish on these species, it was possible to suggest that the fluctuations could be connected with changes in predation pressure.

416 A. D. McIntyre

Another relevant study is a t present being carried out on a soft bottom community a t 80 m off the northeast coast of England and data for the first four years (1971-1974) are reported by Buchanan et al. (1974). In a community of some 66 species, 15 ac­counted for 83% of the total individuals, and in the four years studied, while there was no significant difference in the num ber of species, the numbers of individuals more than doubled. O f the top 15 species, 6 showed no significant change, and of the remaining 9 species, 3 showed a persistent rise in numbers while the remainder fluctuated. The general picture of the population is of three basic components: one group of conservative species which remained stable, a second volatile group which was subject to great fluctuations from year to year, and a third opportunistic group which rapidly increased to replace the volatiles.

The above studies seem to suggest that over short time scales of several years we can expect significant fluctuations of macrobenthic species which may be accounted for by such factors as predation. A task for the benthic biologist in the next few years might thus be defined as evaluating the North Sea communities summarized in Tables 170 to 175 and identifying the conservative, volatile, and opportunistic species in each. For long-term monitoring the conservative spe­cies might deserve most attention, and there could be the possibility of concentrating on a few species and developing a monitoring programme for long-term changes unhampered by the highly labour intensive operations common to most benthic surveys.

REFERENCES

Allen, J . A. 1966. T he dynamics and inter-relationships o f mixed populations of Caridea found off the north-east coast of England. In Some C ontem porary Studies in M arine Science, pp. 45-66. Ed. by H . Barnes. Allen and Unw in, London.

Barnett, P. R . O . 1971. Some changes in in tertidal sand com­munities due to therm al pollution. Proc. R . Soc. Lond., 13, 177: 353-364.

Barnett, P. R . O . 1972. Effects o f w arm w ater effluents from power stations on m arine life. Proc. R . Soc. Lond., B, 180: 497-509.

Beukema, J . J . 1974. Seasonal changes in the biomass o f the macrobenthos of a tidal flat area in the D utch W adden Sea. N eth. J . Sea Res., 8(1): 94-107.

Birkett, L. 1953. Changes in the composition of the bottom fauna o f the Dogger Bank area. N ature, Lond., 171: 265.

Birkett, L- 1954. Standing crop, m ortality and yield o f a Mactra patch. ICES C M 1954. N orth Sea Committee. No. 72.

Blegvad, H . 1922. Anim al communities in the southern N orth Sea. Proc. Zool. Soc. Lond., 27-32.

Blegvad, H . 1951. Fluctuations in the amounts of food animals o f the bottom of the Limfjord in 1928-1950. Rep. Dan. biol. Stn, 53: 3-16.

Buchanan, J . B. 1963. T he bottom fauna communities and their sediment relationships off the coast o f N orthum berland. Oikos, 14: 154-175.

Buchanan, J . B., Kingston, P. F. & Sheader, M . 1974. Long­

term population trends of the benthic m acrofauna in the off­shore m ud o f the N orthum berland coast. J . m ar. biol. Ass. U .K ., 54: 785-795.

Buchanan, J . B. & W arwick, R . M . 1974. A n estimate o f benthic macrofaunal production in the offshore m ud of the N orthum ­berland coast. J . m ar. biol. Ass. U .K ., 54: 197-222.

Cadée, G. S. & Hegem an, J . 1974. Prim ary production of the benthic microflora living on tidal flats in the D utch W adden­sea. Neth. Jo u r. Sea Res., 8(2-3): 260-291.

Caspers, H . 1939. Die Bodenfauna der Helgoländer Tiefen Rinne. Helgoländer wiss. M eeresunters., 2(1): 1-112.

Caspers, H . 1950. Die Lebensgemeinschaft der Helgoländer Austernbank. Helgoländer wiss. M eeresunters., 3, 119 List (Sylt).

Colman, J . S. & Segrove, F. 1955. T he fauna living in Stoupe Beck Sands, Robin H ood’s Bay (Yorkshire, N orth Riding). J . Anim. EcoL, 24: 426-444.

Davies, F. M . 1923. Quantitative studies on the fauna of the sea bottom . No. 1. Prelim inary investigation of the Dogger Bank. M in. Agric. Fish. Fishery Invest., Ser. 2, 6, No. 2.

Davies, F. M . 1925. Q uantitative studies o f the fauna of the sea bottom . No. 2. Results o f the Investigations in the southern N orth Sea. 1921—24. M in. Agric. Fish. Fishery Invest., Ser. 2, 8, No. 4.

Dicks, B. 1976. Offshore biological monitoring. In M arine Eco­logy and Oil Pollution. Ed. by J . M . Baker. Applied Science Publishers, 566 pp.

Dörjes, J . , Gadow, S., Reineck, H . E. & Singh, I. B. 1969. Die R innen der Ja d e (Südliche Nordsee). Sedimente und M akro- benthos. Senckenberg. m arit., (1)50: 5-62.

Dörjes, J . , Gadow, S., Reineck, H . E. & Singh, I. B. 1970. Sedi- mentologie und M akrobenthos der N ordergründe und der Aussenjade (Nordsee). Senckenberg. m arit., 2: 31-59.

Edwards, R . & Steele, J . H . 1968. T he ecology of 0-group plaice and common dabs a t Loch Ewe. 1. Population and food. J . exp. m ar. Biol. Ecol., 2: 215-238.

Fenchel, T . 1968. T he ecology of m arine microbenthos. I I . The food of m arine benthic ciliates. Ophelia, 5: 73-121.

Glémarec, M . 1973. The benthic communities o f the European continental north Atlantic continental shelf. Oceanogr. mar. Biol. Ann. Rev., 11: 263-289.

Gray, J . S. 1971. The effects o f pollution on sand meiofauna com­munities. Thalassia Jugosl., 7(1): 79-86.

Gray, J . S. & Rieger, R . M. 1971. A quantitative study of the meiofauna of an exposed sandy beach, a t R obin Hoods Bay, Yorkshire. J . m ar. biol. Ass. U .K ., 51: 1-19.

Hagm eier, A. 1925. Vorläufiger Bericht über die vorbereitenden Untersuchungen der Bodenfauna der Deutschen Bucht mit dem Petersen-Bodengreifer. Ber. dt. wiss. K om m n Meeres­forsch., 1: 247-272.

Hagm eier, A. 1930. Eine Fluktuation von Mactra (Spisula) sub- truncata D a Costa an der ostfriesischen Küste, Ber. dt. wiss. K om m n Meeresforsch., N .F. 5: 126-155.

Hagm eier, A. & K ändler, R . 1927. Neue U ntersuchungen im nordfriesischen W attenm eer und au f den fiskalischen Austem - bänken. Wiss. Meeresunters. Abt. Helgoland, 16, no. 6.

Harris, R . P. 1972. The distribution and ecology of the intertidal meiofauna o f a sandy beach a t W hitsand Bay, East Cornwall. J . m ar. biol. Ass. U .K ., 52: 1-18.

Heincke, Fr. 1894. Die Mollusken Helgolands. Wiss. Meeres­unters. Abt. Helgoland, N .F. 1.

Hickel, W. & Gunkel, W. 1968. U ntersuchungen über die Häu- figheit der Bakterien in der obersten Sedimentschicht der Deutschen Bucht in Beziehung zu den Substrateigenschaften. Helgoländer wiss. Meeresunters., 18: 213-231.

Holme, N. A. 1950. The bottom fauna of G reat W est Bay, J . mar. biol. Ass. U .K ., 29: 163-183.

Holme, N. A. 1953. T he biomass of the bottom fauna in the

The benthos of the western North Sea 417

English Channel off Plym outh. J . m ar. biol. Ass. U .K ., 32 : 1-49.

Holm e, N. A. 1966. The bottom fauna of the English Channel. I I . J . m ar. biol. Ass. U .K ., 46: 401 -*193.

Holm e, N . A. 1967. Changes in the bottom fauna of W eymouth Bay and Poole Bay following the severe w inter o f 1962—63, J . m ar. biol. Ass. U .K ., 47: 397-405.

Linke, O . 1939. Die Biota des Jadebusenwattes. Helgoländer wiss. Meeresunters., 1(3): 201-348.

M cIntyre, A. D. 1958. The Ecology of Scottish Inshore Fishing Grounds. 1. The bottom fauna of east coast grounds. M ar. Res., 1: 1-24.

M cIntyre, A .D . 1961. Quantitative differences in the fauna of boreal m ud associations. J . m ar. biol. Ass. U .K ., 41: 599-616.

M cIntyre, A. D. 1964. Meiobenthos of sub-littoral muds. J . m ar. biol. Ass. U .K ., 44: 665-674.

M cIntyre, A. D. 1969. Ecology of M arine Meiobenthos. Biol. Rev., 44: 245-290.

M cIntyre, A. D. 1970. The range of biomass in intertidal sand w ith special reference to the bivalve Tellina tenuis. J . m ar. biol. Ass. U .K ., 50: 561-575.

M cIntyre, A. D. 1977. Effects o f pollution on inshore benthos. In Ecology of M arine Benthos. Ed. by B. C. Coull. Belle W. Baruch L ibrary in M arine Science, No. 6. University of South Carolina Press, Columbia.

M cIntyre, A. D. & Eleftheriou, A. 1968. The bottom fauna of a flatfish nursery ground. J . m ar. biol. Ass. U .K ., 48: 113-142.

M cIntyre, A. D. & M urison, D. 1973. The meiofauna of a flat­fish nursery ground. J . m ar. biol. Ass. U .K ., 53: 93-118.

M öbius, K . 1893. Ü ber die Thiere der schleswig-holsteinischen Austernbänke, ihre physikalischen und biologischen Lebens­verhältnisse. Sitzungsber. Kgl. Pr. Akad. d. Wissensch. 2. Ber­lin, 8, 67.

M oore, H . B. 1933. A comparison of the sand fauna of Port Erin Bay in 1900 and in 1933. Proc. malac. Soc. Lond., X X (V I): 285-294.

Newell, G. E. 1954. The m arine fauna of W hitstable. Ann. Mag. n a t. Hist., 7: 321-350.

Pearson, T . H . 1972. The effect of industrial effluent from pulp and paper mills on the m arine benthic environment. Proc. R. Soc. Lond., 5 180: 469-485.

Poulsen, E. H . 1951. Changes in the frequency of larger bottom invertebrates in the Limfjord in 1927-1950. Rep. Dan. biol. Stn, 53: 17-35.

R achor, E. 1972. O n the influence o f industrial waste containing H 2S 0 4 and FeSO , on the bottom fauna off Helgoland (Ger­m an Bight). In M arine Pollution and Sea Life. Ed. by M. Ruivo. Fishing News (Books) L td., London. 624 pp.

R achor, E. & Gerlach, S. A. Changes of macrobenthos in a sub­littoral sand area o f the Germ an Bight, 1967 to 1975. This volume, p. 418.

Reineck, H .-E., Dörjes, J . , Gadow, S. & Hertweck, G. 1968.

Sedimentologie, Faunenzonierung und Faziesabfolge vor der Ostküste der inneren Deutschen Bucht. Senckenberg. leth., 49 (4 ): 261-309.

Rosenberg, R. 1971. Recovery of the littoral fauna in Saltkälle- fjord subsequent to discontinued operations o f a sulphate pulp- mill. Thalassia Jugosl., 7: 341-351.

Schmidt, P. 1968. Die quantitative Verteilung und Populations­dynam ik des Mesopsammons am Gezeiten-Sandstrand der Nordseeinsel Sylt. I. Faktorengefüge und biologische Gliede­rung des Lebensraumes. In ter. Rev. der gesamten Hydrobiol. Hydrogr., 53: 723-779.

Schuster, O. 1952. Die V areler R inne im Jadebusen. Abh. senckenberg. naturforsch. Ges., 486: 1-38.

Smidt, E. L. B. 1951. Animal production in the Danish W adden­sea. M eddr K om m n Danm .Fisk- og Havunders. (Serie Fiskeri), 11: 1-151.

Soyer, J . 1971. Bionomie benthique du plateau continental de la côte Catalane Française. V - Densités et biomasses d u meio­benthos. Vie Millieu, X X II(2 ) Ser. B .: 351-424.

Steele, J . H ., M cIntyre, A. D., Edwards, R . R . C. & Trevallion, A. 1970. Interrelations o f a young plaice population w ith its invertebrate food supply. In Animal Populations in relation to their food resources. Ed. by A. Watson, Blackwell, 477 pp.

Stephen, A. C. 1923. P re lim inary survey of the Scottish waters of the N orth Sea by the Petersen grab. Sei. Invest. Fish. Scot., 1922, 3: 21 pp.

Stephen, A. C. 1929. Studies on the Scottish m arine fauna: The fauna of the sandy and m uddy areas of the tidal zone. Trans. R . Soc. Edinb., 56: 291-306.

Stephen, A. C. 1953. Life on some sandy shores. In Essays in M arine Biology, pp . 50-72. Ed. by S. M . M arshall and A. P. Orr. Oliver & Boyd, Edinburgh.

Stripp, K . 1969. Die Assoziationen des Benthos in der Helgo­länder Bucht. Veröff. Inst. Meeresforsch. Bremerh., 1 2 :9 5 - 142.

Stripp, K . and Gerlach, S .A . 1969. Die Bodenfauna im Ver­klappungsgebiet von Industrieabwässern nordwestlich von Hel­goland. Veröff. Inst. Meeresforsch. Bremerh., 12: 149-156.

Ursin, E. 1960. A quantitative investigation of the echinoderm fauna of the central N orth Sea. M eddr Danm . Fisk- og H av­unders. I I , No. 24.

Warwick, R . M . & Buchanan, J . B. 1970. The meiofauna off the coast of Northum berland. I. The structure of the nematode population. J . m ar. biol. Ass. U .K ., 50: 129-146.

Wigley, R . L., and M cIntyre, A. D. 1964. Some quantitative comparisons of offshore meiobenthos and macrobenthos south of M artha’s Vineyard. Limnol. Oceanogr., 9: 485-493.

Ziegelmeier, E. 1963. Das M akrobenthos im Ostteil der Deut­schen Bucht nach qualitativen und quantitativen Bodengreifer­untersuchungen in der Zeit von 1949-1960. Veröff. Inst. Meeresforsch. Bremerh., Sonderband. Drittes Meeresbiol. Symp. 23-25 Okt. 1962 in Bremerhaven, 101-114.

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