This paper not to be cited without prior reference to the author

'.

International Concil for

the Exploration of the Sea

C.M. 1982/L: 2

Biological Oceanography

Committee

BIOMASS DISTRIBUTION AND PRODUCTION ESTIMATES

OF MACRO-ENDOFAUNA IN THE NORTH SEA

by

Eike Rachor

Institut für Meeresforschung; D-2850 Bremerhaven, FRG

ABSTRACT

Information about biomass distribution and production of macro­

endofauna in the whole North Sea is very limited, especially

regarding the central and northern North Sea. A provisional

biomass distribution map is drawn (Fig. 1), and data about

annual P/B ratios are compiled. A rough estimate of total

North Sea macrobenthos biomass is 1.6 mill. t ash-free dry

weight. Annual P/B may be as high as 2, which is sufficient

for supporting demersalfish production.

rnjers~a~5~n~ an5 ~odel11nq =f ~arlne e=csystems and realistl=

estl~a:e5 abo~~ proj~~~:Vlty an5 yields depend largely on tne va:~e

of informatlcn O~ han5 an5 re5 int0 the syste~. As rar as J can see,

the ln~or~a~1C~~ a~ailat:E a~~ ~se~ ab0~~ the benthos fcr u~de~-

standln? the Nortr. Se~ ecosy~te~ 1s very llrnited ane varies widely. ~

Thus, N\~ERSE~ & LR=I:~ (1977) in their modellinq North Sea fishe-

ries took a macrober.t~icbiomass value of 16 mill. t from McI~TYRE's

(1975) data, considering, however, 12 mill. t to be more realistic.

STEELE (1965, 1974) used earlier da~a o~ McINTYRE, which were only

half as high (about 6.5 mill. t). Assumptions about production of

macrobenthos are eveL more arbitrary, as they are based mainly on

single population studiesin restricted nearshore areas. So, models

about the North Sea have evolved, in which the role of the benthic efauna is simplif~ed, although there are, for example, difficulties

to understand the increased yields of demersal fish since the six-

ties, whereas the main pelagic fish declined.

In his review about the benthos of the western North Sea, }1cINTYRE

(1978) summarized the quantitative da ta available for that area

includin? information about meiofauna ane about variability of

bottorr. fauna in the whole North Sea.

This paper is intended to summarize available biomass and produc­

tivity estirnates about the macro-endofauna of the whole North Sea

taking into account new investigations fromthe northern area ..

(ELEFTHERIOU, pers. COITE., KINGSTON , pers. cornrr..), the "Dana"

results of the Dogger Bank (URSIN, 1960; Klro~EGAARD, 1969; PETERSEN,

(1977), outcome from the southern North Sea (GOVAERE et al., 1980;

CREUTZBERG et a1., 1982) and the German Bight (SALZWEDEL et a1.,

in prep.).

Since spatial and temporal variability of the benthos is known

to be considerable and methods used for sampling endofauna and esti­

rn3ting productivity values differ widely, I do not think that the

available dnta are sufficient to draw a reliable and conclusive

biomass distribution map of the North Sea macrobenthos. Neverthe-

,.

•

l~EE, a ro~g~ a~:emp~ lS made to cet a~ i~press~c~ ab~~~ w~a~ ~s

kncw~ an6 t~ see wherc the gap~ are. Furthermorc, proauctivity

estimates will be reviewea, especially looking OD annual P/B

ratios and their variability.

Bl0MASS DISTRIBUTIO!~

Fig. 1 presents data about macrobenthic biomass (ash-free dry

weights, AFDW, per m2 ) according to several authors. Information

from investigations before the second world war was not taken into

account, as mostly rough total weights (including shells etc.) were

determined (e.g. BLEGVAD, 1922; HAG~mIER, 1925). Beyond this there

are the great differences in sarnpling gear,.by which comparison is

still more impeded.

Por the calculation of AFDW from dry tissue weights, 10 per cent

were taken as ashes; wet tissue weights were considered to comprise

10 per cent AFD~.

The map shows that there is relatively good knowledge about macro­

benthos in the southeastern and - more scattered - northwestern part

of the North Sea, whereas large areas of the central and ncrthern

North Sea and off the English coast are not covered. Since da ta from

intertidal and estuarine areas are even more variable than froffi

subtidal fauna, they are not included in Fig. 1. It is to stress,

however, that these areas as a whole would be included mainly in-2the category of ')8.0 9 AFmV'm (BEUKEfJl..A, 1975).

Subtidal areas of high biomass stocks belong chiefly to thc

infralittoral etage (GLEMAREC, 1973; see KINGSTOn & RACHOR, 1982):

the Germann Bight, the muddy bottom areas south of the Dogger Bank

and large parts of the Dogger Bank, nearshore Scottish arcas and

- as far as the few available results show - areas at thc north-

.western edge of the North Sea east and sauth of the Shetlands. Poar")

areas (especially with less than 1 9 AFEvi per ro~) are indicatcd in

the central and eastern part of thc northern North Sea, belongins

to the open sea etage (deeper than 100 roj.

,- .., -

A roug~ e5tirna~e o~ total bioffiass s~o=~ c~ Nort~ Sea ffiacro-

e~~ofauna results in 16 mille t wet tissue weigtt {1.f ~ill. t

;I~~: accordin9 to th€ following ~ab~la~lCr.:

Eta~e Per cent of North Se.::: area 1-.FD\\'· 17,- 2 'Iota::' A!"D'v\

~nfralit- 41 5 9 1 .025.000 ttoral

coasta1 28 ...9 420.000 t.:>

open sea 31 1 9 155.000 t

Total North Sea 1.600.000 t

This is the same stock as used in ANDERSEN's & URSIN's (1977)

North Sea model.

PRODUCTIO!~

There are great difficulties in presenting reasonable pro­

ductivity estimates of the North Sea macrofauna as a whole. Not

only species and co~~unities, but also distinct populations from

different areas and in different years exhibit varying annual

production performances, especially if growth and age structure

of the populations vary and if gamete production and growth of

the very young individua1s are not considered.

Table I is a su~~ary about what is known of sublittoral macro­

endofauna productivity in the North Sea proper. Annual P/B ratios 4twere found to be rather low in a 80 m deep mud area off the coast

of Northumberland (BUCffiM~AN & WAR~nCK, 1974: P/B = 0.44 for the

who1e rnacrofauna). HEIP et a1. (1982) give for an Abra alba

cornrnunity of the southern North Sea a P/B ratio of about 3, whereas

a poor Macoma cornrnunity is assurned to have a ratio of less than

0.5 ( GOVAERE et a1., 1980) .In the German Bight, annual P/B

ratios were found to be rather high in several populations of

different major taxa, fitting weIl into the known nurnbers between

1- and 5 for longer, respectively shorter lived species.

..

t

•

As proc~ction estimates 0: subli~tcral Nort~ Sea populations

an= cor.munities are scarce, estimates fronother cornparable marine

areas are to be considered. The most comprehensive compilation· of

relevant P/B.-data i5 given by ROBERTSO~;' (j9'79), who calculated a

regression equation for pooled data r€latin~ P!E 'anclifespan

(L) for rnacrobenthos from a variety ofphyla and marine habitats.

Table 11 surnmarizes ROBERTSON'S dataand gives new calculations

and comparison5 withthe North Sea valuesfrom Table. I. It. can be

seen that the addition of the German Bight estimates does not much

influence the equation of world-wide subtidal soft bottcm populations,

but, that the' addi tional .consideration ofthe BUCHANAN & \>;AR\>;IC}:

Northumberland estimates produces' 10w PjB-va1ues •

Information about lifespan of the relevant macrofauna populations

of different areas .of the North Seais even worse than that about

annual production. Therefore, a1lattempts to come to acceptable

estimates of North Sea macrobenthos production are of high uncertain­

ty. The foll?wing figures, taking into account a longer 1ifespan

for deeper-living populations, are to be regarded as very rough,

preliminary estimates:

Infralittoral Coastal Open sea etage Total

L 2.0 4.0 5.0 ca. 2-3

• P/B 2.5 1.0 0.7 ca. 2.0

P (MDW, 2.5 0.4 O. 1 3.0mil1. t)

DISCUSSION

Biomass and productivity of. sublittoral macrozoobenthos depend

on many factors, a~ong which are:

a. availabi1ity and composition of organic matter,as a rule related

with primary production in the euphotic zone, water depth ane

sediment grain size distribution;

b. population age structure, related with environmental stability,

predation pressure,reproduction bio10gy;

'_. ot:-,er ccr.rrl~ni-:y Frcper:'ies lü:e feedin:;: type do:r.inanccs,

relative importan=e o! msicfa~n2 and reicro-orga~isrns and

o! vagile epibenthcs.

Little is known about the relntive irnportance of all these

and other possible factors. The rough SkC7.chof bior.',ass distributior,

(Fig. 1) indicates higher productivity cf the shallow water fauna

of the infralittoral etage in the southern North Sea, especially

where.fine bottoIT deposits are prevailing. Information about the

central North Sea i5 almost lacking. In the northern North Sea

biomass seems te be. lew with the exceptibn cf the north western

edge where primary productivity cculd be high due to the influx ..

cf Atlantic water. Fishing intensity is not in contradiction to

the sketched biomassdistribution of macrozoobenthos in the

North Sea.

Considering STEELE's (~974) North Sea model, an annual macro­

zoobenthos production cf about 30.kcal.rn- 2 is required by demersal

fish. This is only acchievec by ta)~ing a relatively high macro­

fauna productivity (menn P/B ~bout 2) at a higher biomass than

STEELE assumed. The estimatcd biomass of this paper (1.6 mill. t

AFm~, which corrcsponds to 3.2 9 AFDN'rn-2==15 kcal'm- 2 ) is the

same stock as usee in .~JDERSEN's ane URSIN's (1977) North Sea model.

1I.I.II

I!II

II.,I

i!

tiII

\II

iI!

All these estimates are based on very limited data and are ,I~.

insufficient for understanding the North Sea ecosystem and its I

Ichanges. What is needed, are a It quas isynoptic map of biomass l

distribution" of the nacro-endofauna, production estirnates especially !i

of the offshore fauna of thc central and northern North Sea, and I

information about the v~riability 0: macrofauna production (annual \!and lang-term due to changes in climate, fish stocks, entrophication). jI

\

Ii

iI

IIII

- 7 -

'fable I. ....., ~ -)-1Estimates of annual product~on (p, in g A~Dw .~ -·a ),

annual turnover ratios (PIß) and lifespan CL, in years)of sublittoral North Sea macro-endofauna populations.

-.;Species p P/B L Locality, Depth Authority

.1r:uno trypane aulogaster, p 0.36 2.1 2 ? off Northumber- ßUCHAl\fAN ~

:ieteromastus filiforrnis,p 0.30 1.0 2-3 land, mud, 80 m ',-lA....'-t\JICK, 1974-

Jpiophanes kröyeri, p 0.20 1.4- 2 ? " "G'lycera rouxi, p 0.19 0.4- 5 " "Lumbrineris fragilis, p 0.08 1.3 3 11 11

:.Jnaetozone setosa, p 0.05 -1.3 2-3 11 11

"a ~itida, b 0.12 1.1 3 " 11

3=issopsis lyrifera, e 0.11 0.3 4- 11 "rJalocaris ::l3.candreae, c 0.14- 0.1 8.5 11 11

mean of studied2;orthumberland populations

totale0 r::untL.'1.i ty A 7LLI •

1.0 3.6

0.4

11

., 11

#'I ..... --I""; 1-,, /

~!";:-iO.d ~ t .:lI.,1·.),~ .;:

.~ '"-' '--

_-L~'~~CR ~ .3.~::.­

::::L, 1 :'3:

"

1 ;erman 3i~ht,

\3 3..:1.'::' , .:. :3 .::.1 .:/ -:J~r:lan 3ig~t,

:::.ud, c::;:rr3 :~erman 3i~ht,

i;::ud, 20-23 r:J.

? Ger~an 3igh'C,alud, 23:n

2? Gerrnan 3ight,~uddy sand, 35 ~

3.5 Geroan 3ight,sand, ''16 ::l

~.5 26 ::l

2.1

I! "<0+ _ ,-'

1.5

1.7

('. :"l..... ·73.14

1.35

2.'76

c

,::)

b

b

ra 'Ch.'-ce i ,

.. , , '-l_,~J.cU..l.a ~~ tL....osa,

;~l~ellus pellucidus,

:ellina rabula I,

:-.:e8:1. :)f 3tudied~err:J.~n 3i~ht ;opulations ? 0_." German Bight

'~ .... r­• -::;>

.., -.e. j 30uthern 3ight 1.1. ,

::.1 11 "

. .~(=_3~~:~J~3:.J -

. ..J :. -t 3.. _ "[ :.., 3. t ,"' =

- - ---- -- --------- -------------------------,--------------

",' : .•..... -

;..:~:'E::,.sE~~, F.? ~ UF:.SI!\, E. (1977;: J... r.r..:ltispecies exte:uöio:l

~~ tne BeJertcn and Holt theory 0: f~shing, with a=cou~ts.

oi phosphorus cireulation ane Frirnary production.

Danm. Fisk. - '00 Havunders. , ~J. S. -;, 319-435.~ -

- Meddr.

BE::!:E~..h, J.J. (19i5): Biologische produktie in zee. In: VERVELDE.,

: G.J. (Ed.): Produktie in.biclogis6he systemen. - PnDoc,

Wageningen, 243-262.,

BLEGVAD, H. (1922): Animal communities in the southernNorth Sea.

- Proe. zool.'Soc. London 1922, 27-32.

BUCHANM , J. B., KINGSTON , P. F. & SHEADER, M. ' (1974): Longterm

populations trends of the benthicmacrofauna in,the offshore

mud of the Northumberland coast. - J. mare biol. Ass. U.K. ~;

785-795.

•BUCHANA.~, J.B. Er v..'ARWICK, R.M. (1974>: An estimate,of benthic rnacro­

faunal production in theoffshore mud of the Northumberland

coast. - J. mare biol. Ass. D.K. ~, 197-222.

CREUTZBERG, F., WAPENAAR, P., DUlNEVELD, G. & LOPEZ, N., (1982):

Distribution and density of the benthic fauna in the southern

North Sea in relation to bottom characteiisti~sandhydrographie

conditions. - lCES Symposium on biologicalproductivity of ,

continental shelves in the temperate zone of the North Atlantic,

Kiel 1982. No. ~, 1-17.

GLEMAREC, M. (1973): The benthic cornmun'ities of the European' con- .,'

tinental north Atlantic continental shelf. ~ Oceanogr. mare

BioI., Ann. Rev. 11, 263-289.

GOVAERE, J. C. R. (1980): Benthic communi ties in the south~~n Bight

of the North Sea and their use in ecological ~onit6ring~.~'

- Helgoländer .Meeresunters. ~, 507-521. .~.

HAGMEIER, A. (1925): Vorläufiger Bericht über die vorbereitenden

Untersuchungen der Bodenfauna der Deutschen Bucht mit dem

Petersen-Bodengreifer. - Ber. dt. 'wiss. Kommn. Meeresforsch . ,

N.F • .1., 247-272.

HEIP, C., HE~mN, R. & VINCX, M. (1982): Variability and productivity

of meiobenthos in the Southern Bightof the North Sea. - lCES

Symp., Kiel 1982, No. 20, 1-8.

,•

•

- lCES c.:·:. i9&2/L: 4~.

KlRKEGAf.P~, ~.E. (1969): A quantita~ive investi9ation of the central

North Sea Pclvchaeta. - Spolia zool. Mus. hann. 29, 1-285.~ -

KLEIN, G., RACHOR, E. & GERLACH, S~J.•. (1975): Dynamics ane producti­

vity of two populations of the benthic tube-dwellinq amphipod

Ampelisca brevicornis in Helgoland Bight. - Ophelia li, 139-159.

!·lcINTYRE, A.D. (1975): The benthos of the western North Sea. -

lCES Symposium on the changes in the ~orth Sea fisk stocks

and their causes. Aarhus.

McINTYRE, A.D. (1978): The benthos of the western North Sea. ­

RapF. P.-v. Reun. Cons. int. Explor. Mer.172, 405-417.

PETERSEN, G.H. (1977): The density, biomass and origin ofthe

bivalves of the central North Sea. - Meddr. Da~~. Fisk. ­

og Havunders. 2, 221-273.

RACHOR, E. (J976): Structure, dynrnaics andproductivity of a

population of Nucula nitidosa (Bivalvia, Protobranchiata)

in the German Bight. - Ber. dt. wisse Kornrnn. Meeresforsch.

24, 296-331.

RACHOR, E. & B&~TEL, S. (1981): Occurrence and ecological signi­

ficance of the spoon-worm Echiurus echiurus inthe German Bight.

- Veröff. Inst. Meeresforsch. Bremerh. ~, 71-88.

RACHOR, E. & SALZvffiDEL, H. (1976): Studies on population dynarnics

and productivity of some bivalves in the German Bight. - Proc •

10th Europ. Symp. Mer. Biol. Ostend, Belgium, Vol. 2, 575-588.

RACHOR, E., ARNTZ, W.E., RUMOHR, H. & MANTAU, R.-H. (in press):

Seasonal and long-term population dynamics in Diastylis rathkei

(Crustacea: Cmnacea) of Kiel.Bay and German Bight. - Netherlands

J. Sea Res.

ROBERTSON, A.J. (1979): The relationship between annual production:

biomass ratios and lifespans for marine macrobenthos. - Decologia

(Berl.) 38, 193-202.

SALZ\iEDEL, H. (1980): Energy budgets for two populations of the

bivalve Tellina fabula in the German Bight. - Veröff.lnst.

Meeresforsch. Bremerh. ~, 257-287.

r· _.,I:,!

STEELE, J.B. (1967): Notes on some theoretical problems in pro­

duction ecology. - Mem. Ist. Ital. Idrobiol. ~, (suppl.),383-398. •

STEELE, J.B. (1974): The structure of marine ecosytems. - Blackwell,•Oxford. 128 pp.

URSIN, E. (j960): A quantitative investigation of the echinoderm

fauna of the central North Sea. - Meddr. Danm. Fisk. - og

Havunders. N.S. 11, Nr. 24, 3-204.- ,

Fig. 1: Rough sketch of North Sea macro-endofauna biomassdistribution.

Information from different North Sea areas, aceording to:

Northern North Sea: Eleft., pers. comm., Kingston pers.

COmi'TI., Hartwig, pers. eomm., Mclntyre (1978)i

Central North Sea (ineI. Dogger Bank): Ursin (1960),

Kirkegaard (1969), Buehanan & Warwiek (1974),Petersen (1977}i

South Western North Sea: Govaere et al. (1980),

Creutzberg et al. (1982)j

German Bight: Salzwedel & Raehor (in prep.).

•

:;

,

57

Sc

55

J

5~

"51

-' ~.1

I

I. i

('

,... ..i

I41

I I39 40

I t37 38

I36

-1.1-8.0

I4 35

1.1-_.

- .--

I 127 ~

.::>

I5 2624 .---:..------------------------------------

t .....

> S.O

, (~;" .. 9

TalJle II: EstiIoates of lifesttt (L), mean annual P/B ratios'end calcu1ated P/B ratios

for different lifespans of populations from differ~llt areas, according to

ROBERTSON, 1979, and"new calculated regression equations.

~--~-I

according tooriginal population

data

P/B according to the givenregression equations with

L (years)=

Mean L(years)

MeanP/B

1 2 3 4 5

a. world-wide(intertidal and subtidal)HOBEHTSON, 1979

U. würld-wide(subtidal soft bottom)from ROUERTSON, 1979

c. world-wide (B.) plusactditiona1 values of'l'dble 1

LI. Nut'th Sea,vdlues of Table I

E. world-wide (B.) plusGerman Bight, va1ues of'l'alJle I

4

2.3

2.8

3.3

2.5

2.5

3.0

2.3

1.5

2.7

4.6 2.8 2.1 1.7 1.4

10g10 P/B=0.66-0.726 10g1oL

4.6 2.8 2.0 1.7 1.4

10g10 P/B=0.66-0.729 10g1oL

5.3 2.3 1.4 1.0 0.7

10g10 P/B=0.73-1.24 10g10L

4.7 1.8 1.0 0.7 0.5

10g10

P/B=0.674-1.377 10g10L

4.6 2.7 1.9 1.5 1.3

10g10 P/B=0.663-0.792 10g10L