Meiobenthos of the Deep Northeast Atlantic
M.
Vincx,'
B.J. Bett,2 A Dinet,3 T. Ferrero,4 AJ. Gooday,2 P.J.D.
Lambshead,4 O. Pfannkuche,6 T. Soltwedel5 and A Vanreusel'
lUniversity of Gent, Zoology Institute, Marine Biology Section, KL.
Ledeganckstraat 35, B 9000 Gent, Belgium..
2Institute of Oceanographic Sciences Deacon Laboratory, Brook Road,
Wormley, Godalming, Surrey GU8.5UB, UK.
3
Laboratoire Arago, F 666.50 Banyuls sur Mer, France..
4Department of Zoology, The Natural History Museum, Cromwell Road,
London SW7.5BD, UK..
5Institutfur Hydrobiologie und Fischereiwissenschajt, Universitiit
Hamburg, Zeiseweg 9, 2276.5, Germany.
6Forschungzentrumfur Marine Geowissenschaften, GEO MAR Abt.
Marine Umweltgeologie, Universitiit Kiel, Wischhofstr.. 1-3, Kiel, Germany
1.. Introduction
,
2
2.. Meiobenthos in the Northeast Atlantic
,
4
2..1.. Physiographic setting
,
4
2..2.. Historical background.. .. .. ...... .. .. .... . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .... .. .. .. .... .. .. .. .. .. .. .. .. . .. .. 5
2..3. Sampling areas .. ..
,
6
2..4.. Collection and processing
,
6
3.. Environmental Variables. .. .. .. .. .. .. .. .. .. ... .. .. .. .. . .. .... .. . . .. .. .. ...... .. .. . .. .. .. .. .. .. .. .... . 16
3.1.. Sediment type .. .. .... .. .. .. .. ...... .. .. .. . .. .. .. . .. .... .. .. . .. .. .. .. .... .. .. .. . .. .. .. .. .. .. 16
3..2.. Oxygen ..................... ......... ............................... ........................ .. 17
3..3..Food supply.., .........., .............. 17
3,.4.. Deep Bottom Water masses ,.. ,
20
3..5.. Near-bottom currents ,. 21
4.. Horizontal Spatial Patterns
,
21
4..1.. Bathymetric trends .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. . .. .. .. .. 22
4..2.. latitudinal trends .................. ................................... ... .......... 35
4.3.. Multivariate analysis 41
4..4.. Comparison with other regions 44
4..5.. Patterns at different taxonomic levels ..,. ....... ......... ......... .. 46
4.6.. Small-scale spatial patterns. . ..... ............................. ...................... 52
5.. Vertical Spatial Patterns , ....... ... ... ......... 53
5..1. Suprabenthic microhabitats 53
5..2..Vertical distribution within the sediment. ...................................... 53
ADVANCES IN MARINE BIOL OGY VOL 30
ISBN 0-12-m6130-8
Copyright @
1994 A~ademic Pre<s Limited
All rights of reproduction in any fOlm reselved
2 M. VINCX ET AL
6. Temporal Patterns
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7. Summary and Conclusions"
ACknowledgements
References
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1. INTRODUCTION
Although the first ecological investigations on the meiobenthic communi-
ties of the deep northeast Atlantic were carried out 20 years ago (Thiel,
1972b), it is only recently (1990) that co-operative research has been
initiated by the European Community under the EC MAST I (Marine
Science and Technology I 1990-1992) programme: "Natural variability
and the prediction of change in marine benthic ecosystems". The general
objectives of this EC programme, which continues in a MAST II project
(1993-1996), are (i) to describe the natural structure and variability of
offshore benthic populations in the northeast Atlantic, (ii) to relate the
structure and variability to processes in the physical, chemical and
biological environment, (Hi) to describe the trophic network in the
benthic boundary layer and to estimate the organic carbon flux through
the deep-sea benthic ecosystem, and (iv) to attempt to predict the
changes that are likely to be associated with natural and anthropogenic
disturbance. An important component of benthic ecosystems, particularly
in the deep sea (Thiel, 1975, 1983), is the meiobenthos, generally
considered to include organisms in the size range 31-500 JAm. The
combined efforts of five laboratories in four of the countries participating
in the MAST project have highlighted the gaps that exist in our
knowledge of the meiobenthos of the northeast Atlantic and have
prompted this review. Our main purpose is to summarize literature data
and new results from an area lying between 15°N and 53°N and extending
from the continental margin of western Europe and northwest Africa to
the Mid-Atlantic Ridge (Figure I).
Since the first quantitative investigation by Wigley and McIntyre
(1964), data on deep-sea meiobenthos have been gathered from all
oceans and attempts made to relate the broad geographical patterns
observed to various environmental factors" On a planetary scale, one of
the major environmental gradients is created by the slope of the ocean
floor, a gradient which has important effects on benthic communities. As
in the case of macrobenthos (Lampitt et al., 1986), the data available on
meiobenthic densities in deep-sea environments also show trends which
can be related to the amount and nature of organic matter reaching the
seafloor (Thiel, 1983; Shirayama, 1983; Pfannkuche, 1985; Pfannkuche
and Thiel, 1987). The distribution patterns of deep-sea organisms are
MEIOBENTHOS OF THE DEEP NORTHEAST ATLANTIC
3
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Figure 1 The northeast Atlantic showing the positions of the 30 sampling areas..
4
M. VINCX ET AL.
influenced by other variables such as sediment type, bottom currents and
bottom water masses. Local topographic and hydrodynamic features,
such as canyons, seamounts and deep boundary currents, are also
important. In addition, the ever-improving resolution of the physical
structure of the deep sea, and technical advances in sampling gear and
surface navigation, have permitted biologists to address small-scale
variability, on scales ranging from centimetres to kilometres.
In this review we consider first the nature and scope of meiofaunal
research in the northeast Atlantic and then discuss the environmental
parameters which are believed to influence meiofaunal organisms. Next,
we discuss the various types and scales of pattern observed among
meiofaunal populations within our study area, progressing from the
large-scale bathymetric and latitudinal trends and then to small-scale
horizontal patterns within particular areas. Faunal densities and faunal
composition are considered separately and compared with data from
other regions. Finally, we discuss the distribution of meiofauna within
sediment profiles and the temporal variability of populations. Our
approach dif~ers, therefore, from that adopted in Tietjen's (1992) recent
review of deep-sea meiofauna which focused mainly on abundance and
biomass data from different oceans and on the relationship between the
biomass of the meiofauna and that of other faunal components.
2. MEIOBENTHOS IN THE NORTHEAST ATLANTIC
2.1. Physiographic Setting
The area under investigation consists of a series of deep basins separated
by ridges. Basin depth tends to increase from north to south, with depths
in excess of 5000 m occurring in basins to the west and northwest of the
Cape Verde Islands.
A number of physiographic zones can be recognized within this region:
continental shelf, continental slope, continental rise, abyssal apron and
abyssal plain (Emery and Uchupi, 1984; see also Rona, 1980; Udintsev et
al., 1989-1990). Secondary features include the zone of abyssal hills
which separates the continental rise from the Mid-Atlantic Ridge and a
number of major seamounts and volcanic islands. Notable aspects include
the abyssal aprons (sediment masses deposited by geostrophic bottom
currents) of the northwest African margin and around and to the west of
the Rockall Trough (Hill, 1987) and the series of abyssal plains (from
north to south the Porcupine, Biscay, Iberian, Tagus, Horseshoe, Seine,
Madeira, Cape Verde, Gambia) which lie seaward of the continental rise.
MEIOBENTHOS OF THE DEEP NORTHEAST ATLANTIC
5
The area consists of different biogeochemical provinces of plankton
productivity, such as upwelling (NW-Africa), trade wind regime, subtro-
pical gyre, etc., which are of great consequence to the supply of food to
the seabed and ultimately for the sediment type where pelagic sedimenta-
tion prevails.
2.2. Historical Background
The study of some meiobenthic taxa, particularly foraminifera, living in
this region has a long history (e.g.. Parker & Jones, 1856; Brady, 1884).
However, sampling for meiobenthos was incidental until the 1960s and
1970s when the first quantitative meiobenthic samples were collected
from the German research vessel Meteor; numerical abundance data from
these samples were published by Thiel (1972a, b, 1975, 1978, 1983) and
Rachor (1975). Another quantitative investigation which included the
meiobenthos was the BIOGAS programme, carried out during the 1970s
in the Bay of Biscay (Dinet and Vivier, 1977; see also Dinet et al., 1985).
More recent papers devoted partly or exclusively to the meiobenthos are
those of Pfannkuche et al. (1990), Pfannkuche (1992, 1993b) in the
BIOTRANS area and Rutgers van del' Loeff and Lavaleye (1986) at the
DORA site.
Other studies have focused on particular aspects of the meiobenthos.
Some authors have considered just the nematodes (Riemann, 1974; Dinet
and Vivier, 1979, 1981). Desbruyeres et al. (1985) evaluated meiobenthic
taxa as part of a recolonization experiment in the Bay of Biscay. Another
approach has been to look for correlations between meiobenthic densities
and environmental parameters such as bathymetric depth and the amount
of organic matter in the sediment (Thiel, 1979b, 1983; Dinet and
Khripounoff, 1980; Sibuet et al., 1989; Vanreusel et al., 1992). Although
taxonomic studies of deep-sea meiobenthos are fairly rare in our area,
some new taxa have been described among the harpacticoids (Bodin,
1968; Dinet 1977), nematodes (Decraemer, 1983), ostracods (Kornicker,
1989, van Harten, 1990) and tardigrades (Renaud-Mornant, 1989). Some
of these investigations have dealt exclusively with the metazoans while
others have included foraminifera within the scope of the meiobenthos.
Several papers by Gooday (1986a, b, 1988), Gooday and Lambshead
(1989), Lambshead and Gooday (1990) have described the foraminiferal
meiobenthos in the northeast Atlantic. Gooday and Turley (1990)
presented some additional data and Gooday (1990) established anew,
ecologically important allogromiid species. The numerous geologically
orientated studies of modern deep-sea foraminifera in the northwest
Atlantic (Murray, 1991) deal only with the hard-shelled taxa and are not
considered further.