Yi#iOLOEY
ln1tnom
ELSEVIER
Marine Micropaleontology 25 ( 1995) 169-I 86
Benthic foraminiferal distribution and recolonization of formerly
anoxic environments in Dramrnensfjord, southern Norway
E. Alve
Received 4 August 1994; accepted after revision 10 January 1995
Abstract
Investigations of living (stained) benthic foraminifera in the surface (O-l cm) sediments along a depth transect in Drammensfjord, southern Norway, have been carried out on samples collected in 1984 and during all four seasons in 1988. The
transect runs through strongly variable environments from a well oxygenated, brackish surface layer to anoxic waters of slightly
less than normal marine salinity. The objectives were to study foraminiferal recolonization patterns after a prolonged period
( > 5 years) of nearly permanent anoxic bottom water conditions in the lower parts of the transect, the seasonal stability of the
assemblages after recolonization, and interspecific tolerances to various environmental parameters (i.e., temperature, salinity,
dissolved oxygen concentration, water depth). When the redox-boundary was at its shallowest position in the water column
(30-35 m water depth; salinity 29-30%0), Ammodiscus? gullmarensis was dominant adjacent to the anoxic areas. This represents
the first record of agglutinated dominated assemblages bordering anoxic environments. It took more than one year after reaeration
before the areas, where anoxic conditions had prevailed for more than five years, became suitable for colonization. By 1988, the
foraminiferal standing crop had more than doubled in areas influenced by the transitional water masses and living (stained)
individuals were present down to the redox-boundary. Additionally, four species, which were not found along the transect in
1984, had been introduced. These immigrants had probably been transported into the area in suspension from the south.
Stainfirthiafitsiformis was the first and most successful species to recolonize the formerly anoxic areas and it showed exceptionally high densities in samples collected a few meters above the redox-boundary. After recolonization, all species showed a
distinct depth succession which, for most of them, prevailed throughout the year. Possible lack of seasonal population fluctuations
in several species is thought to be due to a permanently plentiful food supply. The nine abundant species have been ranked in
accordance with their interspecific tolerance to increasing euryhaline and eurythermal environmental conditions.
1. Introduction
Paleoenvironmental
reconstructions
based
on
foraminiferal assemblages are primarily dependent on
our knowledge about their modern ecology. We know,
however, that many ancient environmental
settings do
not have any modern analogues, as the environmental
conditions have changed through time. In order to
improve our prospects of making paleoenvironmental
reconstructions,
every possible modern marine envi0377-8398/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved
SSDIO377-8398(95)00007-O
ronment
should be investigated.
Drammensfjord,
southern Norway, represents a unique, temperate environment, where the intermediate
water masses are
trapped between a well oxygenated, brackish surfacewater layer and nearly permanent anoxic bottom water
with slightly lower than normal marine salinity. The
oxygen conditions in the fjord have declined over the
last couple of centuries due to discharges of organic
material. However, reduced organic input over the last
ten to fifteen years has caused a deepening of the gen-
E. Alve /Marine Micropaleontology 25 (1995) 169-186
170
era1 position of the redox boundary in the water masses
and some of the formerly anoxic areas of the fjord
bottom have been reoxygenated (Alve, 1990, 1991).
These unique conditions warrant a study of the benthic
foraminiferal distributions
along an environmentally
complex depth transect. Samples were collected along
a depth transect when the redox boundary was approximately at its shallowest position (1984) and, four
years later ( 1988), when it had been lowered by about
20 m. This sampling has enabled documentation of the
impact of improved oxygen conditions on the foraminiferal assemblages and of recolonization patterns in
the formerly anoxic areas. Samples were collected during four seasons (February, May, August, and October) in 1988 in order to study the distributional stability
of the populations of benthic foraminiferal species after
reaeration.
Previous investigations of benthic foraminiferal colonization due to improved environmental
conditions
are sparse (e.g., Cato et al., 1980; Finger and Lipps,
1981; Schafer, 1982; Schafer et al., 1991) but a closer
understanding
of recolonization
patterns and mechanisms will enhance our possibilities of interpreting sudden occurrences of foraminifera
in the geological
record, for instance in connection with sapropels.
2. Investigation
area
2.1. Environmental
characteristics
Drammensfjord is a part of the silled Oslofjord system, southern Norway. It is separated into an inner (20
km long, <3 km wide) and an outer (10 km) part by
a sill at 10 m water depth. The bottom topography
shows a gradually increasing water depth from around
10 m in the north to a maximum of 124 m in the southern
part, just inside the sill. The water masses show a typical
estuarine stratification. Fresh water, from the River
Drammen, enters the fjord in the north, close to the city
of Drammen, at a rate of about 290 m3/s (Magnusson
and NZS, 1986) and mixes with the marine fjord water.
The resulting brackish surface water (seasonal ranges:
salinity < 1 to about 15%0, temperature < 1” to about
20°C)) with a vertical thickness generally equal to sill
depth ( 10 m), flows southwards and out of the fjord
through the narrow sill area (minimum width about
150 m) .A pronounced halocline separates the brackish
surface layer (B.S.L.) from a transitional layer (T.L.)
which extends down to about 35 m water depth where
the salinity is about 30%0. The temperature varies seasonally from about 4” to 14°C in the upper parts of the
transitional layer but the range decreases with increasing water depth and only small annual variations (temperature: 6.2”-8.O”C; salinity: 30.0-31.5%0) occur in
the stable deep water (S.D.W.) . Because of the density
gradient at sill depth, the shallow position of the sill,
and low vertical mixing of the water masses, frequent
deep water renewals are prevented. Such renewals only
occur once every 3-5 years, and are mainly restricted
to November-May
(Magnusson and NZSS, 1986).
Due to these geomorphological and hydrographical
characteristics, Drammensfjord has a natural potential
for developing anoxic conditions in its deeper parts;
during the last one thousand years, well-oxygenated
conditions have not prevailed for long periods (Alve,
1991). Consequently,
the oxygen conditions in the
deeper areas are sensitive to organic matter enrichment
and increased, human-induced
organic flux (initially
effluents from saw mills, later from paper and pulp
industries, agricultural drainage and domestic sewage)
over the last 130-140 years has raised the position of
the redox cline.
During the first half of the 197Os, most of the paper
industry closed down, but the organic material which
had accumulated in the sediments continued to affect
the oxygen balance for many years. Additionally, discharges of municipal effluents increased since the
1960s and the agricultural contribution remained significant. All these factors contributed to the development of severe oxygen-limited
conditions in 1977,
1978, and 1982 withanoxiabelow
30-35 m waterdepth
but a slight increase in dissolved oxygen occurred in
1983-1984 (Magnusson
and Nass, 1986). Further
increase was reported in 1987-1988 with anoxic conditions restricted to areas below about 35 m water depth
in the northern, and below about 60 m in the southern
parts of the fjord (Alve, 1990). In 1988, the total
organic carbon content in the middle and southern parts
of the fjord was generally between 1 and 2% in the
surface sediments associated with the B.S.L. and
between 2 and 3% at greater water depths (Alve,
1990). Furthermore, the sediments along the profile
investigated in this study had a sand content of lO-60%
(decreasing with increasing water depth) in areas
underlain by the B.S.L. At greater depths it was muddy
E. Alve /Marine Micropaleontology 25 (1995) 169-186
with < 2% sand below about 30 m. For further details
about the environmental
conditions, see Alve ( 1990,
1991).
2.2. Previous foraminiferal investigations
More than one thousand years ago, Drarnmensfjord
was characterized
by normal marine foraminiferal
assemblages resembling those of the present Oslofjord
(Alve, 1991). Due to climatic changes and isostatic
elevation,
deep-water
renewals
were gradually
impeded and the changing environmental
conditions
gave rise to low diversity benthic foraminiferal assemblages dominated by agglutinated species. Since the
middle of the last century, the increased input of organic
material and subsequent shoaling of the redox boundary limited the distribution of benthic forarninifera to
successively shallower areas. In 1987-1988, the following distribution pattern of total (stained + empty
tests) assemblages was recognized along six depth profiles from different parts of the fiord ( Alve, 1990) : the
B.S.L. was strongly dominated by a low diversity Mliammina fusca assemblage. In the upper part of the
transitional layer, Astrammina sphaerica and Eggerelloides scabrus were dominant in the northern and
southern parts, respectively. Spiroplectammina biformis was frequent ( >5% of total assemblage) at all
stations below the B.S.L., except in the samples immediately above the redox boundary. Ammodiscus? gullmarensis was particularly abundant in the lower parts
of the transitional layer, whereas Stainforth fisiformis strongly dominated the sediments in the immediate
vicinity of the redox boundary in the middle and southern parts. S. fusiformis was not present in the northern
area probably because the shallow position of the redox
boundary restricted the distribution of oxygenated surface sediments to areas where the salinity was too low
for its maintenance
(i.e., less than about 30%0). No
foraminifera were found below the B.S.L. in the northwest and below 30 m in the northeast river influenced
areas.
3. Material and methods
The present investigation is based on 104 surface
sediment samples (O-l cm) collected by means of a
light gravity corer (6.7 cm inner diameter) during 5
171
cruises along a depth transect (2-51 m water depth)
from the middle part of the eastern side of Drammensfjord, southern Norway (for a map of the area, see
Alve, 1990). Nine samples were collected on May 15,
1984, and the rest were collected during four seasons
in 1988: 25 on February 18; 25 on May 24; 24 on
August 4; 21 on October 18. Sampling in February
1989 was prevented by ice coverage.
The salinity and temperature were measured every
meter from 0 to 10 m water depth, every second meter
from 10 to 20 m, and every fifth meter from 20 to 50m
by means of a Salinity Temperature Bridge, type M.C.5
during all cruises, except in May, 1988 (due to logistical problems). For most stations during the 1988
cruises, 250 ml of water immediately overlying the
sediment in the core liner (in the range O-1 5 cm above
the sediment water interface) was transferred to glass
bottles for standard Winkler titrations. At each station,
the surface O-l cm of sediment was preserved in 70%
alcohol for foraminiferal analysis.
In the laboratory, the samples were stained with rose
Bengal for about 24 hours, heated to about 70°C for 20
min, dried at 50°C weighed and washed through 500,
250, 125 and 63 pm sieves. Each fraction was weighed
and the foraminifera in the > 125 pm fraction were
floated in C2C14. Previous to flotation, the samples were
carefully dry sieved through a 500 pm sieve in order
to separate material held together by organic matter.
Only the surface O-l cm of sediment was used in
order to avoid, as much as possible, the wood fibres
from the pulp and paper industries at greater sediment
depths. For the same reason, the > 125 pm fraction
was used for the foraminiferal analysis.
All abundance data refer to the number of stained
individuals recorded in each sample (i.e., in 35 cm3 of
wet sediment) and only species with an abundance of
5 stained individuals or more in at least 5 samples are
discussed. No diversity calculations have been carried
out because most samples had too few individuals
( < 100) to give significant values. Therefore, reference is only made to the number of species recorded in
each sample.
4. Results
4.1. Water masses
Except for the February temperature values, and an
exceptionally deep position of the halocline in August,
E. Ah/Marine
172
Temperature
Salinity (Y&
5
0
-+-
10
1s
20
Feb.18
-
Micropaleontology 25 (1995) 169-186
25
30
0
2
‘.+..
May15
4
6
8
d-
Aug4
Dissolved oxygen (ml/l)
(“C)
10
12
14
2
16
Oct. 18
4
6
8
-+-
Feb. 18
..+..
Aug4
-
May 24
-
Oct. 18
10
Fig. I. Salinity (A), temperature (B), and dissolved oxygen concentration (C) along the investigated profile. All measurements are from 1988,
except the May 15 salinity and temperature data, which were collected in 1984.
Table I
Ranges of water depth, salinity, and temperature for important species. Range I = maximum range of occurrence; Range II = range within which
the absolute abundance of the species is 2 10 individuals per 35 cm3. The arrow indicates the successive, increasing relative tolerance of the
different species to increasing euryhaline and eurythermal conditions. Data based on average values at similar depths from two stations in
Drammensfjord measured during 10 cruises between May 6 and November 24, 1982 (NIVA data) and on the author’s measurements along the
investigated transect during sample collection in May, 1984, and in February, August, and October, 1988
Wafer depth (m)
I
Range
II
I
Salinity (%)
II
Tcmperaturc (“C)
I
II
M. fusca
2
11
3
8
0.1-25.0
0.1-22.1
0.6-22.6
0.6-22.2
E. albiumbilicatum
5
46
7
11
0.1-31.5
0.2-25.0
1.6-18.0
3.0-16.0
7
44
a
17
0.2-31.5
0.2-28.1
3.0-16.0
3.3-15.6
A. cads
E. scabrus
11
36
11
12
12.8-31.5
12.8-25.9
4.0-15.5
4.0-15.5
IO
40
12
30
6.0-31.5
16.3-31.5
3.8-15.4
4.1-14.8
S, biformis
12
48
14 - 44
16.3-31.5
19.6-31.5
4.1-13.9
4.4-13.8
A.? gullmarcnsis
14 _ 42
15 - 38
19.6-31.5
20.7-31.5
4.4-13.8
4.6-13.1
A. glomeratum
15 - 51
18 - 38
20.7-31.5
23.1-31.5
4.6-13.1
5.0-12.7
S. fusiformis
23 * 51
32 - 48
26.3-31.5
30.1-31.5
5.4-11.2
6.1- 7.0
E. excavatum
the salinity and temperature data for each sampling
event (Fig. 1A and B) fall within the ranges measured
by the Norwegian
Institute
for Water Research
(NIVA) between May 6 and November 24, 1982
(NIVA data from Jan Magnusson) . Table 1 gives maximum ranges in temperature and salinity for selected
water depth intervals based on the two above mentioned
sources. The dissolved oxygen concentrations showed
similar patterns in February, August, and October,
1988, with gradually decreasing values from about 8
ml/l at 2 m to 0.0 ml/l at 50 m water depth in February
and to 0.1 and 0.2 ml/l at 5 1 m in August and October
E. Alve /Marine Micropaleontology 25 (1995) 169-186
Total no. stained / 35 cm3
Total
no.
173
stained/35 cm3 1
3s
150 ;g
100
1
I,,
I,
I
k
I,,
V)
.
May, 1988
B.S.L.
:
,
T.L.
40-
,S.D.W.
45
0
2
4
6
6
1012
0
No. of species
I
2
I
4
I
6
I
a
I
10
I
12
I4
No. of species
Fig. 2. Total stained abundance (no. per 35 cm3, solid line) and number of species (stippled line) recorded in May 1984 and May 1988 samples.
Note the scale difference between the upper x-axes. B.S.L. = Brackish surface layer; T.L. = Transitional layer; S.D.W. = Stable deep water.
respectively (Fig. 1C). In May, the values were somewhat higher and decreased from around 9 ml/l at depths
shallower than 8 m, to 3.1 ml/l at 17 m and remained
relatively constant at around 3 ml/l down to 38 m. The
concentration then decreased to 1.1 ml/l at 46 m and
remained at this level down to 50 m water depth.
4.2. Surface sediments
In 1984, the surface sediments were light greyish
brown to brown down to 34 m water depth. At 40 m,
the sediments were greyish-black with a brown surface
veneer and at depths greater than 45 m, they were black
and had a soupy consistence. Approximately the same
pattern was observed during all sampling events in
1988, except that the brown veneer extended down to
47 m in August, and in October, clumps of bright
orange-red sediments were present between 36 and 42
m water depth.
4.3. Foraminiferal diversity and abundance
May 1984
Stained foraminifera were recorded down to 30 m
water depth but only 1 or 2 species occurred at most
stations (Fig. 2; Appendix 1) . A maximum of 6 species
were found at 24 m. The samples were strongly dominated by agglutinated taxa and calcareous forms were
only present between 14 and 24 m, where they made
up 2-30% of the stained assemblages. Total abundance
of stained individuals per 35 cm3 decreased from 28 at
the shallowest station to a minimum of 3 at the border
between the B.S.L. and the transitional layer. Just
below this, at 14 m water depth, the abundance rose to
a maximum value of 48 and then gradually decreased
to 0 at 34 m. Miliamminafusca
was most abundant in
areas influenced by the B.S.L. (Fig. 3). At greater
water depths, Ammotium cassis, Eggerelloides scabrus, and Ammodiscus? gullmarensis showed succes-
E. Alve /Marine
Stained / 35 cm3
0
0’
10
’
’
20
’
’
30
’
25 (199.5) 169-186
Stained/35
Stained / 35 cm3
40
’
Micropaleontology
50 0
10
20
30
40
0
10
20
cm3
30
40
1 $ 3
EJo@
’
May, 1984
5
&
*-
B.S.L
I
: /
35
40
45
/
L
+-
M.fusca
-
A.cassis
c..
T.L.
-
A.
*.
E. excavatum
cassis
;.D.W
E. excavatum
- * - E. scabrur
d
50
A.? gullmarensis
d
A.? ~uharmsis
Fig. 3. Numerical density (no. per 35 cm3) of abundant stained species in May 1984 and May 1988. New occurrences in 1988 are shown in the
right hand diagram. For-water mass codes, see Fig. 2.
sively deeper maxima in areas bathed in the transitional
water masses. The only common calcareous species
was Elphidium excauatum in samples dominated by E.
scabrus and A.? gullmarensis.
1988
Stained foraminifera were recorded down to about
50 m water depth on all sampling events (Fig. 4;
Appendix 1) . The number of species was still low in
the B.S.L (generally < 4). In the transitional layer, it
was generally between 6 and 10, with occasional maxima of 13. At greater water depths, the values fell gradually towards the redox-boundary, but the decrease was
more sudden in May than during the other sampling
events. Agglutinated forms still dominated areas influenced by the B.S.L. However, during all sampling
events, calcareous forms dominated in some samples
at the boundary between the B.S.L. and the transitional
layer (Fig. 4). During all seasons, the middle and lower
parts of the transitional layer were completely dominated by agglutinated forms (generally > 75%),
whereas their relative proportions at greater water
depths were strongly reduced (generally < 30%). In
May, agglutinated taxa made up < 2% of the assemblages below 36 m.
The abundance in February, May, and August
showed comparable patterns of distribution, whereas
the October samples generally had somewhat lower
values except in the deeper parts of the profile, between
40 and 45 m depth. During all four seasons, the lowest
abundances (except below 48 m) were recorded in
connection with the B.S.L., with < 20 individuals per
35 cm3. In the transitional layer (down to 35 m) , the
abundance in February, May, and August ranged from
E. Alve /Marine Micropaleontology 25 (1995) 169-186
Total no. stained / 35 cm3
0
O!
50
I
150
100
t
1
-+
175
% Agglutinated
:
10
20
40
60
No. of species
80
100
2
4
6
8
10
I @%
r”
12
I,@
18Feb.
B.S.L.
;.D.W.
-Fig. 4. Depth distribution of total number of stained foraminifera per 35 cm3 wet sediment, relative abundance of agglutinated tests, and number
of species during four sampling events in 1988. For water mass codes, see Fig. 2.
13 to 140 per 35 cm3 (average 69, n = 29). In October
it ranged from 17 to 73 per 35 cm3 (average 40, n = 7).
Maximum abundances
were recorded in February,
August, and October between 35 and 48 m water depth
(range 13-298 per 35 cm3, average 93, n = 23). In
May, the maximum abundance in this depth range was
63 individuals per 35 cm3 at 41 m, and below 44 m it
never exceeded 4 individuals per 35 cm3. Below 48 m,
the abundance was <4 individuals per 35 cm3 at all
sampling events. The number of species showed minimum values of 1 to 2 in the B.S.L. and close to the
redox boundary. Maximum values between 10 and 13
were only recorded in the transitional layer. This pattern was fairly stable through all seasons.
Nine foraminiferal species, including 4 new occurrences (right hand diagram in Fig. 3) compared to
1984, were observed with populations of 2 5 individuals in at least 5 samples (Fig. 5). During all sampling
events, population peak abundances occurred within a
specific depth range characteristic of each species. Miliammina jkca,
restricted to areas influenced by the
B.S.L., had minimum abundances in October. Elphidium albiumbilicatum,
with peaks at the boundary
between the B.S.L. and the transitional water masses,
showed maximum abundances in August and October
and minimum abundances in February. Ammotium cassis had peak abundances at both the upper and lower
boundaries of the transitional layer in February, but
only at the upper boundary during the other sampling
events. Eggerelloides scabrus and Elphidium excavaturn both had peak abundances in areas underlain by
the upper part of the transitional layer; the latter somewhat deeper than the former. Both revealed minimum
abundances in October compared to the other sampling
events. Ammodiscus? gullmarensis and Adercotryma
glomerutum were generally restricted to the transitional
water masses. Maximum abundances of the former
occurred in February and August, whereas the latter
E. Alve /Marine Micropaleontology 25 (1995)
176
5
0
IO
15
25
20
30
0
5
10
15
20
25
30
5
0
169-186
10
15
20
25
M.fusca
\
35
N
/
40
/
45
I
4
10
20
30
40
20
30
40
50
60
0
10
20
E scabrus
30
40
50
0
40
60
120
I60
S. lusilormw
If---
---___
Fig. 5. Numerical density (no. per 35 cm3) of abundant stained species during four sampling events in 1988. Dashed line = February,
line = May, stippled line = August, thin line = October. Note the scale difference between some n-axes.
thick
E. Alve / Marine Micropaleontology 25 (1995) 169-186
177
5. Discussion
5.1. Patterns of recolonization
Stained / 35 cm3
0
10
20
30
40
. D-
50
S.biformis
-+--
M.fusca
-----c
E. albiumbilicatum
+
E. excavatum
--c
A. glomeratum
-.-o-.-
A. cass,s
-
S. fusiformis
- - * -
E. scabrus
..
.+...
60
A.? gullmarensis
Fig. 6. Depth distribution of the numerical density (no. per 35 cm3)
of abundant species in 1988. The density data are average values
over four sampling events for every 5 m water depth.
showed maximum abundances in May and August, and
was least abundant in February. Spiroplectammina
biformis occurred at all depths below the B.S.L. However, it was abundant only below the transitional layer,
except for two minor peaks in February and May, just
below the B.S.L. Stainforthiafusifonnis was present in
the lower parts of the transitional layer, but frequent
occurrences were restricted to deeper areas. It showed
maximum abundances in February, August and October and the values were exeptionally high ( 132-207
individuals per 35 cm3) compared to all other species
at all depths. In May, the maximum abundance of S.
fusiformis was only 62 individuals per 35 cm3at 41 m.
The numerical density of the abundant species added
over the four sampling events and averaged over five
meter intervals of water depth, showed a clear depth
succession of peaks from one dominant species to
another (Fig. 6).
Only a few investigations have focused on recolonization of benthic foraminifera due to improved environmental conditions (e.g., Cato et al., 1980; Finger
and Lipps, 1981; Schafer, 1982; Schafer et al., 1991)
and some have, experimentally, studied colonization of
sterile substrates placed either at the sea floor (Schafer
and Young, 1977; Kaminski et al., 1988) or at various
levels above it (Wefer and Richter, 1976). However,
the factors controlling
the transport mechanisms,
speed, and pattern of colonization and the dispersal of
species under different environmental
conditions are
still poorly understood.
Transport mechanisms of benthic foraminiferal tests
in the marine environment include suspended load and
bed load, floating plants, ice, turbidity currents and
mass flow but the former two are considered to be the
most important (see Murray, 1991 for summary and
discussion). In the present investigation area, suspension followed by lateral transport is considered to be
the most likely mechanism, because the species which
colonized the area between 1984 and 1988 could not
have been transported down from shallower water
depths, as they were not living there in 1984. A passive
distribution mechanism was also presumed to be the
most likely explanation of the recolonization
in the
deeper areas of the Baltic after reestablishment of oxic
conditions (Wefer and Richter, 1976). However, the
vast majority of transported benthic foraminifera are
reported to be dead, whereas live specimens are only
rarely reported from the water column. For instance, in
the western English Channel
and the Western
Approaches, which are highly unstable hydrodynamically, only scattered individuals of live specimens
( > 76 pm) were recorded in suspension by Murray et
al. ( 1982). They suggested that it was exceptional for
live foraminifera to be thrown into suspension and that
it probably was not a successful or widespread means
of dispersal in those areas. On the other hand, it is
possible that the pseudopodial networks of adults are
more extensive (bigger and stronger) than those of
juveniles and, therefore, more efficient in “anchoring”
the tests to the substrate. Thus, adults may be less readily suspended than juveniles and empty tests, and the
possibility that more live specimens might have been
178
E. Abe /Marine Micropaleontology 25 (1995) 169-186
recorded if fractions less than 76 pm also had been
investigated, can not be excluded. Another possibility
for benthic foraminiferal colonization of a new area is
that they actively migrate there, as opposed to passive
transport. However, even though some species are
mobile (e.g., Schafer and Young, 1977; Travis and
Bowser, 1991) and movement rates of up to 0.5 mm/
min have been recorded (Kitazato, 1981)) it is not
likely that this mechanism is efficient enough to explain
colonization by species which have immigrated over
some distance (e.g., several kilometers). Migration by
self locomotion is, of course, possible within limited
areas.
It is reasonable to assume that the recolonization rate
depends on whether the area to be colonized becomes
suitable at the right time of the year relative to the
reproduction patterns of the potential colonizers. Wefer
and Richter ( 1976) speculated that a recent reproduction in the source area, which would supply small and
medium sized shells for transport, was a prerequisite
for the suspended-transport
mechanism. The rate of
colonization also depends on the efficiency of the transporting mechanism (i.e., speed of water movement)
when the individuals in the source area are of a size
and growth stage suitable for transportation.
5.2. Diversity and total stained abundance
Drarnmensfjord represents a hydrographically complex system since most environmental parameters vary
over relatively short vertical distances, ranging from
seasonally changing temperature conditions in the well
oxygenated, brackish surface layer to slightly brackish,
anoxic water masses of stable temperature at intermediate and greater depths. This means that the forarniniferal assemblages are trapped between two basically
different extremes, namely seasonally variable brackish water conditions and nearly permanently anoxic
conditions. As most benthic foraminifera are adapted
to normal marine salinities, the general trend in modern,
shallow water, foraminiferal assemblages is an increasing species diversity along increasing salinity gradients
and with increasing environmental
stability. In Drammensfjord, however, the positive effects of increased
marine influence with depth is counteracted by deteriorated oxygen conditions which leads to a decreasing
species diversity towards the redox boundary and the
complete exclusion of foraminifera in the permanently
anoxic areas. Indeed, low diversity in the deeper areas
was also likely due to the fact that they represent an
early phase in the recolonization.
In May of both 1984 and 1988, maximum peak abundances were recorded immediately below the B.S.L.
Substantial amounts of the organic material and nutrients enter the fjord via the river water. This material is,
in turn, transported southwards in the B.S.L. and some
of it settles in the fjord, while the rest is transported
further south to affect other parts of the Oslofjord system (Magnusson and NESS, 1986). On its way southwards, particulate material in the lower part of the
B.S.L. (including recently dead phytoplankton)
falls
out of suspension because of reduced velocity due to
friction between the B.S.L. and the underlying transitional layer. The friction also causes resuspension of
the surface sediments where the boundary between the
water masses impinges on the fjord slope. This implies
that the areas immediately below the lower boundary
of the B.S.L. receives substantial amounts of organic
material and nutrients. Hence, these areas may support
large populations of species which are able to tolerate
the otherwise variable environmental
conditions prevailing there. In the present case, it might explain the
maximum abundances of A. cask in both 1984 and
1988, and E. excauatum in 1988 in the upper part of
the transitional layer.
When the transect was investigated for the first time
in May 1984, the area was about to recover from the
severely oxygen depleted conditions in the late 1970s
and in 1982. No oxygen data are available from the
1984 sampling event, but sporadic oxygen measurements showed that anoxic conditions (with HPS) were
present at water depths greater than about 30 m during
June, August, and October 1982, whereas in December
(i.e., winter, when the redox boundary normally is at
its shallowest position) of both 1983 and 1984, oxic
conditions were recorded down to 45 m (Magnusson
and NZSS, 1986). Consequently, there was adeep water
renewal during the spring of 1983. This implies that
oxic conditions had already prevailed down to about
45 m for more than one year before the samples were
collected in May 1984. Despite this, no living individuals were recorded deeper than about 30 m, indicating
that recolonization of the areas which had been reoxygenated for more than a year was slow. By 1988,
however, the abundance in the transitional layer had
more than doubled, more species had been introduced
E. Abe/Marine Micropaleontology
25 (1995) 169-186
to the area, and living individuals were recorded down
to 50 m, corresponding
to the position of the redox
boundary (Fig. 1C).
There are sevaral possible explanations for why the
sediments below 30 m water depth had not been recolonized after having been oxygenated for more than a
year. First, it is reasonable to assume that foraminiferal
tests are most effectively thrown into suspension and
transported during periods of deep water renewals
when substantial amounts of water enter the fjord and
disturb the sediment surface on its way towards the
head. Consequently, living individuals may have been
transported to the investigation area during the deep
water renewal in early 1983 but since the areas deeper
than 30 m had suffered from anoxia over several years,
the surface sediments were probably not suitable for
recolonization immediately after reoxygenation.
Second, the suspension and transport mechanism might
not have been efficient enough to transport any living
individuals to the area in the time period between the
deep water renewal in early 1983 and May 1984. A
similar time lag before recolonization
was found on
artificial substrates, installed above the sea bottom in
the Baltic, were the first living foraminifera did not
appear until 7-8 months after installation (Wefer and
Richter, 1976). The time lag was explained by a probable absence of strong water movements and/or lack
of small individuals to be transported. In Drammensfjord, it is not reasonable to assume that lack of small
individuals in the source area south of the transect was
responsible for the time lag, as several species with
different reproduction rates were involved, implying
that juveniles always were available. Third, of the few
species living along the transect in 1984, only A.? gullmarensis was abundant below 30 m in 1988. This indicates that factors other than oxygen limited the
colonization at greater depths.
5.3. Species response
The shallower areas influenced by the B.S.L. were
dominated by agglutinated, low diversity Miliammina
fusca assemblages in both 1984 and 1988 (Figs. 3 and
4) suggesting no detectable environmental changes. In
1984, calcareous taxa occurred only at intermediate
depths in the transitional layer and they were never
abundant. By May 1988, both Elphidium albiumbilicatum and E. excavatum had established themselves in
119
the lower part of the B.S.L., the former associated with
more brackish conditions than the latter. E. excavatum
was also abundant in the transitional layer and it was
even the dominant species just below the B.S.L. On the
other hand, the general distribution of the agglutinated
Ammotium cassis had not changed over the four year
period and maintained its peak abundance just below
the boundary between the B.S.L. and the transitional
layer. The abundance
was, however,
somewhat
reduced in 1988 compared to 1984. This might be due
either to annual population fluctuations or to reduced
concentrations
of particulate organic material in the
water flowing over and/ or settling on the surface sediments, as the species is known to benefit from elevated
concentrations of suspended particulate organic matter
(e.g., Olsson, 1976).
Eggerelloides scabrus occurred only at intermediate
depths in the transitional layer in 1984, whereas in
1988, it was living in both shallower and deeper areas,
although still restricted to the transitional layer. The
lack of stained individuals at 14 m was probably a
seasonal effect as it was, together with Ammotium cassis, the most abundant species in the dead assemblage
in this sample. Eggerelloides scabrus, a widespread
inner shelf species in northern European seas, also
enters fjord environments
but requires salinities
> 24%0 during most of the year (summary in Murray,
1991). In Drammensfjord, it did not occur in the riverinfluenced northern areas in 1987-1988 when the redox
boundary there was at about 40 m and its high abundance in the southeastern parts indicated that it is
closely associated with the marine water entering over
the sill ( Alve, 1990). Following the cessation of dumping activity in Chaleur Bay, Canada, Eggerella advena
(the West Atlantic counterpart to E. scabrus) was,
together with A. cask, the pioneer species which had
repopulated most of the dump site substrate after one
month (Schafer, 1982). It was suggested that this recolonization was related to active mobilization of, for
instance, E. advena as it had shown to be one of the
most mobile species in tank experiments (Schafer and
Young, 1977). Consequently, lack of a sufficient passive transport mechanism should not have prevented
colonization of E. scabrus below 30 m in Drammensfjord after the substrate had been oxygenated for
more than a year. The increased depth distribution of
E. scabrus from 1984 to 1988 rather suggests that even
though it is known to tolerate oxygen concentrations
180
E. Alve /Marine Micropaleontology 25 (1995) 169-186
of <OS ml/l (I. Olsson, pers. commun., 1989), it
needed more than one year to colonize sediments recovering from prolonged periods ( > 5 years) of nearly
permanent anoxia.
The most unusual finding, compared to earlier investigated modern foraminiferal assemblages, is the dominance of Ammodiscus? gullmarensis in the deeper
parts of the 1984 transect, where it was the most abundant species closest to the permanently anoxic, deeper
water masses. Modem occurrences of Ammodiscus species are reported from a range of environments from
brackish, shallow water areas to abyssal depths (summary in Hiltermann, 1989). However, to the author’s
knowledge, assemblages dominated by one or more
Ammodiscus species have, with the exception of two
samples between 2500 and 3000 m water depth in the
Sea of Japan (Matoba and Honma, 1986)) only been
reported from the fossil record (e.g., Nagy and Johansen, 1991 and references therein). In May 1984, its
living distribution was limited to 24-30 m. Consequently, it was the best adapted species to survive in
soft, muddy, organic-rich
sediments influenced by
slightly brackish
bottom water (salinity
mainly
between 29 and 30%0, occasionally
27%0) which
recently had been closely bordered by nearly permanent anoxic waters. By May 1988, the population and
vertical depth distribution
of A.? gullmarensis had
increased and it remained the most abundant species in
the same depth interval as in 1984. As for E. scabrus,
it took more than a year for A.? gullmarensis to colonize
the sediments below about 30 m water depth. Nothing
is known about its mobility.
Spiroplectammina biformis and Adercortyma glomeratum were, in addition to Elphidium albiumbilicaturn, new arrivals in 1988 compared to 1984 (Fig. 3).
Scattered empty tests of these taxa were present, however, in some 1984 samples indicating that either minor
populations of the species had lived there recently or,
more probably, that suspended empty tests had been
transported from more southern areas where they have
lived, at comparable depths, for more than one thousand years (Alve, 1991). Their absence in 1984, especially in the middle and upper parts of the transitional
layer, can not be explained by a prolonged recovery
period from anoxic conditions, as these areas had never
been anoxic.
In 1984, A.? gullmarensis strongly dominated the
areas close to the redox boundary at water depths down
to 30 m. This was the case for the transect discussed in
the present study (middle part of the eastern side of the
fjord) and of a 1988 transect in the northeastern part
of the fjord ( Alve, 1990). Stainforthiafusiformis
was
absent from both transects. The dominance of A.? gullmarensis and the absence of S. fusiformis occurred at
times when the downward limit of oxygenated bottomwater conditions coincided with the lower parts of the
transitional layer. This probably indicates that, for most
of the year, S. fustformis requires somewhat higher
salinities ( > 30%0) than A.? gullmarensis. Consequently, it is reasonable to infer that adverse salinity
was the causative factor of the absence of S.fustformis
close to the redox boundary when the latter was located
in the lower parts of the transitional layer.
In 1988, of all the stained species present in the
middle transect of the eastern part of the fjord, S. j%siformis was the numerically most abundant down to 5 1
m. Two important observations are that its living distribution was primarily concentrated in areas beneath
the stable deep water (i.e., deeper than the transitional
layer) and that there were few other co-occurring species. These facts suggest that S. fuszformis was the first
successful abundand recolonizer of the formerly anoxic
areas.
Bulimina marginata was not present in the 1984
samples although scattered individuals
making up
< 2% of the stained assemblages were present at > 22
m water depth during all seasons in 1988. This is
another indication of improvement because in other
parts of Oslofjord B. marginata is commonly found in
association with S. fusiformis (Risdal, 1964; Alve and
Nagy, 1990).
5.4. Seasonal variations
As the profile was sampled only four times during
one year, it is not possible to draw any detailed conclusions about seasonal population dynamics. It is possible, however, to get a rough impression because each
of the four sampling events represent the four seasons
of the year and the close spacing of the samples should
compensate for distributional patchiness. Variations in
abundance is seen in the depth distribution of most
species (Fig. 5) but this does not affect the general
distributional trends. In fact, the phenomenon is not
surprising, as Murray ( 199 1) concluded that variation
in standing crop size is normal for shallow-water ben-
E. Alve /Marine Micropaleontology 25 (1995) 169-186
thic foraminifera. An additional point which is important to keep in mind, is that because only the > 125 pm
fraction was analysed, the earliest growth stages after
reproduction are not recorded. Consequently, very low
abundance values might, in some cases, be due to recent
reproduction (dominance of small, < 125 pm individuals) rather than to an actual low abundance of the
species.
The most striking feature of the distribution is the
distinct depth succession of peak abundances from one
species to another. Also, although the samples were
collected at four seasons, the living assemblages show
remarkably
consistent
distributional
patterns. This
might be due to the fact that the foraminiferal assemblages in Drammensfjord are not influenced by seasonally dependent food supplies to the same extent as many
other shallow water areas (e.g., Erskian and Lipps,
1987), as excess supplies of nutrients are available
throughout the year. The main seasonally dependent
food supply is phytoplankton
but their abundance is
not as high as should be expected considering the high
supply of nutrients. This is due to poor light conditions
which limits their main distribution to the upper 4-5 m
of the water column, to the short residence time of the
B.S.L, and to unfavourable
salinity conditions for
marine species (Magnusson and Naess, 1986). Consequently, competition for food should not be a limiting
factor at any time of the year, except for possibly selective phytoplankton
feeders. The species distribution
down to about 30 m reflects, in addition to possible
nutrient preferences, their relative response level to
salinity and temperature variations. Below this depth,
depleted oxygen and stressed environmental conditions
due to the fact that the area recently had been anoxic,
start influencing the distribution pattern, in addition to
the previously discussed parameters.
The species can be listed as follows with regard to
increasing salinity requirements and decreasing temperature ranges: M. fusca, E. albiumbilicatum, E. excauatum, A. cassis, E. scabrus, S. biformis, A?.
gullmarensis, A. glomeratum, and S.fusiformis (Table
1). The B.S.L., which represents a harsh environment,
was dominated by M. fusca, a cosmopolitan species,
which tolerates most environmental fluctuations typical
of brackish shallow water areas (summary in Murray,
1991). In the western Baltic, size distribution curves
representing populations collected every 2 to 4 weeks
from July, 1973 to May, 1975, did not show any definite
181
reproduction cycles (Wefer, 1976). The growth period
of M. fusca was suggested to be 3 months. In Drammensfjord, the relatively stable abundance from February to August supports Wefer’s conclusion about lack
of a strong seasonality in the reproduction cycle.
The only other modern E. albiumbilicatum association reported in Europe, is from 4m water depth ( 87%
of total assemblage) in Oslofjord (as Nonion depressulus asterotuberculatus
by Risdal, 1964) but it is a
common species in Quaternary deposits (e.g., Knudsen, 1985, 1993). Risdal reported the number of total
(living + dead) individuals at each station (upper l-2
cm of sediment) and only indicated whether stained
individuals of the species were present or not. Relative
frequencies of > 10% of the total assemblages of E.
albiumilicatum were restricted to 4-6 water depth but
stained individuals were present from 3 to 10 m. The
distribution of E. albiumbilicatum in Drammensfjord
is in good agreement with Risdal’s findings as far as
the hydrographical characteristics are concerned. It also
agrees with the findings of Austin and Sejrup (1994)
from Syslakvag, western Norway. The increasing
abundance
of E. albiumbilicatum
from February
through May to August and October (Fig. 5)) suggests
that it reproduced during late winter and spring when
the temperature was at a minimum in the upper part of
the transitional layer (Fig. 1B).
The populations of A. cassis show seasonal variations at the lower boundary of the transitional layer
where it was frequent only in February, whereas the
size of the population was fairly constant over the year
at the upper boundary. In the western Baltic, it was
suggested to have a growth period of 5 months, with
reproduction occurring in December, May, and October (Wefer, 1976). A. cassis either lies on the sediment
surface or it occurrs within the upper few (3-4) cm of
the sediment (Olsson, 1976; Linke and Lutze, 1993).
The fact that it is associated with the boundaries of the
transitional layer in Drammensfjord, is in accordance
with occurrences of this species in other temperate
areas (e.g., Olsson, 1976; Scott et al., 1977; Alve and
Nagy, 1986) where it shows an increased abundance
in transitional environments with high concentrations
of particulate organic material, such as those influenced
by a halocline (Olsson, 1976) or by breaking internal
waves (Olsson, 1977).
Elphidium excauatum reproduces throughout the
year (Haake, 1967) and a growth period of 3 months
182
E. Alve /Marine Micropaleontology 25 (I 995) 169-186
was suggested by Wefer ( 1976). In Drammensfjord, it
was frequent in the upper part of the transitional layer
at all sampling events, but the values were significantly
higher in February, May, and August compared to
October. Also, its shallowest occurrence (lower part of
the B.S.L.) was recorded in February and May, during
periods of minimum temperatures.
Eggerelloides scabrus, A.? gullmarensis, and A.
glomeratum showed maximum abundances in the transitional layer during all sampling events. There were
no obvious trends of seasonal variations in their abundance patterns, so they seem to maintain relatively
static size of their populations throughout the year. This
might reflect that they are able to benefit from the permanent excess in food availability,
by reproducing
independently of the season of the year.
Spiroplectammina biformis showed the widest depth
range distribution of all species but maximum abundance occurred below the transitional layer. The drastic
drop in abundance from February to May in the deeper
parts of the transect might reflect that the sediments
had been disturbed both physically and chemically by
the inflowing water during the renewal process in early
spring and that new reproduction just had occurred.
These deeper sediments were probably particularly easily disturbed due to their soupy consistency where the
border between the sediment and the overlying water
is very diffuse. Subsequently, the new generation was
gradually built up during the summer and fall. It took
several months before it became abundant down to 45
m, as suggested by the successively increasing abundance with depth from May through August to September (Fig. 5).
Stainforthiafusiformis occurred in the lower parts of
the transitional layer but maximum abundances were
always confined to deeper areas, close to the redoxboundary (Fig. 5). Its high abundance during all sampling events supports Murray’s ( 1992) assumption that
it reproduces throughout the year. In May however, its
abundance was reduced compared to the other months.
In February, the dissolved oxygen concentrations
immediately above the sediment water interface (about
O-15 cm above the sea floor) were 0.37 and 0.16 ml/l
at 46 and 48 m, respectively, whereas H2S was recorded
at 50 m. It is reasonable to assume that the oxygen
concentration at each of these stations were considerably lower in the pore water of the soupy, organic-rich
sediments. Recent experimental studies have shown
that S. fusiformis migrate upwards in the sediments and
concentrate in the surface 0.5 cm when the oxygen
concentrations in the overlying water is lowered to 0.2
ml/l (Alve and Bernhard, 1995). Additionally, after
one month of exposure to oxygen concentrations of 0.2
ml/l many individuals had climbed up on polychaete
tubes in order to “seek” more oxygenated conditions.
In Drammensfjord, the individuals had no elevated substrates to climb up on and the individuals might have
died before the deep water renewal. The reduced abundance in May might additionally, in the same way as
for S. biformis, reflect stressed conditions in connection
with the deep water renewal and that reproduction had
just started. However, S. fusiformis became abundant
at greater depths more rapidly than S. biformis; an indication of its opportunistic nature (Alve, 1994).
The reason why the foraminiferal abundance showed
maximum values close to the redox boundary, might
be due to the fact that they were protected from predators (Buzas et al., 1989). This, however, is probably
not the only explanation as S.fisiformis, which clearly
was the dominant species in the assemblages, also is
known to flourish in other stressedenvironments
inhabited by possible predators, for instance the Danish slope
of the Skagerrak Basin (Alve and Murray, 1995). The
most reasonable explanation is that S. fusiformis has a
unique ability to quickly colonize and build up large
populations in recently disturbed environments. As it
is a small, thin shelled, calcareous form, which seems
to reproduce throughout the year (Murray, 1992; this
paper), it is likely that juveniles of this species are
easily suspended and transported to suitable places for
colonization.
5.5. General comments on interspecific salinity and
temperature requirements
From a geological point of view, it is noticeable that
the depth distribution of the various species is relatively
consistent during all sampling events. Hence, by considering their numerical densities added over the four
sampling events and averaged over five meter intervals
of water depth, it turned out that, with increasing water
depth, there was a clear succession of peaks from one
dominant species to another (Fig. 6). Except for possible gains or losses through post mortem alterations,
this kind of time-averaged data is what gets preserved
in the geological record. The succession of the specie!:
E. Alve /Marine
Micropaleontology
in Table 1 shows a distinct trend with increasing tolerance to increasing euryhaline and eurythermal conditions from the bottom (S. fusiformis) to the top (M.
fisca) of the list. The trend is consistent whether the
maximum depth range of each species (Range I), or
only their high abundance range (Range II), is being
considered.
6. Conclusions
The following conclusions can be drawn based on
analysis of living ( stained) benthic foraminifera in surface (O-l cm) sediments, collected along an environmentally variable depth transect (from brackish, well
oxygenated waters, to anoxic waters of slightly less
than normal marine salinity) in Drammensfjord
in
1984, and four years later, when the position of the
redox boundary in the water masses was lowered by
about 20 m:
In May 1984, the deeper parts of the investigated
profile had been oxygenated for more than a year, after
having suffered from a prolonged period ( > 5 years)
of nearly permanent anoxic conditions. No benthic foraminifera had colonized the formerly anoxic areas and
foraminifera were only present down to water depths
where the redox-boundary had been positioned before
oxygenation. However, by May 1988, the foraminiferal
abundance was more than doubled in areas influenced
by the transitional water masses, four species which
were not recorded in 1984 had immigrated to the area,
and living individuals were present down to the redoxboundary. It is concluded that the lower limit of the
foraminiferal distribution in 1984 was at the same position as it was before the deep water renewal in the spring
of 1983 and that it took more than a year before the
soupy, organic-rich sediments, that had been exposed
to anoxia for several years, became suitable for recolonization.
The species diversity was clearly negatively affected
by the stressed environments in both the upper (brackish) and lower (anoxic) parts of the profile even though
these environments were of a completely different character. The positive effects of increased marine influence
below the brackish surface layer was counteracted by
the decreased dissolved oxygen concentrations
at
greater depths and the fact that the area just recently
25 (1995) 169-186
183
had been oxygenated, resulting in a maximum diversity
at intermediate depths.
An exceptional finding is the dominance of the
agglutinated
Ammodiscus?
gullmarensis
in soft,
muddy, organic-rich sediments influenced by slightly
brackish bottom water in the area where the redox
boundary had been at its shallowest position. This is
the first modem record of a completely agglutinated
dominated assemblage bordering anoxic water masses.
Maximum abundance during all seasons, except the
spring (May), was recorded between the lower part of
the transitional layer and the permanently anoxic bottom water. The overall dominant species here was
Stainforthiafusiformis,
which was the first important,
and most successful colonizer of the formerly anoxic
areas.
The nine abundant species recorded along the transect showed a distinct water depth succession of peak
abundances which, in addition to other environmental
parameters (food preferences and tolerance to stress
caused by fluctuations in dissolved oxygen concentrations) , reflected their interspecific tolerance to increasing
euryhaline
and
eurythermal
conditions.
Spiroplectammina
biformis showed the widest depth
range distribution of all recorded species.
7. Fauna1 reference list
Generic names are in accordance with Loeblich and
Tappan ( 1987).
Adercotryma glomeratum (Brady) = Lituola
glomerata Brady, 1878
Ammodiscus? gullmarensis
(Hoglund) = Ammodiscus plunus Hoglund, 1947
Ammotium cassis (Parker) = Lituola cassis Parker,
1870
Eggerelloides scabrus (Williamson) = Bulimina
scubru Williamson, 1858
Elphidium albiumbilicatum (Weiss) = Nonion
pauciloculum Cushman, subsp. albiumbilicatum
Weiss, 1954
Elphidium excauatum (Terquem) = Polystomella
excauatu Terquem, 1875
Miliamminafusca
(Brady) = QuinqueloculinaJusca
Brady, 1870
184
E. Alve /Marine
Micropaleontology
Spiroplectammina biformis (Jones and
Parker) = Textularia agglutinans d’orbigny var.
biformis Parker and Jones, 1865
Stainforthia fusiformis (Williamson)
= Bulimina
pupoides d’orbigny var. fusifonis
Williamson, 1858
Acknowledgements
I am sincerely grateful to Jeno Nagy, Fulvio Bomb,
Nils Gundersen, Halvor Johansen, Eli Kjekshus, Erling
Siggerud and the captain, Torgeir Solstad, for assistance during the various cruises with the research vessel
Bj@rn F@yn. Joan Bernhard and John Murray are
thanked for helpful comments on the manuscript. The
project was funded by the Norwegian Research Council
for Science and the Humanities (NAVF) .
For further information the author can also be contacted via INTERNET, her e-mail address is elisabeth.alve@geologi.uio.no.
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15.1984
(m)
0
0
s. b@miJ
S.
0
24.1988
by
0
0
2
0
0
0
s.il@mis
s. fqwni4
Total no. specimen,
hmm4.
,9%?.
M.flm
E.dbimbilicatim
A. cask
E.ezc-m
E. zcatml
0
0
0
0
0
0
0
0
0
0
0
0
0
0
A. StLWlW@tW+
S. bifcrm's
s.Ji&fmiJ
DO. spccimcns
0
0
A.? Sullmemis
m9l
0
E.rcbnu
I
20
0
0
0
0
0
0
0
,2
11
0
0
0
0
0
0
0
9
0
5
+-+_-
0
0
0
0
0
0
0
0
A. cnrrL
0
E. eu~vam
0
0
E.&wnbilic.hrm
4
3
1,
___-
0
0
0
0
0
0
0
0
M./WC0
18.1988
Onobu
0
S. Jin#mi~
1
0
s. bifmtis
sp.ximalr
0
0
A,? SJlmnreM”r
A. $mt?d?n
malno.
0
0
0
0
10
0
A.Ibmndlrm
0
0
0
A.? /*Uiwcnnt
0
0
0
3
0
E.Is~
0
0
1
0
E. acav~nn
0
0
A. corrL
0
16
,6
0
E.cxlkimwicm
10
0
0
0
0
0
0
0
0
10
10
2
M.fuco
4
0
0
A. &mmdwn
no. spccimcnr
0
.4.?gllllmw~s
‘mniJ
0
0
E.acawm
E.scnhm
Total
0
A.CUG
s.
0
LLczbimnbSicaam
s. l+ami4
4
IS,1988
M.fiKO
Fcbnry
Toulmrpsimcor
0
0
A. glaaavn
28
0
‘anui
0
0
A.? SIlunwetis
2,
0
4
E.ucov~m
&SC&
IO
3
0
2
A. cmiJ
M.Jkti
E.,dbimnbiiica
May
Wucr dqb
0
0
0
0
0
0
2
2
20
0
0
0
0
0
0
0
3
15
23
0
0
0
0
0
0
0
0
16
6
22
0
0
0
0
0
0
0
15
6
20
0
0
0
0
0
2
0
12
0
7
.__+
0
0
0
0
0
0
0
2
35
0
0
0
0
0
0
0
9
23
20
0
0
0
0
0
14
0
6
0
6
0
0
0
0
6
0
0
0
2
8
10
0
0
0
0
0
0
0
0
6
9
0
0
0
0
0
0
32
1
36
0
0
0
0
2
0
0
26
7
7
0
0
0
0
0
5
0
1
1
3
0
0
0
0
0
0
0
3
0
,O
1
0
1,
0
0
0
0
0
0
0
2
9
3
0
76
0
2
0
0
2
22
5
42
1
0
4
0
0
14
60
,2
3
0
-__-+
-
30
0
5
0
0
3
15
6
0
0
60
0
17
0
4
29
0
0
0
46
0
0
0
0
0
0
,
0
24
(40
0
0
47
,4
3
12
,2
2
0
2
,,
10
0
0
0
50
0
19
2
1,
9
6
0
0
0
15
76
0
7
1
24
19
,424
0
0
0
16
0
0
0
61
0
2
6
51
4
$4
0
0
0
79
0
3
2
23
I9
26
0
133
4
4
26
72
0
0
0
17
,
4,
0
3
4
19
8
4
0
0
0
67
0
1,
a3
0
5
20
15
32
9
0
0
0
3,
0
2
6
2
13
6
0
0
0
49
0
1
6
.
33
0
0
0
20
11
12
38
0
0
0
36
0
0
0
0
26
5
0
0
0
16
1
66
3
7
25
20
2
0
1
0
75
0
1
6
21
32
4
0
0
0
96
1
4
9
22
47
2
0
0
0
22
1
0
1
0
65
3
2
3
37
14
23
0
29
JO
49
0
4
6
23
8
2
0
0
0
27
0
2
0
11
5
5
0
5
73
6
4
34
(6
2
0
0
0
63
0
0
7
23
8
9
0
0
1
69
0
0
5
31
25
0
0
0
0
57
0
2
5
20
2,
0
0
1
40
t
1
16
$1
1
2
0
0
0
46
8
2
1,
18
0
0
0
2
24
0
15
6
0
0
0
0
0
56
2
2
25
10
4
0
0
0
75
4
2
6
34
16
2
0
0
0
13
0
6
2
1
1
0
0
0
0
14
0
0
0
13
1
0
0
0
0
27
0
0
26
3
0
25
0
24
Water depths and counting data (no. per 35 cm3) of stained foraminifera in 1984 and 1988 samples,
Appendix 1
0
4
0
5
9
5
0
0
0
3,
108
20
4
4
64
4
1
0
2
0
32
2,
---
105
7
26
46
0
1
0
0
0
64
1,
0
29
25
3
1
0
0
0
33
0
0
0
0
0
0
0
0
0
0
34
516
5
1,
46
0
0
0
1
0
0
0
(17
166
59
119
12
20
2
0
0
0
4
39
24
4
0
0
0
0
35
34
162
99
74
3
3
1
0
0
0
0
36
210000
4
0
0
0
4
16
11,
3,
I,
59
2
0
0
0
0
49
8
10
5
10
1
1
0
0
0
49
20
13
4
4
0
0
5
0
0
36
1
3
1
2
0
0
0
6
0
4
10
1
t
0
1
14
23
107
67
29
149
140
0
1
0
0
0
0
0
40
55
66
8
2
207
296
a2
0
0
0
0
0
53
39
7
1
5
0
0
0
0
0
0
106
134
17
1,
107
89
1,
0
0
0
3
0
0
0
0
0
52
5,
1
0
0
0
0
0
0
0
52
48
2
0
0
0
0
0
1
0
44
0
0
30
30
0
0
0
0
0 0
0
0
0
63
62
1
0
0
0
0
0
0
44
34
8
0
0
0
0
0
1
0
42
0 0
0
0
0
41
76
75
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
45
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
7
13
6
22
22
0
0
0
5,
0
3
3
0
0
0
0
0
0
0
0
3
3
0
0
0
0
0
0
0
0
60
0
---f
2
2
0
0
0
0
0
0
0
0
49
0
0
0
0
0
0
0
0
91
63
6
0
0
0
0
0
0
0
0
0
0
0
0
0
0
132
139
4
1
0
0
0
0
t
0
2
2
0
0
0
0
0
0
0
0
0
40
39
1
0
0
0
0
0
20
19
0
0
0
0
0
0
0
0
0
46
0
0
47
0
0
46