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Growth, survivorship and reproduction
of Daphnia middendorffiana in several Arctic
lakes and ponds
P. M. YURISTA 1,3 AND W. J. O’BRIEN 2,4
1DEPARTMENT OF BIOLOGY, UNIVERSITY OF MICHIGAN, ANN ARBOR, MI
UNIVERSITY OF KANSAS, LAWRENCE, KA
PRESENT ADDRESSES: 3US EPA (MED)
GREENSBORO, NC
-, USA
, USA
, USA AND 2DEPARTMENT OF ECOLOGY AND EVOLUTIONARY BIOLOGY,
 CONGDON BLVD. DULUTH, MN , USA AND 4UNIVERSITY OF NORTH CAROLINA GREENSBORO,
The growth, survivorship and reproduction of Arctic region Daphnia middendorffiana was investigated in several lakes and ponds on the tundra in northern Alaska and additionally in a laboratory
study. Growth rate equations, reproduction rates and survivorship under natural conditions were determined. The natural environments differed in the available resources; investigations were made in
undisturbed oligotrophic lakes, lakes undergoing nutrient manipulations, lakes recovering from nutrient manipulation, and a small human-created pond. The lakes also differed in the presence or absence
of fish. The results indicated that resource availability affected the growth, survivorship and reproduction of D. middendorffiana. The lake with the highest resources produced the greatest reproduction and growth. The environments with the lowest resources had the least reproduction. Secondly,
resource level was observed to influence life history choices. Under low resource conditions D. middendorffiana produced ephippia at first reproduction rather than neonates. Third, the results also indicated that refuge from predation significantly affects the distribution of D. middendorffiana. Lakes
that contain fish do not support significant populations of D. middendorffiana, although the growth
and survivorship studies indicate they could do well in those environments.
I N T RO D U C T I O N
Predictions of global climate change (Houghton et al.,
1990) have stimulated increased attention in Arctic ecosystems (O’Brien, 1992). Polar areas are projected to experience the largest impact as a result of global change
(Hansen et al., 1988; Houghton et al., 1990). Predictions of
the impact on community structure as a result of global
change are uncertain because there is limited biological
information from which to construct relevant models.
Daphnia is an important and often dominant species of
Arctic aquatic ecosystems (Edmondson, 1955; O’Brien et
al., 1979; Hebert and Loaring, 1980; Stross et al., 1980;
Hebert and Hann, 1986; Hobaek and Weider, 1999). In
oligotrophic aquatic ecosystems Daphnia serve as a keystone species that results in a high transfer efficiency of
energy from pico- and nanoplankton to higher trophic
levels (Stockner and Porter, 1988; Stockner and Shortreed, 1989). While several growth models exist for temperate zone Daphnia (Paloheimo et al., 1982; Kooijman,
© Oxford University Press 2001
1986; McCauley et al., 1990; Hallam et al., 1990), few
models exist for growth of Arctic zone Daphnia (Stross et
al., 1979; Yurista, 1997). One reason for there being fewer
bioenergetic models of Arctic species is the limited data
available on the growth and physiology of Arctic zooplankton for use as input or calibration data. Most recent
papers on Arctic region zooplankton species deal mainly
with population genetics (Boileau and Hebert, 1988,
1991; Weider, 1989; Dufresne and Hebert, 1995; Weider
and Hobaek, 1996; Hobaek and Weider, 1999; Weider et
al., 1999). More encompassing models for aquatic ecosystems in the Arctic also depend on zooplankton because of
the major role they play in energy transfer from primary
producers to the higher trophic levels.
Physiological parameters often vary among temperate
species (Goss and Bunting, 1980; Prosser, 1991). Biologists
hold the common expectation that physiological parameters should also vary between temperate and nontemperate species. An organizing feature for the
difference in comparative physiology between species has
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been their biological adaptations to different habitats
(Prosser, 1991). Ingestion rates for D. middendorffiana, an
Arctic region species (Hebert, 1995; Hobaek and Weider,
1999), are higher then for temperate species (Chisholm et
al., 1975). In addition, the peak ingestion rate for D. middendorffiana, occurs around 11–15°C (Chisholm et al., 1975;
Yurista, 1999a) whereas temperate species have peak
ingestion rates near 20°C (Lampert, 1987). Measured
assimilation rates for D. middendorffiana are considerably
different than for Daphnia collected from temperate
regions (Yurista, 1999a). The peak assimilation rates occur
at lower temperatures [13–15°C (Yurista, 1999a)] in
Arctic species than in temperate species [∼20°C (Lampert,
1977)]. Also, when respiration for D. middendorffiana is
scaled to the same allometric exponent as temperate
species, the effect from temperature was a downward shift
of about 5°C in stress tolerance (Yurista, 1999b). Daphnia
middendorffiana exhibits different physiology from temperate zone species.
The use of data from temperate zone organisms for
prediction in Arctic systems may have confounding effects
because of both interspecific differences in temperature
adaptations and life history strategies. The model by
Stross et al. (Stross et al.,1979) used physiological information from temperate species for respiration and assimilation rates and growth was calibrated to unpublished
observations for Arctic D. middendorffiana. Models that use
data from temperate zone organisms as input may not
provide accurate prediction under the more limiting temperature conditions to which Arctic species are subjected.
Temperate models also indicate that more studies are
needed at limiting resource conditions (McCauley et al.,
1990), such as oligotrophic waters in the Arctic. Even with
a good understanding of temperature adaptations, life
history choices will undoubtedly alter the success of an
organism (Lynch, 1989). Our understanding of life
history decisions in Arctic Daphnia is limited. The production of ephippia has been linked to day length (Stross,
1969). Adaptations of obligate asexuality have been
attributed to the short season (Brooks, 1957). Observations that increase insight into life history choices will
strengthen predictions concerning the effect of climate
change and provide comparative examples for other
species from the Tropics to the Arctic.
This study was designed to extend our basic knowledge
of the ecology of Arctic D. middendorffiana, a freshwater
cladoceran. In addition to the basic physiological processes of ingestion, assimilation and respiration (Yurista,
1999a,b), other important parameters in the construction
of production models include growth rate, survivorship
and reproductive output. These additional parameters are
known to depend on available resources. Growth, survivorship and reproduction were determined under field
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resource conditions ranging from resource-limited oligotrophic lakes to nutrient-fertilized lakes and also in a controlled laboratory situation. Resource availability was
monitored and elemental stoichiometry as an indication
of food quality was determined during and after some of
the experiments. Life history choices were inferred from
the observed results.
METHOD
Daphnia middendorffiana was collected at the Arctic Long
Term Ecological Research (LTER) site (O’Brien, 1992).
The Arctic LTER is located in Northern Alaska on the
foot hills of the North Slope of the Brooks Mountain
Range (Lat. 68°38N Long. 149°38W). Daphnia middendorffiana used in laboratory studies was transported to Ann
Arbor, MI and maintained in laboratory cultures (Yurista,
1999a).
The field experiments were conducted in ponds and
lakes (Toolik Lake, Lake S11, Lake N1, Lake N2-ref, Lake
N2-fert, Dam Pond and MS-2 Pond) near the Toolik Lake
Arctic LTER research area [(Hansen et al., 1992;
O’Brien,1992),
w
/w
kaw.
s:c.
ep
d
A
ru/tlilte.Table
tcth I]. Toolik Lake is a large (150 ha, 25
m maximum depth) unmanipulated lake. S11 is a small
lake (0.4 ha, 10 m maximum depth) and was undisturbed
prior to these experimental measurements (subsequent to
1995 S11 has undergone fish manipulation). Lake N1 (4.4
ha, 14 m maximum depth) was undergoing a nutrient
addition experiment during the growth measurement.
Lake N2 (1.8 ha, 10.7 m maximum depth) had previously
been fertilized and was under a recovery period. Lake N2
had a curtain installed across the middle of the lake to
establish a reference side (N2-ref) and a treatment or fertilized side (N2-fert) (Hershey, 1992). Lakes N1 and N2 are
located approximately 300 m from each other. Dam Pond
(0.1 ha, 1 m maximum depth) is a small pond, impounded
during the Alaskan pipe-line construction, in a flood plain
area of a third-order stream. MS-2 Pond is a thaw pond
that has formed in the permafrost of a gravel pad area
used for material storage during the construction of the
Alaskan pipe-line. MS-2 Pond is approximately 40 m2 in
area, with a maximum depth of 0.5 m, and is similar in
size to many naturally occurring ponds in the region. MS2 Pond differs from most ponds in that the bottom substrate is composed mostly of gravel and rock with very
little organic material. The lakes and ponds of this experiment contain natural populations of D. middendorffiana
(O’Brien et al., 1979) with the exception of Lake N2.
All D. middendorffiana used in these experiments were
obtained from adults collected in Dam Pond. Adults with
embryos were isolated from a collection on a single day and
held in the laboratory until the birth of the young, generally within 2 days of capture. Neonates (<24 h old) were
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Table I: Physical and chemical background information on experimental sites
Toolik Lake
Lake S11
Lake N1
Maximum
Specific
Specific
Area
Depth
epilimnion
conductivity
alkalinity
Secchi
depth
(ha)
(m)
(m)
pH
(µS cm–1)
(meq l–1)
(m)
150
25
<9
7.51
46
0.45
3.2–5.2
0.4
10
<4
7.95
193
1.58
4.5–8.2
4.4
14
<4
8.46
112
1.04
0.7–3.3
Lake N2-ref
~0.8*
7
<4
7.63
104
0.89
3.0–6.5
Lake N2-fert
~1.0*
10.7
<4
7.92
109
1.06
3.2–6.2
Dam Pond
0.1
1
MS2-Pond
0.04
0.5
Chemistry data is the 1993 average from all data points within the maximum epilimnion depth. Lake N2 has been divided by a curtain to separate it
into two experimental basins. Lake N2-fert was in a recovery phase from previous manipulations. Lake N1 was undergoing a fertilization experiment
during this trial. The observed range in Secchi depth is from 1993.
measured for initial size and counted out in groups of 10
to be placed randomly in 1.8 l field cages (O’Brien and
Kettle, 1981). The cages shield the experimental animals
from direct predation effects. The cages were suspended at
a depth of 2 m in the lakes and either mid-column or at 1
m in the ponds. The suspension method used an anchor
system and floats such that the cages were not affected by
surface waves. Two cages of 10 neonates each were placed
in Toolik Lake (Limno-Bay), Lake S11, Lake N1, Lake N2ref and Lake N2-fert in 1993 and in Toolik Lake (main
lake), Dam Pond and MS-2 Pond in 1995. The animals
were inspected and measured weekly with a calibrated
Wild dissecting microscope transported to each field site.
The cages were retrieved under water and kept submerged
until just prior to inspection. The cages were drained such
that animals were retained on one of the Nitex® screens
to the cage and observed under the dissecting microscope
long enough to measure and count all the animals. Bodylength measurements were made from the centre of the
eye to the base of the tail spine and recorded to the nearest
0.02 mm. The cages were quickly re-submerged and
returned to their mooring sites.
In 1993 chlorophyll a samples collected as part of the
Arctic LTER monitoring programme were used to assess
available resources for the Daphnia. The 1 m and 3 m
samples were averaged to determine a value for 2 m.
Correlation between particulate carbon and chlorophyll a
at several dates and in several lakes in 1995 indicated a
ratio of approximately 229 (n = 10, SE = 16). Estimates of
ambient resources in terms of carbon for 1993 were based
on this ratio. In 1995 particulate carbon and chlorophyll
a levels were collected in Toolik Lake. In the small ponds,
however, only particulate samples were collected to
observe resource availability. A known volume of 240–300
ml was filtered onto replicate 13 mm AE filters that had
been previously combusted at 450°C for 2 h. The filters
were analysed for carbon and nitrogen on a Perkin-Elmer
2400 CHN analyser. Replicate filters were also analysed
for phosphorus after persulphate digestion using the
molybdate method (Wetzel and Likens, 1992).
Laboratory animals (collected from Dam Pond) were
cultured at 12°C in separate 50 ml screw cap Pyrex vials
(n = 13 for each treatment) under continuous light conditions of approximately 20 µE m–1 s–1. Water and food
were replaced every other day and the condition and
length of each animal were recorded at that time. The
replacement of food every other day was not optimal but
provided a stressful and low-level resource environment
analogous to Arctic ponds. Algae food levels were
adjusted to the treatment levels using fresh log-phase
Chlamydomonas stock of known concentration as determined with a fluorometer. A Turner fluorometer calibrated with a known chlorophyll a standard (Sigma), was
used to determine the chlorophyll a content of live cultures. DCMU was used in the chlorophyll a measurements to obtain an accurate concentration by suppressing
photosynthetic electron transport and remove variation
due to different physiological conditions of the cells (Slovacek and Hannan, 1977). The carbon content was
determined with a Perkin-Elmer CHN 2400 of algae collected on ashed and rinsed 13 mm A/E filters. The results
were correlated to the fluorometer readings.
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Growth for D. middendorffiana under controlled conditions in the laboratory was determined with two levels
of food (175 µg C l–1 and 525 µg C l–1) at 12ºC. To account
for depletion of resources because of the batch culture
conditions, computations based on ingestion rates
(Yurista, 1999a) indicated average resource levels of 90 µg
C l–1 and 290 µg C l–1 respectively (computed for 2.0 mm
animals). The experimental food levels were consistent
with natural levels in Toolik Lake and the small ponds. To
control for maternal effects, neonates used in growth
experiments were obtained from adult D. middendorffiana
maintained under the same treatment conditions.
Growth of D. middendorffiana was determined from
length measurements using a calibrated dissecting microscope (40). Length was measured from the centre of the
eye to the base of the tail spine and recorded to the nearest
0.02 mm. A length–weight relationship, and composition
in carbon, phosphorus and nitrogen of D. middendorffiana
was available for making additional size comparisons
(Yurista, 1999a).
Statistical analyses were conducted with SYSTAT (7.0).
Because the test subjects were measured multiple times
(initially and four subsequent times) during the course of
the experiments, the statistical model was a repeated
measures ANOVA (Neter et al., 1990). Site and time were the
independent factors and replication was based on the
means for each of the two cages at a site.
R E S U LT S
Growth of animals in both 1993 and 1995 (eight sites, two
replicates each) as measured by length was significantly
different among the ponds and lakes (ANOVA F = 11.8,
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P = 0.0012 repeated measures, n = 16) with Lake N1 the
clear exception (Figure 1). Adults under most treatments
reached the approximate same final adult size (2.4 mm)
after about 15 days. Empirical von’Bertalanffy growth
models were determined for each of the lakes and ponds
(Table II). Growth in Lake N1 was faster and individuals
reached a greater final size (3.0 mm). Length was considered a comparable measure between treatments due to
the use of a single pond as a source of all experimental
animals. Additionally, the length to weight relationship is
unaffected by resource level (Lynch, 1989; Manca et al.,
1994) in the ranges of these experiments. Growth rate of
D. middendorffiana in laboratory studies was generally slow
at 12ºC (Figure 2). Maturity was reached after about
20–24 days. Some animals survived for over 115 days. The
size of animals when raised under the two food level treatments only differed noticeably into maturity (after 40
days).
Results of the field studies for survivorship varied
among the aquatic systems investigated (ANOVA F = 3.52,
P = 0.049 repeated measures, n = 16). The highest survivorship was observed in Toolik Lake (Figure 3). N2-fert
had the next highest survivorship followed by similar survivorship in Lakes S11 and N1 while N2-ref was the
lowest for 1993. In 1995 Toolik Lake again had the same
high survivorship, with Dam Pond having similar survivorship to that observed in Lakes S11 and N1 the
previous year. Lake N2-fert and MS-2 Pond had the
lowest survivorship over both years.
Energy allocated to reproduction in the field was
measured by egg production. The use of neonate production as a measure would be confounded because observations were made every 7 days and neonate survivorship
Table II: Standard von’Bertalanffy growth models (mm = a/[1 +
exp(b – c 3 day)]) as determined by non-linear regressions (SYSTAT
7.0) for each site
Site
a
b
c
R2
Limno Bay
Lake N1
Lake N2F
Lake N2R
Lake S11
Toolik
Dam Pond
MS2 Pond
2.47 (0.052)
3.12 (0.088)
2.38 (0.057)
2.25 (0.068)
2.52 (0.030)
2.31 (0.041)
2.26 (0.014)
2.19 (0.024)
0.56 (0.10)
0.97 (0.13)
0.48 (0.12)
0.44 (0.18)
0.61 (0.066)
0.37 (0.087)
0.30 (0.019)
0.29 (0.062)
0.19 (0.022)
0.19 (0.024)
0.19 (0.026)
0.23 (0.046)
0.22 (0.015)
0.20 (0.021)
0.15 (0.004)
0.21 (0.016)
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
Values within parentheses are the asymptotic standard error for each parameter estimation. The R2 for each
regression was 0.99 with n = 5 data points.
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Fig. 1. In situ measurements of Daphnia middendorffiana growth. Study
periods extended from 24 June to 27 July 1993 and 29 June to 27 July
1995. (a) 1993 for Toolik, N1, N2-fert, N2-ref and S11; and (b) 1995 for
Toolik, Dam Pond and MS-2 Pond. Error bars are one standard deviation. Approximate rankings of food resource levels (1–3) are indicated
in the key for each year based on quantity and average rank of C : P and
C : N.
in the interim was unknown. Laboratory reproduction
was measured with ephippia and neonate production.
Energy allocated to reproduction was significantly different between the natural systems (ANOVA F = 7.74, P =
0.0049 repeated measures, n = 16) and observed to be the
highest in Lake N1 in 1993 (Figure 4). Reproductive effort
in N1 was dominated largely by neonate production, as
was true of the other lakes. Toolik Lake and Lake S11 had
the next highest reproduction followed by the other lakes
and ponds. Reproduction for Toolik Lake was similar in
both 1993 and 1995. The Dam Pond reproduction was
lowest with only ephippia production. Reproduction in
Fig. 2. Growth rate and reproduction observed for Daphnia middendorffiana in laboratory cultures at 12°C and food levels of 175 and 525 µg C
l–1 (see text). Reproduction was initially by ephippia production until
approximately day 45. Error bars are one standard deviation.
MS-2 Pond was slightly higher than Dam Pond but similarly dominated by ephippia production (Figure 5).
In the laboratory at 175 µg C l–1 (average 90 µg C l–1)
total reproduction was low and composed mostly of ephippia production. Reproduction eventually was much higher
for Daphnia cultured at 525 µg C l–1 (average 290 µg C l–1)
(Figure 2). The first few reproductive events under each
laboratory treatment were ephippia production. Daphnia
middendorffiana is a facultative, if not obligate, asexual
(Edmondson, 1955; Zaffagnini and Sabelli, 1972; Hebert,
1987; Yurista, 1999a). Total ephippia production was
similar at both food levels. As the adult animals continued
to increase in size, reproduction switched to parthenogenic
neonate production at approximately day 45 (Figure 2).
The animals cultured at 0.175 µg C l–1 had minimal
parthenogenic reproduction while the animals at 0.525 µg
C l–1 produced considerably more parthenogenic offspring
after shifting from ephippia egg production (Figure 2).
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Fig. 3. Survivorship of Daphnia middendorffiana during in situ experiments. (a) 1993 for Toolik, N1, N2-fert, N2-ref and S11; and (b) 1995
for Toolik, Dam Pond and MS-2 Pond. Approximate rankings of food
resource levels (1–3) are indicated in the legend for each year based on
quantity and average rank of C : P and C : N.
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Fig. 4. Cumulative reproduction for Daphnia middendorffiana from in situ
experiments. (a) 1993 for Toolik, N1, N2-fert, N2-ref and S11; and (b)
1995 for Toolik, Dam Pond and MS-2 Pond. Approximate ranking of
food resource levels (1–3) are indicated in the legend for each year based
on quantity and average rank of C : P and C : N.
Seston availability varied within the lakes and ponds
(Table III). Carbon concentrations were the highest in
Lake N1, at values of ~1000–6400 µg C l–1. Lake N1
during this study was being manipulated for a multi-year
nutrient-addition experiment. The other lakes had lower
carbon concentrations but were closer in range to each
other (~100–350 µg C l–1), with an early bloom followed
by relatively constant levels. Carbon resources were the
lowest in Dam Pond with the MS-2 Pond only slightly
higher (Table IV).
Temperature data for the 1993 study were routinely
measured during Arctic LTER monitor sampling. During
the growth experiments temperature ranged from
approximately 11°C as the trials began to a mid-season
peak near 18°C with an average temperature of about
15°C (Table V). There was little difference in temperature

between lakes, indicating that the observed differences in
growth and survivorship are most likely due to factors
such as food availability and quality. Temperature data
was not recorded in the small ponds in 1995.
Particulate samples taken in 1995 (Table IV) to estimate
food quality indicated some differences between the lakes
and ponds. Ratios of elemental composition for available
resources varied. In general the C : P ratio of particulate
matter was good to marginal (range 200–650, Table IV)
(Urabe and Watanabe, 1992; Sterner et al., 1993: Sterner,
1997). Ranked next by C : N ratio, the highest quality food
(range 8–10) was found in Toolik Lake and S11 (Table IV).
C : N ratios were 10–12 in the other lakes and 10–20 in
Dam Pond. Terrestrial systems in tundra regions are often
nitrogen limited (Shaver and Chapin, 1980). Peat from
tundra sources probably influences the particulate C : N
ratio in the ponds but is an unimportant food source for
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Fig. 5. Percentage of reproduction as ephippia eggs under the different treatments for both years. As apparent resources by treatment decline in
quantity and quality (Tables III and IV) an increase in emphasis for ephippia production was observed. N1 had the highest total resource availability and Dam Pond the lowest.
Table III: Carbon resource concentrations (µg C l–1) at 2 m in
the study lakes, as computed from chlorophyll a concentrations (µg
Chl a l–1) determined from the average of 1 m and 3 m Arctic
LTER routine monitoring samples in 1993
Toolik
N1
N2-fert
14 June
551
1078
–
16 June
–
–
991
N2-ref
S11
–
304
–
18 June
–
–
–
–
492
21 June
858
1598
736
690
–
28 June
565
1266
1425
441
–
5 July
402
3006
252
273
–
7 July
–
–
–
–
133
12 July
159
2785
197
119
–
19 July
209
6485
281
209
–
26 July
279
5110
242
145
–
2 August
302
4635
350
141
–
4 August
–
–
–
–
429
9 August
286
3992
295
126
–
The conversion from chlorophyll a to carbon used a factor of 229. The zooplankton growth study
period spanned the time 24 June to 27 July.
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Table IV: Particulate carbon, nitrogen and phosphorus sample results collected in 1995
Date
(Chl a)
C
N
P
415
57.1
2.70
C:N
C:P
Toolik
19 June 1995
27 June 1995
593
–
5 July 1995
322
8.57
410
6 July 1995
–
363
47.6
2.43
9.04
398
15 July 1995
–
316
35.7
1.77
10.37
477
17 July 1995
294
26 July 1995
244
7 August 1995
283
Dam Pond
11 June 1995
–
157
14.8
2.05
15.73
204
15 June 1995
–
113
6.5
1.40
20.23
215
22 June 1995
–
117
9.6
1.23
14.28
254
4 July 1995
–
99
9.3
1.00
12.39
264
9 July 1995
–
170
22.3
1.70
8.90
266
15 July 1995
–
149
18.0
1.27
9.85
314
–
247
36.0
3.0
8.01
220
3 July 1995
–
291
38.6
2.13
8.56
383
9 July 1995
–
256
33.7
1.97
8.87
348
15 July 1995
–
594
68.4
4.70
10.39
337
–
294
41.1
1.20
9.93
654
1 July 1995
–
230
25.9
1.6
10.42
383
16 July 1995
–
158
17
1.4
10.87
300
–
281
25.4
1.90
12.71
394
MS-2 Pond
9 July 1995
S11
N1
15 July 1995
N2-ref
N2-fert
30 June 1995
The column (Chl a) is in carbon based on conversion (factor of 229) of Arctic LTER chlorophyll a monitoring data. All results are in µg l–1. Particulate
samples were collected at the depth of field culture chambers. The growth study period spanned the time 29 June to 27 July. Additional CHN and
phosphorous samples were also collected in 1995 from the study lakes of 1993. These samples are used to compare general food quality of the
different lakes and ponds. The results are in µg l–1. The level of fertilization for Lake N1 in 1995 had been reduced from the 1993 level.
Daphnia (Kling et al., 1992). Although measurements of
particulate matter were not made in 1993 it is expected
that the C : N ratio was similar to the 1995 measurements
reported here.
DISCUSSION
In general the short season and low ambient resources
levels in Arctic ponds and lakes provide little time and

resources for both growth and reproduction. Maintenance followed by growth are of first importance to an
organism and therefore should receive first allocation of
energy intake. Reproduction to maintain a population will
follow basic survivorship and growth. As resource levels
increase, reproductive output and, potentially, growth will
increase.
Resource quantity was assessed by particulate carbon
concentration measured both by chlorophyll a levels with
yurista (2199)(ds) 15/6/01 9:38 am Page 741
P. M. YURISTA AND W. J. O’BRIEN
GROWTH, SURVIVORSHIP AND REPRODUCTION OF ARCTIC DAPHNIA
Table V: Temperature (°C) from LTER monitoring data at 2 m during the 1993 and 1995 studies
1993
Toolik
N1
N2C
N2F
18 June
S11
1995
Toolik
9.99
21 June
7.75
11.28
11.11
10.64
19 June
28 June
9.05
11.56
11.09
11.29
28 June
7.80
5 July
13.84
16.17
15.75
15.97
5 July
12.48
12 July
14.87
16.43
14.96
15.47
19 July
18.14
17.97
18.00
19.05
17 July
15.82
26 July
15.24
15.19
15.36
15.46
26 July
10.88
13.39
13.21
13.99
13.55
11.13
10.42
10.51
10.72
7 July
2 August
13.97
4 August
9 August
6.08
12.88
7 August
10.41
Study extended from 24 June to 27 July 1993 and 29 June to 27 July 1995 each sampling season. Lake S11 is slightly more remote than the other
lakes and was monitored less frequently.
a conversion factor to carbon that was determined on the
local systems and by direct analysis in some situations.
Resource quality is an additional consideration and a
general assessment of quality was made by mineral
element ratios (Table IV). Recent research by MüllerNavarra et al. (Müller-Navarra et al., 2000) argues for fatty
acid composition as the appropriate index of food quality
although Boersma (Boersma, 2000) has found that
mineral needs must be met first.
Growth was comparable at low and medium resource
levels but enhanced at the highest level where Lake N1
had the largest investment in growth. Indirect effects on
life history from cues due to predation risk in the presence
of vertebrate predators (N1, N2 and Toolik have fish; S11
lacks fish) would predict an opposite response in size.
Invertebrate predators (Chaoborus, S11) would also elicit an
opposite indirect response to the one observed. The
observed effect was attributed to resource availability.
Similarly, in the laboratory study, eventual investment in
growth was highest at the higher food level. A basic level
of growth to maturation appears to be realized until
minimal reproduction can sustain a population. As
resource levels increase, additional energy may be
directed into enhanced reproduction and growth beyond
the basic maturation level as well.
Investment in reproduction by D. middendorffiana in this
study appeared to depend on available resources. Reproduction was noticeably low in environments with poor
resource conditions (Figure 4, Tables III and IV). In MS-2
and Dam Pond, where the quantity and quality of resources
were low (Table IV), survivorship and reproduction were
stressed. As resource quantity and quality increased in availability (Lakes N2-ref, N2-fert) survivorship improved as did
reproduction. As further increases occurred in resource
quantity and quality (Toolik Lake, Lake S11), so did reproduction. Finally, at the highest resource quantity (Lake N1)
further increases in reproduction occurred and additional
investments in growth were observed. Similarly, in laboratory studies the higher resource level translated into greater
reproduction. These study results bracket the range of conditions and responses that may be expected in natural
Arctic systems.
In addition to reduced reproduction in Daphnia spp. at
low resource levels, as noted by previous researchers
(Richman, 1958; Taylor, 1985), the Arctic D. middendorffiana also appears to exhibit life history choices at low
resource levels. Ephippia formation at first reproduction
in the laboratory and in the ponds under stress from low
resource conditions indicates priority to investment in
future generations. Resource levels may control induction
of D. middendorffiana diapause egg production in addition
to photoperiod as determined by Stross (Stross, 1969).
During the field experiments there was 24 h of daylight
and laboratory animals were cultured under continuous
lighting. In comparison, Stross and Hill (Stross and Hill,
1965) found multiple control (photoperiod and culture
density) for temperate D. pulex. In the present experiments
culture density was one animal per 50 ml in the laboratory
and one animal per 180 ml in the field, much lower than
in Stross and Hill (Stross and Hill, 1965). As culture
density increases so do resource depletion rates, hence
resource stress may be the second proximal stimulus

yurista (2199)(ds) 15/6/01 9:38 am Page 742
JOURNAL OF PLANKTON RESEARCH
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(Stross and Hill, 1965). The laboratory resource levels
(average 90 and 290 µg C l–1) may indicate the levels at
which growth and reproduction become stressed. When
ephippia production was significant under field conditions
(Figure 5), resource levels were also low and comparable
to the laboratory (Tables III and IV). Diapause eggs at
initial reproduction may indicate a life history choice for
investment in a future population due to resource stress.
Temperature did not vary significantly between the
different systems (Table V). An average temperature of
approximately 15°C was realized during these experiments. Therefore any differences in adult size (Lake N1)
are probably not attributable to temperature (McKee and
Ebert, 1996). The laboratory study had a slower growth
rate as to be expected from the lower temperature (12°C).
In laboratory studies for the energy budget of D. middendorffiana (Yurista, 1999a), a temperature of 13–14°C produced the most favourable effect on the energy budget for
activity, growth and reproduction.
Container effects need to be considered. In all treatments
D. middendorffiana were restricted to planktonic water
resources that freely passed through the cage Nitex® 153
µm mesh. This was probably more significant in the shallow
ponds where attached or benthic algae may provide a significant amount of available resources. Daphnia middendorffiana will forage on attached or settled algae as observed in
laboratory cultures. This resource became unavailable to D.
middendorffiana with the use of cages. That attached algae
may be significant could also be inferred from net tows to
obtain the experimental animals (Dam Pond) which indicated greater reproduction than observed in the cages. An
alternate explanation for this observation is that the early
season algae bloom accounted for greater reproduction at
the commencement of the experiments. All experimental
measurements were conducted subsequent to the early
season bloom. A second factor is that MS-2 Pond has little
to no vegetation surrounding it and is subject to turbidity
from sediment influx during rain storms. Cages potentially
restricted the movements of animals in avoiding the most
turbid locations. Turbid conditions are detrimental to
Daphnia (McCabe and O’Brien, 1983; Kirk, 1992). These
two cage effects may restrict extrapolation of the current
results to planktonic systems only.
At low but typical resource levels for Arctic systems
Toolik Lake provided a growth environment as good as, or
better than, most of the other lakes, even one that lacked
fish (Lake S11). The presence (Toolik, N1 and N2) or
absence (S11 and ponds) of fish did not greatly effect
growth or reproduction. Daphnia middendorffiana are not
common in Toolik and N1 but in this study grew and
reproduced well on the resources available in these lakes.
Fish predation is the probable mechanism for their lack of
abundance.


NUMBER

PAGES
‒

The distribution of Daphnia middendorffiana in Arctic
ponds and lakes is governed by several factors. First, in
even the most resource poor ponds (MS-2 and Dam Pond)
D. middendorffiana were able to survive, grow and reproduce. Threshold resources for comparable-sized Daphnia
(Gilwicz, 1990) are less then 25% of the minimum
observed in our measurements. Resource availability has
minimal constraint on which systems they may inhabit.
The population size within a system though will be dependent on the resource level. Second, D. middendorffiana and
D. pulex (found in Arctic ponds but never in Arctic lakes)
are generally eliminated from lakes with planktivorous fish
(O’Brien et al., 1979) although resources may be
favourable for their existence. Third D. middendorffiana tolerate invertebrate predation better then D. pulex (Hebert
and Loaring, 1980; Luecke and O’Brien, 1983; Dodson,
1984) and are found in ponds containing Heterocope septentrionalis. Finally, that D. middendorffiana do not co-exist with
D. pulex may be due to differences in competitive abilities
between species. The energy budget of D. middendorffiana is
considerably smaller than temperate zone D. pulicaria
(Yurista, 1999a). Whether the budget for Arctic D. pulex is
greater and allows for greater reproductive potential
(competitive ability) to displace D. middendorffiana is
unknown at this time.
AC K N O W L E D G E M E N T S
We would like to thank N. Bettez, M. Dornblazer and P.
O’Hara for collecting the LTER data. We would also like
to thank the anonymous reviewers whose comments
helped strengthen the paper. This work was supported in
part by grants from the Rackham School for Graduate
Studies, the Department of Biology, University of Michigan, and NSF grants, 921175, 9400722, and 9553064.
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