Direct and indirect effects of Ca and P decline on the
crustacean zooplankton of acid-sensitive, Shield lakes
Norman Yan
Michelle Palmer
Adam Jeziorski
Howard Riessen
Dallas Linley
Bjoern Walseng
Christian Laforsch
Andrew Paterson
Natalie Kim
Allegra Cairns
Michael Arts
Holopedium glacialis* as painted by G.O. Sars, late 1800s
Gel capsule margin
*formerly H. gibberum (Rowe et al. 2007)
Hypothesized links of logging, climate warming, acid rain and Bythotrephes
on interactions of Holopedium and Daphnia in Ontario lakes
WARMING CLIMATE
LOGGING 
ACID RAIN
Bythotrephes 
Ca 
P
Algae
Holopedium 
DOC 
Chaoborus 
Daphnia 
Objectives
1. To provide field evidence that low Ca is damaging
daphniids
2. To provide lab evidence for both direct and indirect
causes linked to reduced growth, delayed reproduction,
and reduction in anti-predator defenses
3. To suggest that falling P and rising DOC, and the spread
of an invading predator are additional stressors,
4. To suggest that the relative fitness of daphniids and
Holopedium has changed, now favouring Holopedium,
and to show that Holopedium is on the rise
5. To consider possible lessons for the OA field.
What I won’t discuss
• Older evidence of widespread damage to
important species
• That was both correlated with, and proven to
be caused by lake acidification
• From which recovery was possible
• After the acidity was neutralized, or acid
deposition was reduced
Is D. mendotae widespread & important at pH >6 (n=276)?
Daphnia
mendotae
Region
# of lakes
# of taxa
Dorset
Sudbury
Algoma
Thunder Bay
24
72
62
118
28
35
29
37
D. g. mendotae biomass (ug/L)
Is there a pattern with pH?
Can acid-sensitivity explain the pattern?
60
50
40
30
20
10
0
4.5
5.0
5.5
6.0
lake pH
6.5
7.0
Rank
Abundance of
D. mendotae
3
3
2
1
Trial
1
2
3
4-day LC50 pH (95% CI)
5.69 (5.5-5.9)
5.98 (5.7-6.2)
5.94 (5.7-6.1)
Pooled
5.85 (5.7-6)
7.5
Keller, Yan et al. 1990. ES&T 24: 1259
I won’t discuss if biota can recover if acidity is reduced
Mean crustacean richness
(taxa/standard count)
10
9
Middle Lake
8
7
6
5
4
3
Liming
2
1970 1975 1980 1985 1990 1995 2000 2005 2010
Yan and Strus 1980, CJFAS 37: 2282; Yan et al. 1996, CJFAS 53: 1301; 2004 Ecol. Lett 7: 452
What I will discuss
• Temporal, spatial and experimental evidence
that falling Ca, coupled with falling P & rising
DOC levels, and the spread of an invading
predator is damaging Ca-rich zooplankton in
dilute, oligotrophic lakes on the Canadian
Shield for reasons that are complex and vary in
importance from lake to lake
• The lessons of this story for ecologists
studying OA
Watershed 2EB (Muskoka)
in the Great Lakes watershed
in the province of Ontario, Canada
Dorset
Plastic Lake
Daphnia
Holopedium
• High Ca demand
• High P demand
• Vulnerable to
invertebrate predators
• Acid-sensitive
• Low Ca demand
• Low P demand
• Less vulnerable to
invertebrate predators
• Acid-tolerant
•
Photo by D. Taylor
•
Painting by G.O. Sars
35 years of monitoring at Dorset Environmental Science Centre
(8 DESC lakes + 36 other lakes with academic partners, especially York and Queen’s U)
1
2
3
4
5
6
7
8
Harp
Chub
Blue Chalk
Red Chalk
Dickie
Crosson
Plastic
Heney
1
2
3
4
8
8
5
6
7
The 36 lakes have changed since the 1980s*
30
7
Ice-free average in 2004 - 2005
pH
TP
25
20
6
15
10
5
5.96 to 6.21
5
6
9.2 to 8.4
3
(mg/m )
5
7
5
10
15
20
25
30
14
12
Ca
4
DOC
10
8
6
2
0
2.53 to 2.09
(mg/L)
0
2
4
4
3.02 to 4.10
(mg/L)
2
0
0
2
4
Ice-free average in the 1980s
*Palmer, Yan et al. 2011 CJFAS 68: 1038
6
8
10
12
14
Calcium has declined in 7 of 8 Dorset lakes*
BC
HP
3.5
CB
HY
CN
PC
DE
RCM
Dickie (DE)
is different
Ice-Free Ca (mg•L-1)
3.0
2.5
2.0
1.5
1975
1980
1985
1990
1995
2000
2005
*Molot and Dillon 2008, CJFAS; Jeziorski et al. 2008 Science 322: 1377, Yao et al. 2011 Water Res. Res
Why are calcium levels rising in Dickie Lake?
Ca load from all un-gauged sources:
2700 kg/yr
Dust suppressant added yearly >1998: 10,450 L
Ca concentration in suppressant solution: 196 g/L
Ca added in dust suppressant since 1998: 2050 kg/yr
Yao et al. 2011 Wat. Resour. Res
TP levels have declined
TP (µg/L) mean of ice-free season
16
BC
HP
14
CB
HY
CN
PC
DE
RC
12
10
8
6
4
1975
1980
1985
1990
1995
Year
*OMOE data, Hall and Smol (1996), Eimers et al. 2009 CJFAS 66: 1682
2000
2005
Holopedium and Daphnia differ in their Ca and P needs
Animals collected from 9 Ontario lakes *
*Jeziorski and Yan 2006, CJFAS 63: 1007
Also, Anderson & Hessen, Sterner, Elser, Brett, etc.
DOC levels are rising *
7
BC
HP
CB
HY
CN
PC
DE
RC
DOC (mg/L)
6
5
4
3
2
1980
1985
1990
1995
2000
2005
Year
*Keller et al. 2008 CJFAS 65: 786
See also Monteith et al. 2007 Nature 450: 537
*At >4 mg/L, Chaoborus, & thus Holopedium benefit*
3
log C. punctipennis abundance (#/m )
2.5
2.0
1.5
1.0
r = 0.32, p = 0.03
n = 49
0.5
0.0
1
10
DOC (mg/L)
*Allen 1973 Ecology 54: 484, Arnott & Vanni 1993 Ecology 74: 2361
Wissel et al. 2003 Freshwat Biol 48:1421.
# of Lakes with Bythotrephes
And Bythotrephes is spreading in Ontario*
180
150
120
90
60
30
0
1985
reviewed in Yan et al. 2011, Biol. Invas
1990
1995
2000
Year
2005
2010
2015
% occurrence of species in Bythotrephes lakes
Bythotrephes affects all daphniids except D. mendotae,
but it does not affect Holopedium
6
100
10
3,4
80
12
14
40
20
0
30,32
28,29
26
24
31
21
0
23
7
13
11
17
16
22
20
8
15,18
19,20
25,27
5
9
1:1
60
40
60
80
% occurrence of species in reference lakes
*Boudreau & Yan, 2003 CJFAS
1,2
100
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Taxa
D. b. tho
M. edax
D. mend
H. gibb
B. frey
L. min
S. oreg
D. birg
E. lacu
T. exte
D. dubi
D. long
B. long
C. scut
C. spha
D. cata
B. tub
A vern
P. ped
S. crys
So, the lakes are changing
• pH has risen modestly, but >6 in many lakes
• Ca has fallen by 25% in most lakes, often below 1.5 to 2 mg/L,
a key threshold
• TP has fallen enough so we have far fewer mesotrophic lakes
• DOC has risen by 25%, in some lakes above a likely threshold
(3 mg/L) that benefits the zooplanktivore, Chaoborus
• Bythotrephes is spreading, and when established is abundant
enough (3-5/m3) to change Cladocera
• Colonial chrysophytes have replaced diatoms (Paterson et al.
2008), and mean algal colony size has likely increased
• Most of these changes likely harm daphniids, benefiting
Holopedium; only the rise in pH should benefit daphniids
Is there evidence that falling Ca
is harmful to daphniids?
Zooplankton richness
(Crustacean Spp/lake)
[Ca] at which crustacean zooplankton richness declines in 545 Norwegian lakes,
without Bythotrephes, with pH >6, and Ca <7 mg/L.
Richness averaged in bins of 0.5 mg Ca/L width (data from B. Walseng, NINA)
N=40
108
60
N=38
89
76
Breakpoint = 2.76 mg/L
Ca (mg/L) at bin midpoint
Daphniid % Occurrence
(mean of sorted blocks of 50 lakes)
Segmented regression of mean % occurrence of Daphniids in blocks of 50 lakes vs.
Ca in 600 Norwegian lakes with pH>6. (Lakes with Bythotrephes included)
Data from B. Walseng
Average Ca (mg/L) in blocks of 50 lakes sorted by Ca
Holopedium % occurrence
(mean of sorted block of 50 lakes)
% Occurrence of Holopedium vs. Ca in 600 Norwegian, non-acid
lakes (mean for sorted blocks of 50 lakes)
Average Ca (mg/L) in blocks of 50 lakes sorted by Ca
Daphniid % Occurrence
(mean of sorted blocks of 25 lakes)
Segmented regression of Daphnia % Occurrence vs. Ca in 290
Ontario lakes sorted by Ca in a model including pH, each data
point represents the mean of 25 lakes
Breakpoint at 1.6 mg/L
o
*unpub.data from Cairns and Yan
83%
(n = 15)
19
Average Ca (mg/L) in blocks of 25 lakes sorted by Ca
20
Modelled Observed
Pattern of occurrence
For 5 of 7 daphniid taxa
with Ca in 300 lakes
Cairns & Yan in revision
Cairns
For the other 2 daphniids - D. ambigua & catawba*
there was no decline in prevalence with Ca
*A. Jeziorski. A. Cairns, and N. Yan unpub. data, all taxa reared at 2.3 mg/L of Ca
We see the same pattern over time*
Changes in Daphnia fossils from a Plastic Lake sediment core
*Jeziorski et al. 2008 Science 322: 1374-7
Do field experiments agree?
2 day replacement bioassay
• Lakes with 4 [Ca]s - 1.1, 1.3, 1.4, 2.4 mg/L
• 17 day endpoint (July-Aug ‘08)
• Transfer to new culture tubes in field
• Open treatments with or without added
food
• Closed treatment with added Ca and
Ca+food
Waste & animals examined in lab
• # of neonates
• # of exuvia
• Verify survival
Lily
Allegra
z = 2m
Temperature (oC) at 2m depth
LAKE
BK (2.28)
CN058 (1.41)
LY (1.31)
LS (1.06)
ALL
Mean
22.8
22.5
22.9
23.2
22.9
Median
22.9
22.5
22.8
23.1
22.8
Std Dev
0.33
0.41
0.45
0.41
0.47
Survival of daphniid juveniles over 17 days
in the open treatments (Cairns & Yan in prep.)
Buck Lake
Ca = 2.3 mg/L
CAISN 58 Lake
Ca = 1.4 mg/L
Lower Schufelt, Ca = 1.06
& Lynch, Ca = 1.3 mg/L
Why are we losing Daphnia
Effects of Ca & temperature on r for Daphnia pulex*
r (neonates/female•day)
Intrinsic
rate of natural increase, r (d-1)
0.6
0.5
0.4
20
0.3
24
28
0.2
0.1
0
0.1
0.5
1
1.5
Ca (mg/L)
Ashforth & Yan 2008 L&O 53: 420
2
5
10
*Are results similar in a soft-water medium,
with a lake species of Daphnia?
Intrinsic rate of natural increase (r in d-1)
0.4
0.35
20°C
23°C
0.3
26°C
0.25
0.2
0.15
0.1
0.05
0
0.5
1
1.5
2
Calcium concentration (mg L-1)
2.5
5
*21 day bioassay with D. pulicaria, in FLAMES medium (Linley, Shead & Yan, in prep.)
Why has r fallen?
Low Ca slows growth, and alters growth response to Chaoborus kairomone*
Body Length (mm)
1.5
No Kairomone
Kairomone
Instar 4
1.4
1.3
1.2
1.1
1.0
0.5
1.5
2.5
Calcium (mg/L)
*Riessen, Linley, Yan, Altshuller, Laforsch in prep
5.0
Estimates of increased vulnerability to predators
(from Riessen, Linley, Yan, Altshuller, Laforsch in prep)
Predator
Acanthocyclops
robustus 1
Heterocope
2
septentrionalis
Chaoborus
americanus 3
Daphnia
instar
Body length
reduction (%)
Increase in
vulnerability
(%)
4
15
16.3
4
15
42.4
4
17
79.6
1 - vulnerability calculated using Gliwicz & Umana (1994)
2 - vulnerability calculated using O'Brien et al. (1979)
3 - vulnerability calculated using Riessen and Trevett-Smith (2009)
Neck teeth in
Daphnia minnehaha
Photos by H. Riessen
*Does low Ca exposure alter neck teeth induction in D. pulex?
NS
100
P < 0.001
a b b b
P < 0.001
a b b b
NS
% Daphnia
80
Neck Spine:
Strong
Weak
None
60
40
Calcium (mg/L):
A = 0.5
B = 1.5
C = 2.5
D = 5.0
20
0
ABCD
ABCD
ABCD
ABCD
1
2
3
4
Instar
*Riessen, Linley, Yan, Altshuller, Laforsch in prep
Does low Ca alter carapace rigidity?
• Yes, but we are just now working with
Laforsch to quantify this effect.
How does low Ca harm daphniids?
• Directly:
– Low Ca saps energy
– Reduces body growth, delaying reproduction & r
– Reduces survival of neonates in lab and field
• Indirectly:
– Low Ca reduces normal growth response to Chaoborus
kairomone
– Reduces neck teeth production, and
– (likely) reduces carapace rigidity, thus
– Increasing vulnerability to native invertebrate predators
• And falling P, rising DOC and spreading
Bythotrephes likely exacerbate these trends
Bythotrephes has very low Ca needs*
Bythotrephes
~0.03% Ca
*Kim and Yan, CJFAS, under review
Holopedium
~0.3% Ca
Daphnia
~5% Ca
So what happens when we lose daphniids?
Functional complimentarity happens
8 long-term study lakes & 31-37 other lakes
with paleolimnological data and repeated surveys
1
2
3
4
5
6
7
8
Harp
Chub
Blue Chalk
Red Chalk
Dickie
Crosson
Plastic
Heney
1
2
3
4
8
8
5
6
7
Paleolimnological evidence for the rise of Holopedium:
Change in relative abundance of Holopedium in pelagic Cladoceran assemblage
in the top vs. bottom (pre-industrial) slices of cores of 37 lakes with Ca 1-3
mg/L, pH 5-7.
Holopedium - Recent sediments
(% of Pelagic Cladocera)
20
15
10
paired t = 2.66
p= 0.012
5
0
0
5
10
15
20
Holopedium - Pre-industrial Sediments
(% of Pelagic Cladocera)
Adam Jeziorski
Evidence from the repeat of a broad-scale survey*
Change in relative abundance of Holopedium in the planktonic Cladoceran
assemblage in 31 low Ca lakes, 5 invaded by Bythotrephes
% Holopedium in 2004-05
60
50
with Bythotrephes
without Bythotrephes
Michelle Palmer
40
30
20
10
w/o Bythotrephes, t = 2.85, p < 0.01
w Bythotrephes, t = 3.5, p = 0.02
0
0
10
20
30
40
50
% Holopedium in the 1980s
60
Trends of Holopedium relative abundance
in the 8 long-term study lakes
group 1
Blue Chalk
Crosson
Harp
Heney
Red Chalk
tau (p)
0.56 (<0.001)
0.31 (0.03)
0.46 (0.001)
0.47 (<0.001)
0.52 (<0.001
group 2
Chub
Dickie
Plastic
Group 1 – significant increase
Group 2 – no change
No lakes with falling relative abundance
tau (p)
0.08 (0.55)
0.05 (0.71)
0.11 (0.42)
Evidence from the 8 Dorset lakes
H. glacialis (% of Cladocera ± SE)
Changes in the relative abundance of Holopedium in the Cladoceran assemblage
from 1981 to 2005 in Dorset lakes, with and without a significant trend
50
40
CB, DE, PC
30
20
Handfuls of Holopedium
Plastic Lake, August, 2011
Photo by R. Ingram
10
BC, CN, HP, HY, RC
0
1980
*Yan et al. (in prep)
1985
1990
1995
Year
2000
2005
What explains the initial difference in relative
Holopedium abundance between lake-groups?
Abundance of Chaoborus (#/m3)
water quality
Holopedium
Lake
group
pH
Ca
TP
DOC C. punc
HY
RC
HP
BC
CN
PC
DE
CB
1 - low
1 - low
1 - low
1 - low
1 - low
2 - high
2 - high
2 - high
5.6
6.3
6.2
6.6
5.5
5.8
5.7
5.5
2.1
2.8
3
2.8
2.3
2
2.5
2.5
8
6
9
7
11
8
13
13
2.7
2.5
4
1.9
4.1
2.4
5.2
4.9
low
high
6.0
5.7
2.6
2.3
8.2
11.3
3.0
4.2
mean
mean
0.3
0.3
1.5
7.1
1.9
51.6
37.8
27.6
C. flav
C. triv
Total
63.9
0.3
0.3
1.5
7.1
7.4
51.6
52.4
104.6
5.5
14.6
13.1
3.3
69.6
What happened to the 5, low-Holopedium lakes
between 1980 & 2005?
•
•
•
•
•
pH rose a bit from 6 to 6.2
Ca fell by 18% to a mean of 2.1 mg/L
TP fell by 16% to 6.9 ug/L
DOC rose by 24% to 3.8 mg/L
We don’t know (yet) what happened to
Chaoborus
• Bythotrephes invaded Harp Lake
What is the proximate cause of the Holopedium rise?
Clutch and body size (± 1 SE) of Holopedium (n = 469) vs. 9 species of
Daphnia (n = 851) in 31 study lakes in 2004 and 2005*
4.5
Clutch size of gravid females
D pulicaria (48)
4.0
H glacialis
D. dentifera (52)
3.5
3.0
2.5
D ambigua (16)
D longiremus (131)
D catawba (232)
D pulex (76)
D retrocurva (52)
2.0
D mendotae (212)
D dubia (63)
1.5
0.8
1.2
1.6
2.0
Body length (mm) of gravid females
*Palmer and Yan, unpubl.
2.4
Conclusions / Hypotheses
• We have 3 independent bodies of evidence of rising
importance of Holopedium in Ontario’s Shield lakes
• Falling Ca and TP, linked to long-term watershed
acidification, rising DOC, and the spread of
Bythotrephes, may be counteracting the benefits of
rising pH, at least for the daphniids.
• The causes for the losses of daphniids and rise of
Holopedium are likely lake-specific.
Potential Implications
• Elemental food quality for pelagic consumers may
have worsened, given the low P and Ca levels in
Holopedium
• Efficiency of energy transfer in the pelagic food web
may have fallen, given the low vulnerability of jellyclad taxa to invertebrate predators
• Filter clogging issues for large water takers in softwater lakes may worsen (eg. Spotts, S.M.S and M.T Brett. 2006.
A limnological investigation of potential filter-clogging agents at the city of
Everett water filtration plant, unpubl. report, U Washington).
Potential lessons for OA researchers
• Small changes in chemistry may have huge effects on biota
• Closely related taxa may have very different Ca needs
• Causal mechanisms may be both direct and indirect, and vary in
space
• Indirect effects on growth & reproduction, or vulnerability to
predators may be more important that direct toxic effects
• Acid or low Ca stress may be compounded by nutrient stress, and
overfeeding may mask effects in experiments
• More generally it is risky to look at OA in isolation of other factors
that change food web dynamics.
• Long-term and large-scale ecological research is critical, but must be
accompanied by experiments to test hypotheses.
• A mix of research at all ecotoxicological scales (genes to the global
ocean) is needed.
• Recovery from damage is possible, if appropriate action is taken.
Acknowledgements
• Personnel at the MOE’s Dorset Environmental
Science Centre
• NSERC for funding
• Many summer students and technicians at the
DESC, Queen’s and York
• Howard for the invitation