5. Lipid Dietary Dependencies in Zooplankton
101
TABLE 5.5. Results of dietary supplement experiments with Daphnia pulicaria from
Lake Waynewood (August 1989).a
Clutch size
Treatment
n
X
Control
14
4.7
+Lo-EFA
12
4.7
+Hi-EFA
14
4.3
+Lo-Protein
14
4.4
+Hi-Protein
14
6.8
+Hi-EFA +Lo-Protein
15
5.9
+Algae
15
5.6
Source of variance
df
SS
EFA
2
0.595
Protein
2
44.846
EFA * Protein
3.124
+Algae
5.143
Error
87
563.917
SD
2.0
2.6
2.6
2.6
2.7
2.4
3.2
P
NS
.04
NS
NS
a+Algae, A. Jalcatus; EFA, essential fatty acids; NS, not significant. Clutch size analyzed by two-way
ANOVA (SAS). Interaction with all lipid or protein treatments. The lake adult population at the time of
the experiment had a mean length of 1.8 mm and a mean clutch size of 2.06 (SD, 0.68 eggs).
senting a smaller protein addition (Lowry assays), was intermediate between the
control and the protein treatments and not statistically distinguishable from either.
5.3.2. Lake Waynewood Experiment: October 1989
5.3.2.1. Algal Diet
At the time of the October microcapsule experiment in Lake Wayne wood, the
algae in that eutrophic lake were dominated by two colonial cyanobacteria,
Gomphosphaeria nageliana and Aphanizomenon flos-aquae, which were not
perceptibly grazed (Table 5.6). Several other colonial forms, including Synura
petersenii, were grazed at low rates. Grazing rates were highest on small flagellates (~20-50 mi· daphniid- I • d- I ), including Cryptomonas marssonii (18
ml . daphniid - 1 . d -I) (Fig. 5.1). Cryptomonas was relatively abundant and contributed the largest part (40%) to the total volume of ingested algae.
Nutrient enrichment assays suggested that the phytoplankton as a whole was
not limited by N or P, or the combination ofN with P. After 3 d, algal chlorophyll a
and 4-h 14C uptake were uniform across all nutrient treatments lacking Daphnia
(P >.2 from one-way ANOVA) as well as across treatments with Daphnia (separate one-way ANOVA, P >.2). Grazing slightly reduced both chlorophyll a and
14C uptake. These results for the whole algal community, which was dominated by
inedible types, are not presented in detail. Cell counts and autoradiography
101
TABLE 5.5. Results of dietary supplement experiments with Daphnia pulicaria from
Lake Waynewood (August 1989).a
Clutch size
Treatment
n
X
Control
14
4.7
+Lo-EFA
12
4.7
+Hi-EFA
14
4.3
+Lo-Protein
14
4.4
+Hi-Protein
14
6.8
+Hi-EFA +Lo-Protein
15
5.9
+Algae
15
5.6
Source of variance
df
SS
EFA
2
0.595
Protein
2
44.846
EFA * Protein
3.124
+Algae
5.143
Error
87
563.917
SD
2.0
2.6
2.6
2.6
2.7
2.4
3.2
P
NS
.04
NS
NS
a+Algae, A. Jalcatus; EFA, essential fatty acids; NS, not significant. Clutch size analyzed by two-way
ANOVA (SAS). Interaction with all lipid or protein treatments. The lake adult population at the time of
the experiment had a mean length of 1.8 mm and a mean clutch size of 2.06 (SD, 0.68 eggs).
senting a smaller protein addition (Lowry assays), was intermediate between the
control and the protein treatments and not statistically distinguishable from either.
5.3.2. Lake Waynewood Experiment: October 1989
5.3.2.1. Algal Diet
At the time of the October microcapsule experiment in Lake Wayne wood, the
algae in that eutrophic lake were dominated by two colonial cyanobacteria,
Gomphosphaeria nageliana and Aphanizomenon flos-aquae, which were not
perceptibly grazed (Table 5.6). Several other colonial forms, including Synura
petersenii, were grazed at low rates. Grazing rates were highest on small flagellates (~20-50 mi· daphniid- I • d- I ), including Cryptomonas marssonii (18
ml . daphniid - 1 . d -I) (Fig. 5.1). Cryptomonas was relatively abundant and contributed the largest part (40%) to the total volume of ingested algae.
Nutrient enrichment assays suggested that the phytoplankton as a whole was
not limited by N or P, or the combination ofN with P. After 3 d, algal chlorophyll a
and 4-h 14C uptake were uniform across all nutrient treatments lacking Daphnia
(P >.2 from one-way ANOVA) as well as across treatments with Daphnia (separate one-way ANOVA, P >.2). Grazing slightly reduced both chlorophyll a and
14C uptake. These results for the whole algal community, which was dominated by
inedible types, are not presented in detail. Cell counts and autoradiography