Aqernt. Sci., Vol. 51, 1994. Can. J. Fish. Aquat. Sci. Downloaded from www.nrcresearchpress.com by Laurentian University on 03/22/15. For personal use only.
Crustacean Zoop ankton Communities and Lake Morphometry in Precambrian Shie W. Keller and M. ~ o n l o n ' Can. J. Fish. Aquat. Sci. Downloaded from www.nrcresearchpress.com by Laurentian University on 03/22/15 For personal use only.
Cooperative Freshwater Ecology Unit, Ontario Ministry of Environment and Energy, 799 Larch Street, Sudbury, ON P3E 5P9, Canada
Keller, W., and M. Conlon. 1994. Crustacean zosplankton communities and lake morphometry i n Precambrian Shield lakes. Can. j. Fish. Aquat. Sci. 51 : 2424-2434. To investigate relationships between crustacean zooplankton communities and lake rnorphometry we sampled 60 near-neutral Precambrian Shield lakes, including many small, shallow lakes. Morphometry-related patterns in the distributions of naany zooplankton species were evident. Lake depth determined the occurrence of hypolimnetic species, and lake depth, lake area, and watershed area were positively related to the species richness of zooplankton communities. Among lakes with fish, deeper (maximum depth >8 m) Bakes were characterized by greater species richness, higher abundances of a number of species including Daphnia pulex, Daphnia gafeata mendstae, Daphnia dubia, and DiacycBops bicuspidatus thornasi, and lower abundances of heptsdiaptomus minutus, than shallower (maximum depth 8 m). The division into these depth categories was based on the evidence of a discontinuity in species richness at -8 m (Fig. 2). These depth categories also served to roughly divide lakes among those expected to be dsminated by smaller and larger fish species, and those expected to show some thermal stratification or no stratification (W. KeBler, personal observations). A number of species showed differences in relative occurrence between these lake groups (Table 5). Considering only zooplankton species that showed at least a 10% difference in occurrence between the two lake depth groups, D.pubex, D. brachyururn, D. g . anenhdotae, 8. dubia, D. b. thomcksi, D. longireraaks, E. long ispina, Eeptodora kindtik, .Ye cwlawraeoide.~, M . e h x , P! pedkcubus, and C. scletifer were more common among deeper lakes, while E. nainutus, H. gibberurn, Ha. birgei, and A. leprspus had increased occurrence among Can. 9. Fish. Aquac. Sci.,
Vol. 51, 1994
TABLE4. Varimax rotated factor matrix of zooplankton species abundances with the first four principal components, for the Algorna study lakes. Only species occurring in >I040 of the lakes are considered. For full species names see Table 2.
Principal component"
Can. J. Fish. Aquat. Sci. Downloaded from www.nrcresearchpress.com by Laurentian University on 03/22/15 For personal use only.
Taxa
PC1
T. extensus H . gibberlent M aedax Cyclopoid copepodids B. loaagir~pifris D. b. thornasi B. l~ngiremis D.dubia D. g. rnendotue A. Eeptopus B. brachyurutn L. mn'nulus 0.modestus Cyclopoid nauplii D.p u l a D. hirgei E. lacustris D. rerrocurva Calanoid copepodids E. I~pegi~ppiv~a S. sregonensis Calanoid nauplii Eigenvalue % variance explained Cumulative percent
PC2
PC3
PC4 0.10 0.25 -0.11 0.25 0.05 0.30 0.04
2.25 10.2 45.4
2.08 9.8 54.6
3.50 15.9 35.2
"Environmental variables with significant (Pearson r, p < 0.05) correlations with principal component factor scores were: PC1, chlsasphyll a (r = 0.33); PC2, Iake depth (r = 0.42), watershed m a (r = 0.34), lake area (r = 8.311, ~ecchi(0.291, C. arnericanw (r = -0.26), DOC (r = -0.25); PC3, C- americanus ( r = 0.431, Ca ( r = -0.351, conductivity (r = -0.34), pH ( r = -0.33), watershed area (r -0.33), lake area (r = -0.22). There were no significant ( p < 0.05) environmental correlates with PC4. b ~ o a d i n g> 0.5; loadings are correlations between species and components after orthogonal rotation. -
3 2
0.86' -0.02 0.04 0.75~ -0.15 0.06 0 . 6 8 ~ 0.10 0.31 0 . 6 8 ~ 0.45 0.08 -0.19 0.55' -0.13 -0.01 0 . 8 9 ~ -0.05 -0.09 0 . 7 6 ~ -6.05
4.24 19.3 19.3
4
1
A A
0
-1
.
-
shallower lakes (Table 5). Considering abundance, L. minutus had higher abundance ( p < 0.05) in shallower lakes, while a number of species, including D.pulex, D. g. naelzdotae, D. d ~ b i a and , D. b. thomasi, as well as several hypolirnnetic species, had higher abundances in deeper lakes (Table 6). The environmental variables dissolved organic carbon (DOC), AI, and total phosphorus (TP) were higher ( p < 8.05) in concentration in shallower lakes, while lake area, watershed area, and Secchi transparency were Bower ( p < 0.05) (Table 7). Lakes inferred to be fishless based on the presence of C. anlericanus had the highest percent occkrrences of T. extensus, D. pulex, 8. brachyurntrn, A. leptopus, 0. modesbus, H. gibberurn, and S. cr.ysta!kina, and conspicuous absences of D. birgei, D. b. thornasi, D. g. rnelzdotae, sand hypolimnetic species (Table 5). They differed from shallower lakes by having higher (p < 0.05) abundances of D.pulex, D. brachyururn,, S. crystallina, and A. lepbogus and an absence of D. birgei. Fishless lakes also had higher abundances of a number of specles, particulary A. legtopus, Can. J . Fisiz. Aquut. Sci., Vol. 51, 1994
FIG. 3. Relationship between lake factor scores for (a) PC1 and PC2 and (b) PC2 and PC3 for the Algoma study lakes.
S. crystalkina, and D. brachyururn, and lower abundances of D. dubia, than deeper lakes (Table 6). Fishless lakes had lower ( p < 0.05) chlorophyll a, watershed area, and pH than shallower lakes. They had lower ( p < 0.05) depth, lake area, watershed area, and pH than deeper lakes (Table 7 ) . Species richness was lower (g < 0.05) in shallower lakes and fishless lakes than in deeper lakes. There was no difference ( p > 0.05) in species richness between shallower lakes and fishless lakes.
Discussion Overall, the Algoma study lakes contained a zooplankton species assemblage (Table 2) that was similar to lakes in other regions of Ontario. Of the 28 species present in the Algorna lakes, 26 species occurred in surveys of 161 lakes in northeastern Ontario and 137 lakes in northwestern Ontario (Keller and Pitblado 1989; lakes with pH > 6.0 only). The total number of species collected in the Algoma lakes (28) was slightly lower than the total numbers of species collected by Keller and Pitblado (1989) in surveys of northeastern 2429
TABLE5 . Percent occurrence of crustacean zooplankton species within groups of 'Veep" (>8 m), 66sshdlow"(c7 Secchi ( r n ) " ~ ~ DOC (nng-L-I)" TP ( p g - ~ - 9 ' Chl a ( p g - ~ - ' ) b p~b*c
Conductivity (FS-cm- ') Calcium (rng.~-') Aluminum (pg~L-')" "Significant (p < 0.05) difference between "deep" and "shallow" Bakes. b~ignificant( p < 0.05) difference between "shallow" and "fishless" lakes. "Significant ( p < 0.05) difference between "deep" and "fishless" lakes. d~ecchidisc visible to bottom in some shallow lakes. were rarely or never collected from lakes
