Ea. Smiley et Aj. Tessier, ENVIRONMENTAL GRADIENTS AND THE HORIZONTAL DISTRIBUTION OF MICROCRUSTACEANS IN LAKES, Freshwater Biology, 39(3), 1998, pp. 397-409
1. The assemblage of suspension-feeding microcrustaceans in lakes chan
ges along a habitat gradient from nearshore to offshore. This gradient
of microcrustaceans was explored in relation to differences in macrop
hytes and the associated changes in water chemistry, food resources an
d types of predators. 2. Some microcrustacean species were littoral or
limnetic specialists, while others changed their distribution along t
his horizontal habitat gradient on a diel or seasonal basis. Distribut
ion patterns were similar in a lake and a pond which differed in exten
t of macrophyte habitat. 3. There was a large shift in the composition
of sestonic food, indicating heterotrophic seston nearshore and more
autotrophic seston offshore. Sit-and-wait predators of microcrustacean
s (e.g. Enallagma spp.) dominated nearshore and cruising predators (e.
g. Leptodora kindtii Focke) were more common offshore. 4. A reciprocal
transplant experiment revealed that littoral specialists could surviv
e equally well when fed littoral or limnetic seston, while limnetic sp
ecialists performed poorly when fed littoral seston. Food resources ma
y be important in determining where some microcrustacean species live
along this horizontal habitat gradient.