Dl. Nielsen et al., Effects of hydrological variation and planktivorous competition on macroinvertebrate community structure in experimental billabongs, FRESHW BIOL, 42(3), 1999, pp. 427-444
1. To study two factors which are predicted as causing changes to community
structure in cut-off meanders (colloquially known in Australia as billabon
gs, a term of aboriginal origin), 16 experimental billabongs were construct
ed. These were designed to test two hypotheses: (a) that the structure of m
acrophyte and invertebrate communities within billabongs is altered by chan
ging the pattern of flooding; and (b) that the presence of small planktivor
ous fish alters invertebrate community structure and diversity within billa
bongs.
2. An increase in the duration of flooding seems to favour animals better a
dapted to a greater availability of macrophyte habitat. Changing the season
ality of flooding resulted in prolonging of the time water was available ov
er the summer months.
3. The presence of a planktivorous fish appears to affect macroinvertebrate
communities through competition with other planktivores. Variable top-down
pressure may create differing successional patterns and ultimately differe
nt communities at lower trophic levels.