Seasonal and diel periodicity in the drift of aquatic insects in a subtropical Florida stream

Abstract

A study of insect drift was conducted in a small, subtropical Florida stream from December 1971 to December 1972 to describe the seasonal and diel periodicity and to determine factors influencing behavioural drift. Paired samples of 2h duration beginning 15 min after sunset were taken biweekly, and hourly collections over a 24-h period were made quarterly. Benthic invertebrates were collected on each date from three habitats (riffle, pool and aquatic vegetation) and temperature, dissolved oxygen and current velocity were measured. Drift rates ranged from 100 ro 2125 organistiisjm^.h (003 to 0-49 organisms!m'^} (^"d were greatest in winter and early spring; minimal rates occurred in the summer months. The following six taxa, in order of relative abtmdance, comprised 87% of the drift: Baetis intercalaris, Cheumatopsyche sp., Stenonema exiguum, Chironomidae, Stenelmis fuscata and Simulium sp. Total drift showed no significant correlation with temperature, dissolved oxygen or mean benthic abundance and only slight correlation with cttrrent velocity (r=0'34). Stepwt'se, multiple regression analyses indicated that riffle density and mean size of drifting organisms were important factors influencing the drift rates of B. intercalaris (R=0-61) and S. exiguum (R = 0-82); mean size, riffle density and water temperature influenced the drift of Cheumatopsyche sp. (R = O-1S). The other taxa of drifting insects showed no significant correlation with the variables measured. Diel (24 h) studies of the major taxa showed marked differences in the periodicity, both within and between taxa, indicating the need for long-term sttidies with freqtient sample intervals in subtropical habitats. A new drift pattern for the family Chironomidae, alternans type, was observed for late instars of Folypedilum halterale.

Effects of flow fluctuations on the daily and seasonal drift of invertebrates in a tropical river

“…However, we found higher drift densities in the dry winter season than in the wet summer season (Fig. 3(A)), corroborating the findings of Cowell and Carew (1976) and Schreiber (1995). Furthermore, we observed significant differences in taxonomic composition between seasons (Fig.…”

“…2). We believe that different life history patterns related to the marked differences in environmental conditions (e.g., temperature, photoperiod, patterns of allochtonous input) found between the seasons are probably responsible for the differences in seasonal drift patterns that we observed (Cowell and Carew, 1976). The main difference between wet and dry seasons was the density of Simuliidae.…”

“…The entry of invertebrates into the water column may result from several factors (Cowell and Carew, 1976), including accidental dislodgement from the substratum (Poff and Ward, 1991), interaction with other invertebrates and predators (Huhta et al, 2000), and changes in water quality, discharge and current velocity (Brittain and Eikeland, 1988).…”

Benthic invertebrate colonization: source distance effects on community composition

“…It is most likely that formation of new islands (i.e. channel reconstruction and restoration) would occur during summer months, periods of high invertebrate drift (Cowell & Carew 1976;Stoneburner & Smock 1979). Little contribution from upstream migration would occur until several months after water was flowing in the channel.…”

Trout predation and the size composition of stream drift 1

“…Although neither of these taxa is immune from predation, they appear to suffer markedly lower predation pressure than do larger invertebrates. In an intriguing study of a subtropical stream in Florida, Cowell and Carew (1976) found a shift from no periodicity to nocturnal drifting in PolypediZum haterale when late instars predominated. Anderson and Lehmkuhl (1968) found the mean weight of drifting individuals in four groups (Chironomidae, Baetis, Paraleptophlebia, Capnia) to be greater by night than by day.…”