ISSN:
1573-5117
Keywords:
artificial substrates
;
microcosms
;
riffle insects
;
substrate selectivity
;
toxicity testing
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The purpose of this study was to determine which of the following artificial stream designs would be most logistically simple yet effective in maintaining riffle insects during a 30 d bioassay: 1) static and no current (S-NC); 2) flow-through and no current (FT-NC); 3) static with current (S-C); or 4) flow-through with current (FT-C). Flow-through and current, when provided, were 12 ml min−1 and 30 cm sec−1, respectively. Streams were covered by emergence traps, and daylight equivalent lights provided a natural photoperiod. The four stream designs were evaluated in triplicate based on changes in insect species-abundances after 30 d. Test organisms were transferred to the artificial streams in rock-filled containers previously colonized for 30 d in a third-order mountain stream riffle. Additional colonized substrates were sampled immediately to provide an estimate of initial densities placed in the artificial streams. Hess samples were taken directly from the source riffle to evaluate how well the artificial substrates reflected species-abundances on the natural substrate. Adults were collected from the artificial streams every 48–72 h to determine the percentage of initial densities that emerged. After 30 d (7 Aug–6 Sept, 1986), all organisms remaining in the streams were censused. Designs were evaluated using combined densities of adults and young. Relative to benthic samples taken directly from the source riffle, the artificial substrates selected for collector-filterers and against collector-gatherers. The FT-C and S-C stream designs maintained most taxa at or above initial densities, and even in the FT-NC and S-NC streams densities of some taxa were not significantly different (P ≤ 0.05) from initial densities. Emergent adults comprised a large proportion of mayfly and chironomid densities and must be monitored during bioassays with aquatic insects. These results indicate that microcosms of riffle insect communities can be maintained for at least 30 d with moderate current and minimal flow-through.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00008474
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