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Macroinvertebrate size‐distributions of two contrasting freshwater macrophyte communities
Author(s) -
HANSON JOHN MARK
Publication year - 1990
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1990.tb00726.x
Subject(s) - chara , macrophyte , biomass (ecology) , biology , invertebrate , aquatic plant , ecology , myriophyllum , algae , botany , potamogeton
SUMMARY.1 Macroinvertebrates (>0.1 mg, fresh weight) were collected every 2 weeks for 18 weeks from weedbeds dominated by either the macroalga Chara or rooted plants (mostly Isoetes sp., Potamogeton filiformis, Nuphar variegatum and Myriophyllum exalbescens) in Narrow Lake, Alberta, Canada. Significant differences in total biomass, taxonomic composition, and size‐structure of the macroinvertebrate community were found between the two weedbed types. 2 Total biomass of macroinvertebrates in the Chara beds (seasonal mean 26.4 g m −2 ) was consistently higher than in the rooted‐plant weedbeds (seasonal mean 7.6 g m −2 ). 3 The macroinvertebrate community of the Chara beds was dominated by chironomids, anisopterans, gastropods and sphaerid clams whereas amphipods dominated the community in the rooted‐plant weedbeds. 4 On average, the proportion of total biomass in the various size‐classes (biomass size‐spectrum) of the macroinvertebrate community in Chara beds varied very little between 1 and 512 mg. In rooted plant weedbeds, the spectrum showed a strong peak in the 4–8 mg size‐class, a weak peak in the 32–64 mg size‐class, and proportionately low biomass in the 128–256 mg and 256–512 mg size‐classes. The slope of the normalized size‐spectrum for the macroinvertebrate community of the Chara beds (‐0.89) was significantly different from that of the rooted plant community (‐1.11). The biomass of large organisms (>64 mg) was 10 times greater in the Chara beds than in the rooted‐plant weedbeds. 5 The species composition of aquatic macrophyte beds can greatly influence the abundance, taxonomic composition, and size‐structure of the littoral zone macroinvertebrate community. Therefore, any changes in plant species composition of weedbeds, through introduction of exotic plant species or introduction (or loss) of an efficient grazer (e.g. crayfish), have the potential to alter greatly the structure of the macroinvertebrate community in a lake, with unknown consequences to fish and waterfowl dependent upon these prey.