ISSN:
1573-5117
Keywords:
algae
;
benthic
;
geothermal
;
macroinvertebrates
;
stream
;
thermal
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m−2 at 52 °C to less than 0.1 g m−2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures. Macroinvertebrates were absent at temperatures ⩾45 °C; the highest density (〉 150 000 m−2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m−2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature ‘buffer’ is maintained.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00008935
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