The contribution of epipelon to total sediment microalgae in a shallow temperate eutrophic loch (Loch Leven, Scotland) |
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Authors: | B M Spears L Carvalho R Perkins M B O’Malley and D M Paterson |
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Institution: | (1) Centre for Ecology and Hydrology Edinburgh, Penicuik, Midlothian, EH26 0QB, Scotland, UK;(2) School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE, Wales, UK;(3) Sediment Ecology Research Group, Scottish Oceanographic Institute, University of St. Andrews, St. Andrews, Fife, KY16 8LB, Scotland, UK |
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Abstract: | Benthic microalgae are known to perform important ecosystem functions in shallow lakes. As such it is important to understand
the environmental variables responsible for regulating community structure, positioning and biomass. We tested the hypothesis
that the positioning (across a depth gradient of 2–22 m overlying water depth) and relative biomass (determined using bulk
and lens tissue harvested chlorophyll (Chl) a concentrations) of the epipelon community would vary independently with season (12 monthly samples) and across natural gradients
of light and habitat disturbance relative to the total benthic algal community (i.e. all viable microalgae in the surface
sediments) in a shallow eutrophic loch. Total sediment microalgal Chl a concentrations (TS-Chl; range: 5–874 μg Chl a g−1 dw) were highest in winter and in the deepest site (20 m overlying water depth), apparently as a result of phytoplanktonic
settling and sediment focussing processes. Epipelic Chl a concentrations (Epi-Chl; range: <0.10–6.0 μg Chl a g−1 dw) were highest in winter/spring, a period when water clarity was highest and TS-Chl lowest. Principal components analysis
highlighted strong associations between Epi-Chl and sites of intermediate depths (2.5–5.5 m) in all seasons except autumn/winter.
Autumn/winter represented the season with the highest average wind speeds preceding sampling, during which the highest Epi-Chl
concentrations were associated with the deepest sites. Epi-Chl was associated with intermediate light and habitat disturbance
during spring/summer and summer/autumn and varied positively with habitat disturbance, only, in autumn/winter and winter/spring.
The epipelon community structure also varied with depth; diatoms dominated shallow water sediments, cyanobacteria dominated
deep water sediments, and sediments at sites of intermediate depth returned the highest biovolume estimates and the most diverse
communities. This study has strengthened the hypothesis that the structure and biomass of benthic microalgal communities in
lakes are regulated by habitat disturbance and water clarity, both of which are expected to respond to climate change and
eutrophication. The degree to which these structural responses reflect functional performance requires clarification. |
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