ID:
publications-1169
Type:
PEER REVIEWED ARTICLE
Year:
2017
Authors:
Ărika M. Neif , Daniel Graeber , Liliana Rodrigues , Simon RosenhĂžj-Leth , Tinna M. Jensen , Peter Wiberg-Larsen , Frank Landkildehus , Tenna Riis ,
Title:
Responses of benthic algal communities and their traits to experimental changes in fine sediments, nutrients and flow
Venue/Journal:
DOI:
10.1111/fwb.12965
Research type:
Uncategorized
Water System:
River Basins
Technical Focus:
Abstract:
Summary Lowland stream ecosystems are subjected to multiple anthropogenic stressors, usually nutrient enrichment in combination with sedimentation of fine particles and low flow periods in summer. Here, we investigated the temporal development of the benthic algae community in response to these three stressors and linkages to the trait characteristics of the community to explore the mechanisms responsible for stressâinduced community changes. We investigated the response of benthic algae species composition, traits (life forms, cell size categories), biovolume and chlorophyll a (Chlâa) concentration to low flow in combination with nutrient enrichment and fine sedimentation in twelve large outdoor stream flumes (12 m long) resembling small streams in size and habitat characteristics. The experiment consisted of two phases: a normalâflow phase followed by a lowâflow phase (90% current velocity reduction), each spanning 4 weeks. We applied a eutrophication scenario (mean increases of 1.14â5.48 mg N/L and 0.01â0.06 mg P/L in the flumes for dissolved inorganic nitrogen and phosphate respectively) throughout the experiment. Under low flow, we supplemented this with a fine sedimentation scenario (>90% stream bed cover). We took samples once in the normalâflow phase and every week during the lowâflow phase. We observed strong responses in the benthic algae community to sudden changes in low flow and fine sedimentation, mediating rapid species turnover with a decreased algal biovolume and increased abundance of large, motile species. However, we did not observe any pronounced responses to nutrient enrichment. In contrast to the observations for other variables, we found a continuous increase in Chlâa concentration during low flow. This was likely due to continuous fine sedimentation during this phase, reducing light availability which probably resulted in an increase of cellâlevel Chlâa concentration in response to light limitation and lower rates of lightâinduced Chlâa degradation. The rapid response of the benthic algal community to the applied stressors suggests that even short periods of major stressor exposure may significantly affect benthic algae in lowland systems. We suggest that shortâterm stress events may have cascading effects on several important ecosystem processes given the importance of benthic algae for the productivity of these systems.
Link with Projects:
603378
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