Hydrodynamic control of benthic mats of <i>Didymosphenia geminata</i> at the reach scale

Cullis, James; McKnight, Diane M.; Spaulding, Sarah A.

doi:10.1139/cjfas-2014-0314

Cited by 23 publications

(20 citation statements)

References 40 publications

(13 reference statements)

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“…The putative threshold DRP concentration of 2 mg m À3 , below which D. geminata proliferations develop, is consistent with some observations of proliferations in North and South America, as well as New Zealand (e.g. Miller et al, 2009;Reid & Torres 2014, Cullis, McKnight & Spaulding, 2015. However, D. geminata proliferations in Europe have been observed in rivers with average DRP concentrations substantially higher than 2 mg m À3 (e.g.…”

Section: Introductionsupporting

confidence: 88%

“…Miller et al, 2009;Reid & Torres 2014, Cullis, McKnight & Spaulding, 2015. Miller et al, 2009;Reid & Torres 2014, Cullis, McKnight & Spaulding, 2015.…”

Section: Introductionmentioning

confidence: 99%

“…A third objective was to determine whether reductions in D. geminata abundance associated with nutrient enrichment can be caused by competitive exclusion by other algal taxa, rather than direct effects of enrichment (Cullis et al, 2012(Cullis et al, , 2015Richardson et al, 2014). We measured the effects of N and P enrichment on two phases of D. geminata development, initial growth following colonisation and established mats.…”

Section: Introductionmentioning

confidence: 99%

“…We measured the effects of N and P enrichment on two phases of D. geminata development, initial growth following colonisation and established mats. A third objective was to determine whether reductions in D. geminata abundance associated with nutrient enrichment can be caused by competitive exclusion by other algal taxa, rather than direct effects of enrichment (Cullis et al, 2012(Cullis et al, , 2015Richardson et al, 2014). We therefore evaluated the responses of other benthic algal taxa to the experimental treatments.…”

Section: Introductionmentioning

confidence: 99%

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Contrasting effects of low‐level phosphorus and nitrogen enrichment on growth of the mat‐forming alga Didymosphenia geminata in an oligotrophic river

Kilroy

Larned

2016

Freshwater Biology

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Summary The stalked diatom Didymosphenia geminata forms proliferations of stalk‐dominated mats in rivers. Over its range in New Zealand, mats rarely occur where average dissolved reactive phosphorus (DRP) concentrations exceed ~2 mg m−3, but do occur in rivers with dissolved inorganic nitrogen (DIN) concentrations up to ~250 mg m−3. Previous studies indicated that low DRP concentrations limit D. geminata cell division and stimulate stalk production and mat development, even at very low ambient DIN concentrations (~10 mg m−3). We ran two nutrient‐enrichment experiments in instream channels in an oligotrophic river with a persistent D. geminata proliferation to (i) test the hypothesis that elevated DRP concentrations reduce or prevent mat development by reducing stalk production; and (ii) investigate the effect of DIN enrichment on D. geminata growth and mat development. In Experiment 1, treatments comprised low‐level enrichment with DRP (to 1.6 mg m−3, from superphosphate fertiliser), DIN (to 13.5 mg m−3, from ammonium sulphate), and both DRP and DIN. Compared to unenriched controls, DIN and DRP enrichment enhanced D. geminata cell densities, biomass, cell division (frequency of dividing cells), stalk biovolume and percentage cover of mats, indicating both N‐ and P limitation for all growth metrics. In the DRP‐enriched treatments, biomass accrual may have been stimulated rather than reduced as predicted because DRP concentrations did not exceed the putative 2 mg m−3 threshold. In Experiment 2, we expanded the range of DRP enrichment using additions of orthophosphate as well as superphosphate, and added DIN to all treatments. Higher DRP concentrations (up to 4 mg m−3) initially enhanced D. geminata growth. By the end of the experiment, D. geminata‐dominated biomass in the orthophosphate treatments was lower than in the superphosphate or DIN‐only treatments. Outflows from the experimental channels caused slight nutrient enrichment in the river downstream. During Experiment 1, this DRP and DIN enrichment had no detectable effect on D. geminata standing crop on the riverbed. During Experiment 2, D. geminata standing crop downstream of the experiment declined relative to the unenriched area upstream. The specific mechanism linking P enrichment to D. geminata biomass decline is unclear. In the experimental channels there was evidence for a predominance of cell division over stalk production in orthophosphate treatments, as hypothesised. In the river, we observed higher rates of sloughing in the river downstream of the experiment than upstream. There was no evidence that competition from other algal taxa reduced D. geminata standing crop. The results supported the hypothesis that DRP enrichment at concentrations over ~2 mg m−3 leads to reduced D. geminata biomass and % cover in this river. However, biomass reduction occurred only when DRP was added as orthophosphate, not as superphosphate. N limitation of D. geminata growth in river water with ambient mean DIN concentrations below ~6 mg m−3 suggests that D. geminata pr...

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Section: Introductionsupporting

confidence: 88%

“…Miller et al, 2009;Reid & Torres 2014, Cullis, McKnight & Spaulding, 2015. Miller et al, 2009;Reid & Torres 2014, Cullis, McKnight & Spaulding, 2015.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Contrasting effects of low‐level phosphorus and nitrogen enrichment on growth of the mat‐forming alga Didymosphenia geminata in an oligotrophic river

Kilroy

Larned

2016

Freshwater Biology

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“…Rapids may render unsuitable conditions due to high shear stress and higher frequency of bed load transport causing mat scouring whereas light availability is limited in deeper pools. This result supports previous observations that geomorphological units define physical habitat suitability for mat colonization and growth (Cullis, Spaulding, & McKnight, 2015;Miller et al, 2009). Runs and riffles offer optimal conditions for D. geminata colonization, mat development, and persistence due to their shallow depths, high light availability, and stable substrate between high discharge events.…”

Section: Discussionsupporting

confidence: 92%

Effect of discharge and habitat type on the occurrence and severity of Didymosphenia geminata mats in the Restigouche River, eastern Canada

2018

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Since 2006, the Restigouche River watershed, eastern Canada, has been affected by nuisance growths of the mat‐forming diatom, Didymosphenia geminata. In 2010, in view of the potential impacts of this alga on the local Atlantic salmon fishery, we created a volunteer monitoring network to assess D. geminata mat severity within the watershed. Over the course of 6 monitoring summers, more than 1,200 observations of D. geminata mat severity were reported in 20 subwatersheds of the Restigouche River basin. Observations were mapped to illustrate the yearly severity of D. geminata mats throughout the watershed. Metrics were then extracted from this dataset to assess the spatial and temporal variability of mat severity. At the reach scale, D. geminata occurrence was predominantly found in riffles compared to any other river habitat type. At the watershed scale, a two‐sample Kolmogorov–Smirnov test highlighted a significant effect of maximum spring discharge on mean annual D. geminata mat severity, indicating that when maximum spring discharge is high, severity of D. geminata mats in the following months is significantly lower. Additionally, maximum spring discharge explained 71% of the variability in annual mat severity. This study contributes to the understanding of mat severity dynamics and illustrates the value of volunteer monitoring networks for studying complex ecosystem dynamics.

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Potential for real‐time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams

McKnight

Cozzetto

Cullis³

et al. 2015

Water Resources Research

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While continuous monitoring of streamflow and temperature has been common for some time, there is great potential to expand continuous monitoring to include water quality parameters such as nutrients, turbidity, oxygen, and dissolved organic material. In many systems, distinguishing between watershed and stream ecosystem controls can be challenging. The usefulness of such monitoring can be enhanced by the application of quantitative models to interpret observed patterns in real time. Examples are discussed primarily from the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica. Although the Dry Valley landscape is barren of plants, many streams harbor thriving cyanobacterial mats. Whereas a daily cycle of streamflow is controlled by the surface energy balance on the glaciers and the temporal pattern of solar exposure, the daily signal for biogeochemical processes controlling water quality is generated along the stream. These features result in an excellent outdoor laboratory for investigating fundamental ecosystem process and the development and validation of process-based models. As part of the McMurdo Dry Valleys Long-Term Ecological Research project, we have conducted field experiments and developed coupled biogeochemical transport models for the role of hyporheic exchange in controlling weathering reactions, microbial nitrogen cycling, and stream temperature regulation. We have adapted modeling approaches from sediment transport to understand mobilization of stream biomass with increasing flows. These models help to elucidate the role of in-stream processes in systems where watershed processes also contribute to observed patterns, and may serve as a test case for applying real-time stream ecosystem models.

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Hydrodynamic control of benthic mats of Didymosphenia geminata at the reach scale

Cited by 23 publications

References 40 publications

Contrasting effects of low‐level phosphorus and nitrogen enrichment on growth of the mat‐forming alga Didymosphenia geminata in an oligotrophic river

Contrasting effects of low‐level phosphorus and nitrogen enrichment on growth of the mat‐forming alga Didymosphenia geminata in an oligotrophic river

Effect of discharge and habitat type on the occurrence and severity of Didymosphenia geminata mats in the Restigouche River, eastern Canada

Potential for real‐time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams

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