Effects of beaver impoundments on dissolved organic matter quality and biodegradability in boreal riverine systems

Catalán, Núria; Ortega, Sonia Herrero; Gröntoft, H.; Hilmarsson, Torfi Geir; Bertilsson, Stefan; Wu, Pianpian; Levanoni, Oded; Bishop, Kevin; Bravo, Andrea G.

doi:10.1007/s10750-016-2766-y

Cited by 23 publications

(28 citation statements)

References 44 publications

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“…Previous studies showed that impoundment establishment modifies the sources and the biodegradability patterns of riverine NOM (Catalán et al ). Moreover, the role of molecular composition of NOM on Hg(II) methylation processes in boreal lake sediments has been recently highlighted (Bravo et al ).…”

Section: Resultsmentioning

confidence: 99%

High methylmercury formation in ponds fueled by fresh humic and algal derived organic matter

Ortega

Catalán

Björn

et al. 2017

Limnology & Oceanography

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Neurotoxic methylmercury causes adverse effects to ecosystem viability and human health. Previous studies have revealed that ponding alters natural organic matter (NOM) composition and increase methylmercury concentrations in rivers, especially in the first years after flooding. Here, we investigate the influence of NOM composition (i.e., sources and degradation status) on mercury methylation rate constants in nine boreal beaver ponds of different ages across Sweden. We show that increased methylmercury concentrations in surface waters is a consequence of enhanced mercury methylation in the pond sediments. Moreover, our results reveal that during the first years after the initial flooding, mercury methylation rates are fueled by the amount of fresh humic substances released from the flooded soils and by an increased production of algal-derived NOM triggered by enhanced nutrient availability. Our findings indicate that impoundment-induced changes in NOM composition control mercury methylation processes, causing the raise in MeHg levels in ponds. Scientific Significance StatementPonds are the most abundant type of aquatic ecosystem at boreal, subarctic, and artic latitudes. Accelerated permafrost thawing caused by global warming and an increasing number of beaver populations now recovering from near extirpation are the main causes of ponding in the boreal region. Unfortunately, ponding is associated with increased concentrations of neurotoxic methylmercury, particularly during the first years after the initial flooding. An understanding of the processes controlling methylmercury formation is thus required to develop management strategies that aim to reduce mercury exposure. Our results show that ponding enhanced the released of fresh humic organic matter and nutrients triggered algae growth, both determining the final concentration of methylmercury in ponds.

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Section: Resultsmentioning

confidence: 99%

High methylmercury formation in ponds fueled by fresh humic and algal derived organic matter

Ortega

Catalán

Björn

et al. 2017

Limnology & Oceanography

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“…), but others have also reported an apparent discrepancy between HIX and SUVA (Catalán et al. ). Because humic acids contain a greater proportion of aromatic groups than fulvic acids (Findlay and Sinsabaugh ), it could be hypothesized that the observed increase in humic substances is mainly driven by the more labile fulvic acids.…”

Section: Discussionmentioning

confidence: 96%

“…This release would be facilitated by the inundation of soils and flooding of vegetation in the case of beaver dams (Catalán et al. ) and by soil disturbance and road networks in the case of forest management.…”

Section: Discussionmentioning

confidence: 99%

Linking stream ecosystem integrity to catchment and reach conditions in an intensively managed forest landscape

et al. 2018

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Forests are vital to maintaining headwater stream integrity in forested biomes, which ensures the delivery of aquatic ecosystem services downstream. Forest harvesting, however, can alter land–water linkages and compromise stream integrity. Historically, the main effects of forestry on streams have been documented by studies that used relatively few (mainly abiotic) indicators and which focused on single harvesting events. However, forest management is expected to intensify in the future to meet increasing global wood demand and it is likely that our present understanding does not adequately capture the cumulative effects that streams will be subjected to under intensive forest management. To address this, we assessed the effects of varying forest management intensities on the integrity of 15 forest headwater streams in northwestern New Brunswick, Canada. We used a comprehensive approach to link multiple biotic and abiotic indicators of stream ecosystem integrity to reach‐ and catchment‐level characteristics including forest management (e.g., cumulative harvesting over time, road density, forest condition). Most indicators detected the gradient in forest management intensity with abiotic indicators responding most strongly. Streams in catchments with highest management intensity (especially road density) tended to have higher fine inorganic sediment deposition and entrainment, water cations and carbon, dissolved organic matter humification, and water temperature. These abiotic differences were associated with higher biofilm biomass and shredder densities, but lower leaf decomposition. Evidence from our multi‐indicator approach elucidated a potential effects pathway of higher inorganic sediment content in biofilms of organic matter potentially limiting or altering its use by microbial and benthic macroinvertebrate (BMI) communities and resulting in reduced leaf decomposition rates. Overall, this study shows that current best management practices in an intensively managed watershed (and legacy effects from past management such as older road systems) do not fully protect against an increased delivery of terrestrial materials to streams with resulting habitat and biotic changes, but that they are mostly effective at preventing the impairment of BMI communities.

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“…Probably, the low algal contributions observed in MC2 stemmed from the beaver dam ~1 km upstream from our sampling reach, which may have enhanced the release of terrestrial materials following the inundation of soils (Catalán et al. ).…”

Section: Discussionmentioning

confidence: 99%

Increased reliance of stream macroinvertebrates on terrestrial food sources linked to forest management intensity

Erdozain

Kidd

Kreutzweiser

et al. 2019

Ecological Applications

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Our understanding of how forest management practices affect the relative importance of autochthonous vs. allochthonous resource use by headwater stream food webs is relatively poor. To address this, we used stable isotope (C, N, and H) analyses of food sources and macroinvertebrates from 15 streams in New Brunswick (Canada) and assessed how different catchment conditions arising from the gradient in forest management intensity affect the contribution of autochthonous resources to these food webs. Aquatic primary production contributed substantially to the biomass of invertebrates in these headwater streams, especially for scrapers and collector‐gatherers (25–75%). However, the contribution of algae to food webs decreased as forest management intensity (road density and associated sediments, water cations/carbon, and dissolved organic matter humification) increased, and as canopy openness decreased. This trend was probably due to an increase in the delivery of organic and inorganic terrestrial materials (dissolved and in suspension) in areas of greater harvesting intensity and road density, which resulted in more heterotrophic biofilms. Overall, results suggest that, despite the presence of riparian buffers, forest management can affect stream food web structure via changes in energy flows, and that increased protection should be directed at minimizing ground disturbance in areas with direct hydrological connection to streams and at reducing dissolved and particulate matter inputs from roads and stream crossings in catchments with high degrees of management activity.

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Effects of beaver impoundments on dissolved organic matter quality and biodegradability in boreal riverine systems

Cited by 23 publications

References 44 publications

High methylmercury formation in ponds fueled by fresh humic and algal derived organic matter

High methylmercury formation in ponds fueled by fresh humic and algal derived organic matter

Linking stream ecosystem integrity to catchment and reach conditions in an intensively managed forest landscape

Increased reliance of stream macroinvertebrates on terrestrial food sources linked to forest management intensity

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