Environmental factors structuring benthic primary producers at different spatial scales in the St. Lawrence River (Canada)

Lévesque, David; Hudon, Christiane; James, Patrick M. A.; Legendre, Pierre

doi:10.1007/s00027-016-0501-4

Cited by 11 publications

(11 citation statements)

References 38 publications

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“…In contrast with the eutrophic River Loire in which phytoplankton represented the most important primary producer (Meybeck et al 1998), annual production of rooted vascular plants and associated epiphytes in the SLR constitutes &66% of total autochthonous production (Vis et al 2007). Given the predominance of benthic primary producers along the 550-km-long course of the SLR (Lévesque et al 2017), it is most likely that plant decay takes place, at least partially, locally (yielding DOC) rather than being entirely exported as detritus (POC) to the estuary. The isotopic signature of organic carbon fractions indeed showed that aquatic primary producers contributed a significant proportion of total organic carbon year-round and that degradation of aquaticallyproduced POC into DOC was most important during summer months throughout the SLR system (Hélie and Hillaire-Marcel 2006).…”

Section: Discussionmentioning

confidence: 98%

“…Fluvial lakes St. Lawrence, Saint-François, Saint-Louis and SaintPierre together support [200 km 2 of emergent wetlands (Hudon et al 2006), in addition to extensive riverbed colonization by submerged aquatic macrophytes (Lévesque et al 2017). In Lake Saint-Pierre alone (LSP, &350 km 2 , Fig.…”

Section: Study Areamentioning

confidence: 95%

“…The total annual contribution of primary producers to C fixation and nutrient assimilation was then estimated by applying these values to the entire wetted area of SLR bottom (2637 km 2 ) between Wolfe Island and Québec. This estimation was deemed conservative since both the biomass (Lévesque et al 2017) and maximum depth of colonization (i.e. water transparency, see Hudon et al 2000) of submerged aquatic vegetation are lower in Lake Saint-Pierre than for fluvial lakes located upstream.…”

Section: Contribution Of Primary Producers To Carbon Fixation and Nutmentioning

confidence: 99%

“…After exiting Lake Ontario, the SLR flows through a succession of broad (2-12 kmwide) and shallow (mean depth 3-7 m) fluvial lakes, which are extensively colonized by submerged aquatic vegetation (Vis et al 2007;Lévesque et al 2017). Little interest has been given to the seasonal variations in carbon and nutrient flux as a result of within-river biological processes such as carbon fixation, nutrient assimilation and transformation by bacteria and primary producers.…”

Section: Introductionmentioning

confidence: 99%

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Hydrological and biological processes modulate carbon, nitrogen and phosphorus flux from the St. Lawrence River to its estuary (Quebec, Canada)

et al. 2017

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Increased flux of carbon and nutrients from human activities in river basins were linked to acidification and deepwater hypoxia in estuaries and coastal areas worldwide. Annual loads (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) of suspended particulate matter (SPM), dissolved organic carbon (DOC), total nitrogen (TN) and total phosphorus (TP) were assessed at the Lake Ontario inlet of the St. Lawrence River (SLR) (7110 m 3 s -1 ) and its estuarine outlet at Québec City (12,090 m 3 s -1 ). Internal loads from the Ottawa River (1950 m 3 s -1 ), seventeen other tributaries, urban wastewaters, atmospheric deposition and erosion were also estimated. Erosion (65% of SPM, 29% of TP), inflow from Lake Ontario (42% of DOC, 47% of TN) and Ottawa River (28% of DOC) contributed important flux to the estuary. Loads from other tributaries (20 and 27% of TN and TP at Quebec City) largely exceeded municipal sources (6% of exported TN and TP) and require future remediation. Aquatic plants fixed 277,000 t of C, 49,000 t of N and 7000 t of P (May-Sept.), delaying the nutrient flux to the estuary and turning the SLR into a nutrient sink over summers of lowest discharge. Degradation of exported organic C could consume 5.4-7.1 million t O 2 year -1 in the estuary whereas SLR flux of N and P represent 31-47% and 7-14% of total annual estuarine flux, respectively. Carbon and Nitrogen flux from freshwaters partly explain the decline in pH and oxygen concentrations in deep estuarine waters thus highlighting the need to reduce diffuse sources of nutrients in the entire watershed.

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Section: Discussionmentioning

confidence: 98%

Section: Study Areamentioning

confidence: 95%

Section: Contribution Of Primary Producers To Carbon Fixation and Nutmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrological and biological processes modulate carbon, nitrogen and phosphorus flux from the St. Lawrence River to its estuary (Quebec, Canada)

et al. 2017

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“…For example, land cover previously dominated by agriculture may sustain high nutrient loads from sediments to streams for a long time period after a change in land use (Maloney and Weller 2011). Anthropogenic land use, comprising agriculture, development and urbanization, contributes to increased nutrient and ion concentrations (Taka et al 2017), pollutants and turbidity (due to sediment load) in streams (Foley et al 2005), and these effects cascade downstream (Levesque et al 2017). Wang et al (2008) found that nutrient loading and percent of urban land use were the most important drivers of deteriorating stream conditions.…”

Section: Introductionmentioning

confidence: 99%

Are drivers of microbial diatom distributions context dependent in human‐impacted and pristine environments?

Pajunen

Jyrkänkallio‐Mikkola

Luoto

et al. 2019

Ecological Applications

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Species occurrences are influenced by numerous factors whose effects may be context dependent. Thus, the magnitude of the effects and their relative importance to species distributions may vary among ecosystems due to anthropogenic stressors. To investigate context dependency in factors governing microbial bioindicators, we developed species distribution models (SDMs) for epilithic stream diatom species in human‐impacted and pristine sites separately. We performed SDMs using boosted regression trees for 110 stream diatom species, which were common to both data sets, in 164 human‐impacted and 164 pristine sites in Finland (covering ~1,000 km, 60° to 68° N). For each species and site group, two sets of models were conducted: climate model, comprising three climatic variables, and full model, comprising the climatic and six local environmental variables. No significant difference in model performance was found between the site groups. However, climatic variables had greater importance compared with local environmental variables in pristine sites, whereas local environmental variables had greater importance in human‐impacted sites as hypothesized. Water balance and conductivity were the key variables in human‐impacted sites. The relative importance of climatic and local environmental variables varied among individual species, but also between the site groups. We found a clear context dependency among the variables influencing stream diatom distributions as the most important factors varied both among species and between the site groups. In human‐impacted streams, species distributions were mainly governed by water chemistry, whereas in pristine streams by climate. We suggest that climatic models may be suitable in pristine ecosystems, whereas the full models comprising both climatic and local environmental variables should be used in human‐impacted ecosystems.

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Rhododendron maximumimpacts seed bank composition and richness followingTsuga canadensisloss in riparian forests

et al. 2018

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Miniat. 2018. Rhododendron maximum impacts seed bank composition and richness following Tsuga canadensis loss in riparian forests. Ecosphere 9(4):e02204. 10. 1002/ecs2.2204 Abstract. Southern Appalachian riparian forests have undergone changes in composition and function from invasive pathogens and pests. Castanea dentata mortality in the 1930s from chestnut blight (Cryphonectria parasitica) and Tsuga canadensis mortality in the 2000s from the hemlock woolly adelgid (Adelges tsugae) have led to the expansion and increased growth of Rhododendron maximum, an evergreen subcanopy shrub. A better understanding of seed bank characteristics and the various abiotic and biotic factors that affect the seed bank may be useful in determining the restoration potential of forest communities following invasion-related disturbances. We compared the seed bank of two deciduous forest types: hardwood forests with a dense R. maximum subcanopy (hereafter, RR) and hardwood forests without R. maximum (hereafter, HWD). We evaluated numerous microenvironmental variables through principal component analysis (PCA) and correlated the derived PCA axes scores to seed bank density and richness across forest types. We found that seed bank density was comparable between the forests types; however, seed bank richness was much lower in RR than HWD and the species composition was dissimilar between forest types. Twenty-eight of 64 (44%) species in the seed bank of HWD were not found in the seed bank of RR. Species that were represented in both forest types were often found in contrasting densities. Most notably, seed bank densities of several woody species were considerably higher in RR (85%) than HWD (45%), while herbaceous seed bank density was lower in RR (11%) than HWD (50%). Mineral soil pH, soil nutrient availability, and soil moisture were lower, and organic soil (Oi + Oe + Oa) depth and mass were greater in the RR than HWD forest type. PCA correlations revealed that PCA4 (represented by understory density and Oe + Oa phosphorus and carbon/nitrogen ratio) was negatively correlated with total seed bank density. PCA1 (represented by Oe + Oa cations and phosphorus, understory richness, ground-layer cover, and mineral soil pH) and PCA4 were positively correlated with total seed bank richness. These results suggest that the soil seed bank will not be the primary mode of recruitment to establish a diverse and herbaceousrich community if a RR is present.

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Environmental factors structuring benthic primary producers at different spatial scales in the St. Lawrence River (Canada)

Cited by 11 publications

References 38 publications

Hydrological and biological processes modulate carbon, nitrogen and phosphorus flux from the St. Lawrence River to its estuary (Quebec, Canada)

Hydrological and biological processes modulate carbon, nitrogen and phosphorus flux from the St. Lawrence River to its estuary (Quebec, Canada)

Are drivers of microbial diatom distributions context dependent in human‐impacted and pristine environments?

Rhododendron maximumimpacts seed bank composition and richness followingTsuga canadensisloss in riparian forests

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