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Map of Lake Simcoe with 5 m depth contour lines shown. Shaded area indicates portion of lake \15 m depth (approximate maximum depth of epilimnion and euphotic zone). Study site marked with star 

Map of Lake Simcoe with 5 m depth contour lines shown. Shaded area indicates portion of lake \15 m depth (approximate maximum depth of epilimnion and euphotic zone). Study site marked with star 

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Dreissenid mussels are notorious invasive organisms whose establishment is associated with large, ecosystem-scale changes to patterns of productivity in aquatic systems. We investigated how localized impacts of dreissenids affect the potential of littoral substrates to support primary and secondary production using in situ incubations and compariso...

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... Simcoe is a large (722 km 2 ), oligo-mesotrophic lake in southern Ontario. Because of its gently sloping morphometry and clear water Lake Simcoe has an extensive littoral area with approximately half of the lake bottom in the euphotic zone (Fig. 1). Cobble, pebble, and boulder are common littoral substrates, especially along exposed shorelines, with areas of extensive macrophyte growth in sheltered parts of the lake (Rawson 1930;Ginn 2011). The lake has a long history of human impact and species invasions (Rawson 1930;Evans et al. 1996;Palmer et al. 2011), with zebra mussels (D. polymorpha) colonizing the lake in the mid 1990s, and quagga mussels (D. rostriformis bugensis) first detected in 2004 ( Evans et al. 2011). Dreissenids were common and abundant throughout the littoral zone when the experiments on which we report were carried out ( Ozersky et al. 2011a), with D. polymorpha accounting for more than 98 % of total dreissenid abundance in the shallow littoral areas of the lake ( Ozersky et al. ...

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... dissolved oxygen, redox characteristics and pH can all affect the geochemical behavior of sedimentary P, then cause the release of P in sediments (Mort et al., 2010;Pan et al., 2020;Yang et al., 2021a). Long-term P release is calculated by mass balances of P supply on scales of years to decades, binding and burial, which are governed by sediment mineralogy and diagenetic processes (Ozersky et al., 2013;Depew et al., 2018), and regulated the ecosystem health for a long time (Parsons et al., 2017). Thus, clarifying the geochemical processes of different P forms in sediment cores can help understand their potential mobility and release risks, which can provide recommendations for management. ...
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... Invasive dreissenids have had a profound impact on the light environment that impacts not only growth but also the timing of late summer detachment and attendant beach deposition (Kuczynski et al., 2016). Mussels have also influenced the nutrient environment by entraining and processing particulate matter, releasing a significant fraction of its particulate phosphorus intake as soluble reactive phosphorus (SRP, μgP L -1 , Ozersky et al., 2013), the only form of the nutrient fully and freely available to algae (Reynolds, 2006). Thus, particulate phosphorus has become a more important feature of the Cladophora nutrient environment, be it introduced through tributary and point source discharges or transported to the nearshore from the offshore (Zhou et al., 2021). ...
Article
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... All methods for measuring aquatic metabolism rates are associated with some errors [31,32], and research focusing on benthic metabolism in particular has generally been more recent than research on planktonic dynamics [33]. Nevertheless, in situ measurements of changes in oxygen concentrations in sealed transparent benthic chambers or domes are a common method for assessing periphyton metabolism rates both in marine [34] and freshwater [35,36] environments. We thus measured oxygen dynamics in sealed clear and dark chambers containing rocks with attached FAB (Cladophora) or non-FAB periphyton assemblages and exposed in the lake (in situ), as this general approach has also been applied to determine periphyton metabolism rates in other large lakes [37,38]. ...
... Our measured rates of periphyton GPP are within the range that has been described previously for mesotrophic and oligotrophic lakes ( [36] and references therein). However, contrary to the findings of a previous study that focused on FAB blooms by Spirogyra sp. in a Japanese lake [22], we measured the highest rates of both total and chl a-specific GPP on non-FAB rocks in Bear Lake. ...
Article
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... The long-term P release can be determined considering the mass balance among P supply, binding, and burial on scales of years to decades, which are controlled by sediment mineralogical composition and diagenetic processes (Depew et al., 2018;Dittrich et al., 2013;Kim et al., 2013;Matisoff et al., 2016;Ozersky et al., 2013). During sediment diagenesis, while some labile (reactive) P forms can be released to dissolved bioavailable forms, some labile P can also transfer into inert P forms that can be permanently buried (Alam et al., 2020;Dittrich et al., 2013). ...
Article
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... The natural substrate at all sites was either rocky (bedrock, boulder, cobble, or pebble) or sandy. Macrophytes and invasive dreissenid mussels (which can stimulate periphyton growth through nutrient excretion; Ozersky et al., 2013) were absent at all but one site (GB6) due to the high energy environment at the shallow deployment depths of our experiments. Experiments were deployed between 11 and 31 July 2017 and retrieved between 8 and 28 August 2017. ...
Article
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... The ecological effects of biogeochemical cycling by suspension feeding bivalves have been well studied (Vaughn & Hakenkamp, 2001;Vaughn & Hoellein, 2018). The removal of suspended fine particulate matter can significantly reduce turbidity, promote macrophyte and algae growth (Ozersky et al., 2013), and change ecological community dynamics (De Stasio et al., 2014;Vanderploeg et al., 2001). Filter feeding may also have considerable geomorphic effects, such as reduced downstream fine sediment transport. ...
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Invertebrates are important sediment engineers, making up for their small body size with abundance and behavioral diversity. However, despite the recognized importance of invertebrates as sediment engineers in terrestrial and marine environments, zoogeomorphology in rivers has primarily considered larger taxa, such as fish and beaver. This article reviews the zoogeomorphic effects of invertebrates in freshwater habitats, with a focus on rivers. To better synthesize current zoogeomorphic research and to help guide future studies we build a conceptual model considering biotic (behavior, abundance, body size, life history, and species invasions) and abiotic (geophysical energy and sediment grain size) controls on the direction and magnitude of zoogeomorphology. We also incorporate invertebrate engineers into conceptual sediment entrainment models, to understand their geomorphic role in the context of hydraulic power and sediment size. We structure our review around invertebrate behavior as a key control on whether invertebrates have a sediment destabilizing or stabilizing impact. Invertebrate zoogeomorphic behavior are diverse; the majority of research concerns bioturbation, a result of locomotion, foraging, and burrowing behaviors by many taxa. Similarly, burrowing into bedrock by a caddisfly and non-biting midge larvae promotes bioerosion. Attachment to the substrate, (e.g., silk nets by caddisfly larvae or byssal threads by some mussels) can stabilize sediment, providing bioprotection. Bioconstructions (e.g., caddisfly cases and mussel shells) may have either stabilizing or destabilizing effects depending on their density and abiotic context. Interactions between lotic invertebrates and fluvial processes are complex and understudied, requiring further research across a greater range of taxa, behaviors, and spatiotemporal scales. This article is categorized under: • Water and Life > Nature of Freshwater Ecosystems • Water and Life > Conservation, Management, and Awareness Abstract Invertebrates affect the transport of sediment in rivers but are often overlooked due to their small size. Diverse behaviors result in significant effects on fluvial geomorphology.
... In contrast, stations B and N are shallow, with lakebed colonized by dreissenid mussels (Nicholls et al. 2011). Filter feeding dreissenids can affect particle deposition and P recycling through the ingestion of algal and other debris and subsequent deposition of particles as faeces and pseudofaeces (Howell et al., 1996;Ozersky et al., 2013;Mosley and Bootsma 2015). Manning (1996) showed that before dreissenid colonization in the mid-90s a large proportion of suspended particles from upper basins of the Bay of Quinte was exported downstream to Hay Bay. ...
... While there are no recent estimates, Bailey et al. (1999) concluded that their filtration capacity (0.1-10 days) far exceeded water renewal time, effectively intercepting suspended algal particles and accelerating their deposition -increasing carbon and P content of surrounding surface sediment of the upper bay sites. At the same time, mussel respiration depletes oxygen near lake bed (Ozersky et al., 2013) while their guts and excreta represent anaerobic environments (Hecky et al., 2004), affecting the cycling of redox sensitive elements. In turn, this may mobilize redox sensitive P forms in surface sediment and likely contributes to higher short-term diffusive P fluxes at stations B and N. ...
Article
Phosphorus (P) levels in eutrophic lakes with restricted external P inputs often show hysteresis resulting from sediment P diagenetic recycling. Hard water oxygenated lakes are often thought to be less susceptible to P release from sediment due to precipitation of P with calcium carbonate and P sorption on iron (Fe) oxyhydroxides in oxidized surface sediments. However, perpetuated eutrophic conditions in many hard water oxygenated lakes persist despite drastic reduction of external P inputs. What limits P sediment binding capacity and drives its release from sediments in such lakes is often less understood. Here we characterize sediment P diagenetic processes driving persistent internal loading in the Bay of Quinte, a hard water, polymictic embayment of Lake Ontario, Canada. We used a multifaceted approach, combining a comprehensive three-year study of sediment P binding forms, recent sediment stratigraphy and accumulation, high spatial resolution measurement of dissolved oxygen, redox potential and pH across the sediment-water interface and depth profiles of nutrient and metals concentrations in pore water. Despite oxygenated bottom water conditions P diffusive fluxes during summer are substantial (1–6.5 mg P/m ² /day), representing as much as 50% of external P inputs. Estimated rates of benthic organic carbon degradation indicate that anaerobic organic P mineralization in anoxic sediments is the main driver of P release, which is strongly influenced by Fe reduction. Estimated rates of benthic organic carbon degradation indicate that anaerobic organic P mineralization in anoxic sediments is the main driver of P release. In surface sediment the redox sensitive P is the prevailing diagenetically reactive P phase, emphasizing strong coupling with ferric Fe. While this indicates substantial P sorption on Fe oxyhydroxides, their spare binding capacity is limited, as reducible Fe: P ratios are close to sorption limit. The calcium carbonate bound P increased with sediment depth at the expense of redox sensitive P, suggesting diagenetic sequestration into apatite with sediment burial. However, only 40% of diagenetically reactive P forms, which account for ~2/3 of the total P in surface sediment, are permanently retained during burial. Importantly, our data show that in fact significant P-flux occurs in shallow areas, with an apparent discordance with concurrent measures of long-term P release from the sediments. These results also demonstrate that short-term measures cannot be extrapolated to long-term estimates and vice versa.
... Numerous studies find that aquatic invertebrate communities can make significant contributions to ecosystem nutrient demand via excretion and closely related species are often assumed to make similar contributions (e.g., Grimm 1988, Vanni 2002, Hall et al. 2003, Alves et al. 2010, Ozersky et al. 2013. Vanni (2002) argues that of all the direct (excretion, ingestion, egestion, production) and indirect (competition and physical modification of the environment) effects that animals can have on nutrient cycling, excretion is the most important because dissolved inorganic forms of excreted nutrients (e.g., NH þ 4 and PO 3À 4 ) are readily assimilated by primary producers and microbial decomposers that form the trophic base of food webs. ...
Article
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Understanding the amount of variation in functional traits between closely related species within guilds is critical for understanding links between community composition and ecosystem processes. Nutrient excretion is an important link between animals and their environments, and aquatic invertebrate communities can supply a considerable proportion of ecosystem nutrient demand via excretion. We quantified nitrogen (N) and phosphorus (P) excretion rates of 10 species of larval caddisflies that inhabit high‐elevation ponds and wetlands to determine the magnitude of variation in nutrient excretion within this guild. We found considerable interspecific variation in biomass‐specific excretion of nitrogen (eightfold differences), phosphorus (sevenfold differences), and the stoichiometric N:P ratios (fivefold differences). Through a meta‐analysis, we compared the variation within this guild to the variation found in other family‐level species assemblages to determine the overall range in the variation of nutrient excretion that could be expected across guilds and to determine whether the variation in this caddisfly guild is comparatively extreme, average, or low. The meta‐analysis revealed a large range in variation among guilds, and comparatively, the variation within this caddisfly guild is high for N excretion and intermediate for P excretion. The considerable variation within guilds revealed by our meta‐analysis suggests that functional redundancy among guild members is difficult to predict. Thus, some natural or human‐caused species gains or losses within biological groupings such as guilds and trophic levels could have little or no effect on ecosystem processes, whereas others could have very large effects.
... The arrival of dreissenid mussels in early 1990s likely affected sediment P dynamics (Hecky et al., 2004). In shallow nearshore areas, dreissenid colonies changed depositional patterns, intensified particulate matter eposition and bioavailable nutrient recycling (Howell et al., 1996;Hecky et al., 2004;Ozersky et al., 2013;Mosley and Bootsma, 2015). Prior to dreissenid colonization, fine grained P associated with clay-organic matter-iron oxide assemblages was retained in suspension over extended periods and largely exported to lower reaches of the Bay of Quinte or lake Ontario (Manning, 1996). ...
... Linear grained suspended matter. Subsequent deposition of intercepted particles as faeces and pseudofaeces, effectively enriches surface sediment in both P and organic matter (Howell et al., 1996;Ozersky et al., 2013) which in turn fuels diagenetic recycling of nutrients. Packaging of particulate P with organic matter in mussel excretions creates anaerobic microenvironments at sediment surface which likely accelerates release of redox sensitive P upon deposition (Hecky et al., 2004). ...
... Packaging of particulate P with organic matter in mussel excretions creates anaerobic microenvironments at sediment surface which likely accelerates release of redox sensitive P upon deposition (Hecky et al., 2004). Moreover, oxygen depletion over mussel infested lake bed stimulates breakdown of redox sensitive P forms (e.g., Ozersky et al., 2013;Tyner et al., 2015), while anaerobic environments in mussel guts create favorable conditions for breakdown and release of redox sensitive P forms (Hecky et al., 2004). Our model captures dreissenid mussel reengineering of sediment P dynamics, insofar the recent increase in P diffusive fluxes in the upper bay stations are concerned. ...
Article
Internal P flux contributes significantly to P budget in the Bay of Quinte. • Dynamics of sediment P transformations were studied using diagenetic modelling. • Summer sediment P diffusive fluxes varied between 1.5 and 3.6 mg P m −2 d −1. • Diagenesis of redox sensitive and organic P forms drives substantial P diffu-sive flux. • Sediment P retention was dominated by apatite formation and varied between 71 and 75%. Internal phosphorus (P) loading significantly contributes to hysteresis in ecosystem response to nutrient reme-diation, but the dynamics of sediment P transformations are often poorly characterized. Here, we applied a reaction-transport diagenetic model to investigate sediment P dynamics in the Bay of Quinte, a polymictic, spatially complex embayment of Lake Ontario, (Canada). We quantified spatial and temporal variability of sediment P binding forms and estimated P diffusive fluxes and sediment P retention in different parts of the bay. Our model supports the notion that diagenetic recycling of redox sensitive and organic bound P forms drive sediment P release. In the recent years, summer sediment P diffusive fluxes varied in the range of 3.2-3.6 mg P m −2 d −1 in the upper bay compared to 1.5 mg P m −2 d −1 in the middle-lower bay. Meanwhile sediment P retention ranged between 71% and 75% in the upper and middle-lower bay, respectively. The reconstruction of temporal trends of internal P loading in the past century, suggests that against the backdrop of reduced external P inputs, sediment P exerts growing control over the lake nutrient budget. Higher sediment P diffusive fluxes since mid-20th century with particular increase in the past 20 years in the shallower upper basins, emphasize limited sediment P retention potential and suggest prolonged ecosystem recovery, highlighting the importance of ongoing P control measures.
... Previous studies have shown significant increases in concentrations of dissolved nitrate (NO 3 − ) and ammonium (NH 4 + ) associated with the establishment of Dreissena spp. (e.g., Higgins and Vander Zanden, 2010;Johengen et al., 1995;Ozersky et al., 2013;Strayer, 2009). These increases in dissolved NO 3 − and NH 4 + likely increase the isotopic values of dissolved inorganic nitrogen (DIN) in the water column of invaded habitats. ...
Article
Identifying the sources of methylmercury (MeHg) and tracing the transformations of mercury (Hg) in the aquatic food web is an important component of effective strategies for managing fish Hg concentrations. In our previous work we measured stable isotopes of Hg (δ202Hg, Δ199Hg, and Δ200Hg) in the Laurentian Great Lakes and estimated source contributions of Hg to bottom sediment. Here, we identify isotopically distinct Hg signatures for Great Lakes predatory fish. Fish reflect high values for odd-isotope mass independent fractionation (MIF) that span a large range in Δ199Hg (2.27 - 6.73‰). With the exception of Lake Erie, temporal variability and intralake specific signatures were not evident. The large range in odd-MIF reflects variability in the depth of the euphotic zone where Hg is most likely incorporated into the food web. Even-isotope MIF, a potential tracer for Hg from precipitation, appears both disconnected from lake sedimentary sources and comparable in magnitude among the lakes. When comparing isotopic Hg signatures in sediment and MeHg in fish, bioaccumulated MeHg isotopic signatures are more reflective of atmospheric precipitation than sediment. We also conclude that the degree of photochemical processing of Hg is controlled by phytoplankton uptake rather than by dissolved organic carbon quantity among lakes.