Ecology of the macrophyte Podostemum ceratophyllum Michx. (Hornleaf riverweed), a widespread foundation species of eastern North American rivers

Wood, James; Freeman, Mary C.

doi:10.1016/j.aquabot.2017.02.009

Cited by 12 publications

(6 citation statements)

References 66 publications

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“…These beds can accumulate massive biomass over summer in temperate regions (Madsen, Chambers, James, Koch, & Westlake, 2001; Zohary & Ostrovsky, 2011), resulting in reduced native vegetation diversity (Andersen, Kragh, & Sand‐Jensen, 2017; Parveen, Asaeda, & Rashid, 2017), changes in community composition of other trophic levels such as benthic invertebrates (Kelly & Hawes, 2005; Kovalenko & Dibble, 2010), and loss of ecosystem functions and services (Bunn, Davies, Kellaway, & Prosser, 1998; Villamagna & Murphy, 2010). Consequently, invasive macrophytes commonly represent ‘foundation species’ (Ramus, Silliman, Thomsen, & Long, 2017; Wood & Freeman, 2017) and have been referred to as ‘ecosystem engineers’ due to their dominance in abundance and influence on lentic ecosystems (Thomaz, Mormul, & Michelan, 2014; Yarrow et al, 2009). A primary mechanism of impact by invasive macrophytes is the production of adverse physicochemical conditions above the sediment–water interface, which have been recorded inside dense beds in shallow lakes (Andersen et al, 2017; Bunch, Allen, & Gwinn, 2010; Vilas, Marti, Adams, Oldham, & Hipsey, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…. Consequently, invasive macrophytes commonly represent 'foundation species' (Ramus, Silliman, Thomsen, & Long, 2017;Wood & Freeman, 2017) and have been referred to as 'ecosystem engineers' due to their dominance in abundance and influence on lentic ecosystems (Thomaz, Mormul, & Michelan, 2014;Yarrow et al, 2009). A primary mechanism of impact by invasive macrophytes is the production of adverse physicochemical conditions above the sediment-water interface, which have been recorded inside dense beds in shallow lakes (Andersen et al, 2017;Bunch, Allen, & Gwinn, 2010;Vilas, Marti, Adams, Oldham, & Hipsey, 2017).…”

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confidence: 99%

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Invasive macrophytes induce context‐specific effects on oxygen, pH, and temperature in a hydropeaking reservoir

Moore

Clearwater²,

Duggan

et al. 2020

River Research & Apps

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Dense macrophyte beds are known to produce extreme diurnal oxygen and temperature conditions in shallow lakes. However their influences in managed hydropeaking reservoirs has received limited attention. We measured dissolved oxygen, pH and water temperature in the Lake Kar apiro hydroreservoir, northern New Zealand, across a gradient of proportional water-column height occupied by the invasive macrophytes Egeria densa and Ceratophyllum demersum, which dominated in the upperriverine (variable water inflow) and lower-lacustrine (variable water level) sections, respectively. Hypoxia and anoxia events that occurred inside invasive macrophyte beds during their summer peak biomass accumulation period were more pronounced for C. demersum than for E. densa, and within the bottom 20% of the water column. In contrast, pH and temperature changed little in relation to proportional macrophyte height. Macrophyte species differences in the production of hypoxia and anoxia events increased when site-specific hydropeaking management covariates (depth, inflows, water level) were accounted for. This association with hydropeaking likely resulted from contrasting hydrodynamics in the lower-lacustrine and upper-riverine lake sections, where oxygen can decrease with higher water levels and lower water inflow rates, respectively. During the course of our study, some macrophyte beds were treated with herbicide, enabling us to document prolonged and sustained hypoxic/anoxic conditions near the bottom following spraying. These results underscore the adverse effects of invasive macrophytes on water physicochemical attributes that sustain aquatic biota, and highlight the context-dependent nature of these effects moderated by reservoir management for hydropeaking and macrophyte control.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Invasive macrophytes induce context‐specific effects on oxygen, pH, and temperature in a hydropeaking reservoir

Moore

Clearwater²,

Duggan

et al. 2020

River Research & Apps

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“…The intense herbivory pressure and reduced biomass observed in low-velocity habitats indicate that the realised niche of Podostemum can be strongly controlled by consumers interacting with water velocity. This phenomenon was hypothesised by Wood and Freeman (2017) and is evidenced by the persistence and growth of Podostemum in low-velocity locations when the plant was protected from consumers. Supportive of this notion, our reciprocal transplant and consumer exclosure experiments showed that stem length of heavily grazed plants can recover relatively quickly when water velocity is above approximately 0.5 m/s or when herbivory is precluded.…”

Section: Discussionmentioning

confidence: 96%

“…If these conclusions are correct, managing for more natural flow regimes (i.e. periods of high flow and low flow) in flow‐regulated rivers could restore Podostemum habitat in rivers where the plant has been extirpated due to prolonged low flow conditions (Countryman, ; Philbrick & Crow, ; Wood & Freeman, ). A flow regime that supports Podostemum growth may also aid in managing nutrient enrichment in downstream water bodies because reductions in Podostemum biomass may lead to increased nutrient spiralling length (Newbold, Elwood, O'Neill, & Winkle, ) and reduced resource flux (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…If these conclusions are correct, managing for more natural flow regimes (i.e. periods of high flow and low flow) in flow-regulated rivers could restore Podostemum habitat in rivers where the plant has been extirpated due to prolonged low flow conditions (Countryman, 1978;Philbrick & Crow, 1983;Wood & Freeman, 2017). A flow regime that supports…”

Section: Discussionmentioning

confidence: 99%

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Water velocity regulates macro‐consumer herbivory on the benthic macrophyte Podostemum ceratophyllum Michx.

et al. 2019

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Macrophytes influence aquatic ecosystems by increasing habitat complexity and providing trophic resources for aquatic fauna. While herbivory on freshwater macrophytes is widely documented in lakes and low‐velocity riverine habitats, the influence of herbivory on macrophytes in higher‐velocity habitats has rarely been examined. We investigated the hypothesis that water velocity can influence consumption rates of the submerged macrophyte, Podostemum ceratophyllum, an angiosperm that grows attached to stable substrates in high water velocity riverine habitats throughout eastern North America. Known macro‐consumers of Podostemum include crayfishes, turtles, and waterfowl. We estimated grazing pressure by conducting short‐term (up to 77‐day) transplant and consumer‐exclosure experiments, and quantified changes in Podostemum stem length when the plant was exposed to low (<0.5 m/s) and higher velocities in two Piedmont rivers in Georgia (USA). Podostemum transplanted into low‐velocity habitats rapidly lost stem length unless macro‐consumers were excluded from accessing the plant. In contrast, Podostemum transplanted into high‐velocity habitats showed little change or gained stem length. We estimated that 85% (67–98%; 95% credible interval) of the daily stem growth (0.026 cm cm−1 day−1) in Podostemum was consumed during a 77‐day paired consumer‐access versus exclosure experiment conducted in mean water velocities of 0.35–0.5 m/s. We also found a positive relation (R2 = 0.58) between Podostemum biomass and water velocity (ranging between c. 0.1 and 1.3 m/s) in benthic samples collected over a 2‐month period. We conclude that high water velocity reduces herbivory on Podostemum, and that water velocity can thus control the accrual of benthic plant biomass and the movement of plant‐derived materials through benthic food webs. Our research has implications for estimating resource storage and flux in lotic food webs and illuminates a mechanism by which flow regulation and management may affect basal resources in rivers.

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How low is too low? Partnering with stakeholders and managers to define ecologically based low‐flow thresholds in a perennial temperate river

Rack,

Freeman,

Emanuel

et al. 2024

River Research & Apps

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Managing aquatic ecosystems for people and nature can be improved by collaboration among scientists, managers, decision‐makers, and other stakeholders. Many collaborative and interdisciplinary approaches have been developed to address the management of freshwater ecosystems; however, there are still barriers to overcome. We worked as part of a regional stakeholder group comprising municipal water utility operators, conservation organizations, academic partners, and other stakeholders to understand the effects of low‐flow and drought on ecological functions of the upper Flint River, Georgia (USA), a free‐flowing river important for municipal water supply, recreation, and native biota. We used published literature and locally targeted studies to identify quantitative flow targets that could be used to inform water management and drought planning. Drawing from principles of Translational Ecology, we relied on an iterative process to develop information needs for the group and maintained communication and engagement throughout data collection, analysis, and synthesis. We identified three quantitative flow benchmarks to evaluate the ecological impacts of drought in the river. The results were valuable to both the water utilities represented in the working group and State regional water planning, which is used to guide water management strategies and permitting for the basin. We identified principles that were important for the successful engagement in the working group and helped to overcome the challenge of working across sectors and without direct authority guiding the implementation of our work. Interdisciplinary work and creative solutions are crucial to plan for and adapt to greater pressure on our water resources.

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Ecology of the macrophyte Podostemum ceratophyllum Michx. (Hornleaf riverweed), a widespread foundation species of eastern North American rivers

Cited by 12 publications

References 66 publications

Invasive macrophytes induce context‐specific effects on oxygen, pH, and temperature in a hydropeaking reservoir

Invasive macrophytes induce context‐specific effects on oxygen, pH, and temperature in a hydropeaking reservoir

Water velocity regulates macro‐consumer herbivory on the benthic macrophyte Podostemum ceratophyllum Michx.

How low is too low? Partnering with stakeholders and managers to define ecologically based low‐flow thresholds in a perennial temperate river

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