Bulbils of some charophytes

Bharathan, Seema

doi:10.1007/bf03053351

Cited by 8 publications

(2 citation statements)

References 5 publications

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“…Asexual reproduction also occurs more commonly through starch-filled outgrowths of the rhizoids called bulbils which may become abundant on plants and eventually are shed and become buried within the substrate, persisting throughout the year (Wood & Imahori, 1965;Casanova, 1994) and which may ultimately germinate separate from the thallus. Still more common is asexual reproduction (and hibernation) by starch-filled node cells, as in the case of Nitellopsis obtusa (Bharathan, 1987). As is the case for many starch-packed Charophyte structures, if a consumer organism is able to dissolve and free their contents from calcified structures, they are potentially highly attractive to organisms browsing such structures or dabbling in substrates where they can accumulate (for example due to water currents) in some abundance as an easy source of concentrated energy.…”

Section: Topical Reviewmentioning

confidence: 99%

Interactions between stoneworts (Charales) and waterbirds

Fox,

Stīpniece

2023

Biological Reviews

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Stoneworts (Charales) are green algae that represent an important food resource for many waterbird species in Europe and elsewhere. Browsing avian herbivores (e.g. swan, goose, duck and coot species) consume Charales plant vegetative parts, by head‐dipping, up‐ending or diving. A lower fibre content and longer growing season may make Charales as attractive to such herbivores as sympatric submerged higher plant species in some circumstances. Charales respond to environmental stress (e.g. drought) by producing abundant diaspores, in the form of oospores (sexual) and bulbils (asexual), both rich in starch, generating abundant food for waterbirds at critical stages in their annual migratory cycles. Waterbirds feed on these by diving (e.g. common pochard Aythya ferina and red‐crested pochard Netta rufina) or by filtering from the water column (e.g. dabbling duck species), ensuring dispersal of sexually produced and vegetative diaspores locally (because of predator swamping) and remotely (through endo‐ and ectozoochorous dispersal by long‐distance migratory waterbirds). Greater invertebrate density and diversity associated with Charales canopies enhances their attractiveness over other submerged macrophyte beds to diving predators [e.g. tufted duck Aythya fuligula, common pochard and Eurasian coot Fulica atra (hereafter coot)]. Fish fry preying on these invertebrates use such vegetation as predator cover, in turn providing prey for avian piscivores such as grebes and cormorants. Abundant Charales contribute to maintaining a transparent water column due to canopy density, nutrient effects, dampening of sedimentation/remobilisation of suspended matter and nutrients and allelopathic effects on other plants (especially phytoplankton). Shallow, relatively eutrophic waters can flip between clear‐water high‐biodiversity (where Charales thrive) and turbid species‐poor depauperate stable states (lacking Charales). Shifts between turbid conditions and rich submerged Charales beds have profound elevating effects on aquatic diversity, to which waterbirds show rapid aggregative responses, making them ideal indicator species of ecological change; in the case of Charales specialists (such as red‐crested and common pochard), indicators of the presence and abundance of these plants. Large‐bodied colonial nesting birds (e.g. cormorants, gulls, heron and egrets) aggregating along lake shores contribute high N and P loadings to water bodies sensitive to such external and internal inputs and can cause local eutrophication and potential loss of Charales. Despite variation from complete seasonal removal of Charales biomass to undetectable grazing effects by herbivorous birds, evidence suggests little effect of avian grazing on biomass accumulation or the stability of community composition (under otherwise stable conditions), but we urge more research on this under‐researched topic. We also lack investigations of the relative foraging profitability of different Charales organs to waterbirds and the degree of viability of gyrogonites (fertilised and calcified oospores), vegetative bulbils and plant fragments after passage through the guts of waterbirds. We especially need to understand better how much the carbonate armour of these organs affects their viability/dispersal via waterbirds and urge more research on these neglected plants and their relationships and interactions with other organisms in the aquatic biota.

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Section: Topical Reviewmentioning

confidence: 99%

Interactions between stoneworts (Charales) and waterbirds

Fox,

Stīpniece

2023

Biological Reviews

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“…The presence of both antheridia and oogonia-bearing starry stonewort in North America could change the life history strategy of this species and allow for spread via sexual reproduction. Vegetative reproduction currently occurs through development of star-shaped bulbils, from which the common name is derived, that serve as a form of sexual reproduction and allow for dispersion through space and time (Bharathan 1987).…”

Section: Introductionmentioning

confidence: 99%

Environmental factors influencing biomass and bulbil production of Nitellopsis obtusa in Lake Koronis, Stearns County, Minnesota

Carver,

Wersal,

Gebhart

2024

J Aquat Plant Manage

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Starry stonewort [Nitellopsis obtusa (Desvaux) J. Groves] is a green macroalga in the family Characeae that is native to Eurasia. In the United States it has invaded many waterbodies across the northern tier from New York to Minnesota. In Minnesota, starry stonewort often grows later into the growing (September to December) season than most native species; however, the environmental factors that influence this life history trait are not well understood. Starry stonewort was harvested every 3 wk from May to November in 2020 and 2021 from four locations in Lake Koronis, Stearns County, MN. Light, water pH, and water temperature were also collected to correlate these variables to starry stonewort growth. Rhizoid biomass had weak negative correlations with temperature (rs ¼ 0.19) and pH (rs ¼ 0.14). Bulbil biomass had weak negative correlations with temperature (rs ¼ 0.24), pH (rs ¼ 0.31), and light transmittance (rs ¼ 0.11). Bulbil density had weak negative correlations with temperature (rs ¼ 0.23), pH (rs ¼ 0.29), and light transmittance (rs ¼ 0.10). Bulbil production was highest between October and November of each year. Bulbil biomass and density was lower in 2020 (4.6 g m2 and 1,229 bulbils m2) thanin2021(14.7gm2 and 5,211 bulbils m2). The average annual bulbil density was 1,537 bulbils m2 and ranged from 0 to 157,000 bulbils m2. The ability of starry stonewort to grow in dense mats and produce large quantities of bulbils contributes to the difficulty of controlling infestations. Bulbils are a method of spatial and temporal distribution that can allow for recolonization of previously treated areas.

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The non-native charophyte Nitellopsis obtusa (starry stonewort) influences shifts in macrophyte diversity and community structure in lakes across a geologically heterogeneous landscape

Harrow-Lyle

Kirkwood

2022

Aquat Ecol

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Bulbils of some charophytes

Cited by 8 publications

References 5 publications

Interactions between stoneworts (Charales) and waterbirds

Interactions between stoneworts (Charales) and waterbirds

Environmental factors influencing biomass and bulbil production of Nitellopsis obtusa in Lake Koronis, Stearns County, Minnesota

The non-native charophyte Nitellopsis obtusa (starry stonewort) influences shifts in macrophyte diversity and community structure in lakes across a geologically heterogeneous landscape

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