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Keynote speakers

16th International Symposium on Aquatic Plants

Here are the Keynote speakers in alphabetical order.

Coetzee, Julie A.


Title and Affiliation: Assoc. Professor, Centre for Biological Control, Rhodes University, Grahamstown, South Africa

Title of talk: Recent developments in control of aquatic macrophytes: insights from Sub-Saharan African

Abstract: Sub-Saharan Africa, and particularly southern Africa, has a long history of managing the establishment and spread of invasive floating macrophytes. The past thirty years of research and the implementation of biological and integrated control programmes has led to widespread control of these species in many degraded freshwater ecosystems. Such initiatives are aimed at restoring access to potable freshwater and maintaining native biodiversity. However, in recent years, there has been a decline in populations of floating invasive plants, and an increase in the establishment and spread of submerged and emergent invasive plant species, which poses significant threats to aquatic ecosystems. This talk highlights the vulnerability of Africa’s eutrophic systems to successful colonisation by this suite of new macrophytes following the successful biological control of floating invasive macrophytes, and explores a new regime shift in invasive populations partly driven by biological control. A more holistic approach to the control of invasive aquatic plants is required to ensure long-term ecosystem recovery and sustainability as Sub-Saharan Africa faces the pressures imposed by global climate change.


Maberly, Stephen C.


Title and Affiliation: Professor, Centre for Ecology and Hydrology, Lancaster, UK

Title of talk: Putting the C into maCrophytes.

Abstract: Carbon is the major element required by plants. When freshwater macrophytes evolved from terrestrial ancestors and moved into water they traded-off potential problems of water-limitation for problems of carbon limitation, because the underwater supply of dissolved inorganic carbon is often slow and unreliable compared to CO2 in air. This talk will discuss the morphological, physiological and biochemical mechanisms that different freshwater macrophytes have evolved to minimise carbon limitation, and the consequences of these for their ecology.


Scholz, Vincent V.


Title and Affiliation: PhD student, Aarhus Unviersity, Denmark

Title of talk: What´s current in the rhizosphere of aquatic plants?

Abstract: In marine and freshwater sediments aquatic plants can release oxygen into the rhizosphere, which protects the roots from toxic sulfide by biotic and abiotic oxidation of sulfide.
Therefore, the rhizosphere could be an ideal environment for long-distance electron transport, mediated by sulfide-oxidizing cable bacteria, which indeed have recently been found associated with seagrass roots.
Our results revealed high cable bacteria densities at the oxic-anoxic transition zone next to roots of the freshwater plants Littorella uniflora using a combination of fluorescence in situ hybridization (FISH) and oxygen sensitive planar optodes. Scanning electron microscopy showed cable bacteria along root hairs. Electric potential measurements showed an electric field over centimeters from the roots indicating active sulfide oxidation and oxygen reduction by the cable bacteria. Cable bacteria were also found globally distributed in the rhizosphere of various aquatic plants in salt- and freshwater systems, including a saltmarsh, high alpine lake and paddy field, implying that the plant root - cable bacteria interaction is a generic property in the rhizosphere of aquatic plants and thus turning the rhizosphere into an electric environment. The electric imprint not only alters rhizosphere processes, but also has climate relevant implications on a global scale.


Soons, Merel B.


Title and Affiliation: Assoc. Professor, Utrecht University, The Netherlands

Title of talk: Dispersal ecology of aquatic and riparian plants: release, transport and arrival.

Abstract: Plant species around the world invest in seed dispersal by producing large numbers of seeds, with a wide range of morphological adaptations that facilitate dispersal. Not all dispersed seeds reach suitable sites, however, and plants can significantly improve their fitness by increasing the proportion of seeds arriving at suitable sites for germination and establishment. Disproportionate dispersal to suitable sites is known as ‘directed dispersal’.

Riparian ecosystems span the gradient from aquatic to terrestrial communities. Vegetation communities along this gradient usually show clear spatial sorting, where plant species inhabit a species-specific hydrologic niche. In such a system, directed dispersal greatly enhances species fitness if seeds arrive disproportionally at suitable sites along the hydrological gradient.

We demonstrate that wetland plants produce seeds with adaptations to promote transportation and deposition by water towards microsites along the hydrological gradient where they germinate and establish best. Aquatic species produce seeds that sink and are transported by water as bed load towards inundated sites. In contrast, shoreline species produce seeds that float for very long periods of time so that they are eventually entrapped by shoreline vegetation or deposited at the waterline. Wind dispersal and dispersal by waterbirds are more complex. Wind simply appears to be the best available dispersal vector for more terrestrial wetland plant species to reach drier areas in a wet environment. Dispersal by waterbirds allows directed dispersal at larger spatial scales, as it allows species in riparian ecosystems to cross terrestrial areas and move between riparian ecosystems that are unconnected by water flows.





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