In cooperation with international researchers, staff of the ELKH Centre for Ecological Research (CER) have used DNA-based methods to investigate the spread of aquatic prokaryotes (bacteria) and single-celled microeukaryotes by waterfowl through endozoochory, i.e. ingestion. The first comprehensive study on the subject has been published in the Journal of Biogeography.
Dispersal is a key process in terms of connecting habitats and contributing to the maintenance of biodiversity, gene flow and ecosystem functioning. Waterfowl are efficient spreaders of multicellular organisms – such as aquatic vertebrates, macrophytic organisms, macroinvertebrates and zooplankton – but the study of their role in the spread of aquatic microorganisms has so far been relegated to the background, despite modern molecular techniques and an ever-increasing interest in the subject.
The first comprehensive study was completed under the leadership of researchers from CER in cooperation with international co-authors. The study presents the results of a DNA-based examination of the distribution of aquatic prokaryotes (bacteria) and single-celled microeukaryotes by waterfowl through the feeding process.
Photo: Zsolt Kalotás
The research was carried out in Seewinkel National Park (Fertőzug), located in the Hungarian-Austrian border region, where the frequently saline lakes form a suitable habitat network for aquatic organisms. Many waterfowl species find excellent feeding and nesting places in this area of outstanding natural importance, which is also on the UNESCO World Heritage List. The researchers compared the microorganism communities of water samples taken from intermittently saline lakes in two consecutive years and excrement samples from various waterfowl species that visit the area. They initially sought to determine what proportion of the bacteria and eukaryotic protozoa found in the local wetlands were present in the excrement of the region’s dominant greylag goose (Anser anser) and other species. Based on this analysis, they were able to determine the potential number of ‘stowaways’.
The results show that waterfowl can be vectors for all major groups of aquatic organisms, from bacteria to phytoplankton and protozoa. “Based on our study, the spreading ability of bird species was found to be relatively similar, even though they otherwise had quite different lifestyles. Although geese mainly feed in fields and meadows, our research demonstrates that with the simple act of drinking regularly from lakes, they play an equally important role in ensuring connections to species that also obtain their food from lakes,” said Beáta Szabó, a scientific research fellow at the CER Institute of Aquatic Ecology, and a primary author of the study. “From this point of view, the only exception is the northern shoveler (Spatula clypeata), which, thanks to the filter apparatus on its beak – similar to whales’ bristles – was shown to be the most effective spreader of microeukaryote.”
The study provides important evidence for the spread of organisms through nutrition. In addition, it highlights that the role of waterfowl can be decisive in maintaining ecological relationships between wetlands at the level of prokaryotic and unicellular microeukaryotic communities that form the basis of the food web of lakes.
Szabó, B., Szabó, A., Vad, C. F., Boros, E., Lukić, D., Ptacnik, R., Márton, Z., Horváth, Z. (2022) Microbial stowaways: Waterbirds as dispersal vectors of aquatic pro- and microeukaryotic communities. Journal of Biogeography, 49(7): 1286-1298. https://doi.org/10.1111/jbi.14381