SPATIAL AND SEASONAL PATTERNS IN MACROPHYTE-ASSOCIATED TOXIC CYANOBACTERIA AND THEIR TOXINS: A CASE STUDY FROM A TEMPERATE LAKE

Benthic cyanobacteria produce potent toxins, with anatoxins (ATXs) implicated in numerous recent dog poisoning incidents. Some benthic cyanobacteria attach to submerged macrophytes, facilitating transport to beaches and posing potential risks to humans and animals. The specific interactions and conditions supporting macrophyte-associated cyanobacteria are not well understood. Climate change, with its impact on temperature and seasonal shifts, further complicates cyanobacterial dynamics, potentially enhancing the spread and toxicity of these microorganisms.We analyzed macrophyte-associated cyanobacteria occurrence across transects and depths in Lake Tegel (Berlin, Germany) monthly for one year, beginning in May 2023. This dimictic temperate lake has experienced macrophyte recolonization due to nutrient load reduction, increased water clarity, and a quagga mussel invasion in 2013. Cyanobacteria presence on macrophytes was assessed microscopically, with ATXs quantified from biofilms and water samples analyzed for nutrient concentrations. We focused on Fontinalis antipyretica, a rootless wintergreen water moss occasionally washed ashore. Samples were collected from four transects and two additional locations. Only one additional site consistently showed high toxin levels. Microcoleus, a known toxic genus, was linked to sample toxicity, and Oscillatoriales and Nostocales were identified microscopically, by cultivation, and PCR. PCR indicated anaC-osc genes in samples with the highest ATX levels. An underwater camera detected dense red-brown mats covering macrophytes in October and November, which correlated with peak toxin concentrations (ATX-a 418 µg/g d.w., DhATX 68.6 µg/g d.w., HATX 0.8 µg/g d.w.).

Presentation Preference: Oral

Primary Presenter: Nikola Stankovic, University of Nis (nikola.stankovic@pmf.edu.rs)

Authors:

Nikola Stankovic, University of Nis  (nikola.stankovic@pmf.edu.rs)

Sven Meissner, IGB Berlin  (sven.meissner@igb-berlin.de)

Jutta Fastner, UBA Berlin  (jutta.fastner@uba.de)

Michael Monaghan, IGB Berlin  (michael.monaghan@igb-berlin.de)

Sabine Hilt, IGB Berlin  (sabine.hilt@igb-berlin.de)