Despite the recent invasion of disturbingly buzzing non-biting midges (Chironomidae) along the shores of Lake Balaton, there is no need for concern. As their name suggests, these greenish insects, which rest on coastal vegetation during the day, do not bite, so there is no reason to fear them.
In August, millions of Chironomus balatonicus, known as the Balaton midge, swarmed the shores of Lake Balaton, taking their "summer holiday." Although their presence, particularly in the evening hours, is not very pleasant, researchers from the HUN-REN Balaton Limnological Research Institute (BLRI) emphasise their important role in the lake's nutrient cycle. By consuming algae and developing on them, these midges provide essential food for fish, as well as for birds and amphibians living near the water.
Chironomus balatonicus larvae develop in the lake's sediment and typically emerge in two major waves: one in late spring and early summer, and another in August and September. Their abundance can vary greatly across different areas of the lake, with higher concentrations often found in the Szigliget and Keszthely Basins. The population may also fluctuate from year to year. According to BLRI, this variation is influenced by the availability of microscopic algae, their primary food source. In areas where algae levels were low in the previous period, Chironomidae were almost absent. However, once the concentration of chlorophyll-a, an indicator of algae levels, exceeds 20 micrograms per litre, the population can increase significantly, potentially reaching mass levels with higher algae production.
Interestingly, Chironomus balatonicus was very common in the lake during the 1980s and 1990s, with swarms often much larger and more bothersome than those observed this year. As water quality improved, the algae population declined, leading to a decrease in the midge population. Since the late 1990s, the species has become relatively rare and is mainly found in the western parts of the lake, according to the BLRI website. However, this year, prolonged high water temperatures have also contributed to increased algae levels throughout the lake compared to previous years, resulting in a higher-than-usual population of Chironomidae.
Although these midges do not bite, their sheer number and noisy presence can still be unpleasant. This can be managed during the day by avoiding disturbance of the bushes and trees where they rest and by keeping in mind that these insects are strongly attracted to light at night.