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Image by Laura Nyhuis

Jellyfish Blooms

Jellyfish are becoming more common in the Marmara Sea—and it’s not just a coincidence. As sea temperatures rise and fish populations drop due to overfishing, jellyfish are thriving in the gaps left behind.
 
With fewer predators and more plankton to eat, they’ve begun to bloom in record numbers, especially near coasts. Jellyfish are made up of 95% water and have no true stomach, relying on a simple cavity to absorb food.
 
While they may seem harmless, large jellyfish swarms can disrupt fishing, sting swimmers, and signal deeper imbalances in the sea. Their growing presence tells a story: when ecosystems shift, new ones form—often in unexpected ways.

Jellyfish Sightings

Of the project’s 285 reports, 82 contained at least one named jellyfish identification, while additional reports documented abundance, size, or whether jellyfish were observed in the sea or along the shore.

 

Ay Denizanası was by far the most frequently reported jellyfish type, appearing in 72 reports and accounting for 87.8% of reports containing a named identification. This suggests that it was either particularly common, widely distributed, or more readily recognized by participants than other reported types.

 

Most abundance observations involved small groups of between one and ten jellyfish. However, higher-density events were also notable. Nearly one-quarter of valid abundance responses documented at least 51 jellyfish, including seven reports of more than 100 individuals. This indicates that although low-number sightings were most common, concentrated aggregations occurred in a meaningful subset of observations.

 

Small and medium-sized jellyfish were reported at similar frequencies, while large adults were less common. More than two-fifths of size reports indicated mixed sizes or multiple life stages within the same observation. This may point to seasonal or spatial variation in jellyfish populations, although further analysis by month, location, and reported species is required before drawing ecological conclusions.

 

Jellyfish were more frequently reported in the sea than only along the shore. Approximately two-thirds of valid location responses described jellyfish in the water, while just over one-third documented shore-only observations. This suggests that the dataset reflects both active marine presence and coastal accumulation or stranding events.

 

Overall, the findings show a persistent but variable jellyfish presence across the surveyed region. Future cross-analysis of species, abundance, size, season, and location will help identify whether high-density events and different life stages cluster within particular geographic areas or periods of the year

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