Jellyfish distribute vertically according to irradiance

Area of Science:

• Marine Biology
• Jellyfish Ecology
• Benthic Ecology

Background:

• The coronate jellyfish, Periphylla periphylla, is known for mass occurrences in Norwegian fjords.
• Understanding jellyfish vertical distribution is crucial for marine ecosystem dynamics.

Purpose of the Study:

• To test the hypothesis that Periphylla periphylla distributes vertically according to preferred absolute light intensities.
• To investigate the relationship between light levels and the vertical migration of P. periphylla.

Main Methods:

• Vertical distribution data of P. periphylla medusae were collected using remotely operated vehicle (ROV) video observations.
• Data were gathered during day, dusk, and night periods in Lurefjorden, Norway.
• Ambient light levels (irradiance) were estimated in relation to jellyfish distribution.

Main Results:

• Large P. periphylla (approx. 9 cm diameter) avoided irradiance levels above 5×10⁻³ µmol quanta m⁻² s⁻¹.
• Approximately two-thirds of the population remained above 10⁻⁷ µmol quanta m⁻² s⁻¹ during daytime.
• Some individuals were observed in significantly darker waters, indicating varied responses.

Conclusions:

• Periphylla periphylla exhibits vertical distribution patterns influenced by a preferential range of absolute light intensities.
• The findings suggest that P. periphylla undertakes diel vertical migration (DVM) in response to light cues.
• Light intensity is a key factor regulating the vertical positioning of this jellyfish species in its natural habitat.