Fish mitigate trophic depletion in marine cave ecosystems

Area of Science:

• Marine Biology
• Ecology
• Ichthyology

Background:

• Marine caves are food-limited environments due to lack of light and restricted water flow.
• Reduced organic matter influx impacts organisms within these unique habitats.

Purpose of the Study:

• To investigate the trophic role of the cardinalfish (Apogon imberbis) in Mediterranean marine caves.
• To determine if Apogon imberbis functions as a trophic vector, linking cave and external ecosystems.

Main Methods:

• Analysis of cardinalfish stomach contents to assess diet and feeding patterns.
• Identification of prey items to distinguish between cave-associated and external species.
• Visual census data collection to compare cardinalfish density inside and outside caves during day and night.

Main Results:

• Cardinalfish stomach repletion was highest in the early morning, indicating nocturnal feeding.
• Prey items primarily belonged to species found outside of cave habitats.
• Cardinalfish density was higher inside caves during the day and outside caves at night.

Conclusions:

• Apogon imberbis plays a crucial role in nutrient transfer between Mediterranean marine caves and surrounding environments.
• The cardinalfish's diel (daily) movement patterns facilitate the import of external food resources into cave ecosystems.
• This research supports the hypothesis of Apogon imberbis as a key trophic link in marine cave food webs.