Indications of a benthic foraminifer Cribrononion gnythosuturatum to salinities revealed by eDNA metabarcoding and morphological methods

Cribrononion gnythosuturatum is a widely distributed benthic foraminifer. However, its adaptability to salinity changes is still poorly understood. To investigate the response of C. gnythosuturatum to salinity changes, sediment samples were collected from an intertidal zone of the Yellow Sea and cultured at 13 salinity gradients from 0 to 60 psu for 10 weeks. The results of the culture experiments were analyzed using morphological and eDNA methods. The results showed that extremely high tests broken rate at low salinities (<15 psu). Under high salinities (>50 psu), the stained protoplasm was concentrated in the center of the chambers. Meanwhile, both morphological and eDNA metabarcoding results showed that under abnormal salinity conditions (15-25 psu or 40-50 psu), the abundance, relative abundance and growth rate of C. gnythosuturatum reached the maximum value, while the tests were well preserved. This study reveals the mechanism by which C. gnythosuturatum is used as a salinity indicator for paleoenvironments.