Environmental significance of morphological variations in the foraminifer Ammonia aomoriensis (Asano, 1951) and its molecular identification: A study from the Yellow Sea and East China Sea, PR China

Ammonia aomoriensis (Asano 1951) was isolated from 78 samples collected from the Yellow Sea and East China Sea during 2010 to 2014. The species exhibits dimorphism (microspheric and megalospheric forms) and different coiling directions (dextral and sinistral). A fragment of SSU rDNA was sequenced for four specimens of A. aomoriensis exhibiting different morphologies (dextral vs. sinistral, microspheric vs. megalospheric). Our results show that A. aomoriensis from our study sites branch within previously obtained sequences of the same species. In order to test whether morphological differences are environmentally controlled we investigated 667 specimens from Qingdao and Jiaozhou Bay among which 290 were right coiled (dextral) and 377 were left coiled (sinistral). Similarly, 525 were microspheric and 142 were megalospheric. A correlation coefficient was computed to evaluate the relationship between foraminiferal morphology (dimorphism and coiling direction) and environmental parameters (temperature and salinity). A significant positive correlation was detected between the ratio of microspheric/megalospheric forms and salinity (r = 0.719, p < 0.001). No correlation was detected between morphological variations and temperature. Our findings suggest that the ratio of microspheric/megalospheric forms in A. aomoriensis can be used to infer past salinity conditions (and thus fresh water influx) in study areas off China.