Impact of temperature on intertidal foraminifera: Results from laboratory culture experiment

Abstract

The response of intertidal foraminifera and their morphological characteristics to temperature changes in laboratory microhabitats is poorly studied. Therefore, a benthic foraminiferal community from intertidal sediment of the Yellow Sea was cultured at five constant temperatures (6, 12, 18, 24, and 30 °C) under laboratory microcosm conditions. The culture experiment lasted for 100 days, and four replicates were set up in each temperature treatment. The response of the foraminiferal community (abundance, species richness, Margalef index, Shannon–Wiener diversity, and Pielou's evenness) and species composition to the different temperatures was studied. In total, 6771 living (stained) specimens of benthic foraminifera were obtained. Foraminiferal community abundance varied from 75 to 131 individuals/g dry sediment, at 6 °C and 18 °C, respectively. The statistical analysis showed that temperature had a significant effect on most of the foraminiferal community parameters (p < .01). Most of these parameters increased with an initial increase in temperature until 18 °C or 24 °C but then declined at subsequently warmer temperature. The percentage of living foraminifera among total assemblages generally decreased with increasing temperature. Additionally, species composition was also significantly altered. Temperature had a significantly positive effect on the porcelaneous taxa, while negative one on the hyaline ones. The dominant species (Ammonia aomoriensis, A. tepida, and A. beccarii) showed different optimal temperature limits; that is, Ammonia aomoriensis showed a broader temperature tolerance and a preference for lower temperature (6–12 °C), while Ammonia tepida preferred higher temperature (18–30 °C), and Ammonia beccarii had an intermediate range (12–18 °C). The results of morphometric study indicated that the dominant species responded to temperature in terms of both size and length/width ratio. The major and minor axes of A. beccarii significantly increased at a higher temperature, whereas the length/width ratio of the three dominant species decreased with increasing temperature. Our study indicates that rising temperature could significantly alter not only the community structure but also the chamber morphology of intertidal foraminifera.