Reviews and syntheses: Salinity-dependent algae uptake and subsequent carbon and nitrogen metabolisms of two intertidal foraminifera (<i>Ammonia tepida</i> and <i>Haynesina germanica</i>)

• Main Authors: M. Lintner, B. Biedrawa, J. Wukovits, W. Wanek, P. Heinz
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-07-01
• Series: Biogeosciences
• Online Access: https://www.biogeosciences.net/17/3723/2020/bg-17-3723-2020.pdf

<p>Benthic foraminifera are abundant marine protists which play an important role in the transfer of energy in the form of organic matter and nutrients to higher trophic levels. Due to their aquatic lifestyle, factors such as water temperature, salinity and pH are key drivers controlling biomass turnover through foraminifera. In this study the influence of salinity on the feeding activity of foraminifera was tested. Two species, <i>Ammonia tepida</i> and <i>Haynesina germanica</i>, were collected from a mudflat in northern Germany (Friedrichskoog) and cultured in the laboratory at 20&thinsp;<span class="inline-formula">^∘</span>C and a light–dark cycle of 16:08&thinsp;h. A lyophilized algal powder from <i>Dunaliella tertiolecta</i>, which was isotopically enriched with <span class="inline-formula">¹³</span>C and <span class="inline-formula">¹⁵</span>N, was used as a food source. The feeding experiments were carried out at salinity levels of 11, 24 and 37 practical salinity units (PSU) and were terminated after 1, 5 and 14&thinsp;d. The quantification of isotope incorporation was carried out by isotope ratio mass spectrometry. <i>Ammonia tepida</i> exhibited a 10-fold higher food uptake compared to <i>H. germanica</i>. Furthermore, in <i>A. tepida</i> the food uptake increased with increasing salinity but not in <i>H. germanica</i>. Over time (from 1–5 to 14&thinsp;d) food C retention increased relative to food N in <i>A. tepida</i> while the opposite was observed for <i>H. germanica</i>. This shows that if the salinity in the German Wadden Sea increases, <i>A. tepida</i> is predicted to exhibit a higher C and N uptake and turnover than <i>H. germanica</i>, with accompanying changes in C and N cycling through the foraminiferal community. The results of this study show how complex and differently food C and N processing of foraminiferal species respond to time and to environmental conditions such as salinity.</p>