Effects of heavy metals (Pb, Cu, Zn) on algal food uptake by Elphidium excavatum (Foraminifera) 

Abstract

<p><span><span>Foraminifera are unicellular organisms which are important for marine C and N processing. Feeding experiments showed that the food uptake and thus the turnover of organic matter are influenced by changes of physical parameters (e.g., temperature, salinity). Since many areas of the Baltic Sea are strongly affected by anthropogenic activity and therefore contaminated by heavy metals from shipping in the past, this study examined the effect of heavy metal pollution on the food uptake of the most common foraminiferal species of the Baltic Sea, </span></span><span><span><em>E</em></span></span><span><span><em>lphidium</em></span></span><span><span><em> excavatum</em></span></span><span><span>. </span></span><span><span>In 2019, we collected water and sediment containing living </span></span><span><span><em>E</em></span></span><span><span><em>.</em></span></span><span><span><em> excavatum</em></span></span><span><span> in </span></span><span><span>the Kiel Fjord</span></span><span><span>. In laboratory experiments,</span></span><span><span> Baltic Sea seawater was enriched with metals at various levels above normal seawater: Zn (9.2-, 144- and 1044-fold), Pb (2.4-, 48.5- and 557-fold) and Cu (5.6- and 24.3-fold), and the </span></span><span><span>foraminiferal </span></span><span><span>uptake of </span></span><span><sup><span>13</span></sup></span><span><span>C- and </span></span><span><sup><span>15</span></sup></span><span><span>N-labelled phytodetritus was measured by isotope ratio mass spectrometry. Significant differences in food uptake were observable at different types and levels of heavy metals in sea water. An increase in the Pb concentration did not affect food uptake, whereas strong negative effects were found for high levels of Zn and especially for Cu. Interestingly, experiments with short incubation periods (1 and 5 days) showed greater differences in food uptake </span></span><span><span>from undisturbed conditions </span></span><span><span>than those of longer incubation times (10 and 15 days). In summary, an increase in the heavy metal pollution in the Kiel Fjord will likely lead to a significant reduction in the turnover of organic matter by foraminifera such as </span></span><span><span><em>E. excavatum</em></span></span><span><span>.</span></span></p>

Assimilation of Particular Organic Matter and Dissolved Organic or Inorganic Compounds by Cribroelphidium selseyense (Foraminifera)

“…A possible explanation could be the seasonal lifestyle of the foraminifera. In the study of Lintner et al (2021b) the foraminifera were collected in autumn, whereas the foraminifera in this study were collected in summer. The seasonality of foraminiferal activity in combination with a phytodetrital pulse has been often discussed in literature (e.g., Kitazato et al, 2000).…”

“…All algae, except of L. arenaria and D. tertiolecta are common in the Baltic Sea. These two algae (L. arenaria and D. tertiolecta) were also tested, because they are very common algae in feeding experiments and have been used several times with foraminifera (e.g., Lintner et al, 2021b). Further, dissolved inorganic compounds (CO 3 2− , NH 4…”

“…Especially a fresh D. tertiolecta diet was not favored in contrast to that of other offered algae. To analyze the food uptake of C. selseyense at different salt concentrations we also offered D. tertiolecta (also 5 mg freeze-dried algae per dish) in past experiments as a food source and observed a C uptake between 0.04 and 0.1 µg/mg and an N uptake of 0.02-0.06 µg/mg after 15 days (Lintner et al, 2021b). In the study here we observe a C uptake of approximately 0.02 µg/mg and an N uptake of 0.01-0.05 µg/mg.…”

“…This is of particular interest, when analyzing the effect of environmental parameters on C. selseyense, because a higher food uptake of foraminifera can lead to a better interpretation of the results from such feeding experiments. Furthermore, dissolved heavy metal concentrations (Lintner et al, 2021b) or the light regime (Lintner et al, 2021a) can affect the feeding and the metabolic activity of foraminifera. In this case, it could be shown, that an enrichment of Cu led to a dramatic increase of the food uptake of C. selseyense, whereas Zn or Pb does not significantly affect the metabolisms of this foraminifera (even for Zn a trend was observed) (Lintner et al, 2021b).…”

“…Furthermore, dissolved heavy metal concentrations (Lintner et al, 2021b) or the light regime (Lintner et al, 2021a) can affect the feeding and the metabolic activity of foraminifera. In this case, it could be shown, that an enrichment of Cu led to a dramatic increase of the food uptake of C. selseyense, whereas Zn or Pb does not significantly affect the metabolisms of this foraminifera (even for Zn a trend was observed) (Lintner et al, 2021b). Additionally, foraminifera show different chloroplast uptake ratios (kleptoplastidy) with different algal diets (Correia and Lee, 2000).…”