Hippos pump silicon, vital for aquatic life

Hippos are now understood to be significant 'animal silicon pumps,' transferring vital silicon from terrestrial grasslands into rivers. Researchers found that through their daily routine of grazing and depositing dung in water, hippos can move approximately 0.4 metric tonnes of silicon into Kenya's Mara River on a dry-season day. This input is crucial because silicon is essential for diatoms, microscopic algae that underpin aquatic food webs. The study, published in Science Advances, estimated that hippos might influence up to 76% of the silicon flux in the studied river reach.

The biogenic silicon content in hippo dung was found to be significantly higher than in the grass they consume. Laboratory tests also indicated that silicon dissolves more readily from dung than from undigested grass. While these findings highlight the connection between large animals and riverine ecosystems, researchers caution that the estimates are based on dry-season observations in one river. Further research is needed to understand the full impact on aquatic food webs and potential consequences like algal bloom dynamics.