| Summary: | This study evaluates the bioavailability of trace metals to microalgae in Vulcano, Italy, where naturally occurring undersea CO2 vents create a pH gradient. Volcanic vent sites are ideal locations to study long-term effects of acidification and warming on metal biogeochemistry. The impacts of ocean acidification are often studied in controlled mesocosms with attention to biological response, however the additional response of seawater chemistry to acidifi cation on biology is largely unknown. Six stations were selected along a pH gradient from the main vent to a control site with samples taken between March and May 2013. Biofilms were grown at one metre depth over 15 days, and samples taken of seawater and sediment. Diatom species assemblages were captured using an scanning electron microscope (SEM), and inductively coupled plasma mass spectrometry (ICP-MS) for trace metals from all samples. The results from each the biofilm, seawater, and sediment were compared to establish an analogue for trace metal bioavailability with specific interest in the relationship of Fe and diatoms.
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