Summary In previous work, lab‐scale reactors designed to study microbial Fe(II) oxidation rates at low pH were found to have stable rates under a wide range of pH and Fe(II) concentrations. Since the stirred reactor environment eliminates many of the temporal and spatial variations that promote high diversity among microbial populations in nature, we were surprised that the reactors supported multiple taxa presumed to be autot...

Summary Marine sponges are diverse, abundant and provide a crucial coupling point between benthic and pelagic habitats due to their high filtration rates. They also harbour extensive microbial communities, with many microbial phylotypes found exclusively in sponge hosts and not in the seawater or surrounding environment, i.e. so‐called sponge‐specific clusters ( SCs ) or sponge‐ and coral‐specific clusters ( SCCs ). We employe...

Summary Marine sponges often contain diverse and abundant communities of microorganisms including bacteria, archaea and eukaryotic microbes. Numerous 16S rRNA‐based studies have identified putative ‘sponge‐specific’ microbes that are apparently absent from seawater and other (non‐sponge) marine habitats. With more than 7500 sponge‐derived rRNA sequences (from clone, isolate and denaturing gradient gel electrophoresis data) now...