Dynamics of nutrients, total organic carbon, prokaryotes and viruses in onboard incubations of cold-water corals

Abstract

The potential influence of the cold-water corals (CWCs) <I>Lophelia pertusa</I> and <I>Madrepora oculata</I> on the dynamics of inorganic nutrient and total organic carbon (TOC) concentrations and the abundances of prokaryotes and viruses in bottom water was assessed in onboard incubation experiments. Ammonium, nitrite, dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and TOC concentrations and N:P ratios were typically higher in incubation water with corals than in controls, whereas nitrate concentrations did not reveal a clear trend. Mucus release (normalized to coral surface) was estimated by the net increase rate of TOC concentrations and averaged 23 ± 6 mg C m⁻² h⁻¹ for <I>L. pertusa</I> and 21 ± 8 mg C m⁻² h⁻¹ for <I>M. oculata</I>. Prokaryotic and viral abundance and turnover rates were typically stimulated in incubation water with corals. This estimated prokaryotic stimulation averaged 6.0 ± 3.0 × 10⁹ cells m⁻² h⁻¹ for <I>L. pertusa</I> and 8.4 ± 2.9 × 10⁹ cells m⁻² h⁻¹ for <I>M. oculata</I>, whereas the estimated viral stimulation averaged 15.6 ± 12.7 × 10⁹ particles m⁻² h⁻¹ for <I>L. pertusa</I> and 4.3 ± 0.4 × 10⁹ particles m⁻² h⁻¹ <I>M. oculata</I>. Our data suggest that prokaryotes and viruses are released from corals and that nutrient and mucus release enhanced prokaryotic and viral production. The result of this stimulation could be a fuelling of bottom water in CWC reefs with nutrients and organic matter and consequently an enhancement of microbe-mediated processes.