Effect of Nanoparticles on DMS Consumption and DMSP Concentration in Aiptasia pallida

Abstract

Wide use of nanoparticles (NPs) in day-to-day products increases the likelihood of NPs entering and effecting marine organisms as a result of direct emissions and indirect terrestrial runoff. The effects of NPs on dimethylsulfide (DMS) consumption and concentrations of dimethylsulfoniopropionate (DMSP) within the holobiont of cnidarians remain obscure. This study examines the effects of titanium dioxide (TiO2 NP) and capped silver nanoparticles (cAg NP) at 50mg/L concentrations, on the microscopically observations of physiological changes to the tropical sea anemone, Aiptasia pallida (clone CC7), the concentrations of DMS and DMSP of its intracellular symbiont Symbiodinium sp. (A02 and B01) and its surface DMS consuming bacteria. DMS was quantified during NP exposure, and 24 and 96h post exposure using gas chromatography (GC). DMS production was found to be 2.5 fold higher in A02 compared to B01. However, concentrations of particulate DMSP were only observed to increase in the B01 strain when exposed to TiO2 NP (22.90±1.55nmol h-1mg-1) compared to control (11.41±0.05nmol h-1mg-1). A common pattern was identified for the surface DMS consuming bacteria on A. pallida, regardless of Symbiodinium strain or NP treatment. During NP exposure DMS consumption was lower in all NP treatments (0.10±0.05nmol h-1mg-1) in comparison to the controls (0.19±0.19 nmol h-1mg-1). 24h post exposure, DMS consumption was higher (0.27±0.13 nmol h-1mg-1) compared to the controls (0.20±0.22nmol h-1mg-1), with DMS consumption returning to similar rates as controls in NP treatments post 96h exposure. Microscopical observations showed that cAg NP had the greatest adverse effect on both Symbiodinium strains, with approximately 40% decrease in cell density after 24h exposure, and loss of tentacles in A. Pallida being observed only in this NP treatment. This work illustrates the potentially negative impacts of NPs on DMS consumption and concentrations of DMSP in the holobiont of A. pallida, thus emphasising the need for more studies to be conducted on NP effects in the tropical marine environments.