Nickel uptake in Symbiodynium spp. and host cnidarian -assessment using the model cnidarian Exaiptasia pallida.

Supervisor: Amanda Reichelt-Brushett (Cross University Australia).
Nickel (Ni) is common marine pollutant and derived from discharge of industries, mining and agriculture. Elevated Ni concentrations, could be harmful the organisms in marine environment such as corals reef. Corals and sea anemones are cnidarians and many species are host to algae known Symbiodinium spp. that live in the host in a symbiotic relationship. The sea anemones Exaiptasia pallida has been widely used for toxicity tests in the laboratory because it is easy to maintain and culture in contained aquarium conditions. To understand the pathway of uptake and storage of elevated Ni between the sea anemone host and symbiotic algae, and the model sea anemone E pallida was exposed to three different Ni concentrations (500 µg/L, 1000 µg/L, 2000 µg/L) and control treatment over 9 days and 18 days. Ni accumulation was assessed in both the host anemone tissues and the Symbiodinium spp. The concentration of Ni was measured using Perkin Elmer NexION 300D ICPMS (Inductively Couple Plasma Mass Spectrophotometry) after sampel digestion. The statistical analysis was completed using R version 3.5.0 (R core team 2013). R Foundation for Statistical Computing, Vienne, Austria. The model was chosen by Akaike Information Criterion (AIC) after to comparing between model options. Shapiro-Wilks test was used to verify the normal

distribution of the date set to be analysed. The overall result showed the accumulation of nickel was highest in Symbiodinium spp.

(212.62 + 50.12 mg/Kg) after a 9 days exposure period in concentration 2000 µg/L while 18 days exposure period was less ( 129.66 + 31,94 mg/Kg) in concentration 2000 µg/L. The lower uptake of Ni in Symbiodinium spp. in the longer exposure time of 18 days compare to 9 days exposure might be due to the ability of Symbiodinium spp. to release the Ni through their metabolism or the Ni dose may have inhibited normal function of the algae, although the accumulation of both times period was significantly higher than the control treatments. Meanwhile, host anemones accumulated 77.43 + 6.28 mg/Kg Ni over 9 days exposure period and the 2000 µg/L treatment and increased after 18 days exposure in concentration 2000 µg/L ( 45.54 + 4.12 mg/Kg), both of which are significantly greater concentration of Ni compare to the control treatments. This result suggest that the highest Ni treatment influenced the normal function of the anemone and is a similar finding to the Symbiodinium spp. result. The result of these finding highlight the importance of understanding the metal accumulation in host and cnidarian. This is particularly important if these species are used in biomonitoring studies where bleaching may occur due to stress, but may in effect be a depuration pathway for metal load, masking the biological uptake and interaction between metal and organisms.