Characterisation of artisanal mine waste on Buru Island, Indonesia and toxicity to the brittle star Amphipholis squamata.

Artisanal small-scale gold mining (ASGM) using mercury (Hg) amalgamation commenced on Buru Island, Indonesia, in 2012, but was halted in 2015 due to concerns of widespread Hg contamination. Much of the Hg used in the mining process is lost to trommel waste which is disposed of in settlement ponds that drain into adjacent waterways and into Kayeli Bay. Several thousand unmanaged trommel sites and associated tailing ponds exist on Buru Island. This study shows that waste from the Marloso trommel at the Gogrea site contained 203 mg/kg total Hg (THg), with a negligible proportion present as bioavailable methyl Hg (MeHg) and a low total organic carbon content. There are currently very few tools available for ecotoxicological risk assessment of mine tailings for tropical marine ecosystems, and we support the development of Tailings Toxicity Tests (TTTs) and describe laboratory toxicity test methods using the cosmopolitan benthic echinoderm Amphipholis squamata. Undiluted trommel waste caused 100% mortality of A. squamata within 48 h, and a 96-h LC50 of 6.7% w/w trommel waste (4 mg/kg THg) was estimated. Sub-lethal effects on the water vascular system of the brittle star were assessed by quantification of the Ability to Right Itself (ARI), and a 48-h EC50 of 7.3% w/w trommel waste (14.4 mg/kg THg) was estimated. The results show that trommel waste produced on Buru Island is highly contaminated with THg and is acutely toxic, raising serious concern for receiving ecosystems where Hg methylation to more toxic and bioavailable forms is likely.

Effects of Cd, Co, Cu, Ni and Zn on asexual reproduction and early development of the tropical sea anemone Aiptasia pulchella.

Currently few studies present sub-lethal toxicity data for tropical marine species, and there are no routine toxicity tests using marine cnidarians. The symbiotic sea anemone Aiptasia pulchella has been identified as a useful species for ecotoxicological risk assessment, and would provide a tropical marine cnidarian representative. Chronic sub-lethal toxicity tests assessing the effects of 28-day trace metal exposure on asexual reproduction in A. pulchella were investigated, and concentration-dependant reductions in the number of offspring that were produced were evident for all metal exposures. Metal concentration estimates causing 50% reductions in the numbers of asexually-reproduced juveniles after 28-day exposures (28-day effect concentrations 50%: EC50s) were 14 µg/L for copper, 63 µg/L for zinc, 107 µg/L for cobalt, 145 µg/L for cadmium, and 369 µg/L for nickel. Slightly higher 28-day EC50s of 16 µg/L for copper, 192 µg/L for zinc, 172 µg/L for cobalt, 185 µg/L for cadmium, and 404 µg/L for nickel exposures and were estimated based on reductions in the total number of live developed and undeveloped offspring. These sensitive and chronic sub-lethal toxicity estimates help fill the knowledge gap related to metal effects on cnidarians over longer exposure periods, and this newly-developed bioassay may provide a much needed tool for ecotoxicological risk assessment relevant to tropical marine environments.

Development of a chronic, early life-stage sub-lethal toxicity test and recovery assessment for the tropical zooxanthellate sea anemone Aiptasia pulchella.

There is an urgent need to identify additional tropical marine species and develop sensitive sub-lethal and chronic toxicity test methods for routine ecotoxicology. The tropical symbiotic sea anemone Aiptasia pulchella is a suitable species for use in ecotoxicology and here we have assessed the effects of trace metal exposures on the development of asexually produced A. pulchella pedal lacerates to a juvenile stage. Concentrations of 55 µg/L for cadmium, 262 µg/L for cobalt, 5 µg/L for copper, and 269 µg/L for zinc were estimated to inhibit normal development by 50 percent after 8-d exposures, and are among the most sensitive available toxicity estimates for marine organisms. This work illustrates the potential value of this species and sub-lethal toxicological endpoint for routine ecotoxicology in tropical marine environments.