Simulated coal spill causes mortality and growth inhibition in tropical marine organisms

Coal is a principal fossil fuel driving economic and social development, and increases in global coal shipments have paralleled expansion of the industry. To identify the potential harm associated with chronic marine coal contamination, three taxa abundant in tropical marine ecosystems (the coral Acropora tenuis, the reef fish Acanthochromis polyacanthus and the seagrass Halodule uninervis) were exposed to five concentrations (0–275 mg coal l−1) of suspended coal dust (<63 μm) over 28 d. Results demonstrate that chronic coal exposure can cause considerable lethal effects on corals, and reductions in seagrass and fish growth rates. Coral survivorship and seagrass growth rates were inversely related to increasing coal concentrations (≥38 mg coal l−1) and effects increased between 14 and 28 d, whereas fish growth rates were similarly depressed at all coal concentrations tested. This investigation provides novel insights into direct coal impacts on key tropical taxa for application in the assessment of risks posed by increasing coal shipments in globally threatened marine ecosystems.

glued to calcium carbonate pegs and left for a 6 week recovery/acclimation period.
The seagrass species Halodule uninervis is commonly found in coastal Queensland environments, including port areas. H. uninervis was collected at Cockle Bay, Magnetic Island (-19.198578, 146.791696). Cores of intact seagrass were placed in plant pots lined with a plastic bag which was filled with seawater and sealed during transportation to AIMS. Seagrasses were re-potted within 24 hours and maintained in 150 l indoor flow-through holding tanks (27°C, salinity 35.8 ± 0.03 PSU, 12h light:dark photoperiod at ~200 µmol photons m -1 s -1 ) at the National Sea Simulator. Seagrasses were acclimated to the laboratory conditions 4 weeks prior to the commencement of the experiment.
Eight-week-old Acanthochromis polyacanthus were sourced from a captive breeding program at the Marine and Aquaculture Research Facilities Unit, James Cook University, Townsville. Fish were acclimated for 2 weeks to temperature-controlled (27°C, salinity 35.8 ± 0.03 PSU, 12h light:dark photoperiod at ~200 µmol photons m -1 s -1 ) laboratory conditions. Each fish was tagged with an individual fluorescent marker by subcutaneous injection of an elastomer dye with an insulin needle and were left to recover for one week 1 . Fish were randomly assigned to experimental tanks (n = 10 per tank) and were fed once per day with 4 mg of crushed INVE 5/8 enriched food per fish 1 and also had access to the Artemia nauplii provided to the corals. Food was also added to the treatment without fish so that corals were exposed to the same food regime.  10% and 50% of the tested population (IC 10 and IC 50 ) for fish (b) and seagrass (c) were estimated using linear interpolation. Concentrations are plotted on a log scale.

Experimental system
The flow-through coal delivery system was based on that described in Flores et al. 2 (Fig. S3). The base of each aquarium sloped (36°) towards the front of the tank to reduce particles accumulating on the bottom. An external pump (Eheim Compact+ 3000 at 3000 l h -1 : Eheim GmbH, Germany) suctioned particles from the lowest point at the base of each aquarium and resuspended the particles at the back of the tank. Re-suspension and dissolved oxygen saturation, was further maintained with an air stone situated at the rear of each tank. Fresh seawater (filtered to <1 µm) was added at a rate of 4 l h -1 to each tank by irrigation dripper (2 water turnovers per tank per day).
Experimental coal concentrations were maintained by pulsing coal solutions from highly concentrated stocks (120 -1200 mg l -1 ) of suspended coal (in 238 l fibreglass tanks) into each experimental tank (10 pulses of 80 ml stock suspension per h -1 , Fig. S3). The coal stock suspension was maintained using an external pump (Eheim Compact 1260 at 2400 l h -1 : Eheim GmbH, Germany) that suctioned coal at the stock tank base and delivered it via PVC pipe back to the top of the stock tank, thus maintaining coal particles in suspension (Fig. S3).