Effects of coal contamination on tropical marine organisms
Berry, Kathryn Laura Elizabeth (2017) Effects of coal contamination on tropical marine organisms. PhD thesis, James Cook University.
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Abstract
Australia exports more coal by sea than any other nation. A series of new mines and port expansions are currently proposed that will lead to an estimated four-fold increase in coal exports through the Great Barrier Reef (GBR) World Heritage Area over the next decade. Increased shipping presents a greater risk of shipping incidents that can potentially release large quantities of coal into the environment. Despite local and international concern related to the shipment of coal through the GBR, there are currently large knowledge gaps pertaining to the risks associated with coal contamination, particularly in tropical marine environments. The overarching objective of this thesis was to quantify the levels at which coal particles become a threat to the health of tropical marine organisms. I placed specific focus on reef-building corals and seagrass because they provide essential ecosystem services. I also investigated juvenile-reef fish as they represent higher level taxa that inhabit coral reefs and seagrass ecosystems. I used an experimental approach to assess the threats posed by both acute and chronic coal particle contamination that is either currently taking place (i.e. fugitive losses from ports), or that could occur in the future (i.e., ship spill scenarios). Additionally, both the physical and chemical effects of coal contamination were considered.
The maintenance of coral reef populations is dependent on the success of early life history processes, such as fertilisation, and larval recruitment onto the reef. A coal spill may contaminate the ocean surface through to the seabed, potentially posing a threat to the early life history stages of corals that develop in the water column. In Chapter 2 I established threshold values for short-term coal exposures to coal suspensions and leachate dilutions, for coral gametes, embryos and larvae. Moderate concentrations (≥ 50 mg l-1) of suspended coal particles significantly inhibited fertilisation and reduced embryo survivorship, which could lead to lower larval densities. Low levels of coal deposition (12.5 mg cm-2) onto surfaces significantly reduced larval settlement. While a large coal spill is unlikely to occur during a mass spawning event, this chapter highlighted that even low to moderate coal concentrations can impair coral recruitment.
Another potential contamination scenario from a shipping incident involves the chronic release of coal suspensions. The hypothesis that chronic coal contamination will negatively affect key demographic rates (growth and mortality) of a reef-building coral (Acropora tenuis), seagrass (Halodule uninervis) and reef-fish (Acanthochromis polyacanthus) was tested in Chapter 3. The aim was to establish threshold values that elicit lethal and sub-lethal responses. This was investigated by employing a concentration-response experimental design that exposed the organisms to a range of coal concentrations (0 to 275 mg coal l-1) over 14 and 28 d. Low to moderate levels of suspended coal caused extreme light attenuation and coal particles were extremely sticky, adhering to the tissue surfaces of all test organisms. Coral survivorship and seagrass growth rates declined with increasing coal concentrations, and effects were larger after 28 compared with 14 d of exposure. Fish growth rates were similarly depressed in all coal treatment intensities but survivorship was high (98% survivorship). Reduced growth can have serious consequences on reproductive success and survivorship, which could alter population growth in reefs and seagrass meadows subjected to chronic coal contamination.
The mechanisms underlying sub-lethal effects of coal suspensions on the reef fish, Acanthochromis polyacanthus, focusing on aerobic respiration and gill morphology, was investigated in Chapter 4. Acute exposure (5 d) to 38 or 73 mg coal l-1 temporarily reduced fish standard oxygen consumption rates (MO2) by 17 %; however, prolonged exposures resulted in significant elevations in MO2, by 30-47% compared with control fish. After 31 d exposure to suspended coal concentrations (0, 38, 73 and 275 mg coal l-1), coal particles had adhered to fish gills, most notably in the highest coal treatments. In response, the fish exposed to 275 mg coal l-1 shed parts of their filament epithelium, which increased their respiratory surface area, thus enhancing their oxygen uptake efficiency. This chapter emphasizes that low-moderate concentrations of chronic coal exposure can elicit energetically costly stress responses (increased metabolism, gill remodelling) in fish. However, changes in gill structure potentially mitigate negative effects of coal exposure and this may have contributed to the low fish mortality measured in Chapter 3.
In Chapter 5 I investigated the effects of chronic coal deposition and acute coal suspensions on the physiological performance (photosynthesis, respiration and calcification) of three morphologically distinct coral species, and compared these responses with those elicited by carbonate sediments. Corals were exposed to chronic deposition (2 x 30 mg cm-2 exposures per week for 4 weeks) and acute exposure to a high concentration (1250 mg l-1) of suspended particles. Trace metal and polycyclic aromatic hydrocarbon (PAH) leachate was measured from each particle type. Corals were generally less efficient at clearing coal particles from their tissues compared to sediments, and coal exposure lead to greater reductions in physiological performance than sediment. Elevated dissolved concentrations of certain trace metals (Al, Mn, Co, Ni) in coal suspensions may have contributed to the negative impacts of coal. This chapter emphasizes the differences in the response of corals to coal and the need for management agencies to consider contamination by coal particles independently of- and in addition to sediment exposures.
This thesis provides important evidence that tropical marine organisms can be directly and indirectly affected by a range of coal contamination scenarios; including decreased coral fertilisation and settlement, reduced physiological performance and survivorship of adult corals, and decreased seagrass and fish growth rates. The results underscore the importance of adequately assessing the risks posed by increased shipping through ecologically sensitive areas, such as coral reefs and seagrass meadows. The research identified threshold estimates for sub-lethal and lethal effects that can be implemented to improve environmental impact assessments and risk modelling. By addressing critical knowledge gaps that presently impede adequate assessment of the risks posed by coal contamination and spills to coral reef and coastal ecosystems, this thesis contributes to the management of sustainable coal transportation through the Great Barrier Reef Marine Park, and other coastal environments.
| Item ID: | 52993 |
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| Item Type: | Thesis (PhD) |
| Keywords: | coal contamination, coal particles, coal spills, coal, coral reproduction, ecology, environmental impact, fertilisation, Great Barrier Reef, marine contamination, settlement, suspended particles |
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| Additional Information: | Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 2: Berry, Kathryn L.E., Hoogenboom, Mia O., Brinkman, Diane L., Burns, Kathryn A., and Negri, Andrew P. (2016) Effects of coal contamination on early life history processes of a reef-building coral, Acropora tenuis. Marine Pollution Bulletin, 114 (1). pp. 505-514. Chapter 3: Berry, Kathryn L.E., Hoogenboom, Mia O., Flores, Florita, and Negri, Andrew P. (2016) Simulated coal spill causes mortality and growth inhibition in tropical marine organisms. Scientific Reports, 6. pp. 1-8. |
| Date Deposited: | 28 Mar 2018 05:12 |
| FoR Codes: | 06 BIOLOGICAL SCIENCES > 0606 Physiology > 060603 Animal Physiology Systems @ 50% 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050199 Ecological Applications not elsewhere classified @ 50% |
| SEO Codes: | 97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 50% 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 50% |
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