Potential impacts of bushfires on our Marine
Environment

For specific enquiries or
interview requests on bushfire impacts relating to marine ecosystems and
environment please contact media@sims.org.au

Contaminants
and Toxic Effects of Ash to Marine Ecosystems

Dr
Katherine Dafforn, Senior Lecturer in Environmental Science at the Macquarie University
Marine Research Centre, and Deputy Director of SIMS’ Sydney Harbour Research
Program:

“Bushfire ash contains a number of
different constituents including carbon and essential nutrients, but depending
on the location of the fires can also contain high concentrations of
contaminants such as metals. At low levels these can be beneficial to an
ecosystem by stimulating growth, but if levels are too high then there might be
toxic effects.”

“Most research has focused on the
impact of bushfires on land and so we actually don’t know a lot about the
impacts of bushfire ash on waterways. Certainly bushfires remove vegetation
which increases soil mobilisation and so we’d expect more soil runoff into
waterways resulting in murkier waters. This increased sediment load and reduced
light in the water column could have impacts on productivity. Similarly metals
in high concentrations can impact on marine life by causing death through toxicity
or affecting reproduction and growth rates.”

“Some research has also shown that fire
mobilises mercury in runoff and the fluctuating temperatures in fires can cause
methylation – higher concentrations of mercury have been found in fish from
lakes in burned catchments compared to reference catchments.”

Potential
Impacts of Bushfire Smoke and Ash to Sydney and Surrounds

Assoc.
Prof Shauna Murray, core member of the Climate Change Cluster, leader of the Seafood Safety: Marine Algal Biotoxins research program at UTS, and team leader of the Marine Microbial
Biotoxins Facility at
SIMS:

“An ash layer might shade the water column,
and lead to an inability of phytoplankton to access sunlight. This might lead
to die offs of phytoplankton, which in turn might lead to a low level of oxygen
in the water. A low level of oxygen can lead to the deaths of marine life, ie
fish, as they basically suffocate.”

“The addition of ash might be lead to a
large nutrient input to the water column. This could lead to greatly increased
growth of certain ‘weed’ microalgal species. This is called a “harmful algal
bloom” (HAB), and they are increasingly common around the world. Some HABs are
directly caused by nutrient inputs, ie fertilisers. An addition of ash might
have this same effect.”

Drought
and Fire Impacts in Estuaries

Associate
Professor William Glamore, Water Research Laboratory, School of Civil and Environmental
Engineering, UNSW Sydney. Member of SIMS
Scientific Advisory Committee.

“The bushfires are a symptom of the
prolonged drought impacting our coastal communities. In addition to the fire impacts, the drought
has also generated a number of additional effects. While the issues of turbidity, ash and water
scarcity have been well covered, the coastal drought has helped generate an
unprecedented volume of acidic groundwater.

Initially created by the drainage of
coastal floodplains, via Commonwealth supported programs in the 1960-70s, these
acidic sediments are prevalent throughout coastal NSW. If left unmanaged, the large volume of acidic
groundwater will leach into coastal ecosystems across our marine estate. Once released, the acidic groundwater, with
high concentrations of heavy metals, becomes a toxic plume that is transported
with the tide throughout an estuary. Previous large events have followed floodplain rainfall and resulted in
major fish kills over entire estuaries, such as the Richmond River in 2001 and
2008. Other impacted systems include the
Tweed, Clarence, Macleay, Manning, Hastings, Hunter, Shoalhaven and indeed
every large coastal floodplain in NSW.

Due to the prolonged drought and the
likelihood of future rains, it is anticipated that a major acid event is
imminent. The acidic plumes are
typically associated with ‘black water’, (i.e. very low dissolved oxygen
levels), which can lead to marine animals dying from asphyxiation. This is likely to be exacerbated by large
volumes of ash that will consume oxygen in the water. In combination, the toxic metals, acidic
water, ash load, drought stressed ecosystem and high turbidity present
significant risks to our marine/estuarine estate.

Urgent action is required to restore high
priority acidic sites to reduce acid generation, limit acid discharges and
recreate intertidal ecosystems that sequester carbon.”

Unprecedented
Fires require Crucial Research for Future Monitoring of Coastal Environments

Combined statement from
SIMS’ Postdoctoral Group, including Dr Paloma Matis, Dr Maria
Vozzo, Dr Fabrice Jaine, Dr Michael Doane, Dr Hayden Schilling & Dr Nina
Schaefer.

“The impacts of these fires will likely be
far reaching and influence all levels of the coastal marine ecosystem. Erosion
and subsequent run-off of burned land-based material will result in massive
inputs of carbon and other nutrients into the marine environment. This will
likely ramp up productivity, including microalgal and cyanobacterial blooms. In
the event of blooms, oxygen levels will be reduced and this will affect all
levels of life, ranging from bacteria through to fish communities. In addition,
large amounts of run-off will likely carry heavy metals, which are naturally
occurring in the sediments, but can become toxic when shuttled into the food
web through mobilization by microbial organisms (i.e. bacterial metabolism).
High inputs of ash into the surrounding environment could shade some areas of
the coastal region (some beaches already have ‘black’ waves due to enormous
amount of ash in the water), reducing sunlight into the water column.

Should this reduced light availability be
prolonged this could impact important sub-tidal habitats including seagrass and
kelp beds, which provide refuge and nursery habitats for commercially and
recreationally important species, improve water quality and provide protection
to coastal zones from erosion.

The extent of these fires is unprecedented
and therefore our predictions may in fact underrepresent the extent to which
coastal ecosystems will be affected in NSW. Furthermore, research into the
impacts and continued monitoring of coastal environments is crucial going
forward.”