It’s pretty common knowledge nowadays that the ocean acts as a natural sink for much of the world’s pollution, with many sombre images littering our news feeds of plastic ‘islands’ and marine animals distressed and entangled.
But what if one of the biggest threats marine environments face is silent, invisible to the naked eye and fairly lightly documented in Australia?
Don’t get me wrong - plastics are grim, and scientists predict that by 2050, there’ll be more plastic by weight in our oceans than fish (yikes…).
In recent years we have seen huge positive changes in production and consumerism, widespread efforts from communities and much coverage in science and media. While these efforts must continue to keep tackling the plastic problem, it’s only one piece of the tricky pollution puzzle.
Another particularly sinister piece, and one that I’d like to tell you about today, are trace metals. Trace metals can be naturally occurring - even essential - in our marine environments, for example, copper is essential for nitrification, while zinc and cadmium are essential for CO2 acquisition.
It is when trace metals are introduced into the environment that things get hazy; with the potential to either exceed safe thresholds of existing elements or bring completely foreign elements to the table such as lead.
Historically, mining and smelting operations have released metals like lead, copper, zinc and mercury into the waterways here in New South Wales, Australia, but there are many current anthropogenic sources of marine trace metal accumulation such as agricultural run-off (cadmium, cobalt, copper, zinc, molybdenum), marinas and ship maintenance (copper, zinc), industrial pollution (lead, chromium, cobalt, nickel, cadmium) and coastal urban development run-off (silver, lead, copper, selenium, zinc, chromium).
The kicker for trace metals is that once in the marine environment, they don’t degrade, and just distribute into various compartments which means accumulation – and sometimes biomagnification – in marine life.
This is where things get a bit scary…
Once ingested, inhaled or dermally absorbed, trace metals can affect an animal’s pathology causing sickness, neurological disorders and organ failure. Even scarier, trace metal toxicity can hinder biological processes, affecting growth rate, reproduction, fecundity and ultimately population diversity and viability.
Given the bioaccumulation and biomagnification of metals, this is particularly concerning for apex predators such as whales and dolphins, and there have been several strandings globally that have been linked to trace metal toxicity, with post-mortem results returning alarming levels of deadly metals like lead and mercury.
These toxicology results paired with inflammation and pathology in organs like the liver and kidneys (where metals are known to accumulate) provide pretty solid evidence that the trace metal toxicity is likely to have ultimately caused the animal’s demise.
So, it’s pretty clear: the gradual, large-scale effects of trace metal toxicity are ominous indeed, threatening the health and future of entire populations of marine taxa. However, the slow burn and cloak of invisibility over this threat means it’s rarely front and centre in the media, and despite gaining recent traction in marine science in Australia, there still appears to be a sizeable gap in studies and data.
Two of the biggest factors in this are samples and – drumroll please – FUNDING.
As you can imagine, it’s pretty difficult to access liver and kidney samples from a live specimen or even a dead one that is endangered rarely sighted and/or 500km out to sea.
Post-mortem sampling of stranded animals like cetaceans is the most extensive way to get an insight into trace metal toxicity in their populations, but this is limited to the species and number of individuals stranded/sampled. Live sampling is achievable with blubber and skin biopsies, however lacks the information vital organs can tell us and is only appropriate for regularly surfacing, predictable populations like our East Coast humpbacks.
I was lucky enough to carry out a trace metal study on stranded cetacean samples last year, including samples from the elusive beaked whale family. High levels of cadmium and clear differences in calf and adult accumulation of metals were the highlights of this study, however, it only scratched the surface of what may be lurking in our marine mammal populations and I’m endeavouring to dig deeper and deeper.
I currently sit in the planning stages of my Honours study once again in marine mammal toxicology, however that big, forementioned ‘F’ word is harder and harder to come by in Covid times, and one thing I’ve learnt is that trace metal testing on cetaceans is limited because it’s so expensive (go figure!).
If you’re still with me here and wondering what you can do to help besides funding (seriously…), firstly, thank you! And secondly, there are many things you can do in your everyday life to help fight the pollutions battle.
A big carrier of contaminants like trace metals into the ocean is plastic, funnily enough, so why not kill two birds with one stone and reduce your plastic use to avoid it ending up in the ocean.
Appropriate waste disposal including the use of household chemicals and solvents is also a great help, and carrying this diligence with you to your workplace, families, friends’ houses and outdoor activities earns you extra bonus points too.
While you can’t physically pick up trace metals that are in the marine environment (cue: the image of giant novelty magnet), there are a number of scientists working on filtering and extraction devices to help ‘detoxify’ areas of the ocean, so hope remains for areas that may already be heavily affected.
Research is imperative right now for trace metals, and the more we can find out about what species are affected, how they are affected, and where they are affected, the sooner we can manage the situation and hopefully stop further damage to populations of marine life.
You know the drill folks: reduce, reuse, recycle – and rally behind your friendly neighbourhood scientists doing the dirty work to help protect what they love!
Written by Natalie Palmer
Veterinary nurse, graduate Marine and Environmental scientist
Palmer, N. 07/02 (2021). Trace element concentrations in various tissues of stranded cetaceans along the New South Wales coast. Unpublished Third Year Undergraduate Report. School of Environment, Science and Engineering, Southern Cross University, Lismore.
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