[Coral-List] [EXTERNAL] Re: sunscreens threaten coral

Tue May 10 12:24:41 UTC 2022

Bruce - some of the sunscreen chemicals are relatively water insoluble in freshwater and would be even less so in saltwater. There have been papers reporting chemicals with low water solubility accumulating in the sea-surface microlayer - oil slicks and leaked gasoline would be clearly obvious examples. Other chemicals that aren't visible but also water insoluble will also accumulate at the surface.

We did a cursory investigation with sunscreens in the USVI where we compared concentrations in subsurface water (~1m depth - i.e. arms length) to concentrations in the microlayer in multiple bays around St. John in the USVI (https://doi.org/10.1016/j.marpolbul.2015.10.077). Concentrations were higher in the microlayer when they were detectable, but significantly so for only one chemical (octinoxate) in one bay. There are limitations to the results but there is enough there to indicate further work would be worthwhile.
________________________________
From: Coral-List <coral-list-bounces at coral.aoml.noaa.gov> on behalf of Bruce Carlson via Coral-List <coral-list at coral.aoml.noaa.gov>
Sent: Monday, May 9, 2022 4:48 PM
To: Peter Sale <sale at uwindsor.ca>
Cc: coral-list at coral.aoml.noaa.gov <coral-list at coral.aoml.noaa.gov>
Subject: [EXTERNAL] Re: [Coral-List] sunscreens threaten coral

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I would add one more factor to Peterʻs list, and that relates to the life cycle of “corals”.  I am not fully familiar with the extent of research on sunscreens and toxicity to corals, but if these chemicals tend to float or concentrate on the surface they would be (perhaps) more of a factor to the eggs/larvae.  I assume this has been covered in previous posts so I wonʻt elaborate because everyone on this list will understand the point.

Bruce Carlson

> On May 9, 2022, at 12:51 PM, Peter Sale via Coral-List <coral-list at coral.aoml.noaa.gov> wrote:
>
> Hello listers,
> I've been following the discussion of sunscreens (we've visited this problem multiple times but myths are resistant to being debunked).
>
> One factor that is important when considering the toxicity of a particular chemical, or product containing chemicals, is the concentration at which it has deleterious effects.  Concentration in the open waters of a reef is itself a complicated thing, because with water flowing past the organisms it can be the case that cumulative exposure over time is more important than actual concentration in the water present at the organism's surface at one time.  Still, as a first approximation, if concentrations measured in reef waters are orders of magnitude below those causing harm in aquarium experiments, there is probably no reason to get overly excited.
>
> A second factor which seems not to be getting much attention on coral-list is that while a rose is a rose is a rose, a coral is not a coral is not a coral.  In other words, there are numerous species of corals, some very distantly related to each other, and there are myriad other reef organisms, some very important ecologically, that are also distantly related to each other.  (Coral reefs are arguably the most taxonomically diverse ecosystems on the planet, as Paul Ehrlich pointed out in the 1970s.)  Toxicological experiments cannot test all species, but there is seldom much effort to test organisms beyond a few, often weedy and hardy, species that are conveniently available for lab use.  Even if an experiment showed toxic effects on the species tested, it would be unwise to assume it is toxic for all.  Conversely, if the experiment showed no toxic effect, it would be unwise to assume other more sensitive species might be impacted.  I'm not belittling the importance of toxicological
> experiments.  I am arguing for a more nuanced appreciation.  Frankly, we should abide by the precautionary principle whenever we contemplate putting novel chemical compounds into coral reef waters, but we should also maintain perspective, and recognize that there are some obvious pressures on coral reefs from overfishing to climate change to inappropriate shoreline development that we are not yet dealing with sufficiently.
>
> Peter Sale
> sale at uwindsor.ca<mailto:sale at uwindsor.ca>
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