[Coral-List] [EXTERNAL] Re: effect of sunscreen on corals

Bargar, Timothy tbargar at usgs.gov
Thu Feb 7 19:55:58 UTC 2019

I was asked several years ago to help biologists at the USVI National Park
understand whether or not they should be concerned about sunscreen
chemicals.  There were some articles showing adverse effects in aquatic
organisms that had been exposed to the active ingredients in sunscreen
lotions, so their concern was understandable.  But like I said before, the
dose makes the poison.  If you elevate exposure enough, you could see an

I suggested to them that coastal waters at some of their high and low use
beaches be sampled to determine what active ingredient concentrations were
present.  My thought process was 2-fold.  First, the ocean is terrific at
dilution because of the tremendous water volume available.  There is a
cliche in aquatic toxicology, "dilution is the solution to pollution".  I
was not expecting to see very high concentrations, but we don't know that
without investigating.  Second, if we sampled at some of the high-use
beaches and still didn't see much, then the likelihood of effect (i.e.
risk) would be very low there, and certainly so where visitation was low or
essentially non-existent.  So we went out and collected samples, largely
within 5-10 m of the surf zone.  Most of the samples had concentrations
well below 1 ug/L, but to my surprise, we found oxybenzone concentrations
up to 6 ug/L, which at the time was near the highest I'd seen in the
literature.  Since a few effect concentrations in the literature were less
than 6 ug/L, there was greater risk than I expected.  Since the samples
were collected so close to the surf zone and I expected concentrations
would decline with distance from that zone, we went back out and conducted
sampling designed to test that hypothesis at 2 of the higher-use beaches.
As expected, they did decline with distance from the beach.  Data from
these sampling efforts can be found in Bargar et al (2015), Marine
Pollution Bulletin v101, pp 193-199.  All of those samples were collected
around mid-day when I expect the most swimmers to be present, again under
the presumption that if we found little in the water, then risk was likely
to be minimal.  A few papers have shown diurnal variation of concentrations
(Sankoda et al. 2015, Arch Environ Contam Toxicol v68, pp 217-224,
Tovar-Sanchez et al. 2013, PLOS One v8 issue 8, e65451), presumably in
response to the number of swimmers at the beaches.  I expect the same at
the USVI National Park, but haven't been able to investigate.

The actual concentration to which aquatic organisms are exposed is tough to
determine precisely.  It clearly will vary diurnally making the actual
exposure an average over a span of time that an investigator chooses to
select.  A single discreet sample, while representing an organism's
exposure at that instant, is not representative of its entire exposure.
The organism will integrate exposure over time and location (for mobile
organisms).  We have conducted an experiment in which we tried to mimic, in
a flow-through system, what we'd expect to be the diurnally varying
concentrations at the high-use beaches.  We exposed mosquito-fish (I know,
not a marine organism much less a coral) to this system for 8 weeks,
beginning when the fish were 1-2 days old and then looked at gene
regulation in select tissues.  We also evaluated growth and survival - no
effect there.  We're still evaluating the molecular data.  I'd like to do
the same with coral, but haven't succeeded in securing funding.

I guess my point in saying all of this is that there is a lot of
uncertainty regarding the risk to reefs from the active ingredients in
sunscreens.  The literature base for it is nowhere near that for much of
the other reef-related research.  There is little doubt that the actives
can adversely affect aquatic organisms given adequate exposure.  There is
also little doubt that the spatial extent of potential exposure to the
actives world wide is nowhere near that of the spatial extent of exposure
to elevated temperatures.  Even if concentrations in the water were
sufficient to have an effect, there are only so many beaches or areas where
swimmers are in the water. The sun, however, is just about everywhere.  So
the potential spatial extent of effects is greater for warming than the
sunscreen actives.  However, if a particular chemical is shown to be a
significant risk, resource managers at the local level want and need to do
something about it (I have been told as much by those at the national
park).  Doing so can only alleviate some of the stress.  I think there is
"room" to manage and research both.

On Thu, Feb 7, 2019 at 10:51 AM Douglas Fenner via Coral-List <
coral-list at coral.aoml.noaa.gov> wrote:

> I was just made aware of a new paper on some sunscreen UV filter
> ingredients, though oxybenzone was not tested.
> Fel, J-P, et al 2018.  Photochemical response of the scleractinian
> coral *Stylophora
> pistillata* to some sunscreen ingredients.  Coral Reefs 38: 109-122.
> https://link.springer.com/article/10.1007/s00338-018-01759-4
> (become a member of the International Coral Reef Society, and ALL the
> articles in Coral Reefs become open-access for you, and you can join
> amazingly inexpensively!)
> One person pointed out to me that when there is strong evidence that there
> is an effective chemical that is less toxic, then more toxic chemicals can
> be banned.  Says that happens all the time in the insecticide industry.  I
> hope there are effective UV filters that are less toxic and useful for
> sunscreens.
> Another points out that the "conservationists" in the dive industry jump
> all over easy things like sunscreens, eager to urge people to take action,
> but won't touch global warming with a 10 foot pole (my wording).  That's
> treating the scratch while the patient dies of a gunshot wound to the
> chest, great way to watch the reefs die under our noses, in my opinion.
> If there was direct evidence of coral mortality in the ocean caused by a
> sunscreen ingredient, the case for banning it would be stronger.  But where
> is the evidence of that???  Bleaching has killed billions of colonies all
> over the world, massive coral mortality, obvious to anyone.  But where's
> the evidence that sunscreens have caused mass mortality?  As someone
> pointed out to me, for virtually every chemical, there is a concentration
> at which it becomes toxic.  The real question is, are sunscreen chemicals
> toxic to corals at the concentrations at which they occur in the ocean
> where corals are?  And it has to be in the water able to affect the coral,
> if you put a dispersant in, then chemicals that don't readily dissolve in
> the water (and surely the manufacturers don't want it to wash off or
> dissolve off of people readily) may then have much higher concentrations
> dissolved in the water than would dissolve naturally in the ocean, no
> surprise if they are toxic, but that wouldn't be the situation where living
> corals are in the ocean.  Does oil dissolve in water?  The amount of oil
> floating on the surface isn't what kills corals on the bottom, it is the
> small fraction that manages to dissolve in the water that affects the coral
> on the bottom (unless the coral is so shallow that the oil or tar balls
> cover the coral directly).  Even sunscreen floating on the surface, if it
> doesn't dissolve in the water, will have little effect on life in the
> surface microlayer, I would think.  A small part dissolves, and the
> question is, is that enough to damage corals.  The small part of sunscreen
> chemicals floating at the surface which dissolves may not stay in the
> surface microlayer but diffuse and be carried by water movement into the
> bulk water column, and thus might not be nearly as concentrated at the
> surface as the non-dissolving portion.  I haven't tested it, I'm not a
> chemist, I defer to those with expertise in this area, please enlighten us.
>      There is a sentence in the abstract (which is open access at the URL I
> posted above) that says: "It first shows that for many organic filters,
> measured concentrations were significantly lower than nominal
> concentrations, due to the lipophilic nature of the compounds."  Which
> sounds to me like they are saying that the concentration dissolved in the
> water was less than calculated based on how much they put into the water,
> because it doesn't dissolve readily in water.
>      Zinc oxide was found to be toxic to the corals.  Also, another
> sentence in the abstract says: "The other UV filters tested showed no
> adverse effect on coral symbionts or animal tissue up to the concentration
> corresponding to their water solubility limit (and even above)."  I
> interpret this to mean that you can dissolve all you can of them in the
> water and they don't show an adverse effect on photosynthesis (which is
> what was measured).  Note that they didn't test oxybenzone, they tested
> other UV filters used in some sunscreens.
> Cheers,  Doug
> On Tue, Feb 5, 2019 at 9:43 PM Bill Allison <allison.billiam at gmail.com>
> wrote:
> > I was thinking of sunscreens as one of many insults afflicting the
> > microlayer ecosystem, and how important that ecosystem is.
> >
> > On Tue, Feb 5, 2019 at 10:38 PM Douglas Fenner <
> > douglasfennertassi at gmail.com> wrote:
> >
> >> Good point!  Many or most coral eggs float so they would be in the
> >> surface microlayer, slicks of coral eggs on the surface on the Great
> >> Barrier Reef are large enough you can follow them for a while from
> >> airplanes.  I would guess that sunscreens float, but I don't know.  But
> >> most areas small enough to be contaminated significantly by sunscreens
> are
> >> not very likely to be self-seeding, especially for the majority of
> corals
> >> that are broadcast spawners.  Still would be an impact on overall coral
> >> reproduction, though given that the areas that have large numbers of
> >> tourists with sunscreen in the water are minute compared to the world
> reef
> >> area, especially in the Indo-Pacific, which of course is most of the
> >> world's reefs, the effect would be pretty small, probably difficult to
> >> measure I would guess.  Maybe higher in an area like the Caribbean where
> >> tourism is large on many islands.
> >> Cheers,  Doug
> >>
> >> On Tue, Feb 5, 2019 at 2:05 PM Bill Allison <allison.billiam at gmail.com>
> >> wrote:
> >>
> >>> It strikes me that sunscreens will tend to float as will toxins seeping
> >>> into the sea from freshwater lenses and fogging pesticides in diesel
> >>> carriers, all of which will be harmful to organisms in the surface
> >>> microlayer.
> >>> Wurl, O. and J. P. Obbard (2004). "A review of pollutants in the
> >>> sea-surface microlayer (SML): a unique habitat for marine organisms."
> >>> Marine Pollution Bulletin 48(11-12): 1016-1030.
> >>> Abstract
> >>> Boundary layers between different environmental compartments represent
> >>> critical interfaces for biological, chemical and physical processes.
> The
> >>> sea-surface microlayer (uppermost 1-1000 lm layer) forms the boundary
> layer
> >>> interface between the atmosphere and ocean. Environmental processes are
> >>> controlled by the SML, and it is known to play a key role in the global
> >>> distribution of anthropogenic pollutants. Due to its unique chemical
> >>> composition, the upper organic film of the SML represents both a sink
> and a
> >>> source for a range of pollutants including chlorinated hydrocarbons,
> >>> organotin compounds, petroleum hydrocarbons, polycyclic aromatic
> >>> hydrocarbons (PAH) and heavy metals. These pollutants can be enriched
> in
> >>> the SML by up to 500 times relative to concentrations occurring in the
> >>> underlying bulk water column. The SML is also a unique ecosystem,
> serving
> >>> as an important habitat for fish eggs and larvae. Concentration ranges
> and
> >>> enrichment factors of pollutants in the SML in different areas of the
> >>> world's oceans have been critically reviewed, together with available
> >>> toxicity data for marine biota found within the SML. Overall, the SML
> is
> >>> highly contaminated in many urban and industrialized areas of the
> world,
> >>> resulting in severe ecotoxicological impacts. Such impacts may lead to
> >>> drastic effects on the marine food web and to fishery recruitment in
> >>> coastal waters. Studies of the toxicity of fish eggs and larvae
> exposed to
> >>> the SML contaminants have shown that the SML in polluted areas leads to
> >>> significantly higher rates of mortality and abnormality of fish
> embryos and
> >>> larvae.
> >>>
> >>
> --
> Douglas Fenner
> Ocean Associates, Inc. Contractor
> NOAA Fisheries Service
> Pacific Islands Regional Office
> Honolulu
> and:
> Consultant
> PO Box 7390
> Pago Pago, American Samoa 96799  USA
> How to win public support for a global carbon tax
> https://www.nature.com/articles/d41586-019-00124-x
> Global warming will happen faster than we think.
> https://www.nature.com/articles/d41586-018-07586-5
> Nations falling short of emissions cuts set by Paris climate pact, analysis
> finds
> http://www.sciencemag.org/news/2018/11/nations-falling-short-emissions-cuts-set-paris-climate-pact-analysis-finds?utm_campaign=news_daily_2018-11-28&et_rid=17045989&et_cid=2515903
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Tim Bargar, Ph.D.
Research Ecotoxicologist
The USGS Wetland and Aquatic Research Center
7920 NW 71st Street
Gainesville, Florida 32653
T - (352) 264-3520
F - (352) 378-4956

"Do not withhold good from those who deserve it when it's in your power to
help them."

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