Impact of inorganic UV filters contained in sunscreen products on tropical stony corals (Acropora spp.)

Full text

Short Communication
Impact of inorganic UV filters contained in sunscreen products on tropical
stony corals (Acropora spp.)
Cinzia Corinaldesi
a,
⁎
,1
, Francesca Marcellini
b,1
, Ettore Nepote
c
, Elisabetta Damiani
c
, Roberto Danovaro
c,d
a
Dipartimento di Scienze e Ingegneria della Materia, dell'Ambiente ed Urbanistica, Università Politecnica delle Marche, Via Brecce Bianche, Ancona, Italy
b
Ecoreach Ltd, Corso Stamira 61, 60121 Ancona, Italy
c
Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, Ancona, Italy
d
Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, Italy
HIGHLIGHTS
•Organic UV-filters and preservatives in
sunscreens can harm coral reefs world-
wide.
•Among the inorganic UV filters tested in
the Maldives, ZnO caused bleaching of
Acropora spp.
•Bleaching induced by ZnO was deter-
mined by its impact on symbiotic algae
and was associated with microbial en-
richment.
•Eusolex® T2000 and Optisol™did not
cause evident bleaching, resulting in low
environmental impact to Acropora ssp.
•The use of eco-compatible filters in sun-
screens is highly recommended to pro-
tect coral reef health in the future.
GRAPHICAL ABSTRACT
abstractarticle info
Article history:
Received 19 January 2018
Received in revised form 8 May 2018
Accepted 8 May 2018
Available online xxxx
Editor: Daniel Wunderlin
Most coral reefs worldwide are threatened by natural and anthropogenic impacts. Among them, the release in
seawater of sunscreen products commonly used by tourists to protect their skin against the harmful effects of
UV radiations, can affect tropical corals causing extensive and rapid bleaching. The use of inorganic (mineral) fil-
ters, such as zinc and titanium dioxide (ZnO and TiO
2
) is increasing due to their broad UV protection spectrum
and their limited penetration into the skin. In the present study, we evaluated through laboratory experiments,
the impact on the corals Acroporaspp. of uncoated ZnO nanoparticles and twomodified forms of TiO
2
(Eusolex®-
T2000 and Optisol™), largely utilized in commercial sunscreens together with organicfilters. Our results demon-
strate that uncoated ZnO induces a severe and fastcoral bleaching due to the alteration of the symbiosis between
coral and zooxanthellae. ZnO also directly affects symbiotic dinoflagellates and stimulates microbial enrichment
in the seawater surrounding the corals. Conversely, Eusolex® T2000 and Optisol™caused minimal alterations in
the symbiotic interactions and did not cause bleaching,resulting more eco-compatible than ZnO. Due to the vul-
nerability of coral reefs to anthropogenic impacts and global change, our findings underline the need to accu-
rately evaluate the effect of commercial filters on stony corals to minimize or avoid this additional source of
impact to the life and resilience ability of coral reefs.
© 2018 Elsevier B.V. All rights reserved.
Keywords:
Sunscreens
Coral bleaching
Inorganic filters
Titanium dioxide
Zinc oxide
Science of the Total Environment 637–638 (2018) 1279–1285
⁎Corresponding author.
E-mail address: c.corinaldesi@univpm.it (C. Corinaldesi).
1
Equally contributed to this work
https://doi.org/10.1016/j.scitotenv.2018.05.108
0048-9697/© 2018 Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
Science of the Total Environment
journal homepage: www.elsevier.com/locate/scitotenv

1. Introduction
Coral reefs are among the most diverse and productive ecosystems
on Earth supporting a huge biodiversity (around 830,000 multi-
cellular species, Fisher et al., 2015), and providing ecosystem goods
and services to half a billion people including food provision, financial
incomes and protection against natural hazards (Ferrario et al., 2014;
Hughes et al., 2012;Teh et al., 2013). Approximately, 70% of coral
reefs are currently threatened by several natural and anthropogenic im-
pacts including overfishing, urban-coastal development, pollution and
tourism (Krieger and Chadwick, 2013;Spalding and Brown, 2015,Tsui
et al., 2017). It has been estimated that every year, millions of tourists
travel to tropical destinations (UNWTO, 2015) enhancing the risk of im-
portant consequences on marine life and ecosystems (Danovaro et al.,
2008;Giglio et al., 2015). In the last decades, production and consump-
tion of sunscreens containing active organic (e.g. cinnamates, camphor
derivatives, benzophenones) and/or inorganic (e.g. TiO
2
and ZnO) in-
gredients to protect human skin from UV radiation, have increased in
the cosmetic market on a global scale (Osterwalder et al., 2014;
Sánchez-Quiles and Tovar-Sánchez, 2014).
Despite organic filters dominates the market of sunscreen products,
the combined use of inorganic compounds, such as zinc oxide (ZnO) and
titanium dioxide (TiO
2
), is constantly increasing due to the broad UV
spectrum of protection, and their limited penetration into the skin (Lu
et al., 2015;). However, the potential of these compounds to generate
reactive oxygen species (ROS) and release metal ions into the aquatic
environment has been recently demonstrated, with consequent possi-
ble negative effects on aquatic organisms (Blaise et al., 2008;Haynes
et al., 2017;Hu et al., 2018;Minetto et al., 2017;Wong et al., 2010). At
the same time, investigations on the impact of ZnO and TiO
2
on marine
life, being mostly focused on microalgae, are still too limited to draw
general conclusions (Hazeem et al., 2016;Miller et al., 2010).
Previous studies have also shown that sunscreen products and
their organic ingredients (e.g., organic UV filterssuchasethylhexyl
methoxycinnamate, benzophenone-3, benzophenone-2and preser-
vatives such as butylparaben) can harm tropical reefs worldwide
contributing to coral bleaching (Danovaro et al., 2008;Downs et al.,
2014).
It has also been hypothesised that inorganic filters, such as TiO
2
and
ZnO, depending on their specific physical characteristics (i.e. size, crys-
tal form, morphology of particles), can produce different effects on ma-
rine algae (Peng et al., 2011;Sendra et al., 2017).
It is well known that under UV radiation both ZnOand TiO
2
promote
the formation of reactive oxygen species (ROS) by photocatalytic reac-
tions that lead to important consequences on the health of marine or-
ganisms (Haynes et al., 2017;Ivask et al., 2010;Sánchez-Quiles and
Tovar-Sánchez, 2014). Furthermore, recent studies have confirmed
that ZnO can be toxic to many aquatic organisms (Khosravi-Katuli
et al., 2018;Li et al., 2018;Shin et al., 2018), and dissolved Zn ions
have been implicated as a major mechanism driving the toxicity of
ZnO nanoparticles in aqueous media (Noventa et al., 2017;Wong
et al., 2010).
In the present study, we tested the hypothesis that these filters can
also harm stony corals, possibly through the impact on their symbiotic
microalgae. For this purpose, we evaluated the impact of inorganic UV
filters, largely utilized in commercial sunscreens, on the stony corals of
the genus Acropora of the Maldivian Lhaviyani Atoll (Vavvaru Island).
We conducted field experiments based on the addition of ZnOnanopar-
ticles and of two forms of TiO
2
(Eusolex®T2000 and Optisol™). The
genus Acropora was selected as it is the dominant stony coral in tropical
coral reefs worldwide, and their symbiotic algae (i.e. Symbiodinium sp.)
can be easily recognised, investigated and cultured. The findings ob-
tained here can expand our knowledge on the impact of inorganic UV
filters on coral reefs in order to understand the best tools and practices
for minimising the impacts of tourism and recreational activities and
preserving these corals and their ecosystems.
2. Materials and methods
2.1. Inorganic UV filters
In the present study, we tested the impact of zinc oxide nanoparti-
cles (SIGMA) characterised by uncoated particles of size ranging from
20 to 200 nm (nanoparticles N50% of the total particles), as observed
by Scanning Electronic Microscopy and two forms of titanium dioxide:
Optisol™(Oxonica Ltd. and UK Nanotechnology Company) and
Eusolex®T2000 (Merck KGaA). Eusolex®T2000 is represented by the
crystal form “rutile”with particles size of 20 nm and by the surface
coated with alumina and dimethicone. Optisol™is another modified
form of titanium dioxide in which a small amount of manganese is in-
corporated into the structural lattice conferring free radical scavenging
power, thus minimising the formation of free radicals (Wakefield
et al., 2004). These modifications (surface coatings and metal doping)
have the scope to reduce the potential reactivity of photo-activated
TiO
2
particles by quenching and/or reducing the reactive species gener-
ated before they can interact with the other ingredients in a formula and
with skin components itself (Tiano et al., 2010).
2.2. Sampling area and experimental design
Coral nubbins (3–6 cm) belonging to the genus Acropora spp. were
collected from different donor colonies at ca. 5 m water depth in the
front reef area of Vavvaru Island (Lhaviyani Atoll, Maldives). Nubbins
were immediately placed in experimental mesocosms located at ca.
50 m from the sampling site and supplied with a continuous seawater
flow (i.e. with intake in the sampling area), which allowed us to keep
the same conditions present in situ. Corals were acclimatised in aquar-
ium for 48 h at in situ conditions of temperature and salinity (28 °C
and 35, respectively). After acclimatisation, thehealthycorals (i.e. with-
out any sign of bleaching or necrotic tissue, and showing open polyps)
were washed in virus-free seawater (filtered onto 0.02 μmmembranes
Anotop syringe-filters; Whatman, Springfield Mill, UK), and immersed
in polyethylene Whirl-pack bags (Nasco, Fort Atkinson, WI, USA) filled
with 2 L of virus-free seawater taken to the sampling area. Replicate
sets of coral nubbins (n= 3, containing N300 polyps each) were
exposed to aliquots of different UV filters (final concentration
6.3 mg L
−1
of each inorganic UV filter) and compared with untreated
coral nubbins (used as controls). Corals were incubated in aquaria
maintained at in situ conditions (temperature and salinity), with sea-
water in a continuous flow directly from the ocean. This final concentra-
tion (equivalent to half the maximum concentration of inorganic filters,
permitted in the EU and US, for sunscreen products; i.e. 12%) falls within
the range of values of the same inorganic compounds used in previous
researches (Khosravi-Katuli et al., 2018;Libralato et al., 2013;Mezni
et al., 2018;Sendra et al., 2017;Wang et al., 2016;Yung et al., 2015),
thus allowing us to make proper comparisons.
2.3. Release of zooxanthellae and their health status
Zooxanthellae were analysed from seawater samples collected from
the seawater of the experimental mesocosms in order to quantify
the number ofthe symbiotic organisms released from the coralcolonies.
Ten mL of seawater were collected from treated (added with filters) and
untreated systems immediately after the addition of UV filters (t
0
=
start of the experiment) and after 24 h (t
24
) and 48 h (t
48
) from the be-
ginning of the experiment. Aliquots of seawater samples were filtered
through 2.0-μm polycarbonate filters and mounted on glass slides.
Zooxanthellae were counted under a Zeiss Axioplan epifluorescence mi-
croscope (Carl ZeissInc., Jena, Germany; ×400 and×1000). Based on the
autofluorescence and gross cell structure, we discriminated the
zooxanthellae released from coral colonies as pale (P, pale yellow
colour, vacuolated, partially degraded zooxanthellae) and transparent
(T, lacking pigmentations, empty zooxanthellae) from healthy
1280 C. Corinaldesi et al. / Science of the Total Environment 637–638 (2018) 1279–1285

zooxanthellae (H, brown/bright yellow colour, intact zooxanthellae;
Danovaro et al., 2008;Mise and Hidaka, 2003). The abundance of the
damaged zooxanthellae released was obtained from the sum of the
total number of zooxanthellae classified as pale and transparent, that
were detected in the seawater surrounding coral nubbins exposed to
the different inorganic UV filters.
2.4. Bleaching quantification
According to Siebeck et al. (2006), we performed a colorimetric
analysis of digital photographs of corals taken at the beginning of the
experiments and after 48 h of treatment with UV-filters (specified
above). Photographs were taken under identical illumination with a
Canon EOS 400D digital camera (Canon Inc., Tokyo, Japan) with a scale
meter on the background. The photographs were subsequently
analysed with a photo-editing software for colour composition cyan,
magenta, yellow and black (CMYK). Levels of bleaching were measured
as the difference between the coral's colour at the beginning of the ex-
periments (t
0
) and after 48 h of exposure (t
48
). Thirty random measure-
ments of variables CMYK were carried out across the coral area.
Variations in the percentage of the different colour components
(CMYK) were analysed with one-way analysis of variance (ANOVA).
To rank the bleaching effect due to the different sunscreens tested, we
obtained Bray–Curtis similarity matrix and multidimensional scaling
analysis of the shifts in CMYK colour composition of treated corals
using Primer 5.0 software (Primer-E Ltd., Plymouth, UK). Bleaching
rates were measured as the variation percentage in CMYK colour com-
position between treated and control corals using Primer 5.0 software
(Primer-E Ltd). In addition, to the mean values obtained we attributed
scores of thebleaching degree by means of a mathematical function, ac-
cording to a scaleorganized in ranks (0 to N60), i.e. from “no visible coral
bleaching”(0−10) to “total bleaching”of 100% of coral nubbinssurface
(N60).
2.5. Prokaryotic and viral abundance
Prokaryotic and viral abundance in seawater samples was deter-
mined according to the protocol described by Noble and Fuhrman
(1998). Sub-samples (10 mL) from treated (added with filters) and un-
treated systems were collected immediately after the addition of sun-
screen (t
0
= start of the experiment) and after 24 h (t
24
) and 48 h
(t
48
) from the beginning of the experiment. After collection, three repli-
cate seawater samples were stored at −20 °C until the analysis. Sub-
samples were filtered onto 0.02 μm poresize filter (Whatmann Anodisc;
diameter, 25 mm; Al
2
O
3
) and stained with 100 μLofSYBRGold(stock
solution diluted 1:5000). The filters were incubated in the dark for
20 min, washed three times with 3 mL of prefiltered Milli-Q water
and mounted onto glass slides with 20 μL of 50% phosphate buffer
(6.7 mM phosphate, pH 7.8) and 50% glycerol (containing 0.5% ascorbic
acid). Slides were stored at −20 °C. Prokaryotes and viruses' counts
were obtained by epifluorescence microscopy (Zeiss Axioskop 2). For
each slide, at least 20 microscope fields were observed and at least
200 prokaryotes and viruses were counted per filter.
2.6. Statistical analysis
Differences in the investigated variables betweencontrols and treat-
ments were assessed using permutational analyses of variance
(PERMANOVA; Anderson, 2005;McArdle and Anderson, 2001)on
square root transformed data. The design included two fixed factors
(time and treatment). When significant differences were encountered
(pb0.05) post-hoc pairwise tests were also carried out. Statistical anal-
yses were performed using PRIMER 6 (Clarke and Gorley, 2006).
3. Results and discussion
The inorganic UV filters tested here, ZnO and TiO
2
(especially in the
rutile form) nanoparticles are commonly used in sunscreen products for
their UVA (320–400 nm) and UVB (290–320 nm) coverage and to in-
crease the transparency of cosmetics applied on the skin (Smijs and
Pavel, 2011).
The analyses conducted in this study reveal that ZnO caused the
strongest negative effects in terms of number of zooxanthellae released
from the stony corals investigated (pb0.001, Fig. 1A). In particular, the
release of zooxanthellae after ZnO addition was significantly higher
than in the control and in the corals treated with both TiO
2
forms
(EusolexT2000 and Optisol) with thestrongest effect after 48 h of expo-
sure (i.e., zooxanthellae release up to two orders of magnitude higher
than in the control and other treatments; Fig. 1A; Table S1). In addition,
ZnO determined the release of the highest fraction of damaged zooxan-
thellae (up to one order of magnitude higher than the other treatments
tested), suggesting that these nanoparticles can strongly affect hard
corals impairing their symbiotic microalgae.
Previous eco-toxicological studies documented the negative effects
of ZnO nanoparticles on marine organisms including algae, crustaceans
and fish (Peng et al., 2011;Wong et al., 2010). Here, we expand the ev-
idence on the negative effect of ZnO nanoparticles, revealing their im-
pact also on tropical corals and their symbiosis with microalgae.
The addition of both Eusolex T2000 and Optisol also caused an in-
crease in the release of zooxanthellae in the seawater surrounding
coral nubbins when compared to the control (Fig. 1A; Table S1). How-
ever, whereas Eusolex T2000 showed effects in the short term (t
0
and
t
24,
pb0.01), Optisol acted only after 24–48 h of exposure (pb0.01).
Fig. 1. Impact of the inorganic filters on symbiotic microalgae of Acropora spp. To tal
abundance of zooxanthellae (A) and damaged zooxanthellae (B) relea sed into the
seawater surrounding coral nubbins exposed to 6.3 mgL
−1
of zinc oxide and titanium
dioxide (Eusolex T2000 and Optisol) during th e time-course experiment. Results are
reported as mean values ± S.D.
1281C. Corinaldesi et al. / Science of the Total Environment 637–638 (2018) 1279–1285

PERMANOVA analyses confirmed the significant differences in the re-
sponses of Acropora exposed to the two types of TiO
2
as a result of the
treatment × time interaction (pb0.01).
In the zooxanthellae released from corals, we observed a loss of
photosynthetic pigments already 24 h after exposure to ZnO (Fig. 1B).
The abundance of damaged zooxanthellae, indeed, increased over
time reaching values up to two orders of magnitude higher than in the
controls and in the other treatments (pb0.001). The amount of
damaged zooxanthellae released by corals treated with Eusolex T2000
increased significantly already after 24 h of exposure compared to the
control (pb0.05) whereas the effect of Optisol was more evident after
48 h of exposure (pb0.001).
Previous studies revealed that inorganic TiO
2
nanoparticles are the
major-oxidizing agents in coastal waters, producing very high rates of
H
2
O
2
in seawater and directly affecting the growth of phytoplankton
(Tovar-Sánchez et al., 2013). Our findings indicate that Optisol (TiO
2
modified with manganese) has a non-immediate impact on corals and
symbiontmicroalgae, potentially due to its surface or structural modifi-
cations (manganese doping), which minimises the reactivity of photo-
activated particles rendering them initially inert in water (Botta et al.,
2011). On the contrary, Eusolex T2000 (TiO
2
filter coated with alumina
and dimethicone) has an immediate effect on corals and symbiont
microalgae. The different response time of corals to the two inorganic
filters (immediate for Eusolex and delayed for Optisol) might be associ-
ated with the diverse characteristics of the TiO
2
filters, which once re-
leased in seawater could have a different behaviour and/or action
mechanism (Tsui et al., 2017). Since Optisol determined a “delayed ef-
fect”on the symbiotic interaction between corals and zooxanthellae,
we cannot exclude a long-term effect on the corals due to chronic expo-
sure (Tsui et al., 2017).
The loss of zooxanthellae induced by ZnO resulted in a fast coral
bleaching, which was evident after 24 h of exposure (Fig. 2), and at
the end of the experiment bleaching dominated for 67% of the corals'
surface (Fig. 3; Table S2). Conversely, after addition of the two different
types of TiO
2
no visible bleaching was observed in the corals (Fig. 2),
which, indeed, showed only a slight colour loss in 6–7% of their surface
similarly to the control (3%, Fig. 3;TableS2).
Fig. 3. Bleaching degree in Acropora spp. exposed to the different inorganic UV filters.
Percentage of bleaching in the corals exposed to 6.3 mgL
−
1 of zinc oxide and titanium
dioxide (Eusolex T2000 and Optisol) and scale of bleaching severity.
Fig. 2. Bleaching of Acropora spp. nubbins caused by the inorganic filters. Photographs of
the corals in the control (unexposed corals to inorganic filters; A and B) and exposed to
zinc oxide (C and D), Eu solex T2000 (E and F) and Optisol (G and H) at the sta rt (t
0
)
and at the end (after 48 h) of the experiment.
1282 C. Corinaldesi et al. / Science of the Total Environment 637–638 (2018) 1279–1285

The lower impact of TiO
2
on the corals when compared to ZnO
was evident also in terms of microbial enrichment in the seawater
surrounding the nubbins of Acropora. Previous studies demonstrated
that tropical corals subjected to environmental stress regulate the
abundance of their associated microbes, essential to coral immunity
and health (Krediet et al., 2013), by increasing the amount of bacteria
and viruses released directly in seawater and/or through mucus
(Garren and Azam, 2012;Nguyen-Kim et al., 2015). In addition, previ-
ous investigations reported that sunscreen products and theirUV filters
increase virus proliferation in seawater like in the same way as other
environmental stressors (Danovaro and Corinaldesi, 2003;Danovaro
et al., 2008;Davy et al., 2006). Here, we observed that in systems treated
with ZnO a strong enrichment of both prokaryotes and viruses (42.05 ±
3.88 × 10
8
cells L
−1
and 44.83 ± 0.87 × 10
8
viruses L
−1
;pb0.001,
Fig. 4A and B; Table S3) was observed after 48 h of incubation
compared to the control (14.40 ± 0.32 × 10
8
cells L
−1
and 16.62 ±
1.07 × 10
8
viruses L
−1
). Conversely, the two types of TiO
2
did not
determine any significant increase in microbial abundance over time
(on overage, 5.44 ± 0.18 × 10
8
cell L
−1
and 6.50± 0.23 × 10
8
viruses L
−1
in the treatment with Eusolex T2000 and 6.87 ± 0.11 × 10
8
cell L
−1
and
9.53 ± 0.22 ×10
8
viruses L
−1
in the treatment with Optisol, Fig. 4Aand
B; Table S3). Indeed, TiO
2
particles have been reported to have antimi-
crobial activity due to the generation of free radicals by photoexcitation
or adsorption of the bacterial cells onto TiO
2
particles (Dhanasekar et al.,
2018;Gogniat et al., 2006). However, the specific effect of TiO
2
on pro-
karyotic cells has not yet been defined. Previous studies suggested that
the phototoxicity of nanoTiO
2
on bacteria is not determined by a single
factor but by multiple factors that also include the inorganic material
morphology (Tong et al., 2013).
Concluding, our findings indicate that uncoated ZnO nanoparticles
induce a complete, and potentially irreversible coral bleaching causing
asignificant rapid and widespread mortality of the symbiotic zooxan-
thellae of the stony corals, and stimulating microbial enrichment in
the seawater surrounding the corals. Supposedly, this result may be
due to the alteration of the cellular membrane lipid composition of
hard corals and their symbiotic organisms (Tang et al., 2017). In addi-
tion, previous investigations reported that dissolved Zn
2+
can cause tox-
icity in algae (Franklin et al., 2007;Lee and An, 2013;Shin et al., 2018)
determining manganese deficiency (Miller et al., 2010), mitochondrial
and DNA damage (Sharma et al., 2012), oxidative stress (Xia et al.,
2008;Li et al., 2012) and cell membrane damage (Song et al., 2010).
Other studies highlighted that the cell membrane damage can result
in membrane deformation and morphological changes of cells and
even organelles (Peng et al., 2011;Tang et al., 2017;Trevisan et al.,
2014;Xiong et al., 2011).
Market trends of sunscreen products indicate that ZnO filter utiliza-
tion will overtake nano titanium dioxide (nTiO
2
) in the near future, es-
pecially after the approval of ZnO for cosmetic purposes in the EU since
April 2016 (http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=
CELEX%3A32016R0621). Indeed, ZnO offers high skin protection due
to its greater broad-spectrum UV coverage and reduced opaqueness
thanks to improved formulation technologies (Lademann et al., 2006;
Smijs and Pavel, 2011). The use of ZnO in cosmetic and sunscreen prod-
ucts has been hypothesised to be a safer alternative to conventional
organic-based filters due to several issues related to photoinstability,
skin irritability and endocrine disrupting ability (Biebl et al., 2006;
Hojerová et al., 2011;Krause et al., 2012). However, the results reported
here demonstrate that theuse of ZnO is extremely harmful to the organ-
isms tested, thus suggesting that its use in sunscreen and personal care
products should be further assessed in future investigations because it
might have important consequences on marine environment. Since
the negative impact of ZnO will also be present when it is used in com-
bination with TiO
2
, the concern about these compounds should be also
extended to sunscreen products using a combination of both inorganic
filters. Although the use of coated/modified TiO
2
in sunscreens is not
completely exempt of potential negative effects (Tanvir et al., 2015),
the results of the present study indicate that when used alone (i.e., as
a single ingredient)it can have a limited impact on tropical stony corals.
Accordingly, a similar study conducted on the Montastraea faveolata in
the Caribbean Sea shows that TiO
2
caused significant zooxanthellae ex-
pulsion in all the colonies, without mortality, suggesting a possible coral
acclimation and recovery from stress (Jovanovićand Guzmán, 2014).
However, further investigation is needed to clarify if its use is fully
eco-compatible with marine life while protecting human skin from UV
damage or if it may be harmful if used under specific conditions or in
combination with other products.
Acknowledgments
This study was conducted within the frame of the projects MERCES
(Marine Ecosystem Restoration in Changing European Seas), funded by
the European Union's Horizon 2020 research and innovation program
(grant agreement no. 689518), and national funds ATENEO 2013
obtained by R. Danovaro and ATENEO 2013-2016 obtained by C.
Corinaldesi provided by MIUR (Italian Ministry of University and
Research).
Conflict of interest
The authors declare no competing financial interests.
Fig. 4. Microbial enrichment in the seawatersurrounding coralsinduced by inorganic filters. Prokaryotic (A)and viral (B) abundancesin seawater surrounding coralsexposed to 6.3 mgL
−1
of zinc oxide and titanium dioxide (Eusolex T2000 and Optisol) overtime. Results are reported as mean values ± S.D.
1283C. Corinaldesi et al. / Science of the Total Environment 637–638 (2018) 1279–1285

Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.scitotenv.2018.05.108.
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