According to this study by authors C. A. Downs, Esti Kramarsky-Winter, Roee Segal, John Fauth, Sean Knutson, Omri Bronstein, Frederic R. Ciner, Rina Jeger, Yona Lichtenfeld, Cheryl M. Woodley, Paul Pennington, Kelli Cadenas, Ariel Kushmaro, Yossi Loya:
Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands
"Benzophenone-3 (BP-3; oxybenzone) is an ingredient in sunscreen lotions and personal-care products that protects against the damaging effects of ultraviolet light. Oxybenzone is an emerging contaminant of concern in marine environments—produced by swimmers and municipal, residential, and boat/ship wastewater discharges. We examined the effects of oxybenzone on the larval form (planula) of the coral Stylophora pistillata, as well as its toxicity in vitro to coral cells from this and six other coral species. Oxybenzone is a photo-toxicant; adverse effects are exacerbated in the light. Whether in darkness or light, oxybenzone transformed planulae from a motile state to a deformed, sessile condition. Planulae exhibited an increasing rate of coral bleaching in response to increasing concentrations of oxybenzone. Oxybenzone is a genotoxicant to corals, exhibiting a positive relationship between DNA-AP lesions and increasing oxybenzone concentrations. Oxybenzone is a skeletal endocrine disruptor; it induced ossification of the planula, encasing the entire planula in its own skeleton. The LC50 of planulae exposed to oxybenzone in the light for an 8- and 24-h exposure was 3.1 mg/L and 139 µg/L, respectively. The LC50s for oxybenzone in darkness for the same time points were 16.8 mg/L and 779 µg/L. Deformity EC20 levels (24 h) of planulae exposed to oxybenzone were 6.5 µg/L in the light and 10 µg/L in darkness. Coral cell LC50s (4 h, in the light) for 7 different coral species ranges from 8 to 340 µg/L, whereas LC20s (4 h, in the light) for the same species ranges from 0.062 to 8 µg/L. Coral reef contamination of oxybenzone in the U.S. Virgin Islands ranged from 75 µg/L to 1.4 mg/L, whereas Hawaiian sites were contaminated between 0.8 and 19.2 µg/L. Oxybenzone poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change."
There is also supplementary publications if you want to pay for it.
Some countries (Bermuda) are now issuing requests of its tourism industry to ask that their clients (tourists) apply lotion about a half-hour before entering reef waters, the thinking is that these chemicals are absorbed into the skin and are less harmful to the reefs.
Another study by authors Bratkovics S, Wirth E, Sapozhnikova Y, Pennington P, Sanger D
Baseline monitoring of organic sunscreen compounds along South Carolina's coastal marine environment.
Organic ultraviolet filters (UV-F) are increasingly being used in personal care products to protect skin and other products from the damaging effects of UV radiation. In this study, marine water was collected monthly for approximately one year from six coastal South Carolina, USA sites and analyzed for the occurrence of seven organic chemicals used as UV filters (avobenzone, dioxybenzone, octocrylene, octinoxate, oxybenzone, padimate-o and sulisobenzone). The results were used to examine the relationship between beach use and the distribution of UV-F compounds along coastal South Carolina, USA. Five of the seven target analytes were detected in seawater along coastal South Carolina during this study. Dioxybenzone and sulisobenzone were not detected. The highest concentrations measured were >3700 ng octocrylene/L and ~2200 ng oxybenzone/L and beach use was greatest at this site; a local beach front park. Patterns in concentrations were assessed based on season and a measure of beach use.
And another, extremely detailed and well-sourced study by authors Lauretta Burke, Katie Reytar, Mark Spalding, Allison Perry:
Reefs at Risk Revisited
Reefs at Risk Revisited brings together data on the world’s coral reefs in a global analysis designed to quantify threats and to map where reefs are at greatest risk of degradation or loss. We incorporated more than 50 data sources into the analysis—including data on bathymetry (ocean depth), land cover, population distribution and growth rate, observations of coral bleaching, and location of human infrastructure. These data were consolidated within a geographic information system (GIS), and then used to model several broad categories of threat from human activities, climate change, and ocean acidification. In the absence of complete global information on reef condition, this analysis represents a pragmatic hybrid of monitoring observations and modeled predictions of reef condition.
Here are some other links on the subject:
How Sunscreen May Be Destroying Coral Reefs
A chemical in sunscreen may be contributing to the destruction of the coral reefs as swimmers trying to protect their skin venture near reefs, according to new research.
Researchers behind the study, published in the journal Archives of Environmental Contamination and Toxicology, found that the chemical oxybenzone has toxic effects on young coral that causes endocrine disruption, DNA damage and death of coral, among other the problems. Oxybenzone also exacerbates coral bleaching, a process by which coral reject symbiotic organisms and lose their color. Bleaching has been particularly prevalent in recent years due to rising sea temperatures.
Skincare Chemical Threatens Coral Reefs
A study from a team of international scientists has found that a common chemical in many sunscreen lotions and cosmetics is highly toxic to juvenile corals and other marine life. Oxybenzone, or BP-3, is found in more than 3,500 skin care products worldwide for protection against the sun's harmful effects. The compound has been found entering the environment both through wastewater effluent and directly from swimmers wearing sunscreens.
(with apologies, I think this refers to the same study as the first I mentioned)
Another study by authors Roberto Danovaro, Lucia Bongiorni, Cinzia Corinaldesi, Donato Giovannelli, Elisabetta Damiani, Paola Astolfi, Lucedio Greci, Antonio Pusceddu
Coral bleaching (i.e., the release of coral symbiotic zooxanthellae) has negative impacts on biodiversity and functioning of reef ecosystems and their production of goods and services. This increasing world-wide phenomenon is associated with temperature anomalies, high irradiance, pollution, and bacterial diseases. Recently, it has been demonstrated that personal care products, including sunscreens, have an impact on aquatic organisms similar to that of other contaminants.
So, yeah - lots of studies. And yes, a product killing much of the delicate eco-systems is allowed to be sold.