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Waterborne Investigates Environmental Stressors to Coral in the Florida Keys

Posted by Jenn Collins on May 10, 2021


One of the most diverse ecosystems in the world are the coral reefs.  Corals can grow in both shallow and deep waters but corals that build reefs are generally found in shallow subtropical and tropical waters.  Known as the “big cities in the sea”, coral reefs are home to thousands of species.  Since these ecosystems are pertinent to the survival of several thousand species, the decline of corals is a global concern. Recently, Waterborne scientists and engineers, in collaboration with the Consumer Healthcare Products Association, investigated specific stressor impact on the widespread decline of coral in the Florida Reef Tract.

Coral reefs are threatened by multiple stressors, most notably by the global sea temperature change and acidification due to the rise in atmospheric CO2 levels.  Stony Coral Tissue Loss Diseases (SCTLD) are of particular concern for coral health and is important to consider in a multi-stressor assessment. On a local scale, stressors can include invasive species, unsustainable fishing practices, and tourism-related damage.  Recently, a few scientists have hypothesized the potential for certain sunscreen active ingredients to be a significant contributor to the decline in coral health. Conservation efforts are built on investigating such stressor impact hypotheses.

We focused our evaluation on environmental stressors to Florida Reef Tract coral in the Florida Keys through the lens of accepted global and local factors. We considered the following environmental stressors, in order of magnitude: sea surface temperature, SCTLD, land-based pollutants, marine-based influences, and sunscreen active ingredients.

The active ingredients oxybenzone and octinoxate in sunscreens have been effective in UV filtering for 40 years, reducing the amount of melanoma cases by 50% for sunscreen users. This certainly indicates a human health benefit for the use of UV-filter sunscreen products. That said, it is important to consider if continued use of these products impacts the health of coral reef ecosystems. To this end, we incorporated a systematic literature review of coral reef stress factors and coral reef impact assessments, an investigation of monitoring results of sunscreen active ingredients in marine and coastal waters, and a screening evaluation of local anthropogenic factors in Key West in context with proximity to coral and associated bathymetry and ocean currents. These elements were used to assign a relative ranking of factors contributing to degradation of coral in the waters around Key West and develop recommendations for next steps for the protection of reef resources in Florida waters.

Preliminary laboratory studies have been conducted on oxybenzone and octinoxate in an attempt to characterize toxic effects. These studies were short in duration (≤ 7 days) exposing various types of coral (e.g., Acropora pulchra, Stylophora pistillata, Pocillorpa domiconis) to different concentrations of oxybenzoate and/or octinoxate. Further long-term testing is needed in order to assess any chronic effects. These short-term studies also lacked robust testing methods to define measured concentrations of the UV-filters in water and the results have not been reproduced by other researchers.  Based on these preliminary peer-reviewed studies, toxic effects of oxybenzone and octinoxate could not be demonstrated. Therefore, UV filters have not been shown to directly damage Atlantic coral reef populations or decrease their ability to respond to other environmental stressors.

Monitoring of these active ingredients has not been conducted in the Florida Keys; however monitoring efforts from populated beaches such as the Virgin Islands and Waikiki, HI have resulted in UV-filter concentrations either in the parts-per-trillion range or below levels of detection. It is important to consider that even the detections in the parts-per-trillion range from populated beaches are representative of shoreline, publicly-accessible locations. Corals in the Florida Keys are located miles away from the shoreline, indicating that concentrations near corals would be much lower.

Although further research is needed to successfully characterize chemical toxicity effects on coral species, weight-of-evidence assessments have not identified UV-filter active ingredients from sunscreens as a contributor to coral decline. These stressor impact evaluations play a critical role in improving and targeting mitigation and conservation efforts. Although our assessment indicated these active ingredients are likely not significant stressors to coral, we are able to recommend that conservation efforts be focused on known significant stressors including recreational practices in and around the coral reef to reduce the spread of SCTLD and minimize structural damage to the reefs. Read more about this work at https://www.chpa.org/sites/default/files/media/docs/2021-03/Environmental-Stressors-to-Coral-in-the-Florida-Keys-11182020.pdf.