Coral reef attributes associated with microplastic exposure.

Coral reef declines have been documented since the 1980's from a variety of global and local stressors. Management resource tools are needed to preserve these fragile ecosystems from stressors, both known and unknown. Laboratory studies have shown microplastics (MP) to have negative effects on coral physiology, but their effects in a natural environment are not well understood. Thus, our primary objectives were to explore associations between MPs and coral reef attributes. We measured MP concentrations from sub-surface water and coral tissue samples from two Caribbean/Atlantic scleractinian coral species, Montastraea cavernosa and Orbicella faveolata, from St. John, U.S. Virgin Islands and Florida's Coral Reef in 2017 and 2018, respectively. Polymer identification yielded mostly cotton or polyester fibers for both water and coral tissue samples. This study is the first to document MPs in coral tissues from either the U.S. Virgin Islands or Florida's Coral Reef and is the first to explore how MPs relate to coral reef attributes. Significant, positive relationships were seen between MPs in coral tissue and coral density, rugosity, and percent coral cover, indicating MPs may not have immediate adverse effects on coral reef health.