Fig. 1.
Seafloor depths and surface slicks along the west coast of Hawai‘i Island, the southeastern most island in the Hawaiian Archipelago. (A) Seafloor depths. (B) Remotely sensed observations for September 23, 2018 revealed that surface slicks and ambient waters occupied 8.8% (90 km2/1,025 km2) and 91.2% (935 km2/1,025 km2) of all nearshore (≤6.5 km) ocean surface area, respectively. (C) Distance to nearest slick shown in B with 54.0% (505 km2/935 km2) of all nearshore ambient waters within 500 m of a surface slick. The spatial extent of remote sensing detection is the colored region shown in B and C. For additional survey time points, the area of surface slicks and ambient waters as a percentage of the study area and the percent area of ambient waters that are within 500 m of a surface slick are as follows: August 31, 2018, 8.8% (88 km2/998 km2), 91.2% (910 km2/998 km2), and 49.2% (448 km2/910 km2); October 3, 2018, 9.1% (94 km2/1,037 km2), 90.9% (943 km2/1,037 km2), and 47.3% (446 km2/943 km2); and October 11, 2018, 6.5% (67 km2/1037 km2), 93.5% (970 km2/1037 km2), and 47.0% (456 km2/970 km2) (SI Appendix, Fig. S1).