A Quantitative small-boat platform for sampling ocean surface slicks

A newly designed surface sampler frame with a 1-square-meter mouth area was constructed for quantitative sampling of ocean surface features, with a focus on surface slicks. Design criteria included: 1) sizing for deployment from small boat platforms, 2) the ability to be towed at an oblique angle to ensure that prop wash did not affect the sample, and 3) adjustable net attachments to target different size classes (e.g., plankton versus small fish), along with a mechanical flowmeter to quantify the volume of water sampled. Towing angles were easily controlled by adjusting bridle lengths to ensure prop wash did not influence sample collection. Surface slick sampling was conducted along 500-meter transect locations in nearshore waters of the Kona coast region of Hawaii, demonstrating the ability to follow the sinuosity of slicks in calm sea conditions and at slow towing speeds (less than 3.5 knots). Larvae of Exocoetidae (Paraexocoetus) and Kyphosidae (Kyphosus) were numerically dominant in the samples collected. Significant amounts of microplastics were also collected during testing and sampling operations. The authors concluded that the surface sample frame was effective in acquiring samples from the narrow, meandering slick bands and was found appropriate for studying these and other ocean surface features. This surface sampling platform assembly is named Lele Wa'a (Hawaiian for whale shark, Rhincodon typus).