Title: MESOPHOTIC MACROALGAE ACROSS THE HAWAIIAN ARCHIPELAGO: DECIPHERING THE DIVERSITY AND DISTRIBUTION OF DEEP LIMU

Abstract: Macroalgae are a conspicuous, yet poorly described, component of mesophotic ecosystems in Hawaii, forming habitat for coral reef fish in the Northwestern Hawaiian Islands (NWHI) and vast meadows in the Main Hawaiian Islands (MHI). Over the past 10 years, we have used submersibles, ROVs, and technical diving to survey the distribution and diversity of mesophotic algae at 76 sites across the Hawaiian Archipelago. Expansive macroalgal meadows of native or invasive green algae were found around Oahu (Avrainvillea sp., Udotea sp.) and the Maui Nui Island complex (Halimeda kanaloana) to 90 m, with distinct distribution patterns among specific islands. In contrast, macroalgal beds of Microdictyon were observed at mesophotic depths in the NWHI. Numerous new records and new species of macroalgae were discovered, suggesting the mesophotic flora is distinct from shallow water. Molecular analyses revealed that mesophotic sea lettuces in Hawaiian waters form unique communities composed of four new species within the genera Ulva and Umbraulva. Similar patterns of cryptic diversity are emerging for other dominant algae, such as the brown alga Distromium. Overall, the mesophotic flora appears to be abundant and biogeographically diverse with a combination of temperate, subtropical, and tropical affinities. The current study contributes greatly to our understanding of marine biodiversity and biogeography in the Pacific, and has significant implications regarding the unique nature of mesophotic coral ecosystems in Hawaii.

Authors: Spalding HL, Conklin KY, Tsuda RT, Wagner D, Kosaki R, Smith CM, Sherwood AR

Presentation: Oral

Session: 29

Date: 06/21/16

Time: 14:45

Location: 308 A/B

Back