Defining that je ne sais QUOI of seep sites: An overview of the Quantitative Ocean-Column Imaging (QUOI) voyage to offshore New Zealand

Abstract

Detecting and characterizing oceanic seep sites is of considerable interest for the geoscience community due to their influence on global climate, ecological significance, connection to resources of high value, and, in many locations including New Zealand, their cultural importance. Modern acoustic systems provide the means for quantitative analysis of seep systems by collection of backscattered energy by gas bubbles and associated water column phenomena and surrounding seafloor. The July 2018 international, multi-institution Quantitative Ocean-Column Imaging (QUOI) voyage aimed to develop protocols and methodologies for identifying and quantifying seafloor and water-column backscatter data associated with bubble seep sites utilizing a large range of active acoustic systems and direct sampling methods. Here, we will provide an overview of QUOI voyage goals and research activities at several locations offshore of New Zealand, including the Calypso hydrothermal vent field in the Bay of Plenty. Gas bubble and hydrothermal fluid emission were captured in acoustic water column data, video transects, and direct sampling operations. More than 3000 individual seep bases were identified in the Calypso hydrothermal vent field, occupying approximately 9 of 115 km2 of mapped seafloor. Efforts are underway to characterize the bubble size distribution of seep sites and quantify carbon flux to the atmosphere using a combination of broadband acoustic methods and in-situ measurements.