This page provides highlights of fieldwork conducted in the North Pacific Ocean that I have participated in and occasionally been the chief scientist. A continuing theme through many of these expeditions is the temporal variability associated with microbial-mediated biogeochemical cycling over timescales extending from hours to days, days to weeks, and seasons to years. The stable conditions of the oligotrophic ecosystem allow the subtle yet important changes in biogeochemical and ecological dynamics to be resolved more readily than highly variable environments. Selected publications resulting from these expeditions are mentioned and full citations for the references can be found on the Publications page.
This video was produced at the end of our 2018 expedition onboard the R/V Falkor by Thom Hoffman. It summarizes the oceanographic technology used during the expedition and describes the scientific research conducted on marine microorganisms and biogeochemical cycling in the open ocean habitat.
It is a beautiful reminder of why we go to sea.
July 2018 The large 2018 volcanic eruption on the Big Island was proceeded by 2 months of lava entering the North Pacific Ocean. An expedition was conducted to examine the effects of the lava entry on phytoplankton abundance and water-column biogeochemistry in the oligotrophic ecosystem. Our sampling took us within 0.5 miles of the lava entry point where seawater was collected for a wide range of chemical and biological analyses.
March-April 2018 This SCOPE field expedition deployed novel Long Range Autonomous Underwater Vehicles (LRAUVs) in conjunction with WaveGliders, SeaGliders, and a suite of profiling equipment and static sensors to determine the effect of mesoscale eddies on upper ocean hydrography, biogeochemistry, and microbial processes. The one month expedition on the R/V Falkor was divided into two legs to accommodate an engineering test phase followed by a comprehensive scientific expedition.
March 2016 The second major CMORE/SCOPE field campaign used SVP drifters to track the circulation of an anticyclonic eddy located immediately to the north of the Hawaii Islands. Seagliders were used to survey across the eddy field and shipboard measurements of water-column biogeochemistry, productivity and export were conducted. This expedition heavily featured in situ incubations for many important rate processes (grazing, productivity, nitrogen fixation) whereby the incubation bottles are suspended on free-drifting arrays.
July-August 2015 The CMORE/SCOPE field campaign focused on diel studies of microbial metabolism using Lagrangian-based observations facilitated with the deployment of SVP drifters close to the center of an anticyclonic modewater eddy. Due to the number of scientists involved, the fieldwork was conducted using two University of Hawaii research vessels simultaneously. Diel cycles of microbial metabolism were analyzed over a ten day period, with a break in the middle to provide contextual biogeochemical measurements.
March 2014 Building off the day-to-day variability investigations in the summer of 2012, this CMORE cruise increased the frequency of sampling to every 4 h (referred to as ‘diel sampling’) to inform on day-night changes in microbial metabolism (Ferron et al. 2015), particulate material, and particle size. The diel sampling was influenced by the passage of a storm with 40 knot winds passing through the Station ALOHA region which deepened the mixed layer to depths of 110 m, not quite enough to reach the deep chlorophyll maximum or impact the nutricline.
July-September 2012 A combination of CMORE and HOT cruises provided near-continual sampling at Station ALOHA during July-September 2012. The 2.5 months of high resolution sampiling revealed the day-to-day variability associated with upper water column productivity and biogeochemistry to compliment the HOT programs long-term observations. The summer 2012 was associated with overall low productivity with a period of net heterotrophic conditions and the advection of a low salinity feature through the ALOHA region associated with low phytoplankton biomass (Wilson et al. 2015).
September 2011 The CMORE BioLINCS expedition used in situ sampling devices to explore different aspects of the nitrogen cycle in oligotrophic North Pacific Subtropical Gyre. Equipment deployed during the expedition included sediment trap arrays to measure nitrogen export and transformations (Wilson et al. 2014); Sample Incubation Device for in situ rate measurements of nitrogen fixation (Bombar et al. 2015); and the Environmental Sample Processor for diazotroph diversity and abundances (Robidart et al. 2014).
March 2011 This was the second of two cruises led by Matt Church at the University of Hawaii. During this expedition, a new method at-sea indirect measurements of nitrogen fixation (Wilson et al., 2012). This highly sensitive method was facilitated by a reduced gas analyzer (PP1, Peak Labs) which is 1-2 orders of magnitude more sensitive than the standard GC-FID used to quantify the ethylene produced during the acetylene reduction assay.
May 2010 In 2010, I co-led a research expedition to Station ALOHA which included five teachers participating in the Science Teachers Aboard Research Ships (STARS) program. Taking the teachers to sea to conduct hands-on sampling, processing seawater samples in the lab, and interpret hydrocast data helps to incorporate oceanography into their classrooms. The science research onboard the ship included sampling the mesopelagic for zooplankton and nutrient amendment experiments involving dissolved organic matter additions.
August 2008 This CMORE cruise conducted a transect across two eddy fields while conducting water-column hydrographic and biogeochemical measurements to determine the effect of eddy-eddy activity in the oligotrophic gyre. A suite of on deck incubations were conducted to accompany the water-column observations including nutrient amended microcosms to identify the microbial taxa and metabolic functions associated with methylphosphonate-driven methane production (Martinez et al., 2013).
June 2008 The Ocean Productivity Perturbation EXperiment was a field experiment in the North Pacific Ocean. Commercially available Atmocean Wave Driven Ocean Upwelling Pumps were tested as a potential delivery mechanism of deep nutrient rich water into the photic zone to stimulate phytoplankton productivity. The field operations were filmed by the TV production company Impossible Pictures for a series shown on the Discovery Channel.
1988-present The Hawaii Ocean Time-series (HOT) program conducts near-monthly hydrographic and biogeochemical observations at Station ALOHA. Alongside these long-term time-series observations, trace gas measurements of methane, nitrous oxide, dimethylsulfide, carbon monoxide, and hydrogen have been conducted. Currently, discrete samples are collected on every cruise for methane and nitrous oxide in the upper water-column and analyzed back on land to provide a long-term data record of these important greenhouse gases.