NEPTUNE Canada

Monitoring Endeavour–Middle Valley Hydrothermal Systems

Monitoring the Endeavour – Middle Valley Hydrothermal Systems: Integrated heat and mass fluxes and the response of biogeochemical and physical processes to perturbations

Principal investigator(s)

Kathryn Gillis

Co-investigators

David Butterfield, Deborah Kelley, Marv Lilley, Steven Mihaly, Rick Thomson

Discussion & Collaboration

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Abstract

Mid-ocean ridges are dynamic environments where globally significant chemical, biological and heat fluxes occur between the lithosphere and hydrosphere. Investigations of mid-ocean ridge hydrothermal systems are inherently interdisciplinary, reflecting the complex linkages between geological, biological, chemical, and physical processes. Here we propose an observatory experiment at the Endeavour – Middle Valley ridge segment that will monitor spatial and temporal variability associated with seafloor spreading and the variability in biogeochemical and physical processes associated with hydrothermal vent fields and the overlying water column.

The over-arching questions that will be addressed by this experiment are:

• What are the impacts of tectonic and magmatic perturbations on biogeochemical and hydrological processes in ridge crest environments and the overlying water column?
  • What are the timescales of these impacts? Do they differ in sedimented (topographically unconstrained) versus non-sedimented (topographically constrained) terrains? What are the impacts at local and regional scales?
• What are the total fluxes of heat, chemistry, and biomass out of a hydrothermal system?
  • What are the relative contributions to oceanic ecosystems from hydrothermal chemical flux, turbulent buoyancy flux, and topographic interaction dynamics?

Study Sites/Locations

During the first phase of instrument deployment, the greatest density of instrumentation will be focused at the MEF and Mothra field, with more modest instrument deployment at High Rise, Sasquatch, and Middle Valley. The optimal high-temperature experiment at the MEF will be focused at the 360°C smoker called Sully in the Bastille complex, and at the 300°C black smoker Finn in the Faulty Towers complex of the Mothra field.

Diffuse flow systems respond in fundamentally different ways to perturbation events than black smoker chimneys, they host very dense and diverse macro and microfaunal communities, and they are rich in microbes. Life within these systems has a direct impact on fluid chemistry and so fluids and life must be studied as an integrated package. The optimal diffuse flow site experiment will include a fluid sampler/microbial incubator equipped to monitor the temperature, Eh and pH of diffuse fluids and collect diffuse fluid and microbial samples with co-registered chemical and temperature data on both a regular schedule (e.g., bi-monthly) and on-demand (event response), and one-chip and digital cameras trained on the venting and ecological communities. A microbial incubator will be installed into drill holes in basalt located in areas of warm hydrothermal discharge. As with the high temperature sites, the first phase of instrument deployment will be focused at the Main (Easter Island) and Mothra fields, with minimal instrument deployment at the High Rise, Sasquatch and Middle Valley sites.

The temporal variability of integrated heat flux, currents, and turbulence for the main vent fields within the axial valley of Endeavour segment and the impacts that this variability has on ecosystem productivity within the water column will be examined using an array of instruments at five axial valley sites. A set of three cross-axis sites will span the ~1 km-wide valley between the MEF and Mothra. Two additional moorings will encompass the length of the valley between MEF and High Rise, and High Rise and Salty Dawg.

Moored sensors (ADCPs, thermistor arrays, current metres, transmissometers) and sampling devices will be positioned above a high-temperature structure (ranging from the vent orifice to 100 m). The mooring will provide real-time data on the volume, density, velocity, temperature and composition (water plus organic and inorganic particulates) in the lower part of the plume. Time-series or event sampling of the particle load and water in the plume will examine uptake and release of metals in the plume, residence times of particles, reaction rates, and chemical and biological responses to perturbations in the heat and mass flux of the plume. This experiment will complement measurements of high- temperature vents at the plume source and larger-scale heat and mass flux experiments in the neutrally buoyant plume.

Equipment Summary

In addition, the team plans to install a Cabled Observatory Imaging Sonar System (COVIS) either at Grotto or Dante vent sites to image and quantify hydrothermal flow at a vent cluster.

How this project will foster collaboration

There is a long history of collaboration between many of the co-investigators. Canadian researchers (NRCan scientists, DFO scientists, CanRIDGE participants) have collaborated with US colleagues, primarily at the University of Washington (UW), Oregon State University (OSU) and NOAA, to study the geology, biology, physics and chemistry of vent sites along the Juan de Fuca Ridge; scientists from UW and Institute of Ocean Sciences have developed the initial Seabreeze experiment; and Canadian, US, and German researchers have conducted collaborative projects aimed at understanding the genesis of seafloor ore deposits.

Another critical component of future collaborations will be to engage graduate students, post-doctoral fellows, and research associates in the planning and implementation of all aspects of the experiment (see Section 8 for more details). We envision that these students will be co-supervised by researchers from more than one institution, and involved in instrument development, analysis of data collected during the transition period, and/or developing predictive models to test the observations. In this way we will train the next generation of observatory scientists, particularly those from Canada, and facilitate cross-border cooperation amongst their supervisors.

In addition to this considerable intellectual collaboration, there has been significant US and Canadian investment in the development of prototype instruments and experimental design, and site characterization. The Marine Geology and Geophysics at the US National Science Foundation (NSF), Ocean Drilling Program, NSERC, DFO and NRCan have funded numerous investigations at both Middle Valley and Endeavour since the early 1980s. More recently, the W.F. Keck foundation provided $5M over a 5-year period to the University of Washington to set up a proto-Neptune Observatory at Endeavour; extensive leveraging has resulted in nearly a $10M investment since the Keck program began in 2002. In addition, Endeavour is one of three 10-year NSF NSERC, DFO and NRCan have funded numerous investigations at both Middle Valley and Endeavour since the early 1980s. More recently, the W.F. Keck foundation provided $5M over a 5-year period to the University of Washington to set up a proto-Neptune Observatory at Endeavour; extensive leveraging has resulted in nearly a $10M investment since the Keck program began in 2002. In addition, Endeavour is one of three 10-year NSF Ridge Integrated Studies Sites in the world’s oceans. The NSF Ridge program has a budget of $9M/year and they have funded numerous experimental and field efforts to Endeavour since the programs inception. Collectively, these programs have resulted in the Endeavour being amongst the best-studied hydrothermal systems in the world, and the premier mid-ocean ridge observatory. It is the only mid-ocean ridge site to host an in-situ seismic array that is integrated with chemical and biological sensors and sampling instruments. It has also been the focus of a long-term educational outreach effort funded by the NSF known as REVEL (http://www.ocean.washington.edu/outreach/revel/), which has resulted in participation of both Canadian and US junior and high school teachers in seagoing research.

Resources & References

Powerpoint presentations at NEPTUNE Canada workshop, 2/09

• Presentation by Karen Bemis
• Presentation by Kathy Gillis
• Presentation by Rick Thomson