Setting up the trace metal rosette for deployment. Photo: Sarah Seabrook

Tangaroa voyage: Land-sea connectivity in the Ross Sea coastal environment

26 April 2023

Hidden deep beneath the Antarctic ice lies complex, poorly understood, networks of ancient water and gas. Are these networks connected to the ocean and, in particular, the Ross Sea region Marine Protected Area?

Dr Sarah Seabrook (NIWA), an early career researcher, received an ASP Opportunity Fund award to explore these connections between land and sea in the Ross Sea coastal environment. On the 2023 Tangaroa voyage, she pursued this research in the coastal region of northern Victoria Land. She was searching for seafloor seeps of subglacial fluids into the ocean.

The scarcity of identified fluid seeps in Antarctica has prevented determination of how these fluid systems impact coastal margins; however, the implications may be profound. For example, these subglacial fluids contain iron and other trace metals (which may create productivity hotspots) and greenhouse gases (which may impact the climate system).

With so little known about these systems, Sarah’s team used a diverse sampling plan while at sea, to begin quantifying:

  1. the composition of these fluids,
  2. the impacts that the fluid seeps have on the marine environment, and
  3. and the temporal and spatial variation in fluxes.

While along the coast, shipboard acoustics sent down sound pings, which reflected off gas bubbles or fluids seeping from the seafloor, making a plume in the data that the team could target for sampling and visualisation. Once a location was identified, ecosystem change on the seafloor in response to these seeps was visualised with a digital towed instrument system (DTIS), which took video and photo observations along the seafloor. When appropriate, samples were taken from discrete locations on the seafloor to allow follow up description of unique species, and geochemical characterisation of the sediments.

Fig 1 plume

Seafloor images from areas of marine seeps, showing transition from background seafloor to periphery of seep site, and centre of seep plume. The white bar indicates 10cm. Photo: Sarah Seabrook.

To quantify the composition of the fluids and gases released from these seeps, to understand how these features were changing water column properties, two types of sampling occurred. First, a conductivity, temperature, and depth (CTD) rosette was used to profile the water column, and to sample at specified depths for gases, nutrients, and microbial life. Secondly, specialised trace metal sampling occurred with a trace metal clean rosette and, at times, hand-deployed niskin bottles.

From this work, the team made many exciting discoveries throughout the voyage that they are working to better understand now back in the lab.

“I was absolutely astounded by the level of ecosystem change that we were observing in the marine environment in response to these fluids seeps. We know so little about them, but they seem so important and I’ve come away really motivated to help figure out the mystery.” – Sarah Seabrook

The Tangaroa voyage supports ASP research into the biological and physical aspects of Ross Sea ecology that provides fundamental information essential to understanding threats from the changing environment. Field work of this kind is critical to development and validation of the projection models that the ASP is developing to better understand climate-related threats to the Ross Sea MPA and further afield.