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Two decades of chemical oceanographic research along the transect suggested a critical role for microbes, and potential key changes in community composition and function associated with the different water masses. As drivers of biogeochemical cycles, changes in microbial communities could have vast repercussions for the marine biome.

The Munida Microbial Observatory Time-Series (MOTS) project was established in 2013 as a specific program embedded within the Munida Transect Time Series.

The aim of MOTS is to provide a comprehensive description of microbial contributions to marine ecosystems in the Southern Ocean by targeting two major water masses, as well as studying the influence of oceanic fronts on microbial diversity and function.

The work carried out within the MOTS project encompasses four major research areas:

Spatiotemporal dynamics in microbial communities

Key people: Kim Currie, Antoine Bagnaro

Microbial communities respond to environmental cues linked to space and time. We aim to establish a long term data collection that allows us to monitor how communities change over space and time, and what the mechanisms associated with these changes are.

Primary objectives:

  • Determine community variance across depth
  • Determine community variance across water masses
  • Determine the effect of frontal zones on communities and processes
  • Seasonal and cyclic (ENSO) events

Top-down vs bottom-up control of marine ecosystems

Key people: Jess Wenley, Andres Gutierrez-Rodriguez

Marine ecosystems are complex and dynamic. Microbes form the base of oceanic food webs as the main source of primary production in global oceans. These microbial populations vary over space and time due to presence of predators such as protists and viruses, or due to different nutrient regimes available to autotrophs that subsequently transfer energy to higher trophic levels. By determining whether microbial populations are controlled by these top down or bottom up processes across the different water masses in the Munida Transect, we can begin to understand how they are contributing to food webs and biogeochemical cycles at a global scale.

Primary objectives:

  • Determining connections across trophic levels. The role of:
    1. Viruses
    2. Protozoa
    3. Protists
  • Establishing the co-occurrence of biochemical and community change

Biogeochemical cycling in pelagic waters

Key people: Blair Thomson, Scott Lockwood

Biogeochemical cycles drive oceanic productivity and regulate our global climate. The factors controlling these cycles are poorly understood, particularly the role of microbial community interactions. We focus on the cycling of carbon and phosphorus, examining variation in extracellular enzymatic activity (EEA) and phycosphere interactions across the Munida transect. Assessments of microbial EEA provides insight into the remineralisation of organic matter, and researching microbial interactions within the phycosphere allows greater comprehension of influences affecting the cycling of nutrients and climatically important molecules such as methane. Ultimately, by modelling these systems, we can better understand the role of microbial community biogeochemical cycling in a changing climate at a global scale.

Primary objectives:

  • Determine the role of oceans as sources/sinks of greenhouse gas emissions through:
    1. S and P recycling
    2. hydrolysis of organic matter
    3. nitrification
  • Determine the extent of EEA and the role these enzymes play in nutrient turnover and acquisition.
  • Determine the sources and flux of carbon within different water masses.

Impacts of climate change

Key people: Fenella Deans, Cliff Law, Miles Lamare

Climate change is already changing our oceans through warming of the surface waters and increased pCO2 lowering the pH in a process called ocean acidification (OA). Climate change will change the most fundamental processes in our ocean such as biogeochemical cycling which is carried out my microbes and enzymes they produce. The long-term monitoring of the Munida transect by the MOTS group can show how climate change is already affecting ocean microbes and the monitoring will continue to show these changes over time. The Munida transect can also provide natural assemblages of microbes from different water masses to be used in manipulative experiments looking at projected ocean temperatures, acidification and other projected ocean changes. The record created by MOTS also serve as a benchmark for observations made during experiments simulating future OA scenarios.

Primary objectives:

  • Experimental manipulations of natural assemblages to determine impacts of future climate change scenarios
  • Benchmarking of observed changes against long term observations.