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The perilous state of the planet's coral reefs and the menace of harmful algal blooms are just two examples of current threats to our fragile marine ecosystems.
SENSENET, an EU-funded project that developed and tested new in-situ sensors for marine monitoring, successfully trained 16 PhD students and one postdoctoral researcher in these innovative techniques.
“The research network has enabled young scientists to test new ways of monitoring marine life so we can get an accurate real-time picture of what is happening in our seas,” says one of the researchers, Arjun Chennu, of the Max Planck Institute for Marine Microbiology in Bremen, Germany.
SENSENET brought together students from France, Germany, India, Italy, North Korea and Ukraine for doctoral projects in Europe via workshops, field placements and university-based training courses.
The projects developed various new optical and chemical sensors to measure key indicators, such as dissolved oxygen, acidity/alkalinity and nutrient levels in real time, and tested data collection and anti-fouling technology. Students were also involved in the development of a new long-distance underwater data-transmission system. These new techniques are desperately needed to help tackle marine environmental challenges, which require rapid and scalable data collection.
Monitoring the seafloor with new eyes
One of these PhD projects, led by Arjun Chennu, focused on the microalgae in the ocean. Microalgae, which are tiny microscopic plants, underpin the function and health of coastal ecosystems globally. These organisms form the base of the marine food web but are under stress due to rising sea temperatures and acidity.
Chennu studied the habitat of microscopic algae (microphytobenthos), the so-called “frontiers men” in marine ecosystems. “Just under half of photosynthesis – the chemical process that converts light energy to carbon dioxide and glucose to produce oxygen – takes place in water, and much of this work is done by microscopic marine algae, so they are vital for life on the planet,” he says.
The distribution and structure of these microalgae cannot be assessed with the naked eye and have traditionally involved laborious sampling. Designing and building an underwater field instrument to monitor and map the seafloor was Chennu's achievement. The instrument, called HyperDiver, uses hyperspectral imaging to create a picture by combining information from across the electromagnetic spectrum, drawing on visible light, infra-red and ultraviolet frequencies simultaneously.
HyperDiver technology allows scientists to image marine habitats in a way that is similar to satellite mapping techniques for Earth. The images are information-rich and can automate analyses of coral reef biodiversity or microalgal biomass. In addition, the migration and behaviour of marine microalgae can be studied. These are new capabilities which clearly put Europe at the forefront of global research.
Chennu’s work is just 1 of 53 academic papers published so far by the SENSENET students, with an additional 11 paper presented at conferences or as book chapters. Furthermore, the project has led to 75 conference contributions.
Several new chemical sensors have been developed and tested in the field. They include:
- Microfluidic lab-on-chip devices: these are used to measure seawater quality, including pollution indicators such as acidity/alkalinity, phosphate, dissolved iron and manganese. One or several lab functions are handled on a single chip of only a few millimetres.
- Electrochemical sensors: these are designed to measure nutrients such as sulphide, phosphate and dissolved oxygen in marine waters.
Further work focused on acoustic techniques, more specifically the use of sound to quantify flow rates from seepages of gas deep down on the sea floor. These gases, such as marine methane, are thought to be a significant factor in global warming.
“These and other new techniques developed and tested by the SENSENET team will help marine biologists keep a close watch and map important changes in the marine realm, alerting us to changes earlier and hopefully helping us preserve healthy ecosystems for future generations,” says Chennu.