Linnaeus University’s first Wallenberg Scholar aims to understand how the Baltic Sea responds to climate change

There are nearly a billion bacteria in every litre of seawater. Understanding how bacteria grow and thrive is fundamental to understanding the health of entire ecosystems.

– Microscopic phytoplankton in the ocean are one of our planet’s lungs, and their interaction with bacteria is crucial for the ability to capture carbon dioxide and produce oxygen, says Jarone Pinhassi, professor of microbiology and Linnaeus University’s first Wallenberg Scholar.

The Wallenberg Scholar program was launched in 2009 with the aim of providing some of the country’s top researchers with substantial, unrestricted research grants. Jarone is one of the 118 active researchers currently part of the program. His project spans five years, with studies to be conducted in Swedish waters as well as in the Mediterranean and the Atlantic.

Intriguing questions that are still unanswered

Despite the crucial role bacterial processes in the ocean play in the global cycles of carbon, nitrogen, and phosphorus, there are only a handful of studies exploring how energy from rhodopsin affects bacteria’s ability to break down dissolved organic carbon in the ocean.

– A hypothesis we will now investigate is how rhodopsins enhance the efficiency of bacterial growth in light and how the ability to absorb various nutrients improves, says Jarone, emphasising that it is particularly interesting to examine how different bacteria utilise their rhodopsins during different seasons and how gene expression varies in connection with algal blooms.

– These are intriguing questions that are still unanswered. We also want to explore how bacteria contribute to the production of vitamins and other trace elements essential both for the ocean’s food chain and for human health. It is a fascinating thought that this new knowledge might one day be used to optimise the production of dietary supplements or improve processes for water purification.

A better understanding of the Baltic Sea

The desire to understand how nutrients and energy are cycled in the oceans forms the basis of Jarone’s and his fellow researchers’ work. An important goal is to gain a better understanding of how the Baltic Sea responds to climate change and how the breakdown of organic material works.

– Today, there’s widespread awareness of how important forests are for capturing carbon through photosynthesis, which in turn provides us with oxygen. But there aren’t as many people realising that photosynthesis happens just as extensively in ocean organisms. You could say that green plants on land are one of the planet’s lungs, and microscopic phytoplankton in the ocean are the other. Both are equally crucial for capturing carbon dioxide and producing oxygen.

Bacteria in seawater grow actively and act as decomposers of organic material, whether produced in the ocean or flowing in from rivers and other watercourses, including pollutants created by humans.

– We want to understand how bacteria thrive and function, and how they impact our oceans. This is the dream scenario for marine science as a whole – to understand what microorganisms thrive where and when, and how they are affected by different environmental conditions.

Sampling station off the coast of Öland

In addition to acting as decomposers, bacteria play the important role of producing nutrients for higher organisms. Jarone’s research group studies in detail what bacteria and phytoplankton produce different nutrients, vitamins, and fatty acids, and when they do so.

In this work, the sampling station Linnaeus Microbial Observatory, located ten kilometres off the coast of Öland, plays an important role. Approximately every other week, a sampling team travels to the station to collect water samples, which are then transported to the laboratory in Kalmar for analysis.

– We take regular samples to monitor the bacteria and observe variations across seasons and between years. Some bacteria thrive in the spring, while others prefer the autumn.

The same methods as the police

The Baltic Sea is particularly compelling, Jarone explains. Similar sampling stations exist in Hawaii and Bermuda, for example, but they do not experience such pronounced seasonal variations.

– We use genetic analyses here, the same molecular biology methods that the police use to analyse DNA. We examine what genes the bacteria have and how they are used. It’s easy to imagine bacteria as just tiny dots under a microscope, all looking the same, but their genetic makeup is incredibly diverse.

Being appointed a Wallenberg Scholar and receiving funding for independent research, says Jarone, provides an enormous opportunity to take a step closer to better understanding how marine ecosystems may respond to future environmental changes.

– It enables us not only to hire new staff but also to carry out costly analyses, such as field studies in the Baltic Sea and comparative studies of different oceans. We’ll also be able to buy certain equipment that we wouldn’t be able to afford otherwise. It’s fantastic!