Marine Microbial Ecology Group – MMEco

November 2024 – Effect of temperature and nutrient pollution on marine microcosms

In this project, intern Luuk van Wieren is investigating how marine microbial communities respond to nutrient pollution and temperature changes. How do these changes affect the biodiversity in the sediment and the water column?

After a sampling campaign at Tjärnö, the microcosms are being incubated along temperature and nutrient density gradients and routinely monitored. The data will be compared with samples collected in the field to further improve our knowledge of the effects of temperature and nutrient pollution on the marine microbial ecosystem.

Bacterial community assembly in aquaria (2024-2027)

Traditionally, marine microbial communities have been known to be affected by temperature, but it is still unknown how this affects specific community assembly and interactions. For this study, PhD student Nicolai Laufer is currently implementing a microbial time series using aquariums as a model system.

Aquarium systems are designed to mimic natural environments as closely as possible, while providing a controlled system with reduced complexity and biodiversity compared to natural ecosystems. In collaboration with the Maritime Museum Aquarium in Gothenburg, we are sampling the bacterial biodiversity of four aquaria since January 2024. We will compare the microbial biodiversity with other marine environments.

Our results will help us to explain the long-term structural and functional community dynamics that we observe in natural marine microbial communities, but that are difficult to understand due to the high complexity of natural ecosystems. This will facilitate our ability to predict how microbes and their provision of essential ecosystem services will be affected by events such as global warming.

This project is funded by Kungl. Vetenskapsakademiens stiftelser and from the Carl Trygger Foundation.

Marine prokaryotes, keystone populations in the changing ocean (2025-2028)

Marine bacteria play a critical role in the turnover of organic carbon in the microbial cycle, influencing the amount of carbon stored in the ocean or removed from long-term storage by respiration.

Research on ocean change often overlooks bacteria, and there is no consensus on the effects of climate change on marine microorganisms, yet it is important to understand how they cope with and contribute to changing oceans.

In this project, we will sample seawater and natural communities in different ecosystems. We will investigate which microbes contribute to the turnover of organic carbon in different ocean regions and temperatures. The results will help us understand the link between microbial community assembly and nutrient cycling, and improve our holistic understanding of marine ecosystems and the impact of ocean change on microbial communities.

This project is supported by Vetenskapsrådet.

Effects of nutrient stoichiometry on bacteria and nutrient cycles (2024-2027)

To address the challenge of how microbes combat and contribute to climate change, PhD student Teresa Peil will study how marine microbial diversity affects organic carbon turnover under varying nutrient supply regimes.

Nutrients, along with temperature, are a major environmental driver and are predicted to change in concentration and stoichiometry in highly productive coastal environments. Her project aims to understand how these changes affect microbes, how they interact with each other, and how this affects the ocean's carbon balance.

Teresa Peil isolated bacteria from seawater samples collected off the west coast of Sweden. After characterization, these isolates will serve as model organisms for co-culture experiments. Specifically, the effect of varying nutrient and trace metal concentrations on bacterial growth on different types of organic matter will be investigated.

This project is a collaboration with Claudia Ehlert and Maren Striebel at the University of Oldenburg and is funded by FORMAS.

Who actually denitrifies? (2024-2027)

The oceans are a major source of atmospheric nitrous oxide, a potent greenhouse gas and oxygen depleted waters are known to be areas with high nitrous oxide emissions. Nitrous oxide is produced and consumed by microbial nitrogen transformations, but we lack an in-depth understanding of the biogeochemical pathways, their environmental controls and the microbes involved.

Previous studies have shown that denitrification is the dominant production pathway, and related genes are found across all three domains of life. However, many microbes are only capable of partial denitrification.

Hence, PhD student Alisa Wüst wants to investigate the different steps of denitrification and linking it to microbial activity to potentially identify main contributors by undertaking work in an oxygen depleted system, the Gulfo Dulce, Costa Rica. We will be utilizing novel isotope labeling techniques, highly sensitive optical oxygen sensing techniques and in situ incubations as well as transcriptomic and genomic sampling.

This project is in collaboration with Laura Bristow, Department of Marine Sciences, University of Gothenburg, and PhD student Alisa Wüst.

Response of plankton communities to elevated methane concentrations (2022-2024)

In this project, we want to understand how plankton responds to elevated gas concentrations, in this case methane. Can plankton communities buffer potential short-term harmful effects? Are bacteria quick to react when methane gas concentrations increase?

Plankton forms the base of the food web in the ocean and its productivity and biomass is important to support other organisms. Methane gas from biological activity is naturally present in some ocean regions, but here we want to look specifically at the mechanisms of what happens when large amounts of methane gas meet surface plankton communities. The greenhouse gas methane is produced naturally through biotic processes, but the effects of very high concentrations on the sensitive ecosystem of the Baltic Sea are unknown.

With this project we investigate whether the abundance and activity of methanotrophic bacteria increases in response to gas leaks. Ultimately, this knowledge will help to identify and shape possible responses to future gas emissions that can contribute to a healthier ocean.

The project is funded by Aquacosm-plus, FORMAS, and BalticWaters2030.

Bacterial interactions and biogeochemical models (2020-2024)

Biogeochemical models are powerful tools to assess how the large ocean reservoir of carbon influences and is influenced by the climate system. However, the high diversity of organic carbon compounds, microbial communities and their interactions is a challenge for modelling approaches.

Here, we use controlled experimental conditions to disentangle the influence of microbial interactions on dissolved organic carbon biogeochemistry, by combining practical microbial experiments with a modelling perspective in a case study.

This project is a collaboration with Jessika Füssel and Sinikka Lennartz, University of Oldenburg, Germany and funded by the Add-on fellowship for Interdisciplinary Life Sciences of the Joachim-Herz-Foundation.  

More about the project: Biogeochemical Ocean Modelling.

Linnaeus Microbial Observatory (LMO) - disentangling seasonal plankton dynamics (2011-ongoing)

The Linnaeus Microbial Observatory, LMO, is a time-series station in the Baltic Sea Proper and the core of many research projects in microbial oceanography at Linnaeus University.

Since many years, we collaborate on the topic of bacterioplankton community dynamics and links to dissolved organic matter turnover.

More about the station: Linnaeus Microbial Observatory