The effects of climate change on antibiotic resistance development in commercially relevant fish species

Dr. Hassan Humeida, Dr. Jutta Wiese, GEOMAR

The oceans contribute 20% of animal protein to human diets worldwide and are even involved in meeting 50% of protein needs in poor countries. Climate change is impacting not only marine organisms but also the microbiomes that live on or within them. At the same time, the demand for food from the sea is increasing globally along with annual human population growth worldwide. Marine food sources are not infinite and their biodiversity is threatened by various factors, including human pollution and overfishing.  The following Masters thesis performed within the WASCAL program seeks to screen for antibiotic resistant bacteria from commercially relevant fish species of the Cape Verde Islands. The impact of the stressors on fish health status will be determined by measuring anatomical, physiological and nutritional parameters, such as size, weight, organ intactness, among others. This Master’s thesis will be performed GEOMAR Helmholtz Centre for Ocean Research in Kiel.

The sponge resistome along the Schwentine

Dr. David K. Ngugi, GEOMAR

The river Schwentine is of great importance for the drinking water supply of the city of Kiel. However, despite its current perception as a natural environment, the history of its entire length is closely linked to the industrialisation of the city of Kiel (including shipyards, hydroelectric power plants and sewage management). As such, the evolution of its animal inhabitants and their associated microbiota is expected to reflect this human-influenced history, in particular as reservoirs of antimicrobial resistance (AMR).

We will study antimicrobial resistance in the Schwentine River using metagenomics and metatranscriptomics. We will use freshwater sponges as a model animal reservoir for AMR. Sponges cover large areas of freshwater lakes and rivers. They filter suspended particles and microbes, removing up to 95% of the microbes in the water. The filtered microbes include pathogenic bacteria that often carry antibiotic resistance genes (ARGs), which can be inherited by the sponge microbiome.  

In this project, the goal is to understand whether freshwater sponges store ARGs that can be transferred to other microbes and passed up the food chain and drinking water. The Master’s thesis will be carried out at the GEOMAR Helmholtz Centre for Ocean Research in Kiel.

Light-dependent changes in microalgae content in the microbiome of the Baltic Sea sponge Halichondria panicea, and does this has an effect on sponge survival during heat waves (working title)

Dr. Kristina Bayer, GEOMAR

This project follows up on the long-standing observation that the Baltic Sea sponge H. panicea occurs in two color morphs, ranging yellow to green. Green sponges are typically found in light-exposed areas while yellow color morphs are located under rocks and in crevices. Initial unpublished microscopical observations revealed noticeably more diatoms and microalgae in green than in yellow sponges. First, we could use Fluorescence Activated Cell Sorting (FACS) to allow the quantification of photosymbiont abundance in green and yellow sponge tissues during different seasons. Moreover, we will provide additional analysis based on 16S rRNA and 18S rRNA gene amplicon sequencing on yellow and green sponge individuals collected at different months of the year with added sampling effort during the summer peak. This effort will unveil the diversity of prokaryotic and eukaryotic microorganisms coinhabiting the sponge. It will further assess whether seasonal changes in the photosynthetic microorganisms correlates with potentially detrimental effects of the core microbiome and subsequently for the sponge holobiont. This effort will give new insides, if microalgae content changes during warm season might have an effect on sponge health and/ or disease especially during heat waves, which was observed in earlier studies.

This master thesis is part of a jointed DAAD proposal with partners from Portugal, which could provide also the possibility for exchange.

Interested candidates please contact Kristina Bayer (kbayer@geomar.de) or Ute Hentschel (uhentschel(at)geomar.de) for further information. The thesis needs to start in march 2025, latest.