Marine Palynology and Paleoceanography

Males and females often show marked morphological differences. One important difference is in body sizes; think of the huge male elephant seal versus the small female, or the males of angler fish which are dwarf parasites on their female host. While in many invertebrates the female is the larger sex (possibly due to fecundity selection), males are typically the larger sex in many vertebrates (especially when there is male-male competition for females, the males hold territory or resources, and fight other males for access to females). There are a wide range of hypotheses to explain the degree of sexual size dimorphism (SSD), but often the tests of such theories has been restricted to the use of terrestrial species. Marine species often have very well documented body sizes, have diverse life histories, and marked male-female differences. They present excellent opportunities to tests theories of SSD. In this study you will put together comprehensive (quality controlled) data on the body sizes of the sexes of wide ranges of animal species from marine environments, and explore the diversity of size differences, and to examine possible drivers of these patterns (e.g. Rensch’s rule, Quantitative genetic theory). 

Taxa we may consider using in this exploration include: decapods and euphausiids, but many other taxa could be considered. We have to date explored such analysis in marine pelagic copepods:
Macroevolutionary patterns of sexual size dimorphism in copepods | Proceedings of the Royal Society B: Biological Sciences. And marine and freshwater fish: Selection for increased male size predicts variation in sexual size dimorphism among fish species | Proceedings of the Royal Society B: Biological Sciences.

Phytoplankton production is influenced by the available source of nitrogen (N) in the system. Assimilation of a new source of N, such as nitrate supplied by below the euphotic zone, fixes atmospheric CO2 and leads to “new production”, while assimilation of a recycled source of N such as ammonium leads to “regenerated production” with minimal or no CO2 fixed. Stable isotope (SI) analyses of nitrogen (N) and carbon (C) have been used extensively to study marine food webs with the δ15N of organic matter being an indicator of the trophic position of consumers in a food chain, while the δ13C of organic matter provides insights into the food source assimilated by a consumer. In this project we aim to i) identify the main N source assimilated by phytoplankton, ii) quantify primary productivity in the studied region.

The student will be analyzing samples collected during a cruise in the Azores in 2024 for stable isotope analyses of particulate organic N and C, and N and C uptake rates. 

Plastic pollution in the ocean is increasingly recognised as a persistent and complex problem. In this project, the student will collaborate with the student in the previous project (supervised by Helge Niemann) and characterize microbial degraders of micro and nanoplastics using DNA marker gene sequencing. The student will prepare sequencing libraries, potentially sequence at the institute and analyze microbial profile data. 

The student will learn DNA extraction, PCR, and microbial community data analysis techniques.

The genome of W. oceani XK5, a member of a major group of marine bacteria, encodes a truncated denitrification pathway enabling the reduction of nitrite (NO₂-) to nitrous oxide (N₂O), a potent greenhouse gas. We showed that, unusually, the XK5 strain reduces NO₂- into N₂O during stationary growth under oxic conditions. We aim to compare the transcriptomes of the XK5 strain under denitrifying and non-denitrifying growth conditions to assess the expression and regulation of its denitrification pathway. In this project, we will test the use of Nanopore sequencing to profile the XK5 strain transcriptomes via direct mRNA sequencing and analyze differences in gene expression, especially of the denitrification pathway, between growth conditions.

The student(s) will learn microbial cell culture, RNA extraction, library preparation for direct RNA sequencing, and data analysis techniques.