My research is placed at the transition between molecular, developmental and zooplankton biology. A large emphasis is to develop molecular tools to understand life history strategies and trophic interactions within an ecosystem. I am in particularly interested in the biology of Appendicularians. These fascinating filter feeders are second in abundance after copepods in many marine ecosystems and are though to shortcut the marine food web by feeding on marine bacteria. In addition, their feeding structure, which traps prey particles, is continuously discarded and replaced throughout the life cycle generating a flux of carbon from the surface layer to the deep sea.
This makes the role of Appendicularians in the marine ecosystem exciting and much research remains in order to understand more of their biology. Apart from occupying an interesting and important link in the marine food web, the Appendicularian, Oikopleura dioica, is an interesting model organism in molecular biology. They have a very small genome for a complex metazoan, a short generation time and are transparent. These criteria make developmental and gene expression studies of Appendicularians intriguing.
My research within developmental biology is to understand the link between time, age and developmental progression. The aim of this research is to create a common reference system and thereby combining knowledge from general life history, developmental and fundamental gene expression studies.
Barofsky A, Simonelli P, Vidoudez C, Troedsson C, Nejstgaard JC, Jacobsen HH, Pohnert G (2010). Growth phase of the diatom Skeletonema marinoi influences the metabolic profile of the cells and the selective feeding of the copepod Calanus spp.. J. Plankton Res., 32(3):263-272.
Simonelli P, Troedsson C, Nejstgaard JC, Zech K, Larsen BL, Frischer ME (2009). Evaluation of DNA extraction and handling procedures for PCR-based copepod feeding studies. J. Plankton Res., 31(12):1465-1474.
Troedsson C, Bouquet J-M, Skinnes R, Acuña J-L, Zech K, Frischer ME, Thompson EM (2009). Regulation of filter-feeding house components in response to varying food regime in the Appendicularian, Oikopleura dioica. J. Plankton Res., 31(12):1453-1463.
Bouquet J-M, Spriet E, Troedsson C, Otterå H, Chourrout D, Thompson EM (2009). Culture optimization for the emergent zooplanktonic model organism Oikopleura dioica. (Larvacean). J. Plankton Res. 31(4) 359-370.
Troedsson C, Simonelli P, Naegele V, Nejstgaard JC, Frischer ME (2009). Quantification of copepod gut content by differential length amplification quantitative PCR (dla-qPCR). Mar. Biol. 156:253-259.
Troedsson C, Lee RF, Walters T, Stokes V, Brinkley K, Naegele V, Frischer ME. (2008). Detection and Discovery of Crustacean Parasites in Blue Crabs (Callinectes sapidus) by 18S rDNA Targeted Denaturing High-Performance Liquid Chromatography (DHPLC). Appl. Environ. Microbiol. 74(14):4346-4353.
Troedsson C, Lee RF, Stokes V, Walters T, Simonelli P, Frischer ME (2008). Development of a Denaturing High-Performance Liquid Chromatography (DHPLC) Method for Detection of Protist Parasites of Metazoans. Appl. Environ. Microbiol. 74(14):4336-4345.
Nejstgaard JC, Frischer ME, Simonelli P, Troedsson C, Brakel M, Adiyaman F, Sazhin AF, Artigas LF (2008). Quantitative PCR to estimate copepod feeding. Mar. Biol. 153: 565-577.
Troedsson C, Ganot P, Bouquet J-M, Aksnes DL, Thompson EM (2007). Endostyle cell recruitment as a frame of reference for development and growth in the Appendicularian, Oikopleura dioica. Biol. Bull. 213: 325-334.
Troedsson C, Frischer ME, Nejstgaard JC, Thompson EM (2007). Molecular quantification of differential ingestion and particle trapping rates by the Appendicularian Oikopleura dioica as a function of prey size and shape. Limnol. Oceangr. 52(1): 416-427.
Aksnes DL, Troedsson C, Thompson EM (2006). A model of developmental time applied to planktonic embryos. Mar. Ecol. Prog. Ser. 318: 75-80.
Aksnes DL, Troedsson C, Thompson EM (2006). Integrating developmental clocking and growth in a life-history model for the planktonic chordate Oikopleura dioica. Mar. Ecol. Prog. Ser. 318: 81-88.
Troedsson C, Grahl-Nielsen O, Thompson EM (2005). Variable fatty acid composition of the pelagic Appendicularian, Oikopleura dioica, in response to dietary quality and quantity. Mar. Ecol. Prog. Ser. 289:165-176.
Troedsson C, Bouquet JM, Aksnes DL, Thompson EM (2002). Resource allocation between somatic growth and reproductive output in the pelagic chordate Oikopleura dioica allows opportunistic response to nutritional variation. Mar. Ecol. Prog. Ser. 243:83-91.
Spada F, Steen H, Troedsson C, Kallesoe T, Spriet E, Mann M, Thompson EM (2001). Molecular patterning of the oikoplastic epithelium of the larvacean tunicate Oikopleura dioica. J. Biol. Chem. 276: 20624-32.
Life History strategy
1. Phylogenetic microarrays and high-throughput sequencing: A new tool for biodiversity assessment in Northern Norway (NFR, Havet og Kysten, 2010-2014).
Our primary objective is to improve the resolution of current environmental monitoring programs (EMP). Towards this objective we aim to develop and evaluate the potential of using genomic-era technology (Environomics). Specifically, we aim to conduct:
1. Metagenome sequencing for biodiversity of current monitoring stations to evaluate the environomic approach.
2. Metagenome sequencing for biodiversity of several sensitive marine areas in Northern Norway, which will provide a baseline reference prior to any anthropogenic impact.
3. Development and evaluation of microarray technology for species detection for high throughput biodiversity monitoring (phylochip)
4. Set standards for the coupling between traditional morphology based taxonomy and modern chip-based technology.
We envision that the proposed approach to environmental sampling will set the standard for future monitoring programs yielding high frequency and spatial resolution data. Improvements of current EMP will generate:
1. Increased knowledge of marine environments and provide a solid foundation for coastal management. A priority of this application will be to generate baseline biodiversity data for sensitive marine areas in Northern Norway and in particular in the Barents Sea.
2. Increased knowledge of short and long-term effects that exploiting petroleum resources have on oceanic ecosystem structure, function and biodiversity. This includes oil leakage, but also general human activities.
2. Molecular markers to estimate algal diets of molluscs. (FNS, 2010-2011).
The principal objective of the KLEM project is to test molecular based methods to detect and quantify the algal preys of different commercial molluscs with the aim of advising the industrial partners about the feeding preferences (algal diet) of cultivated species to optimise their production. We will focus on the successful development of the semi-quantitative qPCR assays and will adapt them for investigating the diet of molluscs.
3. Response of pelagic foodwebs to warmer, acidified oceans. (NFR, Havet og Kysten, 2011-2014).
Atmospheric CO2 is projected to double by 2100, resulting in increased temperatures, ocean acidification (OA) and changes in the balance of marine ecosystems. While chemical effects of OA are well understood, the biological effects are less certain. Predictions include a shift in plankton communities towards smaller organisms, reduced carbon (C) export rates, and increased roles of gelatinous zooplankton in C cycling. Using a whole ecosystem approach we will test hypotheses that (H1) CO2 induced acidification, with warming, will result in a shift of autotrophic plankton communities favoring smaller flagellate species rather than large diatoms and (H2) acidification and warming will favor gelatinous plankton resulting in increased transfer of autotrophic production to the microbial loop. To address these hypotheses, we propose to conduct experiments using a multi-factorial design (CO2, temperature, presence/absence of gelatinous plankton). We will quantify and characterize autotrophic, heterotrophic, and bacterial plankton communities, growth and development rates of a model gelatinous plankter (Oikopleura dioica) and dominant copepod species, DOM production, fate, and turnover rates, as well as net microbial community respiration rates. By examining in detail the 'microbial black box', this proposal will generate data with clear implications for international biogeochemical initiatives which seek to provide understanding of global change and consequent effects on human society. Determining how gelatinous plankton alter C flows in a high CO2 world is also important in managing commercial fisheries as yields are controlled by C bioavailability to higher trophic levels and C transfer efficiency through planktonic food webs. Combining multidisciplinary international science and state of the art research facilities and approaches, provides a unique template for transformative research on impacts of OA on biologically mediated elemental flux through our changing oceans.
4. A novel cross-disciplinary approach to solve an old enigma: the food-web transfer of the mass-blooming phytoplankter Phaeocystis. (NFR, FriBio, 2011-2014).
Phaeocystis spp. are key primary producers in the world oceans, and seasonally constitute the majority of total pelagic biomass at higher latitudes. The trophodynamics of these algae are therefore of key importance for understanding some of the largest ecosystems on Earth. Despite decades of investigations the quantitative knowledge about these algae as food for zooplankton and subsequent productivity of higher trophic levels is limited and contradictory. Recent results suggests that this is due to large errors in laboratory estimates, methodological difficulties, and lack of knowledge about the influence of chemical signaling including anti-predational metabolites in situ. However, our recently developed molecular methods enable specific quantification of copepods and other zooplankton feeding on Phaeocystis in situ. Based on these, we propose to investigate feeding by the dominating micro- and mesozooplankton in Norwegian waters using a combination of molecular, specific stable isotope analysis and classical approaches. The dynamics of metabolites hypothesized to regulate the feeding on Phaeocystis (chemical signaling) will be simultaneously analyzed using cutting-edge metabolomic approaches. The project is based on a close cooperation by an established group of international leaders in their respective fields, and will develop Norwegian research skills and expertise through focus on training of young scientists in state-of-the-art methodology. To achieve a lasting effort towards gender equality we will promote female candidates combined with national and international network building. We have ambitious publication plans and anticipate considerable national and international interest. This project aims to establish advanced methodologies in quantitative aquatic ecology, and has a significant potential to increase the quantitative understanding of Phaeocystis in the global cycling of climate gases and transfer of energy to higher trophic levels, such as fisheries.