Methods

We apply common techniques for morphological and molecular species identification („integrative taxonomy“) and for assessing population connectivity and genetic diversity within a species. By looking at the standing stock of genetic variation, which lies at the basis of adaptation processes, and genetic connectivity patterns, we can better assess a species‘ resilience to environmental changes. Using (e)DNA metabarcoding datasets generated, typically producing high amounts of short DNA reads, we aim to infer population connectivity of various taxa, which is based on a new, still underexplored field called metaphylogeography.

Example publications:

• Murray A, Praebel K, Desiderato A, Auel H, Havermans C (2023) Phylogeography and molecular diversity of two highly abundant Themisto amphipod species in a rapidly changing Arctic Ocean. Ecology and Evolution 13(8): e10359.
• Havermans C, Hagen W, Zeidler W, Held C, Auel H (2019) A survival pack for escaping predation in the open ocean: amphipod-pteropod associations in the Southern Ocean. Marine Biodiversity 49(3): 1361-1370.
• Kaiser P, Bode M, Cornils A, Hagen W, Martínez Arbizu P, Auel H, Laakmann S (2018) High-resolution community analysis of deep-sea copepods using MALDI-TOF protein fingerprinting. Deep Sea Research I 138: 122-130.
• Havermans C, Seefeldt MA, Held C (2018) A biodiversity survey of scavenging amphipods in a proposed marine protected area: the Filchner area in the Weddell Sea, Antarctica. Polar Biology41(7): 1371-1390.
• Bode M, Laakmann S, Kaiser P, Hagen W, Auel H, Cornils A (2017) Unravelling diversity of deep-sea copepods using integrated morphological and molecular techniques. Journal of Plankton Research 39: 600-617.

With experimental work, exposing individuals of a certain species to different temperatures, we can identify the thermal window of its geographic populations along a poleward gradient, or its different life stages. This is done using ecophysiological measurements (e.g. respiration rate) and the evaluation of gene expression patterns, e.g. with whole-transcriptome analyses.  Such experiments based on thermal stress or a combination of multiple stressors allow to disentangle the role of local adaptation and to predict range shifts.

Example publications:

• Martinez-Alarcón D, Held C, Harms L, Auel H, Hagen W, Havermans C (2024) Race to the poles: the thermal response of the transcriptome of two range-expanding pelagic amphipod species. Frontiers in Marine Science11: 1336024.
• Kaiser P, Hagen W, Bode-Dalby M, Auel H (2022) Tolerant but facing increased competition: Arctic zooplankton versus Atlantic invaders in a warming ocean. Frontiers in Marine Science 9: 908638.
• Auel H, Hagen W (2017) Eine virtuelle Reise durch die Weltmeere - über Energieflüsse, Nahrungswege und Anpassungspfade. In: Faszination Meeresforschung Ein ökologisches Lesebuch (G Hempel, K Bischof, W Hagen, Hsgr.), 2. Auflage, Springer, Heidelberg, N.Y.
• Schukat A, Bode M, Auel H, Carballo R, Martin B, Koppelmann R, Hagen W (2013) Pelagic decapods in the northern Benguela upwelling system: Distribution, ecophysiology and contribution to active carbon flux. Deep-Sea Research I 75: 146-156.
• Teuber L, Schukat A, Hagen W, Auel H (2013) Distribution and ecophysiology of calanoid copepods in relation to the oxygen minimum zone in the eastern tropical Atlantic. PLoS ONE 8(11): e77590.

Trophic biomarkers such as fatty acids and stable isotopes (15N, 13C) provide powerful tools to study predator-prey interactions and food-web structure. They are based on the fact that certain biochemical components of the prey are incorporated into the consumer’s body tissue largely unchanged. “You are what you eat!” At the same time, they integrate dietary spectra over longer time spans of weeks to months compared to stomach/gut content analysis, which can only provide a snapshot of the latest meal. Our research team analyzes fatty acid profiles by gas-chromatography in order to elucidate feeding relationships in marine ecosystems and to trace dietary signals along the food chain. In addition, the stable isotope ratio of 13C provides information about primary production at the basis of the food web, whereas the stable isotope ratio of 15N can be used to characterize the trophic levels/positions of consumers.

Example publications:

• Bode M, Hagen W, Schukat A, Teuber L, Fonseca-Batista D, Dehairs F, Auel H (2016) Feeding strategies of tropical and subtropical calanoid copepods throughout the eastern Atlantic Ocean - Latitudinal and bathymetric aspects. Progress in Oceanography138: 268-282.
• Teuber L, Schukat A, Hagen W, Auel H (2014) Trophic interactions and life strategies of epi- to bathypelagic calanoid copepods in the tropical Atlantic. Journal of Plankton Research 36: 1109-1123. 
• Schukat A, Auel H, Teuber L, Lahajnar N, Hagen W (2014) Complex trophic interactions of calanoid copepods in the Benguela upwelling system. Journal of Sea Research 85: 186-196.

Environmental DNA (eDNA) represents both extra- and intracellular DNA, shed by a diversity of organisms to their surrounding environment. We focus on metazoan eDNA, shed by animals –floating or swimming through the water or present on the seafloor – in the shape of dead cells, mucus, skin, scales, faeces, excretion products, etc. This eDNA is collected from the water column using CTD rosette samplers or niskin bottles, which is then filtered through membrane filters, from which DNA can be isolated in the home laboratory. It is an efficient method to uncover the biodiversity in an area of rapid change, particularly for those animals that are not easily sampled with nets or trawls, like jellyfish. eDNA results are best to be combined with other methods such as video surveys or net catches, in order to obtain the most comprehensive biodiversity assessment. To improve on eDNA studies, we also carry out experiments on eDNA shedding and decay rates. Finally, species-specific assays can be developed in order to obtain quantitative values for target taxa, such as non-indigenous or range-shifting species.  

Example publications:

• Murray A, Priest T, Antich A, von Appen WJ, Neuhaus S, Havermans C (2024) Investigating pelagic biodiversity and gelatinous zooplankton communities in the rapidly changing European Arctic: an eDNA metabarcoding survey. Environmental DNA6(3): e569.
• Havermans C, Dischereit A, Pantiukhin D, Friedrich M, Murray A (2022). Environmental DNA in an ocean of change: Status, challenges and prospects. Arquivos de Ciências do Mar55: 298-337.

We commonly apply DNA metabarcoding studies on stomach contents in order to obtain a high resolution picture of the prey spectrum of particular species. The complementary use of this recent tool with biomarker analyses are particularly valuable, as DNA metabarcoding allows a high-resolution identification of the diet composition of a species, however representing only a temporal snapshot, whereas the former represents a long-term signal of food sources over time, albeit in a lower taxonomic resolution. We also use “natural samplers” of pelagic and benthic diversity, by investigating particular organisms that “sample” eDNA from the water or sediment. This represents a novel development in the field of eDNA, for which the high-throughput sequencing analysis of tissues or gut contents of such taxa (e.g., hydrozoans and sponges filtering liters of water per day; detritus-feeders that process large quantities of sediment), allows a most comprehensive assessment of pelagic and benthic diversity, respectively.

Example publications:

• Ruiz MB, Moreira E, Novillo M, Neuhaus S, Leese F, Havermans C (2024) Detecting the invisible through DNA metabarcoding: The role of gelatinous taxa in the diet of two demersal Antarctic key stone fish species (Notothenioidei). Environmental DNA 6(3): e561.
• Dischereit A, Beermann J, Lebreton B, Wangensteen OS, Neuhaus S,Havermans C(2024) DNA metabarcoding reveals a diverse, omnivorous diet of Arctic amphipods during the polar night, with jellyfish and fish as major prey.Frontiers in Marine Science14(11): 1327650.
• Dischereit A, Wangensteen OS, Praebel K, Auel H, Havermans C (2022) Using DNA metabarcoding to characterize the prey spectrum of two co-occurring Themisto amphipods in the rapidly changing Atlantic-Arctic gateway Fram Strait. Genes 13(11): 2035.