The Krill Gut Microbiome project (KiGuMi) explores the microbial diversity contained within the digestive tract of Antarctic krill, Euphausia superba. Krill contain unique enzymatic equipment which allows for the highly effective hydrolytic breakdown of complex substrates. The biomass estimate of E. superba in the Southern Ocean is approximately 379 million tons and corresponds to 300-400 trillion individuals, making Antarctic krill one of the largest biomasses of any wild-living species. The volume of an average individual’s digestive tract is estimated to be 100 ul, which means the entire population of krill contains an enormous reaction space (up to 8 x 107 m3) for the turnover of complex organic matter and for the potential to discover relevant enzymes for biotechnology. However, the microbial community and metabolic pathways occurring within krill’s digestive tract have yet to be studied in detail. KiGuMi scientists explore the microbial diversity of dissected digestive tract tissues (stomach, digestive gland, and hind gut), establish the first metaOMICS for this system, and discover hydrolytic enzymes and microbes that potentially have biotechnical applications.
Population Shift and Ecosystem Response – Krill vs. Salps (POSER)
The western Atlantic sector of the Southern Ocean (SO) and the northern part of the Western Antarctic Peninsula (WAP) in particular is one of the fastest warming areas on the planet, making this part of the SO to an invaluable observatory for ecosystem responses to climate change. Long-term data sets indicate a significant decrease of sea ice cover leading to shifts on different levels in the WAP region such as a decline in krill abundance in the northern part of the WAP and an increase of salp populations as well as a shift in food quality and quantity. Due to their delicate feeding basket, salps prefer ‘warmer’, ice-free waters with lower phytoplankton concentrations. Krill and salps are among the most important grazers in the SO, occupying completely different ecological and spatial niches. They differ remarkably in their life cycles, their mode of feeding and reproduction, the way they fuel the lower food web by organic matter release and the upper tropic levels as prey and in their importance for the SO-fishery. Therefore, shifts in dominance between these two groups will most likely trigger a cascade of short- and long-term changes in ecosystem structure and function, affecting both the functional biodiversity and biogeochemical cycles in the pelagic system of the western Atlantic sector of the SO. The overall aim of POSER is to understand how krill and salps influence productivity, regeneration of macronutrients (N, P, Si) and micronutrients (FE, Zn, Co, Cu, Cd, Pb) with a special focus on Fe, carbon export and structure of the microbial food web in the western Atlantic sector of the Southern Ocean. The interdisciplinary approach will allow predicting the causal effect of climate induced environmental changes on a) the population dynamics of key players in the pelagic system (krill, salps) and b) the consequences of an abundance shift of these organisms on the lower trophic food web, stoichiometry, and carbon flux. Given the important role of the Antarctic food web in the global ocean, our project has a large societal relevance enabling us to predict the consequences of global warming for the Southern Polar Ocean.
International: Prof. Dr. Evgeny Pakhomov, University of British Columbia (UBC), Canada, Dr. Marina Monti, Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS), Italy.
Duration 2016-2020
Financial Support Ministry for Science and Culture of Lower Saxony (MWK) The project and the financial support are located at the University of Oldenburg.
The Performance of Krill vs. Salps to withstand in a warming Southern Ocean (PEKRIS II)
Project description
Antarctic krill (Euphausia superba) is a key structural element for the functional biodiversity of the Southern Ocean ecosystem and an important target of a highly specialized fishing industry which is almost exclusively localized in the south-west Atlantic sector of the Southern Ocean, where krill has the highest abundance. However, this region has seen some of the greatest impacts from climate change on the planet, affecting biodiversity and the integrity of the pelagic food web. In addition, the increasing abundance of the tunicate Salpa thompsoni make predictions on future population dynamics of krill extremely difficult. The first phase of the PEKRIS project aimed to improve our understanding of the population dynamics of salps and krill in the Southern Ocean in relation to climate change by examining the temperature dependence of physiological processes in field and laboratory experiments and then summarizing the results through models. During the PEKRIS project crucial knowledge gaps and additional research needs were identified including, the influence of increased water temperatures on the reproductive capacities of the parental generations and offspring of both species, the effects of changing food quality and quantity, and the influence of krill fisheries in spawning areas. These knowledge gaps form the basis for PEKRIS II. New empirical data integrated into ecological models, together with the results from the first phase, will allow for more realistic predictions about the effects of climate changes on the ecosystem of the Southern Ocean and support a more adaptive risk assessment of the krill fishery in the Southern Ocean.
Krill biomass estimation in the Southern Ocean (KrillBIS II)
The aim of KrillBIS II is to continue krill stock research as a tool for the science-based decisions of the German Federal Ministry of Food and Agriculture (BMEL) and ensure the contribution of German research within the framework of the Commission for the Conservation of Living Marine Resources in the Antarctic (CCAMLR). At present, catch quotas are estimated using fishery pressure, the abundance and distribution of krill predators, and predator dependence on krill abundance and distribution. However, KrillBIS I showed that focusing more on the biology of krill, the seasonal distribution pattern of its developmental stages, and the ability of krill to adapt to climatic environmental changes is urgently need to improve conservation. The KrillBIS II project supports the development of krill specific data for this new approach and analyzes the extent it improves on the management of the krill population compared to the previous predator-centered approach. In order to realize this: a) the current level of knowledge of krill must be analyzed to uncover knowledge gaps, b) How these knowledge gaps can be closed must be identified, and c) existing data on the biology and adaptability of krill must be integrated into models in order to enable predictions on population development under various climate scenarios.
CHASE - CHronobiology of changing Arctic Sea Ecosystems
Biological clocks are central to all living systems. They provide a measure of time so that organisms can anticipate and adapt to cyclic changes in their environment. While the genetic basis of this clock is well established in terrestrial species it has remained, until recently, elusive in marine organisms. New findings by our group suggest that in zooplankton, circadian clock genes underpin daily behavioral/physiological rhythms. By measuring day-length, the circadian clock synchronizes the timing of seasonal life cycle events in response to annual cycling changes in light conditions (photoperiodism). As the Arctic Ocean is warming, zooplankton are undergoing habitat range extensions polewards. This will result in exposure to new and more extreme day-lengths (photoperiods) at the higher latitudes – known in many terrestrial species to have negative consequences on fitness. We therefore aim to investigate the behavior, physiology and genetic responses of two ecologically central taxa, the copepod Calanus finmarchicus and the euphausiid Thysanoessa inermis to their natural and new photoperiodic environments. The central hypothesis of CHASE is that changes in photoperiod will disrupt the ticking of the circadian clock and the timing of important daily and seasonal life-cycle events.
MEMAREs - Understanding the MEchanistic bases of MArine clocks and Rhythms in the Antarctic key species Euphausia superba
Biological clocks are found in almost all life forms, from bacteria to humans, and enable organisms to anticipate environmental cycles and regulate their behaviour and physiology accordingly. While the mechanistic principles of these endogenous timing mechanisms have been extensively studied in terrestrial model species (e. g. fruit fly or mouse), little is known in the marine environment, where life – and correspondingly, biological clocks – have evolved. Antarctic krill (Euphausia superba) is a key species endemic to the Southern Ocean, which is a high latitude region characterized by extreme seasonal fluctuations in environmental factors (photoperiod, sea ice extent, food availability). The life cycle of Antarctic krill is shaped by strong diel rhythms (DVM, metabolic activity), synchronized to the day-night cycle, and seasonal rhythms (growth, lipid accumulation, gene expression), synchronized to the seasonal change in photoperiod and food availability, making Antarctic krill highly adapted to a life under extreme conditions. Recent investigations suggest the involvement of an endogenous clock in both, diel (DVM, metabolic activity) and seasonal (e. g. growth, enzyme activity and gene expression) processes. Moreover, the molecular components of an endogenous clock have been characterized in E. superba in a transcriptomic study. However, nothing is known about the underlying mechanistic principles and the neuronal architecture of this clock and how it is synchronized to the environment, which is the key to understand diel and seasonal timing in Antarctic krill. With parts of the Southern Ocean experiencing rapid warming caused by anthropogenic driven climate change, it is of fundamental interest to understand the involvement of endogenous timing mechanisms into life cycle functions of Antarctic krill. By combining seasonal field samplings and molecular biological methods with laboratory experiments (behaviour, metabolic activity) the MEMAREs project aims to further understand the underlying principles of diel and seasonal timing in Antarctic krill to gain insights into its plasticity towards environmental change.
