[en] We present here an innovative use of stable isotopes ratios of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) combined with mercury (THg) and selenium (Se) concentrations in seal body tissues as ecological tracers of harbour and grey seal foraging activities and exposure to Hg. SIBER (Stable Isotope Bayesian Ellipes) allows the use of stable isotope ratios, [Se] and [Hg] to build geometric spaces (or “isospaces”). These can be used as proxies of species ecological niches commonly referred to “isotopic niches” . Our objectives are (1) to evaluate potential temporal changes in foraging patterns and exposure of grey seals and harbour seals (2) to highlight the trophic plasticity of these two seal species in a changing environment.
A multi-tracer approach ([THg] and [Se]; 13C, 15N, 34S values) was applied to harbour seals and grey seals (blood; German and Scottish coasts, n=174 and n=80, respectively) during different time periods (from 1900 to 2017). Additionally, the same tracers were analysed in harbour seals (hair; from 1930 to 2017) from the Natural History Museum of Stockholm (n=10), free-ranging and stranded harbour seals from the North Sea (German and Belgian coasts, n=40 and n=6, respectively). SIBER package in R was used to explore the variation in the isotopic niche (δ13C vs. δ15N and δ15N vs. δ34S) and the ecological niches (δ13C vs. T-Hg, T-Hg vs. δ15N, δ34S vs. T-Hg, δ13C vs. Se, Se vs. δ15N and δ34S vs Se).
Our multi-tracer approach revealed:
(1) an increase of the size isotopic and ecological niche size in agreement with a more offshore foraging distribution, and an increase of benthic resources (more flatfish and less sandeels) for Scottish grey seals over time (Fig.1). In contrast, we calculated a smaller isotopic niche size for harbour seals over time likely linked to an increase of phytoplankton biomass, supporting zooplankton for planktivorous fish species such as clupeids.
(2) Long-term changes having affected the North Sea are reflected in hair collected from harbour seals (1930-2017). We found [THg] and δ13C values increased linearly with time. Higher δ13C values may be related to local higher primary productivity that may explain the possible increase of prey species abundance. Such increases may be related to changes in habitat use, particularly as tracking studies have shown that some foraging now occurs around wind farm installations.
Research Center/Unit :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Das, Krishna ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanographie biologique ; Université de Liège - ULiège > Freshwater and OCeanic science Unit of reSearch (FOCUS)
Siebert, Ursula; Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, 25761 Büsum, Germany
Damseaux, France ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanographie biologique
Pinzone, Marianna ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanographie biologique ; Université de Liège - ULiège > Freshwater and OCeanic science Unit of reSearch (FOCUS)
Lepoint, Gilles ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution ; Université de Liège - ULiège > Freshwater and OCeanic science Unit of reSearch (FOCUS) ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Laboratoire d'Ecologie trophique et isotopique
Gilles, Anita; Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, 25761 Büsum, Germany
Schnitzler, Joseph ; Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, 25761 Büsum, Germany
Jauniaux, Thierry ; Université de Liège - ULiège > Département de morphologie et pathologie (DMP) ; Université de Liège - ULiège > Fundamental and Applied Research for Animals and Health (FARAH) > FARAH: Santé publique vétérinaire
Pomeroy, Patrick; Sea Mammal Research Unit, Scottish Oceans Institute, East Sands, University of St Andrews, KY16 8LB, UK
Language :
English
Title :
Seals in a changing sea: an multi-tracer approach
Publication date :
01 May 2023
Event name :
SETAC Europe 33rd Annual Meeting
Event organizer :
The Society of Environmental Toxicology and Chemistry (SETAC)
Event place :
Dublin, Ireland
Event date :
30th April- 4th May 2023
Audience :
International
Peer reviewed :
Peer reviewed
References of the abstract :
We present here an innovative use of stable isotopes ratios of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) combined with mercury (THg) and selenium (Se) concentrations in seal body tissues as ecological tracers of harbour and grey seal foraging activities and exposure to Hg. SIBER (Stable Isotope Bayesian Ellipes) allows the use of stable isotope ratios, [Se] and [Hg] to build geometric spaces (or “isospaces”). These can be used as proxies of species ecological niches commonly referred to “isotopic niches” . Our objectives are (1) to evaluate potential temporal changes in foraging patterns and exposure of grey seals and harbour seals (2) to highlight the trophic plasticity of these two seal species in a changing environment.
A multi-tracer approach ([THg] and [Se]; 13C, 15N, 34S values) was applied to harbour seals and grey seals (blood; German and Scottish coasts, n=174 and n=80, respectively) during different time periods (from 1900 to 2017). Additionally, the same tracers were analysed in harbour seals (hair; from 1930 to 2017) from the Natural History Museum of Stockholm (n=10), free-ranging and stranded harbour seals from the North Sea (German and Belgian coasts, n=40 and n=6, respectively). SIBER package in R was used to explore the variation in the isotopic niche (δ13C vs. δ15N and δ15N vs. δ34S) and the ecological niches (δ13C vs. T-Hg, T-Hg vs. δ15N, δ34S vs. T-Hg, δ13C vs. Se, Se vs. δ15N and δ34S vs Se).
Our multi-tracer approach revealed:
(1) an increase of the size isotopic and ecological niche size in agreement with a more offshore foraging distribution, and an increase of benthic resources (more flatfish and less sandeels) for Scottish grey seals over time (Fig.1). In contrast, we calculated a smaller isotopic niche size for harbour seals over time likely linked to an increase of phytoplankton biomass, supporting zooplankton for planktivorous fish species such as clupeids.
(2) Long-term changes having affected the North Sea are reflected in hair collected from harbour seals (1930-2017). We found [THg] and δ13C values increased linearly with time. Higher δ13C values may be related to local higher primary productivity that may explain the possible increase of prey species abundance. Such increases may be related to changes in habitat use, particularly as tracking studies have shown that some foraging now occurs around wind farm installations.
