Diet of harbor porpoises along the Dutch coast: a combined stable isotope and stomach contents approach

in Marine Mammal Science (in press)

High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected ... [more ▼]

High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected along the Dutch coast (2006–2008) and their diet was assessed through stomach content and stable isotope analysis (d13C and d15N) of porpoise muscle and prey. Stable isotope analysis (SIAR) was used to estimate the con- tribution of prey species to the porpoises’ diet. This was compared to prey composi- tion from stomach contents, to analyze differences between long- and short-term diet. According to stomach contents, 90.5% of the diet consisted of gobies, whiting, lesser sandeel, herring, cod, and sprat. Stable isotope analysis revealed that 70-83% of the diet consisted of poor cod, mackerel, greater sandeel, lesser sandeel, sprat, and gobies, highlighting a higher importance of pelagic, schooling species in the porpoises’ diet compared to stomach contents. This could be due to prey distribution as well as differ- ences in behavior of porpoises and prey between the coastal zone and offshore waters. This study supports the need for multi-method approaches. Future ecological and fishery impact assessment studies and management decisions for porpoise conservation should acknowledge this difference between the long- and short-term diet. [less ▲]

Changes in trace elements during lactation in a marine top predator, the grey seal

in Aquatic Toxicology (2013), 126

Lactation in pinnipeds represents the most significant cost to mothers during the reproductive cycle. Dynamics of trace elements and their mobilization associated with energy reserves during such an ... [more ▼]

Lactation in pinnipeds represents the most significant cost to mothers during the reproductive cycle. Dynamics of trace elements and their mobilization associated with energy reserves during such an intense physiological process remains poorly understood in marine mammals. The changes in tissue concentrations of 11 elements (Ca, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) were investigated in a longitudinal study during the lactation period and during the post-weaning fast period. Blood, milk, blubber, and hair samples were collected sequentially from 21 mother-pup pairs of grey seals (Halichoerus grypus) from the Isle of May in Scotland. Maternal transfer through the milk was observed for all trace elements, except for Cd. As an indicator of the placental transfer, levels in pup lanugo (natal coat) revealed also the existence of maternal transfer and accumulation of all assayed trace elements during the foetal development. The placental and mammary barriers against non-essential metal transfer to offspring appear to be absent or weak in grey seals. Examining the contamination levels showed that this grey seal population seems more highly exposed to Pb than other phocid populations (2.2 mg/kg dw of grey seal hair). In contrast, blood and hair levels reflected a lower Hg exposure in grey seals from the Isle of May than in harbour seals from the southeastern North Sea. This study also showed that trace element concentrations in blood and blubber could change rapidly over the lactation period. Such physiological processes must be considered carefully during biomonitoring of trace elements, and potential impacts that rapid fluctuations in concentrations can exert on seal health should be further investigated. [less ▲]

Mercury in blood of free-ranging seals Phoca vitulina from the North Sea: Time-trend and association with environmental factors

Conference (2012, March 27)

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment ... [more ▼]

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment. Recently, development of monitoring programs and non-invasive sampling techniques, including seal catches allowed blood sampling on a regular basis together with measurements of blubber thickness, body mass, sex and body length. Concentrations of total mercury (T-Hg) and other trace elements (Cd, Pb, Zn, Cu, Fe) as well as ∂13C and ∂15N values were determined by mass spectrometry in blood of 75 wild harbour seals caught in the German Wadden Sea between 1997 and 2011. ∂13C and ∂15N mean values (-17.5‰ and 18.1 ‰ respectively) were strongly similar to that measured previously in the muscle of stranded harbour seals from the Wadden Sea. In contrast, ∂15N mean value was strikingly higher than that recorded in grey seals (Halichoerus grypus) from Scotland (14.1 ‰ respectively; Habran et al. submitted.) while ∂13C values remained similar between the two seal species. These values confirmed the high trophic position of the harbour seal in the North Sea. In contrast to Cd and Pb, T-Hg in blood harbour seals reached concentrations as high as 2.1 μg.g-1 dry weight (10 times higher than the 0.21 μg.g-1 dry weight recorded for grey seals from Scotland) but depended on several factors including ∂15N values, age group and the body mass. T-Hg was detected in juveniles confirming maternal transfer to offspring and time-trend revealed no decrease of T-Hg in blood of harbour seals these last 15 years. [less ▲]

Cadmium toxicokinetics and bioaccumulation in turtles: trophic exposure of Trachemys scripta elegans

in Ecotoxicology (2012), 1

Ecotoxicological data in reptiles are mainly represented by field studies reporting tissues burden of wild-captured individuals but much less is known on processes of uptake, depuration, accumulation and ... [more ▼]

Ecotoxicological data in reptiles are mainly represented by field studies reporting tissues burden of wild-captured individuals but much less is known on processes of uptake, depuration, accumulation and effects of inorganic contaminants in these species. In this study, females’ Trachemys scripta elegans were exposed to cadmium (Cd) through a CdCl2 supplemented-diet with increased environmental relevant concentrations during 13 weeks and then went through a decontamination phase during 3 weeks being fed uncontaminated food. Blood and feces were collected during the three phases of the experiment and the turtles were sacrificed at the end of the experiment and organs samples collected. The Cd concentrations in blood remained stable over the course of the experiment while Cd concentrations in feces increased with time and with amount of Cd ingested. Assimilation efficiency in liver and kidney together was low (0.7 – 6.1 %) but did occur and Cd accumulated in a dose-dependent manner in organs in the following order of concentrations: kidney>liver>pancreas>muscle. In terms of organs burden, Cd-burden was the highest in liver followed by kidney and pancreas. The assimilation efficiency decreased as Cd ingested increased suggesting that at higher dose of Cd absorption decreased and/or depuration increased. Mineral content of the liver was modified according to Cd level with increased concentrations of zinc and iron with increasing Cd levels. Accumulation of Cd had no effects on survival, food consumption, growth or weight and length suggesting no effect of treatment on females’ body conditions. [less ▲]

Use of Physiologically Based Pharmacokinetic (PBPK) Models in Marine Mammal Toxicology

in Kawaguchi, M.; Misaki, K.; Sato, H. (Eds.) et al Interdisciplinary Studies on Environmental Chemistry—Environmental Pollution and Ecotoxicology (2012)

Physiologically based pharmacokinetic (PBPK) models are mathematical models that are largely based upon the physiological characteristics of the species and the biochemical properties of the chemical of ... [more ▼]

Physiologically based pharmacokinetic (PBPK) models are mathematical models that are largely based upon the physiological characteristics of the species and the biochemical properties of the chemical of interest. They quantitatively describe and predict the kinetics of pollutants inside the body and can be of major importance for risk assessment of chemicals in marine mammals. PBPK models which consist of five compartments (liver, blubber, kidney, brain, and the rest of the body) were made for selected polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in order to address the bioaccumulation of these compounds in tissues of harbour porpoises (Phocoena phocoena). Harbour porpoises have relatively long life spans, are common cetaceans in the North Sea, a heavily polluted area, and are known to be very sensitive to pollution. Models developed for all compounds (some PCBs and PBDEs) were evaluated using existing datasets from the literature and from analyses performed by GC-MS, the latter being obtained from stranded porpoises in the Black Sea and the North Sea over a period of 18 years (1990–2008) to assess spatial and temporal trends in bioaccumulation of the respective PCBs and PBDEs. We demonstrate that PBPK models are a feasible computational approach that can be used as a non-destructive tool for predicting the chemical pollution status of the marine mammals. [less ▲]

Feeding ecology of harbour porpoises: stable isotope analysis of carbon and nitrogen in muscle and bone

in Marine Biology Research (2012), 8(9), 829-841

Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N ... [more ▼]

Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch coast (2006􏰄2008). In addition, samples from 30 prey species were analysed. Prey samples showed high d15N values in species of higher trophic level. In addition, geographic differences in isotopic composition were found, with higher d15N and d13C values in prey from more southern, coastal and estuarine areas. Based on muscle d15N values, we found neonatal enrichment and that larger porpoises, in particular males, seem to feed on lower trophic level species, compared to smaller individuals. Also bone d15N values show that larger animals had fed on lower trophic levels in distant times. Porpoises from the Eastern Scheldt reveal distinct d13C values in muscle, but not in bone. This shows that these animals had foraged in the Eastern Scheldt for a longer time period but were not born there. Seasonal variation in bone d15N and d13C values revealed two distinct groups of porpoises along the Dutch coast, a winter group (mainly males) that migrated from neighbouring regions and a Dutch subpopulation in summer. These results furthered our insight about shifts in trophic level and feeding location of harbour porpoises from the southern North Sea over time. [less ▲]

The sheepshead minnow Cyprinodon variegatus as a marine vertebrate model for investigating endocrine disrupting effects of triclosan

Poster (2012)

Zebrafish (Danio rerio) has been a prominent model in toxicology. This freshwater species present many advantages both in identifying endpoints of toxicity and in elucidating mechanisms of toxicity ... [more ▼]

Zebrafish (Danio rerio) has been a prominent model in toxicology. This freshwater species present many advantages both in identifying endpoints of toxicity and in elucidating mechanisms of toxicity. However, marine toxicologists lack such omnipotent model displaying similar advantages to zebrafish: small size, rapid breeding, and easy maintenance. We propose here the use of the sheepshead minnow Cyprinodon variegatus to define thyroid-disrupting effects of triclosan during pre-hatching development. Three females and two males were placed in each of the three breeding chambers designed for this experiment. More than 300 eggs were collected over three days and maintained in seawater with triclosan concentrations at 0, 100 ng.L-1, and 100 µg.L-1. Exposure of larvae to triclosan lasted until hatching. After hatching (six days post-spawning), 5 larvae per condition were placed in Bouin’s fixative for brain and thyroid histology. Length and body mass were measured. The body was frozen at -80oC to determine muscle thyroid hormone levels (T3 and T4), using radio-immunoassay techniques. Hatching success, in vivo observations, gross observation, thyroid hormone levels, histology will be determined and discussed in the framework of whether or not triclosan may alter thyroid metabolism during pre-hatching period of the sheepshead minnow. [less ▲]

Environmental factors affecting thyroid function of wild sea bass (Dicentrarchus labrax) from European coasts

in Chemosphere (2012)

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 ... [more ▼]

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 wild sea bass collected near several estuaries: namely the Scheldt, the Seine, the Loire, the Charente and the Gironde. Thyroxine (T4) and triiodothyronine (T3) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfatation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that are predicted to lead to an increased conversion of T4–T3 and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. From all compounds tested, the higher chlorinated PCBs seemed to be the most implicated in this perturbation. [less ▲]

Toxicokinetics of selenium in Chelonians: trophic exposure in Trachemys scripta scripta

(2011, December)

Background. Se is primordial for all development stages in oviparous species but can induce cellular damages (e.g. oxidative stress, histopathotoxicity) , embryo- and immunotoxicity (Usdi 1998; Hoffman ... [more ▼]

Background. Se is primordial for all development stages in oviparous species but can induce cellular damages (e.g. oxidative stress, histopathotoxicity) , embryo- and immunotoxicity (Usdi 1998; Hoffman 2002) , even at low concentration. Unlike birds and fishes, little is currently known on Se toxicology in reptiles, such as turtles. Most studies reported tissue burdens from field-captured or death animals but rarely provided an understanding of the dose, duration or pathway of exposure. Our present study aims to investigate toxicokinetic of Se through an in vivo and per os exposure of the yellow-bellied slider turtle Trachemys scripta scripta. Furthermore relationship between Se concentration in internal tissues (liver, kidney, muscle ) and external tissues (carapace, skin, blood) will evaluate usefulness of these last in the framework of non-invasive sampling in protected turtle species. Methodology. 160 yellow-bellied slider turtles, around four weeks old, were acquired in September 2010 and placed by pair in individual tank for a six-month acclimatization period. Lengths, as straight carapace length SCL, ranged from 1.7 to 6.4 cm. Three groups of 42 individuals each were designed. The feeding trial consisted in an eight-week supplementation period followed by a four-week depuration period. At some intervals during that time scale, six individuals per group were sacrificed and tissues were collected (carapace, scutes, skin, blood, liver, kidney, muscle) for selenium analysis. During the supplementation period, turtles were fed with diet containing 0 (control) , 23 or 47 µg.g-1 of selenium as seleno-L-methionine. During the depuration period, the remaining individuals were fed with non-supplemented control diet. Total selenium was investigated by ICPMS. Results and discussion. The Se-concentration in all collected tissues increased in a dose-dependent way over the course of the supplementation period. Se accumulation had no effect on survival, diet behavior or growth. Higher Se levels were observed in kidney, followed by muscle and blood. During the recovery period, Se levels decreased in tissues in a significantway except in blood, muscle and carapace. Blood, skin and carapace Se levels were positively correlated to those in kidney and muscle. Such relationships were also observed between liver and carapace, and blood. Results suggested a Se transfer through the food intake and the potential use of carapace and skin as relevant tools in non-invasive biomonitoring studies. [less ▲]

Ecotoxicology of marine predators: Strategy and perspectives

Scientific conference (2011, October 25)