Bone as a surrogate tissue to monitor metals in baleen whales.

Metals are massively deposited in the marine environment through direct emissions or atmospheric dry and wet depositions, a process since long enhanced by human activities. Metal contamination in the marine organisms has been increasingly investigated, but most research focuses on few tissues, elements and species considered indicative. Baleen whales have been scarcely studied in this respect. Here we contribute to the fragmented knowledge on this field examining the concentrations of zinc, copper, lead, titanium and strontium in the bone of fin whales (Balaenoptera physalus) from NW Spain and W Iceland. Bone was selected because it is a tissue commonly available in archival historic collections, and it is therefore useful to examine long-term trends in metal pollution. We tested differences between populations and we investigated age- and sex-related accumulation trends, as well as the occurrence of placental transfer. Sr concentrations and Pb accumulation rates with age were significantly higher in individuals from NW Spain than in those from W Iceland. Placental transfer occurred, at different levels, for all metals: as a result fetuses showed significantly higher Cu, Pb and Zn concentrations than adults. After birth, only Zn and Pb concentrations significantly increased with age. Through this study we contributed to fill some gaps in the knowledge regarding metal contamination in marine mammals, and we concluded that bone can be a suitable surrogate tissue to monitor a number of trace elements, provided that dissimilarities in tissue-specific deposition are taken into account when comparing concentrations from different tissues.

Fin whales and microplastics: The Mediterranean Sea and the Sea of Cortez scenarios.

The impact that microplastics have on baleen whales is a question that remains largely unexplored. This study examined the interaction between free-ranging fin whales (Balaenoptera physalus) and microplastics by comparing populations living in two semi-enclosed basins, the Mediterranean Sea and the Sea of Cortez (Gulf of California, Mexico). The results indicate that a considerable abundance of microplastics and plastic additives exists in the neustonic samples from Pelagos Sanctuary of the Mediterranean Sea, and that pelagic areas containing high densities of microplastics overlap with whale feeding grounds, suggesting that whales are exposed to microplastics during foraging; this was confirmed by the observation of a temporal increase in toxicological stress in whales. Given the abundance of microplastics in the Mediterranean environment, along with the high concentrations of Persistent Bioaccumulative and Toxic (PBT) chemicals, plastic additives and biomarker responses detected in the biopsies of Mediterranean whales as compared to those in whales inhabiting the Sea of Cortez, we believe that exposure to microplastics because of direct ingestion and consumption of contaminated prey poses a major threat to the health of fin whales in the Mediterranean Sea.

The fin whale, a marine top consumer, exposes strengths and weaknesses of the use of fluoride as ecological tracer.

Fluoride is retained in bone tissues of animals and its availability in the environment varies between regions according to natural and anthropogenic sources. These properties suggest this element as a suitable tracer of origin, distribution or movements of animals. In marine environments, krill builds-up fluoride concentrations that are transferred to its predators. In this study we examine the ability of bone fluoride concentrations to discriminate two separate populations of a krill consumer, the fin whale. Background levels of the sampling areas (Western Iceland and North-Western Spain) were determined through the analysis of krill samples. As expected, due to the high load of volcanic-derived fluoride in Icelandic waters, krill from W Iceland showed much higher fluoride concentrations than that from NW Spain. Concentrations in whales' bone were correlated with sex and age, increasing linearly with age in females and showing significantly lower values and a different age-related pattern of accumulation in males. Fluoride concentrations in whales' bone were much higher than in krill, indicating accumulation of the element but, rather unexpectedly, the area of origin had no influence on concentrations. This apparent contradiction may be explained either by the integration in bone of food consumed in other areas, or by the activation of homeostatic responses at very high levels of fluoride exposure. It is concluded that fluoride can be a useful tracer only if age and sex data are integrated into the analysis, year-round information on diet is available and/or the investigated population is exposed to mild levels of this element.