Metals as chemical tracers to discriminate ecological populations of threatened Franciscana dolphins (Pontoporia blainvillei) from Argentina

Abstract

Franciscana dolphins are the most impacted small cetacean in the Southwestern Atlantic Ocean, classified as Vulnerable A3d by IUCN. Essential (Fe, Mo, Mn, Cr, Ni, Co) and non-essential (Ag, Pb, Sn) trace elements (TEs) were measured in liver, kidney, and brain samples of by-catch Franciscana dolphins that were living in estuarine (n = 21) and marine (n = 21) habitats (1) to assess whether TEs posed a threat and (2) to evaluate the suitability of TEs for discriminating ecological populations of this species in Argentinean waters. Essential TEs showed little variation in tissues from both groups in agreement with levels reported for other cetaceans and suggesting that these concentrations correspond to normal physiological levels. Non-essential TEs were higher in estuarine juveniles and adults dolphins than in marine specimens. These results suggest anthropogenic sources associated with estuarine area and that Franciscana dolphins are good sentinels of the impact of the environment. The difference in the concentrations of TEs beetwen ecological populations appeared to be related to distinct exposures in both geographical areas, and it is suggested that Ag and Sn concentrations in adults are good chemical tracers of anthropogenic input of TEs. These results provide additional information for improved management and regulatory policy.

A Synthesis of the Ecology, Human-Related Threats and Conservation Perspectives for the Endangered Franciscana Dolphin

“…With regard to trace elements, Seixas et al (2008) found that the concentrations of selenium (Se), total mercury (Hg), and organic mercury (OrgHg) were higher in the livers and kidneys of franciscanas from Rio Grande do Sul State than Rio de Janeiro State, Brazil. For both areas, the values were of the same order of magnitude as those reported in earlier studies with the same species from Brazil (Lailson-Brito et al, 2002;Kunito et al, 2004;Seixas et al, 2007) and Argentina (Marcovecchio et al, 1994;Gerpe et al, 2002;Denuncio et al, 2017;Romero et al, 2017). Franciscana livers showed higher concentrations of mercury, zinc, and copper relative to concentrations in other organs, whereas their highest cadmium concentrations were mostly found in kidneys (Marcovecchio et al, 1990;Gerpe et al, 2002;Lailson-Brito et al, 2002;Kajiwara et al, 2004;Seixas et al, 2008).…”

Trace element concentrations in the small Indian mongoose (Herpestes auropunctatus) from Hawaii, USA

“…6c). The median Pb values from the firing range was highest compared to some wild terrestrial (Kalisinska et al, 2016) and marine (Cardellicchio et al, 2002;Romero et al, 2017) mammals. Lead concentrations in all the brain samples from the Ukumehame firing range and two of the eight from Hilo Airport exceeded the mean Pb level observed in the brain of male rats (0.239 µg g −1 WW), which were exposed to 50 mg/L Pb and had increased ambulatory activity measured as lines crossed (Mansouri et al, 2012).…”

Assessment of Knowledge on Metal Trace Element Concentrations and Metallothionein Biomarkers in Cetaceans

“…This protective effect could be because essential metals (e.g., Zn) are inducers of the synthesis of metallothioneins (MTs), which are involved in metal detoxification [ 17 ]. The metal concentrations in cetaceans are mainly estimated in the kidney and liver because these organs are, respectively, involved in immune response, biotransformation of toxic compounds, and renal filtration; however, some studies are also focused on metal levels in muscle [ 7 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Unfortunately, it is not possible to compare the metal contaminations determined in distinct cetacean species, because they were collected in different geographical zones and years.…”