Contrasted accumulation patterns of persistent organic pollutants and mercury in sympatric tropical dolphins from the south-western Indian Ocean

Abstract

Due to their high trophic position and long life span, small cetaceans are considered as suitable bioindicators to monitor the presence of contaminants in marine ecosystems. Here, we document the contamination with persistent organic pollutants (POPs) and total mercury (T-Hg) of spinner (Stenella longirostris, n =21) and Indo-Pacific bottlenose dolphins (Tursiops aduncus, n=32) sampled from the coastal waters of La Réunion (south-western Indian Ocean). In addition, seven co-occurring teleost fish species were sampled and analyzed as well. Blubber samples from living dolphins and muscle from teleosts were analyzed for polychlorinated biphenyls (PCBs), DDT and metabolites (DDTs), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and polybrominated diphenyl ethers (PBDEs). Methoxylated PBDEs (MeO-PBDEs), reported as having a natural origin, were also analyzed. T-Hg levels were measured in blubber and skin biopsies of the two dolphin species. Stable isotopes δ(13)C and δ(15)N values were determined in skin of the dolphins and in the muscle of teleosts. For PCBs, HCHs and T-Hg, concentrations were significantly higher in T. aduncus than in S. longirostris. For other POP levels, intra-species variability was high. MeO-PBDEs were the dominant compounds (55% of the total POPs) in S. longirostris, while PCBs dominated (50% contribution) in T. aduncus. Other contaminants showed similar profiles between the two species. Given the different patterns of POPs and T-Hg contamination and the δ(15)N values observed among analyzed teleosts, dietary and foraging habitat preferences most likely explain the contrasted contaminant profiles observed in the two dolphin species. Levels of each class of contaminants were significantly higher in males than females. Despite their spatial and temporal overlap in the waters of La Réunion, S. longirostris and T. aduncus are differently exposed to contaminant accumulation.

Linking pollutant exposure of humpback whales breeding in the Indian Ocean to their feeding habits and feeding areas off Antarctica

“…It completes works recently conducted on fish and dolphins sampled off La Reunion (Dirtu et al, 2016), and increases the knowledge related to the southern Indian Ocean sector. Our results provide the first published records of d 13 C and d 15 N values in skin biopsies from humpback whales from the Southern hemisphere and these data reflect their dietary sources.…”

“…Due to a lower trophic position, low POP concentrations are measured in most baleen whales compared to toothed whales (Dirtu et al, 2016;Kunito et al, 2002;Pinzone et al, 2015). POP concentrations in the tissues of humpback whales would vary according to the environmental contamination but also to many other factors including the sex, the diet and their nutritional status (Bengtson Nash et al, 2013;Dorneles et al, 2015;Waugh et al, 2012).…”

“…Biopsies were collected from a 7 m motor-boat, using a regular Barnett crossbow and aluminium darts as previously described (Dirtu et al, 2016;Lambertsen, 1987). A custom-made stainless steel tube tip (0.8 cm diameter, 2.5 cm length) was screwed at the end of the dart (Fig.…”

Habitat selection of two island-associated dolphin species from the south-west Indian Ocean

“…Increasing underwater noise from coastal planning, vessel traffic and dolphin-watching activities might also contribute to habitat degradation and lead to changes in habitat use, with possible consequences at the population level (Bejder et al, 2006;Lusseau and Bejder, 2007;New et al, 2015;Weilgart 2007). Furthermore, the near shore habitat of Indo-Pacific bottlenose dolphins in Reunion make them particularly vulnerable to anthropogenic pollution discharged by rivers or surface runoff compared to spinner dolphins (Dirtu et al,2016). Given the species' conservation status around the island-described as "endangered" (UICN France et al, 2013)-it is critical to preserve its coastal habitat as a whole to ensure the population's viability for the long term.…”

Environmental status and early warning value of the pollutant Semicarbazide in Jincheng and Sishili Bays, Shandong Peninsula, China

“…Establishment of the biological accumulation factor BCF was calculated as the ratio of the average analyte level in a selected tissue of an organism, expressed as mg/kg wet weight (C shellfish ), to the analyte concentration in water, expressed as mg/L (C seawater ) (Petoumenou et al, 2015;Gissi et al, 2015). The accumulation ability can be influenced by various biological and ecological factors, including geographic area, age, size, sex, tissue type, diet and temporal distribution (Bragigand et al, 2006;Dirtu et al, 2016). The Environmental Protection Agency of United State (USEPA) ruled that BCF should be determined in a mobile environment, and 28 days were needed to obtain reliable result.…”