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

Abstract

a b s t r a c tHumpback whales, Megaptera novaeangliae, breeding off la Reunion Island (Indian Ocean) undergo largescale seasonal migrations between summer feeding grounds near Antarctica and their reproductive winter grounds in the Indian Ocean. The main scope of the current study was to investigate chemical exposure of humpback whales breeding in the Indian Ocean by providing the first published data on this breeding stock concerning persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), DDT and its metabolites (DDTs), chlordane compounds (CHLs), polybrominated diphenyl ethers (PBDEs), and methoxylated PBDEs (MeOPBDEs). Analyses of stable isotopes d 13 C and d 15 N in skin resulted in further insight in their feeding ecology, which was in agreement with a diet focused mainly on low trophic level prey species, such as krill from Antarctica. POPs were measured in all humpback whales in the order of HCB > DDTs > CHLs > HCHs > PCBs > PBDEs > MeO-BDEs. HCB (median: 24 ng g À1 lw) and DDTs (median: 7.7 ng g À1 lw) were the predominant compounds in all whale biopsies. Among DDT compounds, p,p 0 -DDE was the major organohalogenated pollutant, reflecting its long-term accumulation in humpback whales. Significantly lower concentrations of HCB and DDTs were found in females than in males (p < 0.001). Other compounds were similar between the two genders (p > 0.05). Differences in the HCB and DDTs suggested gender-specific transfer of some compounds to the offspring. POP concentrations were lower than previously reported results for humpback whales sampled near the Antarctic Peninsula, suggesting potential influence of their nutritional status and may indicate different exposures of the whales according to their feeding zones. Further investigations are required to assess exposure of southern humpback whales throughout their feeding zones.

Feeding ecology and population delineation of south‐eastern Atlantic and south‐western Indian Ocean humpback whales using stable isotope analysis

“…Although mean δ 13 C values seem to indicate these whales are feeding in the mid to high latitudes of the southern Atlantic Ocean, their low δ 15 N values seem to indicate feeding at a low trophic level, which is characteristic of a diet consisting of a majority of krill. Stable isotopic analysis of BSC4, which breeds off La Reunion Island in the western Indian Ocean, has revealed comparable δ 15 N values to this study (7.8 ± 0.4%; Das et al, ), indicating the substocks of BSC share a primarily krill‐based diet. These nitrogen and carbon diet values are similar to the average krill and copepod values ( δ 15 N = 3.6‰; δ 13 C = −25.6‰) in the areas of the southern Atlantic these whales are expected to feed in between the Polar Front and 55 ° S (Schmidt et al, ).…”

“…Stable isotope analysis, therefore, provides a corollary method of breeding stock delineation that can provide insights into whale behaviour approaching or on Southern Ocean feeding areas, where opportunities for observation and sampling are extremely limited. In the future, any study of the isotopic ecology of South Atlantic and south‐western Indian Ocean humpback whale populations will benefit from additional sampling of whale skins and sampling of potential prey species from feeding grounds, as well as combination with other emerging techniques, such as radiocarbon measurements (Eisenmann et al, ) and measurements of persistent organic pollutants (Das et al, ). Quantitatively determining ecological characteristics is a method that can also be widely applied to other humpback whale breeding stocks in the Southern Hemisphere to shed light on the complicated population dynamics of these animals that are an integral part of the marine ecosystem and are still recovering from past commercial whaling.…”

“…Marine mammals are ecosystem sentinels (Moore, ), and stable isotopic analysis of migratory whales is proving an effective means of gleaning information about the changing climate (Bengtson Nash et al, ; Seyboth et al, ) and human impacts on the ocean (Das et al, ). Owing to their elusive nature (migratory, often do not feed at the surface), specific dietary information of whales is usually obtained infrequently through surface observation or gut contents during necropsy when a dead whale is located.…”

Marine Ecosystem Assessment for the Southern Ocean: Birds and Marine Mammals in a Changing Climate

“…Persistent Organic Pollutants have been identified in Antarctic biota since the 1960s (George and Frear, 1966), including in top predators (Aono et al, 1997;Bustnes et al, 2006Bustnes et al, , 2007Waugh et al, 2014;Dorneles et al, 2015;Das et al, 2017). The POP profiles of Antarctic foraging species are typically distinct from northern hemisphere and lower southern latitude counterparts (Bengtson Nash, 2011), reflecting unique, pesticidedominated, hemispheric usage trends, as well as the long-range transport capabilities of individual chemicals (Bengtson Nash et al, 2010).…”

Hexachlorobenzene exerts genotoxic effects in a humpback whale cell line under stable exposure conditions

“…1,2 In the Southern hemisphere, hexachlorobenzene (HCB) dominates contaminant proles, [3][4][5][6][7] including those of humpback whales (Megaptera novaeangliae) feeding in Antarctica. [8][9][10] HCB exhibits typical legacy POP characteristics such as high stability (>6 years half-life in biota), hydrophobicity (log K ow ¼ 5.73, max. water solubility ¼ 5 mg L À1 ) 11,12 and volatility (H ¼ 35 Pa m 3 mol À1 ).…”