Persistent Organic Pollutants and Mercury in Genetically Identified Inner Estuary Bottlenose Dolphin (Tursiops truncatus) Residents of the Guayaquil Gulf, Ecuador: Ecotoxicological Science in Support of Pollutant Management and Cetacean Conservation

Abstract

The bottlenose dolphin is one of the most common cetaceans found in the coastal waters, estuaries, and mangroves of Ecuador. However, its population size is gradually declining in the Gulf of Guayaquil, and anthropogenic factors including habitat degradation, uncontrolled dolphin watching, dredging activities, increasing maritime traffic, underwater noise, bycatch, and marine pollution have been implicated in their decline. Very little is known about contamination by persistent organic pollutants (POPs) and mercury in bottlenose dolphins from the Pacific coast of South America. To address this research gap, the first assessment of total mercury (THg) and POPs, including polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs), in free-ranging bottlenose dolphins in mangroves (El Morro Mangrove Wildlife Refuge) of the Gulf of Guayaquil, was conducted in Ecuador in 2018. Dolphin samples (i.e., skin and blubber; n = 9), were obtained using dart biopsy field methods for contaminant analysis. POP concentrations ranged from 0.56 to 13.0 mg/kg in lipid weight, while THg ranged from 1.92 to 3.63 mg/kg in dry weight. The predominant POPs were OCPs (50% of POP), followed by PCBs (46%) and PBDEs (6.0%); particularly, p,p-DDE, the main DDT metabolite and a potent antiandrogenic, accounting for 42% of POP, ranging from 0.12 to ∼7.0 mg/kg lw, followed by PCB 153 (8.0%) and PCB 180 (5.0%). PBDE 47 accounted for 2.0% of POP. While the POP concentrations are lower than those found in dolphins from many other regions

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

“…The general profile is similar to other delphinid species using and/or residing on the Brazilian coast, such as Guiana dolphins ( Sotalia guianensis ), bottlenose dolphins, and killer whales ,, and common dolphins ( Delphinus delphis ) from Argentina, but differs from Fraser’s dolphins ( Lagenodelphis hosei ) also from Argentina and bottlenose dolphins from Ecuador, which presented higher contribution of DDTs rather than PCBs. Furthermore, POP concentrations found in rough-toothed dolphins were relatively higher than other delphinid species from South America. ,, …”

“…Furthermore, POP concentrations found in rough-toothed dolphins were relatively higher than other delphinid species from South America. 21,59,62 Collectively, the profile and concentrations magnitude indicate a predominance of industrial over agricultural activities, 63 confirming the study area as an urban and industrialized region and as a hotspot for persistent organochlorine contaminants. This pattern also upholds the coastal behavior of rough-toothed dolphins in the SWAO.…”

“…The PCB profile was dominated by hexa-, hepta-, and pentachlorinated congeners in all three populations, as observed in other marine mammals from the southern hemisphere, reflecting the residual profile of the commercial mixtures imported since Brazil was not a producer of PCBs. 21,59 The DDT profile was dominated by p.p′-DDE, indicating a historical contamination by DDT in the SWAO. 60 The DDT contribution in the S population stands out in comparison to the other ecological populations of rough-toothed dolphins, and it is probably related to the historical agricultural activity in Paranástate 61 as it may also suffer from the influence from Saõ Paulo state.…”

Emerging Contaminants and New POPs (PFAS and HBCDD) in Endangered Southern Resident and Bigg’s (Transient) Killer Whales (Orcinus orca): In Utero Maternal Transfer and Pollution Management Implications

“…Contaminant concentrations were blank-corrected by subtracting the concentration in the associated method blank [method detection limit (MDL)] for each analyte from the sample concentration to account for background contamination throughout laboratory analyses (see Table S1 for MDL values). Samples with no contaminant detection were substituted with either 1/2 half of the blank concentration ([blank]/2) or blank reporting limit (RL) divided by the square-root of two (RL/√2) if no blank contaminant concentration was detected. ,, These adjusted samples and those analytes with contaminant concentrations below the associated blank were not blank corrected. Contaminants that were equal in concentration to the blank sample were replaced with values derived from the [blank]/2 calculation.…”

Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador

“…Emissions from human-made sources and industrialization in the Gulf of Guayaquil, for example, may explain THg concentrations on the order of 2.76 and 4.90 mg/kg dry weight observed in estuarine sediments and mangrove mussels (Mytella strigata), respectively (Calle et al, 2018). Comparably, Hg contamination (i.e., concentrations ranging from 1.92 to 3.63 mg/kg dry wt) in skin samples of bottlenose dolphins (Tursiops truncatus) from the Guayaquil Gulf was also recently reported (Alava et al, 2020).…”