Is Exposure to Macondo Oil Reflected in the Otolith Chemistry of Marsh-Resident Fish?

Emerging Chemical Methods for Petroleum and Petroleum-Derived Dissolved Organic Matter Following the Deepwater Horizon Oil Spill

Despite the fact that oil chemistry and oils spills have been studied for many years, there are still emerging techniques and unknown processes to be explored. The 2010 Deepwater Horizon oil spill in the Gulf of Mexico resulted in a revival of oil spill research across a wide range of fields. These studies provided many new insights, but unanswered questions remain. Over 1,000 journal articles related to the Deepwater Horizon spill are indexed by the Chemical Abstract Service. Numerous ecological, human health, and organismal studies were published. Analytical tools applied to the spill include mass spectrometry, chromatography, and optical spectroscopy. Owing to the large scale of studies, this review focuses on three emerging areas that have been explored but remain underutilized in oil spill characterization: excitation-emission matrix spectroscopy, black carbon analysis, and trace metal analysis using inductively coupled plasma mass spectrometry.

Alterations in energy metabolism, total protein, uric and nucleic acids in African sharptooth catfish (Clarias gariepinus Burchell) exposed to crude oil and fractions

Water contamination by crude oil is a growing challenge and little is known about the probabilistic and non-probabilistic ecosystem and species consequences. Therefore, research aimed at understanding species survival strategy in crude oil-contaminated environments with focus on cellular metabolic alterations and dynamics is vital. This study assessed the alterations in lactate dehydrogenase (LDH), glucose (GLU), glucose-6-phosphate dehydrogenase (G-6-PDH), total protein (TP), uric and nucleic acids (UA, RNA, and DNA) in the liver, heart, kidney, blood supernatants, and muscle homogenates of African sharptooth catfish ([ASC] Clarias gariepinus) exposed to varying bonny-light crude oil concentrations to understand the underlying cause of their delayed development as well as potential health and wellbeing. Three concentrations (20, 50, and 100 mg/L) of diluted whole bonny-light crude oil (DWC), water-soluble (WSF), and water-insoluble (WIF) fractions of bonny-light crude oil were used to grow ASC for 9 weeks at room temperature. Biochemical assessments revealed significant (at p < 0.05) elevations in heart LDH (48.57 ± 4.67 to 3011.34 ± 4.67 U/L) and blood G-6-PDH activities (54.86 ± 0.00 to 128 ± 18.29 mU/mL), GLU (0.22 ± 0.01 to 0.77 ± 0.01 mg/dL), TP (5.15 ± 0.14 to 22.33 ± 0.21 g/L), UA (0.29 ± 0.05 to 10.05 ± 0.27 mg/dL), as well as liver DNA (0.38 ± 0.02 to 2.33 ± 0.09 μg/mL) and RNA (12.52 ± 0.05 to 30.44 ± 0.02 μg/mL) levels for laboratory-grown ASC in DWC, WSF, WIF, and oil-impacted Ubeji river collected ASC relative to the control. Due to greater levels of cellular metabolic alterations in oil-impacted Ubeji River collected ASC, it is evident that bonny-light contamination levels in the river is greater than 100 mg/L. In conclusion, bonny-light crude oil is toxic to ASC and induces stress response. The ecological changes caused by bonny-light crude oil contamination may ultimately affect niche functioning and the development of organs in ASC.

Past and Contemporaneous Otolith Fingerprints Reveal Potential Anthropogenic Interferences and Allows Refinement of the Population Structure of Isopisthus parvipinnis in the South Brazil Bight

Simple Summary

Otolith geochemical signatures were important tools used to investigate the population of commercially exploited fish species. Historical and contemporary otolith samples of Isopisthus parvipinnis, Bigtooth corvina, an economically and ecologically important Brazilian fish species, collected in five subareas [São Paulo: North—NSP, Center—CSP and South—SSP; Paraná (PR) and Santa Catarina (SC)] of the shallow waters off the coast of the South Brazil Bight were used in this study. Univariate and multivariate statistical analyses showed spatial differences in otolith chemical composition over the years, suggesting that long-term temporal variability in oceanographic conditions, anthropogenic influence, and climate change on this coastal ecosystem influenced the geochemical signatures. Moreover, these results also confirm that I. parvipinnis is not a single and homogeneous fish stock in this geographic area, supporting the existence of a metapopulation structure scenario and corroborating previous studies that used alternative, complementary phenotypic tags.

Abstract

In this study, otolith geochemical signatures (Element:Ca ratios) were used to investigate the long-term spatial shifts of the population structure of Isopisthus parvipinnis, Bigtooth corvina, an economically and ecologically important Brazilian fish species. Two-hundred and ninety-seven juvenile individuals from historical (1975) and contemporary (2018/2019) samples were collected in five subareas [São Paulo: North—NSP, Center—CSP and South—SSP; Paraná (PR) and Santa Catarina (SC)] of the shallow waters off the coast of the South Brazil Bight were analyzed. The main informative single elements were Co:Ca, Cu:Ca, Li:Ca, Mg:Ca, Mn:Ca, Ni:Ca, Na:Ca, and Rb:Ca. Multivariate analysis showed spatial differences in otolith chemical composition over the years. Samples from 1975 presented an overall low reclassification rate (58%), suggesting the existence of two population units: (1) SP + PR; and (2) SC. However, samples from 2018/2019 discriminated four distinct population units with a good overall reclassification (80%): (1) NSP; (2) CSP; (3) SSP + PR; and (4) SC. This spatial differentiation on the geochemical signatures probably reflects the effects of long-term temporal variability in oceanographic conditions, anthropogenic influence, and climate change on this coastal ecosystem. The data also corroborate and refines the population structure scenario of I. parvipinnis recently described using complementary phenotypic tags.

Multivariate analysis of otolith microchemistry can discriminate the source of oil contamination in exposed fish

The uptake of metals into the aragonite lattice of the fish otolith (ear-bone) has been used for decades as a historical record of exposure to metals in polluted environments. The relative abundance of two metals in particular, Ni and V, are used in forensic chemical analysis of crude oils to assist in confirming its origin. In this study we investigate the potential for metal accumulation in otoliths to act as a biomarker of exposure to crude oil. Using a 33-day static-renewal laboratory trial design, 56 juvenile Lates calcarifer (commonly known as Asian seabass or barramundi) were fed diets enriched with V (20 mg/kg), Ni (500 mg/kg), Fe (500 mg/kg), and two crude oils with distinctly different metals profiles: a heavy fuel oil (1% w/w) and a typical Australian medium crude (1% w/w). Fish exposed to crude oils showed Ba and Al retained in otoliths in a dose-dependent manner, but fish fed V-, Ni- and Fe-enriched diets showed no metal increase in otoliths, indicating that V, Ni and Fe are not incorporated into the otolith of L. calcarifer via dietary exposure. For crude oils, incorporation into otolith for many metals is likely limited due to porphyrin casing reducing their bioavailability. Principal components analysis (PCA) and subsequent linear discriminatory analysis (LDA) of selected otolith metals demonstrated that, even despite large variability in the metal abundances detected in otolith between individuals within the test groups (cv = 1.00), it is possible to discriminate between fish exposed to different crude oils using multivariate analysis of their otolith microchemistry.

Genotyping-in-Thousands by sequencing of archival fish scales reveals maintenance of genetic variation following a severe demographic contraction in kokanee salmon

Historical DNA analysis of archival samples has added new dimensions to population genetic studies, enabling spatiotemporal approaches for reconstructing population history and informing conservation management. Here we tested the efficacy of Genotyping-in-Thousands by sequencing (GT-seq) for collecting targeted single nucleotide polymorphism genotypic data from archival scale samples, and applied this approach to a study of kokanee salmon (Oncorhynchus nerka) in Kluane National Park and Reserve (KNPR; Yukon, Canada) that underwent a severe 12-year population decline followed by a rapid rebound. We genotyped archival scales sampled pre-crash and contemporary fin clips collected post-crash, revealing high coverage (> 90% average genotyping across all individuals) and low genotyping error (< 0.01% within-libraries, 0.60% among-libraries) despite the relatively poor quality of recovered DNA. We observed slight decreases in expected heterozygosity, allelic diversity, and effective population size post-crash, but none were significant, suggesting genetic diversity was retained despite the severe demographic contraction. Genotypic data also revealed the genetic distinctiveness of a now extirpated population just outside of KNPR, revealing biodiversity loss at the northern edge of the species distribution. More broadly, we demonstrated GT-seq as a valuable tool for collecting genome-wide data from archival samples to address basic questions in ecology and evolution, and inform applied research in wildlife conservation and fisheries management.

Spatial assessment of major and trace element concentrations from Lower Athabasca Region Trout-perch (Percopsis omiscomaycus) otoliths

The Lower Athabasca Region (LAR) is home to the largest bitumen deposit in Alberta, and has seen industrial development related to the extraction and processing of bituminous sands since the late 1960s. Along with industrial and economic growth related to oil sands development, environmental concerns have increased in recent decades, including those about potential effects on fish. We measured major and trace element concentrations in Trout-perch otoliths from the Athabasca and Clearwater Rivers in the LAR, to illustrate spatial variations and identify possible industrial impacts. Both laser ablation ICP-MS and solution-based ICP-MS methods were employed. Of the trace elements enriched in bitumen (V, Ni, Mo and Re), only Ni and Re were above the limits of detection using at least one of the methods. The only significant differences in element concentrations between upstream and downstream locations were found for Li, Cu, and Pb which were more abundant upstream of industry. For comparison and additional perspective, otoliths from the same fish species, but taken from the Batchawana River in northern Ontario, were also examined. The fish from Alberta yielded greater concentrations of Ba, Bi, Li, Mg, Na, Re, Sc, Th and Y, but the Ontario fish had more Cr, Rb and Tl, likely because of differences in geology.