Search

The Deepwater Horizon oil spill highlighted the need to understand the effects of oil exposure on marine eggs and larvae. To determine how short-duration exposure impacts the survivability of early life stages of the bay anchovy, Anchoa mitchilli, embryos and larvae ≤ 3-days-post-hatch (dph) were exposed to high-energy water accommodated fractions of weathered crude oil for 2 or 6 h. Lethal and sublethal effects of short-duration oil exposure were observed, including crippling malformations and altered optimal swimming and foraging behavior of larvae without malformation. The probability of mortality for larvae exposed as embryos (37.37 and 77.31 µg L -1 total polycyclic aromatic hydrocarbons or 'TPAH'), assessed 48 h after exposure, increased from 0.06 to 0.15 (2 h) and 0.10-0.23 (6 h) relative to unoiled controls. When exposed as 1-dph larvae (8.80-37.37 µg L -1 TPAH) and assessed 24 h after exposure, the probabilities increased from 0.20 to 0.76 (2 h) and 0.28-0.99 (6 h). Among surviving larvae, probabilities of yolk-sac, finfold, notochord, and cranio-facial malformations increased with exposure concentration, duration, and time after exposure by up to 0.07 immediately following exposure of 1-dph larvae and 0.55 24 h after exposure. When assessed 48 h after exposure as embryos, the probability of larval malformation reached 0.43. First-feeding (3-dph) foraging behavior was altered immediately and 24 h after 2 h exposures (8.80-77.31 µg L -1 TPAH). Time spent in motion and swim speed increased with exposure concentration by up to 331% and 189%, respectively. The number of bursts min -1 increased by 293% immediately and 152% 24 h after exposure. Burst distance decreased by 201%. Pause duration and burst speed decreased by 391% and 250% immediately and 124% and 109% 24 h after exposure. No effects were found for burst duration or tortuosity. Our results suggest potential cascading effects on fitness and trophic interactions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The BP-contracted Deepwater Horizon Macondo well blowout occurred on 20 April 2010 and lasted nearly three months. The well released millions of barrels of crude oil into the northern Gulf of Mexico, causing extensive impacts on pelagic, benthic, and estuarine fish species. The bay anchovy (Anchoa mitchilli) is an important zooplanktivore in the Gulf, serving as an ecological link between lower trophic levels and pelagic predatory fish species. Bay anchovy spawn from May through November in shallow inshore and estuarine waters throughout the Gulf. Because their buoyant embryos are a dominant part of the inshore ichthyoplankton throughout the summer, it is likely bay anchovy embryos encountered oil in coastal estuaries during the summer and fall of 2010. Bay anchovy embryos were exposed to a range of concentrations of two field-collected Deepwater Horizon oils as high-energy and low-energy water accommodated fractions (HEWAFs and LEWAFs, respectively) for 48h. The median lethal concentrations (LC 50 ) were lower in exposures with the more weathered oil (HEWAF, 1.48µg/L TPAH50; LEWAF, 1.58µg/L TPAH50) compared to the less weathered oil (HEWAF, 3.87µg/L TPAH50; LEWAF, 4.28µg/L TPAH50). To measure delayed mortality and life stage sensitivity between embryos and larvae, an additional 24h acute HEWAF exposure using the more weathered oil was run followed by a 24h grow-out period. Here the LC 50 was 9.71µg/L TPAH50 after the grow-out phase, suggesting a toxic effect of oil at the embryonic or hatching stage. We also found that exposures prepared with the more weathered Slick B oil produced lower LC 50 values compared to the exposures prepared with Slick A oil. Our results demonstrate that even relatively acute environmental exposure times can have a detrimental effect on bay anchovy embryos., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Bay anchovy (Anchoa mitchilli) is an ecologically important zooplanktivorous fish inhabiting estuaries of the Gulf of Mexico and eastern North America from Maine to Florida. Because they have a protracted spawning season (spring through fall) and are abundant at all life stages in coastal estuaries, their eggs and larvae likely encountered oil that reached the coast during the Deepwater Horizon oil spill. We compared responses to oil exposure at different life stages and at lethal and sublethal conditions using acute, 24h exposures. In a series of experiments, bay anchovy larvae were exposed to high energy water accommodated fractions (HEWAF) and chemically-enhanced WAF (CEWAF) at two stages of larval development (5 and 21 days post hatch, dph). HEWAF oil exposures induced significantly greater life stage dependent sensitivity at 5 dph than at 21 dph but chemically dispersed (CEWAF) exposure mortality was more variable and LC 50s were not significantly different between 5 and 21dph larvae. Acute exposure to two low-level concentrations of CEWAF did not result in significant mortality over 24h, but resulted in a 25-77% reduction in larval survival and a 12-34% reduction in weight specific growth after six days of post-exposure growth following the initial 24h exposure. These results show that younger (5 dph) bay anchovy larvae are more vulnerable to acute oil exposure than older (21 dph) larvae, and that acute responses do not accurately reflect potential population level mortality and impacts to growth and development., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Our goal was to develop a standardized approach for sperm vitrification of marine fishes that can be applied generally in aquatic species. The objectives were to: 1) estimate acute toxicity of cryoprotectants over a range of concentrations; 2) evaluate the properties of vitrification solutions (VS); 3) evaluate different thawing solutions, and 4) evaluate sperm quality after thawing by examination of motility and membrane integrity. Sperm were collected from red snapper ( Lutjanus campechanus ), spotted seatrout ( Cynoscion nebulosus ), and red drum ( Sciaenops ocellatus ). A total of 29 combinations of cryoprotectants were evaluated for toxicity and glass formation. Samples were loaded onto 10-µL polystyrene loops and plunged into liquid nitrogen. There was a significant difference ( P < 0.05) in post-thaw motility among VS and among species when using the same VS. The sperm in VS of 15% DMSO + 15% ethylene glycol + 10% glycerol + 1% X-1000™ + 1% Z-1000™ had an average post-thaw motility of 58% and membrane integrity of 19% for spotted seatrout, 38% and 9% for red snapper, and 30% and 19% for red drum. Adaptations by marine fish to high osmotic pressures could explain the survival in the high cryoprotectant concentrations. Vitrification offers an alternative to conventional cryopreservation.

Feeding experiments were performed to investigate mercury (Hg) isotope fractionation during trophic transfer and internal distribution of total Hg (THg) in marine fish on exposure to natural seafood. Young-of-the-year amberjack (Seriola dumerili) were fed with either blackfin tuna (Thunnus atlanticus; 2647 ng/g THg) or brown shrimp (Farfantepenaeus aztecus; 25.1 ng/g THg) for 80 d or 50 d, respectively, and dissected for muscle, liver, kidney, brain, and blood. After 30 d of tuna consumption, Hg isotopes (δ(202) Hg and Δ(199)Hg) of the amberjack organs shifted to the tuna value (δ(202)Hg = 0.55‰, Δ(199)Hg = 1.54‰,), demonstrating the absence of Hg isotope fractionation. When amberjack were fed a shrimp diet, there was an initial mixing of the amberjack organs toward the shrimp value (δ(202)Hg = -0.48‰, Δ(199)Hg = 0.32‰), followed by a cessation of further shifts in Δ(199)Hg and a small shift in δ(202)Hg. The failure of Δ(199)Hg to reach the shrimp value can be attributed to a reduction in Hg bioaccumulation from shrimp resulting from feeding inhibition and the δ(202)Hg shift can be attributed to a small internal fractionation during excretion. Given that the feeding rate and Hg concentration of the diet can influence internal Hg isotope distribution, these parameters must be considered in biosentinel fish studies., (© 2013 SETAC.)

Background: Methylmercury (MeHg) exposure assessments among average fish consumers in the United States may underestimate exposures among U.S. subpopulations with high intakes of regionally specific fish., Objectives: We examined relationships among fish consumption, estimated mercury (Hg) intake, and measured Hg exposure within one such potentially highly exposed group, recreational anglers in the state of Louisiana, USA., Methods: We surveyed 534 anglers in 2006 using interviews at boat launches and fishing tournaments combined with an Internet-based survey method. Hair samples from 402 of these anglers were collected and analyzed for total Hg. Questionnaires provided information on species-specific fish consumption during the 3 months before the survey., Results: Anglers' median hair Hg concentration was 0.81 µg/g (n = 398; range, 0.02-10.7 µg/g); 40% of participants had levels >1 µg/g, which approximately corresponds to the U.S. Environmental Protection Agency's reference dose. Fish consumption and Hg intake were significantly positively associated with hair Hg. Participants reported consuming nearly 80 different fish types, many of which are specific to the region. Unlike the general U.S. population, which acquires most of its Hg from commercial seafood sources, approximately 64% of participants' fish meals and 74% of their estimated Hg intake came from recreationally caught seafood., Conclusions: Study participants had relatively elevated hair Hg concentrations and reported consumption of a wide variety of fish, particularly locally caught fish. This group represents a highly exposed subpopulation with an exposure profile that differs from fish consumers in other regions of the United States, suggesting a need for more regionally specific exposure estimates and public health advisories.

We combined N, C, and Hg stable isotope measurements to identify the most important factors that influence MeHg accumulation in fish from the northern Gulf of Mexico (nGOM), and to determine if coastal species residing in the Mississippi River (MR) plume and migratory oceanic species derive their MeHg from the same, or different, sources. In six coastal species and two oceanic species (blackfin and yellowfin tuna), trophic position as measured by delta(15)N explained most of the variance in log[MeHg] (r(2) approximately 0.8), but coastal species and tuna fell along distinct, nearly parallel lines with significantly different intercepts. The tuna also had significantly higher delta(202)Hg (0.2-0.5 per thousand) and Delta(201)Hg ( approximately 1.5 per thousand) than the coastal fish (delta(202)Hg = 0 to -1.0 per thousand; Delta(201)Hg approximately 0.4 per thousand). The observations can be best explained by largely disconnected food webs rooted in different baseline delta(15)N signatures (MR-plume vs oceanic) and isotopically distinct MeHg sources, with oceanic MeHg having undergone substantial photodegradation ( approximately 50%) before entering the base of the food web. Given the MR's large, productive footprint in the nGOM and the potential for exporting prey and MeHg to the adjacent oligotrophic GOM, the disconnected food webs and different MeHg sources are consistent with recent evidence in other systems of important oceanic MeHg sources.