Survival and Contaminants in Imperiled and Common Riverine Fishes Assessed with an In Situ Bioassay Approach.

An in situ bioassay approach was used to determine whether aquatic contaminant stressors in a large Atlantic river ecosystem affect the survival of 3 fish species: the largemouth bass (Micropterus salmoides, juveniles), the fathead minnow (Pimephales promelas, adults), and the robust redhorse (Moxostoma robustum, juveniles). Hatchery-propagated fish were placed into cages to assess site-specific survival in the Yadkin-Pee Dee River of North Carolina and South Carolina, USA. Contaminants were measured in caged fish and sediment and surface water at each site. No apparent longitudinal trends in fish survival were detected, and contaminant concentrations varied among sites. Juvenile largemouth bass and robust redhorse did not survive past 13 and 23 d, with corresponding Kaplan-Meier median survival estimates of 9.7 and 12.1 d, respectively. Survival of adult fathead minnows deployed in cages alongside the juvenile fish averaged 43% at the end of the 28-d exposure, with a 22-d median survival estimate. The intersex condition, an indicator of endocrine disruption, was not observed in any adult fathead minnow. Contaminant accumulation in surviving fathead minnows was apparent, with highest accumulated concentrations of polychlorinated biphenyls (34.6-93.4 ng/g dry wt), organochlorine pesticides (19.9-66.1 ng/g dry wt), and mercury (0.17-0.63 µg/g dry wt). Contaminants and other water quality stressors in this river system appear to detrimentally impact juvenile fish survival, with presumed effects at the fish assemblage and community levels. Environ Toxicol Chem 2021;40:2206-2219. © 2021 SETAC.

Trophodynamics of Per- and Polyfluoroalkyl Substances in the Food Web of a Large Atlantic Slope River.

Per- and polyfluoroalkyl substances (PFASs) have attracted scientific and regulatory attention due to their persistence, bioaccumulative potential, toxicity, and global distribution. We determined the accumulation and trophic transfer of 14 PFASs (5 short-chain and 9 long-chain) within the food web of the Yadkin-Pee Dee River of North Carolina and South Carolina, US. Food web components and pathways were determined by stable isotope analyses of producers, consumers, and organic matter. Analyses of water, sediment, organic matter, and aquatic biota revealed that PFASs were prevalent in all food web compartments. Biofilm, an aggregation of bacteria, fungi, algae, and protozoans and a basal resource for the aquatic food web, showed high PFAS accumulation (in 10 of 14 compounds), particularly for perfluorooctanoic acid, with the greatest mean concentration of 463.73 ng/g. The food web compartment with the most detections and greatest concentrations of PFASs was aquatic insects; all 14 PFASs were detected in individual aquatic insect samples (range of 1.0 (range of 0.57 to 2.33); it is possible that an unmeasured PFBS precursor may be accumulating in biota and metabolizing to PFBS, leading to a higher than expected TMFs for this compound. Our findings demonstrate the prevalence of PFASs in a freshwater food web with potential implications for ecological and human health.

Relation of contaminants to fish intersex in riverine sport fishes.

Endocrine active compounds (EACs) are pollutants that have been recognized as an emerging and widespread threat to aquatic ecosystems globally. Intersex, the presence of female germ cells within a predominantly male gonad, is considered a biomarker of endocrine disruption caused by EACs. We measured a suite of EACs and assessed their associated impacts on fish intersex occurrence and severity in a large, regulated river system in North Carolina and South Carolina, USA. Our specific objective was to determine the relationship of contaminants in water, sediment, and fish tissue with the occurrence and severity of the intersex condition in wild, adult black bass (Micropterus), sunfish (Lepomis), and catfish (Ictaluridae) species at 11 sites located on the Yadkin-Pee Dee River. Polycyclic aromatic hydrocarbons (PAHs), ethinylestradiol (EE2), and heavy metals were the most prevalent contaminants that exceeded effect levels for the protection of aquatic organisms. Fish intersex condition was most frequently observed and most severe in black basses and was less frequently detected and less severe in sunfishes and catfishes. The occurrence of the intersex condition in fish showed site-related effects, rather than increasing longitudinal trends from upstream to downstream. Mean black bass and catfish tissue contaminant concentrations were higher than that of sunfish, likely because of the latter's lower trophic position in the food web. Principal component analysis identified waterborne PAHs as the most correlated environmental contaminant with intersex occurrence and severity in black bass and sunfish. As indicated by the intersex condition, EACs have adverse but often variable effects on the health of wild sport fishes in this river, likely due to fluctuations in EAC inputs and the dynamic nature of the riverine system. These findings enhance the understanding of the relationship between contaminants and fish health and provide information to guide ecologically comprehensive conservation and management decisions.

Food web contaminant dynamics of a large Atlantic Slope river: Implications for common and imperiled species.

Persistent and bioaccumulative contaminants often reach concentrations that threaten aquatic life by causing alterations in organism behavior and development, disruption of biological processes, reproductive abnormalities, and mortality. The objectives of this research were to determine the aquatic food web structure and trophic transfer and accumulation of contaminants within a riverine ecosystem and identify potential stressors to the health of an imperiled fish, the robust redhorse (Moxostoma robustum) and other species of conservation concern in a large Atlantic Slope (USA) river. Trophic position was determined for food web taxa by stable isotope analyses of representative producers, consumers, and organic matter of the Yadkin-Pee Dee River of North Carolina and South Carolina. Contaminant analyses were performed on water, sediment, organic matter, and aquatic biota to assess the prevalence and accumulation of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), current use pesticides (CUPs), polycyclic aromatic hydrocarbons (PAHs), and selected metals. Contaminants were prevalent in the environment and food web components of the river. PCBs were detected in 32% of biotic samples (mean 0.24µg/g dry weight [DW], range 0.01-3.33µg/g DW), and DDTs (legacy OCPs and metabolites) were detected in 90% (mean 0.014µg/g DW, range 0.0004-0.29µg/g DW). The trace metals manganese and cadmium exceeded published threshold effect concentrations in sediment (460 and 0.99µg/g DW, respectively). Mercury was detected in all food web samples exhibiting a mean of 0.61µg/g DW and range 0.006-2.35µg/g DW (mean 0.13µg/g wet weight [WW], range 0.001-0.6µg/g WW). Concentrations exceeded the 0.2µg/g WW aquatic life criterion for mercury in 38% of fish samples. Fish trophic magnification factors (TMFs; range 0.33-3.75) indicated that contaminant accumulation occurred from both water and dietary sources. The combination of analytical approaches applied here provides new insight into contaminant dynamics with conservation implications.

Seasonal physiological dynamics of maturing female southern flounder (Paralichthys lethostigma).

Physiological information is rarely used in descriptions of maturity for managed, wild fish species; however, the use of physiological data holds great promise to provide important detail on the complexities of oocyte development and maturity. Investigating southern flounder (Paralichthys lethostigma)-an overfished commercial and recreational fishery resource-we examined pre-spawn physiological changes in females to provide further detail of the maturation process. Given that adults of this species complete maturation and spawn in unknown offshore locations, information on pre-spawn physiological changes is particularly informative for both size- and age-based patterns of maturity. We evaluated seasonal and ontogenetic changes in hormone concentrations in blood plasma that are commonly associated with sexual maturation, in addition to quantifying and classifying lipid stored in liver tissue. We found a strong positive relationship between body weight and lipid content during all months, as well as evidence for mobilization of lipids among larger females in September and October, presumably for gonadal development. Throughout the sampling period, the lipid content of smaller individuals was dominated by structural lipids (as opposed to storage lipids). In contrast, larger individuals possessed greater amounts of storage lipids. This suggests that larger, putatively maturing individuals were accumulating storage lipids for later production of vitellogenin. Females sampled for blood sex steroids and ovarian histology showed different testosterone and estradiol concentrations between putatively maturing and immature fish, and temporal variation with peaks in October and November. Overall, emerging patterns of liver lipid content and composition and blood steroid concentrations describe a multi-month maturation process that is often managed one dimensionally over short time periods. Insights from this work will improve our understanding of the life history of southern flounder, with the potential for better understanding of the dynamics of offshore spawning migration and informing subsequent species management.