Terra (aqua) incognita : knowledge gaps in global ecotoxicology

The peer-reviewed toxicological literature contains twice as many studies pertaining to the River Thames (United Kingdom) than to the Congo River (Central Africa), despite the latter's watershed being roughly 250 times larger and sustaining a 5-fold greater human population (Web of Science database). Protecting such underresearched natural resources from chemical contamination requires local research to fill knowledge gaps, attention to regional expertise, and incorporation of local communities into the decision-making process. The support of regional, collaborative networks may be the most important of these because they will be most responsive to emerging ecotoxicological concerns as they develop.This article also appears in: Contaminants of Emerging Concern: Addressing Data Gaps with a Focus on Developing Countrieshttps://setac.onlinelibrary.wiley.com/journal/15528618hj2022Chemistr

Data from: Local adaptation despite high gene flow in the waterfall-climbing Hawaiian goby, Sicyopterus stimpsoni.

Environmental heterogeneity can promote the emergence of locally adapted phenotypes among subpopulations of a species, whereas gene flow can result in phenotypic and genotypic homogenization. For organisms like amphidromous fishes that change habitats during their life history, the balance between selection and migration can shift through ontogeny, making the likelihood of local adaptation difficult to predict. In Hawaiian waterfall-climbing gobies, it has been hypothesized that larval mixing during oceanic dispersal counters local adaptation to contrasting topographic features of streams, like slope gradient, that can select for predator avoidance or climbing ability in juvenile recruits. To test this hypothesis, we used morphological traits and neutral genetic markers to compare phenotypic and genotypic distributions in recruiting juveniles and adult subpopulations of the waterfall-climbing amphidromous goby, Sicyopterus stimpsoni, from the islands of Hawai\u27i and Kaua\u27i. We found that body shape is significantly different between adult subpopulations from streams with contrasting slopes and that trait divergence in recruiting juveniles tracked stream topography more so than morphological measures of adult subpopulation differentiation. Although no evidence of population genetic differentiation was observed among adult subpopulations, we observed low but significant levels of spatially and temporally variable genetic differentiation among juvenile cohorts, which correlated with morphological divergence. Such a pattern of genetic differentiation is consistent with chaotic genetic patchiness arising from variable sources of recruits to different streams. Thus, at least in S. stimpsoni, the combination of variation in settlement cohorts in space and time coupled with strong postsettlement selection on juveniles as they migrate upstream to adult habitats provides the opportunity for morphological adaptation to local stream environments despite high gene flow

Serum estrogenicity and biological responses in African catfish raised in wastewater ponds in Ghana

Reuse of wastewater for aquaculture improves the efficient use of water and promotes sustainability but the potential effects of endocrine disrupting compounds including estrogens in wastewater is an emerging challenge that needs to be addressed. We examined the biological effects of wastewater-borne estrogens on African catfish (Clarias gariepinus) raised in a wastewater stabilization pond (WSP) of a functioning municipal wastewater treatment plant, a wastewater polishing pond (WWP) of a dysfunctional treatment plant, and a reference pond (RP) unimpacted by wastewater, located in Ghana. Measurements of estrogen concentrations in pond water by liquid chromatography/tandem mass spectrometry showed mean 17 s-estradiol concentrations were higher in the wastewater ponds (WWP, 6.6 ng/L ? 2.7 ng/L; WSP, 4.9 ng/L ? 1.0) than the reference (RP, 3.4 ? 1.1 ng/L). Estrone concentrations were found to be highest in the WSP (7.8 ng/L ? 1.7) and lowest in the WWP (2.2 ng/L ? 2.4) with the RP intermediate (4.7 ? 5.0). Fish serum estrogenicity assayed by ESCREEN was significantly higher in female vs. male catfish in the RP and WSP but not in the WWP (p = 0.05). Histological examination of liver and gonad tissue showed no apparent signs of intersex or pathology in any ponds. The similarities in various measures of body indices between fish of this study and African catfish from other freshwater systems suggest that aquaculture may be a suitable reuse option for treated municipal wastewater

Challenges to wastewater aquaculture: a case study of traditional and emerging contaminant concentrations in African catfish [Abstract only]

Municipal wastewater-fed aquaculture promotes efficient water use, however, the potential effects of wastewater-borne traditional and emerging contaminants on fish and human health are potential challenges. The pathogen and heavy metal accumulation in fish tissue and serum estrogenicity and biological effects of wastewater-borne estrogens were assessed in African catfish (Clarias gariepinus) raised in a wastewater stabilization ponds (WSP) of a functioning municipal wastewater treatment plant and reference ponds (RP) unimpacted by wastewater, located in Ghana (West Africa). Preliminary results showed that significantly higher levels (2-3 log units) of pathogen (E. coli) contamination were detected in the gut and skin of fish from the WSP than the reference ponds (p = 0.05). Furthermore, the levels of heavy metals found in fish tissue were below the expected daily nutritional requirement (1-2 mg) for humans and poses insignificant toxicological risks. The mean estrogen concentrations were higher in the wastewater ponds than the reference and fish serum assayed by E-SCREEN showed significantly higher estrogenicity in female vs. male catfish in the RP compared to the WSP (p = 0.05). Histological examination of liver and gonad tissues showed no apparent signs of intersex or pathology. These studies showed that catfish cultivated at the study sites were safe for human consumption, however, precautions such as depuration and effective processing methods including grilling and smoking prior to consumption are recommended to reduce pathogen loads. In terms of fish health, biological metrics in this study suggest that aquacultural use of adequately treated municipal wastewater had minimal estrogenic effects on African catfish. Investigation of other growth and reproduction-modulating compounds (e.g. androgens) are needed

Ontogenetic change in novel functions: waterfall climbing in adult Hawaiian gobiid fishes

Juveniles from three species of Hawaiian gobiid fishes climb waterfalls as part of an amphidromous life cycle, allowing them to re-penetrate adult upstream habitats after being swept out to the ocean upon hatching. The importance of climbing for juvenile stream gobies is well established, but adult fish in upstream island habitats also face potential downstream displacement by periodic disturbances. Thus, retention of climbing ability could be advantageous for adult stream gobies. Climbing performance might be expected to decline among adults, however, due to the tendency for mass-specific muscular power production to decrease with body size, and a lack of positively allometric growth among structures like the pelvic sucker that support body weight against gravity. To evaluate changes in waterfall-climbing ability with body size in Hawaiian stream gobies, we compared climbing performance and kinematics between adults and juveniles from three species: Awaous guamensis, Sicyopterus stimpsoni and Lentipes concolor. For species in which juveniles climbed using ‘powerbursts’ of axial undulation, adult performance and kinematics showed marked changes: adult A. guamensis failed to climb, and adult L. concolor used multiple pectoral fin adductions to crutch up surfaces at slow speeds, rather than rapid powerbursts. Adult S. stimpsoni, like juveniles, still used oral and pelvic suckers to ‘inch’ up surfaces and climbed at speeds comparable to those of juveniles. However, unlike juveniles, adult S. stimpsoni also add pectoral fin crutching to every climbing cycle. Thus, although powerburst species appear to be particularly susceptible to size-related declines in waterfall-climbing performance, the addition of compensatory mechanisms pre- vents the loss of this novel function in some species