Coen Hird

Ambient sunlight contains ultraviolet radiation (UVR), a potent genotoxic stressor, yet whether natural UVR induces DNA damage in free-living amphibian larvae remains unclear. We reared striped marsh frogs (Limnodynastes peronii) in outdoor mesocosms under low versus high ambient UVR treatments for 5 days and quantified cyclobutane pyrimidine dimers (CPDs) by ELISA. Measurable CPD levels were detected under both UVR exposures, providing direct evidence that natural sunlight induces DNA damage in amphibian larvae. Although mean CPD levels did not differ between treatments, quantile regression revealed higher levels of CPDs in both the lower (τ=0.05) and upper (τ=0.95) quantiles under high UVR. This pattern suggests that while average DNA damage levels were similar, subsets of individuals experienced disproportionately high CPD burdens under increased UVR. These results highlight the value of mesocosms as a tool to bridge laboratory and field contexts to evaluate the effects of UVR on aquatic fauna, particularly as UV environments shift with climate change.

Environmental sciences increasingly call for the inclusion of Indigenous knowledges. Yet this inclusion is frequently reduced to datasets, management tools or cultural insight, while systematically disavowing the sovereignty, law and epistemological authority that underpins Indigenous knowledge systems. Such extractive framings maintain the disciplinary coherence of science and secure its possessive claims to objectivity, even as they acknowledge pluralism. Indigenous scholars working within these constrained terrains are drawing on bodies of Indigenous theory such as Critical Indigenous Studies (CIS) to reconfigure the terms of knowledge production. This paper traces some of those reconfigurations. Guided by methodological commitments resonant with Indigenous Process Method, I conducted a review of 21 Indigenous‐authored environmental research papers. Rather than analysing their content, I followed the theoretical lineages they cited (68 foundational CIS texts) to illuminate conceptual forces shaping Indigenous environmental scholarship, and then returned to these initial papers to show how such commitments reverberate in environmental science practice. Five constellations emerged: Refusal and Resurgence; Indigenous Law and Governance; Relationality and Kincentric Ethics; Decolonial Environmental Futures and Justice; and Indigenous Methodologies. These constellations trouble hegemonic environmental science and expose its racialised epistemic architecture to assert that Indigenous knowledges cannot be adequately known by the logics of hegemonic science. What emerges is a challenge for environmental science disciplines to resist assimilation and refuse containment of Indigenous knowledges. If environmental sciences are to move beyond rhetorical inclusion, they must be willing to relinquish authority and relate otherwise. This review provokes that Indigenous knowledges do not need to be let in to science but they are here already and refuse to perform for institutional legitimacy. Read the free Plain Language Summary for this article on the Journal blog.

Loss of structural habitat complexity associated with habitat degradation in marine systems may expose early life stages of fishes to harsh environmental conditions. Specifically, loss of coral cover means less suitable refuge is available for some reef fish species to lay their eggs, exposing them to pervasive stressors such as ultraviolet radiation (UVR). Here, using laboratory experiments, we exposed embryos of the clownfish Amphiprion ocellaris for 2 h daily to two UVR levels reflective of their depth at settlement; high UVR (280 µW m−2), reflective of shallow depths, and low UVR (80 µW m−2), reflective of deeper depths over their embryonic period, and then measured changes in mass, yolk sac volume, DNA damage, and survival. Despite being exposed to ecologically relevant levels of UV radiation, there was 100% mortality before hatching and inflated yolk sacs in both high and low UVR-treated animals. Exposure to UVR also resulted in DNA damage, albeit only in high UVR treatments. It is evident from our results that the protection that the reef can offer from UVR is critical for the survival of clownfish. Our results also underscore the need for future work to consider this often-neglected stressor and the role of adequate refuge for the healthy development of early-life stages of reef organisms.

Ultraviolet radiation (UVR) has a range of strong effects on freshwater ecosystems, and changing UVR is implicated in global amphibian declines. The link between UVR and amphibian declines is not well understood, largely due to limited understanding of actual UVR exposure regimes in freshwater ecosystems. Logistical challenges in measuring aquatic UVR regimes in situ have impeded progress, including the design of cost-effective radiometric monitoring tools and the measurement of UVR at ecologically relevant scales. We designed novel underwater UVR loggers and deployed them in southeast Queensland creeks to log near-continuous underwater ultraviolet index (UVI) for 11 days across four sampling events within the peak amphibian breeding season. We compared these data with solar modelling, dosimetric and handheld radiometric techniques. The dataset (2616 h from 39 UV sensors) revealed a highly heterogenous daily UVR microenvironment that showed capacity for harmful UVI exposures at both sites. Traditional cumulative or periodic UVR monitoring approaches often missed these acute high UVR exposures. Fine scale UVR data logging was proven to be a cost-effective approach for monitoring the UVR microenvironment in freshwater systems. While no single method can be considered universally optimal, our results highlight the advantages of continuous in situ UV monitoring, particularly for capturing short-duration ultraviolet fluctuations relevant to aquatic organisms.

Ultraviolet radiation (UVR) is a pervasive factor that has shaped the evolution of life on Earth. Ambient levels of UVR mediate key biological functions but can also cause severe lethal and sublethal effects in a wide range of organisms. Furthermore, UVR is a powerful modulator of the effects of other environmental factors on organismal physiology, such as temperature, disease, toxicology and pH, among others. This is critically important in the context of global change, where understanding the effects of multiple stressors is a key challenge for experimental biologists. Ecological physiologists rarely afford UVR discussion or include UVR in experimental design, even when it is directly relevant to their study system. In this Commentary, we provide a guide for experimental biologists to better understand if, when, and how UVR can be integrated into experimental designs to improve the ecological realism of their experiments.

1) Ultraviolet radiation (UVR) has a range of strong effects on freshwater ecosystems, and changing UVR is implicated in global amphibian declines. The link between UVR and amphibian declines is not well understood, largely due to limited understanding of actual UVR exposure regimes in freshwater ecosystems. Logistical challenges in measuring aquatic UVR regimes in situ have impeded progress, including the design of cost-effective radiometric monitoring tools and the measurement of UVR at ecologically relevant scales. 2) We designed novel underwater UVR loggers and deployed them in southeast Queensland creeks to log near-continuous underwater UV Index (UVI) for 11 days across 4 sampling events within the peak amphibian breeding season. We compared these data with solar modelling, dosimetric and handheld radiometric techniques. 3) The dataset (2616 hours from 39 UV sensors) revealed a highly heterogenous daily UVR microenvironment that showed capacity for harmful UVI exposures at both sites. Traditional UVR monitoring techniques often missed these high UVR exposures. 4) Fine scale UVR data logging was proven to be a gold standard of monitoring the UVR microenvironment in freshwater systems. This is important for understanding the relevance of laboratory-based studies investigating how freshwater organisms respond to UVR, monitoring changing UVR in aquatic systems and ultimately predicting how aquatic systems will respond to changes in UVR levels associated with global climate change.

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Statistical analyses that physiologists use to test hypotheses predominantly centre on means, but the tail ends of the response distribution can behave quite differently and underpin important scientific phenomena. We demonstrate that quantile regression (QR) offers a way to bypass some limitations of least squares regression (LSR) by building a picture of independent variable effects across the whole distribution of a dependent variable. We used LSR and QR with simulated and real datasets. With simulated data, LSR showed no change in the mean response but missed significant effects in the tails of the distribution found using QR. With real data, LSR showed a significant change in the mean response but missed a lack of response in the upper quantiles which was biologically revealing. Together, this highlights that QR can help to ask and answer more questions about variation in nature.

Amphibian declines are sometimes correlated with increasing levels of ultraviolet radiation (UVR). While disease is often implicated in declines, environmental factors such as temperature and UVR play an important role in disease epidemiology. The mutagenic effects of UVR exposure on amphibians are worse at low temperatures. Amphibians from cold environments may be more susceptible to increasing UVR. However, larvae of some species demonstrate cold acclimation, reducing UV‐induced DNA damage at low temperatures. Understanding of the mechanisms underpinning this response is lacking. We reared Limnodynastes peronii larvae in cool (15°C) or warm (25°C) waters before acutely exposing them to 1.5 h of high intensity (80 µW cm⁻²) UVBR. We measured the color of larvae and mRNA levels of a DNA repair enzyme. We reared larvae at 25°C in black or white containers to elicit a skin color response, and then measured DNA damage levels in the skin and remaining carcass following UVBR exposure. Cold‐acclimated larvae were darker and displayed lower levels of DNA damage than warm‐acclimated larvae. There was no difference in CPD‐photolyase mRNA levels between cold‐ and warm‐acclimated larvae. Skin darkening in larvae did not reduce their accumulation of DNA damage following UVR exposure. Our results showed that skin darkening does not explain cold‐induced reductions in UV‐associated DNA damage in L. peronii larvae. Beneficial cold‐acclimation is more likely underpinned by increased CPD‐photolyase abundance and/or increased photolyase activity at low temperatures.

Many amphibian declines are correlated with increasing levels of ultraviolet radiation (UVR). While disease is often implicated in declines, environmental factors such as temperature and UVR play an important role in disease epidemiology. The mutagenic effects of UVR exposure on amphibians are worse at low temperatures. Amphibians from cold environments may be more susceptible to increasing UVR. However, larvae of some species demonstrate cold acclimation, reducing UV-induced DNA damage at low temperatures. Understanding of the mechanisms underpinning this response is lacking. We reared Limnodynastes peronii larvae in cool (15°C) or warm (25°C) waters before acutely exposing them to 1.5 h of high intensity (80 μW cm ^-2 ) UVBR. We measured the colour of larvae and mRNA levels of a DNA repair enzyme. We reared larvae at 25°C in black or white containers to elicit a skin colour response, and then measured DNA damage levels in the skin and remaining carcass following UVBR exposure. Cold acclimated larvae were darker and displayed lower levels of DNA damage than warm-acclimated larvae. There was no difference in CPD-photolyase mRNA levels between cold- and warm-acclimated larvae. Skin darkening in larvae did not reduce larval accumulation of DNA damage following UVR exposure. Our results showed that skin darkening alone does not explain cold-induced reductions in UV-associated DNA damage in L. peronii larvae. Beneficial cold-acclimation is more likely underpinned by increased CPD-photolyase abundance and/or increased photolyase activity at low temperatures. Research Highlights: L. peroniii larvae darken when exposed to cold temperatures Darker larvae were not protected from the effects of UV on DNA damage Cold acclimation of larvae when exposed to UV is likely driven by DNA repair enzymes not melanin