Paper: Frogs and contaminated homes

Urban sprawl and the rising popularity of water-sensitive urban design of urban landscapes has led to a global surge in the number of wetlands constructed to collect and treat stormwater runoff in cities. However, contaminants, such as heavy metals and pesticides, in stormwater adversely affect the survival, growth, and reproduction of animals inhabiting these wetlands. A key question is whether wildlife can identify
and avoid highly polluted wetlands. We investigated whether pond-breeding frogs are attempting to breed in wetlands that affect the fitness of their offspring across 67 urban wetlands in Melbourne, Australia. Frog species richness and the concentration of contaminants (heavy metals and pesticides) were not significantly related, even in the most polluted wetlands. The proportion of fringing vegetation at a wetland had the greatest positive influence on the number of frog species present and the probability of occurrence of individual species, indicating that frogs inhabited wetlands with abundant vegetation, regardless of their pollution status. These wetlands contained contaminant levels similar to urban wetlands around the world at levels that reduce larval amphibian survival. These results are, thus, likely generalizable to other areas, suggesting that urban managers could inadvertently be creating ecological traps in countless cities. Wetlands are important tools for the management of urban stormwater runoff, but their construction should not facilitate declines in wetland-dependent urban wildlife.

Sievers, M., Hale, R., Swearer, S. E., and Parris, K. M. (2018). Frog occupancy of polluted wetlands in urban landscapes. Conservation Biology

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Paper: Will light fix the welfare issues associated with submerged farming?

Although surface-based cages dominate the marine finfish aquaculture industry, production issues that arise at the surface such as poor environmental conditions and the presence of parasites has spurred interest in submerging cages. However, submerged culture is not without its own issues; for example, the adverse effects on fish buoyancy levels can alter swimming speeds and cause tilted swimming at night time, leading to reduced growth rates and vertebral deformities. The use of continuous artificial lighting is common practice in surface-based salmon farming to inhibit maturation. Its  implementation can also increase swimming speeds at night, and, if used in submerged cages, may reduce the incidence of tilted swimming. Here we compared submerged
(below 10 m) and surface culture of Atlantic salmon Salmo salar for 42 d under continuous lighting. The use of continuous lightning during submergence of large (3.4 kg) Atlantic salmon increased swimming speeds, reduced tilted swimming, and spinal deformities did not arise. Submerged culture also decreased infestation by attached sea lice stages by 72%, from 4.4 to 1.2 lice per fish. However, specific growth rates of submerged fish were 30% lower than those of surface-reared fish. Developments in engineering and technologies that allow salmon to refill their swim bladders during submergence show promise in eliminating welfare and growth problems. Robust scientific experiments at full commercial scale of cages and operating systems that consider both production and welfare outcomes are critical to the successful development of submerged farming.

Sievers, M., Korsøen, Ø., Dempster, T., Fjelldal, P.G., Kristiansen, T., Folkedal, O. and Oppedal, F. (2018). Growth and welfare of submerged Atlantic salmon under continuous lighting. Aquaculture Environment Interactions. DOI: 10.3354/aei00289.

Job: GLOW (Global Wetlands program)

I have been fortunate to be appointed a research fellow (marine ecologist) working within the Global Wetlands program with the Australian Rivers Institute at Griffith University. I will be working with a highly-skilled and diverse group of people, led by Rod Connolly and Chris Brown. For more information, see:

http://www.rodconnolly.com

http://www.seascapemodels.org

https://www.griffith.edu.au/australian-rivers-institute

Paper: Correcting common misconceptions to inspire conservation action in urban environments

Despite repeated calls to action, proposals for urban conservation are often met with surprise or scepticism. It seems there remains a pervasive narrative in policy, practice and the public psyche that urban environments, while useful for engaging people with nature or providing ecosystem services, are of little conservation value. We argue that the tendency to overlook the conservation value of urban environments stems from misconceptions about the ability of native species to persist within cities and towns, and that this, in turn, hinders effective conservation action. Drawing on recent scientific evidence, we propose updated messages that can guide and inspire conservation action in urban environments: consider small spaces, recognize unconventional habitats, test creative solutions, and use science to minimize the impacts of future urban development.

Soanes, K., Sievers, M.,Chee, Y. E., Williams, S. G. N., Bhardwaj, M., Marshall, A. J., and Parris, K. M. (2018). Correcting common misconceptions to inspire conservation action in urban environments. Conservation Biology.

https://onlinelibrary.wiley.com/doi/abs/10.1111/cobi.13193

Paper: Contaminant mixtures interact to impair predator-avoidance behaviours and survival in a larval amphibian

Global declines in amphibian populations are a significant conservation concern, and environmental contamination is likely a contributing driver. Although direct toxicity may be partly responsible, contaminants are often present at sub-lethal concentrations in the wild. Behavioural end-points are becoming an increasingly useful method to estimate the impact of contaminants, particularly if the behavioural responses manifest to affect individual fitness (i.e. survival, growth, or reproduction). In the wild, most animals are affected by multiple stressors, and determining how these interact to affect behaviour is critical for understanding the ecological implications of contaminant exposure. Here, we examined the individual and interactive effect of the heavy metal copper and the insecticide imidacloprid on mortality rates and anti-predator behaviours of spotted marsh frog (Limnodynastes tasmaniensis) tadpoles. This common species frequently occupies and breeds in contaminated stormwater and agricultural wetlands, where copper and imidacloprid are often present. These contaminants may alter behaviour via physiological and neurological pathways, as well as affecting how tadpoles respond to chemical cues. Tadpoles suffered unexpectedly high mortality rates when exposed to imidacloprid concentrations well below published LC50 concentrations. Only unexposed tadpoles significantly avoided predator cues. Copper and imidacloprid reduced swimming speed and distance, and escape responses, while increasing erratic swimming. We observed an interactive effect of imidacloprid and copper on erratic swimming, but in general imidacloprid and copper did not act synergistically. Our results suggest that as contaminants enter waterbodies, tadpoles will suffer considerable direct mortality, reduced foraging capacity, and increased susceptibility to predation. Our results provide the first evidence of imidacloprid affecting amphibian behaviour, and highlight both the adverse effects of copper and imidacloprid, and the importance of exploring the effect of multiple contaminants simultaneously.

Behavioural responses recorded during the prodding period following 24-h exposure to copper, imidacloprid and the combination of both. Total distance travelled (a), average swimming speed (b), escape response (c; time taken to swim 25 mm following the first prod), and erratic swimming (d; the number of turns made greater than 90 degrees). Mean ± SE are shown, with points intentionally jittered.

 

Sievers, M., Hale, R., Swearer, S. E., and Parris, K. M. (2018). Contaminant mixtures interact to impair predator-avoidance behaviours and survival in a larval amphibian. Ecotoxicology and environmental Safety. DOI: 10.1016/j.ecoenv.2018.06.028.

https://authors.elsevier.com/a/1XDoQXad0OD6b

Paper: Stormwater wetlands can function as ecological traps for urban frogs

Around cities, natural wetlands are rapidly being destroyed and replaced with wetlands constructed to treat stormwater. Although the intended purpose of these wetlands is to manage urban stormwater, they are inhabited by wildlife that might be exposed to contaminants. These effects will be exacerbated if animals are unable to differentiate between stormwater treatment wetlands of varying quality and some function as “ecological traps” (i.e., habitats that animals prefer despite fitness being lower than in other habitats). To examine if urban stormwater wetlands can be ecological traps for frogs, we tested if survival, metamorphosis‐related measures, and predator avoidance behaviors of frogs differed within mesocosms that simulated stormwater wetlands with different contaminant levels, and paired this with a natural oviposition experiment to assess breeding‐site preferences. We provide the first empirical evidence that these wetlands can function as ecological traps for frogs. Tadpoles had lower survival and were less responsive to predator olfactory cues when raised in more polluted stormwater wetlands, but also reached metamorphosis earlier and at a larger size. A greater size at metamorphosis was likely a result of increased per capita food availability due to higher mortality combined with eutrophication, although other compensatory effects such as selective‐mortality removing smaller individuals from low‐quality mesocosms may also explain these results. Breeding adults laid comparable numbers of eggs across wetlands with high and low contaminant levels, indicating no avoidance of the former. Since stormwater treatment wetlands are often the only available aquatic habitat in urban landscapes we need to better understand how they perform as habitats to guide management decisions that mitigate their potential ecological costs. This may include improving wetland quality so that fitness is no longer compromised, preventing colonization by animals, altering the cues animals use when selecting habitats, pretreating contaminated water prior to release, providing off‐line wetlands nearby, or simply not constructing stormwater treatment wetlands in sensitive areas. Our study confirms the potential for urban stormwater treatment wetlands to function as ecological traps and highlights the need for greater awareness of their prevalence and impact at landscape scales.

Sievers, M., Parris, K. M., Swearer, S. E., and Hale, R. (2018). Stormwater wetlands can function as ecological traps for urban frogs. Ecological Applications. DOI: 10.1002/eap.1714.

Paper: Behaviour in the toolbox to outsmart parasites and improve fish welfare in aquaculture

Host behaviour can prevent infection and moderate the fitness of parasites. Antiparasite behaviours are prevalent in many host–parasite systems and occur over fine or broad scales. With global growth in aquaculture production and the associated proliferation of parasites in farming systems, the behaviour of the fish being farmed has seldom been investigated in relation to parasites. Epidemics and outbreaks of parasites are prevalent in most aquaculture systems, and behaviour could be harnessed in concert with current methods to prevent and control parasites and pathogens. However, this requires a systematic understanding of the behaviours of hosts, their capacity for resistance and their interaction with the environment and the parasite. Herein, we present evidence for how behaviour could be used in aquaculture, and discuss the possibility for behaviour to be used in aquaculture as (i) an indicator of welfare status, (ii) a tool in prevention or control and (iii) to maintain or improve welfare. We apply this framework to a case study of a highly problematic parasite, the salmon louse (Lepeophtheirus salmonis), on farmed Atlantic salmon (Salmo salar). We present the current state of the system, and the drawbacks of current control or prevention methods. We synergise current knowledge on host behaviours and show how behaviour could be incorporated into current and new approaches for prevention and control. Through this first evaluation of the possibilities behaviour presents in disease management, we aim to facilitate a shift in the current disease control paradigm from reactive‐based post‐infection control to pre‐infection prevention approaches.

Bui, S., Oppedal, F., Sievers, M., and Dempster, T. (2017). Behaviour in the toolbox to outsmart parasites and improve fish welfare in aquaculture. Reviews in Aquaculture. DOI: 10.1111/raq.12232.