School of BioSciences, The University of Melbourne, Parkville, Victoria, 3010, Australia.
School of Ecosystem and Forest Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Ecol Appl. 2018 Jun;28(4):1106-1115. doi: 10.1002/eap.1714. Epub 2018 Apr 26.
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.
在城市周围，天然湿地正在迅速被破坏，并被改造成用于处理雨水的湿地。虽然这些湿地的目的是管理城市雨水，但它们却有野生动物栖息，这些野生动物可能会接触到污染物。如果动物无法区分不同质量的雨水处理湿地，那么这些影响将会加剧，有些湿地可能会成为“生态陷阱”（即动物喜欢的栖息地，尽管适应性比其他栖息地低）。为了研究城市雨水湿地是否可能成为青蛙的生态陷阱，我们测试了在模拟不同污染水平雨水湿地的中观模型中，青蛙的存活率、与变态相关的测量值和对捕食者的回避行为是否存在差异，并将其与自然产卵实验相结合，以评估繁殖地的偏好。我们首次提供了经验证据，证明这些湿地可能成为青蛙的生态陷阱。在污染更严重的雨水湿地中，蝌蚪的存活率更低，对捕食者嗅觉线索的反应也更迟钝，但它们也更早达到变态期，体型更大。更大的变态期体型可能是由于高死亡率与富营养化相结合导致的人均食物供应增加的结果，尽管其他补偿效应，如选择性死亡率将较小的个体从低质量的中观模型中去除，也可能解释这些结果。繁殖成蛙在高污染和低污染湿地中产卵数量相当，这表明它们不会回避前者。由于雨水处理湿地通常是城市景观中唯一可用的水生栖息地，我们需要更好地了解它们作为栖息地的表现，以指导减轻其潜在生态成本的管理决策。这可能包括改善湿地质量，使其适应性不再受到损害，防止动物殖民，改变动物选择栖息地时使用的线索，在释放前对污染水进行预处理，在附近提供离线湿地，或者干脆不在敏感地区建造雨水处理湿地。我们的研究证实了城市雨水处理湿地可能成为生态陷阱，并强调了需要在景观尺度上更加意识到它们的普遍性和影响。
