Ecosystem-Based Restoration to Mitigate Eutrophication: A Case Study in a Shallow Lake

Under the influence of human activities, eutrophication has become an increasingly serious global phenomenon, especially in shallow lakes. Many studies have shown that aquatic macrophytes play a significant role in controlling eutrophication, but only few of these studies are ecosystem based. In this paper, we applied a mass-balance ecosystem model to a shallow eutrophic lake (Lake Datong, China) as a case study with the aims of evaluating the status of ecosystem restoration via the recovery of aquatic vegetation and providing adaptive management suggestions. Results showed that the ecosystem was immature with weak energy flows and nutrient cycling largely due to the excessive submerged macrophytes and the lack of fish as consumer. In the early stages of restoration, the number of fish should be reduced, and aquatic vegetation needs to be recovered to mitigate eutrophication. When the aquatic vegetation community tends to be stable, herbivorous and omnivorous fish should be moderately stocked, and dead aquatic macrophytes should be harvested to maintain the healthy and sustainable development of the ecosystem. This study provided insights for the ecological restoration of shallow eutrophic lakes and revealed the urgent need for ecosystem-based restoration

Ineffective integration of multiple antipredator defenses in a rotifer: a low-cost insurance?

To maximize survival, prey often integrates multiple anti-predator defenses. How the defenses interact to reduce predation risk is, however, poorly known. We used the rotifer Brachionus calyciflorus to investigate how morphological (spines) and behavioral (floating) defenses are integrated against a common predatory rotifer, Asplanchna brightwellii, and if their combined use improves survival. To this end, we assessed the cost of the behavioral defense and the efficiency of both defenses, individually and combined, as well as their mutual dependency. The results show that the behavioral defense is costly in reducing foraging activity, and that the two defenses are used simultaneously, with the presence of the morphological defense enhancing the use of the behavioral defense, as does the pre-exposure to predator cues. However, while the morphological defense reduces predation risk, the behavioral defense does not, thus, adding the costly behavioral defense to the morphological defense does not improve survival. It is likely that the cost of the behavioral defense is low given its reversibility-compared to the cost of misidentifying the predator species-and that this has promoted the adoption of both defenses, as general low-cost insurance rather than as a tailored strategy toward specific predators. Thus, the optimal strategy in the rotifer appears to be to express both morphological and behavioral defenses when confronted with the cues of a potential predator.When predators are around, no effort should be spared in defending oneself. We show that the rotifer, Brachionus calyciflorus, uses both spines on its body and floating behavior to defend itself when exposed to predator cues. However, only spines are needed to reduce predation risk. It seems likely that the low cost of floating has promoted its adoption, in addition to the possession of spines: it offers a general low-cost insurance against predation.Peer reviewe

Biomimetic Ag/ZnO@PDMS Hybrid Nanorod Array-Mediated Photo-induced Enhanced Raman Spectroscopy Sensor for Quantitative and Visualized Analysis of Microplastics

Microplastics are persistent pollutants that accumulate in the environment and can cause serious toxicity to mammals. At present, few technologies are able to quantitatively detect chemicals and provide morphological information simultaneously. Herein, we developed a dragonfly-wing-mimicking ZnO nanorod array decorated with AgNPs on polydimethylsiloxane (PDMS) as a surface-enhanced Raman spectroscopy (SERS) and photo-induced enhanced Raman spectroscopy (PIERS) substrate for trace analysis of microplastics. The Ag/ZnO@PDMS hybrid nanorod array endows the sensor with high sensitivity and signal repeatability (RSD ∼ 5.89%), ensuring the reliable quantitative analysis of microplastics. Importantly, when the noble metal–semiconductor substrate was pre-radiated with ultraviolet light, a surprising PIERS was attained, achieving an additional enhancement of 11.3-fold higher than the normal SERS signal. By combining the PIERS technology with the “coffee ring effect”, the sensor successfully discerned microplastics of polyethylene (PE) and polystyrene (PS) at a trace level of 25 μg/mL even with a portable Raman device. It was capable of identifying PS microspheres in contaminated tap water, lake water, river water, and seawater with detection limits of 25, 28, 35, and 60 μg/mL, respectively. The recovery rates of PS microspheres in four water environments ranged from 94.8 to 102.4%, with the RSD ranging from 2.40 to 6.81%. Moreover, quantitative and visualized detection of microplastics was readily realized by our sensor. This portable PIERS sensor represents a significant step toward the generalizability and practicality of quantitative and visual sensing technology