Direct and indirect effects of a common cyanobacterial toxin on amphibian-trematode dynamics

Incorporating Microbial Species Interaction in Management of Freshwater Toxic Cyanobacteria: A Systems Science Challenge

Water resources are critically important, but also pose risks of exposure to toxic and pathogenic microbes. Increasingly, a concern is toxic cyanobacteria, which have been linked to the death and disease of humans, domesticated animals, and wildlife in freshwater systems worldwide. Management approaches successful at reducing cyanobacterial abundance and toxin production have tended to be short-term solutions applied on small scales (e.g., algaecide application) or solutions that entail difficult multifaceted investments (e.g., modification of landscape and land use to reduce nutrient inputs). However, implementation of these approaches can be undermined by microbial species interactions that (a) provide toxic cyanobacteria with protection against the method of control or (b) permit toxic cyanobacteria to be replaced by other significant microbial threats. Understanding these interactions is necessary to avoid such scenarios and can provide a framework for novel strategies to enhance freshwater resource management via systems science (e.g., pairing existing physical and chemical approaches against cyanobacteria with ecological strategies such as manipulation of natural enemies, targeting of facilitators, and reduction of benthic occupancy and recruitment). Here, we review pertinent examples of the interactions and highlight potential applications of what is known.

Effects of Polyester Microplastic Fiber Contamination on Amphibian-Trematode Interactions

Microplastic contamination poses a global threat to aquatic organisms, yet we know little as to how microplastics may indirectly affect organismal health via their influence on species-species interactions (e.g., host-parasite interactions). This is problematic because microplastic-mediated alterations to host-parasite dynamics could negatively impact individual- population-level health of hosts. Using a larval amphibian (host) and free-living trematode (parasite) model, we asked whether 1) polyester microplastic fibers influence parasite survival; 2) whether polyester microplastic fiber ingestion by amphibians alters amphibian susceptibility to infection; and 3) whether simultaneous exposure of amphibians and trematodes to polyester microplastic fibers influences infection outcomes. Polyester microplastic fibers did not alter trematode survival, nor did their ingestion by amphibians increase amphibian susceptibility to infection. However, when amphibians and trematodes were exposed simultaneously to the fibers, the infection success of the parasite was reduced. Lastly, we conducted a field survey for microfiber contamination across multiple ponds and found microfibers across each of the sampled ponds. Overall, our results contribute to the limited knowledge surrounding the ecological consequences of microplastic contamination. Environ Toxicol Chem 2022;41:869-879. © 2021 SETAC.

A Mini-Review on Recent Developments in Anti-Icing Methods

An aggressive impact of the formed ice on the surface of man-made objects can ultimately lead to serious consequences in their work. When icing occurs, the quality and characteristics of equipment, instruments, and building structures deteriorate, which affects the durability of their use. Delays in the adoption of measures against icing endanger the safety of air travel and road traffic. Various methods have been developed to combat de-icing, such as mechanical de-icing, the use of salts, the application of a hydrophobic coating to the surfaces, ultrasonic treatment and electric heating. In this review, we summarize the recent advances in the field of anti-icing and analyze the role of various additives and their operating mechanisms.

Effects of different roadway deicing salts on host-parasite interactions: The importance of salt type

The application of roadway deicing salts is increasing the salinity of freshwater systems. Increased salinization from salts, such as NaCl, CaCl₂ and MgCl_2, can have direct, negative impacts on freshwater organisms at concentrations found in nature. Yet, our understanding of how these salts can indirectly impact freshwater organisms by altering important ecological interactions, such as those between hosts and their parasites, is limited. Using a larval amphibian and infectious free-living helminth (i.e. trematode) model, we examined whether exposure to environmentally relevant concentrations of NaCl, CaCl₂ and MgCl₂ 1) influence trematode mortality; 2) alter amphibian-trematode interactions; and 3) alter larval amphibian activity (a behavior associated with parasite avoidance). We found that exposure to CaCl₂ greatly reduced trematode survival across all Cl^- concentrations (230, 500, 860 and 1000 mg Cl^- L^-1) while NaCl and MgCl₂ had no effect. When both host and parasites were exposed to the salts, exposure to NaCl, but not MgCl₂ or CaCl₂, increased infection. The lack of effect of CaCl₂ on infection was likely driven by CaCl₂ reducing trematode survival. Exposure to NaCl increased infection at 500 mg Cl^- L^-1, but not 230 or 860 mg Cl^- L^-1. Increased infection was not due to salt exposure altering tadpole behavior. Our results suggest that NaCl can negatively impact amphibian populations indirectly by increasing trematode infections in tadpole hosts.