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Emerging infectious diseases in marine systems threaten food security and ecosystem function. Experiments to determine drivers of transmission and mortality from emerging pathogens require a reliable supply of disease-free animals. Imperfect detection of subclinical, latent, and early stage infections, however, necessitates effective treatments to remove infection from animals with unknown infection status. In this study, a procedure utilizing elevated temperatures and over-the-counter parasiticides to remove Hyalophysa lynni was developed. The apostome ciliate H. lynni is responsible for shrimp black gill (sBG) disease in commercially important southeastern shrimp fishery species, including Litopenaeus setiferus (white shrimp). Following a series of pilot studies to determine parasiticides combination and dosage, L. setiferus of unknown infection status were exposed to either 20[degrees]C or 30[degrees]C artificial seawater, and a parasiticide cocktail of metronidazole (3.15 mg [L.sup.-1]) and Cu+2 (0.5 mg [L.sup.-1]) or a medication-free control for 14 days in a fully crossed experimental design. All treatments, except for the 20[degrees]C without medications treatment, significantly reduced pathogen prevalence. The 30[degrees]C artificial seawater with parasiticide treatment resulted in complete curing of the experimental population, but shrimp mortality in this treatment was high (50%). This high mortality may have contributed to the low parasite prevalence found in this treatment by differentially culling infected individuals. If this is the case, the parasiticides may lower the parasite prevalence both by curing infections and heightening stress and subsequent mortality of diseased individuals. Although this procedure was developed to produce H. lynni-free shrimp to facilitate experimental studies of sBG disease, it is likely that this methodology would effectively produce specific-pathogen-free individuals in other crustacean species. KEY WORDS: Litopenaeus setiferus, Crustacea, Hyalophysa lynni, shrimp black gill, disease, parasiticides, gill parasite, apostome ciliate, INTRODUCTION Many marine systems are experiencing emerging infectious diseases that cause significant mortality in commercially and ecologically important species, threatening food security, and ecosystem function (Lafferty et al. 2015, Byers [...]

Predators regulate communities through top‐down control in many ecosystems. Because most studies of top‐down control last less than a year and focus on only a subset of the community, they may miss predator effects that manifest at longer timescales or across whole food webs. In southeastern US salt marshes, short‐term and small‐scale experiments indicate that nektonic predators (e.g., blue crab, fish, terrapins) facilitate the foundational grass, Spartina alterniflora, by consuming herbivorous snails and crabs. To test both how nekton affect marsh processes when the entire animal community is present, and how prior results scale over time, we conducted a 3‐year nekton exclusion experiment in a Georgia salt marsh using replicated 19.6 m2 plots. Our nekton exclusions increased densities of plant‐grazing snails and juvenile deposit‐feeding fiddler crab and, in Year 2, reduced predation on tethered juvenile snails, indicating that nektonic predators control these key macroinvertebrates. However, in Year 3, densities of mesopredatory benthic mud crabs increased threefold in nekton exclusions, erasing the tethered snails' predation refuge. Nekton exclusion had no effect on Spartina biomass, likely because the observed mesopredator release suppressed grazing snail densities and elevated densities of fiddler crabs, whose burrowing alleviates soil stresses. Structural equation modeling supported the hypotheses that nektonic predators and mesopredators control invertebrate communities, with nektonic predators having stronger total effects on Spartina than mud crabs by controlling densities of species that both suppress (grazers) and facilitate (fiddler crabs) plant growth. These findings highlight that salt marshes can be resilient to multiyear reductions in nektonic predators if mesopredators are present and that multiple pathways of trophic control manifest in different ways over time to mediate community dynamics. These results highlight that larger scale and longer‐term experiments can illuminate community dynamics not previously understood, even in well‐studied ecosystems such as salt marshes. [ABSTRACT FROM AUTHOR]

For marine species with planktonic dispersal, invasion of open ocean coastlines is impaired by the physical adversity of ocean currents moving larvae downstream and offshore. The extent species are affected by physical adversity depends on interactions of the currents with larval life history traits such as planktonic duration, depth and seasonality. Ecologists have struggled to understand how these traits expose species to adverse ocean currents and affect their ability to persist when introduced to novel habitat. We use a high‐resolution global ocean model to isolate the role of ocean currents on the persistence of a larval‐producing species introduced to every open coastline of the world. We find physical adversity to invasion varies globally by several orders of magnitude. Larval duration is the most influential life history trait because increased duration prolongs species' exposure to ocean currents. Furthermore, variation of physical adversity with life history elucidates how trade‐offs between dispersal traits vary globally. [ABSTRACT FROM AUTHOR]

Ecosystems vary broadly in their responses to disturbance, ranging from highly impacted to resilient or resistant. We conducted a large‐scale analysis of hurricane disturbance effects on coastal marshes by examining 20 years of data from 10 sites covering 100,000 ha at the Georgia Coastal Ecosystems Long‐Term Ecological Research site distributed across gradients of salinity and proximity to the ocean. We analyzed the impacts of Hurricanes Matthew (in 2016) and Irma (in 2017) on marsh biota (plants, crabs, and snails) and physical attributes (erosion, wrack deposition, and sedimentation). We compared these variables prior to the storms (2000–2015) to years with storms (2016, 2017) to those after the storms (2018–2020). Hurricanes generated storm surges that increased water depth and salinity of oligotrophic areas for up to 48 h. Biological variables in the marsh showed few effects of the hurricanes. The only physical variable affected was creek bank slumping; however, slumping had already increased a year before the hurricanes, suggesting that slumping could have a different cause. Thus, our study uncovered only minor, ephemeral impacts on Georgia coastal marshes, highlighting their resistance to hurricane disturbance of the lower magnitude that typically confronts this region of coastline. [ABSTRACT FROM AUTHOR]

Fisheries and aquaculture provide food and economic security, especially in the developing world, but both face challenges from infectious disease. Here, we consider management of disease issues from a structured decision‐making perspective to examine how infectious disease can threaten seafood production and influence management decisions. For both wild fisheries and aquaculture, disease‐management objectives generally aim to mitigate the severity and economic burden of outbreaks. General management strategies include manipulating host densities, reducing system connectivity, conserving or improving habitat, and implementing direct treatments or some other biological interventions. To inform decisions, mathematical models can be used to explore disease dynamics and to forecast the potential effectiveness of alternative management actions. Developing and implementing disease‐management strategies also involve considering uncertainties and balancing competing stakeholder interests and risk tolerances. We conclude by outlining several steps for applying structured decision making that are broadly useful to decision makers facing issues related to disease. [ABSTRACT FROM AUTHOR]

Ecosystem engineers (EEs) strongly influence ecosystems by affecting the abiotic properties of a system to which many biota respond. EEs can, thus, be pivotal species in restoration by helping to move systems toward desired states much faster and more efficiently than direct human intervention on the abiotic state.For EEs to play a central, purposeful role in restoration, it is important to identify guiding principles about how the EEs may best be selected and incorporated.I discuss three important aspects to determine (a) where the utility for EEs is high; (b) where EEs can most easily establish, are easy to handle and scaling‐up their use is possible; and (c) how to recognize and value multiple, coupled and trait‐dependent engineering functions of EEs.Understanding these aspects of EEs should help guide purposeful and efficient choices in our approach to restoration. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Parasitism rates can vary dramatically across large and small spatial scales. Such heterogeneity in infection is driven by variation in environmental factors that influence the probability of host and parasite encountering each other (encounter filters) and of genetic and physiological factors that alter whether that encounter results in a successful infection (compatibility filters). Here, we investigated how infection in first‐intermediate hosts (snails) by trematode parasites is influenced by small‐scale variation in environmental variables (final host relative abundance, nutrients, and temperature) and population origin across multiple ponds within an artificial flow‐through wetland system in Atlanta, GA, U.S.A.We placed individually marked, lab‐reared F1 generation snails of the same age from three different populations into field enclosures at nine ponds along a 1‐km stretch of connected, flow‐through ponds for 86 days and allowed them to accrue infections naturally. This highly controlled field experiment allowed us to disentangle the underlying factors influencing small‐scale variation in infection risk, which can be masked when looking only at natural patterns of infection prevalence across space.We found high heterogeneity in infection risk. The probability of infection was highest in ponds downstream and with high levels of bird activity; population origin was not important.This work provides experimental evidence that infection risk varies across small spatial scales (tens of metres), driven by steep gradients in influential environmental drivers, emphasising the importance of controlled field manipulations to understand infection risk. Identifying small‐scale drivers of infection risk can help mitigate infection in hosts of interest (e.g., humans, fish), and should be acknowledged in organismal field studies, where infection and infection risk may influence the ecology, physiology, or behaviour of animals. [ABSTRACT FROM AUTHOR]