Search

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 [...]

Predation is a dominant structuring force in ecological communities. In aquatic environments, predation on bivalves has long been an important focal interaction for ecological study because bivalves have central roles as ecosystem engineers, basal components of food webs, and commercial commodities. Studies of bivalves are common, not only because of bivalves' central roles, but also due to the relative ease of studying predatory effects on this taxonomic group. To understand patterns in the interactions of bivalves and their predators we synthesised data from 52 years of peer‐reviewed studies on bivalve predation. Using a systematic search, we compiled 1334 studies from 75 countries, comprising 61 bivalve families (N = 2259), dominated by Mytilidae (29% of bivalves), Veneridae (14%), Ostreidae (8%), Unionidae (7%), and Dreissenidae and Tellinidae (6% each). A total of 2036 predators were studied, with crustaceans the most studied predator group (34% of predators), followed by fishes (24%), molluscs (17%), echinoderms (10%) and birds (6%). The majority of studies (86%) were conducted in marine systems, in part driven by the high commercial value of marine bivalves. Studies in freshwater ecosystems were dominated by non‐native bivalves and non‐native predator species, which probably reflects the important role of biological invasions affecting freshwater biodiversity. In fact, while 81% of the studied marine bivalve species were native, only 50% of the freshwater species were native to the system. In terms of approach, most studies used predation trials, visual analysis of digested contents and exclusion experiments to assess the effects of predation. These studies reflect that many factors influence bivalve predation depending on the species studied, including (i) species traits (e.g. behaviour, morphology, defence mechanisms), (ii) other biotic interactions (e.g. presence of competitors, parasites or diseases), and (iii) environmental context (e.g. temperature, current velocity, beach exposure, habitat complexity). There is a lack of research on the effects of bivalve predation at the population and community and ecosystem levels (only 7% and 0.5% of studies respectively examined impacts at these levels). At the population level, the available studies demonstrate that predation can decrease bivalve density through consumption or the reduction of recruitment. At the community and ecosystem level, predation can trigger effects that cascade through trophic levels or effects that alter the ecological functions bivalves perform. Given the conservation and commercial importance of many bivalve species, studies of predation should be pursued in the context of global change, particularly climate change, acidification and biological invasions. [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]

Strategies for managing biological invasions are often based on the premise that characteristics of invading species and the invaded environment are key predictors of the invader's distribution. Yet, for either biological traits or environmental characteristics to explain distribution, adequate time must have elapsed for species to spread to all potential habitats. We compiled and analyzed a database of natural history and ecological traits of 138 coastal marine invertebrate species, the environmental conditions at sites to which they have been introduced, and their date of first introduction. We found that time since introduction explained the largest fraction (20%) of the variability in non-native range size, while traits of the species and environmental variables had significant, but minimal, influence on non-native range size. The positive relationship between time since introduction and range size indicates that non-native marine invertebrate species are not at equilibrium and are still spreading, posing a major challenge for management of coastal ecosystems.

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]