Instant Ocean Versus Natural Seawater: Impacts on Aspects of Reproduction and Development in Three Marine Invertebrates

Comparative impact of sunlight and salinity on human pathogenic virus survival in river, estuarine, and marine water microcosms

Urban wastewater contains a diverse array of human pathogenic viruses, often in high concentrations, presenting a significant challenge for water quality management. Sewage spills into natural water systems therefore pose a significant public health risk due to the potential to cause viral infections, yet the behaviour of viruses under dynamic environmental conditions remains poorly understood. This study investigates the decay of sewage-associated viruses (Adenovirus, Enterovirus, Hepatitis A Virus, Influenza A Virus, Norovirus GII, and Respiratory Syncytial Virus) in river, estuary, and marine water, with and without simulated sunlight. Using both qPCR and capsid integrity qPCR (CI-qPCR) methods, we found that in the absence of sunlight, time was the most significant factor influencing viral decay across all water types. The time required for a 90 % reduction in viral gene copies (T90) was observed within 0.3-24.3 days. Simulated sunlight accelerated viral decay, with significant reductions in gene copies l-1 observed within 1-3 days for all viruses studied, and T90 values ranging from 7 to 62.8 h. The effect of salinity on viral decay varied among viruses and water types. These results highlight the complex interplay between environmental water properties and viral persistence, emphasizing the critical role of solar radiation in viral inactivation. The study also demonstrates the value of using both qPCR and CI-qPCR methods to assess total and potentially infectious viral loads, respectively. These results have important implications for water quality management and public health risk assessment in diverse aquatic environments, particularly in the context of the increased frequency of sewage spills occurring in response to climate change and increasing urbanization. The data will support improvements in water quality modelling and associated risk management, contributing to more effective measures for protecting public health in coastal and inland water systems.

Microcosm experiment investigating climate-induced thermal effects on human virus viability in seawater: qPCR vs capsid integrity for enhanced risk management

Climate change is intensifying extreme weather events in coastal areas, leading to more frequent discharge of untreated wastewater containing human viruses into coastal waters. This poses a health risk, especially during heatwaves when bathing activity increases. A study examined the survival and viability of seven common wastewater viruses in seawater at different temperatures. Viral genomes were quantified using direct qPCR, whilst viability was assessed using Capsid Integrity qPCR. Results showed that T90 values from direct qPCR were much higher than those from CI-qPCR, suggesting that risk mitigation should be based on viral integrity tests. All viruses remained potentially viable for at least 72 h in environmental seawater and longer in sterile artificial seawater, highlighting the importance of biotic processes in viral inactivation. Viral persistence decreased with increasing temperature. Whilst heatwaves may partially reduce risks from human viral pathogens in coastal waters, they do not eliminate them entirely.

Hyposalinity stress reduces mussel byssus secretion but does not cause detachment

Environmental stressors such as salinity fluctuations can significantly impact the ecological dynamics of mussel beds. The present study evaluated the influence of hyposalinity stress on the detachment and survival of attached mussels by simulating a mussel farming model in a laboratory setting. Byssus production and mechanical properties of thread in response to varying salinity levels were assessed, and histological sections of the mussel foot were analyzed to identify the changes in the byssus secretory gland area. The results showed that hyposalinity stress (20 and 15 psu) led to a significant decrease in mussel byssus secretion, delayed initiation of new byssus production, and reduced plaque adhesion strength and breaking force of byssal threads compared to the control (30 psu) (p < 0.05). The complete suppression of byssal thread secretion in mussels under salinity conditions of 10 and 5 psu, leading to lethality, indicates the presence of a blockade in byssus secretion when mussels are subjected to significant physiological stressors. Histological analysis further demonstrated a decrease in the percentage of foot secretory gland areas in mussels exposed to low salinities. However, contrary to expectations, the study found that mussels did not exhibit marked detachment from ropes in response to the reduced salinity levels during one week of exposure. Hyposalinity stress exposure reduced the byssal secretion capacity and the mechanical properties of threads, which could be a cause for the detachment of suspension-cultured mussels. These results highlight the vulnerability of mussels to hyposalinity stress, which significantly affects their byssus mechanical performance.

A scalable culturing system for the marine annelid Platynereis dumerilii

Platynereis dumerilii is a marine segmented worm (annelid) with externally fertilized embryos and it can be cultured for the full life cycle in the laboratory. The accessibility of embryos and larvae combined with the breadth of the established molecular and functional techniques has made P. dumerilii an attractive model for studying development, cell lineages, cell type evolution, reproduction, regeneration, the nervous system, and behavior. Traditionally, these worms have been kept in rooms dedicated for their culture. This allows for the regulation of temperature and light cycles, which is critical to synchronizing sexual maturation. However, regulating the conditions of a whole room has limitations, especially if experiments require being able to change culturing conditions. Here we present scalable and flexible culture methods that provide ability to control the environmental conditions, and have a multi-purpose culture space. We provide a closed setup shelving design with proper light conditions necessary for P. dumerilii to mature. We also implemented a standardized method of feeding P. dumerilii cultures with powdered spirulina which relieves the ambiguity associated with using frozen spinach, and helps standardize nutrition conditions across experiments and across different labs. By using these methods, we were able to raise mature P. dumerilii, capable of spawning and producing viable embryos for experimentation and replenishing culture populations. These methods will allow for the further accessibility of P. dumerilii as a model system, and they can be adapted for other aquatic organisms.