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Monogenean infection of the internal organs is extremely rare when compared to external infections. This study describes mass mortality of Nile tilapia (Oreochromis niloticus L.) originating from co‐infection with Enterogyrus spp. and Aeromonas jandaei following transport stress. The first fish deaths occurred on day 1 post‐transport, while cumulative mortality reached approximately 90% by day 10 post‐stocking. An atypical amount of pale (whitish) faeces floating on the surface of the water as well as typical clinical signs of motile Aeromonas septicemia, were reported. Adult monogeneans and countless eggs of monogeneans were found in the stomachs and the intestines of both moribund and dead fish, respectively. Two strains of A. jandaei were isolated from the kidneys. Scanning electron microscope microphotographs of the stomach revealed the presence of numerous monogeneans penetrating deep into the gastric tissue, and diffuse lesions filled with bacilliform bacteria. Histopathological examination showed multifocal eosinophilic infiltrate, gastric gland and epithelial necrosis with sloughed necrotic debris in the lumen. This is the first report of co‐infection by Enterogyrus spp. and A. jandaei in Nile tilapia and the first report of Enterogyrus coronatus, Enterogyrus foratus, and Enterogyrus malbergi parasitizing tilapia in Brazil. These findings indicate that synergic co‐infection by Monogenean stomach parasites (E. coronatus, E. foratus, and E. malbergi) and A. jandaei may induce high mortalities in tilapia following transport stress. [ABSTRACT FROM AUTHOR]

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Recent mass mortalities of two predatory sea star species provided an unprecedented opportunity to test the effect of predators on rocky intertidal prey. Mass mortalities provide insight that manipulative experiments cannot because they alter ecosystems on a larger scale, for longer time periods, and remove both organisms and their cues from the environment. We examined shifts in population size structure, vertical zonation, and use of emersed refuge habitats outside tidepools by the abundant herbivorous black turban snail Tegula funebralis, both before and after the successive mortalities of two predatory sea stars. The small cryptic predator Leptasterias spp. suffered a localized but extreme mortality event in November 2010, followed by two mass mortalities of the keystone predator Pisaster ochraceus in August 2011 and autumn 2013. After the local extinction of Leptasterias, the population size of Tegula more than doubled. Also, since Leptasterias primarily inhabited only mid to low intertidal tidepools at this site, small and medium sized snails (which are preferred by Leptasterias) shifted lower in the intertidal and into tidepools after the mortality of Leptasterias. After the mortality of Pisaster in August 2011, large snails did not shift lower in the intertidal zone despite being preferred by Pisaster. Small and medium sized snails became denser in the higher zone and outside tidepools, which was not likely due to Pisaster mortality. Previous studies concluded that Pisaster maintained vertical size gradients of snails, but our data implicate the overlooked predator Leptasterias as the primary cause. This natural experiment indicated that (1) predators exert top-down control over prey population sizes and lower limits, (2) vertical zonation of prey are dynamic and controlled in part by prey behavior, and (3) predators exert the strongest effects on more vulnerable individuals, which typically inhabit stressful habitats higher on the shore or outside tidepools to avoid predation. Because the mass mortalities of two predators drastically reduced both the predation pressure and the chemical cues of predators in the environment, we were able to investigate both the effects of predators on prey populations and the effects on mobile prey behavior.

In recent years, the frequency of mass mortality events in marine ecosystems has increased, and several populations of benthic organism have been affected, reducing their density and changing their size and age structure. Few details are known about the dynamics of these populations over long time intervals. In late summer of both 1999 and 2003 two drastic mass mortality events, co-occurring with anomalous temperature increases, affected the northwestern Mediterranean rocky coastal communities. Due to these events the Paramuricea clavata population living at the western edge of La Spezia Gulf (Italy) was stricken, and 78% of the colonies died. This population was monitored from 1998 (pre-mortality) until 2013. This paper deals with the photographic sampling of permanent plots carried out in 2013. The findings were compared with those from the previous sampling series. This long-term, non-destructive sampling highlights the demographic trajectory of the octocoral population there after two anomalous mortality events, indicating that some new drop-point between local extinction and complete recovery may be have been reached. Long-term monitoring (including pre-mortality data) could allow evaluating the effects of global climate change on the conservation of impacted populations.

Pacific oyster mortality syndrome (POMS) in Pacific oysters Crassostrea gigas is defined by mass mortality with Ostreid herpesvirus I (OsHV-1). In this study the association of Vibrio species with oysters before, during and after POMS events was investigated at population level to clarify their involvement with OsHV-1 in mass mortality events in the Georges and Hawkesbury River estuaries, Australia. In the POMS affected Georges River estuary, three patterns were observed concurrently at different sites: i) Vibrio counts and OsHV-1 DNA concentrations increased in adults and spat as mortalities started then decreased as mortalities stopped ii) bacterial counts increased in spat but not in adults associated with mortalities due to OsHV-1 iii) bacterial counts increased in the absence of mass mortality or high concentrations of OsHV-1 DNA. Although almost half of the 120 bacterial isolates were identified as an unknown Vibrio species belonging to the Splendidus clade with two predominant biotypes (A and H), there was no association between biotype and mortality. Concurrently in the Hawkesbury River estuary, neither mortality nor OsHV-1 were found, Vibrio counts fluctuated significantly and of 84 isolates identified, V. alginolyticus, V. parahaemolyticus and unidentified Vibrio sp. dominated; only five Splendidus clade isolates were identified. However, when POMS emerged in the Hawkesbury River estuary, the Splendidus-clade isolate became the dominant bacterial species. Mortality also occurred there without OsHV-1 and the dominant bacteria then were V. alginolyticus and V. harveyi, but the Splendidus-clade isolate was not detected. None of the bacterial species were specifically associated with POMS, although the Splendidus clade isolate increased in prevalence after POMS emerged in the Hawkesbury River estuary. V. aestuarianus was not detected in this study. While the findings suggest that bacterial proliferation follows infection with OsHV-1 in POMS, this was not a consistent feature. The number and diversity of bacteria within oyster tissues varied over time, between estuaries, between sites within an estuary and were associated with flooding, growing height, the age of oysters, mortality and OsHV-1. • Cultivable bacterial and vibrio counts varied over time. • None of the vibrio species identified were specifically associated with POMS. • An unknown Vibrio species in the Splendidus clade became dominant after OsHV-1 mortality. • The environment had a strong effect on bacterial populations in oyster tissues. [ABSTRACT FROM AUTHOR]

Mass Mortality Events (MMEs) affecting the noble pen shell Pinna nobilis have been reported since 2016. In this work, we used an in vitro flow cytometric assay to evaluate phagocytosis, coupled with cytology and Electron Microscopy (TEM), to define animal immunocompetence following infection by P. nobilis Picornavirus (PnPV). The study was performed on 27 animals in July 2021 and May 2022 on two natural population from the Ebro Delta (Catalonia, Spain) and animals maintained in captivity at facilities in Valencia and Murcia Aquarium. Hemolymph was collected in the field and in captivity as a non-destructive sampling method. Based on dimension and internal complexity, flow cytometry identified three haemocyte types, distinguished in granulocytes, hyalinocytes and a third type, biggest in size and with high internal complexity and granularity. Those cells corresponded at ultrastructure to hemocytes with advanced phases of PnPV infection and related to cytopathic effect of the replicating virus displaying numerous Double Membrane Vesicles (DMVs) and cells corpse fusion. The results showed that pen shell in captivity had significantly lower Total Hemocyte Count (THC) compared with natural population of Alfacs Bay (mean number of 7–9 x 104 vs 2-5 x 105 cells/mL, respectively). FACS (Fluorescence-activated cell sorting) based phagocytosis analysis demonstrate that animals in captivity at IMEDMAR-UCV and Murcia Aquarium, had scarce or absent ability to phagocyte the two stimuli (Staphylococcus aureus and Zymosan A) (10,2 % ± 1,7 of positives) if compared with the natural population in Alfacs Bay (28,5 % ± 5,6 of positive). Ultrastructure images showed that PnPV itself can lead to an alteration of the hemocyte cytoskeleton, impairing the capabilities to perform an active phagocytosis and an efficient phagolysosome fusion. [Display omitted] • The Picornavirus P. nobilis Picornavirus PnPV) actively replicates into bivalve hemocytes. • An in vitro flow cytometric assay to evaluate phagocytosis, coupled with cytology and Electron Microscopy (TEM), was used to define animal immunocompetence. • Hemolymph was collected in the field and in captivity as a non-destructive sampling method. • Pen shell in captivity had significantly lower Total Hemocyte Count (THC) compared with natural population. • Infected cells had scarce or absent ability to phagocyte PAMPS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Invasive red swamp crayfish are present in 75 of 96 metropolitan French departments. • We studied distribution of Aphanomyces astaci in its populations in western France. • The crayfish plague pathogen was detected in > 75 % of sampled sites. • A. astaci strains from this host caused at least 2 recent crayfish plague outbreaks. • As it spreads, threat posed by P. clarkii to native crayfish will likely increase. The crayfish plague pathogen Aphanomyces astaci has been implicated in a number of mass mortalities and irreversible population declines of native crayfish across Europe. At present, the reservoirs of the pathogen in Europe are mainly populations of invasive North American crayfish species. In southwestern Europe, including France, a particularly widespread invader is the red swamp crayfish Procambarus clarkii. Recent distribution data confirm that P. clarkii is present in at least 75 French departments, i.e. more than 78% of those in metropolitan France. We analysed the prevalence and pathogen load of A. astaci in 42 populations of this species in western France (Nouvelle Aquitaine region), where the species is most densely distributed, particularly in a wide range of environments around the Gironde estuary. The pathogen was detected by two different quantitative PCR assays in more than three quarters of the populations studied (34 out of 42); 163 out of 480 analysed crayfish individuals tested positive for the presence of A. astaci. In most cases, individual infection levels were very low, detectable with quantitative PCR but not sufficient for pathogen genotyping. In seven P. clarkii individuals from four populations, however, we were able to assess A. astaci variation by microsatellite markers and sequencing of mitochondrial markers. All these host specimens carried A. astaci genotype group D, haplotype d1, which has caused the majority of crayfish plague outbreaks in neighbouring Spain. In contrast, the French outbreaks genotyped to date (including eight newly analysed in this study) were mostly caused by strains of genotype group B, specific to the signal crayfish Pacifastacus leniusculus. Haplotype d1 found in P. clarkii was involved in one of the newly characterised outbreaks. Our study confirms that P. clarkii is a potentially important reservoir of the crayfish plague pathogen in France, but not the main source of the pathogen in mass mortalities of A. pallipes , probably due to different ecological requirements of the different invasive host crayfish. However, as P. clarkii continues to spread, the threat posed by this species to native crayfish is likely to increase. [ABSTRACT FROM AUTHOR]

The term 'Satoyama' refers to traditional and unique secondary forests in Japan that occupy intermediate zones between villages ('sato') and hills or mountains ('yama'). Satoyama landscapes help sustain ecosystem services and the diversity of secondary natural environments. As Japan relies more heavily on foreign timber imports, the traditional role of Satoyama in providing forest products has diminished, and this has led to their abandonment and poor management. The chemical behavior of cations, anions, and dissolved organic matter in throughfall and stemflow from one such threatened Satoyama system in central Japan was investigated. From autumn to winter, the atmospheric deposition of sulfates and nitrates was 2.5–6.0 times higher compared to the amounts in summer due to the intrusion of air masses from the Asian continent. The dissolved organic matter in the throughfall and stemflow was composed mainly of humic substances and protein derivatives. The deposition fluxes of dissolved organic carbon from throughfall (7.31–10.1 g m−2 a−1) and stemflow (1.79–3.84 g m−2 a−1) in this study were within ranges seen in temperate forests in previous studies. The deposition flux of sulfates was low compared to that in other forest types because canopy interaction was lower, suggesting higher canopy openness than in primary forests. If a shift from a mixed species Satoyama forest to a conifer-dominated forest occurs after the mass mortality of oak, the deposition flux of dissolved organic carbon and K+ might decrease by 33% and 62%, respectively, while NO3− might increase by 20%. In the near future, the degradation of Satoyama landscapes might change the levels of dissolved organic carbon and nitrogen loads, resulting in imbalances in river-ocean linkages affecting forested catchments and aquatic ecosystems in Japan. [ABSTRACT FROM AUTHOR]

Two Pinna nobilis populations thriving inside the borders of the Portofino Marine Protected Area (MPA) (Ligurian Sea, western Mediterranean Sea) were monitored before (2012) and after (September 2018) a dire mass mortality event that, since September 2016, spread through the whole Mediterranean Sea. In Portofino MPA, recorded mortality rates reached values of 91.29% and 43.94% in the two populations. The presence of a Haplosporidium protozoan parasite, considered to be the main cause of the mortality episodes, was confirmed from histological evidence: sporocysts and plasmodia were observed in all the tubules of the digestive glands of the collected specimens. Moreover, a catastrophic storm hit the Ligurian coasts at the end of October 2018, causing considerable damages both below and above the surface; a new survey conducted in November 2018 showed the complete annihilation of the two studied populations, as a probable combination of the continued parasite infections and the mechanical impacts caused by the storm. Finally, in June 2020 the sites were monitored again looking for traces of recovery, but no new specimens were recorded, indicating that P. nobilis became virtually absent from the MPA.

For many long‐lived taxa, such as trees and corals, older, and larger individuals often have the lowest mortality and highest fecundity. However, climate change‐driven disturbances such as droughts and heatwaves may fundamentally alter typical size‐dependent patterns of mortality and reproduction in these important foundation taxa. Working in Moorea, French Polynesia, we investigated how a marine heatwave in 2019, one of the most intense marine heatwaves at our sites over the past 30 years, drove patterns of coral bleaching and mortality. The marine heatwave drove island‐wide mass coral bleaching that killed up to 76% and 65% of the largest individuals of the two dominant coral genera, Pocillopora and Acropora, respectively. Colonies of Pocillopora and Acropora ≥30 cm diameter were ~3.5× and ~1.3×, respectively, more likely to die than colonies <30‐cm diameter. Typically, annual mortality in these corals is concentrated on the smallest size classes. Yet, this heatwave dramatically reshaped this pattern, with heat stress disproportionately killing larger coral colonies and equalizing annual mortality rates across the size spectrum. This shift in the size‐mortality relationship reduced the overall fecundity of these genera by >60% because big corals are disproportionately important for reproduction on reefs. Additionally, the survivorship of microscopic coral recruits, critical for the recovery of corals following disturbances, declined to 2%, over an order of magnitude lower compared to a year without elevated thermal stress, where 33% of coral recruits survived. While other research has shown that larger corals can bleach more frequently than smaller corals, we show the severe impact this phenomenon can have at the reef‐wide scale. As marine heatwaves become more frequent and intense, disproportionate mortality of the largest, most fecund corals and near‐complete loss of entire cohorts of newly‐settled coral recruits will likely reduce the recovery capacity of these iconic ecosystems. [ABSTRACT FROM AUTHOR]

During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays. One of the main drivers related to these mortalities was hypoxic events. This study was designed to understand the hypoxia phenomenon in these bays and to assess how the Peruvian scallop, Argopecten purpuratus, can cope with reduced oxygen levels in seawater based on individual size. First, we analyzed the relationships between dissolved oxygen saturation and other environmental parameters (the Coastal El Niño Index, temperature, salinity and pH) in bottom seawater, the frequency and intensity of hypoxic events in two main culture areas (Sechura and Paracas Bays), and their relationship with scallop mass mortalities. Then, we performed experiments with two size groups of A. purpuratus (31 and 80 mm shell height; seed and commercial size, respectively) to assess their respective survival time under severe hypoxia (1% oxygen saturation) at 16°C and a salinity of 35. Finally, the results of the field records and the experimental data are used to suggest ways to improve scallop cultivation along the Peruvian coast. [ABSTRACT FROM AUTHOR]

The critically endangered fan mussel Pinna nobilis, endemic to the Mediterranean Sea, faces a drastic population decline all over the Mediterranean Sea owing to an infectious disease.Coastal lagoons represent one of this species' last reservoirs; thus, knowledge of the population conservation status in these ecosystems is essential.An extensive monitoring programme was conducted during 2014, 2017 and 2019 in the Mar Menor lagoon, a highly eutrophicated lagoon from Spain. On average, 32,535 m2 have been surveyed each year to determine population densities, distributions and size structures.The cumulative impacts produced by intensive agriculture activity around the lagoon, together with a catastrophic meteorological phenomenon that occurred in 2019, have triggered a significant decline in fan mussel population densities and in population mean shell sizes over the years. Additionally, some fan mussels were infected by the protozoan Haplosporidium pinnae.Therefore, the current P. nobilis population from the Mar Menor is mainly composed of young individuals in specific areas that are facing an extreme situation. Urgent management and conservation actions focused on restoring the ecosystem and protecting P. nobilis individuals are urgently needed, together with reinforcement projects to increase the species' stock in one of its last reservoirs. [ABSTRACT FROM AUTHOR]

Abstract Background Each death event can be characterized by its associated microbes – a living community of bacteria composed of carcass, soil, and insect-introduced bacterial species – a necrobiome. With the possibility for close succession of these death events, it may be beneficial to characterize how the magnitude of an initial death event may impact the decomposition and necrobiomes of subsequent death events in close proximity. In this paper we hope to characterize the microbial communities associated with a proximate subsequent death event, and distinguish any changes within those communities based on the magnitude of an initial death event and the biomass of preexisting carcass (es) undergoing decomposition. For this experiment, 6 feral swine carcasses in containers were placed in the vicinity of preexisting and ongoing carcass decomposition at sites of three different scales of decomposing carcass biomass. Swab samples were collected from the skin and eye sockets of the container pigs and subjected to 16 s rRNA sequencing and OTU assignment. Results PERMANOVA analysis of the bacterial taxa showed that there was no significant difference in the bacterial communities based on initial mortality event biomass size, but we did see a change in the bacterial communities over time, and slight differences between the skin and ocular cavity communities. Even without soil input, necrobiome communities can change rapidly. Further characterization of the bacterial necrobiome included utilization of the Random Forest algorithm to identify the most important predictors for time of decomposition. Sample sets were also scanned for notable human and swine-associated pathogens. Conclusions The applications from this study are many, ranging from establishing the environmental impacts of mass mortality events to understanding the importance of scavenger, and scavenger microbial community input on decomposition.

Abstract Recurrent sea urchin mass mortality has recently affected eastern Atlantic populations of the barren‐forming sea urchin Diadema africanum. This new episode of die‐off affords the opportunity to determine common meteorological and oceanographic conditions that may promote disease outbreaks. The population dynamics of this sea urchin species are well known—urchin barrens have persisted for many decades along most of the coastlines off the archipelagos of Madeira, Selvages, and the Canary Islands, where they limit macroalgae biomass growth. However, this new and explosive mortality event decimated the sea urchin population by 93% on Tenerife and La Palma Islands. Two severe episodes of southwestern rough sea that led to winter storms, in February 2010 (Xynthia) and February 2018 (Emma), preceded both mass mortality events. The autumn and winter months of those years were anomalous and characterized by swells with an average wave height above 2 m that hit the south and southwest sides of the islands. The amoeba Paramoeba brachiphila was the only pathogen isolated this time from the moribund and dead sea urchins, suggesting that the amoeba was the primary cause of the mortality. This new sea urchin die‐off event supports the “killer‐storm” hypothesis that has been already described for western Atlantic coasts. These anomalous southwest storms during winters generate pronounced underwater sediment movement and large‐scale vertical mixing, detected in local tide gauge, which may promote paramoebiasis. This study presents valuable insights about climate‐mediated changes in disease frequency and its impacts on the future of coastal marine ecosystems in the Atlantic.

Two Pinna nobilis populations thriving inside the borders of the Portofino Marine Protected Area (MPA) (Ligurian Sea, western Mediterranean Sea) were monitored before (2012) and after (September 2018) a dire mass mortality event that, since September 2016, spread through the whole Mediterranean Sea. In Portofino MPA, recorded mortality rates reached values of 91.29% and 43.94% in the two populations. The presence of a Haplosporidium protozoan parasite, considered to be the main cause of the mortality episodes, was confirmed from histological evidence: sporocysts and plasmodia were observed in all the tubules of the digestive glands of the collected specimens. Moreover, a catastrophic storm hit the Ligurian coasts at the end of October 2018, causing considerable damages both below and above the surface; a new survey conducted in November 2018 showed the complete annihilation of the two studied populations, as a probable combination of the continued parasite infections and the mechanical impacts caused by the storm. Finally, in June 2020 the sites were monitored again looking for traces of recovery, but no new specimens were recorded, indicating that P. nobilis became virtually absent from the MPA. [ABSTRACT FROM AUTHOR]

A mass mortality event involving cultured blood cockles (Tegillarca granosa) occurred in the Welu estuary in Chanthaburi Province, Thailand, during July and early August of 2013. We collected surviving blood cockles (n = 30) shortly after the mortality event in mid-August and evaluated the physiological conditions of the specimens by performing histological observations of various organs. We found that most specimens of both sexes were at the peak of spawning. Histological observations revealed an absence of food in their digestive ducts and flattened epithelial cells in their midgut glands. The specimens had been experiencing low food availability and nutrient uptake. In addition, rainfall data for Chanthaburi Province revealed that the rainfall in July 2013 was more than twice the average amount received in previous years, and surface salinity data from around the aquaculture site revealed that salinity was < 10 Practical Salinity Unit for longer than a month. Therefore, we concluded that prolonged low-salinity conditions were a major cause of this mass mortality event. [ABSTRACT FROM AUTHOR]

In the summers of 2019 and 2020, a previously undescribed disease occurred in both juvenile and adult shellfish, causing mass mortalities in cultured pearl production, characterized by the major symptom of extreme atrophy of the soft tissues, including the mantle. However, the causative organism was uncertain. We isolated Vibrio sp. strain MA3 from the mantles of diseased pearl oysters Pinctada fucata. Analyses of 16S rRNA gene and DNA gyrase sequence homologies and its biochemical and morphological characteristics suggested that strain MA3 is a new strain of Vibrio alginolyticus. In addition, a hemolysin gene (Vhe1) of strain MA3 was detected as one of the virulence factors, and the complete sequence was determined. BLAST searches showed that Vhe1 shares 99.8% nucleotide sequence identity with Vibrio alginolyticus strain A056 lecithin-dependent hemolysin (ldh) gene, complete cds. Experimental infection of healthy oysters via injection with strain MA3 indicated it could cause high mortalities of the typically affected oysters from which the strain was isolated. These results suggest that the newly isolated Vibrio sp. strain MA3 is a putative causal agent of the recent disease outbreaks in Akoya pearl oysters. [ABSTRACT FROM AUTHOR]

Freshwater mussels (Unionida) are among the world’s most imperiled taxa, but the relationship between freshwater mussel mortality events and infectious disease is largely unstudied. We surveyed viromes of a widespread and abundant species (mucket, Actinonaias ligamentina; syn: Ortmanniana ligamentina) experiencing a mortality event of unknown etiology in the Huron River, Michigan, in 2019–2020 and compared them to viromes from mucket in a healthy population in the St. Croix River, Wisconsin and a population from the Clinch River, Virginia and Tennessee, where a mortality event was affecting the congeneric pheasantshell (Actinonaias pectorosa; syn: Ortmanniana pectorosa) population. We identified 38 viruses, most of which were associated with mussels collected during the Huron River mortality event. Viral richness and cumulative viral read depths were significantly higher in moribund mussels from the Huron River than in healthy controls from each of the three populations. Our results demonstrate significant increases in the number and intensity of viral infections for freshwater mussels experiencing mortality events, whereas individuals from healthy populations have a substantially reduced virome comprising a limited number of species at low viral read depths.

Mass mortality of 0-year-old pearl oysters, Pinctada fucata (Gould), and anomalies in adults were observed in Japan’s major pearl farming areas in the summer of 2019 and 2020. Although adult oyster mortality was low, both adult and juvenile oysters underwent atrophy of the soft body, detachment of the mantle from nacre (the shiny inner surface of the valves), deposition of brownish material on the nacre, and loss of nacre luster. Infection trials were conducted to verify the involvement of pathogens in this phenomenon. Healthy adult pearl oysters were obtained from areas where this disease had not occurred to use as the recipients. The sources of infection were either affected adult oysters with atrophied soft bodies or batches of juveniles in which mortality had reached conspicuous levels. Transmission of the disease to the healthy oysters were tested either by cohabitation with affected oysters or by injections of the hemolymph of affected animals. The injection infection test examined the effects of filtration and chloroform exposure on the pathogen. Occurrence of the disease was confirmed by the appearance of brown deposits on the nacre and loss of nacre luster. The abnormalities of nacre were clearly reproduced in recipient shells in three out of four cohabitation trials with affected oysters. The disease was also reproduced in six out of six injection trails either with hemolymph filtered through 100 nm filter or with hemolymph treated with chloroform. In a serial passage with hemolymph injections, the disease was successfully transmitted through eight passages. These results suggest that the etiology of the disease is a non-enveloped virus with a diameter ≤100 nm.

Introduction: Coral reefs are negatively affected by different anthropogenic and environmental causes in the Gulf of Papagayo, Costa Rican Pacific coast. Objective: The health status of the Playa Blanca coral reef was evaluated. Methods: Between August 2010 and September 2011, the percentage of live coral cover (LCC) per species and of the macroalgae Caulerpa sertularoides was determined in four sectors and at three depths of the coral reef; the annual growth of Pocillopora damicornis and P. elegans was measured and related to temperature, nutrients, wind, sun irradiation and rain. Results: 14 species of corals were found, two of them, Fungia curvata and Leptoseris papyracea, only as skeletons. The area with the highest LCC was offshore in the middle zone of Playa Blanca. The species with the highest coverage in all depth ranges was P. damicornis, followed by P. elegans. The LCC decreased from 29% in September 2010 to 1% in October 2010 due to a mass coral mortality caused by harmful algal blooms. The growth rate of P. damicornis (26.0 ± 8.9 mm year-1) and P. elegans (27.9 ± 4.5 mm year-1) did not show significant differences between depths or location in the reef. Conclusions: The exuberant Playa Blanca coral reef experienced a sudden drop in LCC similar to those described by Glynn et al. (1983). This suggests that cycles of mortality and natural recovery of coral reefs occur, although anthropogenic pressures reduce the resilience capacity of the reefs. Spatial planning, both on land and in the sea, is vital for adequate human development, in which the increase in the resilience of coral ecosystems is incorporated into the analysis. [ABSTRACT FROM AUTHOR]

Reduced streamflow because of climate change presents a major threat to aquatic biodiversity in arid, semi-arid and Mediterranean climatic regions. Freshwater mussels are particularly sensitive to this threat, because of their sedentary nature and limited mobility as juveniles or adults. The freshwater mussel Westralunio carteri, which is endemic to south-western Australia, has undergone a 49% reduction in range in the last 50 years, and a drying climate presents substantial extinction risk, as highlighted by two recent cases of mass mortality. Experimental studies found that mussels respond to water emersion by first tracking receding water levels, then burrowing. The amount of horizontal movement by mussels was not affected by size, but smaller mussels initiated burrowing sooner and were also more likely to be predated if they remained on the surface. Burrowing and shading both significantly reduced mortality rate and increased survival time when mussels were exposed to drying; when shaded or allowed to burrow, mussels could survive at least 62 days out of water. Predicted future reductions in streamflow are likely to increase the mortality rate in W. carteri, but it may be possible to partially avert the adverse effects of drying rivers by increasing riparian shading. [ABSTRACT FROM AUTHOR]

Sea urchins are primary herbivores on coral reefs, regulating algal biomass and facilitating coral settlement and growth. 1,2,3,4,5,6,7,8,9,10,11,12 Recurring mass mortality events (MMEs) of Diadema species Gray, 1825 have been recorded globally, 13,14,15,16,17,18,19,20,21,22,23 the most notorious and ecologically significant of which occurred in the Caribbean in 1983, 14,17,19,20 contributing to the shift from coral to algal-dominated ecosystems. 17,24,25 Recently, first evidence of Diadema setosum mass mortality was reported from the eastern Mediterranean Sea. 23 Here, we report extensive mass mortalities of several diadematoid species inhabiting the Red Sea and Western Indian Ocean (WIO) 26,27,28 including first evidence of mortalities in the genus Echinothrix Peters, 1853. Mortalities initiated in the Gulf of Aqaba on December 2022 and span the Red Sea, the Gulf of Oman, and the Western Indian Ocean (Réunion Island), with population declines reaching 100% at some sites. Infected individuals are characterized by spine loss and tissue necrosis, resulting in exposed skeletons (i.e., tests) and mortality. Molecular diagnostics of the 18S rRNA gene confirm the presence of a waterborne scuticociliate protozoan most closely related to Philaster apodigitiformis in infected specimens—identical to the pathogen found in the 2022 Caribbean mass mortality of Diadema antillarum. 13,15,18 Collapse of these key benthic grazers in the Red Sea and Western Indian Ocean may lead to algal dominance over corals, threatening the stability of coral reefs on a regional scale. 29,30,31,32 We issue a warning regarding the further expansion of mortalities and call for immediate monitoring and conservation efforts for these key ecological species. • Mass mortalities of diadematoid sea urchins spread through the Red Sea and WIO • Species of both Diadema and Echinothrix are susceptible to mortalities • Population declines in D. setosum and E. calamaris in the Gulf of Aqaba reach 100% • Molecular analyses confirm the presence of a Philaster -like scutocilliate protozoan Roth et al. report regional-scale mass mortalities of diadematoid sea urchins in the Red Sea and Western Indian Ocean, driving population declines of up to 100% in Diadema and Echinothrix species since December 2022. Genetic analyses confirm the presence of the Caribbean D. antillarum pathogen, a Philaster- like scuticociliate, in infected specimens. [ABSTRACT FROM AUTHOR]

The highly pathogenic Avian Influenza virus (HPAIV) H5N1 has caused a global outbreak affecting both wild and domestic animals, predominantly avian species. To date, cases of the HPAIV H5 Clade 2.3.4.4b in penguins have exclusively been reported in African Penguins. In Chile, the virus was confirmed in pelicans in December 2022 and subsequently spread across the country, affecting several species, including Humboldt penguins. This study aims to provide an overview of the incidents involving stranded and deceased Humboldt penguins and establish a connection between these events and HPAIV H5N1. Historical data about strandings between 2009 and 2023 was collected, and samples from suspected cases in 2023 were obtained to confirm the presence of HPAIV H5N1. Between January and August 2023, 2,788 cases of stranded and deceased penguins were recorded. Out of these, a total of 2,712 penguins deceased, evidencing a significative increase in mortality starting in early 2023 coinciding with the introduction and spreading of HPAIV H5N1 in the country. Thirty-seven events were categorized as mass mortality events, with the number of deceased penguins varying from 11 to 98. Most cases (97 %) were observed in the North of Chile. One hundred and eighty-one specimens were subjected to HPAIV diagnosis, four of which tested positive for HPAIV H5N1. Spatial analysis validates the correlation between mass mortality events and outbreaks of HPAIV in Chile. However, the limited rate of HPAIV H5N1 detection, which can be attributed to the type and quality of the samples, requiring further exploration. • Historical data about strandings of Humboldt Penguin (Sphenicus humboldti) in Chile, between 2009 and 2023. • A significant increase in mortality started in early 2023 coinciding with the introduction of HPAIV H5N1 in Chile. • 37 massive mortality events were recorded; ranging from 11 to 98 deceased penguins each, mostly in the North of Chile. • 4 out of 181 penguins were positive for HPAIV H5N1, published data indicates different introductions. • Spatial analysis validates the correlation between mass mortality events and outbreaks of HPAIV in Chile. [ABSTRACT FROM AUTHOR]

Unexplained oyster mass mortalities threaten to destabilize the oyster industry on Canada's west coast if left unexplored. A range of potentially causative factors have been identified by the industry and the scientific community but the effects and magnitudes of these factors on oyster mortality risks remain unknown. Through a structured expert elicitation questionnaire, this study presents industry and scientific experts' calibrated judgements of cause of this multifactorial problem. We document low agreement among scientists and oyster growers with regards to important causative groups of factors. There is some agreement that factors like water temperature, seasonality, bacterial pathogens, affect oysters suspended in water and reared in trays, particularly if they are large oysters. However, both scientists and growers harbored differing views about the age and size of oysters susceptible to mass mortalities and the role of food availability and gametogenesis in contributing to mass mortalities. We discuss potential sources of these differing opinions and misconceptions. Our findings also highlight the need for additional research to resolve some of the uncertainty in experts' perceptions of cause. Risk communication efforts in the future should focus on these differing perspectives to work toward mutually viable decisions and solutions. • Unexplained oyster mass mortalities threaten Canadian west coast shellfish industry. • Expert elicitation yielded calibrated judgement of causes of oyster mass mortalities. • Scientists and oyster growers have low agreement about causative factor groups. • Risk communication can highlight differing opinions and clarify misconceptions. [ABSTRACT FROM AUTHOR]

Mucilage events may severely affect the benthic fauna and flora in marine environment, likely causing serious mortality in marine life. The present study was made on a massive mucilage phenomenon in the Çanakkale Strait (Dardanelles) and North Aegean Sea in 2021. Blanket type of mucilage existed for five months between March and July in the Çanakkale Strait, impacting marine benthos, which lead to a likely ecological destruction at some locations. Saros Bay, Gökçeada, Bozcaada and Tavşan Islands (Mavriya) were also impacted by this massive mucilage phenomenon. The highest mean thickness of blanket type of mucilage was observed as 16.26±5.97 cm, while the lowest value was measured as 3.5±0.86 cm. Regarding mucilage aggregates-based mortality in marine invertebrates, 77 individuals of the Pennatulacean coral Pteroeides spinosum were found dead. Data of thickness on substratum of mucilage aggreates is reported for the first time in the inventory of the Turkish marine researches. [ABSTRACT FROM AUTHOR]

Mass mortality of sea urchin, Salmacis virgulata scattered over the periphery of Dhanushkodi beach, was observed on February 13, 2019. More than 100 numbers of recently dead and dying specimens were found within a 10 m2 area on the sandy beach. Beach profiles indicated several hundreds of exoskeletons of previously dead S. virgulata were washed ashore and buried in sand and withering seagrass. The causative agent responsible for mass mortality of S. virgulata is yet to be discovered. However, observations on wave approach toward shore indicated possible evidence that it could be due to a combination of strong nearshore waves and currents. This observation raises a critical research concern to investigate etiology of S. virgulata for species conservation. [ABSTRACT FROM AUTHOR]

Marine heat waves (MHWs) are periods of extremely high seawater temperature that affect marine ecosystems in several ways. Anthozoans (corals and gorgonians) and Porifera (sponges) are usually among the taxa most affected by MHWs. Both are holobiont entities that form complex interactions with a wide range of microbes, which are an essential part of these organisms and play key roles in their health status. Here, we determine microbial community changes suffered in two corals (Cladocora caespitosa and Oculina patagonica), one gorgonian (Leptogorgia sarmentosa) and one sponge (Sarcotragus fasciculatus) during the 2015 MHW. The microbial communities were different among hosts and displayed shifts related to host health status, with a higher abundance in necrosed tissues of Ruegeria species or of potential pathogens like Vibrio. We also carry out a meta-analysis using 93 publicly accessible 16S rRNA gene libraries from O. patagonica, C. caespitosa and L. sarmentosa to establish a Mediterranean core microbiome in these species. We have identified one Ruegeria OTU that maintained a stable and consistent association with these species, which was also related to tissue necrosis in their hosts. Therefore, Ruegeria sp. could play an important and still underexplored role in the health status of its hosts. [ABSTRACT FROM AUTHOR]

Background: Ranavirus is an emerging infectious disease which has been linked to mass mortality events in various amphibian species. In this study, we document the first mass mortality event of an adult population of Dybowski's brown frogs (Rana dybowskii), in 2017, within a mountain valley in South Korea. Results: We confirmed the presence of ranavirus from all collected frogs (n = 22) via PCR and obtained the 500 bp major capsid protein (MCP) sequence from 13 individuals. The identified MCP sequence highly resembled Frog virus 3 (FV3) and was the same haplotype of a previously identified viral sequence collected from Huanren brown frog (R. huanrenensis) tadpoles in South Korea. Human habitat alteration, by recent erosion control works, may be partially responsible for this mass mortality event. Conclusion: We document the first mass mortality event in a wild Korean population of R. dybowskii. We also suggest, to determine if ranavirus infection is a threat to amphibians, government officials and researchers should develop continuous, country-wide, ranavirus monitoring programs of Korean amphibian populations. [ABSTRACT FROM AUTHOR]

• Poultry carcass parts were stabilized during 30 days of thermophilic composting. • Mass loss was nearly 100% for hearts and livers and 30–40% for skin parts. • Dimethyl disulfide (DMDS) and trisulfide (DMTS) contributed 81–88% of VOC fluxes. • Odor was dominated by methanethiol, DMDS, benzaldehyde, pentanoic acid and NH 3. • DMDS/DMTS ratio above 10–13 may indicate sufficient carcass stabilization. Short-term on-site composting of poultry carcasses and broiler litter (BL) is considered as a feasible technology for pathogen elimination during events of mass mortality in poultry houses. However, factors related to mass losses and physical transformation of the poultry carcass, and associated emissions of volatile organic compounds (VOCs) and odors, have not been thoroughly evaluated. This study aims to characterize the degradation of separated carcass parts co-composted with BL and the associated air emissions during 30 days of enclosed composting at 50 °C with constant aeration. The study was carried out in lab-scale simulators using five mixtures containing feathers, rib bones, skins, breast muscles, and hearts and livers, prepared at a 1:2 volumetric ratio (carcass:BL). Dry mass losses reached 59.5, 41.1, 60.8 and 103.5% (based on weight) or 48.4, 29.6, 49.7, and 94.8% (based on CO 2 -C and NH 3 -N emissions), for rib bones, skins, breast muscles, and hearts and livers, respectively. Visually, most of the carcass parts were degraded, and the typical carcass odor had disappeared by the end of the 30 days. Out of 24 VOCs, dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) contributed 80.7–88.3% of the total VOC flux, considering the partial contribution of each part to the emissions involved with the whole carcass. DMDS, DMTS, benzaldehyde, methanethiol, pentanoic acid, and NH 3 , contributed 90.5–97.9% of the odor activity values during composting. DMDS/DMTS ratio is suggested as a potential biomarker of stabilization and readiness of the compost for transportation toward further treatment or safe burial. [ABSTRACT FROM AUTHOR]

The population of Pinna nobilis (Linnaeus, 1758) has been severely damaged, especially by the effect of the disease, in addition to the causes such as fishing activities, overexploitation, environmental pollution, habitat degradation, tourism, and human impacts. Particularly, Haplosporidium pinnae caused gigantic destruction in the P. nobilis population. Accordingly, the present study aimed to determine the current status of the P. nobilis populations in the Çanakkale Strait. Samplings were carried out between July and August 2020 at 9 different stations in the Çanakkale Strait. The results revealed that mass mortality was observed at the two stations (Abide Beach and Kumkale Village Beach) located near the Aegean Sea. On the other hand, it has been determined that the lowest mortality rate (9.62%) has been found at Ilgardere station. Juvenile individuals have been observed in healthy and uninfected populations with high survival rates. This paper is the first document on the spatial distribution of P. nobilis in Çanakkale Strait. Therefore, the P. nobilis population should be continuously monitored to ensure the sustainability of the species. [ABSTRACT FROM AUTHOR]

Scavengers play an important role in nutrient recycling and disease control, and this role may be particularly critical after mass mortality events, such as those caused by epidemics, culling, or natural disasters. Current work on scavenger ecology has focused on use of single carcasses, but behaviors are likely to be different at mass mortality events, in which high resource abundance can prolong the spatial and temporal availability of carcasses. Little is currently known about how scavengers respond to large die‐offs and understanding scavenger use and succession patterns at mass mortality events has important implications for disease ecology. We used photographic time series and river‐side surveys of scavengers using carcasses to investigate scavenger use and succession on wildebeest carcasses that resulted from annual mass drownings in the Mara River, Kenya. In addition, we used telemetry data for tagged avian scavengers to assess individual use of mass drownings. Density of avian scavengers per carcass was almost two orders of magnitude lower at mass drownings than has been documented previously for single carcasses on land. Scavengers demonstrated patterns of temporal resource partitioning, with large‐bodied avian scavengers more common initially, followed by small‐bodied avian scavengers, and then by insectivorous birds and non‐avian scavengers. Avian scavengers also differed in daily activity patterns, with marabou storks more common in the morning and late afternoon and white‐backed and Rüppell's vultures more common mid‐day. Telemetry data indicated that approximately half of tagged vultures used mass drowning events but only spent a small proportion of their time there, suggesting that competition still plays an important role in scavenger dynamics at mass mortality events and that the rewards of such abundant resources may be offset by the risk of foraging in the river. Further research on scavenger behavior during mass mortality events is needed to better understand the role of scavengers in decomposition of carcasses and disease control during these events. [ABSTRACT FROM AUTHOR]

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The Akoya pearl oyster ( Pinctada fucata (Gould)) is the most important species for pearl cultivation in Japan. Mass mortality of 0-year-old juvenile oysters and anomalies in adults, known as summer atrophy, have been observed in major pearl farming areas during the season when seawater temperatures exceed about 20 °C since 2019. In this study, we identified a novel birnavirus as the pathogen of summer atrophy and named it Pinctada birnavirus (PiBV). PiBV was first presumed to be the causative agent when it was detected specifically and frequently in the infected oysters in a comparative metatranscriptomics of experimentally infected and healthy pearl oysters. Subsequently, the symptoms of summer atrophy were reproduced by infection tests using purified PiBV. Infection of juvenile oysters with PiBV resulted in an increase in the PiBV genome followed by the atrophy of soft body and subsequent mortality. Immunostaining with a mouse antiserum against a recombinant PiBV protein showed that the virus antigen was localized mainly in the epithelial cells on the outer surface of the mantle. Although the phylogenetic analysis using maximum likelihood method placed PiBV at the root of the genus Entomobirnavirus, the identity of the bi-segmented, genomic RNA to that of known birnaviruses at the full-length amino acid level was low, suggesting that PiBV forms a new genus. The discovery of PiBV will be the basis for research to control this emerging disease., Competing Interests: The authors declare that they have no competing interests., (© 2024 Matsuyama et al.)

A devastating mass mortality event (MME) very likely caused by the protozoan Haplosporidium pinnae first detected in 2016 in the Western Mediterranean Sea, is pushing the endemic bivalve Pinna nobilis to near extinction. Populations recovery, if possible, will rely on larval dispersal from unaffected sites and potential recolonization through recruitment of resistant juveniles. To assess the impact of the MME on the species’ larval recruitment, an unprecedented network of larval collector stations was implemented over several thousands of kilometers along the Western Mediterranean coasts during the 3 years after the onset of the MME. The findings of this network showed a generalized disruption in recruitment with dramatic consequences for the recovery of the species. However, there were exceptions to this pattern and recruits were recorded in a few sites where the resident population had been decimated. This hints to the importance of unaffected populations as larval exporting sources and the role of oceanographic currents in larval transport in the area, representing a beacon of hope in the current extremely worrying scenario for this emblematic species.

Animal carcasses provide an ephemeral pulse of nutrients for scavengers that use them. Carcass sites can increase species interactions and/or ephemeral, localized landscapes of fear for prey within the vicinity. Few studies have applied the landscape of fear to carcasses. Here, we use a mass die-off of reindeer caused by lightning in Norway to test whether rodents avoided larger scavengers (e.g. corvids and fox). We used the presence and abundance of faeces as a proxy for carcass use over the course of 2 years and found that rodents showed the strongest avoidance towards changes in raven abundance (β = −0.469, s.e. = 0.231, p-value = 0.0429), but not fox, presumably due to greater predation risk imposed by large droves of raven. Moreover, the emergence of rodent occurrence within the carcass area corresponded well with the disappearance of raven during the second year of the study. We suggest that carcasses have the potential to shape the landscape of fear for prey, but that the overall effects of carcasses on individual fitness and populations of species ultimately depend on the carcass regime, e.g. carcass size, count, and areal extent, frequency and the scavenger guild. We discuss conservation implications and how carcass provisioning and landscapes of fear could be potentially used to manage populations and ecosystems, but that there is a gap in understanding that must first be bridged.

Caribbean populations of the long-spined black sea urchin Diadema antillarum Philippi were decimated by a disease-induced mass mortality in the early 1980’s. The present study provides an updated status of the D. antillarum recovery and population characteristics in La Parguera Natural Reserve, Puerto Rico. The last detailed study to assess population recovery in 2001, indicated a slow, and modest recovery, albeit densities remained far below pre-mass mortality levels. Population densities were assessed along three depth intervals in six reef localities and one depth in three lagoonal sea-grass mounds using ten 20 m2 (10 × 2 m) belt-transects at each depth interval. Most of these were previously surveyed in 2001. All individuals encountered along the belt transects were sized in situ with calipers and rulers to characterize the size (age) structure of each population and get insight into the urchin’s population dynamics and differences across localities in the area. Habitat complexity (rugosity) was assessed in all depth intervals. No significant differences in population densities between reef zones (inner shelf and mid-shelf) were observed, but significantly higher densities were found on shallow habitats (12 m; 0.04 ± 0.08 ind/m2) reef habitats in almost all sites surveyed. Habitat complexity had the greatest effect on population densities at all levels (site, zone and depth) with more rugose environments containing significantly higher densities and wider size structures. Comparison between survey years revealed that D. antillarum populations have not increased since 2001, and urchins seem to prefer shallower, more complex and productive areas of the reef. Populations were dominated by medium to large (5–9 cm in test diameter) individuals and size-frequency distributions indicated that smaller juveniles were virtually absent compared to 2001, which could reflect a recruitment-limited population and explain in part, the lack of increase in population densities. The limited temporal scale of this study, high horizontal movement of individuals along the complex, shallower reef and inshore habitats could also explain the general decline in mean densities. Other extrinsic factors affecting reproductive output and/or succesful recruitment and survival of juveniles likely contribute to the high variablility in population densities observed over time.

Following the Mass Mortality Events (MMEs) of the pen shell P. nobilis in Campania region and Sicily, a survey of moribund P. nobilis specimens was also conducted in other Italian regions (Campania, Tuscany, Sardinia, and Apulia) and Spain (Catalunya). Histopathological and molecular examination of 27 specimens of P. nobils revealed different types of pathogens associated with tissue lesions, morbidity and mortality. Presence of Mycobacterium, Vibrio species, Haplosporidium pinnae and Perkinsus sp. were detected, differently distributed into the areas. The Mycobacterium sp., previously reported in Campania and Sicily samples, was observed in all the analyzed areas and individuals, associated to systemic inflammatory lesions. In Spain, H. pinnae was observed in 36% of cases, always associated to the Mycobacterium sp. Molecular study using hsp65 genes and Internal Transcriber Spacer ITS support that a new species of Mycobacteria is infecting P. nobilis, close to M. triplex and belonging to the group of M. simiae complex with M. sherrisi. Presence of Perkinsus spp. resembling P. mediterraneus was observed in 2 out of 13 Italian individuals whose presence should be addressed as potential risk for shellfish aquaculture of the area. Vibrio spp. were also detected in some case. The preliminary results of this study suggest that Mycobacterium sp., Vibrio spp., H. pinnae and Perkinsus sp. cooperate to disease pathogenesis, being Mycobacterium and Haplosporidium most of the time involved. Vigilant inspection of those areas where MME is now starting, along with continuous systematic surveys, are crucial to define the spatiotemporal progress of mortality and the role of every single pathogen in the disease outcome.

Background: Each death event can be characterized by its associated microbes – a living community of bacteria composed of carcass, soil, and insect-introduced bacterial species – a necrobiome. With the possibility for close succession of these death events, it may be beneficial to characterize how the magnitude of an initial death event may impact the decomposition and necrobiomes of subsequent death events in close proximity. In this paper we hope to characterize the microbial communities associated with a proximate subsequent death event, and distinguish any changes within those communities based on the magnitude of an initial death event and the biomass of preexisting carcass (es) undergoing decomposition. For this experiment, 6 feral swine carcasses in containers were placed in the vicinity of preexisting and ongoing carcass decomposition at sites of three different scales of decomposing carcass biomass. Swab samples were collected from the skin and eye sockets of the container pigs and subjected to 16 s rRNA sequencing and OTU assignment. Results: PERMANOVA analysis of the bacterial taxa showed that there was no significant difference in the bacterial communities based on initial mortality event biomass size, but we did see a change in the bacterial communities over time, and slight differences between the skin and ocular cavity communities. Even without soil input, necrobiome communities can change rapidly. Further characterization of the bacterial necrobiome included utilization of the Random Forest algorithm to identify the most important predictors for time of decomposition. Sample sets were also scanned for notable human and swine-associated pathogens. Conclusions: The applications from this study are many, ranging from establishing the environmental impacts of mass mortality events to understanding the importance of scavenger, and scavenger microbial community input on decomposition. [ABSTRACT FROM AUTHOR]

Mass mortalities in Egyptian hatchery-reared Nile tilapia (Oreochromis niloticus) fries have negatively impacted the livelihood of fish farmers for the past 3 years due to fish loss (up to 70%), feed waste, and loss of job opportunities. An investigation into possible viral causes of massive die-offs in tilapia during 2018–2019 identified nervous necrosis virus (NNV) strains phylogenetically related to red-spotted grouper NNV. Clinical signs and gross pathology of naturally infected fish were consistent with classical NNV infections. Electron micrographs revealed virions in the retina and brain. NNV RNA was also detected in the brood stocks' brains and ovaries. Experimental infection of NNV-free fries resulted in 100% morbidity and mortality. Since this is the first report of VNN-outbreaks in African tilapia, different aspects of viral epidemiology and possible ways to break the epidemic wave and prevent future interspecies transmission events are discussed. [ABSTRACT FROM AUTHOR]

An unprecedented irruption of thousands of Razorbills Alca torda into Florida in winter 2012/13 was followed by a "wreck" of Razorbills and Atlantic Puffins Fratercula arctica in outer Cape Cod, Massachusetts, in January-March 2013. We describe these events using citizen-science sources (eBird and beached-bird surveys) and band recoveries, then we discuss them in relation to extreme weather and oceanographic change. We explored effects on likely source populations using census and monitoring data, along with possible contributions from population increases, reduced food supply, and extreme weather. Winter 2012/13 followed a marine heatwave throughout the northwest Atlantic, whose effects included reduced availability of plankton. We attribute the irruption of Razorbills into Florida partly to delayed effects of Hurricane Sandy, which disrupted their coastal habitat sufficiently to cause starving birds to move south on the Labrador Current as far as Florida. Despite the continuation of anomalously warm ocean temperatures in subsequent years and a reduction in plankton communities in the Bay of Fundy and Gulf of Maine that continues to date, no comparable events have been recorded in subsequent winters; this supports our theory that the delayed effects of Hurricane Sandy contributed to these wrecks. We highlight the power of these datasets to detect and to investigate birds' responses to extreme and anomalous conditions, which in turn provides insight into the dynamics of rapidly changing ecological systems. [ABSTRACT FROM AUTHOR]

Mass mortality of bivalve clams along with some other marine fauna was observed during the month of May 2016, mainly consisting of the clams (Mactra aequisulcata) of family Veneridae surfaced over the Clifton coast. The occurrence of mass mortality of the venerid clams Mactra aequisulcata and other marine life has been studied due to the toxicity of chlorinated hydrocarbons (DDTs, HCHs, hexa chloro benzene (HCB), chlordane, dieldrin (4-chlorophenyl), methanol (TCPMOH) and heptachlor epoxide and polychlorinated biphenyls (PCBs). Significant compositional characteristics of PCBs and DDTs were found in all dead clams and other fauna including fish (Johnius carutta), crabs (Portunus pelagicus), gastropods (Babylonia spirata), bivalves (Anadara antiquata), (Mactra aequisulcata) and the pen shell (Atrina pectinata) from Karachi coast, Pakistan. Mean concentrations (ranges) of organochlorine pesticides (OCPs) in crab (Portunus pelagicus) and fish samples were 1.1 (<0.01-1.5), 0.22 (<0.01-1.1) and 0.14 (<0.01-1.3)/µg/g. Those in, bivalves (Anadara antiquata) and pen shell (Atrina pectinata), clams (Mactra aequisulcata) were 0.09 (<0.02-1.2), 0.22 (<0.02-1.3)/µg and 0.13 (<0.01-0.27), respectively. The heptachlor epoxide was found in highest concentration in clam samples (25.00 ± 30.92) µg/g, (wet weight) however, in bivalves, (2.30 µg/g, (wet weight), which were higher than those in other gastropods. Polychlorinated biphenyls (PCBs) concentrations were also measured in the same samples of gastropods (Babylonia spirata), fish (Johnius carutta), crab (Portunus pelagicus), clams (Mactra aequisulcata), bivalves (Anadara antiquata) and the pen shell (Atrina pectinata) to determine the possible cause of mass mortality. The DDT to metabolites (DDD & DDE) concentration ratios exceeded upto 1.0 in the sessile fauna that is clams (Mactra aequisulcata) and the pen shell (Atrina pectinata) from Karachi coast. These organisms also exhibited dichloro diphenyl trichloroethane (DDT) inputs, whereas dichloro diphenyl trichloroethane (DDD) was found to be in degraded component and PCBs were generally in low concentrations. The concentrations of DDTs were higher than the ERL guidelines in the coastal areas of Karachi, suggesting that there is potential of ecological risk present in the prevailing environment. [ABSTRACT FROM AUTHOR]

Recurrent sea urchin mass mortality has recently affected eastern Atlantic populations of the barren‐forming sea urchin Diadema africanum. This new episode of die‐off affords the opportunity to determine common meteorological and oceanographic conditions that may promote disease outbreaks. The population dynamics of this sea urchin species are well known—urchin barrens have persisted for many decades along most of the coastlines off the archipelagos of Madeira, Selvages, and the Canary Islands, where they limit macroalgae biomass growth. However, this new and explosive mortality event decimated the sea urchin population by 93% on Tenerife and La Palma Islands. Two severe episodes of southwestern rough sea that led to winter storms, in February 2010 (Xynthia) and February 2018 (Emma), preceded both mass mortality events. The autumn and winter months of those years were anomalous and characterized by swells with an average wave height above 2 m that hit the south and southwest sides of the islands. The amoeba Paramoeba brachiphila was the only pathogen isolated this time from the moribund and dead sea urchins, suggesting that the amoeba was the primary cause of the mortality. This new sea urchin die‐off event supports the "killer‐storm" hypothesis that has been already described for western Atlantic coasts. These anomalous southwest storms during winters generate pronounced underwater sediment movement and large‐scale vertical mixing, detected in local tide gauge, which may promote paramoebiasis. This study presents valuable insights about climate‐mediated changes in disease frequency and its impacts on the future of coastal marine ecosystems in the Atlantic. [ABSTRACT FROM AUTHOR]

Infectious disease emergence has increased significantly over the last 30 years, with mass mortality events (MMEs) associated with epizootics becoming increasingly common. Factors influencing these events have been widely studied in terrestrial systems, but remain relatively unexplored in marine mammals. Infectious disease‐induced MMEs (ID MMEs) have not been reported ubiquitously among marine mammal species, indicating that intrinsic (host) and/or extrinsic (environmental) ecological factors may influence this heterogeneity. We assess the occurrence of ID MMEs (1955–2018) across extant marine mammals (n = 129) in relation to key life‐history characteristics (sociality, trophic level, habitat breadth) and environmental variables (season, sea surface temperature [SST] anomalies, El Niño occurrence). Our results show that ID MMEs have been reported in 14% of marine mammal species (95% CI 9%–21%), with 72% (n = 36; 95% CI 56%–84%) of these events caused predominantly by viruses, primarily morbillivirus and influenza A. Bacterial pathogens caused 25% (95% CI 14%–41%) of MMEs, with only one being the result of a protozoan pathogen. Overall, virus‐induced MMEs involved a greater number of fatalities per event compared to other pathogens. No association was detected between the occurrence of ID MMEs and host characteristics, such as sociality or trophic level, but ID MMEs did occur more frequently in semiaquatic species (pinnipeds) compared to obligate ocean dwellers (cetaceans; χ2 = 9.6, p =.002). In contrast, extrinsic factors significantly influenced ID MMEs, with seasonality linked to frequency (χ2 = 19.85, p =.0002) and severity of these events, and global yearly SST anomalies positively correlated with their temporal occurrence (Z = 3.43, p = 2.7e‐04). No significant association was identified between El Niño and ID MME occurrence (Z = 0.28, p =.81). With climate change forecasted to increase SSTs and the frequency of extreme seasonal weather events, epizootics causing MMEs are likely to intensify with significant consequences for marine mammal survival. [ABSTRACT FROM AUTHOR]

Causes of Potamogeton crispus population decline in the late spring and early summer are not fully understood. Given that strong UV-B radiation can penetrate the water column and damage aquatic organisms, it may be a key factor in the P. crispus decline. In this study, adult P. crispus plants were exposed to different intensities of UV-B radiation for 6 hours every day, the control group was only exposed to UV-A and photosynthetically active radiation. All groups were exposed to UV-A and photosynthetically active radiation at the same intensity. We monitored the morphological changes, and physiological and biochemical indexes. The results showed that plant height, internode length, and leaf area decreased with corresponding increases in radiation intensity. Additionally, photosynthetic pigment content could be improved with low-intensity UV-B radiation (<10.8 kJ/m²), inhibited with continuous radiation, and decreased by high-intensity of UV-B radiation (>10.8 kJ/m²). Catalase activity improved by short-term radiation, but inhibited by long-term radiation. Superoxide dismutase activity increased gradually with longer irradiation time. The malonaldehyde content increased at the beginning but then decreased with continuing radiation. These results suggest that UV-B radiation may contribute to the mass mortality of P. crispus in late spring and early summer. [ABSTRACT FROM AUTHOR]

Recent field survey in Ranipur Wildlife Sanctuary (RWS), Chitrakoot, Uttar Pradesh, India amazed us to locate several bird carcasses on the railway track and prompted to identify the species and possible reasons of mortality from the deteriorated body remains. Surprisingly, DNA analysis with conserved mitochondrial genes i.e. Cytochrome b (Cyt b) and 16S rRNA, identified carcass originated from a Critically Endangered Red-headed Vulture (RHV: Sarcogyps calvus). The present study exhibits mtDNA based identification to be very efficient in species identification and raises concern for the mortality of RHV due to the possible bird-train collisions. We hope this study will get attention of the wildlife conservationists, forest officials and administrators in order to gather long term monitoring data on the mortality of RHV and other animals by train-hits or associated factors and suggest conservation strategies for wildlife management in and around RWS. [ABSTRACT FROM AUTHOR]

This chapter is focused on two vulnerable bivalve sessile species present in the Cabrera National Park, Pinna nobilis and Pinna rudis. Both species are protected by law and are vulnerable to many impacts. Prior to the creation of the park, the presence of these species was known in the waters of Cabrera but the presence was occasional. A summary of the knowledge acquired during the last years in aspects such as density and distribution of populations, habitat and depth preferences, population demography of the two species (recruitment rate, mortality rate and net growth rate); the size structure, age, and growth rate of both species are provided. In addition, in the case of P. nobilis we investigated the larval establishment and inference of the time of implantation in the study of gonad development, isotopic level of d13C and d15N, capacity as an indicator of heavy metals, antioxidant response, markers of oxidative damage and production of reactive oxygen species. It emphasizes the importance that the Park had for these two species and the result of the effectiveness of more than 20 years of effective protection since the populations of Cabrera presented one of the highest density of all the Mediterranean for both species. The mass mortality event that in a few months has reached Cabrera with catastrophic consequences for the endemic species Pinna nobilis is also discussed. Finally, all this information is discussed in a global context highlighting key points for management strategies. [ABSTRACT FROM AUTHOR]

Beginning in 2013, sea stars throughout the Eastern North Pacific were decimated by wasting disease, also known as "asteroid idiopathic wasting syndrome" (AIWS) due to its elusive aetiology. The geographic extent and taxonomic scale of AIWS meant events leading up to the outbreak were heterogeneous, multifaceted, and oftentimes unobserved; progression from morbidity to death was rapid, leaving few tell‐tale symptoms. Here, we take a forensic genomic approach to discover candidate genes that may help explain sea star wasting syndrome. We report the first genome and annotation for Pisaster ochraceus, along with differential gene expression (DGE) analyses in four size classes, three tissue types, and in symptomatic and asymptomatic individuals. We integrate nucleotide polymorphisms associated with survivors of the wasting disease outbreak, DGE associated with temperature treatments in P. ochraceus, and DGE associated with wasting in another asteroid Pycnopodia helianthoides. In P. ochraceus, we found DGE across all tissues, among size classes, and between asymptomatic and symptomatic individuals; the strongest wasting‐associated DGE signal was in pyloric caecum. We also found previously identified outlier loci co‐occur with differentially expressed genes. In cross‐species comparisons of symptomatic and asymptomatic individuals, consistent responses distinguish genes associated with invertebrate innate immunity and chemical defence, consistent with context‐dependent stress responses, defensive apoptosis, and tissue degradation. Our analyses thus highlight genomic constituents that may link suspected environmental drivers (elevated temperature) with intrinsic differences among individuals (age/size, alleles associated with susceptibility) that elicit organismal responses (e.g., coelomocyte proliferation) and manifest as sea star wasting mass mortality. [ABSTRACT FROM AUTHOR]