Geology topics
Thierry M. Work
Publications and source records attributed to Thierry M. Work.
Report of the technical expert workshop: Developing recommendations for field response, captive management, and rehabilitation of sea turtles with fibropapillomatosis
Fibropapillomatosis (FP) is a disease of sea turtles that primarily manifests as tumors of the skin. Strandings of green turtles with this disease have dramatically increased in the Southeast U.S. over the last decade, necessitating a review of various practices related to the capture, handling, and treatment of afflicted turtles. NOAA and USFWS hosted a workshop in St. Petersburg, Florida on September 6, 2017 to seek input on the development of recommendations to address the following key issues regarding green turtles with FP: 1) disposition when encountered under various circumstances (e.g., strandings, research activities, incidental capture, opportunistic observations); 2) rehabilitation and release; 3) response options if rehabilitation capacity is exceeded; and 4) biosecurity measures to prevent anthropogenic spread of the disease. Federal and state resource agency staff and rehabilitation veterinarians were invited to this workshop to provide input for these recommendations. A review of rehabilitation practices and outcome was shared with participants to inform discussions related to rehabilitation and stranding response. Draft recommendations were prepared for the meeting and participants were asked to share their opinions during moderated discussions and via a written feedback instrument. This input was considered and applied to amend the recommendations, which were also peer-reviewed by six additional veterinarians and a stranding biologist with expertise in sea turtles,rehabilitation medicine, and fibropapillomatosis. The intended use for the completed Fibropapillomatosis and Sea Turtles: Recommendations for Field Response, Captive Management, and Rehabilitation is to assist resource agencies with management planning and decisions related to green turtles with FP and to inform relevant aspects of policy, permits, and authorizations under federal and state regulations.
Exploring the pathology of an epidermal disease affecting a circum-Antarctic sea star
Over the past decade, unusual mortality outbreaks have decimated echinoderm populations over broad geographic regions, raising awareness globally of the importance of investigating such events. Echinoderms are key components of marine benthos for top-down and bottom-up regulations of plants and animals; population declines of these individuals can have significant ecosystem-wide effects. Here we describe the first case study of an outbreak affecting Antarctic echinoderms and consisting of an ulcerative epidermal disease affecting ~10% of the population of the keystone asteroid predator Odontaster validus at Deception Island, Antarctica. This event was first detected in the Austral summer 2012–2013, coinciding with unprecedented high seawater temperatures and increased seismicity. Histological analyses revealed epidermal ulceration, inflammation, and necrosis in diseased animals. Bacterial and fungal alpha diversity was consistently lower and of different composition in lesioned versus unaffected tissues (32.87% and 16.94% shared bacterial and fungal operational taxonomic units OTUs respectively). The microbiome of healthy stars was more consistent across individuals than in diseased specimens suggesting microbial dysbiosis, especially in the lesion fronts. Because these microbes were not associated with tissue damage at the microscopic level, their contribution to the development of epidermal lesions remains unclear. Our study reveals that disease events are reaching echinoderms as far as the polar regions thereby highlighting the need to develop a greater understanding of the microbiology and physiology of marine diseases and ecosystems health, especially in the era of global warming.
Managing an invasive corallimorph at Palmyra Atoll National Wildlife Refuge, Line Islands, Central Pacific
In 2007, a phase shift from corals to corallimorpharians (CM) centered around a shipwreck was documented at Palmyra Atoll, Line Islands. Subsequent surveys revealed CM to be overgrowing the reef benthos, including corals and coralline algae, potentially placing coral ecosystems in the atoll at risk. This prompted the U.S. Fish and Wildlife Service, the lead management agency of the atoll, to remove the shipwreck. Subsequent surveys showed reductions in CM around the ship impact site. We explain patterns of spread of the CM in terms of both life history and local currents and show with a pilot study that pulverized bleach may be an effective tool to eradicate CM on a local scale. If applied strategically, particularly in heavily infested (> 66% cover) areas, active intervention such as this could be an effective management tool to reduce CM impact on localized areas and decrease colonization rate of remaining reefs. This is the first documentation of the response of an invasive cnidarian to shipwreck removal. While this was a singular event in Palmyra, the spatial and temporal patterns of this invasion and the eradications lessons described herein, are useful for anticipating and controlling similar situations elsewhere.
Genomic evolution, recombination, and inter-strain diversity of chelonid alphaherpesvirus 5 from Florida and Hawaii green sea turtles with fibropapillomatosis
Chelonid alphaherpesvirus 5 (ChHV5) is a herpesvirus associated with fibropapillomatosis (FP) in sea turtles worldwide. Single-locus typing has previously shown differentiation between Atlantic and Pacific strains of this virus, with low variation within each geographic clade. However, a lack of multi-locus genomic sequence data hinders understanding of the rate and mechanisms of ChHV5 evolutionary divergence, as well as how these genomic changes may contribute to differences in disease manifestation. To assess genomic variation in ChHV5 among five Hawaii and three Florida green sea turtles, we used high-throughput short-read sequencing of long-range PCR products amplified from tumor tissue using primers designed from the single available ChHV5 reference genome from a Hawaii green sea turtle. This strategy recovered sequence data from both geographic regions for approximately 75% of the predicted ChHV5 coding sequences. The average nucleotide divergence between geographic populations was 1.5%; most of the substitutions were fixed differences between regions. Protein divergence was generally low (average 0.08%), and ranged between 0 and 5.3%. Several atypical genes originally identified and annotated in the reference genome were confirmed in ChHV5 genomes from both geographic locations. Unambiguous recombination events between geographic regions were identified, and clustering of private alleles suggests the prevalence of recombination in the evolutionary history of ChHV5. This study significantly increased the amount of sequence data available from ChHV5 strains, enabling informed selection of loci for future population genetic and natural history studies, and suggesting the (possibly latent) co-infection of individuals by well-differentiated geographic variants.
Validation of ATR FT-IR to identify polymers of plastic marine debris, including those ingested by marine organisms
Polymer identification of plastic marine debris can help identify its sources, degradation, and fate. We optimized and validated a fast, simple, and accessible technique, attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR), to identify polymers contained in plastic ingested by sea turtles . Spectra of consumer good items with known resin identification codes #1–6 and several #7 plastics were compared to standard and raw manufactured polymers. High temperature size exclusion chromatography measurements confirmed ATR FT-IR could differentiate these polymers. High-density (HDPE) and low-density polyethylene (LDPE) discrimination is challenging but a clear step-by-step guide is provided that identified 78% of ingested PE samples. The optimal cleaning methods consisted of wiping ingested pieces with water or cutting. Of 828 ingested plastics pieces from 50 Pacific sea turtles, 96% were identified by ATR FT-IR as HDPE, LDPE, unknown PE, polypropylene (PP), PE and PP mixtures, polystyrene , polyvinyl chloride , and nylon.
Human induced trauma and directed take inhibits sea turtle recovery in the Commonwealth of the Northern Mariana Islands
Sea turtle conservation is often hindered by the lack of reliable information on population status and threats due to sampling difficulties of these highly migratory reptiles that live in remote and data-poor locations. This paper summarizes more than a decade of stranding recoveries (live and dead turtles) on the islands of Saipan and Tinian, Commonwealth of the Northern Mariana Islands (CNMI), to obtain baseline information on the primary threats to sea turtles in the CNMI. Gross external examination and necropsy of dead turtles was used to infer primary cause of stranding of 89 sea turtles (92.1% green ( Chelonia mydas ), 5.6% hawksbill ( Eretmochelys imbricata ), 1.1% olive ridley ( Lepidochelys olivacea ), and 1% unknown). Of these stranding recoveries, 80.9% were juveniles, 15.7% were adults, and 3.4% were unknown. Trauma related to illegal human take was the primary cause of stranding and accounted for 79% of CNMI sea turtle injuries and mortalities. The remaining 21% of strandings were attributed to (in rank order): marine debris entanglement, shark bite, boat strike, emaciation, and infectious disease. This study provides the first comprehensive characterization of cause-specific sea turtle injury and mortality in CNMI, described within the unique socio-cultural and historical dynamics of the region. Culturally-relevant suggestions for management are provided that may help address the primary threat to CNMI sea turtles.
Investigation of plastic debris ingestion by four species of sea turtles collected as bycatch in pelagic Pacific longline fisheries
Ingestion of marine debris is an established threat to sea turtles. The amount, type, color and location of ingested plastics in the gastrointestinal tracts of 55 sea turtles from Pacific longline fisheries from 2012 to 2016 were quantified, and compared across species, turtle length, body condition, sex, capture location, season and year. Six approaches for quantifying amounts of ingested plastic strongly correlated with one another and included: number of pieces, mass, volume and surface area of plastics, ratio of plastic mass to body mass, and percentage of the mass of gut contents consisting of plastic. All olive ridley (n = 37), 90% of green (n = 10), 80% of loggerhead (n = 5) and 0% of leatherback (n = 3) turtles had ingested plastic; green turtles ingested significantly more than olive ridleys. Most debris was in the large intestines. No adverse health impacts (intestinal lesions, blockage, or poor body condition) due directly to plastic ingestion were noted.
Persistent organic pollutants in fat of three species of Pacific pelagic longline caught sea turtles: Accumulation in relation to ingested plastic marine debris
In addition to eating contaminated prey, sea turtles may be exposed to persistent organic pollutants (POPs) from ingesting plastic debris that has absorbed these chemicals. Given the limited knowledge about POPs in pelagic sea turtles and how plastic ingestion influences POP exposure, our objectives were to: 1) provide baseline contaminant levels of three species of pelagic Pacific sea turtles; and 2) assess trends of contaminant levels in relation to species, sex, length, body condition and capture location. In addition, we hypothesized that if ingesting plastic is a significant source of POP exposure, then the amount of ingested plastic may be correlated to POP concentrations accumulated in fat. To address our objectives we compared POP concentrations in fat samples to previously described amounts of ingested plastic from the same turtles. Fat samples from 25 Pacific pelagic sea turtles [2 loggerhead ( Caretta caretta ), 6 green ( Chelonia mydas ) and 17 olive ridley ( Lepidochelys olivacea ) turtles] were analyzed for 81 polychlorinated biphenyls (PCBs), 20 organochlorine pesticides, and 35 brominated flame-retardants. The olive ridley and loggerhead turtles had higher ΣDDTs (dichlorodiphenyltrichloroethane and metabolites) than ΣPCBs, at a ratio similar to biota measured in the South China Sea and southern California. Green turtles had a ratio close to 1:1. These pelagic turtles had lower POP levels than previously reported in nearshore turtles. POP concentrations were unrelated to the amounts of ingested plastic in olive ridleys, suggesting that their exposure to POPs is mainly through prey. In green turtles, concentrations of ΣPCBs were positively correlated with the number of plastic pieces ingested, but these findings were confounded by covariance with body condition index (BCI). Green turtles with a higher BCI had eaten more plastic and also had higher POPs. Taken together, our findings suggest that sea turtles accumulate most POPs through their prey rather than marine debris.
In-vitro replication of Chelonid herpesvirus 5 in organotypic skin cultures from Hawaiian green turtles (Chelonia mydas)
Fibropapillomatosis (FP) is a tumor disease of marine turtles associated with Chelonid herpesvirus 5 (ChHV5) that has historically been refractory to growth in tissue culture. Here, we show for the first time de novo formation of ChHV5-positive intranuclear inclusions in cultured green turtle cells, which is indicative for active lytic replication of the virus. The minimal requirements to achieve lytic replication in cultured cells included 1) either in-vitro culturing of ChHV5-positive tumor biopsies (plugs) or organotypic cultures (rafts) consisting of ChHV5-positive turtle fibroblasts in collagen rafts seeded with turtle keratinocytes and 2) keratinocyte maturation induced by raising raft or biopsy cultures to the air-liquid interface. Virus growth was confirmed by detailed electron microscopic studies revealing intranuclear sun-shaped capsid factories, tubules, various stages of capsid formation, nuclear export by budding into the perinuclear space, tegumentation, and envelopment to complete de novo virus production. Membrane synthesis was also observed as a sign for active viral replication. Interestingly, cytoplasmic particles became associated with keratin filaments, a feature not seen in conventional monolayer cell cultures where most studies of herpesvirus replication have been performed. Our findings draw a rich and realistic picture of ChHV5 replication in cells derived from its natural host and may be crucial not only to better understand ChHV5 circulation but also to eventually complete Koch's postulates for FP. Moreover, the principles described here may serve as model to culture other viruses that are resistant to replication in conventional cell culture.
Pufferfish mortality associated with novel polar marine toxins in Hawaii
Fish die-offs are important signals in tropical marine ecosystems. In 2010, a mass mortality of pufferfish in Hawaii (USA) was dominated by Arothron hispidus showing aberrant neurological behaviors. Using pathology, toxinology, and field surveys, we implicated a series of novel, polar, marine toxins as a likely cause of this mass mortality. Our findings are striking in that (1) a marine toxin was associated with a kill of a fish species that is itself toxic; (2) we provide a plausible mechanism to explain clinical signs of affected fish; and (3) this epizootic likely depleted puffer populations. Whilst our data are compelling, we did not synthesize the toxin de novo, and we were unable to categorically prove that the polar toxins caused mortality or that they were metabolites of an undefined parent compound. However, our approach does provide a template for marine fish kill investigations associated with marine toxins and inherent limitations of existing methods. Our study also highlights the need for more rapid and cost-effective tools to identify new marine toxins, particularly small, highly polar molecules.
Identification of Chelonid herpesvirus 5 (ChHV5) in endangered green turtles (Chelonia mydas) with fibropapillomatosis in Asia
Fibropapillomatosis (FP), a debilitating tumor disease of sea turtles, was first identified in green turtles [ Chelonia mydas (Linnaeus, 1758)] in Florida in 1938. In recent decades, FP has been observed globally and is an emerging panzootic disease in sea turtles. However, few reports of FP in Asia exist. Here, we provide the first evidence of Chelonid herpesvirus 5 (ChHV5) DNA associated with FP in endangered green turtles from Taiwan, through molecular characterization, phylogenetic analysis, and histopathological examination. In our study, ChHV5 was successfully detected by PCR in the FP tumor lesions of green turtles. The sequences were found to be consistent with those of tumor-inducing viruses shown to affect sea turtles in the other parts of the world. ChHV5 RNA from the FP tissues was further detected by RT-PCR, indicating active replication of the viruses inside FP tumors. In addition to the molecular evidence of ChHV5 in FP, epidermal intranuclear inclusions were identified in tumor lesions upon histopathological examination. This further suggests that ChHV5 should be in a transcriptionally active (i.e., non-latent) state in FP tumors of affected green turtles. The phylogenetic tree revealed that ChHV5 from the green turtles in Taiwan were closest to the ChHV5 from Hawaii, Puerto Rico, and Sao Tome. For conservation of endangered sea turtles, ChHV5 should be considered an emerging virus, which threatens sea turtles in marine waters in Asia.
Long-distance translocations to create a second millerbird population and reduce extinction risk
Translocation is a conservation tool used with increasing frequency to create additional populations of threatened species. In addition to following established general guidelines for translocations, detailed planning to account for unique circumstances and intensive post-release monitoring to document outcomes and guide management are essential components of these projects. Recent translocation of the critically endangered Nihoa millerbird ( Acrocephalus familiaris kingi ) provides an example of this planning and monitoring. The Nihoa millerbird is a passerine bird endemic to Nihoa Island in the remote Northwestern Hawaiian Islands. The closely related, ecologically similar Laysan millerbird ( Acrocephalus familiaris familiaris ) went extinct on Laysan Island in the early 20th century when the island was denuded by introduced rabbits. To reduce extinction risk, we translocated 50 adult Nihoa millerbirds more than 1000 km by sea to Laysan, which has recovered substantially in the past century and has ample habitat and a rich prey-base for millerbirds. Following five years of intensive background research and planning, including development of husbandry techniques, fundraising, and regulatory compliance, translocations occurred in 2011 and 2012. Of 11 females in each cohort, 8 (2011 cohort) and 11 (2012 cohort) produced at least one brood of fledglings during their first year on Laysan. At the conclusion of monitoring in September 2014, 37 of the translocated birds were known to survive, and the population was estimated at 164 birds. The reintroduction of millerbirds to Laysan represents a milestone in the island's ongoing restoration.
Wound repair in Pocillopora
Corals routinely lose tissue due to causes ranging from predation to disease. Tissue healing and regeneration are fundamental to the normal functioning of corals, yet we know little about this process. We described the microscopic morphology of wound repair in Pocillopora damicornis . Tissue was removed by airbrushing fragments from three healthy colonies, and these were monitored daily at the gross and microscopic level for 40 days. Grossly, corals healed by Day 30, but repigmentation was not evident at the end of the study (40 d). On histology, from Day 8 onwards, tissues at the lesion site were microscopically indistinguishable from adjacent normal tissues with evidence of zooxanthellae in gastrodermis. Inflammation was not evident. P . damicornis manifested a unique mode of regeneration involving projections of cell-covered mesoglea from the surface body wall that anastomosed to form gastrovascular canals.
Validation of ultrasound as a noninvasive tool to measure subcutaneous fat depth in leatherback sea turtles ( Dermochelys coriacea )
Leatherback turtles ( Dermochelys coriacea ) undergo substantial cyclical changes in body condition between foraging and nesting. Ultrasonography has been used to measure subcutaneous fat as an indicator of body condition in many species but has not been applied in sea turtles. To validate this technique in leatherback turtles, ultrasound images were obtained from 36 live-captured and dead-stranded immature and adult turtles from foraging and nesting areas in the Pacific and Atlantic oceans. Ultrasound measurements were compared with direct measurements from surgical biopsy or necropsy. Tissue architecture was confirmed histologically in a subset of turtles. The dorsal shoulder region provided the best site for differentiation of tissues. Maximum fat depth values with the front flipper in a neutral (45–90°) position demonstrated good correlation with direct measurements. Ultrasound-derived fat measurements may be used in the future for quantitative assessment of body condition as an index of health in this critically endangered species.
Effects of Coralliophila violacea on tissue loss in the scleractinian corals Porites spp. depend on host response
We investigated interactions between the corallivorous gastropod Coralliophila violacea and its preferred hosts Porites spp. Our objectives were to experimentally determine whether tissue loss could progress in Porites during or after Coralliophila predation on corals with and without tissue loss and to histologically document snail predation. In 64% of feeding scars, tissue regenerated within 3 wk, leaving no trace of predation. However, in roughly 28% of scars, lesions progressed to subacute tissue loss resembling white syndrome. In feeding experiments, scars from snails previously fed diseased tissue developed progressive tissue loss twice as frequently as scars from snails previously fed healthy tissue. Scars from previously healthy-fed snails were 3 times as likely to heal as those from previously diseased-fed snails. Histology revealed marked differences in host responses to snails; P. cylindrica manifested a robust inflammatory response with fewer secondary colonizing organisms such as algae, sponges, and helminths, whereas P. rus showed no evident inflammation and more secondary colonization. We conclude that lesion progression associated with Coralliophila may be associated with secondary colonization of coral tissues damaged by predator-induced trauma and necrosis. Importantly, variation at the cellular level should be considered when explaining interspecific differences in host responses in corals impacted by phenomena such as predation.