Electron microscopy reveals viral-like particles and mitochondrial degradation in scombrid puffy snout syndrome.

Aquaculture is an increasingly important food resource, but its sustainability is often limited by disease. In Scombridae fishes, puffy snout syndrome (PSS) is a debilitating condition where tumor-like collagenous growths form around the eyes, nares, and mandibles which impair vision and feeding and frequently lead to mortality. While PSS is considered an infectious or metabolic disease, no disease agents or promoters have been identified. Here, we used electron microscopy (EM) to describe the cellular pathology and search for etiological agents of PSS in Pacific mackerel Scomber japonicus, the first use of this approach for PSS. We examined aquaculture specimens across a range of apparent PSS severity, comparing the results to both wild and aquaculture asymptomatic mackerel. EM imagery consistently revealed viral-like particles in PSS samples, as well as the uniform absence of bacteria, protists, fungi, and other multicellular parasites. In addition to viral-like particles, symptomatic fish had a higher mean percentage of swollen and disintegrating mitochondria than both asymptomatic aquaculture and wild mackerel. This suggests that degraded mitochondria may be related to PSS and could be important to further understanding the origin, promoters, and prevention of PSS. This study serves as a first step in identifying the etiological agents of PSS.

Herbaria macroalgae as a proxy for historical upwelling trends in Central California.

Planning for future ocean conditions requires historical data to establish more informed ecological baselines. To date, this process has been largely limited to instrument records and observations that begin around 1950. Here, we show how marine macroalgae specimens from herbaria repositories may document long-term ecosystem processes and extend historical information records into the nineteenth century. We tested the effect of drying and pressing six macroalgae species on amino acid, heavy metal and bulk stable isotope values over 1 year using modern and archived paper. We found historical paper composition did not consistently affect values. Certain species, however, had higher variability in particular metrics while others were more consistent. Multiple herbaria provided Gelidium (Rhodophyta) samples collected in southern Monterey Bay from 1878 to 2018. We examined environmental relationships and found δ15N correlated with the Bakun upwelling index, the productivity regime of this ecosystem, from 1946 to 2018. Then, we hindcasted the Bakun index using its derived relationship with Gelidium δ15N from 1878 to 1945. This hindcast provided new information, observing an upwelling decrease mid-century leading up to the well-known sardine fishery crash. Our case study suggests marine macroalgae from herbaria are an underused resource of the marine environment that precedes modern scientific data streams.

Coastal sharks supply the global shark fin trade.

Progress in global shark conservation has been limited by constraints to understanding the species composition and geographic origins of the shark fin trade. Previous assessments that relied on earlier genetic techniques and official trade records focused on abundant pelagic species traded between Europe and Asia. Here, we combine recent advances in DNA barcoding and species distribution modelling to identify the species and source the geographic origin of fins sold at market. Derived models of species environmental niches indicated that shark fishing effort is concentrated within Exclusive Economic Zones, mostly in coastal Australia, Indonesia, the United States, Brazil, Mexico and Japan. By coupling two distinct tools, barcoding and niche modelling, our results provide new insights for monitoring and enforcement. They suggest stronger local controls of coastal fishing may help regulate the unsustainable global trade in shark fins.

US protected lands mismatch biodiversity priorities.

Because habitat loss is the main cause of extinction, where and how much society chooses to protect is vital for saving species. The United States is well positioned economically and politically to pursue habitat conservation should it be a societal goal. We assessed the US protected area portfolio with respect to biodiversity in the country. New synthesis maps for terrestrial vertebrates, freshwater fish, and trees permit comparison with protected areas to identify priorities for future conservation investment. Although the total area protected is substantial, its geographic configuration is nearly the opposite of patterns of endemism within the country. Most protected lands are in the West, whereas the vulnerable species are largely in the Southeast. Private land protections are significant, but they are not concentrated where the priorities are. To adequately protect the nation's unique biodiversity, we recommend specific areas deserving additional protection, some of them including public lands, but many others requiring private investment.

Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes.

Some of the most basic questions of sea turtle life history are also the most elusive. Many uncertainties surround lifespan, growth rates, maturity and spatial structure, yet these are critical factors in assessing population status. Here we examine the keratinized hard tissues of the hawksbill (Eretmochelys imbricata) carapace and use bomb radiocarbon dating to estimate growth and maturity. Scutes have an established dietary record, yet the large keratin deposits of hawksbills evoke a reliable chronology. We sectioned, polished and imaged posterior marginal scutes from 36 individual hawksbills representing all life stages, several Pacific populations and spanning eight decades. We counted the apparent growth lines, microsampled along growth contours and calibrated Δ(14)C values to reference coral series. We fit von Bertalanffy growth function (VBGF) models to the results, producing a range of age estimates for each turtle. We find Hawaii hawksbills deposit eight growth lines annually (range 5-14), with model ensembles producing a somatic growth parameter (k) of 0.13 (range 0.1-0.2) and first breeding at 29 years (range 23-36). Recent bomb radiocarbon values also suggest declining trophic status. Together, our results may reflect long-term changes in the benthic community structure of Hawaii reefs, and possibly shed light on the critical population status for Hawaii hawksbills.

Juvenile recruitment in loggerhead sea turtles linked to decadal changes in ocean circulation.

Given the threats of climate change, understanding the relationship of climate with long-term population dynamics is critical for wildlife conservation. Previous studies have linked decadal climate oscillations to indices of juvenile recruitment in loggerhead sea turtles (Caretta caretta), but without a clear understanding of mechanisms. Here, we explore the underlying processes that may explain these relationships. Using the eddy-resolving Ocean General Circulation Model for the Earth Simulator, we generate hatch-year trajectories for loggerhead turtles emanating from Japan over six decades (1950-2010). We find that the proximity of the high-velocity Kuroshio Current to the primary nesting areas in southern Japan is remarkably stable and that hatchling dispersal to oceanic habitats itself does not vary on decadal timescales. However, we observe a shift in latitudes of trajectories, consistent with the Pacific Decadal Oscillation (PDO). In a negative PDO phase, the Kuroshio Extension Current (KEC) is strong and acts as a physical barrier to the northward transport of neonates. As a result, hatch-year trajectories remain mostly below 35°N in the warm, unproductive region south of the Transition Zone Chlorophyll Front (TZCF). During a positive PDO phase, however, the KEC weakens facilitating the neonates to swim north of the TZCF into cooler and more productive waters. As a result, annual cohorts from negative PDO years may face a lack of resources, whereas cohorts from positive PDO years may find sufficient resources during their pivotal first year. These model outputs indicate that the ocean circulation dynamics, combined with navigational swimming behavior, may be a key factor in the observed decadal variability of sea turtle populations.

Terrestrial basking sea turtles are responding to spatio-temporal sea surface temperature patterns.

Naturalists as early as Darwin observed terrestrial basking in green turtles (Chelonia mydas), but the distribution and environmental influences of this behaviour are poorly understood. Here, we examined 6 years of daily basking surveys in Hawaii and compared them with the phenology of local sea surface temperatures (SST). Data and models indicated basking peaks when SST is coolest, and we found this timeline consistent with bone stress markings. Next, we assessed the decadal SST profiles for the 11 global green turtle populations. Basking generally occurs when winter SST falls below 23°C. From 1990 to 2014, the SST for these populations warmed an average 0.04°C yr(-1) (range 0.01-0.09°C yr(-1)); roughly three times the observed global average over this period. Owing to projected future warming at basking sites, we estimated terrestrial basking in green turtles may cease globally by 2100. To predict and manage for future climate change, we encourage a more detailed understanding for how climate influences organismal biology.

A Raman spectral reference library of potential anthropogenic and biological ocean polymers.

Microplastics have been extensively documented in marine ecosystems and food webs with devastating impacts. To solve this global crisis, identifying the polymer composition is key for resolving the material origin, geographic source, and ecosystem life cycle of ocean plastics. Visually based techniques, importantly, are not diagnostic. Raman spectroscopy is an increasingly preferred identification method for its accuracy and reduced likelihood of misinterpretation, though it can be inaccessible due to cost of paywalled spectral libraries and availability of relevant polymer spectra for comparison. Here, we provide an open-access reference library of high-quality, broad-spectrum Raman spectra of major polymer categories germane to marine environments. The library includes high-quality spectra from: (a) pristine anthropogenic polymers newly sourced from manufacturers (n = 40), (b) weathered anthropogenic polymers collected from used consumer, beachcast, agricultural, and fishery sources (n = 22), and (c) biological polymers representing diverse marine taxa, trophic levels, and tissues (n = 17). We hope this reference library can help this rapidly expanding scientific community and facilitate progress in the global plastic pollution crisis.

A biologging database of juvenile white sharks from the northeast Pacific.

Species occurrence records are vital data streams in marine conservation with a wide range of important applications. From 2001-2020, the Monterey Bay Aquarium led an international research collaboration to understand the life cycle, ecology, and behavior of white sharks (Carcharodon carcharias) in the southern California Current. The collaboration was devoted to tagging juveniles with animal-borne sensors, also known as biologging. Here we report the full data records from 59 pop-up archival (PAT) and 20 smart position and temperature transmitting (SPOT) tags that variously recorded pressure, temperature, and light-level data, and computed depth and geolocations for 63 individuals. Whether transmitted or from recovered devices, raw data files from successful deployments (n = 70) were auto-ingested from the manufacturer into the United States (US) Animal Telemetry Network's (ATN) Data Assembly Center (DAC). There they have attributed a full suite of metadata, visualized within their public-facing data portal, compiled for permanent archive under the DataONE Research Workspace member node, and are accessible for download from the ATN data portal.

The geographic disparity of historical greenhouse emissions and projected climate change.

One challenge in climate change communication is that the causes and impacts of global warming are unrelated at local spatial scales. Using high-resolution datasets of historical anthropogenic greenhouse emissions and an ensemble of 21st century surface temperature projections, we developed a spatially explicit index of local climate disparity. This index identifies positive (low emissions, large temperature shifts) and negative disparity regions (high emissions, small temperature shifts), with global coverage. Across all climate change projections we analyzed, 99% of the earth's surface area has a positive index value. This result underscores that while emissions are geographically concentrated, warming is globally widespread. From our index, the regions of the greatest positive disparity appear concentrated in the polar arctic, Central Asia, and Africa with negative disparity regions in western Europe, Southeast Asia, and eastern North America. Straightforward illustrations of this complex relationship may inform on equity, enhance public understanding, and increase collective global action.

North Pacific warming shifts the juvenile range of a marine apex predator.

During the 2014-2016 North Pacific marine heatwave, unprecedented sightings of juvenile white sharks (Carcharodon carcharias) emerged in central California. These records contradicted the species established life history, where juveniles remain in warmer waters in the southern California Current. This spatial shift is significant as it creates potential conflicts with commercial fisheries, protected species conservation, and public safety concerns. Here, we integrate community science, photogrammetry, biologging, and mesoscale climate data to describe and explain this phenomenon. We find a dramatic increase in white sharks from 2014 to 2019 in Monterey Bay that was overwhelmingly comprised of juvenile sharks < 2.5 m in total body length. Next, we derived thermal preferences from 22 million tag measurements of 14 juvenile sharks and use this to map the cold limit of their range. Consistent with historical records, the position of this cold edge averaged 34° N from 1982 to 2013 but jumped to 38.5° during the 2014-2016 marine heat wave. In addition to a poleward shift, thermally suitable habitat for juvenile sharks declined 223.2 km2 year-1 from 1982 to 2019 and was lowest in 2015 at the peak of the heatwave. In addition to advancing the adaptive management of this apex marine predator, we discuss this opportunity to engage public on climate change through marine megafauna.

Stormy oceans are associated with declines in sea turtle hatching.

Many sea turtle populations are below 10% of their pre-Columbian numbers [1-4]. Though historic and systematic over-exploitation is the principal cause of these declines, sea turtles face similar threats today. Adults and juveniles are actively hunted and commercial fisheries catch them incidentally. Nesting suffers from beach development, egg poaching and the poaching of nesting females. Accompanying these familiar hazards is the largely unknown consequences of recent climate change. Here we report monitoring surveys from the Dry Tortugas National Park (DTNP, 24.64N 82.86W), Florida, and show that hurricanes and other storm events are an additional and increasing threat to loggerhead turtle (Caretta caretta) and green sea turtle (Chelonia mydas) nesting. Both species are listed by the US Endangered Species Act and the IUCN considers them 'endangered'.

Sentiment Analysis of Conservation Studies Captures Successes of Species Reintroductions.

Learning from the rapidly growing body of scientific articles is constrained by human bandwidth. Existing methods in machine learning have been developed to extract knowledge from human language and may automate this process. Here, we apply sentiment analysis, a type of natural language processing, to facilitate a literature review in reintroduction biology. We analyzed 1,030,558 words from 4,313 scientific abstracts published over four decades using four previously trained lexicon-based models and one recursive neural tensor network model. We find frequently used terms share both a general and a domain-specific value, with either positive (success, protect, growth) or negative (threaten, loss, risk) sentiment. Sentiment trends suggest that reintroduction studies have become less variable and increasingly successful over time and seem to capture known successes and challenges for conservation biology. This approach offers promise for rapidly extracting explicit and latent information from a large corpus of scientific texts.

Towards a global understanding of the drivers of marine and terrestrial biodiversity.

Understanding the distribution of life's variety has driven naturalists and scientists for centuries, yet this has been constrained both by the available data and the models needed for their analysis. Here we compiled data for over 67,000 marine and terrestrial species and used artificial neural networks to model species richness with the state and variability of climate, productivity, and multiple other environmental variables. We find terrestrial diversity is better predicted by the available environmental drivers than is marine diversity, and that marine diversity can be predicted with a smaller set of variables. Ecological mechanisms such as geographic isolation and structural complexity appear to explain model residuals and also identify regions and processes that deserve further attention at the global scale. Improving estimates of the relationships between the patterns of global biodiversity, and the environmental mechanisms that support them, should help in efforts to mitigate the impacts of climate change and provide guidance for adapting to life in the Anthropocene.

Robust age estimation of southern sea otters from multiple morphometrics.

Reliable age estimation is an essential tool to assess the status of wildlife populations and inform successful management. Aging methods, however, are often limited by too few data, skewed demographic representation, and by single or uncertain morphometric relationships. In this study, we synthesize age estimates in southern sea otters Enhydra lutris nereis from 761 individuals across 34 years of study, using multiple noninvasive techniques and capturing all life stages from 0 to 17 years of age. From wild, stranded, and captive individuals, we describe tooth eruptions, tooth wear, body length, nose scarring, and pelage coloration across ontogeny and fit sex-based growth functions to the data. Dental eruption schedules provided reliable and identifiable metrics spanning 0.3-9 months. Tooth wear was the most reliable predictor of age of individuals aged 1-15 years, which when combined with total length, explained >93% of observed age. Beyond age estimation, dental attrition also indicated the maximum lifespan of adult teeth is 13‒17 years, corresponding with previous estimates of life expectancy. Von Bertalanffy growth function model simulations of length at age gave consistent estimates of asymptotic lengths (male Loo  = 126.0‒126.8 cm, female Loo  = 115.3‒115.7 cm), biologically realistic gestation periods (t 0 = 115 days, SD = 10.2), and somatic growth (male k = 1.8, SD = 0.1; female k = 2.1, SD = 0.1). Though exploratory, we describe how field radiographic imaging of epiphyseal plate development or fusions may improve aging of immature sea otters. Together, our results highlight the value of integrating information from multiple and diverse datasets to help resolve conservation problems.

Author Correction: The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Densities and drivers of sea turtle populations across Pacific coral reef ecosystems.

Sea turtle populations are often assessed at the regional to sub-basin scale from discrete indices of nesting abundance. While this may be practical and sometimes effective, widespread in-water surveys may enhance assessments by including additional demographics, locations, and revealing emerging population trends. Here, we describe sea turtle observations from 13 years of towed-diver surveys across 53 coral islands, atolls, and reefs in the Central, West, and South Pacific. These surveys covered more than 7,300 linear km, and observed more than 3,400 green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) sea turtles. From these data, we estimated sea turtle densities, described trends across space and time, and modelled the influence of environmental and anthropogenic drivers. Both species were patchily distributed across spatial scales, and green turtles were 11 times more abundant than hawksbills. The Pacific Remote Island Areas had the highest densities of greens (3.62 turtles km-1, Jarvis Island), while American Samoa had the most hawksbills (0.12 turtles km-1, Ta'u Island). The Hawaiian Islands had the lowest turtle densities (island ave = 0.07 turtles km-1) yet the highest annual population growth (µ = 0.08, σ = 0.22), suggesting extensive management protections can yield positive conservation results. Densities peaked at 27.5°C SST, in areas of high productivity and low human impact, and were consistent with patterns of historic overexploitation. Though such intensive surveys have great value, they are logistically demanding and therefore have an uncertain budget and programmatic future. We hope the methods we described here may be applied to future comparatively low-cost surveys either with autonomous vehicles or with environmental DNA.

Non-trophic impacts from white sharks complicate population recovery for sea otters.

Complex interactions between protected populations may challenge the recovery of whole ecosystems. In California, white sharks (Carcharodon carcharias) mistargeting southern sea otters (Enhydra lutris nereis) are an emergent impact to sea otter recovery, inhibiting the broader ecosystem restoration sea otters might provide. Here, we integrate and analyze tracking and stranding data to compare the phenology of interactions between white sharks and their targeted prey (elephant seals, Mirounga angustirostris) with those of mistargeted prey (sea otters, humans). Pronounced seasonal peaks in shark bites to otters and humans overlap in the late boreal summer, immediately before the annual adult white shark migration to elephant seal rookeries. From 1997 to 2017, the seasonal period when sharks bite otters expanded from 2 to 8 months of the year and occurred primarily in regions where kelp cover declined. Immature and male otters, demographics most associated with range expansion, were disproportionately impacted. While sea otters are understood to play a keystone role in kelp forests, recent ecosystem shifts are revealing unprecedented bottom-up and top-down interactions. Such shifts challenge ecosystem management programs that rely on static models of species interactions.