Stable isotopes used to infer trophic position of green turtles (Chelonia mydas) from Dry Tortugas National Park, Gulf of Mexico, United States

Evaluating resource use patterns for imperiled species is critical for understanding what supports their populations. Here we established stable isotope (δ13C, δ15N) values for the endangered green sea turtle (Chelonia mydas) population found within the boundaries of Dry Tortugas National Park (DRTO), south Florida, USA. There is little gene flow between turtles sampled at DRTO and in other rookeries in Florida, underscoring the need to study this distinct population. Between 2008 and 2015 we collected multiple sample types (skin [homogenized epidermis/dermis], whole blood, red blood cells, plasma, carapace) from 151 unique green turtles, including 43 nesting females and 108 in-water captures; some individuals were resampled multiple times across years to evaluate consistency of isotope signatures. Isotopic ratios ranged from -27.3 to -5.4 for δ13C and 3.7 to 10.6 for δ15N. Using linear mixed models, we evaluated covariates (sample type, turtle size and year) that best explained the isotope patterns observed in turtle tissues. Predictions from the top model for δ13C indicated a slight decrease over time and for δ15N a slight increase in the middle sampling years (2010–2012); results indicated that turtle size appeared to be the driver behind the range in δ13C and δ15N observed in turtle skin. We found a pattern in stable carbon isotope values that are indicative of an ontogenetic change from an omnivorous diet in smaller turtles to a seagrass-based diet in larger turtles. When we compared the stable carbon and nitrogen isotope values of the samples collected from turtles with that of seagrasses found in DRTO, we found that turtles \u3e 65 cm SCL had similar stable carbon isotope values to the seagrass species present. Results of this study suggest stable isotope analysis coupled with data for available resources can be useful for tracking and detecting future changes in green turtle resource shifts in DRTO

Too Hot to Handle: Unprecedented Seagrass Death Driven by Marine Heatwave in a World Heritage Area

The increased occurrence of extreme climate events, such as marine heatwaves (MHWs), has resulted in substantial ecological impacts worldwide. To date metrics of thermal stress within marine systems have focussed on coral communities, and less is known about measuring stress relevant to other primary producers, such as seagrasses. An extreme MHW occurred across the Western Australian coastline in the austral summer of 2010/2011, exposing marine communities to summer seawater temperatures 2‐5 °C warmer than average. Using a combination of satellite imagery and in situ assessments, we provide detailed maps of seagrass coverage across the entire Shark Bay World Heritage Area (ca. 13,000 km2) before (2002, 2010) and after the MHW (2014, 2016). Our temporal analysis of these maps documents the single largest loss in dense seagrass extent globally (1,310 km2) following an acute disturbance. Total change in seagrass extent was spatially heterogenous, with the most extensive declines occurring in the Western Gulf, Wooramel Bank and Faure Sill. Spatial variation in seagrass loss was best explained by a model that included an interaction between two heat stress metrics, the most substantial loss occurring when degree heat weeks (DHWm) was ≥ 10 and the number of days exposed to extreme sea surface temperature during the MHW (DaysOver) was ≥ 94. Ground‐truthing at 622 points indicated that change in seagrass cover was predominantly due to loss of Amphibolis antarctica rather than Posidonia australis, the other prominent seagrass at Shark Bay. As seawater temperatures continue to rise and the incidence of MHWs increase globally, this work will provide a basis for identifying areas of meadow degradation, or stability and recovery; and potential areas of resilience

Seagrasses in the Age of Sea Turtle Conservation and Shark Overfishing

Efforts to conserve globally declining herbivorous green sea turtles have resulted in promising growth of some populations. These trends could significantly impact critical ecosystem services provided by seagrass meadows on which turtles feed. Expanding turtle populations could improve seagrass ecosystem health by removing seagrass biomass and preventing of the formation of sediment anoxia. However, overfishing of large sharks, the primary green turtle predators, could facilitate turtle populations growing beyond historical sizes and trigger detrimental ecosystem impacts mirroring those on land when top predators were extirpated. Experimental data from multiple ocean basins suggest that increasing turtle populations can negatively impact seagrasses, including triggering virtual ecosystem collapse. Impacts of large turtle populations on seagrasses are reduced in the presence of intact shark populations. Healthy populations of sharks and turtles, therefore, are likely vital to restoring or maintaining seagrass ecosystem structure, function, and their value in supporting fisheries and as a carbon sink

A Systematic Review of How Multiple Stressors from an Extreme Event Drove Ecosystem-Wide Loss of Resilience in an Iconic Seagrass Community

A central question in contemporary ecology is how climate change will alter ecosystem structure and function across scales of space and time. Climate change has been shown to alter ecological patterns from individuals to ecosystems, often with negative implications for ecosystem functions and services. Furthermore, as climate change fuels more frequent and severe extreme climate events (ECEs) like marine heatwaves (MHWs), such acute events become increasingly important drivers of rapid ecosystem change. However, our understanding of ECE impacts is hampered by limited collection of broad scale in situ data where such events occur. In 2011, a MHW known as the Ningaloo Niño bathed the west coast of Australia in waters up to 4°C warmer than normal summer temperatures for almost 2 months over 1000s of kilometres of coastline. We revisit published and unpublished data on the effects of the Ningaloo Niño in the seagrass ecosystem of Shark Bay, Western Australia (24.6 – 26.6o S), at the transition zone between temperate and tropical seagrasses. Therein we focus on resilience, including resistance to and recovery from disturbance across local, regional and ecosystem-wide spatial scales and over the past 8 yearsThermal effects on temperate seagrass health were severe and exacerbated by simultaneous reduced light conditions associated with sediment inputs from record floods in the south-eastern embayment and from increased detrital loads and sediment destabilisation. Initial extensive defoliation of Amphibolis antarctica, the dominant seagrass, was followed by rhizome death that occurred in 60-80% of the bay’s meadows, equating to decline of over 1000 km2 of meadows. This loss, driven by direct abiotic forcing, has persisted, while indirect biotic effects (e.g. dominant seagrass loss) have allowed colonisation of some areas by small fast-growing tropical species (e.g. Halodule uninervis). Those biotic effects also impacted multiple consumer populations including turtles and dugongs, with implications for species dynamics, food web structure, and ecosystem recovery. We show multiple stressors can combine to evoke extreme ecological responses by pushing ecosystems beyond their tolerance. Finally, both direct abiotic and indirect biotic effects need to be explicitly considered when attempting to understand and predict how ECEs will alter marine ecosystem dynamics

De schadelijke werking van het zaad van de Ricinus communis op de gezondheid : een bedrijfsgeneeskundig onderzoek bij havenwerkers te Rotterdam

Large predators often play important roles in structuring marine communities. To understand the role that these predators play in ecosystems, it is crucial to have knowledge of their interactions and the degree to which their trophic roles are complementary or redundant among species. We used stable isotope analysis to examine the isotopic niche overlap of dolphins Tursiops cf. aduncus, large sharks (\u3e1.5 m total length), and smaller elasmobranchs (sharks and batoids) in the relatively pristine seagrass community of Shark Bay, Australia. Dolphins and large sharks differed in their mean isotopic values for δ13C and δ15N, and each group occupied a relatively unique area in isotopic niche space. The standard ellipse areas (SEAc; based on bivariate standard deviations) of dolphins, large sharks, small sharks, and rays did not overlap. Tiger sharks Galeocerdo cuvier had the highest δ15N values, although the mean δ13C and δ15N values of pigeye sharks Carcharhinus amboinensis were similar. Other large sharks (e.g. sicklefin lemon sharksNegaprion acutidens and sandbar sharks Carcharhinus plumbeus) and dolphins appeared to feed at slightly lower trophic levels than tiger sharks. In this seagrass-dominated ecosystem, seagrass-derived carbon appears to be more important for elasmobranchs than it is for dolphins. Habitat use patterns did not correlate well with the sources of productivity supporting diets, suggesting that habitat use patterns may not necessarily be reflective of the resource pools supporting a population and highlights the importance of detailed datasets on trophic interactions for elucidating the ecological roles of predators

SPARC REport No. 7

peer reviewedThe Montreal Protocol (MP) controls the production and consumption of carbon tetrachloride (CCl4 or CTC) and other ozone-depleting substances (ODSs) for emissive uses. CCl4 is a major ODS, accounting for about 12% of the globally averaged inorganic chlorine and bromine in the stratosphere, compared to 14% for CFC-12 in 2012. In spite of the MP controls, there are large ongoing emissions of CCl4 into the atmosphere. Estimates of emissions from various techniques ought to yield similar numbers. However, the recent WMO/UNEP Scientific Assessment of Ozone Depletion [WMO, 2014] estimated a 2007-2012 CCl4 bottom-up emission of 1-4 Gg/year (1-4 kilotonnes/year), based on country-by-country reports to UNEP, and a global top-down emissions estimate of 57 Gg/ year, based on atmospheric measurements. This 54 Gg/year difference has not been explained. In order to assess the current knowledge on global CCl4 sources and sinks, stakeholders from industrial, governmental, and the scientific communities came together at the “Solving the Mystery of Carbon Tetrachloride” workshop, which was held from 4-6 October 2015 at Empa in Dübendorf, Switzerland. During this workshop, several new findings were brought forward by the participants on CCl4 emissions and related science. • Anthropogenic production and consumption for feedstock and process agent uses (e.g., as approved solvents) are reported to UNEP under the MP. Based on these numbers, global bottom-up emissions of 3 (0-8) Gg/year are estimated for 2007-2013 in this report. This number is also reasonably consistent with this report’s new industry-based bottom-up estimate for fugitive emissions of 2 Gg/year. • By-product emissions from chloromethanes and perchloroethylene plants are newly proposed in this report as significant CCl4 sources, with global emissions estimated from these plants to be 13 Gg/year in 2014. • This report updates the anthropogenic CCl4 emissions estimation as a maximum of ~25 Gg/year. This number is derived by combining the above fugitive and by-product emissions (2 Gg/year and 13 Gg/year, respectively) with 10 Gg/year from legacy emissions plus potential unreported inadvertent emissions from other sources. • Ongoing atmospheric CCl4 measurements within global networks have been exploited for assessing regional emissions. In addition to existing emissions estimates from China and Australia, the workshop prompted research on emissions in the U.S. and Europe. The sum of these four regional emissions is estimated as 21±7.5a Gg/year, but this is not a complete global accounting. These regional top-down emissions estimates also show that most of the CCl4 emissions originate from chemical industrial regions, and are not linked to major population centres. • The total CCl4 lifetime is critical for calculating top-down global emissions. CCl4 is destroyed in the stratosphere, oceans, and soils, complicating the total lifetime estimate. The atmospheric lifetime with respect to stratospheric loss was recently revised to 44 (36-58) years, and remains unchanged in this report. New findings from additional measurement campaigns and reanalysis of physical parameters lead to changes in the ocean lifetime from 94 years to 210 (157-313) years, and in the soil lifetime from 195 years to 375 (288-536) years. • These revised lifetimes lead to an increase of the total lifetime from 26 years in WMO [2014] to 33 (28-41) years. Consequently, CCl4 is lost at a slower rate from the atmosphere. With this new total lifetime, the global top-down emissions calculation decreases from 57 (40-74) Gg/year in WMO [2014] to 40 (25-55) Gg/year. This estimate is relatively consistent with the independent gradient top-down emissions of 30 (25-35) Gg/year, based upon differences between atmospheric measurements of CCl4 in the Northern and Southern Hemispheres. In addition, this new total lifetime implies an upper limit of 3-4 Gg/year of natural emissions, based upon newly reported observations of old air in firn snow. These new CCl4 emissions estimates from the workshop make considerable progress toward closing the emissions discrepancy. The new industrial bottom-up emissions estimate (15 Gg/year total) includes emissions from chloromethanes plants (13 Gg/year) and feedstock fugitive emissions (2 Gg/year). When combined with legacy emissions and unreported inadvertent emissions, this could be up to 25 Gg/year. Top-down emissions estimates are: global 40 (25-55) Gg/year, gradient 30 (25-35) Gg/year, and regional 21 (14-28) Gg/year. While the new bottom-up value is still less than the aggregated top-down values, these estimates reconcile the CCl4 budget discrepancy when considered at the edges of their uncertainties

Contribution of alcohol use in HIV/hepatitis C virus co-infection to all-cause and cause-specific mortality: A collaboration of cohort studies

Among persons with HIV (PWH), higher alcohol use and having hepatitis C virus (HCV) are separately associated with increased morbidity and mortality. We investigated whether the association between alcohol use and mortality among PWH is modified by HCV. Data were combined from European and North American cohorts of adult PWH who started antiretroviral therapy (ART). Self-reported alcohol use data, collected in diverse ways between cohorts, were converted to grams/day. Eligible PWH started ART during 2001-2017 and were followed from ART initiation for mortality. Interactions between the associations of baseline alcohol use (0, 0.1-20.0, >20.0 g/day) and HCV status were assessed using multivariable Cox models. Of 58,769 PWH, 29,711 (51%), 23,974 (41%) and 5084 (9%) self-reported alcohol use of 0 g/day, 0.1-20.0 g/day, and > 20.0 g/day, respectively, and 4799 (8%) had HCV at baseline. There were 844 deaths in 37,729 person-years and 2755 deaths in 443,121 person-years among those with and without HCV, respectively. Among PWH without HCV, adjusted hazard ratios (aHRs) for mortality were 1.18 (95% CI: 1.08-1.29) for 0.0 g/day and 1.84 (1.62-2.09) for >20.0 g/day compared with 0.1-20.0 g/day. This J-shaped pattern was absent among those with HCV: aHRs were 1.00 (0.86-1.17) for 0.0 g/day and 1.64 (1.33-2.02) for >20.0 g/day compared with 0.1-20.0 g/day (interaction p < .001). Among PWH without HCV, mortality was higher in both non-drinkers and heavy drinkers compared with moderate alcohol drinkers. Among those with HCV, mortality was higher in heavy drinkers but not non-drinkers, potentially due to differing reasons for not drinking (e.g. illness) between those with and without HCV

NSU Marine Turtle Tracking: What we know so far about the post-nesting movements of loggerhead (Caretta caretta) turtles nesting in Broward County, FL

While there are many challenges in managing threatened populations of highly-migratory marine species, a primary issue is understanding their movements and home ranges. Post-nesting movements of marine turtles can be investigated with satellite telemetry. From 2016 to 2021, we deployed satellite transmitters on 26 female loggerhead turtles (Caretta caretta) nesting on Broward County beaches. We used state-space modeling, asymptotic evaluation, and kernel density estimation to characterize their internesting, migratory, and foraging movements. Of the 20 turtles successfully tracked to foraging grounds, only six remained in US waters, while 14 individuals (70%) moved to international waters. Two of the 14 returned to Campeche Bay, Mexico and the other 12 settled in foraging areas throughout the Bahamas. Migratory distances and durations, as well as total area of foraging home ranges, varied between and within foraging regions. This study represents the first in-depth investigation into post-nesting movements of female loggerhead turtles nesting in Southeast Florida. The highly international nature of these movements highlights the need for regional collaboration to appropriately manage this population

Spatial Pattern in Seagrass Stoichiometry Indicates Both N-Limited and P-Limited Regions of an Iconic P-Limited Subtropical Bay

We investigated seagrass species distribution and nutrient content in the iconic phosphorus-limited Shark Bay, Western Australia. We found the slower-growing, temperate species Amphibolis antarctica and Posidonia spp. had lower N and P content compared to the faster-growing tropical species Halodule uninervis, Syringodium isoetifolium,Cymodocea angustata, Halophila ovalis and Halophila spinulosa. Further, by comparing elemental content of different seagrass species at sites where species co-occurred, we were able to standardize seagrass elemental content across sites with different species composition. This standardization allowed us to make ecosystem-scale inferences about resource availability despite taxon-specific distributions and elemental content. We found a marked spatial pattern in N:P of seagrasses across the system, indicating that P limitation occurred, despite calcium carbonate sediments, only in the most isolated portions of the bay. Large areas closer to the mouth of the bay were either N limited or were not limited by N or P availability. Our results suggest that large-scale nutrient budgets may oversimplify our understanding of limiting factors in a system, resulting in management decisions that may have unforeseen effects on different areas within the same ecosystem