Search for: All records

Abstract We present CoralCT, a software application for analysis of annual extension, density, and calcification in coral skeletal cores. CoralCT can be used to analyze computed tomography (CT) scans or X‐ray images of skeletal cores through a process in which observers interact with images of a core to define the locations of annual density bands. The application streamlines this process by organizing the observer‐defined banding patterns and automatically measuring growth parameters. Analyses can be conducted in two or three dimensions, and observers have the option to utilize an automatic band‐detection feature. CoralCT is linked to a server that stores the raw CT and X‐ray image data, as well as output growth rate data for hundreds of cores. Overall, this server‐based system enables broad collaborations on coral core analysis with standardized methods and—crucially—creates a pathway for implementing multiobserver analysis. We assess the method by comparing multiple techniques for measuring annual extension and density, including a corallite‐tracing approach, medical imaging software, two‐dimensional vs. three‐dimensional analyses, and between multiple observers. We recommend that CoralCT be used not only as a measurement tool but also as a platform for data archiving and conducting open, collaborative science. 

Climate change is imposing multiple stressors on marine life, leading to a restructuring of ecological communities as species exhibit differential sensitivities to these stressors. With the ocean warming and wind patterns shifting, processes that drive thermal variations in coastal regions, such as marine heatwaves and upwelling events, can change in frequency, timing, duration, and severity. These changes in environmental parameters can physiologically impact organisms residing in these habitats. Here, we investigate the synchrony of coral and reef fish responses to environmental disturbance in the Red Sea, including an unprecedented combination of heat stress and upwelling that led to mass coral bleaching in 2015. We developed cross-dated growth chronologies from otoliths of 156 individuals of two planktivorous damselfish species,Pomacentrus sulfureusandAmblyglyphidodon flavilatus, and from skeletal cores of 48Poritesspp. coral colonies. During and immediately after the 2015 upwelling and bleaching event, damselfishes exhibited a positive growth anomaly but corals displayed reduced growth. Yet, after 2015–2016, these patterns were reversed with damselfishes showing a decline in growth and corals rebounding to pre-disturbance growth rates. Our results reveal an asynchronous response between corals and reef fish, with corals succumbing to the direct effects of heat stress, and then quickly recovering when the heat stress subsided—at least, for those corals that survived the bleaching event. Conversely, damselfish growth temporarily benefited from the events of 2015, potentially due to the increased metabolic demand from increased temperature and increased food supply from the upwelling event, before declining over four years, possibly related to indirect effects associated with habitat degradation following coral mortality. Overall, our study highlights the increasingly complex, often asynchronous, ecological ramifications of climate extremes on the diverse species assemblages of coral reefs. 

Subterranean estuaries are coastal ecosystems characterized by vertically stratified groundwater. The biota within these ecosystems is relatively understudied due to the inherent difficulty of accessing such extreme environments. The fauna inhabiting these ecosystems is considered vulnerable to extinction, and the presence of cryptic species has major implications for research and conservation efforts. Most species lack molecular data; however, the evaluation of genetic data for some taxa has revealed that undocumented species are common. This study employs molecular species delimitation methods and DNA barcoding through the analysis of publicly and newly generated sequences, including individuals from type localities and non-crustacean phyla; the latter are typically overlooked in biodiversity assessments of subterranean estuaries. We analysed 376 cytochrome c oxidase subunit I (COI) gene sequences and 154 16S rRNA gene sequences. The COI sequences represented 32% of previously described species and 50% of stygobiont species from the Yucatan Peninsula and Cozumel Island, while sequences of the 16S rRNA represented 14% of described species and 22% of stygobionts. Our results revealed cryptic genetic lineages and taxonomic misidentification of species. As several species from these ecosystems are recognized as endangered, the use of molecular approaches will improve biodiversity estimates and highlight overlooked cryptic lineages in need of evaluation of conservation status. 

Abstract 1D multiferroic fibers are known to exhibit attractive characteristics, including enhanced magnetoelectric (ME) coupling compared to thin film and bulk architectures. A comprehensive understanding of composite fibers, however, has been hindered by the complexity of their structure, leading to limited reports. Here, clear and strong ME coupling is experimentally detected in a composite Janus nanofiber aggregate using second harmonic generation (SHG) polarimetry under different magnetic field orientations. The observation of such a pronounced effect using an all‐optical method has not been previously reported in multiferroic fibers. A series of global fits is performed to the SHG polarimetry results to investigate the behavior of nanofibers within an aggregate. We find the magnetically assembled fibers exhibit semi‐cylindrical alignment as well as the expected lengthwise alignment despite variations in size and composition from fiber to fiber. The ME coupling and the semi‐cylindrical alignment seen in SHG are further corroborated via X‐ray diffraction under similar magnetic field conditions. These findings contribute to the development of complex composite and multifunctional devices using multiferroic nanostructures as building blocks, even those with inhomogeneous shapes and geometries. 

Abstract Echinoderms produce functional gametes throughout their lifespan, in some cases exceeding 200 years. The histology and ultrastructure of echinoderm ovaries has been described but how these ovaries function and maintain the production of high‐quality gametes remains a mystery. Here, we present the first single cell RNA sequencing data sets of mature ovaries from two sea urchin species (Strongylocentrotus purpuratus [Sp]andLytechinus variegatus [Lv]), and one sea star species (Patiria miniata [Pm]). We find 14 cell states in the Sp ovary, 16 cell states in the Lv ovary and 13 cell states in the ovary of the sea star. This resource is essential to understand the structure and functional biology of the ovary in echinoderms, and better informs decisions in the utilization of in situ RNA hybridization probes selective for various cell types. We link key genes with cell clusters in validation of this approach. This resource also aids in the identification of the stem cells for prolonged and continuous gamete production, is a foundation for testing changes in the annual reproductive cycle, and is essential for understanding the evolution of reproduction of this important phylum. 

A series of archaeal bipolar glycerol dialkyl glycerol tetraether (GDGT) lipids were synthesized. Structural properties of self-assembled structures of GDGTs were studied and related to functional behavior such as membrane fusion. 

Abstract This work evaluates glacial dust as a source of sediment, and associated iron (Fe), to the Fe‐limited Gulf of Alaska (GoA). A reanalysis of GoA sediment data, using rare earth elements and thorium as provenance tracers, suggests a flux to the ocean surface of Copper River (AK) glacial dust, and associated Fe, that is comparable to the flux of dust from Asia, at least 1,000 km from the narrow mountain valley glacial dust source area. This work suggests dust from Asia may not be the largest source of Fe to the GoA. Dust models fail to accurately simulate this glacial dust transport because their coarse resolution underestimates wind speeds, and the dust flux. This work suggests that glacial dust fluxes may have been important in the geologic past (e.g., the last glacial maximum) from locations where there was more extensive coverage by glaciers than at present.