ICESat-2 Applications for Investigating Emerging Volcanoes

Submarine volcanism in shallow waters (<100 m), particularly in remote settings, is difficult to monitor quantitatively and, in the rare formation of islands, it is challenging to understand the rapid-paced erosion. However, these newly erupted volcanic islands become observable to airborne and/or satellite remote sensing instruments. NASA’s ICESat-2 satellite laser altimeter, combined with visible imagery (optical and microwave), provide a novel method of evaluating the elevation characteristics of newly emerged volcanoes and their subaerial eruption products. Niijima Fukutoku-Okanoba (NFO) is a submarine volcano 1300 km south of Tokyo (Ogasawara Archipelago of Japan) that periodically breaches the ocean surface to create new islands that are subsequently eroded. The recent eruption in August 2021 is a rare opportunity to investigate this island evolution using high-resolution satellite datasets with geodetic-quality ICESat-2 altimetry. Lansdat-8 and Planet imagery provide a qualitative analysis of the exposed volcanic deposits, while ICESat-2 products provide elevation profiles necessary to quantify the physical surface structures. This investigation determines an innovative application for ICESat-2 data in evaluating newly emerged islands and how the combination of satellite remote sensing (visible and lidar) to investigate these short-lived volcanic features can improve our understanding of the volcanic island system in ways not previously possible.

Grand canonical partition function of a serial metallic island system

We present a calculation of the grand canonical partition function of a serial metallic island system by the imaginary-time path integral formalism. To this purpose, all electronic excitations in the lead and island electrodes are described using Grassmann numbers. The Coulomb charging energy of the system is represented in terms of phase fields conjugate to the island charges. By the large channel approximation, the tunneling action phase dependence can also be determined explicitly. Therefore, we represent the partition function as a path integral over phase fields with a path probability given in an analytically known effective action functional. Using the result, we also propose a calculation of the average electron number of the serial island system in terms of the expectation value of winding numbers. Finally, as an example, we describe the Coulomb blockade effect in the two-island system by the average electron number and propose a method to construct the quantum stability diagram.

Class I DISARM provides anti-phage and anti-conjugation activity by unmethylated DNA recognition

Bacteriophages impose a strong evolutionary pressure on microbes for the development of mechanisms of survival. Multiple new mechanisms of innate defense have been described recently, with the molecular mechanism of most of them remaining uncharacterized. Here, we show that a Class 1 DISARM (defense island system associated with restriction-modification) system from Serratia sp. provides broad protection from double-stranded DNA phages, and drives a population of single-stranded phages to extinction. We identify that protection is not abolished by deletion of individual DISARM genes and that the absence of methylase genes drmMI and drmMII does not result in autoimmunity. In addition to antiphage activity we also observe that DISARM limits conjugation, and this activity is linked to the number of methylase cognate sites in the plasmid. Overall, we show that Class 1 DISARM provides robust anti-phage and anti-plasmid protection mediated primarily by drmA and drmB, which provide resistance to invading nucleic acids using a mechanism enhanced by the recognition of unmethylated cognate sites of the two methylases drmMI and drmMII.

Structural basis for broad anti-phage immunity by DISARM

In the evolutionary arms race against phage, bacteria have assembled a diverse arsenal of antiviral immune strategies. While the recently discovered DISARM (Defense Island System Associated with Restriction-Modification) systems can provide protection against a wide range of phage, the molecular mechanisms that underpin broad antiviral targeting but avoiding autoimmunity remain enigmatic. Here, we report cryo-EM structures of the core DISARM complex, DrmAB, both alone and in complex with an unmethylated phage DNA mimetic. These structures reveal that DrmAB core complex is autoinhibited by a trigger loop (TL) within DrmA and binding to DNA substrates containing a 5' overhang dislodges the TL, initiating a long-range structural rearrangement for DrmAB activation. Together with structure-guided in vivo studies, our work provides insights into the mechanism of phage DNA recognition and specific activation of this widespread antiviral defense system.

Climate Adaptation for Tropical Island Land Stewardship: Adapting a Workshop Planning Process to Hawai‘i

Tropical island ecosystems are highly vulnerable to the multiple threats of climate change (Nurse et al. 2014; Bonan 2008). In response, agencies and organizations are tasked with developing land-management strategies to help ecosystems adapt to changing environmental conditions (Swanston et al. 2016). Research has shown that proactive planning can reduce climate change impacts by facilitating more efficient and rapid responses (Bierbaum et al. 2013). Complex socio-ecological conditions, environmental change related stressors (e.g., wildfire, pests, disease, and drought), a lack of resources, and shifting public policy and agency mandates (Nagel et al. 2017) can all hinder response effectiveness (Crausbay et al. 2020). Despite these challenges, considerable progress has been made in assessing climate vulnerabilities of forest ecosystems and in developing adaptation options for land managers (Swanston and Janowiak 2012; Janowiak et al. 2014; Swanston et al. 2016; Halofsky et al. 2018; Schmitt et al. 2021). Adaptation planning in response to significant anticipated changes is becoming increasingly sophisticated, especially with respect to anticipated changes in forest wildfire regimes, species invasion, species composition, ecosystem health, and hydrological functioning due to climate change. Here we describe our conversion of a highly successful adaptation workshop process (Schmitt et al. 2021) to a virtual environment in response to COVID-19. We effectively delivered content to managers and created an experiential learning environment in which they developed adaptation tactics for their management projects, integrating Indigenous science and knowledge into the workshop format and content. This workshop was additionally novel because it used an adaptation process (Janowiak et al. 2014, Ontl et al. 2018) that has been applied many times in the continental U.S. within primarily temperate and sub-boreal systems (https://forestadaptation.org/), and applied it for the first time to a tropical island system.

Purification efficiency of eight aquatic plant species in an artificial floating island system in relation to extracellular enzyme activity and microbial community

The floating island system exploits the combination of aquatic plants, microorganisms, and extracellular enzymes to purify wastewater. We investigated the purification efficiency of eight aquatic plant species cultured in wastewater. The relationships of plant purification capacity with extracellular enzyme activity and microbial community were analyzed to explore the crucial factors that affect the plant purification capacity and the mechanism of pollutants removal in different plant systems. Three plant species, namely Oenanthe javanica, Thalia dealbata, and lris pseudacorus, were most effective for purification of ammonium-nitrogen (NH4⁺-N), total phosphate (TP), and chemical oxygen demand (COD) with maximum efficiencies of 76.09, 85.87, and 89.10%, respectively. Urease, alkaline phosphatase (AP), and β-glucosidase activities were significantly and positively correlated with root system development (P < 0.05). Activities of urease and AP were positively correlated with NH4⁺-N and TP removal, respectively. The magnitude of urease and AP activity was generally consistent with the plant’s capacity to remove NH4⁺-N and TP. β-Glucosidase activity and COD removal were not significantly correlated. The dominant microbial phylum in each species treatment was Proteobacteria. Alphaproteobacteria and Bacteroidia showed > 1% relative abundance and greater involvement in degradation of pollutants in the experimental system.

Endogenous Approach of a Frequency-Constrained Unit Commitment in Islanded Microgrid Systems

Power reserves are usually scheduled in day-ahead unit commitment (UC) to minimize operating costs while maintaining system security. In applying basic UC (bUC) after a contingency, the system frequency may fall upon the activation of the load-shedding global control (under-frequency load-shedding or UFLS) limits. Small isolated microgrids are more sensitive to this issue due to their lack of inertia. Including dynamic considerations into the bUC problem can minimize UFLS activation and also avoid the need for the operator to later check the short-term feasibility of a bUC solution. These proposals are known as Frequency-Constrained UC (FCUC), although the implementation are very time-consuming. FCUC implementation will increase the system’s operational costs, which should be calculated to estimate remuneration to the safety service based on the additional reserve provision. The electrical system of Gran Canaria island has suffered several episodes of greater blackouts in recent years. Shortly, there will be 242 MW of wind generation installed (26% of the thermal power installed on Gran Canaria). The main objective of this work is to improve the island system reliability by means of an FCUC formulation applied by the system operator in practice, including renewable sources. The results show that the frequency values remained within the admissible boundaries, but the system’s operational costs increased by around 13%.

Tracking Barrier Island Response to Early Holocene Sea-level Rise: High Resolution Study of Estuarine Sediments in the Trinity River Paleovalley

Understanding how barrier islands respond to factors such as variations in sediment supply, relative sea-level rise, and accommodation is valuable for preparing coastal communities for future impacts of climate change. Increasingly, the underlying antecedent topography has been observed to have a significant control on the evolution of the barrier island system by providing increased elevation, decreased accommodation, and sediment supply for the barrier to rework and anchor upon. However, less attention has been focused on how back barrier sediments respond to this decreased accommodation, and how this may affect barrier island evolution. Additionally, the control in which the geometry of the underlying valley itself has on the initiation of barrier islands is poorly understood. Here we examine the stratigraphic framework of the Trinity River incised valley, offshore Galveston, Texas in order to investigate the role of antecedent topography in the evolution of an ancient barrier island system. We present high-resolution imaging of the Trinity incised valley fill using over 1200 km2 of 3D seismic, <700 km of 2D envelope and full waveform chirp data, along with 2 piston cores, 4 gravity cores, 1 platform boring, with associated grain size, foraminiferal, and radiocarbon data. We find that the geometry and elevation of the underlying antecedent topography plays a central role in the evolution of the barrier island system, promoting both initiation and stabilization. This study provides a methodology to investigate the evolution of a relict barrier island system where little to none of the barrier is preserved. With this methodology, we revise the established Holocene paleoshoreline model for the Trinity incised valley.

Ecological specialization, rather than the island rule, explains morphological diversification in an ancient radiation of geckos

Island colonists are often assumed to experience higher levels of phenotypic diversification than their continental sister taxa. However, empirical evidence shows that exceptions to the familiar "island rule" do exist. In this study, we tested this rule using a nearly complete sampled mainland-island system, the genus Pristurus, a group of sphaerodactylid geckos mainly distributed across continental Arabia and Africa and the Socotra Archipelago. We used a recently published phylogeny and an extensive dataset of morphological measures to explore whether island and mainland taxa share the same morphospace or if they present different dynamics of phenotypic evolution. Moreover, we used habitat data to examine if ecological specialization is correlated with morphological change, reconstructing the ancestral habitat states across the phylogeny to compare the level of phenotypic disparity and trait evolution between habitats. We found that insular species do not present higher levels or rates of morphological diversification than continental groups. Instead, habitat specialization provides insight into the evolution of body size and shape in Pristurus. In particular, the adaptation to exploit ground habitats seems to have been the main driver of morphological change, producing the highest levels of disparity and evolutionary rates. Additionally, arboreal species show very constrained body size and head proportions, suggesting morphological convergence driven by habitat specialization. Our results reveal a determinant role of ecological mechanisms in morphological evolution and corroborate the complexity of ecomorphological dynamics in mainland-island systems.