Aquatic Applications Research Articles

Electrically-Shielded Coil-Enabled Battery-Free Wireless Sensing for Underwater Environmental Monitoring.

Battery-free wireless sensing in extreme environments, such as conductive solutions, is crucial for long-term, maintenance-free monitoring, eliminating the limitations of battery power and enhancing durability in hard-to-reach areas. However, in such environments, the efficiency of wireless power transfer via radio frequecny (RF) energy harvesting is heavily compromised by signal attenuation and environmental interference, which degrade antenna quality factors and detune resonance frequencies. These limitations create substantial challenges in wirelessly powering miniaturized sensor nodes for underwater environmental monitoring. To overcome these challenges, electrically-shielded coils with coaxially aligned dual-layer conductors are introduced that confine the electric field within the coil's inner capacitance. This configuration mitigates electric field interaction with the surrounding medium, making the coils ideal for use as near-field antennas in aquatic applications. Leveraging these electrically-shielded coils, a metamaterial-enhanced reader antenna was developed and a 3-axis sensor antenna for an near-field communication (NFC)-based system. The system demonstrated improved spectral stability, preserving resonance frequency and maintaining a high-quality factor. This advancement enabled the creation of a battery-free wireless sensing platform for real-time environmental monitoring in underwater environments, even in highly conductive saltwater with salinity levels of up to 3.5%.

Novel Eel Skin Fibroblast Cell Line: Bridging Adherent and Suspension Growth for Aquatic Applications Including Virus Susceptibility.

Suspension growth can greatly increase the cell density and yield of cell metabolites. To meet the requirements of aquatic industries, a culture model derived from Anguilla anguilla skin was developed using the explant outgrowth and enzyme-digesting passaging methods. These cells were kept in vitro continuously for over 12 months and subcultured 68 times. This heteroploid cell line, designated as ES, can naturally adapt to adherent and suspension growth reversibly under certain temperatures, serum percentages, and inoculum densities, without the need for any microcarriers or special medium additives. The ES cells can continue being highly productive under a temperature range of 15-37 °C and a serum percentage ranging from 3 to 15%. An inoculum density higher than 5 × 105 cells·mL-1 is necessary for the ES cells to turn into suspension efficiently. The green fluorescent protein (GFP) reporter gene was successfully expressed in the ES cells. The ES cells demonstrated susceptibility to Anguillid herpesvirus (AngHV) and red-spotted grouper nervous necrosis virus (RGNNV). ES is the first natural suspension growth model of aquatic origin; it does not require the processes of suspension domestication and carrier dissolution, making it a promising and cost-effective model for vaccine production, bio-pharmaceutical manufacturing, and cellular agriculture.

A comparison of detection probabilities for the patch‐nosed salamander (Urspelerpes brucei) using six survey methods

AbstractThe patch‐nosed salamander (Urspelerpes brucei), discovered in 2007, is a small amphibian endemic to northeast Georgia (GA) and northwest South Carolina (SC), USA. Given its recent discovery, little is known about the species’ conservation status. This is especially true in SC where this species is known from 4 stream localities in total, making monitoring and inventory a current priority. We applied 6 survey methods in 3 streams known to harbor the species (1 in GA; 2 in SC) using a randomized complete block design and conducted replicate surveys using each method 5 to 6 times between August 2021 and June 2022. We used occupancy models to estimate the probability of patch‐nosed salamanders using a randomly selected 5‐m stream segment while simultaneously investigating the effects of method and conditions on detectability. We recorded a total of 90 patch‐nosed salamander detections (60 from GA; 32 from SC) across 22 of the 39 stream segments in our study. Occupancy was similar in 2 streams (SCSouth: 0.94 [0.22 to −1.00 95% CI]; GARef: 0.70 [0.41–0.89 95% CI]) where it was also 3 to 4 times higher than in a third (SCNorth: 0.16 [0.04–0.47 95% CI]), though mechanisms driving the differences remain unclear. While we detected patch‐nosed salamanders with all 6 survey methods, aquatic and terrestrial versions of both leaf‐litter bags and area‐unconstrained surveys were more effective than randomized area‐constrained searches. Terrestrial applications of each method were biased toward adult detections while aquatic applications were biased toward larvae. Patch‐nosed salamander detectability was maximized during conditions (cloudless skies, >5 cm rainfall in the prior week, soil temperatures ≥20°C) that align with spring (March–June) in the species' range. A power analysis based on detectability estimates suggests that, under ideal sampling conditions, either 5 temporally replicated area‐unconstrained searches or a survey of 5 spatially replicated leaf‐litter bags (per 5‐m segment) are necessary to confirm presence‐absence of patch‐nosed salamanders with 90% confidence. Given that the 2 SC streams included in our study represent nearly half of the species’ range in that state, but collectively yielded only about one‐third of total detections and exhibited considerable disparity in occupancy, we recommend more work to clarify resource selection patterns, subpopulation stability, and potential threats to patch‐nosed salamanders in SC specifically.

Dynamics‐Oriented Underwater Mechanoreception Interface for Simultaneous Flow and Contact Perception

The lack of a sufficient and efficient way to simultaneously perceive general underwater mechanical stimuli, physical contact, and fluidic flow has been a bottleneck for many aquatic applications. To address this challenge, dynamics‐oriented underwater mechanoreceptor interface (DOUMI), a bioinspired mechanoreception system that realizes simultaneous contact and flow perception using a single receptor, is introduced. This receptor, response‐elevated‐and‐expanded hair‐like tactile mechanoreceptor (REEM), is inspired by the mechanoreceptive mechanism of aquatic arthropods. REEM combines structural features from different mechanoreceptive sensilla, enabling it to capture a wide range of stimulus dynamics. Under different stimuli, REEM encodes stimuli dynamics as its oscillations with distinct spectral attributes. Those oscillations are efficiently transferred through mechanical processes and imaging, enabling vision‐based extraction and further analysis. Therefore, by evaluating the oscillation dynamics with tailored wavelet‐based indices, DOUMI can distinguish between contact‐ and flow‐induced oscillations at each receptor unit with 90.5% accuracy. Furthermore, DOUMI provides comprehensive 2D mechanoreception with a scalable array of REEMs, delivering capabilities like stimuli spatiotemporal visualization, flow trend detection, and scenario classification with an accuracy of 99.5%. With its robustness and operational efficiency in underwater environments, DOUMI can be easily adapted to existing applications using common materials and hardware, establishing a new, streamlined paradigm for underwater general mechanoreception.

Ultrasonication-Boosted Resorcinol-Formaldehyde Resin Nanoparticle Bromine Fixation and Corresponding Upgraded Aquatic Applications.

Bromine (Br2) and related species removal from water systems are rather complicated due to the complicated chemistry instability, and materials with high Br2 removal rate and efficiency, along with stimuli/apparatus suitable for highly corrosive environments, are necessary. Ultrasonication as a non-destructive process is especially suitable in scenarios where conventional stir apparatus is not applicable, such as highly corrosive environments. Considering the validity nature of Br2 and combining the advantages of ultrasonic with a highly stable Br2 fixation method through aromatic polymer nanoparticles, we demonstrate highly efficient acoustic-aided Br2 removal in aqueous solutions with two times capacity compared to the non-treated sample. Related aquatic applications are also proposed for the materials to be cost-effective, including silver (Ag) recovery, recyclable MnO2-mediated Br2 deep removal, and aqueous zinc anode modification. The coupled novel-material-based processes motivate the strategic design of water purification with high-safety and sustainable industrial procedures and post-value-added utilizations.

Study of biological characteristics of an improved Japanese white crucian carp lineage derived from Carassius cuvieri (♀) × Megalobrama amblycephala (♂)

Based on the formation of fertile allotetraploid fish (4nJB, 4n = 148) derived from female Carassius cuvieri (JCC, 2n = 100) × male Megalobrama amblycephala (BSB, 2n = 48), an improved Japanese white crucian carp (IJCC) was obtained by mating female 4nJB and male 4nJB, and thus far, the population of IJCC has reached the fifth generations (F1–F5). The purpose of the present study was to comparatively investigate the biological characteristics of the IJCC lineage (F1–F5) and their original female parent JCC. The results of DNA content and chromosome numbers showed that the IJCC lineage was diploid with 100 chromosomes. For morphological characteristics, it appears that IJCC-F1 has smaller head and a higher body width than that of JCC, and some countable traits as well as the ratio of measurable traits were significantly different (P < 0.05) between these two fish. With the passing of generations, the appearance of the IJCC lineage has been stable. Regarding reproductive characteristics, the fecundity, sperm volume, sperm density, fertilization rate and hatching rate were not significantly different (P > 0.05) between the JCC and IJCC lineages, indicating that the reproductive capacity of the IJCC lineage was similar to that of the JCC. Furthermore, the growth performance showed that the average weight of IJCC-F1 and IJCC-F5 was significantly greater (P < 0.05) than that of JCC both at 6 months and 1 year of age. The good fertility of the IJCC lineage ensures the multigeneration utilization of its advantage, and the IJCC lineage has significant value in aquatic applications.

Highly Adhesive Epidermal Sensors with Superior Water‐Interference‐Resistance for Aquatic Applications

AbstractGrand challenges exist in the fabrication of robust skin electronics that are resistant to water interference, which can play vital roles in healthcare and lifesaving in activities such as showering, surfing, and swift water rescue. Particularly, dynamic water impingement is very destructive to skin electronics by causing device–skin delamination and sensing malfunctions. Herein, an anemone‐inspired self‐adhesive epidermal sensor with superior ability to resist water interference in various aquatic environments is developed. The epidermal sensor consists of a strain sensing layer composed of interconnected graphene flakes wrapped in ultrathin Ecoflex and a self‐adhesive layer composed of semi‐crosslinked polydimethylsiloxane, which is named as an adhesive graphene encapsulated in Ecoflex (a‐G@E) sensor. The a‐G@E sensor can conformally and stably attach on the skin under the synergy effect of the ultrathin thickness and the self‐adhesive layer. Remarkably, it can maintain a highly stable device–skin interface even under extreme aquatic conditions such as intense water impingement (up to 4 m s−1). As examples, this study demonstrates its applications in transmitting information, controlling robotics underwater, and tracking swimming modes of a fish. It is believed that the a‐G@E sensor can play a unique role in health‐care, sports‐monitoring, and human–machine interactions, especially for aquatic scenarios.

Evaluation of eight band SuperDove imagery for aquatic applications.

Planet's SuperDove constellation is evaluated for remote sensing of water targets. SuperDoves are small satellites with on board eight band PlanetScope imagers that add four new bands compared to the previous generations of Doves. The Yellow (612 nm) and Red Edge (707 nm) bands are of particular interest to aquatic applications, for example in aiding the retrieval of pigment absorption. The dark spectrum fitting (DSF) algorithm is implemented in ACOLITE for processing of SuperDove data, and its outputs are compared to matchup data collected using an autonomous pan-and-tilt hyperspectral radiometer (PANTHYR) installed in the turbid waters of the Belgian Coastal Zone (BCZ). Results for 35 matchups from 32 unique SuperDove satellites indicate on average low differences with PANTHYR observations for the first seven bands (443-707 nm), with mean absolute relative differences (MARD) 15-20%. The mean average differences (MAD) are between -0.01 and 0 for the 492-666 nm bands, i.e. DSF results show a negative bias, while the Coastal Blue (444 nm) and Red Edge (707 nm) show a small positive bias (MAD 0.004 and 0.002). The NIR band (866 nm) shows a larger positive bias (MAD 0.01), and larger relative differences (MARD 60%). Root mean squared differences (RMSD) are rather flat at around 0.01 with peaks in the bands with highest water reflectance of around 0.015. The surface reflectance products as provided by Planet (PSR) show a similar average performance to DSF, with slightly larger and mostly positive biases, except in both Green bands, where the MAD is close to 0. MARD in the two Green bands is a bit lower for PSR (9.5-10.6%) compared to DSF (9.9-13.0%). Higher scatter is found for the PSR (RMSD 0.015-0.020), with some matchups showing large, spectrally mostly flat differences, likely due to the external aerosol optical depth (τa) inputs not being representative for these particular images. Chlorophyll a absorption (aChl) is retrieved from PANTHYR measurements, and the PANTHYR data are used to calibrate aChl retrieval algorithms for SuperDove in the BCZ. Various Red band indices (RBI) and two neural networks are evaluated for aChl estimation. The best performing RBI algorithm, i.e. the Red band difference (RBD), showed a MARD of 34% for DSF and 25% for PSR with positive biases of 0.11 and 0.03 m-1 respectively for 24 PANTHYR aChl matchups. The difference in RBD performance between DSF and PSR can be largely explained by their respective average biases in the Red and Red Edge bands, which are opposite signs for DSF (negative bias in the red), and positive for both bands for PSR. Mapping of turbid water aChl and hence chlorophyll a concentration (C) using SuperDove is demonstrated for coastal bloom imagery, showing how SuperDove data can supplement monitoring programmes.

A Q-Learning-Based Hierarchical Routing Protocol With Unequal Clustering for Underwater Acoustic Sensor Networks

Underwater acoustic sensor networks (UASNs) have emerged as a viable networking approach due to their numerous aquatic applications in recent years. As a vital component of UASNs, routing protocols are essential for ensuring reliable data transmissions and extending the longevity of UASNs. Recently, several clustering-based routing protocols have been proposed to reduce energy consumption and overcome the resource constraints of deployed sensor nodes. However, they rarely consider the hot-spots’ problem and the sink node isolation problem in the multihop underwater sensor networks. In this article, we propose a Q-learning-based hierarchical routing protocol with unequal clustering (QHUC) for determining an effective data forwarding path to extend the lifespan of UASNs. First, a hierarchical network structure is constructed for initialization. Then, a combination of unequal clustering and the Q-learning algorithm is applied to the hierarchical structure to disperse the remaining energy more evenly throughout the network. With the use of the Q-learning algorithm, a global optimal CH and next-hop can be determined better than a greedy one. In addition, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> value that guarantees the optimal routing decisions can be computed without incurring any additional costs by combining the Q-learning algorithm with clustering. The simulation results show that the QHUC can achieve efficient routing and prolong the network lifetime significantly.

Thermal Adsorption and Corrosion Characteristic Study of Copper Hybrid Nanocomposite Synthesized by Powder Metallurgy Route

Novel constitutions of ceramic bond the new opportunity of engineering materials via solid-state process attaining enhanced material characteristics to overcome the drawback of conventional materials used in aquatic applications. The copper-based materials have great potential to explore high corrosion resistance and good thermal performance in the above applications. The main objectives of this research are to develop and enhance the characteristics of the copper-based hybrid nanocomposite containing different weight percentages of alumina and graphite hard ceramics synthesized via solid-state processing (powder metallurgy). The presence of alumina nanoparticles with a good blending process has to improve the corrosion resistance, and graphite nanoparticles may limit the weight loss of the sample during potentiodynamic corrosion analysis. The developed composite’s micro Vickers hardness is evaluated by the E384 standard on ASTM value of 69 Hv and is noted by increasing the weight percentages of alumina nanoparticles. The conduction temperature of actual sintering anticipates the thermogravimetric analysis of developed composite samples varied from 400°C to 750°C. The thermogravimetric graph illustration curve of the tested sample found double-step decomposition identified between 427°C and 456°C. The potentiodynamic analyzer is used to evaluate the corrosion behaviour of the sample and the weight loss equation adopted for finding the theoretical weight loss of the composite.

Using fiber-optic distributed temperature sensing in fisheries applications: An example from the Ozark Highlands

Studies of thermal selection by organisms, including fishes, are common and provide data that are useful for conservation and management. Advances in temperature sensing technology have improved these studies; however, the benefits of new technology (e.g., increased accuracy and greater deployment flexibility) should be carefully considered and compared to disadvantages (e.g., higher costs and training requirements). Fiber-optic distributed temperature sensing (FO-DTS) has become more common in aquatic applications and may provide a novel and useful method of relating thermal patchiness to habitat selection by fishes or other aquatic organisms. We present a case study using FO-DTS to conduct a microhabitat-scale resource selection study using stream fishes of the Ozark Highland ecoregion in the south-central United States. We describe the setup and deployment of FO-DTS and how it was integrated into traditional microhabitat survey methods at three stream sites that were repeatedly surveyed over consecutive days. We successfully used FO-DTS to characterize thermal selection by Neosho Bass Micropterus velox at our sites and conclude that the technology would be applicable to similar, microhabitat-scale evaluations. We then compare costs, benefits, and disadvantages of FO-DTS to other sensing methods that could have been used to complete our study. We found that FO-DTS provided accurate measures and greater coverage compared to most alternatives but that equipment costs were far greater. We provide suggestions for additional fisheries applications where FO-DTS may be useful while acknowledging that in some instances, the upfront costs of the technology may outweigh the potential benefits.

Comparative analysis of growth performance, pharyngeal teeth and intestinal traits in F1 hybrids of female Megalobrama amblycephala × male Culter mongolicus

Aquaculture provides approximately 78% of the fish consumed by humans in China. However, the characters of fish cultivars have different deficiencies, and degradation is serious. Less improved varieties of fish are still an important factor restricting the development of aquaculture in China. Interspecific hybridization is an effective method for producing hybrid varieties with desirable traits. In this study, diploid hybrids (BM, 2n = 48) of blunt snout bream (Megalobrama amblycephala ♀, 2n = 48, BSB) × Mongolian culter (Culter mongolicus ♂, MC, 2n = 48) were obtained by intergeneric crossing. To investigate whether these hybrids have heterobeltiosis, the growth performance, pharyngeal teeth and intestinal traits of BM hybrids were compared with those of their parents (BSB and MC). The average weight of BM hybrids (97.01 ± 27.52 g) was significantly greater (P < 0.05) than that of MC (68.04 ± 12.64 g) and similar to that of BSB (99.33 ± 16.72 g) at 1 year of age; the average weight of BM hybrids (990.49 ± 149.21 g) was significantly greater (P < 0.05) than that of both BSB (895.12 ± 135.38 g) and MC (625.81 ± 81.83 g) at 2 years of age. The pharyngeal tooth structure and intestinal traits of BM hybrids were similar to those of BSB, indicating that BM hybrids were biased toward herbivory. This is the first report of a diploid hybrid with a growth advantage and herbivory produced by crossing female BSB and male MC. The new hybrid offspring have great significance in aquatic applications.

Preferential interactions of surface-bound engineered single stranded DNA with highly aromatic natural organic matter: Mechanistic insights and implications for optimizing practical aquatic applications

Engineered short-chain single stranded DNA (ssDNA) are emerging materials with various environmental applications, such as aptasensor, selective adsorbent, and hydrological tracer. However, the lack of fundamental understanding on the interactions of such materials with natural organic matter (NOM) hinders the improvement of their application performance in terms of sensitivity, selectivity, and stability. In this study, we investigated the interactions of ssDNA (four strands with systematically varied length and sequence) with two humic acids (Suwannee River humic acid (SRHA) and Aldrich humic acid (AHA)) and two humic-like NOM present in local aquatic matrices (ROM in river water and WOM in wastewater). Detailed, molecular level interaction mechanisms were obtained by probing the colloidal stability of the ssDNA-coated gold nanoparticles, coupled with product characterization using a suite of microscopic and spectroscopic techniques. Our study revealed that π-π interactions and divalent cation bridging were the major mechanisms for ssDNA-NOM interactions. ssDNA preferentially interacted with NOM with high aromaticity (AHA > SRHA/WOM/ROM). With divalent cations present (especially Ca2+), even a small amount of AHA could completely shield ssDNA, whereas the extent of shielding by SRHA/WOM/ROM depended on the relative content of ssDNA and NOM and whether bridges formed. The extent of shielding of ssDNA by NOM provides a potential answer to the reported conflicting effects of natural water matrices on the performance of DNA-based sensors. Taken together, our findings provide insights into the transformations of engineered ssDNA under environmentally relevant conditions as well as implications for their performance optimization in practical aquatic applications (e.g., from DNA design to pretreatment strategy).

Recent Trends and Future Perspectives of Emergent Analytical Techniques for Mercury Sensing in Aquatic Environments.

Environmental emissions of mercury from industrial waste and natural sources, even in trace amounts, are toxic to organisms and ecosystems. However, industrial-scale mercury detection is limited by the high cost, low sensitivity/specificity, and poor selectivity of the available analytical tools. This review summarizes the key sensors for mercury detection in aqueous environments: colorimetric-, electrochemical-, fluorescence-, and surface-enhanced Raman spectroscopy-based sensors reported between 2014-2021. It then compares the performances of these sensors in the determination of inorganic mercury (Hg2+ ) and methyl mercury (CH3 Hg+ ) species in aqueous samples. Mercury sensors for aquatic applications still face serious challenges in terms of difficult deployment in remote areas and low robustness, reliability, and selectivity in harsh environments. We provide future perspectives on the selective detection of organomercury species, which are especially toxic and reactive in aquatic environments. This review is intended as a valuable resource for scientists in the field of mercury sensing.

HydroMoth: Testing a prototype low‐cost acoustic recorder for aquatic environments

AbstractPassive acoustic monitoring (PAM) involves recording the sounds of animals and environments for research and conservation. PAM is used in a range of contexts across terrestrial, marine and freshwater environments. However, financial constraints limit applications within aquatic environments; these costs include the high cost of submersible acoustic recorders. We quantify this financial constraint using a systematic literature review of all ecoacoustic studies published in 2020, demonstrating that commercially available autonomous underwater recording units are, on average, five times more expensive than their terrestrial equivalents. This pattern is more extreme at the low end of the price range; the cheapest available aquatic autonomous units are over 40 times more expensive than their terrestrial counterparts. Following this, we test a prototype low‐cost, low‐specification aquatic recorder called the ‘HydroMoth’: this device is a modified version of a widely used terrestrial recorder (AudioMoth), altered to include a waterproof case and customisable gain settings suitable for a range of aquatic applications. We test the performance of the HydroMoth in both aquaria and field conditions, recording artificial and natural sounds, and comparing outputs with identical recordings taken with commercially available hydrophones. Although the signal‐to‐noise ratio and the recording quality of HydroMoths are lower than commercially available hydrophones, the recordings with HydroMoths still allow for the identification of different fish and marine mammal species, as well as the calculation of ecoacoustic indices for ecosystem monitoring. Finally, we outline the potential applications of low‐cost, low‐specification underwater sound recorders for bioacoustic studies, discuss their likely limitations, and present important considerations of which users should be aware. Several performance limitations and a lack of professional technical support mean that low‐cost devices cannot meet the requirements of all PAM applications. Despite these limitations, however, HydroMoth facilitates underwater recording at a fraction of the price of existing hydrophones, creating exciting potential for diverse involvement in aquatic bioacoustics worldwide.

Handover Mechanism Based on Underwater Hybrid Software-Defined Modem in Advanced Diver Networks

For the past few decades, the internet of underwater things (IoUT) obtained a lot of attention in mobile aquatic applications such as oceanography, diver network monitoring, unmanned underwater exploration, underwater surveillance, location tracking system, etc. Most of the IoUT applications rely on acoustic medium. The current IoUT applications face difficulty in delivering a reliable communication system due to the various technical limitations of IoUT environment such as low data rate, attenuation, limited bandwidth, limited battery, limited memory, connectivity problem, etc. One of the significant applications of IoUT include monitoring underwater diver networks. In order to perform a reliable and energy-efficient communication system in the underwater diver networks, a smart underwater hybrid software-defined modem (UHSDM) for the mobile ad-hoc network was developed that is used for selecting the best channel/medium among acoustic, visible light communication (VLC), and infrared (IR) based on the criteria established within the system. However, due to the mobility of underwater divers, the developed UHSDM meets the challenges such as connectivity errors, frequent link failure, transmission delay caused by re-routing, etc. During emergency, the divers are most at the risk of survival. To deal with diver mobility, connectivity, energy efficiency, and reducing the latency in ADN, a handover mechanism based on pre-built UHSDM is proposed in this paper. This paper focuses on (1) design of UHSDM for ADN (2) propose the channel selection mechanism in UHSDM for selecting the best medium for handover and (3) propose handover protocol in ADN. The implementation result shows that the proposed mechanism can be used to find the new route for divers in advance and the latency can be reduced significantly. Additionally, this paper shows the real field experiment of air tests and underwater tests with various distances. This research will contribute much to the profit of researchers in underwater diver networks and underwater networks, for improving the quality of services (QoS) of underwater applications.

Reliable Data Transmission Scheme for Perception Layer of Internet of Underwater Things (IoUT)

Internet of Underwater things (IoUT) is growing into one of the most important research interests since the last few decades. The primary objective of IoUT is to develop a worldwide network of smart underwater-interconnected objects. It has wide-ranging aquatic applications, including surveillance, pollution reduction, monitoring offshore oil and gas pipelines, disaster prevention, and navigation assistance, making it as important as a terrestrial communication system. The underwater communication channel poses unique acoustic communication challenges that suffer from long propagation delay, low bandwidth, multipath, and fading. IoUT significantly differs from the conventional Internet of Things (IoT) due to disparate environmental conditions under the ocean that require re-designing the underwater communication channel model. In addition to the challenges mentioned above, end-to-end delay and efficient energy utilization are also of great concern. Therefore, in this research paper, diverse attributes of underwater acoustic communication, including the speed of sound, transmission loss, absorption, and ambient noise, are analyzed to design a channel model for underwater communication. These environmental conditions also make underwater acoustic channels highly variable, so efficient resources, including bandwidth and power, are required. Adaptive modulation is proposed to make the communications system efficient by considering the distance between nodes and the signal-to-noise ratio as channel state information. The proposed channel model critically analyzed the CSI factors, results show efficient bandwidth utilization and appropriate power consumption for the well-suited route. The proposed research also aims to reduce end-to-end propagation delay by considering vertical angle-based shortest path (efficient route) in the Multilevel rotating priority MRP-routing algorithm.

Evaluation of ACOLITE atmospheric correction methods for Landsat-8 and Sentinel-2 in the Río de la Plata turbid coastal waters

ABSTRACT Landsat-8 (L8) and Sentinel-2 (S2) terrestrial satellite missions have shown to contain useful information for aquatic applications. However, quantitative retrieval of water quality parameters, such as turbidity, strongly depend on the performance of atmospheric correction algorithms. Among available processors, ACOLITE (https://odnature.naturalsciences.be/remsem/software-and-data/acolite) is simple to incorporate in imagery processing routines and has shown to have better performance than other processors for sediment-rich waters. Recently (in 2018), it incorporated a new default atmospheric correction approach, the dark spectrum fit (DSF), which remains to be tested in most of the Southern hemisphere coastal areas. In this work, we present new in-situ radiometric measurements collected in the northern coast of the Río de la Plata estuary, South America, during field campaigns along a 2-year period. The data set was used to evaluate the performance of ACOLITE’s DSF and exponential extrapolation (EXP) methods with L8 and S2 imagery, and to recalibrate a turbidity algorithm. The DSF did not perform very well, giving particularly poor results in the near infrared (NIR) bands. However, its performance was greatly improved with an optional sun glint correction (DSF+GC), although some positive bias was still present in the NIR bands. A GC seemed to be most important in dates with higher sun elevation (austral spring and summer), and should be strongly considered for other water bodies in the region and in similar or lower latitudes (35°S). Additionally, the EXP method gave good results in the green-NIR spectral region when a low (5th) percentile aerosol type was selected. Finally, the effect of the atmospheric correction on turbidity retrieval from satellite imagery was assessed: if the red and a NIR band were combined, the effect of the bias in the NIR region was negligible for the DSF+GC method; however, some impact was noticed for the lowest turbidity levels if a single NIR band was used.

Complementary water quality observations from high and medium resolution Sentinel sensors by aligning chlorophyll-a and turbidity algorithms

High resolution imaging spectrometers are prerequisite to address significant data gaps in inland optical water quality monitoring. In this work, we provide a data-driven alignment of chlorophyll-a and turbidity derived from the Sentinel-2 MultiSpectral Imager (MSI) with corresponding Sentinel-3 Ocean and Land Colour Instrument (OLCI) products. For chlorophyll-a retrieval, empirical ‘ocean colour’ blue-green band ratios and a near infra-red (NIR) band ratio algorithm, as well as a semi-analytical three-band NIR-red ratio algorithm, were included in the analysis. Six million co-registrations with MSI and OLCI spanning 24 lakes across five continents were analysed. Following atmospheric correction with POLYMER, the reflectance distributions of the red and NIR bands showed close similarity between the two sensors, whereas the distribution for blue and green bands was positively skewed in the MSI results compared to OLCI. Whilst it is not possible from this analysis to determine the accuracy of reflectance retrieved with either MSI or OLCI results, optimizing water quality algorithms for MSI against those previously derived for the Envisat Medium Resolution Imaging Spectrometer (MERIS) and its follow-on OLCI, supports the wider use of MSI for aquatic applications. Chlorophyll-a algorithms were thus tuned for MSI against concurrent OLCI observations, resulting in significant improvements against the original algorithm coefficients. The mean absolute difference (MAD) for the blue-green band ratio algorithm decreased from 1.95 mg m−3 to 1.11 mg m−3, whilst the correlation coefficient increased from 0.61 to 0.80. For the NIR-red band ratio algorithms improvements were modest, with the MAD decreasing from 4.68 to 4.64 mg m−3 for the empirical red band ratio algorithm, and 3.73 to 3.67 for the semi-analytical 3-band algorithm. Three implementations of the turbidity algorithm showed improvement after tuning with the resulting distributions having reduced bias. The MAD reduced from 0.85 to 0.72, 1.22 to 1.10 and 1.93 to 1.55 FNU for the 665, 708 and 778 nm implementations respectively. However, several sources of uncertainty remain: adjacent land showed high divergence between the sensors, suggesting that high product uncertainty near land continues to be an issue for small water bodies, while it cannot be stated at this point whether MSI or OLCI results are differentially affected. The effect of spectrally wider bands of the MSI on algorithm sensitivity to chlorophyll-a and turbidity cannot be fully established without further availability of in situ optical measurements.

Terrestrial eDNA survey outperforms conventional approach for detecting an invasive pest insect within an agricultural ecosystem

AbstractRecent methodological advances permit surveys for terrestrial insects from the direct collection of environmental DNA (eDNA) deposited on vegetation or other surfaces. However, in contrast to well‐studied aquatic applications, little is known about how detection rates for such terrestrial eDNA‐based surveys compare with conventional survey methods. Lycorma delicatula, the spotted lanternfly, is an emerging invasive insect in eastern North America, and a significant ecological and economic pest of forested and agricultural systems, especially grapes. During fall 2019, we conducted two rounds of paired eDNA and visual surveys for spotted lanternflies within 48 plots at 12 vineyards in New Jersey, USA. We compared detection probabilities within a multimethod occupancy modeling framework and used the results to extrapolate and inform survey design. The probability of detecting spotted lanternflies given presence in a plot was over two times higher for eDNA (84%) versus visual surveys (36%). In mid‐September, lanternfly eDNA was detected at five plots in three vineyards, while visual surveys revealed only a single individual in one plot. In early October, after dispersal of lanternflies into vineyards, lanternfly eDNA was detected in 12 plots within six vineyards compared with visual detections in six plots in two vineyards. Extrapolations based on detection and local‐scale occupancy rates indicate that only five and 12 plots would have been needed to positively detect lanternfly presence with 95% confidence using eDNA in contrast to 14 and 29 plots with visual surveys alone, respective to survey rounds. Log‐linear models revealed that visual counts of lanternflies were positively related to eDNA concentrations (R2 = 71%). We provide some of the first quantitative evidence to support the enhanced sensitivity of terrestrial eDNA approaches compared with conventional methods. Such methods can augment efforts to combat invasive species through improved ability to delimit invasion fronts, identify satellite populations, and confirm local eradications.