Quantifying Marine Plastic Debris in a Beach Environment Using Spectral Analysis

Marine plastic debris (MPD) is a globally relevant environmental challenge, with an estimated 8 million tons of synthetic debris entering the marine environment each year. Plastic has been found in all parts of the marine environment, including the surface layers of the ocean, within the water column, in coastal waters, on the benthic layer and on beaches. While research on detecting MPD using remote sensing is increasing, most of it focuses on detecting floating debris in open waters, rather than detecting MPD on beaches. However, beaches present challenges that are unique from other parts of the marine environment. In order to better understand the spectral properties of beached MPD, we present the SWIR reflectance of weathered MPD and virgin plastics over a sandy substrate. We conducted spectral feature analysis on the different plastic groups to better understand the impact that polymers have on our ability to detect synthetic debris at sub-pixel surface covers that occur on beaches. Our results show that the minimum surface cover required to detect MPD on a sandy surface varies between 2–8% for different polymer types. Furthermore, plastic composition affects the magnitude of spectral absorption. This suggests that variation in both surface cover and polymer type will inform the efficacy of beach litter detection methods.

Evaluation and Intercomparison of Topographic Correction Methods Based on Landsat Images and Simulated Data

Topographic effects in medium and high spatial resolution remote sensing images greatly limit the application of quantitative parameter retrieval and analysis in mountainous areas. Many topographic correction methods have been proposed to reduce such effects. Comparative analyses on topographic correction algorithms have been carried out, some of which drew different or even contradictory conclusions. Performances of these algorithms over different terrain and surface cover conditions remain largely unknown. In this paper, we intercompared ten widely used topographic correction algorithms by adopting multi-criteria evaluation methods using Landsat images under various terrain and surface cover conditions as well as images simulated by a 3D radiative transfer model. Based on comprehensive analysis, we found that the Teillet regression-based models had the overall best performance in terms of topographic effects’ reduction and overcorrection; however, correction bias may be introduced by Teillet regression models when surface reflectance in the uncorrected images do not follow a normal distribution. We recommend including more simulated images for a more in-depth evaluation. We also recommend that the pros and cons of topographic correction methods reported in this paper should be carefully considered for surface parameters retrieval and applications in mountain regions.

Sr isotopes in the Tortonian-Messinian Lake Bira and Gesher marshes, Northern Valleys of Israel: Implications for hydroclimate changes in East Mediterranean−Levant margins

87Sr/86Sr isotope and Sr/Ca ratios in lacustrine carbonates were used to reconstruct the hydroclimate conditions in the watershed of Lake Bira that filled during the Tortonian-Messinian the tectonic depressions of the Northern Valleys of Israel in the East Mediterranean-Levant region. 87Sr/86Sr ratios of the Tortonian (ca. 10−8 Ma) carbonates of ∼0.7075 and the great expansion of the lake indicate wet conditions and enhanced supply of freshwater from the regional Mesozoic aquifers. Upon the transition to the Messinian period (ca. 7−6 Ma), the 87Sr/86Sr ratios in the carbonates rose to ∼0.7080−0.7085, reflecting the contribution of Sr from Sahara Desert dusts that came to comprise the regional surface cover. This contribution is also reflected in the silicate fraction of the lacustrine formations that show “granitic-crustal” 87Sr/86Sr ratios of ∼0.711. During the Messinian salinity crisis (5.9−5.6 Ma), the region became arid and Lake Bira possibly dried. Later, during the Lago Mare stage (ca. 5.5−5.3 Ma), the rainfall increased and paludal waterbodies scattered the area of the larger Lake Bira.

Implications of 2D versus 3D surveys to measure the abundance and composition of benthic coral reef communities

A paramount challenge in coral reef ecology is to estimate the abundance and composition of the communities residing in such complex ecosystems. Traditional 2D projected surface cover estimates neglect the 3D structure of reefs and reef organisms, overlook communities residing in cryptic reef habitats (e.g., overhangs, cavities), and thus may fail to represent biomass estimates needed to assess trophic ecology and reef function. Here, we surveyed the 3D surface cover, biovolume, and biomass (i.e., ash-free dry weight) of all major benthic taxa on 12 coral reef stations on the island of Curaçao (Southern Caribbean) using structure-from-motion photogrammetry, coral point counts, in situ measurements, and elemental analysis. We then compared our 3D benthic community estimates to corresponding estimates of traditional 2D projected surface cover to explore the differences in benthic community composition using different metrics. Overall, 2D cover was dominated (52 ± 2%, mean ± SE) by non-calcifying phototrophs (macroalgae, turf algae, benthic cyanobacterial mats), but their contribution to total reef biomass was minor (3.2 ± 0.6%). In contrast, coral cover (32 ± 2%) more closely resembled coral biomass (27 ± 6%). The relative contribution of erect organisms, such as gorgonians and massive sponges, to 2D cover was twofold and 11-fold lower, respectively, than their contribution to reef biomass. Cryptic surface area (3.3 ± 0.2 m2 m−2planar reef) comprised half of the total reef substrate, rendering two thirds of coralline algae and almost all encrusting sponges (99.8%) undetected in traditional assessments. Yet, encrusting sponges dominated reef biomass (35 ± 18%). Based on our quantification of exposed and cryptic reef communities using different metrics, we suggest adjustments to current monitoring approaches and highlight ramifications for evaluating the ecological contributions of different taxa to overall reef function. To this end, our metric conversions can complement other benthic assessments to generate non-invasive estimates of the biovolume, biomass, and elemental composition (i.e., standing stocks of organic carbon and nitrogen) of Caribbean coral reef communities.

Morphological Types Of Central Asian Deserts And Their Geographical Aspects

This article provides detailed information on the types of deserts formed by the soil and surface cover deposits in the natural geographical region of Central Asia and their specific geographical features.

Towards the Spectral Mapping of Plastic Debris on Beaches

Floating and washed ashore marine plastic debris (MPD) is a growing environmental challenge. It has become evident that secluded locations including the Arctic, Antarctic, and remote islands are being impacted by plastic pollution generated thousands of kilometers away. Optical remote sensing of MPD is an emerging field that can aid in monitoring remote environments where in-person observation and data collection is not always feasible. Here we evaluate MPD spectral features in the visible to shortwave infrared regions for detecting varying quantities of MPD that have accumulated on beaches using a spectroradiometer. Measurements were taken from a range of in situ MPD accumulations ranging from 0.08% to 7.94% surface coverage. Our results suggest that spectral absorption features at 1215 nm and 1732 nm are useful for detecting varying abundance levels of MPD in a complex natural environment, however other absorption features at 931 nm, 1045 nm and 2046 nm could not detect in situ MPD. The reflectance of some in situ MPD accumulations was statistically different from samples that only contained organic debris and sand between 1.56% and 7.94% surface cover; however other samples with similar surface cover did not have reflectance that was statistically different from samples containing no MPD. Despite MPD being detectable against a background of sand and organic beach debris, a clear relationship between the surface cover of MPD and the strength of key absorption features could not be established. Additional research is needed to advance our understanding of the factors, such as type of MPD assemblage, that contribute to the bulk reflectance of MPD contaminated landscapes.

Hybrid watermilfoil (Myriophyllum spicatum × Myriophyllum sibiricum) exhibits traits associated with greater invasiveness than its introduced and native parental taxa

Hybridization has been associated with increased invasiveness in plants. In North America, the hybrid aquatic plant Myriophyllum spicatum × Myriophyllum sibiricum (hybrid watermilfoil, hereafter HWM) is a cross between non-native invasive Eurasian watermilfoil (M. spicatum, EWM) and native northern watermilfoil (M. sibiricum, NWM). Lab-based trials have demonstrated higher growth rates in HWM compared to EWM and NWM, but these patterns have not been systematically examined in the field. In this study, we compared the invasiveness of HWM to its parental taxa, EWM and NWM, by examining the amount and timing of: (1) flowering, (2) surface cover, and (3) biomass (using stem counts as a proxy). We conducted repeat surveys of Myriophyllum beds at eight lakes (2–3 lakes/taxon) in the Minneapolis–St. Paul Metropolitan area (Minnesota, USA) between June 2017 and November 2018. HWM produced more flower spikes earlier and overall, and maintained consistently more flower spikes throughout the growing season than EWM and NWM. In addition, surface cover reached greater annual peaks and was higher for longer throughout the growing season for HWM than for both parental taxa. We did not observe a significant difference in stem counts among the three taxa, but HWM did reach a higher maximum number of stems than either parental taxon. This study provides field-based evidence of increased invasiveness associated with hybridization between EWM and NWM; specifically, greater reproductive potential via flowering and greater surface cover may increase HWM spread, have greater impacts on native species, and pose more of a nuisance to lake users.

PRISMA Hyperspectral – First insights in the performance in urban surface cover and coastal seascape analysis

<p>The characterization of the Earth’s surface cover based on predefined classes is among the fundamental activities in the domain of satellite image analysis image since the early 70s. It was the joint NASA/ U.S. Geological Survey Landsat series of Earth Observation satellites that start to continuously acquired images of the Earth's land surface, providing uninterrupted data to help land managers and policymakers make informed decisions about natural resources and the environment. However, in 2020, the collected data even if are of continuous flow in terms volume of terrabytes per day from various optical and radar systems, are limited in terms of spectral resolution since almost all sensors are limited to a maximum of 25 spectral channels in the visible, near-and-shortwave-and-thermal infrared spectrum. The need of denser spectral information has been highlighted in early 80s and the first satellite-based hyperspectral sensor, AVIRIS, start to provide data allowing the extraction information on material composition and precise surface cover information. Since then few attempt appear but more are undergoing for launching. In 2019, the Italian Space Agency launch the PRISMA hyperspectral satellite which collect spectral data in the 400-2500nm spectrum; in total 250 spectral channels with a spectral width of ~ 12nm, at 30m pixel size. Here we present first results of the use of Level 2D PRISMA hyperspectral data in mapping the surface characteristics of the urban and periurban area of Heraklion city along with the coastal zone of the urban front aiming at the simultaneous creation of a land-and-coastal cover map along with the extraction of coastal bathymetry information using artificial intelligence approaches within open access platforms. The use of hyperspectral information allow the separation of urban surfaces based on material signatures, while the availability of dense spectral information in the blue-green spectrum allow the more accurate retrieval of coastal seascape characteristics. It is envisaged that hyperspectral missions soon to be the normal in Earth Observation, allowing the accurate creation of geospatial information for further use in several applications.</p>