Environmental Stability and Long-term Variability of Harpacticoid Copepod Assemblages

Harpacticoid copepods of the Chernaya Bay (White Sea) intertidal zone were collected in 45 surveys carried out from spring to autumn over a 25-year period (1996-2020) at three sites that differed in sediment properties. There were no significant long-term trends or seasonal cycles in total abundance. Regarding the species composition, the differences between sites were the most important source of variability over the whole period while the fine-scale (within-habitat) variability was low. Epibenthic species prevailed in fine silty sand, both burrowing and epibenthic species prevailed in medium sand, and interstitial and burrowing species prevailed in coarse sand. A comparison of the data on harpacticoid assemblages from a number of geographically remote loci corroborated the generality of this pattern. In the temporal dimension, the structure of each community was stable until the early 2000s, when the proportion of epibenthic, burrowing and interstitial species changed following changes in sediment properties (increasing siltation at sandy sites and decreasing siltation at the silty site). At each site, there was an increasing long-term trend in diversity (both in total richness and in expected species number). This increase was particularly apparent at sandy sites because of the appearance of epibenthic species. We suggest that sediment composition is the key factor determining the composition of harpacticoid assemblages in space and time. The “ecomorphological profile”, i.e., the proportion of species with different lifestyle and morphological traits, is a useful and informative indicator for describing and typifying these assemblages.

Monsoon Variability Reconstructed from Sedimentological and Mineral Magnetic Studies from Vaghad Tank Deposits, Nashik District, Maharashtra

An attempt made to reconstruct the monsoon variability using sedimentological, geochemical and mineral magnetic studies from deposits in Vaghad Tank, Nashik district, Maharashtra (India). The ~140 years multi-proxy data of the 3.3 meter thick sedimentary section of the tank exhibits some minor changes in sediment characteristics up to the depth of ~150 cm. The grain-size analysis and mineral magnetic studies of 67 samples of sediment suggests that, the sediment dominated by clay. Overall, sedimentary profile does not exhibit any systematic trend in the sediment properties. Finally, the present study concludes no significant changes in the past monsoon conditions have been occurred during the last century but some minor changes in the hydrodynamic conditions have been noticed during the last few decades.

Synergetic CT, XRF and Geoelectric Imaging for Non-Destructive Soil and Sediment Stratigraphic Study

This paper presents the application of three non-destructive techniques in the study of an agricultural area on the west coast of Peloponnese, Greece. The applied methods include (a) electromagnetic geophysical research using a handheld EM profiler (EMP-400 GSSI), (b) computed tomography (CT) with coring data, and (c) X-ray Fluorescence (XRF) scanning. As electrical conductivity is mainly influenced by the bulk soil, including water content, clay content and mineralogy, organic matter, and bulk density, a comparison of the three applied techniques indicates the same soil stratification and same soil properties with depth. Moreover, the ground-truthing by the undisturbed soil and sediments core retrieved in the centre of the site as well as the laboratory analyses of soil and sediment properties confirm the reliability of the geophysical research and the revealed soil/sediment stratification.

Prediction Models for Evaluating the Uptake of Heavy Metals by the Invasive Grass Vossia cuspidata (Roxb.) Griff. in the River Nile, Egypt: A Biomonitoring Approach

This study aimed to develop new prediction models that include sediment properties (pH, organic matter, and silt and clay concentrations) for estimating the potential uptake of heavy metals (HMs) by the invasive grass Vossia cuspidata. Plant and sediment samples were collected from the microsites that represent the natural distribution of the species in two Nile islands in Cairo, Egypt. The results show that the root was the main accumulating organ for the analyzed HMs (Fe, Mn, Zn, Cu, Ni, and Pb). The mean concentrations of Fe and Mn and the maximum concentrations of Cu, Ni, and Pb were phytotoxic. The values of the bioconcentration factor were >1, while the translocation factor was >1 for Zn and Cu in rhizome and stem, Mn in leaf, and Ni and Pb in stem and leaf. There were no significant differences between the measured and the predicted HM concentrations in all organs of the species. This indicates the excellent robustness of the developed regression models. Sixteen equations (out of 24) had high R2 values. Thus, V. cuspidata could be considered a biomonitor for HM pollution, and the developed equations will benefit the prediction of HM uptake by the species in the River Nile ecosystem.

Predicted Mapping of Seabed Sediments Based on MBES Backscatter and Bathymetric Data: A Case Study in Joseph Bonaparte Gulf, Australia, Using Random Forest Decision Tree

Predictive mapping of seabed sediments based on multibeam bathymetric (BM), and backscatter (BS) data is effective for mapping the spatial distribution of the substrate. A robust modeling technique, the random forest decision tree (RFDT), was used to predict the seabed sediments in an area of the Joseph Bonaparte Gulf, Northern Australia, using the multibeam data and seabed sediment samples collected simultaneously. The results showed that: (1) Using multibeam bathymetry data in addition to multibeam backscatter data improves the prediction performance of the RFDT. In comparison to only multibeam backscatter data, the prediction performance achieved a ~10% improvement in sediment properties; it achieved a ~44.45% improvement of overall accuracy in sediment types, and a ~0.55 improvement in Kappa. (2) The underlying relationships between sediment properties and multibeam data show that there is an opposite non-linear correlation between sediment property-BS and sediment property-BM. For example, there is an obvious negative relationship between %mud-BS at incidence angles of 13° and 21°, but the relationship between %mud-BM is positive. As such, the RFDT is a useful and well-performing method in predicting the relationship between sediment properties and multibeam data and in predicting the distribution of sediment properties and types. However, the sediment prediction method in deep-water areas with high gravel content needs to be further evaluated.