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Marine macrophytes help protect coastal habitats by modifying the energy of their environment, attenuating wave action, and stabilizing the sediment. The aim of this research was to examine the effect of the above ground parts of different seagrass and seaweed species on the deposition, retention, physical (dry bulk density and grain size), and chemical properties (organic carbon content and organic carbon density) of sediment. Six seagrass and seaweed communities with different above ground morphologies were studied between the dry (April 2015) and wet seasons (August 2015). The results suggested that the highest canopy complexity index was in the green alga, Halimeda macroloba Decaisne patches, which had the highest canopy score. High canopy complexity patches were likely to retain more sediment and store more organic carbon than lower canopy complexity patches and bare sand, respectively. The sediment retention and percent of organic carbon content were also affected by seasons. The wave action in the wet season affected the sediment through higher sediment deposition and movement, which caused increased sediment instability and led to changes in sediment properties. In addition, shoot density in the dry season was lower than that in the wet season, most likely due to damage from long exposure during low tide. Our results indicate that the canopy complexity of marine macrophytes and seasons influenced both sediment retention and properties of the sediment. This study examined the effect of canopy complexity of seaweed and seagrass species on deposition, retention, physical and chemical properties of sediment. We examined the canopy complexity index using leaf morphology, dimension of shoot and number of canopy level together with mean leaf length and plant coverage. The results suggested that greater canopy complexity was likely to retain more sediment and store more organic carbon. [ABSTRACT FROM AUTHOR]

The use of sediment quality guidelines to predict the toxicity of metals in sediments is limited by an inadequate understanding of exposure pathways and by poor causal links between exposure and effects. For a 10-d exposure to Cu-spiked sediments, toxicity to the amphipod Melita plumulosa was demonstrated to occur through a combination of dissolved and dietary Cu exposure pathways, but for the bivalves Spisula trigonella and Tellina deltoidalis, toxicity occurred primarily by exposure to dissolved Cu. For relatively oxidized sediments that had moderate amounts of organic carbon (2.6-8.3% OC), silt (20-100% <63-µm particles) but low acid-volatile sulfide (AVS), acute toxicity thresholds for the three species were derived based on the OC-normalized Cu concentration of the less than 63-µm sediment fraction. For all three species, no effects were observed at concentrations below 10 µg/L dissolved Cu (in pore water and overlying water) or below 12 mg Cu/g OC (for <63 µm sediment). For sediments with silt/OC properties of 20/0.5, 50/1, or 70/4%, the particulate Cu-based threshold equated to 60, 120, or 480 mg Cu/kg, respectively. For oxic/suboxic sediments in which AVS is not limiting metal availability, sediment quality guidelines of this form will provide adequate protection against toxicity and improve the prediction of effects for sediments with varying properties. Environ. Toxicol. Chem. 2011; 30:1599-1610. © 2011 SETAC [ABSTRACT FROM AUTHOR]

Fossil footprints appear in a variety of preservational states, each revealing a different morphology that can give rise to misidentification and misinterpretations. Comparative ichnological work was conducted using living emus ( Dromaius novaehollandiae). It was clearly demonstrated that the morphological variation that occurred in footprints of the same animal, walking in the same manner, was caused by variation in substrate consistency. Dry sand substrates are unlikely to preserve any anatomical details of the foot, whereas damp sand or mud of firm consistency preserves a high level of anatomical detail. The finest anatomical details, such as skin impressions, are only preserved in firm mud or clay. In semi-fluid to fluid mud the track walls collapse, destroying the shape of the footprint. Increased speed of progression affects the shape of the footprint dramatically as the distal ends of the digits become more deeply impressed in the substrate during acceleration. Plantigrade stance adopted by the emu while feeding produces highly elongated footprints. Applying these observations to the study of fossil footprints demonstrates that great care should be paid to the original sedimentary conditions at the time of track making, as well as to the stance and gait of the trackmaker. [ABSTRACT FROM AUTHOR]

The oceanographic Polar Front separates the East Greenland and Iceland margins. Surface water temperatures across Denmark Strait vary by 8–12 °C and represent one of the steepest oceanographic gradients on earth. The East Greenland margin is a polar environment, with extensive sea-ice cover and calving glacier margins; in contrast, the Iceland shelf is much more temperate, and freshwater run-off is a key component in land–ocean sediment transfers. Average sediment properties from these two contrasting climate and oceanographic continental shelf environments are compared in the spatial domain at 13 sites; the data represent the last 10 000 radiocarbon years of `normal' marine sedimentation for the two regions. The two regions have similar average rates of sediment accumulation (around 43·5 cm kyr-1 ), so that this key variable is factored out in explaining any differences in sediment properties. Dry sediment density, moisture content, hygroscopic moisture, total organic carbon and carbonate contents, mass magnetic susceptibility and the percentages of sand and silt are compared focusing on: (1) median values for sediment properties; and (2) downcore variability, measured by the coefficient of variation (CV). There are significant differences in all but one (hygroscopic moisture) of the sediment properties between Iceland and East Greenland; in four cases, the sense of the differences was not as predicted. In terms of downcore variation (CV), no difference was found between the two regions, nor between the 13 sites, whereas there are some significant differences between the variables. Carbonate and mass magnetic susceptibility have the largest spreads, and moisture content and dry sediment density are the least variable. Protocols are developed to identify the `type core' in a regional series of sites. The results indicate a need to develop a regional perspective on sediment properties, both as inputs to models of sedimentary... [ABSTRACT FROM AUTHOR]

The emerging pollutants antibiotic resistance genes (ARGs) are prevalent in aquatic environments such as estuary. Coastal mangrove ecosystems always serve as natural wetlands for receiving sewage which always carry ARGs. Currently, the research considering ARG distribution in mangrove ecosystems gains more interest. In this work, we investigated the diversity of ARGs in an urban estuary containing mangrove and nonmangrove areas of the South China Sea. A total of 163 ARGs that classified into 22 resistance types and six resistance mechanisms were found. ARG abundance of the samples in the estuary is between 0.144 and 0.203. This is within the general range of Chinese estuaries. The difference analysis showed that abundances of total ARGs, six most abundant ARGs (mtrA, rpoB, rpoC, rpsL, ef-Tu, and parY), the most abundant resistance types (elfamycin, multidrug, and peptide), and the most abundant resistance mechanism (target alteration) were significantly lower in mangrove sediment than that in nonmangrove sediment (p < 0.05). Network and partial redundancy analysis showed that sediment properties and mobile genetic elements were the most influential factors impacting ARG distribution rather than microbial community. The two factors collectively explain 51.22% of the differences of ARG distribution. Our study indicated that mangrove sediments have the capacity to remove ARGs. This work provides a research paradigm for analysis of ARG prevalence and proliferation in the subtropical marine coastal mangrove ecosystem., (© 2019 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)