Nearshore Sediment Samples Research Articles

Factors driving the spatial distribution of microplastics in nearshore and offshore sediment of Lake Huron, North America

Offshore and nearshore sediment samples from Lake Huron, North America, were analysed for microplastics. Normalized abundances ranged from 59 to 335,714 particles per kg of dry weight sediment (p kg−1 dw). Of the four main basins of Lake Huron, the North Channel contained the greatest microplastic abundances, averaging 47,398 p kg−1 dw, followed by Georgian Bay (21,390 p kg−1 dw), the main basin (15,910 p kg−1 dw) and Saginaw Bay (1592 p kg−1 dw). Results indicate that greater lake depths (p = 0.004), associated with finer grained sediment (p = 0.048), are significant zones of deposition. Regression analysis reveals that source-driven factors generally do not account for microplastic abundances and distribution. Instead, process-driven hydrodynamic forces such as waves and surface currents could be driving distribution and deposition into the offshore environment. The findings suggest that these often overlooked processes should be considered when investigating microplastics quantity in bottom sediment of large lakes.

Lake level changes of Nam Co since 25 ka as revealed by OSL dating of paleo-shorelines

Many lakes in the Tibetan Plateau (TP) experienced dramatic lake level changes in the late Quaternary, as suggested by well-preserved paleo-shorelines up to ∼200 m above present lake levels. These relic shorelines provide direct geomorphic record to reconstruct past lake level fluctuation history and water volume changes, linked closely to variations in paleo-climatic controls including Asian monsoon, westerlies and glacial meltwater. In this study, 27 near-shore sediment samples from three of eight paleo-shorelines at north of Nam Co were dated by Optically Stimulated Luminescence (OSL) technique, using coarse grains of quartz and potassium feldspar. Our results indicate that: 1) S1 is the highest/most developed shoreline (+26 m). Sediment from upper part of S1 has a consistent age of ∼25 ka (nine samples from 3 gullies), suggesting a high lake level of Nam Co occurred around 25 ka. An overflow point west of Nam Co has a close elevation to that of S1 and thus limits the presence of higher lake levels; 2) sediment profile from the slightly lower S2 (+22 m) contains two parts, silty sand (6.9–8.9 ka) at the bottom and shoreline deposits atop (∼2.3 ka), suggesting Nam Co maintained a relative high lake level in the early Holocene and such lake level occurred again at about 3.0–2.0 ka; 3) In contrast to the swift variations of monsoon precipitation and glacial meltwater in the late Quaternary, water level of Nam Co remained relatively stable during the period from ∼25 ka to about early Holocene (from +26 m to +22 m), implying a continuous outflowing stage and lake infill constantly exceeds evaporation; 4) S5 (+11 m) has an age of 0.7–1.4 ka. Nam Co showed a much accelerated pace of shrinkage since about 2.0 ka in the late Holocene in roughly two steps: it dropped from +22 m to +11 m from ∼2.0 ka to 1.4 ka, and subsequently dropped another 11 m after 0.7 ka.

Effect of Extreme Weather Events on Contaminant Transport From Urban Run-Off to a Fjord System

Urbanization has resulted in increased contaminant run-off in densely populated areas. Climate change is expected to result in a higher frequency of extreme weather events including torrential rainfall and storms. The contaminant levels of polycyclic aromatic hydrocarbons (PAH), chlorinated paraffins (CPF) and selected metals, in a small urban river were monitored during snow-melting and rainfall events to quantify the contribution to the contamination load of receiving waters of the inner Oslo fjord, Norway. Suspended particulate matter (SPM) was characterized with respect to levels of contaminants as well as toxic response using a battery of bioassays. The contaminant flux from the river to the fjord was quantified and assessed relative to sediment data. Historic data for near-shore sediment samples from the fjord were used to document urban input. The results show a clear episodic response in contaminant load emitted from the river to the fjord. The main historic input to the fjord was found to be PAH from pyrogenic sources like coal and wood burning as well as traffic. A significant reduction in the level of PAH was observed since the 1980s. The measured flux of CPF is consistent with on-going societal use despite a ban on the use of short chain CPF imposed in Norway from 2002.

Distribution of microbial communities in metal-contaminated nearshore sediment from Eastern Guangdong, China

Nearshore environments are a critical transitional zone that connects the marine and terrestrial/freshwater ecosystems. The release of anthropogenic chemicals into nearshore ecosystems pose a human and environmental health risk. We investigated the microbial diversity, abundance and function in metal-contaminated sediments collected from the Rongjiang, Hanjiang and Lianjiang River estuaries and adjacent coastal areas using high throughput sequencing. The concentration of nutrients (NO3-N, NO2-N, NH4-N, PO4-P) and metal (Cu, Zn, Cd, Pb, As, Hg) contaminants were higher at the mouth of the rivers compared to the coastal lines, and this was confirmed using cluster analysis. Estimates obtained using geoaccumulation index showed that about 38.9% of the sites were contaminated with Pb and the pollution load index showed that sediment from the mouth of Hanjiang River Estuary was moderately polluted with metals. In the nearshore sediment samples collected, Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Acidobacteria were the dominant phylum with relative abundances of 46.6%, 8.05%, 6.47%, 5.26%, and 4.59%, respectively. There was no significant correlation between environmental variables and microbial abundance and diversity except for total organic carbon (TOC) (diversity; r = 0.569, p < 0.05) and Cr (diversity; r = 0.581, p < 0.05). At phyla level, Nitrospirae had a significant negative correlation with all metals except Cr, while OD1 had a significant positive correlation with all the metals. Overall, changes in nearshore sediment microbial communities by environmental factors were observed, and these may affect biogeochemical cycling.

Spatial heterogeneity in lipid biomarker distributions in the catchment and sediments of a crater lake in central India

The basin-scale spatial variability in lipid biomarker proxies in lacustrine sediments, which are established tools for studying continental environmental change, has rarely been examined. It is often implicitly assumed that a lake sediment core provides an average integral of catchment sources. Here we evaluated the distribution of lipid biomarkers in a modern ecosystem and compared it with the sedimentary record. We analyzed lipid biomarkers in terrestrial and aquatic organisms and in lake surface sediments from 17 locations within the saline–alkaline Lonar crater lake in central India. Terrestrial vegetation and lake surface sediments were characterized by relatively high average chain length (ACL) index values (29.6–32.8) of leaf wax n-alkanes, consistent with suggestions that plants in drier and warmer climates produce longer chain alkyl lipids than plants in cooler and humid areas. A heterogeneous spatial distribution of ACL values in lake surface sediments was found: at locations away from the shore, the values were highest (31 or more), possibly indicating different sources and/or transport of terrestrial biomarkers. In floating, benthic microbial mats and surface sediment, n-heptadecane, carotenoids, diploptene, phytol and tetrahymanol occurred in large amounts. Interestingly, these biomarkers of a unique bacterial community were found in substantially higher concentrations in nearshore sediment samples. We suggest that human influence and subsequent nutrient supply resulted in increased primary productivity, leading to an unusually high concentration of tetrahymanol in the nearshore sediments.In summary, the data showed that substantial heterogeneity existed within the lake, but leaf wax n-alkanes in a core from the center of the lake represented an integral of catchment conditions. However, lake level fluctuation may potentially affect aquatic lipid biomarker distributions in lacustrine sediments, in addition to source changes.

Shoreline foraminiferal thanatacoenoses around five eastern Caribbean islands and their environmental and biogeographic implications

Foraminiferal thanatacoenoses were examined around five islands in the Caribbean Sea, which forms a single biogeographic province with respect to nearshore (<3 m water depth) foraminifera, which live primarily on marine vegetation. On death, they become incorporated into the sediment. The assemblage at a site reflects the live assemblage and post mortem affects such as dissolution and transport during storms. Reefal species ( Amphistegina gibbosa, Asterigerina carinata) are transported towards shore during storms. Foraminiferal thanatacoenoses were examined in 65 nearshore sediment samples from around five eastern Caribbean islands: St. John (US Virgin Islands), St. Kitts, Nevis, Bequia and Tobago. Cluster and principal components analyses distinguished the following environments (indicator species in parentheses): 1. Sediment associated with mangroves ( Ammonia sobrina), 2. Bays subject to organic matter enrichment ( Quinqueloculina poeyana, Triloculina rotunda, T. trigonula), 3. Areas subject to moderate sediment flux during storms ( Quinqueloculina auberiana, Nodobaculariella mexicana, Peneroplis proteus, Archaias angulatus), 4. Locations subject to high sediment flux during storms ( Amphistegina gibbosa), 5. Sites little stressed by organic matter enrichment or storms ( Discorbis rosea). The majority of samples were from sites in the last category. The data from this study could form the nucleus of a catalogue of Caribbean beaches and their environmental influences.

Toxicity Evaluation with the Microtox ® Test to Assess the Impact of In Situ Oiled Shoreline Treatment Options: Natural Attenuation and Sediment Relocation

Changes in the toxicity levels of beach sediment, nearshore water, and bottom sediment samples were monitored with the Microtox ® Test to evaluate the two in situ oil spill treatment options of natural attenuation (natural recovery––no treatment) and sediment relocation (surf washing). During a series of field trials, IF-30 fuel oil was intentionally sprayed onto the surface of three mixed sediment (pebble and sand) beaches on the island of Spitsbergen, Svalbard, Norway (78°56 ′ N, 16°45 ′ E). At a low wave-energy site (Site 1 with a 3-km wind fetch), where oil was stranded within the zone of normal wave action, residual oil concentrations and beach sediment toxicity levels were significantly reduced by both options in less than five days. At Site 3, a higher wave-energy site with a 40-km wind fetch, oil was intentionally stranded on the beach face in the upper intertidal/supratidal zones, above the level of normal wave activity. At this site under these experimental conditions, sediment relocation was effective in accelerating the removal of the oil from the sediments and reducing the Microtox ® Test toxicity response to background levels. In the untreated (natural attenuation) plot at this site, the fraction of residual oil remaining within the beach sediments after one year (70%) continued to generate a toxic response. Chemical and toxicological analyses of nearshore sediment and sediment-trap samples at both sites confirmed that oil and suspended mineral fines were effectively dispersed into the surrounding environment by the in situ treatments. In terms of secondary potential detrimental effects from the release of stranded oil from the beaches, the toxicity level (Microtox ® Test) of adjacent nearshore sediment samples did not exceed the Canadian regulatory limit for dredged spoils destined for ocean disposal.

Petroleum hydrocarbons in the nearshore marine sediments of the United Arab Emirates

The concentrations of total petroleum hydrocarbons (TPH) were determined in nearshore sediment samples collected from 28 sampling sites along the United Arab Emirates shorelines on the Arabian Gulf, the Gulf of Oman and seven major creeks (khors) extending from them. Concentrations were highly variable and ranged between <0·4 and 212 μg g −1 dry weight, and the highest values obtained were in the top sediment (1 cm) layer near a fuel filling station and port areas. Locally high levels of TPH were found in Dubai, Sharjah and Ajman semi-enclosed creeks where boat activities and land-based wastewater discharges are most common. Data support the premise that port activities, fuel filling stations and land-based wastewater discharges are major sources of pollution in the study area. Correlations with sediment grain size, total organic carbon (TOC) and distance from pollution sources are discussed.

Baseline levels of heavy metals in the waters and sediments of Baffin Bay

Baseline levels of a number of trace metals have been determined in samples of water and sediment from Baffin Bay. Concentrations of Cr, Mn, Fe, Ni, Cu and Cd in the waters of Baffin Bay are generally lower than those observed in eastern Canadian coastal waters, levels being close to reported open ocean concentrations. Nearshore sediment samples, analysed for Cr, V, Mn, Ni, Co, Cu, Zn, Hg and Pb, display comparable concentrations to unpolluted muds in eastern Canadian coastal regions. Concentrations of these elements in the deep sediments of central Baffin Bay closely resemble levels in Atlantic Ocean deep-sea clays.

Origin of Gases Adsorbed in Near-Surface Sediment Identified by Carbon Isotopes: ABSTRACT

Carbon isotope ratios of gases desorbed from nearshore sediment samples collected from the Anadarko basin and from the North Sea have been determined by a technique recently developed in the Hannover laboratories. The results show a relation to geochemical data of the deep pooled hydrocarbons in both areas. Because of this relation, isotope analyses of adsorbed gases are of great interest in crude oil exploration. End_of_Article - Last_Page 701------------