Assessment of dissolved organic carbon and iron effects on water color between a forest and pasture-dominated fine-scale catchment in a Central Appalachian region, West Virginia

Hexabromocyclododecane in sediments from riverine, port, and coastal areas of Kaohsiung, Taiwan: levels, spatial distribution, and potential ecological risk

The widespread use of hexabromocyclododecane (HBCD), a brominated flame retardant, is a major public health concern because of the toxic, persistent, and bioaccumulative nature of HBCD. However, there is limited information available regarding the distribution and transportation of HBCD in sediments across various environmental settings, spanning from riverine to marine environments in the Kaohsiung area of Taiwan. In this study, we comprehensively investigated the level and distribution of and potential ecological risk posed by HBCD in surface sediments in the Kaohsiung area of Taiwan. In sediment samples from stations on the Love River and Kaohsiung Port area, the concentrations of HBCD ranged from 10.6 to 320.1 μg/kg dry weight (dw) and nondetectable (n.d.) to 58.4 μg/kg dw, respectively. The concentrations of HBCD in sediment collected from the M1, M2, and M3 sites, located in the Cijin coastal area, were 896.2 μg/kg dw, 3.2 μg/kg dw ( 1. The M1 site had the highest risk level (RQ = 5.27). These data suggest that domestic sewage and industrial wastewater discharge pose a potential risk to marine environments. Consequently, timely measures to control HBCD-related risks are required. Our study offers insight into the environmental effects of HBCD contamination of sediment and provides valuable information that can be used to guide environmental policy and safety measures.

Water quality and periphyton functional response to input of dissolved manure-derived hydrochars (DHCs)

Dissolved organic matter (DOM) plays a critical role in the global carbon cycle and provides food and energy for aquatic organisms. Recently, hydrochar, as a solid carbonaceous substance derived from hydrothermal carbonization, has been increasingly used as a soil amendment. Upon entering the soil, dissolved components (DHCs) were released from hydrochar as exogenous DOM, finally entering the aquatic ecosystems by runoff, which participates in environmental geochemical processes. However, relevant reports revealing the response of the aquatic ecosystem to the input of DHCs remain insufficiently elucidated. For the first time, the fundamental features of DHCs and their influence on water quality and aquatic biological function were investigated in this study. DHCs at 260 °C (DHC260) had lower yields, a greater [C/N], worse biodegradability, and larger humic acid relative amounts than did DHCs at 180 °C (DHC180). The DHC structural alterations in periphyton-incubated aquatic ecosystems suggested that protein substances were more easily degraded or assimilated by periphyton, especially for DHC180, with rates of decrease of 34.5-63.5%. The increased chemical oxygen demand (COD) degradation in the DHC260 treatments was most likely due to humic acid substances with higher COD equivalents. Furthermore, DHC260 caused phosphorus to accumulate in periphyton, reducing aquatic phosphorus concentration. Notably, the abundances of Flavobacteria and Cyanobacteria associated with water blooms increased 12.7-25.5- and 1.3-8.3-fold, respectively; consequently, the promotional impact of DHCs on algal blooms should be considered. This result extends the nonnegligible role of DHCs in aquatic ecosystems and underlines the need to regulate the hydrochar application process.

Ecology and extent of freshwater browning - What we know and what should be studied next in the context of global change

Water browning or brownification refers to increasing water color, often related to increasing dissolved organic matter (DOM) and carbon (DOC) content in freshwaters. Browning has been recognized as a significant physicochemical phenomenon altering boreal lakes, but our understanding of its ecological consequences in different freshwater habitats and regions is limited. Here, we review the consequences of browning on different freshwater habitats, food webs and aquatic-terrestrial habitat coupling. We examine global trends of browning and DOM/DOC, and the use of remote sensing as a tool to investigate browning from local to global scales. Studies have focused on lakes and rivers while seldom addressing effects at the catchment scale. Other freshwater habitats such as small and temporary waterbodies have been overlooked, making the study of the entire network of the catchment incomplete. While past research investigated the response of primary producers, aquatic invertebrates and fishes, the effects of browning on macrophytes, invasive species, and food webs have been understudied. Research has focused on freshwater habitats without considering the fluxes between aquatic and terrestrial habitats. We highlight the importance of understanding how the changes in one habitat may cascade to another. Browning is a broader phenomenon than the heretofore concentration on the boreal region. Overall, we propose that future studies improve the ecological understanding of browning through the following research actions: 1) increasing our knowledge of ecological processes of browning in other wetland types than lakes and rivers, 2) assessing the impact of browning on aquatic food webs at multiple scales, 3) examining the effects of browning on aquatic-terrestrial habitat coupling, 4) expanding our knowledge of browning from the local to global scale, and 5) using remote sensing to examine browning and its ecological consequences.

Whole-genome sequencing illuminates multifaceted targets of selection to humic substances in Eurasian perch

Extreme environments are inhospitable to the majority of species, but some organisms are able to survive in such hostile conditions due to evolutionary adaptations. For example, modern bony fishes have colonized various aquatic environments, including perpetually dark, hypoxic, hypersaline and toxic habitats. Eurasian perch (Perca fluviatilis) is among the few fish species of northern latitudes that is able to live in very acidic humic lakes. Such lakes represent almost "nocturnal" environments; they contain high levels of dissolved organic matter, which in addition to creating a challenging visual environment, also affects a large number of other habitat parameters and biotic interactions. To reveal the genomic targets of humic-associated selection, we performed whole-genome sequencing of perch originating from 16 humic and 16 clear-water lakes in northern Europe. We identified over 800,000 SNPs, of which >10,000 were identified as potential candidates under selection (associated with >3,000 genes) using multiple outlier approaches. Our findings suggest that adaptation to the humic environment may involve hundreds of regions scattered across the genome. Putative signals of adaptation were detected in genes and gene families with diverse functions, including organism development and ion transportation. The observed excess of variants under selection in regulatory regions highlights the importance of adaptive evolution via regulatory elements, rather than via protein sequence modification. Our study demonstrates the power of whole-genome analysis to illuminate multifaceted nature of humic adaptation and provides the foundation for further investigation of causal mutations underlying phenotypic traits of ecological and evolutionary importance.

Investigating the impact of in situ soil organic matter degradation through porewater spectroscopic analyses on marsh edge erosion

Marsh edge erosion results in soil organic matter (SOM) loss from coastal wetlands and is differentially affected by wind waves, soil properties, and vegetation cover. The degradation of SOM may make the marsh edge susceptible to erosion. The objective of this study was to investigate the effect of in situ biogeochemical degradations of SOM on marsh edge erosion using porewater spectroscopic analyses. Edge erosion was monitored at 12 transects in one of the highly eroding coastal basins of Louisiana. A total of 36 cores were collected at different distances from the edge of the marsh. Porewater was extracted and analyzed for dissolved organic carbon (DOC) and spectroscopic indicators. The north and west side had greater erosion rates (102.38 ± 5.2 cm yr^-1) than east and south side (78.47 ± 3.3 cm yr^-1). However, the north and east side had greater DOC and refractory carbon but less microbial activity indicating SOM degradation alone did not correlate to edge erosion. The intersecting trend between erosion rate and SOM degradation among four sides of the island indicates the complex nature of edge erosion drivers. The estuarine bottom indicators suggest the eroded SOM is not reburied but rather degraded and emitted back into the atmosphere as CO₂, potentially contributing to global change. The coastlines projected to experience high sea-level rise in the coming century are vulnerable to losing a large amount of stored carbon in the absence of efficient mitigation measures.