Benthic sediment resuspension influences boundary layer nutrient dynamics, the ability of substrates to support rooted vegetation, and other factors impacting water quality health (e.g., suspended sediment) and aquatic ecosystems. In response, a benthic boundary layer microcosm system examined potential sediment erosion impacts in 2 independent intact sediment core case studies from diverse geographic locations (Michigan and Texas, USA). The first study investigated the effects of lake sediment erosion on wildrice bedforms, potential impacts to root stability, seed bank displacement, and suspended solids. Results indicate highly erodible sediments exhibit reduced wildrice abundance, underscoring the role of benthic sediment dynamics in maintaining ecosystem resilience. The second study evaluated increases in suspended solids and turbidity in reservoirs at risk from harmful algal blooms. Reservoirs with elevated sediment total phosphorus concentrations exhibited higher levels of total suspended solids during erosion experiments, highlighting potential erosion-induced internal benthic nutrient loading. Collectively, these studies illustrate how erosion microcosms inform the complex interactions between benthic sediment processes and factors influencing aquatic health, allowing natural resource managers to target sediment stabilization activities (e.g., no wake zones) or alter reservoir operations. Future studies should strengthen causal relationships between benthic boundary erosion, watershed characteristics, and water quality outcomes.
Freshwater rock pools (FRPs) are temporary aquatic environments that provide refuge for biodiversity in regions with low precipitation. The macroinvertebrate communities of FRPs in the Brazilian semi-arid region constitute an important link between aquatic and terrestrial ecosystems, given their dependency on both to complete their life cycles. The knowledge about FRPs and their resident biota remains scarce, compromising effective conservation actions. In this study, we investigated the influence of dispersal mode and local environmental conditions on the structure of macroinvertebrate communities. We sampled 16 FRPs on a unique, continuous inselberg in the Brazilian semi-arid region during the wet and dry seasons of 2013. In each rock pool, we collected macroinvertebrates and measured local environmental variables related to water characteristics and pool morphology. We observe that seasonal variation influences the predominant dispersal mode of macroinvertebrate communities, while local environmental conditions shape their composition. Active dispersers were predominant in both wet and dry seasons. However, during the dry season, the abundance of passive dispersers increased sevenfold relative to that of active dispersers. Community composition was significantly influenced by dissolved oxygen, pH, water temperature, and electrical conductivity. These findings highlight the importance of FRPs as habitat refuges for aquatic biota from semiarid regions.
Riverine aquatic systems play a key role in both regional and global carbon cycles. However, the extent to which nutrient regulation and changes in dissolved organic matter (DOM) chemistry control the proportion dissolved organic carbon (DOC) biodegraded by microorganisms (%BDOC) in rivers of the Loess Plateau is still not well quantified. Based on a 56-day indoor incubation experiment, %BDOC, temperature sensitivity (Q10), optical properties of DOM, and nutrients and their stoichiometric ratios were investigated in the middle reaches of the Yellow River. The results showed that BDOC (mean [SD]) at 35 degrees C (54% [21%]) was significantly higher than that at 25 degrees C (38% [22%]) with an average (mean [SD]) Q10 value of 1.7 (0.6). Consistent decreases in absorbance at 254 nm (a254) and 350 nm (a350), supported by a concomitant reduction in humic-like fluorescence, indicated decomposition of aromatic compounds and lignin fractions. By contrast, the increase in the absorbance ratios (E2:E3, A250/A365) and the decrease in the E4:46 ratios (A465/A665) showed that macromolecular DOM had not been completely degraded and enriched after 56 days of incubation. In addition, %BDOC was negatively correlated with DOC, TN:TP, and DOC:TP in the study, further suggesting that phosphorus availability was a major limiting factor for aquatic microbial respiration in rivers of the Loess Plateau. These findings advance the mechanistic understanding of DOC biodegradation, informing predictions of carbon dynamics and their implications for the global carbon cycle under future climate scenarios.
