Surface sediment samples were collected from four areas (the Jingdezhen Industrialized Area (JDZ), Upstream (UP), the Dexing Mining Area (DX), and Downstream (DM)) to investigate the concentration and chemical composition of heavy metals. The sediments were analysed for Cu, Zn, Pb, Cd, Cr, As, and Ni using a sequential extraction scheme according to the improved BCR (European Community Bureau of Reference) method. The obtained results show that the maximum values of Cu (793.52 μg·g⁻¹), Zn (72.09 μg·g⁻¹), Pb (222.19 μg·g⁻¹), and Cd (1.60 μg·g⁻¹) were collected from the DX sampling area, while the JDZ area had the highest concentrations of Cr (97.09 μg·g⁻¹), As (318.05 μg·g⁻¹), and Ni (66.35 μg·g⁻¹). The majority of metal values far exceeded their corresponding background values. The risk analysis of geo-accumulation index (I_geo) indicated that the heavy metals Cu and As were the main pollution factors and each element of the pollution degree followed the order of: Cu > As > Pb > Cd > Cr > Zn. Metal partitioning characteristics were also considered and more than 80% of metals show potential bioavailability and toxic effects.

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under 40% dilution, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate the importance of nutrient limitation effects on microcystin and anatoxin production. To properly combat cyanotoxin and cyanobacterial biomass production in WLE, both N and P reduction efforts should be implemented in its watershed.

Primary productivity plays a key role in aquatic lake ecosystems. This study addresses the characteristics of primary phytoplankton productivity and its relationship with environmental factors in a large, shallow, and eutrophic lake (Lake Taihu, China). Surface water samples were collected in wet and dry seasons from eight lake areas to investigate physicochemical factors and primary productivity. The results show obvious seasonal differences in phytoplankton primary productivity and physicochemical factors in Lake Taihu. The primary productivity in the wet season is about five times larger than that in the dry season, and the spatial distribution of primary productivity is obviously inhomogeneous in the wet season, while in the dry season, there are no significant differences in different lake areas. Most of the lake areas are in the middle eutrophic state regardless of the season; the northwest region has the heaviest degree of eutrophication, while the southeast region has the lightest degree of eutrophication. Pearson correlation indicated that nutrients are the main factors affecting primary productivity in the wet season, while temperature is the most important factor affecting primary productivity in the dry season. Multiple stepwise regression suggested that chlorophyll-a (Chl-a), temperature (T), and water transparency (SD) can be used to estimate the phytoplankton primary productivity in Lake Taihu in different seasons, and the main influencing factors for primary productivity are Chl-a, nutrients, and SD/total suspended solids (TSS) in the wet season and T, Chl-a, and SD/TSS in the dry season.

Sediment resuspension induces endogenous nutrient release in shallow lakes, which has been demonstrated to be associated with eutrophication. In addition to natural wind-driven resuspension, navigable shallow lakes (such as Lake Taihu, China) also experience resuspension from human activities, such as ship waves. Both processes determine the intensity, frequency, and duration of sediment resuspension, and may consequently affect the pattern of cyanobacteria blooms in the lake. In this study, acoustic Doppler Velocimeter (ADV), Optical Backscatter Sensor (OBS), and temperature wave tide gauge (instrument model :RBR duo TD|wave) were placed in an observation platform in the lake to obtain high-frequency flow velocities, suspended sediment concentration (SSC), and wave parameters before, during, and after a cargo ship passed by. We found that the ship wave disturbance intensity is greatly influenced by the draft depth. The movement generated by ship disturbance is primarily horizontal rather than vertical. Compared with the wind-induced wave, the disturbance caused by the ship waves has a high intensity, short duration, and narrow range of influence. The maximum total shear stress under ship disturbance can reach 9~90 times the critical shear stress under a natural state. Therefore, the effect of ship waves on sediment resuspension near the channel of Lake Taihu is much greater than that of wind-induced waves. These findings represent an important step towards understanding the quantitative relationship between ship wave disturbance and sediment resuspension, and lay the foundation for future research in order to understand and control the eutrophication of shallow lakes.

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin and a Planktothrix spp. bloom in Sandusky Bay. Recently, USA and Canada agreed to a 40%

To comprehend the distribution characteristics of the nutrients and the variations in the soil fertility, a total of 23 samples were collected from Nanjishan wetland reserve in the dry season, wet season, and water-recession season. The study area was divided into four areas (A1, A2, A3, and A4) based on the local hydrological conditions, geographical locations, and nutrient load characteristics. The findings showed that the highest concentration of nutrients appeared in A1, followed by A2 due to anthropogenic activities and the sewage discharge along Ganjiang River. Except for the total amounts of nutrients (the total nitrogen (TN), total phosphorus (TP), and total potassium (TK)), the nutrient concentrations dropped in the wet season and recovered in the water-recession season. A close association between microorganisms and the soil nutrients was observed. The Integrated Fertility Index (IFI) indicated a significant spatio-temporal variability in the soil fertility. The soil quality was higher in the dry season. The values of the IFI displayed a decreasing trend during the growing season (wet season). The single factor standard index method (SFSI) suggested that the whole area had a potential risk of eutrophication, to which the TN could be considered a main contributor.