Effects of guanotrophication and warming on the abundance of green algae, cyanobacteria and microcystins in Lake Lesser Prespa, Greece

Phycoremediation of heavy metals and production of biofuel from generated algal biomass: a review

Due to human activity and natural processes, heavy metal contamination frequently affects the earth's water resources. The pollution can be categorized as resistant and persistent since it poses a significant risk to terrestrial and marine biological systems and human health. Because of this, several appeals and demands have been made worldwide to try and clean up these contaminants. Through bioremediation, algal cells are frequently employed to adsorb and eliminate heavy metals from the environment. Bioremediation is seen as a desirable strategy with few adverse effects and low cost. Activities and procedures for bioremediation involving algal cells depend on various environmental factors, including salinity, pH, temperature, the concentration of heavy metals, the amount of alga biomass, and food availability. Additionally, the effectiveness of removing heavy metals from the environment by assessing how environmental circumstances affect algal activities. The main issues discussed are (1) heavy metal pollution of water bodies, the role of algal cells in heavy metal removal, the methods by which algae cells take up and store heavy metals, and the process of turning the algae biomass produced into biofuel. (2) To overcome the environmental factors and improve heavy metals bioremediation, many strategies are applied, such as immobilizing the cells, consortium culture, and using dry mass rather than living cells. (3) The processes for converting produced algal biomass into biofuels like biodiesel and biomethanol. The present study discusses the life cycle assessment and the limitations of biofuel products from algae biomass.

Environmental microcystin exposure triggers the poor prognosis of prostate cancer: Evidence from case-control, animal, and in vitro studies

Microcystin-leucine-arginine (MC-LR) is positively linked with multiple cancers in humans. However, the association between MC-LR and the risk and prognosis of prostate cancer has not been conducted in epidemiological studies. No reported studies have linked MC-LR exposure to the poor prognosis of prostate cancer by conducting experimental studies. The content of MC-LR was detected in most of the aquatic food in wet markets and supermarkets in Nanjing and posed a health risk for consumers. MC-LR levels in both prostate cancer tissues and serum were significantly higher than controls. The adjusted odds ratio (OR) for prostate cancer risk by serum MC-LR was 1.75 (95%CI: 1.21-2.52) in the whole subjects, and a positive correlation between MC-LR and advanced tumor stage was observed. Survival curve analysis indicated patients with higher MC-LR levels in tissues exhibited poorer overall survival. Human, animal, and cell studies confirmed that MC-LR exposure increases the expression of estrogen receptor-α (ERα) and promotes epithelial-mesenchymal transition (EMT) in prostate cancer. Moreover, MC-LR-induced decreased E-cadherin levels, increased vimentin levels, and increased migratory and invasive capacities of prostate cancer cells were markedly suppressed upon ERα knockdown. MC-LR-induced xenograft tumor growth and lung metastasis in BALB/c nude mice can be effectively alleviated with ERα knockdown. Our data demonstrated that MC-LR upregulated vimentin and downregulated E-cadherin through activating ERα, promoting migration and invasion of prostate cancer cells. Our findings highlight the role of MC-LR in prostate cancer, providing new perspectives to understand MC-LR-induced prostatic toxicity.

The role of organic nutrients in structuring freshwater phytoplankton communities in a rapidly changing world

Carbon, nitrogen, and phosphorus are critical macroelements in freshwater systems. Historically, researchers and managers have focused on inorganic forms, based on the premise that the organic pool was not available for direct uptake by phytoplankton. We now know that phytoplankton can tap the organic nutrient pool through a number of mechanisms including direct uptake, enzymatic hydrolysis, mixotrophy, and through symbiotic relationships with microbial communities. In this review, we explore these mechanisms considering current and projected future anthropogenically-driven changes to freshwater systems. In particular, we focus on how naturally- and anthropogenically- derived organic nutrients can influence phytoplankton community structure. We also synthesize knowledge gaps regarding phytoplankton physiology and the potential challenges of nutrient management in an organically dynamic and anthropogenically modified world. Our review provides a basis for exploring these topics and suggests several avenues for future work on the relation between organic nutrients and eutrophication and their ecological implications in freshwater systems.

Interannual and Spatial Variability of Cyanotoxins in the Prespa Lake Area, Greece

The Prespa Lakes area in Greece—comprised partly of lake Great and lake Lesser Prespa and the Vromolimni pond—has a global importance for biodiversity. Although the waters show regular cyanobacteria blooms, assessments of water quality threats are limited. Samples collected in 2012 revealed scattered and low microcystin (MC) concentrations in Great Prespa (<0.2 μg MC L−1) whereas considerable spatial heterogeneity in both total chlorophyll (2.4–93 µg L−1) and MC concentrations (0.04–52.4 µg MC L−1) was detected in Lesser Prespa. In 2013, there was far less spatial variability of MC concentrations in Lesser Prespa (0.4–1.53 µg L−1), however in 2014, increased concentrations were detected near the lakeshore (25–861 µg MC L−1). In Vromolimni pond the MC concentrations were on average 26.6 (±6.4) µg MC L−1 in 2012, 2.1 (±0.3) µg MC L−1 in 2013 and 12.7 (±12.5) µg MC L−1 in 2014. In 2013, no anatoxins, saxitoxins, nor cylindrospermopsins were detected in Lesser Prespa and Vromolimni waters. Tissue samples from carps, an otter and Dalmatian Pelicans contained 0.4–1.9 µg MC g−1 dry weight. These results indicate that cyanotoxins could be a threat to the ecosystem functions of particularly Lesser Prespa and Vromolimni.

Cyanobacterial Blooms and Zooplankton Structure in Lake Ecosystem under Limited Human Impact

Cyanobacterial blooms are tightly related to increasing trophic conditions of lakes and climate warming. Abiotic and biotic parameters were studied in a shallow lake, in which the island with the largest cormorants colony in north-eastern Poland is situated. We hypothesized that the strongest cyanobacterial blooms will persist near the cormorant’s island and will decrease with an increasing distance from it. Filamentous cyanobacteria (Pseudanabaena, Planktolyngbya, Limnothrix, Planktothrix) were the main phytoplankton components during summer and autumn. Their strongest blooms (up to 66 mg L−1) were recorded near the roosting area. The content of nutrients and chlorophyll a, and the biomass of phytoplankton (primarily cyanobacteria) and zooplankton, decreased gradually with the increasing distance from the island. The changes from hypertrophic to eutrophic conditions were confirmed by a decrease in values of the trophic state index from 72 (site 1) to 58 (site 5). This all suggests that cormorants might have a significant impact on the deterioration of water quality (at distance to 1.6 km) and can contribute to faster water eutrophication. Our results suggest that protection of breeding sites for many waterbirds, such as cormorants, becomes a real threat for the functioning of aquatic ecosystems due to a large load of nutrients.