Monitoring and research of microcystins and environmental factors in a typical artificial freshwater aquaculture pond

Abstract

Freshwater aquaculture ponds are important artificially regulated aquatic ecosystems which provide a large number of freshwater fish products in China. The cyanobacteria bloom and microcystin (MC) pollution caused by anthropogenic eutrophication have attracted much attention due to their toxic effects. To provide an insight into the cyanobacterial problem in the ponds, the environmental parameters and MCs of a typical artificial pond in the Yangtze River Delta region of China were monitored and studied from May to December 2015. During the monitoring period, the ponds were in serious eutrophication with total phosphorus (TP) concentrations between 0.95 and 1.80 μg/L, and total nitrogen (TN) concentrations between 1.1 and 4.86 μg/L. High feed coefficient and high fish stock were the main reasons for the eutrophication. The results showed that the water temperature was the key factor that affected the cyanobacteria blooming in the pond. The chlorophyll a concentration was significantly positively correlated with the cyanobacteria density during the blooming season. MC-LR and MC-RR existed simultaneously and showed a significant positive correlation. The peak concentrations of dissolved MC-LR and MC-RR in the pond water were 40.6 and 4.7 μg/L, respectively, which is considered highly toxic. Free MC-LR and MC-RR were also found in the aquaculture products. MC-LR concentrations in the bighead carp (Aristichthys nobilis) liver and shrimp (Macrobrachium nipponense) muscle were up to 2.64 and 4.17 μg/kg, respectively. MC-RR concentration was up to 1.89 μg/kg in the black carp (Mylopharyngodon piceus) liver. The results implied the potential health risks for citizens and pets caused by current artificial freshwater aquaculture pond systems.

Principal hydrology and water quality factors driving the development of plankton communities in a pilot city of China

“…The water quality factors that had strong driving effects towards the development of both phytoplankton and zooplankton communities was pH, which is consistent with the conclusions obtained in plankton‐based studies by Reynolds (2006) and Pinilla (2006). Phytoplankton communities are affected by WT to a greater extent, as phytoplankton growth and reproduction requires higher WT (Alam et al, 2001; Descy et al, 2016; Hu et al, 2018), whereas zooplankton communities are affected by Cond to a greater extent, which is consistent with the conclusions of the study on zooplankton by Walker and Pan (2006). The main chemical factors of water quality driving the development of phytoplankton communities were BOD, as appropriate levels of BOD can promote rapid phytoplankton reproduction (Hou, Song, Liu, Xiao, & Liu, 2004; Salomoni, Rocha, Callegaro, & Lobo, 2006; Zhu, Wang, Chen, Shen, & Deng, 2018).…”

“…In terms of phytoplankton growth habits, their reproduction depends on an appropriate WT (Sinden & Sinang, 2016). WT is the most important physical driving factor for controlling algae resuscitation, reproduction and outbreaks (Figueredo & Giani, 2009; Hu et al, 2018).…”

Gastrointestinal toxicity induced by microcystins

“…MCs pose a threat to human health in many ways, such as oral, dermal and inhalation pathways, and exposure may occur during recreation depending on the types of activities undertaken in the water[ 4 , 5 ]. Freshwater aquaculture ponds are important artificially regulated aquatic ecosystems that provide a large number of freshwater fish products in China[ 6 ]. Moreover, China’s freshwater aquaculture area and production stands first in the world[ 7 ].…”

“…Moreover, China’s freshwater aquaculture area and production stands first in the world[ 7 ]. Studies have shown that MCs can accumulate in a variety of aquatic organisms, such as zooplankton, bivalves, crustaceans, fish, and aquatic vertebrates[ 6 ]. It may exert a potential toxic hazard to humans after the consumption of MC-contaminated aquatic products.…”

“…Studies have indicated that MCs accumulate mainly in the liver, and can be transported to the kidneys, muscle, brain, and intestines through blood circulation[ 6 ]. Furthermore, MCs have been confirmed to be transported into cells via organic anion transporting polypeptides (OATPs), which exist in almost every organ[ 8 ], while some OATPs are preferentially or even selectively expressed in specific tissues[ 9 ].…”