Abstract
The antibiotics sulfamethoxazole (SMZ) and enrofloxacin (ENF) are commonly used in aquaculture in China, but their effects on the primary productivity of phytoplankton are unclear. On the basis of the fishery drug use standards (SMZ, 100 mg kg−1 d−1; ENF, 15 mg kg−1 d−1), these antibiotics were put into culture ponds to observe their effects on the phytoplankton community and primary productivity. The results showed that the changes in phytoplankton species at SMZ and ENF sites were different. At the ENF sites, Bacillariophyta species increased from 7 to 9, euglenophyta from 8 to 12 and cyanophyta from 11 to 9. Chlorophyta species at the SMZ sites increased from 10 to 15 and euglenophyta from 7 to 4. SMZ and ENF significantly promoted the number of cyanophyta (p < 0.05). The promoting effect of SMZ was more obvious than that of ENF. SMZ was more effective than ENF in promoting cyanophyta. The maximum number of cyanophyta at SMZ sites was 52.39 million L−1, and the concentration of SMZ was positively correlated with the number of cyanophyta. The maximum number of cyanophyta at ENF sites was 33.13 million L−1, and the promoting effect of low concentrations was more significant than that of high concentrations. Both SMZ and ENF promoted increased phytoplankton biomass, consistent with the residual time of the antibiotics in the aquaculture environment. The greatest biomass at the SMZ sites was 129.31 g m−³, and that at the ENF sites was 117.85 g m−³. The changes in the α diversity index showed that both SMZ and ENF led to a decrease in phytoplankton biodiversity, and that SMZ was more harmful to it. There were significant differences in the Shannon–Wiener, Pielou and Simpson indexes of the SMZ sites within groups (p < 0.05). The β diversity index showed that both antibiotics could change the phytoplankton habitat, but the effect of ENF on the habitat was recoverable, while that of SMZ prevented its restoration. These data will be valuable in protecting the ecological environment of fisheries and ensuring the safety and stability of fishery aquatic ecosystems.
Highlights
In recent years, antibiotics have been widely used in the prevention and treatment of a variety of bacterial diseases (Bialk-Bielinska et al, 2011; Johnson et al, 2015)
We studied the effects of SMZ and ENF on primary productivity of phytoplankton in the culture environment, to obtain basic experimental data and a theoretical basis to promote the sustainable development of fisheries and to protect the ecological environment
We found that the values of the Shannon–Wiener, Margalef richness and Pielou indexes at the SMZ sites were lower than those at the ENF sites, which indicated that SMZ was more harmful to phytoplankton biodiversity
Summary
Antibiotics have been widely used in the prevention and treatment of a variety of bacterial diseases (Bialk-Bielinska et al, 2011; Johnson et al, 2015). The release of residual antibiotics into the environment may affect the phytoplankton community and endanger the safety and stability of the ecosystem. Changes in the number of algae may cause changes in the dominant species and biomass of the community, affect the stability and complexity of the community structure, lead to habitat changes and even harm the structure and function of the whole ecosystem (Rakowski and Cardinale, 2016). Algae are an important indicator in an environmental quality assessment of an aquatic ecosystem, and so helpful in a comprehensive and effective evaluation of the comprehensive effects of pollutants on phytoplankton and the whole aquatic ecosystem (Li et al, 2008; Khalil et al, 2021). The diversity and complexity of aquatic ecosystems can be effectively understood by observing the species composition and quantitative changes in algae
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