Dynamics of Cyanobacteria and Related Environmental Drivers in Freshwater Bodies Affected by Mitten Crab Culturing: A Study of Lake Guchenghu, China

Hongmin Li,Huihui Chen,Xiaohong Gu,Huiping Ding,Zhigang Mao,Qingfei Zeng

doi:10.3390/w11122468

Abstract

Mitten crab aquaculture is prevalent in China, however, knowledge about the threat of cyanobacteria in mitten crab aquaculture-impacted water bodies is limited. Here, seasonal variations of cyanobacteria and their relationships with environmental factors were investigated for Lake Guchenghu area. Results suggested the changes of cyanobacteria community in crab ponds distinguished from the adjacent lake. In the lake, cyanobacterial biomass (3.86 mg/L, 34.6% of the total phytoplankton) was the highest in autumn with the dominance of Oscillatoria, Aphanocapsa and Pesudanabaena. By contrast, in crab ponds, cyanobacteria (46.80 mg/L, 97.2% of the total phytoplankton biomass) were the most abundant in summer when Pesudanabaena and Raphidiopsis were the dominant species. Of particular note was that obviously higher abundance of filamentous and potentially harmful species (e.g., Raphidiopsis raciborskii and Dolichospermum circinale) were observed in ponds compared to the lake. Specifically, water depth (WD), permanganate index (CODMn), total phosphorus (TP), N:P ratio, and NO 2 −-N were the key environmental variables affected cyanobacteria composition. For crab ponds, N:P ratio, water temperature (WT) and TP were the potential environmental drivers of cyanobacteria development. This study highlighted the fact that mitten crab culture had non-negligible influences on the cyanobacteria community and additional attention should be paid to the cyanobacteria dynamics in mitten crab culture-impacted water bodies, especially for those potentially harmful species.

Highlights

Cyanobacteria are ubiquitous in diverse aquatic environments throughout the world, including lakes, reservoirs, ponds, etc
Whilst some studies suggested that cyanobacteria can dominate in both low and high phosphorus conditions [36], our study found that the total phosphorus was the major positive driving factor in governing the cyanobacteria abundance, and nitrogen was not a limiting factor for cyanobacteria proliferation
The present study demonstrated that the activities of mitten crab culture played a certain role in the change of cyanobacterial community structure

Summary

Introduction

Cyanobacteria are ubiquitous in diverse aquatic environments throughout the world, including lakes, reservoirs, ponds, etc. The impact of aquaculture on water quality and the expansion of harmful cyanobacteria is a major environmental issue. Given the increase in intensive aquaculture, many environmental challenges emerged, among which environmental degradation associated with cyanobacterial blooms appeared to be the most alarming [4]. The noxious cyanobacterial blooms would cause various problems associated. Water 2019, 11, 2468 with unpleasant tastes, odors and toxic metabolite production which could threaten aquatic products and human health [2,4,5,6,7]. Over the past few years, mitten crab culture has become one of the most economically important freshwater aquacultures in China, with current yield of this species increasing dramatically

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