Abstract
An outbreak of harmful algal blooms (HABs) often leads to the death of fish and other marine organisms and causes serious losses to human economic activities. Modified clay (MC) technology is an effective way to control HABs. Although the material and preparation process are based on the premise of green and safety, the potential eco-environmental impacts of MC on non-target organisms should still have to receive attention before field applications can occur. Therefore, the effects of one commonly used modified clay, polyaluminum chloride-modified clay (PAC-MC), on the survival, growth, and oxidative stress of the marine medaka (Oryzias melastigma) were studied. The toxicity test results showed that the 96-h median lethal concentration (96-h LC50) of PAC-MC for newly hatched medaka larvae was 5.204 g/L, which was much higher than the concentration used on site (4–10 t/km2). Within the concentration range of PAC-MC used in this experiment (≤2 g/L), the morphology, heart rate, growth, and aluminum content of larvae did not change with the increase in the modified clay concentration. Low concentrations of PAC-MC (≤0.5 g/L) did not significantly affect catalase (CAT) activity, superoxide dismutase (SOD) activity, peroxidase (POD) activity, and the content of malondialdehyde (MDA), but higher concentrations of PAC-MC (such as 2 g/L) caused oxidative damage to the larvae and increased the antioxidant enzyme activity of the larvae. The present study revealed that under an effective dosage for treating harmful algal blooms on site, PAC-MC had no adverse effects on the survival, growth, oxidative stress, and aluminum content of the newly hatched marine medaka, which provides a scientific basis for the field application of modified clay.
Highlights
Harmful algal blooms (HABs) have gradually evolved from a regional environmental problem to a global ecological disaster
The 7 g/L group died at 3 h, and all died at 48 h
This article studied the effect of PAC-Modified clay (MC) on the model organism for marine ecotoxicology —the marine medaka
Summary
Harmful algal blooms (HABs) have gradually evolved from a regional environmental problem to a global ecological disaster. HABs lead to a large number of deaths of fish and other marine aquaculture organisms, resulting in more and more serious economic losses. Due to low efficiency, high cost, and uncontrollable ecological effects, the practical application of the above methods is limited. Natural clay has the advantages of pollution-free and lowcost treatment, but low flocculation efficiency is the biggest bottleneck in its application process. Zhiming Yu and his team proposed clay surface modification technologies and methods [15,16,17,18] and used modifiers combined with natural clays to overcome the problems related to the need for large amounts of material and low removal efficiency and reduce dosing requirement to 4–10 t/km2 [19]. Of prime consideration is the impact of clay addition on non-target organisms in the water column and the benthic environment
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