The Effect of Chronic Microplastic Exposure Towards the Growth, Biochemical Responses and Histological Changes of the Juvenile Sea Cucumber Holothuria Scabra

<title>Abstract</title> Microplastics (MPs), are minuscule plastic particles less than 5 millimeters in size, originating from the degradation of larger plastic debris. They are found in various sources and posing a significant threat to marine ecosystems. Sea cucumber <italic>Holothuria scabra</italic> is a high value commercial species of sea cucumber. They are also crucial in maintaining a clean seabed and recycling nutrients in the ocean ecosystem. This research aimed to investigate the toxicity effects of microplastics on the well-being of juvenile sea cucumber <italic>H. scabra</italic>. Over 60 days treatment period, polymethylmethacrylate MPs were exposed to the juvenile sea cucumber diet at concentrations of 0.6 MPs/g, 1.2 MPs/g and 10 MPs/g to observe changes in their growth, biochemical responses, and histological alteration. The mean weight, weight gain percentage and specific growth rate exhibited significant differences (p &lt; 0.05) with the control group displaying the highest SGR value of 1.22 ± 0.35%. Mortality was observed in treatment 2 and 3, respectively. Notably, a disruption in enzyme assays was also observed (p &lt; 0.05). The findings of growth rates and biochemical responses were further supported by histological observation, uncovering injuries and loss of cellular components in respiratory trees and intestines. This study enhance our understanding of the toxicity mechanism associated with MPs in filter-feeding organisms.