Composition and Density of Benthic Diatoms in Sediments with Different Compost Mixtures on Cultivation of Sea Cucumbers (Holothuria scabra) Using Floating Net Cages

Diatoms, a group of phytoplankton known as Bacillariophyceae, serve as food for benthic organisms such as sea cucumbers (Holothuria scabra). Sea cucumber raising has the potential to alleviate wild fishing pressure, satisfy a sizable market demand, and improve the water quality in aquaculture settings. This study aimed to analyze the composition and density of benthic diatoms as a natural feed for sea cucumbers deposited in sediments. The research was carried out in the waters of the Inner Ambon Bay, Maluku, Indonesia.  The rearing of sea cucumbers involves using floating net cages with the off-bottom method. This method utilizes suspended containers and sediment, with the addition of seagrass leaves, sago waste, and chicken manure to stimulate the growth of benthic diatoms, which serve as a natural feed for sea cucumbers. This study used three treatments: i) treatment A (seagrass leaves + chicken manure), ii) treatment B (seagrass leaves + sago waste), and iii) treatment C (seagrass leaves + chicken manure + sago waste). Data analysis was descriptively  carried out and displayed in the form of tables and graphs. The research results showed that two orders, 14 families, 25 genera and 66 species of benthic diatoms were found in the sediments of sea cucumber cultivation floating net cages. Density of benthic diatom species, composition, and quantity were influenced by varying meal compositions. Treatments involving seagrass leaves, sago waste, and chicken manure resulted in increased diatom densities and genera composition. The benthic diatoms found were dominated by the order Pennales, in particular the different species belonging to the genera of Navicula. The results of this study found that treatment with a more diverse compost composition was able to support the high number and density of benthic diatoms since it was suspected that they had a higher nutrient content. The results of this study provide information about the effectiveness of using sago waste + chicken manure + seagrass leaves as an alternative compost to stimulate the growth of benthic diatoms as a natural feed in sea cucumber cultivation.