WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2025 47 Results Diatoms on the Artificial Grass. A variety of diatoms was found growing on the artificial grass blades. The most frequently observed species were of the genera Navicula, Nitzschia, Pinnularia, Melosira and Tabellaria (Figure 9). Counting by approximation the quantity growing on the artificial grass, by averaging two counts on a Neubauer plate, yielded an average of 12x104 cells/mL. When multiplied by 5 mL of the dilution this would give an estimate of 625,000 cells of microalgae for each blade observed. There are about 320 blades in 1 patch of the artificial grass that was provided to each replicate of 10 conch, therefore, this yielded a total cell count of about 200 million cells available for the conch. In standard conch aquaculture procedures, juvenile conch at the size used in this study are fed flocculated Chaetoceros gracilis (Davis and Cassar 2020). The cell count is about 1.53 × 109 cells/ mL. If the 28-day old conch are provided with 74 mL of flocculated C. gracilis, this would be equivalent to about 1.13 × 1011 cells. Growth Rates. A key indicator of the success of our system was the growth rate of the conch after their introduction to the tanks with artificial grass. Table 1 shows the average growth rates of juveniles fed the two diets in the two different systems. The growth of the conch on the artificial grass in outside systems (ART, n = 30) and those that were inside and fed C. gracilis (CONT, n=30) were compared using a two-way ANOVA to assess the effects of treatment group (ART vs CONT) and time (T1, T2, T3). This approach allowed for the evaluation of both individual and interactive impacts of treatment group and growth intervals. At T1, ART vs CONT showed no significant differences (p=0.346). At T2 (14 days after the first measurement), the conch in the ART group exhibited a significant growth increase compared CONT (p < 0.01). At T3 (12 days after the second measurement) the ART group again exhibited significantly greater growth (p < 0.01). A visual representation of this growth difference can also be seen in Figure 10. Discussion The utilization of artificial grass as a substrate for microalgae cultivation, especially diatom growth, presents a novel and interesting approach to enhancing the dietary conditions for juvenile queen conch (Aliger gigas). Our findings indicate that artificial grass supported a diverse and nutritious diet for the conch. This effective diatom cultivation led to significant improvements in the growth rates of juvenile conch when compared to traditional substrate and food. Notably, the types of diatoms grown on artificial grass were among those highly beneficial to the diet of juvenile conch, such as Navicula sp., Nitzschia sp., and others. This diversity is desirable for replicating algal communities that conch encounter in their natural habitat. The growth rates observed in the ART group (artificial grass treatment) were significantly higher than those in the CONT (control: regular feeding protocol) group. This shows the potential of natural diatoms to grow on artificial grass, possibly improving the nutritional quality and availability of microalgae in an aquaculture setting. This study highlights that using specific substrates or enrichment in an aquaculture setting can influence the development of cultured species, in our case: juvenile queen conch. The adoption of artificial grass as a substrate possibly more closely replicates the complexity of natural habitats and might also present a sustainable and cost-effective method to address nutritional challenges. Interestingly, despite a quantitative reduction in algae availability (based on cell count) within the ART group compared to normal Chaetoceros gracilis feeding (CONT), a significant enhancement in growth rates was observed over 26 days. This suggests that environmental complexity, or enrichment, plays a crucial role in nutritional dynamics. This might be driven or strengthened by behavioral responses of the queen conch to the presentation of their food, indicating an additional layer of environmental enrichment. The observations made in the current study highlight the intricate interplay between physical environment and biological responses, suggesting that there are benefits of substrate use in aquaculture settings that extend beyond mere nutritional provision. Other substrates could even further encompass broader ecological and behavioral dimensions. Our study is not without limitations, though. The specific environmental conditions within our experimental setup, such as water temperature and light exposure, may have influenced the outcomes. Furthermore, while we observed an increase in growth rates, the study did not fully explore the survival rates and long-term health impacts on the juvenile conch, indicating another area for future research. Our conch experienced a mortality rate of 13 percent (n=4) in the ART group (with artificial grass) versus 3 percent (n=1) in the CONT group over the course of the experiment. It is also important to consider the potential issues associated with using artificial grass, especially the breakdown of plastic and possible toxicity. This aspect was only briefly explored in literature during our study, but it’s crucial for long-term experiments and health implications to evaluate the safety and environmental impact of plastics in aquaculture. It is a necessary step to ensure the safety and sustainability of these practices. Future studies should thus focus on the abovementioned, but also on optimizing the artificial grass substrate for broader applications within aquaculture, firstly investigating its effects over a longer period of time, in larger groups, and possibly also in other species. The latter becomes interesting when thinking about clam, oyster or shrimp culture, which on a larger scale might benefit from increased growth rates when cultured. TABLE 1. Juvenile conch growth rates in the ART (artificial grass in tanks) group versus CONT (control group just fed C. gracilis). (CONTINUED ON PAGE 74)
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