Diatoms from rice paddy fields

Diatoms, like other bioindicators used in river monitoring, could be useful in the assessment of agricultural environments, enhancing an integrated approach in the management of these sites, which are often subject to difficult cultural dynamics. In this context, they are useful tools for the analyses of different sectoral analyses. For this purpose, a study was conducted within two rice-growing environments and the associated supply canal, in the province of Pavia, Lombardy. Diatom colonization was assessed through thirty tiles within each sampling site, used as artificial substrates.

Sampling was carried out during summer 2023: each tile was qualitatively and quantitatively assessed, with biomass, specific and functional community analysis. Environmental characteristics showed high site distinctiveness: high daytime temperature, higher light radiation and elevated anthropogenic impact due to the chemical treatments conducted during the period. Diatom communities responded to these environmental and localized characteristics, as well as to the external influences, changing over the period. A total of 72 species were identified at the three sites. Dominant genera included Nitzschia, Navicula and Planothidium in the rice fields, as well as Amphora and Caloneis in the supply canal, with a greater dominance of motile and low-profile guilds and a near absence of high profile and planktonic ones. Among others, a new species never found in Italy and recently described, Planothidium incuariatum, was identified, the identification of which will be crucial in defining its ecological and environmental requirements for future analyses. These results confirm the validity of diatoms for the assessment of rice-growing environments. Indeed, the differences in specific composition are consistent with the ecological characteristics present at the sites. Moreover, in recent years, the agricultural environment has been the subject of several Italian and European normative, on the protection of human health and environmental quality. In this view, diatoms and periphyton in general, have often been considered useful in decreasing the concentration of dissolved heavy metals in water, with notable benefits for human health and the quality of the final crop product.