Nematode biomass and morphometric attributes as descriptors during a major Zostera noltii collapse

Benthic nematodes are recognized as suitable organisms to provide valuable information on the potential ecological effects of natural and anthropogenic disturbances in aquatic ecosystems. The biomass and morphometric attributes of nematodes (body length, width, and length/width) collected in the Mira estuary (SW Portugal) were analysed before the collapse and during the natural recovery process of the Zostera noltii bed. In addition, their relationship with community characteristics and environmental variables was studied. Moreover, biomass and morphometric attributes were investigated for their potential use as a complementary tool to the classical descriptor density (from which several other descriptors are derived) when studying nematodes as biological indicators. Nematode biomass and morphometric attributes proved to be valuable as correlate with the environmental changes associated with the Z. noltii collapse. High values of nematode biomass, length, width, and length/width ratio were observed during the early recovery process of Z. noltii, contrasting with nematode densities, which showed consistently higher values before the collapse. These findings suggest that biomass and morphometric attributes indicate a functional adaptation of nematode communities to the new environmental conditions in the early recovery process of Z. noltii. Therefore, these traits may be used to provide complementary information to standing stocks of nematode assemblages so as to assess ecological changes over spatial and temporal scales in marine ecosystems, particularly within seagrass bed habitats.