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

Abstract

Benthic nematodes are recognizable suitable organisms to provide valuable information on potential ecological effects of natural and anthropogenic disturbances in aquatic ecosystems. Biomass and morphometric attributes of nematodes (body length, width and length/width) in the Mira estuary (SW Portugal) were analysed before the collapse and during the natural recovery process of the Zostera noltii bed. It was investigated how nematode biomass and morphometric attributes were related to community characteristics and environmental variables. Moreover, biomass and morphometric attributes were investigated for their potential use as complementary tools 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 a correlate with the environmental changes associated with the Z. noltii collapse. The results showed high values of nematode biomass, length, width, and length/width ratio 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 are indicative of the functional adaptation of nematode communities to the new environmental condition in the early recovery process of Z. noltii. Therefore, these traits may be used to provide complementary information to standing stocks of nematodes assemblages to assess ecological changes over spatial and temporal scales in marine ecosystems, particularly within seagrass bed habitats.