Influence of bryophyte biomass and organic matter quantity on the abundance and richness of oligochaetes in forest streams with different phytophysiognomies in southeastern Brazil

Aquatic oligochaetes can be found associated with different types of substrates; including bryophytes (mosses and liverworts) adhered to stones in lotic ecosystems. However, little information is available on the association between oligochaetes and bryophytes in tropical region. Therefore, the aims of this study were: to investigate whether the assemblages of oligochaetes respond to variation in the biomass of bryophytes and quantity of particulate organic matter (POM) present on these plants; verify differences in the composition of oligochaetes in streams flowing through areas with two phytophysiognomies (rocky field and seasonal semideciduous forest). The samples were collected from five first-order streams in the southeast of the state of Minas Gerais. Six samples of bryophytes adhered to stones were obtained from each stream. A total of 1586 oligochaetes were collected and 11 taxa were identified, belonging to the families Naididae and Enchytraeidae. The most abundant taxa were Bothrioneurum (37.95%) and Enchytraeidae (33.01%). A positive relation was observed between oligochaete abundance and POM in two streams (Ibitipoca I and Ibitipoca III) and a positive relation was found between oligochaete abundance and bryophyte biomass in one stream (Ibitipoca I). The composition of the fauna varied within and between the phytophysiognomies studied. The results show that the oligochaetes find favorable conditions to establish themselves in bryophytes, evidencing the ecological importance of these plants as habitat for invertebrates.