Short-term effects of substrate surface structure on macroinvertebrates community structure and functional characteristics

Stones are one of the important natural materials in soil bioengineering and are widely used in river ecosystem restoration projects. After stones are introduced into the river channel, they become a crucial component of the riverbed substrate. Substrate is a crucial habitat for macroinvertebrates. The surface structure of substrate plays a vital role in providing habitat for a greater diversity of macroinvertebrates, thus contributing significantly to the enhancement of riverine biodiversity. This study was conducted in the headwater streams of Changbai Mountain. Complexity was introduced to the substrate surface by adding rough treatments on concrete blocks, as well as different sizes of grooves and holes. The study found that the control substrate (GK0/GT0) took the shortest time (7 d) to establish a relatively stable macroinvertebrate community. In contrast, other treated substrates required a longer time to form relatively stable communities due to the increased available living space on the substrate surface. Overall, various diversity indices were relatively higher on rough substrates compared to smooth substrates. Specifically, at 28 d, the groove-treated substrate MT1 had the highest species richness (18.67) and Shannon-Wiener diversity index (H ', 2.85), which were 2.68 times and 1.54 times higher than the control, respectively. Similarly, at 28 d, the hole-treated substrate MK1 exhibited the highest species richness (20.35) and H ' (2.84), which were 2.90 times and 1.53 times higher than the control, respectively. With the gradient changes in groove and hole sizes, macroinvertebrate species richness, density, H ', Margalef richness index (dM), and Simpson dominance index (D) on different substrates showed an initial increase followed by a decrease trend. Additionally, attached organisms were the dominant taxa on all treated substrates, with higher densities of burrowers in hole-treated substrates and more swimmers in groove-treated substrates. Substrates with larger holes favored the settlement of larger-bodied macroinvertebrates, while substrates with small grooves had higher abundances of various-sized macroinvertebrate groups. It is evident that differences in substrate surface structure have a significant impact on macroinvertebrate diversity and functional characteristics. Therefore, in river ecosystem restoration projects, adding necessary textural structures to the substrate surface can enhance the effectiveness of river ecosystem restoration.