Diversity and temporal-spatial distribution of macroinvertebrate functional feeding groups in the middle reaches of the Huaihe River

Functional feeding groups (FFGs) of macroinvertebrates serve as vital indicators for assessing aquatic ecosystem health. This study aims to elucidate the spatiotemporal distribution patterns of FFGs and their environmental driving mechanisms in the middle Huai River, thereby providing scientific basis for watershed ecosystem health assessment. From 2019 to 2020, 28 sampling sections were set up in the main stream of the middle reaches of the Huaihe River, from Sanhejian to Hongshantou. The survey area was divided into three reaches: the upper section of Linhuaigang Gate (Section U, 6 sections), the section from Linhuaigang Gate to Bengbu Gate (Section M, 16 sections), and the lower section of Bengbu Gate (Section D, 6 sections). Investigations were carried out in the normal water period, flood period, and dry period to explore the spatiotemporal distribution patterns of FFGs of macrobenthos and their correlation with environmental factors. The results show that: 1) A total of 68 species of macrobenthos (Some identified to the genus level) were identified in the middle reaches of the Huaihe River, belonging to 3 phyla, 7 classes, and 21 families, with Limnodrilus sp. being the common dominant species; 2) Analysis based on FFGs reveals that there were 5 functional feeding groups in the three hydrological periods in the middle reaches of the Huaihe River, with their relative abundance ranking as follows: collectors > filter-feeders > shredders > scrapers > predators. Collectors dominated the spatiotemporal distribution; 3) The species diversity indexes showed significant spatiotemporal differences. Section M had the highest Shannon-Wiener diversity index and Margalef richness index, Section U had the highest evenness index, and the diversity was the highest in the normal water period; 4) The results of redundancy analysis (RDA) indicate that the normal water period was mainly affected by water depth, the flood period was mainly affected by nitrite nitrogen, dissolved oxygen, and permanganate index, and the dry period was mainly affected by ammonia nitrogen and permanganate index. The study shows that there are complete FFGs of macrobenthos in the middle reaches of the Huaihe River, and their distribution is synergistically affected by hydrological periods and main environmental factors.