The Interaction Between The Hyporheic Macroinvertebrate And Fine-sediment

Excessive deposition of fine sediment filling interstitial spaces in riverbed substrates is widely acknowledged to negatively impact the aquatic ecosystems.Macroinvertebrates,sensitive to ecological status,respond to the clogged substratum through more intense bioturbation.To better understand the interaction between hyporheic macroinvertebrates and fine sediment,a continuum of a naturally increasing fine sediment content in the Weihe River was investigated through field sampling in four seasons.Data analysis was carried out with the help of R software,nonmetric multidimensional scaling(NMDS)was employed to assess the distribution and the homogeneity in the composition variation of macroinvertebrate assemblages;the similarity of community structure at the same-type clogged sites was assessed by the Cluster analysis.Canonical correspondence analysis(CCA)was performed to reveal the context-dependent relevance of bioturbation activity and the variability of bioturbation in different sampling sites and seasons was clarified with the bioturbation potential value.The main findings of the study are shown below:1)The effects of fine sediments on hyporheic macroinvertebrate community structure were revealed.The study shows that the effect of fine sediment on hyporheic macroinvertebrate community is seasonally dependent due to changes in environmental factors such as flood events and water quality.The abundance is greatest at moderately clogged sites and decreases at heavily clogged sites,in addition,most of the same-type clogged-sites have a similar community composition.Oligochaeta(Tubifex,Limnodrilus),Chironomus and Plannorbidae are more closely associated with heavily clogged sites,while Baetidae,Hydropsychidae and Heptageniidae with lightly clogged sites.Regarding the functional trends,collector-filterer and scaper are significantly associated with lightly clogged sites,while shredder and collectorgatherer were more closely associated with moderately clogged sites.2)The context-dependent relevance of hyporheic macroinvertebrate bioturbation was analyzed.The results shows that hyporheic macroinvertebrate bioturbation is also seasonally dependent.The bioturbation is strongest in summer and at moderately clogged sampling sites.Hydrological variables have a greater impact on bioturbation in summer(normal flow season)and autumn(high flow season),while water quality factors such as dissolved oxygen and conductivity have a greater impact in winter and spring(dry flow season).3)The mechanism of interaction between hyporheic macroinvertebrates and fine-sediments was further clarified.The results shows that the interaction between hyporheic macroinvertebrate and fine-sediment is mediated by both environmental factors and seasons.The interaction is not linearly correlated but rather limited.The study highlights the feasibility of hyporheic macroinvertebrates as indicators for the effects of fine sediment loading pressures on lotic ecosystems and the necessity of reach-specific conservation and management strategies,especially in the downstream.