Development of a phytoplankton-based index of biotic integrity for ecological health assessment in the Yangtze River

Background The application of index of biotic integrity(IBI)to evaluate river health can be an essential method for river ecosystem management.However,these types of methods were developed in small,low-order streams,and are therefore,infrequently applied to large rivers.To that end,phytoplankton communities and environmental variables were monitored in 30 sampling segments of the middle and lower reaches of the Yangtze River,China during the wet(July-August)and dry(November-December)seasons in 2017-2018.We developed a phytoplankton-based index of biotic integrity(P-IBI)and used the index to assess the ecological health of the Yangtze River.Relationships among P-IBI,its component metrics,and environmental factors were analyzed across different seasons.Results Results obtained from the P-IBI indicated that the phytoplankton-based ecological health of the Yangtze River was rated as“good”during both seasons,with an overall better condition in the dry season.During the wet season,there were scattered river segments with P-IBI ratings of“fair”or below.Water quality and land use appeared to shape the patterns of P-IBI.In the wet season,P-IBI negatively correlated with total phosphorus,nitrate,total suspended solids,turbidity,conductivity,and dissolved oxygen.In the dry season,P-IBI positively correlated with total nitrogen,ammonium,and nitrite,and negatively correlated with water temperature.Conclusions The ecological health of the Yangtze River as reflected by the P-IBI exhibited spatial and temporal variability,with the effect of water quality being greater than that of local land use.This study indicated the importance of considering seasonal effects in detecting large river ecological health.These findings enhanced our understanding of the ecological health and characterized potential benchmarks for management of the Yangtze River.These findings also may be applicable to other large rivers elsewhere.

Influence of Geomorphology on Fish Fauna of a Small Mississippi Bluffline Stream

Fish were collected from 39 sites on the main channel and major tributaries of a highly erosive stream, Hotophia Creek. A total of 2,642 specimens representing 38 species were collected between 1986 through 2003. The bluntface shiner Cyprinella camura was the dominant species of fish and when grouped with other cyprinids accounted for 38.0% of the total numbers collected. By weight, Lepisosteusoculatus, Lepomismegalotis, lctiobusbubalus, and Lepomismacrochirus were the dominant species; accounting for 49.9% of the total catch. While more diminutive species such as cyprinids that might be subject to predation by large fish more frequently were found in shallow channels. Fishes with specific habitat requirement such as the pirate perch were found in the middle group of sites, that were disturbed by erosion process but that featured the necessary habitat requirements. Sensitive or intolerant species like the Yazoo darter, creek chubsucker and cyprinids in general were more frequently found in the undisturbed and habitat complex channels. This study supports the hypothesis that geomorphological stream stages are associated with specific communities of fishes.