Both aquatic and terrestrial biodiversity information can be detected in riverine water environmental DNA (eDNA). However, whether riverine water eDNA can be used to simultaneously monitor aquatic and terrestrial biodiversity remains unverified. To assess the effectiveness of using riverine water eDNA to simultaneously monitor the riverine and terrestrial biodiversity information, we proposed that the monitoring effectiveness could be approximated by the transportation effectiveness of land-to-river and upstream-to-downstream biodiversity information flows. Subsequently, we conducted a case study in a watershed on the Qinghai-Tibet Plateau. The case demonstrated that there was higher monitoring effectiveness on summer or autumn rainy days than in other seasons and weather conditions. The monitoring of the bacterial biodiversity information was more efficient than the monitoring of the eukaryotic biodiversity information. On summer rainy days, 43-76% of species information in riparian sites could be detected in water eDNA samples, 92-99% of species information in riverine sites could be detected in a 1-km downstream eDNA sample, and half of dead bioinformation (i.e., the bioinformation labeling the biological material that lacked life activity and fertility) could be monitored 4-6 km downstream for eukaryotes and 13-19 km downstream for bacteria. In this case, we tested the eDNA monitoring effectiveness assessment framework, in which the land-to-river monitoring effectiveness was indicated by detection probability, and the upstream-to-downstream monitoring effectiveness was described by the detection probability per kilometer runoff distance and by the half-life distance of dead bioinformation. It provided a new and usable tool for designing monitoring projects and for evaluating monitoring results.

Global climate change has led to a warmer world, changing the migratory and breeding behaviors of many species, and short-distance migrants may benefit from climate change. With climate change leading to an increasingly disordered climate, we show here that a disordered spring climate disturbs the migration and breeding of a short-distance anadromous fish. In 2020, on the Qinghai-Tibetan Plateau, an abnormally low temperature in April delayed the migration rhythm of Gymnocypris przewalskii by nearly 10 days, while the gonadal development rhythm of the breeding population was almost normal. The phenology mismatch decreased the migrating populations by 30–70%, reducing the larval flux by nearly 80%. This case reveals that for short-distance migrants, different phenologies within the same species respond to disordered climates differently, which leads to phenology mismatches and then threatens the species. Along with increasing local extreme weather and climate events, short-distance migrants need more attention and conservation actions.

Both aquatic and terrestrial biodiversity information can be detected in riverine water environmental DNA (eDNA). However, the monitoring effectiveness (i.e., the proportion of aquatic and terrestrial biodiversity information detected in riverine water eDNA samples) is unknown. To investigate the monitoring effectiveness, we introduced the concept of watershed biological information flow (WBIF) and proposed that the monitoring effectiveness depended on the transportation effectiveness of the WBIF. Then, the monitoring effectiveness could be assessed in the WBIF framework. Here, we conducted a monitoring effectiveness assessment case study in a watershed on the Qinghai-Tibet Plateau according to analysis of the bacterial operational taxonomic unit (OTU) assemblages detected in riverine water eDNA samples and riparian soil eDNA samples during three seasons. The results showed that (1) the downstream-to-upstream monitoring effectiveness: only 76% of the bacterial OTUs could be detected 1 km downstream in spring and more than 97% and 96% could be detected in summer and autumn, respectively. (2) The river-to-land monitoring effectiveness: more than 62% of the bacterial OTUs in riparian soil eDNA samples could be detected in adjacent riverine water eDNA samples on rainy summer days and 16% and 48% could be detected on cloudy spring and autumn days, respectively. These results suggested that riverine water eDNA was viable for simultaneously monitoring aquatic and terrestrial bacterial biodiversity and that rainy days in summer or autumn were suitable sampling times on the Qinghai-Tibet Plateau. More studies on monitoring effectiveness in other taxonomies and in other watersheds with different climatic conditions are needed.