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The community structure and ecological niche of benthic macroinvertebrates in the upper Yarlung Zangbo River were analyzed in April and September 2023. The benthic macroinvertebrate community largely comprises aquatic insects, with Diptera accounting for approximately half. Commonly observed were Chironomus anthracinus, Tadamus sp.1, Piscicola geometra, species of the family Corixidae spp. and the genera Monodiamesa sp., Apatania sp., and Valvata sp. in April, and Orthocladius sp.1, Gammarus sp., Isoperla sp., Nais sp., Baetis sp., Monodiamesa sp., Tanytarsus sp., Ilisia sp., Nebrioporus sp. and species of the family Corixidae spp. in September. The α-diversity analysis showed significant seasonal differences (p < 0.05) in Shannon–Wiener diversity variable and Margalef richness variable. The Pielou evenness variable did not show seasonal effects (p > 0.05). The β-diversity April/September differences can be attributed to species turnover rather than to nestedness, indicating that benthic macroinvertebrate diversity protection strategies are critical to all areas of the river. In April, Chironomus anthracinus exhibited the broadest ecological niche, and, in September, the widest niche was observed in Gammarus sp. The largest observed ecological niche overlap values were between Chironomus anthracinus and Valvata sp. in April and Gammarus sp. and Ilisia sp. in September, indicating interspecific competition. The study clarifies the diversity status of benthic macroinvertebrates in the upper Yarlung Zangbo River and provides data for related research to facilitate formulation of biodiversity conservation policies.

Chironomids have been widely used as indicators of trophic conditions of lakes due to their species-specific environmental requirements. In order to understand resilience and deterioration of aquatic ecosystems due to increases and/or decreases in external loading, recent chironomid community and water chemistry data of seven southern Finnish lakes with varying anthropogenic pressures and bathymetric properties were compared with similar data from the 1960s. Altogether 64 taxa were found. At present, the most numerous taxa are Procladius spp., Chironomus f.l. plumosus, Chironomus f.l. salinarius, Stictochironomus f.l. psammophilus, Benthalia spp., Tanytarsus spp. and Cladotanytarsus. In four lakes, current abundances of chironomid larvae are clearly lower, and in two lakes abundances are higher than during the 1960s. In two shallow, previously highly eutrophic lakes, the chironomid community composition revealed an improvement in the trophic status, while in three deep, previously moderately oligotrophic lakes, a slight deterioration was found. The most dramatic increase in chironomid density and diversity was found in a lake which was most heavily polluted in 1960s. In deep lakes, a slow gradual eutrophication seemed to be responsible for the observed replacement of the previous oligotrophic communities, dominated by Monodiamesa bathyphila, Stictochironomus spp., Polypedilum f.l. breviantennatum and Heterotanytarsus apicalis by eutrophic taxa such as Chironomus f.l. salinarius, Chironomus f.l. plumosus, Einfeldia spp., Sergentia coracina and Microtendipes spp. Among the key factors responsible for changes were dissolved oxygen concentration, food availability, sediment quality, and in one lake, toxic effluents from industry.

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [ Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae ( Tubifex tubifex , Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae ( Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.

Distributions of freshwater midges, including Chironomidae, Chaoboridae, and Ceratopogonidae, were analyzed along a transect of lakes extending north from Whitehorse (Yukon Territory) to the Arctic Ocean (Northwest Territories).Abiskomyia,Mesocricotopus,Monodiamesa, andParacladiuswere restricted to arctic tundra lakes, whereasChaoborus,Pseudochironomus,Polypedilum, andGlyptotendipeswere clearly associated with forest and forest–tundra environments. Many other taxa were broadly distributed with little apparent regard to latitude or ecoclimatic region. Canonical correspondence analyses revealed that midge distributions were most strongly correlated with total Kjeldahl N, maximum lake depth, pH, and summer surface water temperature. The distribution patterns suggest that subfossil midges may provide valuable proxy evidence for paleoenvironmental conditions in the Beringian region of northwestern Canada and Alaska.