First record of Xestochironomus Sublette and Wirth, 1972 (Chironomidae: Chironominae) in the Mexican Nearctic with notes on their habitat

We report the first record of Xestochironomus Sublette and Wirth, 1972 for the Mexican Nearctic. Larvae of Xestochironomus are known from the Neotropics and Nearctic regions. We report them for the Sonora river, NW Mexico, 300 km SW from the closest previous record in the U.S. Habitat data are provided and discussed. Our finding provides supporting evidence for the continuous presence of the genus throughout the Americas, including desert systems

Variability in mentum deformities of Tanytarsus larvae (Diptera, Chironomidae) in a metal rich basin in Northern Mexico

Mentum deformities in chironomids have been commonly used as indicators of metal contamination in freshwater ecosystems. Incidence of these deformities suggests sublethal effects and can provide early signals of environmental deterioration. While anthropogenic metal pollution is known to lead to an increase in deformities in chironomids, natural background deformity incidence information is key to their effective use as biomonitoring tools. Here we explore the incidence of deformities from 5000 Tanytarsus (Diptera, Chironomidae) menta in relation to water physicochemical, and sediment metal (Al, As, Cu, Fe, Mn, Pb, Zn) concentration data from numerous sites in the naturally metal-rich Sonora River (NW Mexico) obtained over a two-year period. Higher metal concentrations were found in the upper basin. Higher salinity, total suspended solids and conductivity were found in the lower basin. Only As and Cu were occasionally found above published threshold effect levels (TEL). The proportion of deformities (% D) was low (2.1%) and a generalized linear model only explained 25.36% of % D variability among samples; this model included several physicochemical parameters. The only metal significantly related to deformities was Cu. Despite significant spatial and temporal variability in all metal concentrations and other physicochemical parameters in the basin, we were unable to explain a strong relationship between metal concentration and deformity incidence. Our results, based on consistent % D quantification from 5000 samples from a single taxon, suggest that natural variation in metal concentrations, even when statistically significant, is not associated with notable variations in the incidence of deformities

The Biological Assessment and Rehabilitation of the World’s Rivers: An Overview

The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2–3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally