Shifts in Estuarine Macroinvertebrate Communities Associated With Water Quality and Climate Change

The present work aims to identify changes in the macroinvertebrate community of the Tagus estuary (Portugal) due to improvements in water quality and to climate change. Data was collected over a period of 16 years (1998–2014) from different sites located along the estuarine gradient. The AZTI Marine Biotic Index (AMBI) was used to assess the ecological quality status based on benthic invertebrate communities and identify possible variations associated with changes in water quality. The overall distribution of each species was examined to detect possible changes associated with climate, based on species’ affinity for more temperate or subtropical climates. Results demonstrate that there was an overall improvement of AMBI scores during the assessment period. The analysis of the geographical distribution of benthic species seems to indicate that there has been an increase of species which prefer subtropical climates in the shallower waters of the estuary, whereas in the deeper estuarine sections the propensity is for species that prefer temperate climates.

Benthic invertebrate communities in the water areas of the Volgograd reservoir near the villages Akhmat and Zolotoye as one of the characterization of conditions for commercial fish reproduction in 2020

The main factor affecting the success of the reproduction of limnophilic fish is the level height and duration of the spring flood with uniform heating of the water. However, the efficiency of fish reproduction also depends on other factors, for example, on the development of the food supply for early juveniles. In 2020, in the water area of the Volgograd reservoir near the villages Akhmat and Zolotoye, according to the results of catches of fry net, developed very unfavorable conditions for the reproduction of commercial fish. The values of production indicators (net primary production and the rate of respiration of the plankton community) in 2020 turned out to be minimal. The dynamics of the abundance, and especially the biomass of benthic invertebrate communities, turned out to be very similar for both water areas in 2018 and very different in 2020. In terms of abundance, among benthic invertebrate communities, in the water area near the village Zolotoye in July 2020, was dominated by oligochaetes and chironomids, and oligochaetes in terms of biomass. At the station near the village Akhmat in July was dominated by chironomids in terms of numbers, and oligochaetes in terms of biomass. In August and September, both in terms of abundance and biomass, oligochaetes dominated in both water areas. There is a correlation between the state of production processes and the state of benthic invertebrate communities in the reservoir. However, the efficiency of fish reproduction correlates, first of all, with the level and temperature regimes of the reservoir during the spawning and feeding period. The decrease in the proportion of underyearlings of crucian carp and perch feeding on benthic invertebrate communities in the catch of fry net in 2020 may be due to both an unfavorable level regime and a drop in the feeding capacity of the water areas.

Do changes in temperature affect EU Water Framework Directive compliant assessment results of central European streams?

Background Benthic invertebrate communities are an integral and longstanding component of stream biomonitoring. However, multiple stressors driven by global change threaten benthic invertebrate communities. In particular, climate warming is expected to disrupt freshwater ecosystems. While an increasing number of studies have shown changes in benthic invertebrate community composition in response to climate warming, the effect on stream assessments has rarely been investigated. As several community composition metrics are also used in stream assessments, we predicted that climate warming would worsen stream assessment results. Therefore, we used a comprehensive data set of 2865 benthic invertebrate samples taken between 2000 and 2014 from small central European low mountain streams. We examined the effects of changes in temperature on common community and stream assessment metrics. We used 31 metrics covering composition, richness, tolerance and function of communities, of which many are used in various stream assessment schemes. Results Against our expectations, we identified a decreasing air temperature trend of − 0.18 °C over 15 years. This trend was accompanied by significant changes in community composition, for example, increases in species richness and decreases in the community temperature index (CTI). Further, we identified slight concomitant improvements of various globally used stream quality assessment metrics, such as a decreasing saprobic index and an increasing BMWP. Conclusions While temperature increased by + 0.9 °C during the past 30 years (1985–2014), our 15-year study period (2000–2014) showed a decrease by − 0.18 °C. Therefore, we regard the concomitant improvement in several assessment metrics as a recovery from prior increasing temperatures. In turn, we assume that increases in water temperature will lead to opposite effects and therefore cause declining assessment results. Water managers should be aware of this linkage that in turn could provide a chance to mitigate the effects of global warming by, for example, planting trees along the rivers and the removal of artificial barriers to increase current velocity to minimize a warming effect.