Does habitat restoration disturb? A case study of a shallow urban water reservoir in western India using cladoceran zooplankton.

Anthropogenic stressors, including restoration activities, can have ecosystem wide impacts, reflecting in various biotic components, particularly the basal levels in the trophic webs. Functional traits link taxonomic diversity to ecosystem function, thereby enabling a better ecological assessment of ecosystem health. We studied the effects of restoration activities on the community structure and functional diversity of freshwater cladoceran zooplankton in an urban water reservoir. Samples were taken in the early and late phases of the restoration work. Cladoceran species community and functional composition was significantly different between the two phases. There was a considerable reduction in taxonomic richness, functional richness and redundancy in the late phase. Taxonomic beta diversity between the two phases was explained more by nestedness. Habitat degradation due to haphazard restoration measures such as destruction of littoral zone and arbitrary desilting in addition to the dumping of untreated sewage could have contributed to the decrease in species and functional richness within the reservoir.

Seasonal variation in functional composition and diversity of cladoceran zooplankton of a lotic eutrophic habitat from India

This study explores the seasonal variation in functional composition, diversity and redundancy of Cladocera from an Indian lotic eutrophic habitat using two-year sampling data. Two seasonal clusters distinguishable by faunal and functional diversity patterns were obtained. Cluster A comprised of four functional groups while the ctenopod filter feeders were absent in cluster B. Cluster A had more number of species, higher functional divergence and lower redundancy than cluster B. Relatively, higher divergence values observed during the cluster A time period could be associated with set of functionally varied species occurring throughout the season. Decline in redundancy values seen within cluster A might be explained by the loss of littoral and benthic species in the peak of summer due to disappearance of submerged macrophytes and an increased nutrient load. Peculiar occurrence of Moina species in the most polluted months needs further investigation as a potential local pollution indicator.

Carbon Transfer from Cyanobacteria to Pelagic and Benthic Consumers in a Subtropical Lake: Evidence from a 13C Labelling Experiment

Eutrophication of lakes often results in dominance of cyanobacteria, which may potentially lead to serious blooms and toxic water. However, cyanobacterial detritus may act as an important carbon source for aquatic organisms. Using stable isotope carbon (13C) as a tracer, we assessed the carbon transfer from cyanobacteria to pelagic and benthic consumers in a 28-day outdoor mesocosm (~130 L) labelling experiment established in Lake Taihu, China, during a Microcystis aeruginosa bloom. The different organisms were labelled differently after addition of the labelled Microcystis detritus to the water. δ13C of particulate organic matter and of cladoceran zooplankton peaked earlier than for larger invertebrate consumers. Among the pelagic species, Daphnia similis had the highest Δδ13C, while the two snail species Radix swinhoei and Bellamya aeruginosa had lower but similar Δδ13C. The bivalves showed relatively modest changes in δ13C. The δ13C of Anodonta woodiana and Unio douglasiae showed a marginal though not significant increase, while a marked increase occurred for Arconaia lanceolate peaking on day 20, and Corbicula fluminea a slight increase peaking on day 9. Our results suggest that carbon from cyanobacteria can be incorporated by pelagic and some benthic consumers and eventually be transferred to higher trophic levels. Cyanobacterial carbon may, therefore, be considered an important carbon source supporting the entire food web during blooms, even if the cyanobacteria are not consumed directly.

Structural-functional organization of littoral zooplankton community of the upper Kremenchug reservoir in the territory of Kaniv nature reserve

The analysis results of the structural-functional organization of littoral zooplankton community of the upper Kremenchug Reservoir in the territory of Kaniv Nature Reserve during the summer of 2015 are presented. Diversity of zooplankton was presented with 34 species: Monogononta rotifers, cladocerans, copepods. The rotatoria-cladoceran zooplankton complex dominated in the taxonomic composition. Zhakkara dominant index for the comparison of the dominant species complexes was used, and it was the low number of similarities within the various biotopes of the six research stations (J = 7,1-28,6). This can be explained by the formation of higher aquatic plants.This led to the formation of specific zooplankton groups in overgrown biotopes.The ecological spectrum of the different groups of the upper Kremenchug Reservoir littoral zooplankton in the summer was characterized by the predominance of the phytophilic groups: phytophilic – 18 species (53 % of all zooplankton species). Depending on the feeding type the largest part was made by the peaceful group – 73,3 % (25 species). Summer littoral zooplankton in quantitative terms was characterized by very low development in both biotopes. Its density varied within 4077± 2098 ind./m³ and biomass 0,07 ± 0,04 g/m for overgrown biotopes, and 4123 ± 3929 ind./m³ and 0,054 ± 0,038 g/m³ for freshwater ones. Among the quantitative indicators, the species of Copepoda dominated, what was associated with the development of their larval stages (Nauplia, Сalanoida juv., Cyclopoida juv.) in the summer period.

Cladoceran diversity dynamics in lakes from a northern mining region: responses to multiple stressors characterized by alpha and beta diversity

The lakes surrounding the iron ore mining region of Schefferville, Quebec, Canada, sit within a landscape of historical disturbances, two of which have been relatively well documented over time: metal contamination and nutrient loading. Based on the analysis of sediment cores, we used cladoceran zooplankton subfossil assemblages from two lakes located in Schefferville to track both alpha and beta diversity over the last 100+ years. We showed that high metal concentrations were correlated with decreased cladoceran diversity, and that the site that experienced both direct wastewater input and atmospheric metal loading (Lake Dauriat) had the greatest declines in cladoceran richness. In both lakes, turnover in cladoceran assemblages was highest in the mining period. During the period of mine closures and improvement of wastewater treatment, some decreases in metal enrichment in the sediments and increases in cladoceran richness were observed in Lake Dauriat. Overall, a combined use of species richness and beta diversity metrics showed alpha and beta diversity are not always congruent, and that there are various ways to interpret scenarios of temporal beta diversity in northern freshwater systems.

Predator–prey interactions between native brine shrimp Artemia parthenogenetica and the alien boatman Trichocorixa verticalis: influence of salinity, predator sex, and size, abundance and parasitic status of prey

Trichocorixa verticalis (T. verticalis), native to North America and the Caribbean islands, is an invasive waterboatman species (Corixidae) in the southwest of the Iberian Peninsula. Previous studies in the native range have suggested that predation by T. verticalis can regulate the abundance of Anostracan and Cladoceran zooplankton in saline ecosystems, causing increases in phytoplankton through a trophic cascade. In this experimental study, we tested the predator–prey relationship between the native brine shrimp Artemia parthenogenetica, and T. verticalis from the Odiel salt ponds in SW Spain. In three experiments, we investigated (1) the effects of Artemia life stage (metanauplii, juveniles, and adults), (2) abundance (three, six, and 12 adult Artemia) and (3) parasitic status (Artemia infected with avian cestodes or uninfected) on predation rates by T. verticalis. We also considered how predation rates in all three experiments were influenced by the sex of T. verticalis and by different salinities (25 and 55 g l−1). Experiment 1 showed that predation rates were highest for metanauplii, possibly because their photophilic behavior makes them more prone to predation. In Experiment 2, we found that predation rate was higher for female T. verticalis and the higher salinity, although the strength of the sex effect varied between treatments. Experiment 3 showed that T. verticalis selectively predated adult Artemia infected with cestodes (red in color), as previously reported for predation by avian final hosts. Collectively, these results indicate that T. verticalis are important predators in their introduced range, and are likely to reduce the abundance of Artemia in more salt ponds as they expand their range, thus increasing phytoplankton abundance through trophic cascades.