Limnologica最新文献

Competition is one of the main drivers of population dynamics of cladoceran species. According to the Size Efficiency Hypothesis, large-bodied cladocerans are superior competitors over small-bodied species because they are more effective filter-feeders and can consume a wider size spectrum of food particles. However, we hypothesized that food quality in terms of phosphorus (P) and/or polyunsaturated fatty acid (PUFA) content can alter competitive interactions, and these potential effects can be modified by temperature. Since large-bodied cladocerans are more vulnerable to poor food quality and are regarded as less adaptive to high temperatures, we hypothesized that large-bodied species would be superior competitors at low temperature and/or high food quality, while small-bodied cladocerans would be competitively superior at enhanced temperature and/or poor food quality. To verify this hypothesis, we conducted laboratory experiments with the small-bodied D. longispina and large-bodied D. magna fed with three different types of food: (1) P-poor and PUFA-rich green algae (low phosphorus or LP-treatment), (2) PUFA-poor-cyanobacteria treatment (CYANO) and (3) P-rich and PUFA-rich green algae (high phosphorus or HP-treatment) at 18°C and 24°C. We found that D. magna had a stronger suppressive competitive effect on D. longispina in all food quality and temperature treatments. Nevertheless, food quality and temperature modified competitive interactions between the small- and large-bodied Daphnia. In HP and CYANO, both Daphnia species were more strongly suppressed by competitor presence at high than low temperatures, whereas in LP mutual suppression was relatively weaker at higher temperatures. This phenomenon was attributed to higher requirement for P at enhanced temperature which created constraints for population growth thus decreasing competitive interactions at higher temperatures. Mutual competitive suppression in CYANO was weaker than in the HP treatment although cyanobacteria had the greatest negative impact on the abundance of both Daphnia species. In general our results show that the outcome of competition between large and small-bodied cladoceran species was not affected by food quality and/or temperature, yet, these factors markedly altered competitive interactions between species.

Plants of riparian forests provide abundant dead leaves for freshwater stream ecosystems which support detritus-based food webs. The increased replacement from natural riparian forests to Eucalyptus plantations, an exotic species distributed throughout the neotropic landscapes, alters leaf breakdown as a key ecosystem process. We evaluate the breakdown of native and exotic leaf species with distinct physical and chemical characteristics (traits) in two different tropical reference condition streams located in Cerrado and Atlantic Forest biomes. We tested the hypothesis that regardless of the leaves’ origin (native or non-native species), leaf litter with higher nutrients and less recalcitrant compounds has higher decay rates. Eucalyptus camaldulensis leaf breakdown was faster than the native species Miconia chartacea in both streams. Leaf breakdown was driven by local characteristics (context dependent) and the macrodecomposer community, with more intensity to the litter's intrinsic physical and chemical quality. The higher leaf breakdown of E. camaldulensis was evidenced in the Atlantic Forest stream, that with the most increased water flow, further accelerating the leaf breakdown. Our findings indicate that due to the innate physical and chemical characteristics of E. camaldulensis, its decomposition occurs at a faster rate compared to native tropical species, as evidenced by the stream flows.

The urban rivers, including Changwang, Meishe, and Wuyuan in Haikou City, China, are vital water resources. Despite the rivers experiencing anthropogenic impacts, limited studies have investigated their water quality and ecological community structure. This study assessed zooplankton functional groups' spatial and seasonal dynamics relative to environmental factors in the three urban rivers. The samples were collected and analyzed seasonally between March and December 2019. The environmental factors varied significantly at spatial and seasonal scales (p < 0.05). Meishe and Wuyuan Rivers had higher electrical conductivity, salinity, TN, and TP than Changwang, which had low turbidity. Seasonally, higher TP, TN, NH₃-N, and COD_Mn levels were found in the spring, while summer and autumn experienced high temperatures. Additionally, spring and summer had high Chl-a levels. Likewise, spring had the lowest heavy metal concentrations, while nearly all metals were elevated in winter and summer. Generally, the average metal content followed the order of Mn > Zn > Cu > Ni > As > Cr > Co > Pb > Cd. The environmental parameters were within class III of the China standard for surface waters (GB 3838–2002), suggesting negligible pollution. This study identified 159 zooplankton species, including 62 Rotifers, 50 Protozoans, 31 Cladocerans, and 16 Copepods. They were classified into 11 functional groups, dominated by Rotifers filter feeders (RF), Rotifers carnivores (RC), and small copepods and cladocerans filter feeders (SCF), followed by Middle copepods and cladocera carnivores (MCC) and Middle copepods and cladocerans filter feeders (MCF). Analysis of similarity (ANOSIM) revealed seasonal differences (p < 0.001) in zooplankton functional groups, with RF and RC most dominant in summer, autumn, and winter, while SCF, MCF, and MCC were dominant in spring. Hence, the redundancy analysis (RDA) and Pearson Correlation analysis revealed that temperature, Chl-a, TP, salinity, COD_Mn, NH₃-N, TN, As, Co, and Cd were the main environmental factors influencing zooplankton functional groups. This study helps understand urban rivers' water quality and ecological community structure, bridging the knowledge gap. The findings are essential for water quality monitoring and management.

Lake browning is considered a severe water quality problem in lake ecosystems, but it has received considerably less attention in water protection than eutrophication. Current metrics used in lake surveillance monitoring programmes, including the European Union’s Water Framework Directive, do not reflect browning sufficiently. The aims of the study were to explore the potential role of the functionality of rotifers as browning indicators and to improve understanding of the environmental parameters driving the functionality and diversity of rotifers. Seasonal data on rotifer communities and water quality from seven lakes with differing water colour and trophic conditions were analysed. The feeding guilds of rotifers enabled differentiation between lakes in terms of their ecological conditions, and, in particular, eutrophic and brown-water lakes were clearly distinguished from other lakes. The guild ratio of rotifers was positively affected by water colour, but inversely related to total phosphorus concentration. Our results suggest that zooplankton functionality provides a potential tool to assess ecosystem dynamics, particularly when assessing lake browning. Thus, our results suggest that application of the guild ratio of rotifers is a promising method to estimate the general browning status of lakes and may complement the metrics used in Water Framework Directive.

Ostracods are taxonomically and ecologically diverse small crustaceans that have recently gained prominence in laboratory studies and environmental impact assessment. In this context, the present study aims to assess the applicability of a new freshwater ostracod for experimental studies in the laboratory, and we provide the formal description of Strandesia rondoniensis n. sp. The original specimens for setting the laboratory cultures originated from the Natural Park of Porto Velho, in the Amazon region (Rondônia State, Brazil). The growth and reproductive rates of eleven adult individuals of S. rondoniensis n. sp. were analyzed. The results showed a high morphological resemblance with Neostrandesia striata and Bradleytriebella lineata, even though the new species belongs to Strandesia, indicating evolutionary convergence. The life cycle analysis showed that individuals of S. rondoniensis n. sp. have fast growth and high reproductive rates, which favour their use in laboratory studies. Besides contributing to the knowledge about ostracods in the Amazon region, which has been poorly studied, the life cycle experiment characterizations provided here should promote the use of this new species as a model organism for laboratory studies.

Nonmarine ostracods are widely distributed in a variety of aquatic habitats, from mountain lakes to underground waters, where each species tends to show species-specific habitat preferences with unique functional traits to increase their survival chances. To understand the patterns of such a relationship between habitat preferences and functional traits of the species, 101 different aquatic sites in the Kastamonu province (Türkiye) were randomly sampled during August 2023. A total of 39 ostracods (20 species, 19 unnamed taxa) were encountered from 49 sites. Seventeen species are new reports for the province. Among them, six species are the most common species with cosmopolitan (or cosmoecious) characteristics. The contribution of these species to the diversity of alpha species (p < 0.05) was more than 90 %. The species with relatively high ecological tolerances generally unveiled low-optimum estimates. Canonical correspondence analysis explained 62.5 % of the correlation between environmental variables and species in which redox potential, electrical conductivity, calcium, and pH were found to be the most related variables to the species (p < 0.05). Fundiversity analysis showed that the presence of swimming setae was correlated with high values of functional diversity, functional richness, and functional distribution of species among five elevation ranges. The results of the habitat selection index and the standardized selection index coincided with the functional traits of the most common species. The species characterized by their habitat selection can be considered as diagnostic species of those specific habitats. Among them, Neglecandona neglecta, reported primarily from dams, springs, and troughs, is considered a typical diagnostic species of these habitats, while Cypridopsis vidua found in lakes and dams can be used as an indicator species for these types of lentic habitats. Similarly, three species (Heterocypris incongruens, Ilyocypris bradyi, Psychrodromus olivaceus) can play a critical role as diagnostic species in troughs but reporting them from different habitats such as ditches and rivers / lakes (I. bradyi) and dams (P. olivaceus and H. salina) indicated their wide range of habitat preferences. Hence, the results suggest that the occurrence of diagnostic species seems to correspond to certain habitat types and their functional traits.