Zooplankton Species Richness Research Articles

Species Richness and Taxonomic Distinctness of Zooplankton in Ponds and Small Lakes from Albania and North Macedonia: The Role of Bioclimatic Factors

Resolving the contribution to biodiversity patterns of regional-scale environmental drivers is, to date, essential in the implementation of effective conservation strategies. Here, we assessed the species richness S and taxonomic distinctness Δ+ (used a proxy of phylogenetic diversity) of crustacean zooplankton assemblages from 40 ponds and small lakes located in Albania and North Macedonia and tested whether they could be predicted by waterbodies’ landscape characteristics (area, perimeter, and altitude), together with local bioclimatic conditions that were derived from Wordclim and MODIS databases. The results showed that a minimum adequate model, including the positive effects of non-arboreal vegetation cover and temperature seasonality, together with the negative influence of the mean temperature of the wettest quarter, effectively predicted assemblages’ variation in species richness. In contrast, taxonomic distinctness did not predictably respond to landscape or bioclimatic factors. Noticeably, waterbodies’ area showed a generally low prediction power for both S and Δ+. Additionally, an in-depth analysis of assemblages’ species composition indicated the occurrence of two distinct groups of waterbodies characterized by different species and different precipitation and temperature regimes. Our findings indicated that the classical species-area relationship hypothesis is inadequate in explaining the diversity of crustacean zooplankton assemblages characterizing the waterbodies under analysis. In contrast, local bioclimatic factors might affect the species richness and composition, but not their phylogenetic diversity, the latter likely to be influenced by long-term adaptation mechanisms.

Analysis of the morphological structure of diapausing propagules as a potential tool for the identification of rotifer and cladoceran species

The study of zooplankton diversity through the analysis of the active community implicates repeated samplings at different sites of the lake, throughout different seasons and years. A valid cost-effective alternative for the analysis of zooplankton species richness is represented by the study of their diapausing propagules. This method allows retrieving in a single sampling the same number of species found in the water column over a period of many years. However, the lack of a reference database of diapausing propagules’ diagnostic characters has, so far, precluded the use of morphology for the identification of egg species. In the present study, an analysis of the morphological characters of rotifer and cladoceran diapausing propagules was performed with Light Microscope (LM) and Scanning Electron Microscope (SEM) to identify possible diagnostic features that would allow identification of their species without having to incubate the sediment first to obtain adults that can be identified. A total of 3780 diapausing eggs of 23 species of rotifers and cladocerans, collected in eleven lakes from five different regions of Spain and Mexico, were morphologically analyzed. High evidence of species-specificity was observed in most rotifer species, while cladoceran diapausing propagules could be only identified to genus level.

Planktonic indicators of trophic states for a shallow lake (Baiyangdian Lake, China)

Eutrophication in lake ecosystems poses a serious threat to the water quality and function of aquatic ecosystems. The species composition and community structure of plankton change directly with variations in lake trophic states. Seasonal sample collections of phytoplankton, zooplankton and environmental variables were conducted in spring, summer, and fall from a large shallow lake, Baiyangdian Lake, China. The species richness, community composition and temporospatial variations of phytoplankton and zooplankton were analyzed. The lake trophic states were assessed using the comprehensive trophic state index (CTSI) and rotifer trophic state index (TSIROT). The results indicated that 69.1% of the lake area showed slight eutrophication, 29.3% showed mesotrophication, and 1.6% showed moderate eutrophication. The Shannon-Wiener diversity index and Pielou evenness index were employed to assess the community diversity of phytoplankton and zooplankton. The dominant taxa and most dominant species of phytoplankton and zooplankton were determined; Cyanophyta and Rotifera were the dominant phytoplankton and zooplankton taxa, respectively. Microcystis sp. and Polyarthra vulgaris were the most dominant species of phytoplankton and zooplankton, respectively. Redundancy analysis (RDA) was applied to identify the key environmental variables that influenced the species, diversity indices and species abundance of phytoplankton and zooplankton. The results showed that ammonia nitrogen (NH4+), total nitrogen (TN), total phosphorus (TP), and dissolved oxygen (DO) were the main environmental factors influencing the species abundance and diversity. The current lake plankton species number and diversity index were lower than those in past decades, as determined by comparing the community characteristics of phytoplankton and zooplankton with historical records. Comparisons of TN:TP ratios with those of other lakes suggested that nitrogen was the limiting nutrient for lake eutrophication. Baiyangdian Lake could have a high potential for eutrophication based on the environmental and ecological characteristics of the lake.

Temporal Variations in Abundance and Species Richness of Zooplankton with Emphasis on Ichthyoplankton in the Subtidal Waters of Umm Al-Namil Island, Northwestern Arabian Gulf of the ROPME Sea Area

Zooplankton, including the ichthyoplankton, abundance and species richness over time in the subtidal waters of Umm Al-Namil Island, Kuwait Bay, were sampled and quantified from September 2016 to August 2017. At the same period, physicochemical measurements (i.e., water temperature, pH, salinity, dissolved oxygen and nutrient concentrations) occurred. A total of 9 larval fish families were identified: Acropomatidae, Bregmacerotidae, Bythitidae, Clupeidae, Engraulidae, Leioganthidae, Platycephalidae, Pseudochromidae and Sparidae, in addition to fish eggs. Other zooplankton were mainly represented by Copepoda, followed by Radiolaria and Molluska larvae. Generally, some sampling events (i.e., months) had 100% fish larvae, while others had 0% fish larvae. The physicochemical parameters showed variations at each sampling event as well as within the same season. Total zooplankton (including ichthyoplankton) mean abundance was highest in summer (22.65 ± 2.85 ind.5l-1), while winter (18.13 ± 1.64 ind.5l-1) and autumn (17 ± 2 ind.5l-1) mean abundance values did not significantly vary. The lowest mean abundance was observed in spring (14.33 ± 1.67 ind.5l-1). Mean species richness was highest during spring (7.22 ± 1.66), but not significantly different from autumn (7 ± 2). No significant difference was observed between winter (6.73 ± 1.64) and summer (5.90 ± 2.85). Overall, the results indicate that zooplankton species richness and abundance in Umm Al-Namil Island varied temporally in response to fluctuations in environmental conditions. Primary among these fluctuations is water temperature at different seasons of the year.

Dispersal mitigates biologically induced disturbances in heterogeneous metacommunities

AbstractThe global increase in anthropogenic disturbances has introduced patterns of heterogeneity across many landscapes. Local disturbances are often studied from the perspective of the local habitat patch, where their direct effects on local community composition are more evident. However, local disturbances can have regional implications when connected to other patches within a metacommunity. Invasive species provide a unique opportunity for studying the influence of biologically induced disturbances on metacommunity dynamics, because invasive species are influential in structuring local communities and have a propensity for dispersing across landscapes, producing gradients in disturbance intensity. The invasive zebra mussel, Dreissena polymorpha, is widespread throughout the eastern USA and is having negative impacts on native communities. Using zebra mussels to induce disturbances in mesocosm zooplankton communities, we tested how the relative abundance of disturbed and undisturbed habitat patches within a metacommunity influenced community and metacommunity biodiversity and composition. The zebra mussels negatively affected pelagic zooplankton species richness, while facilitating the population growth of littoral species. Undisturbed communities mitigated disturbance‐induced local and regional pelagic species loss in heterogeneous metacommunities, while the fully disturbed metacommunity experienced significant losses of pelagic zooplankton at local and regional scales. Disturbed communities influenced undisturbed communities in heterogeneous metacommunities by increasing the densities of littoral zooplankton species. Overall, these results highlight the important effects that undisturbed habitat patches can have on mitigating species loss in locally disturbed patches and maintaining regional biodiversity in heterogeneous metacommunities.

Relationship between zooplankton richness and area in Brazilian lakes: comparing natural and artificial lakes and trends

Abstract Aim We analyzed the relationship between zooplankton species richness and the area of 34 natural and 55 artificial lakes in Brazil (total of 89), with area varying between 0.01 to 2,430 km2. Methods A total of 33 studies were found in the specialized bibliography, containing data from zooplankton sampled in the limnetic areas, here analyzed through descriptive statistics, nonparametric group comparisons, Spearman correlation, and non-linear regression. Results The relationship between zooplankton richness and area in Brazilian lakes depend both on the size and type of the environments. Contradicting aspects of the biogeographic theory, in small environments (up to 6 km2) there is no significant influence of the area on the richness, whether it is natural (ponds) or artificial (dams, reservoirs). The natural lakes present greater richness and habitat variation independent of the size, possibly due to a more diverse composition of niches. Large natural lakes are scarce in Brazil but, with dams, area and zooplankton richness are positively correlated on an intermediate scale, up to 39 km2, critical point of size from which species’ richness stabilizes. Conclusions For the artificial lakes of large or intermediate size in Brazil, area and richness of microcrustaceans have a point from which richness starts to stabilize, as would be expected by the biogeographic theory. But in small size environments there is no evidence confirming this association. Also, it is observed that the natural lakes present higher and more variable values for richness than the artificial ones.

Trophic state (TSISD) and mixing type significantly influence pelagic zooplankton biodiversity in temperate lakes (NW Poland).

BackgroundLake depth and the consequent mixing regime and thermal structure have profound effects on ecosystem functioning, because depth strongly affects the availability of nutrients, light, and oxygen. All these conditions influence patterns of zooplankton diversity. Zooplankton are a key component of the aquatic environment and are essential to maintaining natural processes in freshwater ecosystems. However, zooplankton biodiversity can be different regard to depth, mixing type and trophic state. Therefore, the aim of this study was to examine how depth and mixing regime affect zooplankton diversity in lakes. We also investigated the vertical distribution of diversity across a trophic gradient of lakes.MethodsA total of 329 zooplankton samples from 79 temperate lakes (36 polymictic and 43 dimictic) were collected. The biodiversity of zooplankton was calculated using species richness (SR) and the Shannon index (SI). An index based on Secchi disc visibility was used to determine the trophic state index (TSISD) of lakes. The one-way ANOVA with Duncan’s post hoc test were used to determine differences in zooplankton biodiversity between mictic lake types and thermal layers. To find the best predictors for zooplankton biodiversity a multiple stepwise regression was used. The rarefaction method was used to evaluate the impact of mixing types, thermal layers, and the TSISDon zooplankton biodiversity indices. A Sørensen similarity analysis and nonmetric multidimensional scaling (NMDS) were performed to describe the similarity patterns in species composition among lakes.ResultsWe identified a total of 151 taxa from 36 polymictic and 43 dimictic lakes. Lake depth and the TSISD were significantly correlated with the biodiversity of lake zooplankton. The results of ANOVA and Duncan tests show that mictic type and thermal zones had a significant effect on zooplankton biodiversity. The rarefaction curve showed significant differences in zooplankton biodiversity, which was greater in lakes with lower trophic state. Ordination by NMDS showed clustering of different mictic types, thermal layers, and composition changes throughout the TSISDprofile. Moreover, we determined that polymictic lakes are more heterogeneous than dimictic lakes in regard to zooplankton similarities.DiscussionBoth mictic lake types were characterized by varying levels of zooplankton biodiversity, which is shaped by the communities’ response to lake depth, thermal layers and TSISD values. The zooplankton SR and SI (during daylight hours) depends greatly on the mixing type. Lake type also indicates the importance of the metalimnion in shaping zooplankton biodiversity in dimictic lakes. In addition, data from NW Polish lakes indicated that the increase of the TSISD leads to taxonomic shifts and has a negative effect on the diversity of all groups of zooplankton.

Summer assessment of zooplankton biodiversity and environmental control in urban waterbodies on the Island of Montréal

AbstractWaterbodies in urban environments are usually built or maintained to serve socioeconomic functions. However, they also represent ecosystems that can contribute notably to urban biodiversity. To better understand contribution to biodiversity of urban ecosystems, the variation in zooplankton community composition in 19 waterbodies across the Island of Montréal (Québec, Canada) was monitored across three summer months. Communities were dissimilar between and within waterbodies with species richness differences and replacement patterns playing equal parts in shaping the observed variation. Within each waterbody, notable differences were detected between months, which can affect biodiversity estimation or community composition assessment. Zooplankton species richness was especially well explained by macrophyte cover, which had a positive effect. Compositional differences were also explained by macrophyte cover and by waterbody emptying. Partitioning the beta diversity revealed that only richness difference patterns were explained by macrophyte cover, as species replacement patterns were not explained by any of the measured environmental variables.

Modeling species richness and abundance of phytoplankton and zooplankton in radioactively contaminated water bodies

Water bodies polluted by the Mayak nuclear plant in Russia provide valuable information on multi-generation effects of radioactive contamination on freshwater organisms. For example, lake Karachay was probably the most radioactive lake in the world: its water contained ∼2 × 107 Bq/L of radionuclides and estimated dose rates to plankton exceeded 5 Gy/h. We performed quantitative modeling of radiation effects on phytoplankton and zooplankton species richness and abundance in Mayak-contaminated water bodies. Due to collinearity between radioactive contamination, water body size and salinity, we combined these variables into one (called HabitatFactors). We employed a customized machine learning approach, where synthetic noise variables acted as benchmarks of predictor performance. HabitatFactors was the only predictor that outperformed noise variables and, therefore, we used it for parametric modeling of plankton responses. Best-fit model predictions suggested 50% species richness reduction at HabitatFactors values corresponding to dose rates of 104-105 μGy/h for phytoplankton, and 103-104 μGy/h for zooplankton. Under conditions similar to those in lake Karachay, best-fit models predicted 81-98% species richness reductions for various taxa (Cyanobacteria, Bacillariophyta, Chlorophyta, Rotifera, Cladocera and Copepoda), ∼20-300-fold abundance reduction for total zooplankton, but no abundance reduction for phytoplankton. Rotifera was the only taxon whose fractional abundance increased with contamination level, reaching 100% in lake Karachay, but Rotifera species richness declined with contamination level, as in other taxa. Under severe radioactive and chemical contamination, one species of Cyanobacteria (Geitlerinema amphibium) dominated phytoplankton, and rotifers from the genus Brachionus dominated zooplankton. The modeling approaches proposed here are applicable to other radioecological data sets. The results provide quantitative information and easily interpretable model parameter estimates for the shapes and magnitudes of freshwater plankton responses to a wide range of radioactive contamination levels.

Restoration of a shady urban pond – The pros and cons

The Bzura-7 pond (Łódź, Poland) is a typical shallow and shady urban reservoir situated on the Bzura River that is exposed to pollutants introduced mainly by internal loads and the supply from the catchment. In 2010–2012, the following characteristics were observed in the pond: a high allochthonous input of organic matter, high concentration of ammonium, low concentration of dissolved oxygen and low diversity of zooplankton, dominated mainly by Daphnia spp. From January to June 2013, restoration measures were performed, including sediment removal, increasing light access to the pond and construction of a sequential sedimentation-biofiltration system (SSBS). The aim of the present study was to investigate how the water quality in the Bzura-7 pond was affected by the restoration process, which included reducing pollutant inflows and enhancing habitat potential, thus increasing the diversity of this ecosystem. Restoration efforts improved the chemical and physical parameters of the water. The oxygen concentration increased, and the concentrations of TN and ammonium significantly decreased. Despite the increase in pond lighting, the growth of cyanobacteria was limited. However, we observed increased abundance of green algae and diatoms but less than adequate changes in the zooplankton community structures. Although we observed a significant increase in the zooplankton species richness after restoration, this increase was related to the small-bodied groups of zooplankton, rotifers and bosminiids, characteristic of eutrophic ecosystems. In addition, a planktivorous fish – sunbleak (Leucaspius delineatus) – was identified as an unintended side effect of the restoration effort. Further conservation efforts in the Bzura-7 pond and monitoring of results are still needed.

Regional Dispersal Influences Zooplankton Community Response to Dreissena polymopha Invasion

Aquatic systems are becoming increasingly susceptible to invasive species whereby local species are reduced in abundance and richness leading to changes in many food webs. Dispersal of species from surrounding lakes may provide a natural mechanism to increase local resistance by providing a diversity of locally adapted species to colonize affected communities. This study examined how zooplankton dispersal could potentially reduce the effects of the invasive zebra mussel, Dreissena polymorpha, on zooplankton community total abundance, species richness and diversity. Field experiments were conducted in 20 large tanks, with five replicates, to observe zooplankton community response to (1) the presence and absence of zebra mussels, and (2) the presence and absence of regional disperser zooplankton. Live regional zooplankton, from six surrounding lakes, were added fortnightly to dispersal treatments, while heat-killed zooplankton were added to no-dispersal treatments. All tanks were sampled for chlorophyll and zooplankton community samples prior to dispersal additions. Zooplankton were counted and identified as cladocerans and copepods (macrozooplankton), and rotifers (microzooplankton) to species. In the presence of mussels, chlorophyll was significantly depleted, reducing nutrient availability. All zooplankton richness and abundance decreased suggesting strong resource competition and direct predation by mussels. Dispersal did not affect macrozooplankton community structure, however, dispersal influenced the effect of zebra mussels on rotifers, further decreasing richness. This suggests species from the surrounding lakes may be highly competitive among local species, further proposing that regional species may influence zooplankton community structure and responses to zebra mussel invasion, but the effect is species dependent.

Salinity shapes zooplankton communities and functional diversity and has complex effects on size structure in lakes

Changes in zooplankton community structure and function were analyzed in 24 lakes covering a wide salinity gradient (from 0.5 to 115 g l−1) in a semiarid region in northwest China. We hypothesized that species richness (S), species diversity (H), functional diversity (FD), biomass, and size of zooplankton would decrease with increasing salinity. We found that S, H, and FD did decrease with increasing salinity, whereas zooplankton sizes, size range, and biomasses did not. In fact, the sizes of microcrustaceans were mainly regulated by the abundance of small fish. Besides the impoverishment of FD, the zooplankton functional groups also varied along the salinity gradient. A shift occurred from selective raptorial to more generalist microphagous rotifers, from selective to more generalist filter feeder cladocerans, and from dominance of microphagous herbivorous copepods to microphagous carnivores. Our study indicates that the ongoing salinization of lakes with climate warming will result in important changes in the zooplankton, affecting not only the structure but also the functioning of this community. A weakened top-down control by zooplankton on phytoplankton at moderate high salinities may be an indirect consequence, leading to a worsening of eutrophication symptoms. Loss of fish at high salinities may, however, counteract this effect.

Crustacean zooplankton communities in Chiloé Island coastal lakes (42°S, Chile)

The lakes of Chiloé Island have a high dissolved organic carbon concentration (known as “humic”) and show a connection with brackish water. They also display a high species richness of crustacean zooplankton. The aim of the present study is to characterize the potential factors that explain crustacean species richness in Chiloé Island lakes. To that purpose parameters of the abiotic environment were determined. The results of PCA performed on those data revealed the existence of three lakes with high crustacean species richness that are relatively deep, show high nitrogen concentrations, and are located at relatively high altitude. In contrast, there are two lakes with low species richness, high mineral concentration, and situated at low altitude. One of these lowland lakes gives rise to a river effluent to the sea, and it is connected to the other lake; these observations agree with the results of a performed cluster analysis. Nevertheless, the co-occurrence null model analysis revealed the absence of regulator patterns in species associations, which could be explained to the fact that many of the species occur in most of the lakes. These results are markedly different in comparison to Patagonian lakes of Argentina and Chile that have a low crustacean species number.

Influence of environmental factors on vertical distribution of zooplankton communities in humic lakes

The influence of vertical environmental gradients on zooplankton communities was studied in five humic lakes with the high availability of food resources (phytoplankton and bacterioplankton) and low fish pressure. The factors that inhibit the development of large zooplankton in humic lakes are currently widely debated. We have found that relatively productive humic lakes do not offer many niches for zooplankton because of the sharp thermal gradient which results in a shallow layer of oxygenated waters. The results of this study indicated that different taxonomic groups of zooplankton are determined by a different set of environmental variables. This phenomenon explains very low species richness of zooplankton and a possibility of their coexistence in the narrow oxygenated layer. We concluded that due to sharp thermal gradient in humic lakes biomass of herbivores may be reduced which could promote development of phytoplankton.

8. The Effect of Bythotrephes Longimanus on the Size Structure of Zooplankton Communities in the Muskoka Region, Ontario

Invasive species are considered the greatest threat to aquatic ecosystem biodiversity. Bythotrephes longimanus, an exotic zooplankton species introduced to North America in the 1980s, is threatening the structure of indigenous aquatic ecosystems as it continues to invade inland Ontario lakes. As a predacious zooplankton species, B. longimanus has been shown to decrease zooplankton abundance, species richness and shift zooplankton community size structure in invaded lakes. However, much of the previous research concerning the predatory effects of B. longimanus has been on surveys of a small number of lakes or has been in controlled mesocosm or lab-based experiments. This study examines the effects of B. longimanus on the zooplankton community using size-structure characterizations (grouping individuals from the community based on size) as community measures for 311 lakes in the Muskoka Region, a highly invaded watershed in Southern Ontario. More specifically, the study explores the size-spectra of invaded versus uninvaded lakes, with reference to an array of environmental lake characteristics (water chemistry, lake morphometry,etc.), and the relevance of B. longimanus activity on the regional scale. By using such a large-scale survey we will be able to appreciate regional-scale effects, as well as encompass the multiple and more indirect trophic interactions that B. longimanus is likely having with the entire aquatic community. (Funding: NSERC & CAISN.)

Environmental and zooplankton parameter changes during the drying of a saline shallow temporary lake in central Argentina

Central Argentina has numerous saline lakes sustained by groundwater sources and rainfall. These lakes are temporary and experience significant changes in water level and salinity, depending on wet and dry climate cycles. This study aims to investigate the scarcely known dynamics of environmental and zooplankton parameters during the drying phase of one of these lakes. Monthly samples were taken from December 2 012<br />to July 2 013 in the Ojo de Agua Uriburu lake, previous to its drying. At the beginning of the study, the lake’s depth was 0.7 m and its salinity was 16.65 g/L, later, in July, its depth decreased to 0.06 m and its salinity increased to 92.9 g/L. Zooplankton species richness was low (three crustaceans and three rotifers), with <em>Boeckella poopoensis</em> and <em>Moina eugeniae</em> dominating in the system. Maximum density and biomass were attained<br />by the two dominant species in April (318.5 ind/L and 3 029.1 g /L dry weight; and 242.4 ind/L and 1 530.4 g/L dry weight, for <em>B. poopoensis</em> and <em>M. eugeniae</em>, respectively), and no correlation was found between these parameters and salinity. Maximum average body lengths for both species were observed in the last months of sampling (<em>M. eugeniae</em>: 1 020 84.2 m and<em> B. poopoensis</em>: 1 348.8 89.0 m). At this point of the study, neither juvenile nor larval stages were found. The increase in average body size is, arguably, the result of increased salinity in the system through a negative<br />effect on reproduction. Because this lake reached hypersalinity, its ecological dynamics are unique among those of other temporary, saline lakes that dried in central Argentina. Similar studies on other temporary ecosystems are needed to increase the information on these little known ecological aspects.

Responses of trophic structure and zooplankton community to salinity and temperature in Tibetan lakes: Implication for the effect of climate warming

Warming has pronounced effects on lake ecosystems, either directly by increased temperatures or indirectly by a change in salinity. We investigated the current status of zooplankton communities and trophic structure in 45 Tibetan lakes along a 2300 m altitude and a 76 g/l salinity gradient. Freshwater to hyposaline lakes mainly had three trophic levels: phytoplankton, small zooplankton and fish/Gammarus, while mesosaline to hypersaline lakes only had two: phytoplankton and large zooplankton. Zooplankton species richness declined significantly with salinity, but did not relate with temperature. Furthermore, the decline in species richness with salinity in lakes with two trophic levels was much less abrupt than in lakes with three trophic levels. The structural variation of the zooplankton community depended on the length of the food chain, and was significantly explained by salinity as the critical environmental variable. The zooplankton community shifted from dominance of copepods and small cladoceran species in the lakes with low salinity and three trophic levels to large saline filter-feeding phyllopod species in those lakes with high salinity and two trophic levels. The zooplankton to phytoplankton biomass ratio was positively related with temperature in two-trophic-level systems and vice versa in three-trophic-level systems. As the Tibetan Plateau is warming about three times faster than the global average, our results imply that warming could have a considerable impact on the structure and function of Tibetan lake ecosystems, either via indirect effects of salinization/desalinization on species richness, composition and trophic structure or through direct effects of water temperature on trophic interactions.

Habitat age influences metacommunity assembly and species richness in successional pond ecosystems

AbstractMetacommunity theory suggests that species diversity can depend upon the time since initiation of community assembly, or habitat age, as the relative influence of regional and local structuring processes changes over succession. There are, however, few studies that evaluate the role of habitat age in structuring species richness (diversity–age) over large, fine‐resolution age gradients of secondary succession in metacommunities. To test theoretical predictions of diversity–age relationships in metacommunities, zooplankton species richness and composition along a successional chronosequence in beaver (Castor canadensis) ponds were evaluated. The age of ponds was determined using dendrochronology and historical photography, and ranged from 23 to 69 yr of age. A unimodal relationship between zooplankton species richness and habitat age was observed among the successional ecosystems. This hump‐shaped relationship with community assembly time is congruent with theoretical predictions of species richness in metacommunities and can be explained by the increasing importance of local, relative to regional, structuring processes over successional trajectories. Observed patterns of diversity and composition responded to age‐mediated effects on the local pond environment; older ponds were deeper, had lower colored dissolved organic carbon, and were permanent. Additionally, there were weak but significant dispersal effects on community composition across the region. The lack of consistent community composition by successional stage reflected variation from differences in pond nutrient availability and species dispersal. The results indicate that regional and local age‐dependent structuring mechanisms operate at each successional stage on different local colonist pools and environments yielding communities that reflect succession in their richness response. Consequently, secondary succession should be considered an influential driver of species diversity across temporal and spatial scales in metacommunities.

Resilience and resistance of zooplankton communities to drought-induced salinity in freshwater and saline lakes of Central Asia

Effects of drought-induced salinity changes on aquatic communities are less studied in lentic than in lotic systems. We present changes in zooplankton assemblages from five arid lakes before, during, and after a supra-seasonal drying event in which lake inflow ceased in 2001. We catalogued zooplankton communities in fresh and saline lakes of the Sudochye wetland in Central Asia. During this record low flow period, salinity increased in the lakes. Zooplankton species richness was inversely correlated with salinity. Linear regression using species richness indicated that zooplankton communities in the two least saline lakes were strongly correlated with changes in salinity. Post-drought recovery of species richness suggested resilience to this perturbation. Both saline lakes' zooplankton communities had low correlation with changes in salinity, suggesting greater resistance than the freshwater communities. The fifth lake showed a hybrid response, beginning in the fresh range, but experiencing higher salinities than the other fresh lakes. In the fifth lake species-richness was similarly correlated to changes in salinity as compared to the saline lakes, correlation of % halotolerant species was intermediate between saline and fresh communities, and post-drought species richness was similar to the fresh lakes, which could indicate a “resilient” recovery of species richness.

Linking watershed land uses and crustacean assemblages in Mediterranean wetlands

The watershed land uses in Mediterranean wetlands are essential to understand the functioning of aquatic communities. This study was designed to assess the relationship between watershed land uses, wetland characteristics and zooplankton assemblages (branchiopods and copepods) in 24 Mediterranean wetlands of the southern Iberian Peninsula, which greatly differ in both wetland land uses (olive groves, pasture, scrublands, and forest) and in their morphometric and limnological features. Firstly, results from a Principal Component Analysis allowed us to classify wetlands in two categories: impacted and non-impacted. Then, one-way Analysis of Variance was performed to test differences in zooplankton species richness and a Permutational Analysis of Variance was performed to test differences in zooplankton assemblages between categories. Lastly, a Non-metric Multidimensional Scaling analysis was chosen for the lake-by-species ordination. The results support the hypothesis that zooplankton richness and composition were negatively affected by watershed land uses, mainly agriculture practices. Moreover, species zooplankton assemblages were clearly linked to the two different wetlands categories. The present study puts forward the important role of zooplankton community for testing land use effects in Mediterranean wetlands.