Seven Years Study of the Seasonal Dynamics of Zooplankton Communities in a Large Subtropical Floodplain Ecosystem: A Test of the PEG Model

Irregular hydrological events, according to a classic plankton ecology group (PEG) study, can generate major deviations from the standard PEG model. However, little is known about the function of hydrological factors in influencing the seasonal dynamics of plankton. We used multivariate and Partial Least Squares Path Modeling to analyze the seasonal variation in crustacean zooplankton and related environmental factors from winter 2009 to winter 2016 in Lake Poyang, the largest freshwater lake in China. We found a distinct seasonal pattern in zooplankton development, which deviated, in part, from the PEG model, as we found indications of (1) a weaker degree of food limitation in winter and spring, likely due to high concentrations of allochthonous sources caused by decomposition of seasonally flooded hygrophytes, also affecting sediment dynamics; (2) a peak in crustacean zooplankton biomass in summer when the water level was high (and predation was lower), and where horizontal transport of zooplankton from the littoral zone to the pelagic was possibleand (3) a higher predation pressure in autumn, likely due to a shrinking water volume that left the fish concentrated in less water. The majority of these differences can be attributed to the direct or indirect impacts of physical factor variation.

Natural Feeding and Description of Clausocalanus furcatus Order Calanoida (Copepoda) in the coastal waters of Baniyas City (Eastern Mediterranean): التغذية الطبيعية ووصف النوع Clausocalanus furcatus رتبة Cyclopoida (Copepoda) في المياه الشاطئية لمدينة بانياس (شرق المتوسط)

This study, included the feeding of Clausocalanus furcatus of crustacean zooplankton (Calanoida), by studying the structure of the mandible and the gut content of this previous species to determine their favorite food. 93 samples have been collected vertically in period between March and October 2020. The samples were also accompanied with different hydrophysical and hydrochemical measurements in three regions that differ from each other with their environmental properties. The number of members of (C.furcatus) that were studied reached (64) individuals, of which (44) are female and (20) are male. On the other hand, determining the morphology, studying its structure, and knowing the content of the gut of the aforementioned species helped in expanding knowledge about the conditions and strategies of feeding it under the influence of environmental factors. The number of algae species (phytoplankton) that C.furcatus fed reached (9) species, of which (6) belong to the Dinophyceae, (2) species to Bacillariophyceae earth, and (1) only one species to the group Cryptophyceae. The highest average number of Dinophyceae was (1755), followed by Bacillariophyceae (505) individuals, then the group of Cryptophyceae (189) individuals.

Species diversity and community structure of crustacean zooplankton in the highland small waterbodies in Northwest Yunnan, China

Small waterbodies are a unique aquatic ecosystem with an increasing recognition for their important role in maintaining regional biodiversity and delivering ecosystem services. However, small waterbodies in Northwest Yunnan, one of the most concerned global biodiversity hot-spots, remain largely unknown. Here, we investigated the community structure of crustacean zooplankton and their relationships with limnological, morphometric and spatial variables in the highland small waterbodies in Northwest Yunnan in both the dry (October 2015) and rainy (June 2016) seasons. A total of 38 species of crustacean zooplankton were identified in our study, which is significantly higher than many other reported waterbodies in the Yunnan–Guizhou plateau as well as in the Yangtze River basin. This suggests that the highland small waterbodies are critical in maintaining regional zooplankton diversity in Northwest Yunnan. Meanwhile, we found limnological variables could explain most variation of crustacean zooplankton community, comparing to the morphometric and spatial variables in both the rainy and dry seasons. Our study revealed the diversity and community structure of crustacean zooplankton in the highland small waterbodies in Northwest Yunnan and highlighted the importance of small waterbodies in maintaining regional biodiversity.

Evaluating the performance of DNA metabarcoding for assessment of zooplankton communities in Western Lake Superior using multiple markers

For DNA metabarcoding to attain its potential as a community assessment tool, we need to better understand its performance versus traditional morphological identification and work to address any remaining performance gaps in incorporating DNA metabarcoding into community assessments. Using fragments of the 18S nuclear and 16S mitochondrial rRNA genes and two fragments of the mitochondrial COI marker, we examined the use of DNA metabarcoding and traditional morphological identification for understanding the diversity and composition of crustacean zooplankton at 42 sites across western Lake Superior. We identified 51 zooplankton taxa (genus or species, depending on the finest resolution of the taxon across all identification methods), of which 17 were identified using only morphological traits, 13 using only DNA and 21 using both methods. The taxa found using only DNA metabarcoding included four species and one genus-level identification not previously known to occur in Lake Superior, the presence of which still needs to be confirmed. A substantial portion of taxa that were identified to genus or species by morphological identification, but not identified using DNA metabarcoding, had zero (“no record”) or < 2 (“underrepresented records”) reference barcodes in the BOLD or NCBI databases (63% for COI, 80% for 16S, 74% for 18S). The two COI marker fragments identified the most genus- and species-level taxa, whereas 18S was the only marker whose family-level percent sequence abundance patterns showed high correlation to composition patterns from morphological identification, based on a NMDS analysis of Bray-Curtis similarities. Multiple replicates were collected at a subset of sites and an occupancy analysis was performed, which indicated that rare taxa were more likely to be detected using DNA metabarcoding than traditional morphology. Our results support that DNA metabarcoding can augment morphological identification for estimating zooplankton diversity and composition of zooplankton over space and time, but may require use of multiple markers. Further addition of taxa to reference DNA databases will improve our ability to use DNA metabarcoding to identify zooplankton and other invertebrates in aquatic surveys.

Confusing Invader: Acanthocyclops americanus (Copepoda: Cyclopoida) and Its Biological, Anthropogenic and Climate-Dependent Mechanisms of Rapid Distribution in Eurasia

Acanthocyclops americanus (Marsh, 1892), first described in Wisconsin (USA), was discovered shortly thereafter in Great Britain and then widely distributed in the Palearctic. Its current range includes Europe, North Africa, western and central Siberia with the largest number of findings along the migration tracks of aquatic birds. Until recently, the northern border was the 60th parallel, but in the last decade it has expanded further into the Arctic. The most rapid expansion of its range in Europe happened in the middle of the last century, which was partially hidden from scientists due to a taxonomic mistake caused by the merging of its name with the native Palearctic form Acanthocyclops robustus (Sars, 1863). This problem was solved only recently with the help of molecular genetic tools, allowing a return to the study of biological, anthropogenic and possible climate-dependent mechanisms of the successful rapid invasion of A. americanus into the Palearctic. This paper, along with a detailed description of the life cycle parameters, adaptive behavior of nauplii and population dynamics in Acanthocyclops americanus compared to those in two other native Acanthocyclops species (Acanthocyclops vernalis and A. robustus), provides a possible history of the biological invasion of A. americanus in the Palearctic. Special attention is paid to the climate-dependent mechanism of the expansion of its range into the north and far east of Asia. The introduction of the A.americanus into small lakes in Great Britain resulted in the dominance of this species in the summer plankton. In many high-trophic reservoirs in Belgium, France and Spain, as well as in newly built reservoirs in Europe, this species has become the only representative of crustacean zooplankton in the warm season. This has led to a significant transformation of the trophic webs of these reservoirs. The rapid dispersal of the invasive species, which was demonstrated by A. americanus in the last century, can make it difficult, and in some cases even impossible to study the historical reasons for the formation of the fauna of other invertebrates associated with such events including the movement of continents and the evolution of the Tethys Sea.

Development of trophic indices for lake Onego using of the ecological information system

GIS technologies were used to study the spatial distribution of zones with different trophic conditions in the water area of Lake Onego. Empirical data on the trophic conditions of waters sampled in 1982–2020 were as the basis for the map development. Two periods, before and after 2000, were considered separately to assess the impact of climate change. As indicators of trophic conditions, the number of saprophytic bacterioplankton, biomass of crustacean zooplankton, concentration of chlorophyll “a” and water transparency were used. All characteristics were converted to a normal distribution, and the values at individual points were interpolated for the entire water area of the lake, which was presented as a network of 544 squares. Each cell of the water area was characterized by four values of indicators. To assess trophic conditions, multivariate statistics (principal component analysis) and an expert system (Bayesian classifier) were used. The first principal component can be considered as the integral value of trophic conditions in a given part of the water area. The Bayesian classification method allows to get an estimate of the probability of classifying each cell in the water area as “high trophic conditions” and “low trophic conditions” and assign a significance threshold (p = 0.05). The cartograms built on the basis of both methods are basically the same. Most of Lake Onego area is characterized as low trophic conditions. The vast area with high trophic conditions was identified in the northwestern part of Lake Onego where on the coast large cities are located (Petrozavodsk and Kondopoga), which is associated with active anthropogenic pollution in the last century. In recent years, due to industry recession, trophic conditions in this area has sharply decreased, with the exception of Kondopozhskaya Bay, where there is an increase in water pollution as a result of trout farms.

Crustacean zooplankton communities, mixotrophic cililates, and optical properties in North Patagonian lakes, investigated by remote sensing

North Patagonian lakes are characterized by their oligotrophic or oligo-mesotrophic status. These conditions bring with them, respectively, the presence of abundant mixotrophic ciliates and a low species number of crustacean zooplankton under oligotrophic status, and low numbers of mixotrophic ciliates and a high species number of zooplankton under oligo-mesotrophic status. The aims of the present study are, (1) to use remote sensing techniques for determining abundances of mixotrophic ciliates and crustacean zooplankton, and (2) to characterize these mixotrophic and zooplankton communities by using null models. The sensing was accomplished from a satellite, i.e., by measuring the reflectance of the sunlight on a waterbody, which result will vary according to the contents of the water column. The results of Principal Component Analysis (PCA) revealed that sites with low reflectance of all bands have a high abundance of Stentor accompanied by low zooplankton absolute abundance, whereas a markedly opposite situation was observed under high reflectance, where Stentor has low abundance in conjunction with high zooplankton absolute abundances. The null models revealed that the communities in the studied sites do not have structured species associations, and that there is an overlap of niches. These results obtained agree with similar observations for Argentinean Patagonian lakes.