Plankton growth dynamic driven by plankton body size in deterministic and stochastic environments

In this paper, we establish a new phytoplankton-zooplankton model by considering the effects of plankton body size and stochastic environmental fluctuations. Mathematical theory work mainly gives the existence of boundary and positive equilibria, and shows their local as well as global stability in the deterministic model. Additionally, we explore the dynamics of V-geometric ergodicity, stochastic ultimate boundedness, stochastic permanence, persistence in the mean, stochastic extinction and the existence of a unique ergodic stationary distribution in the corresponding stochastic version. Numerical simulation work mainly reveals that plankton body size can generate great influences on the interactions between phytoplankton and zooplankton, which in turn proves the effectiveness of mathematical theory analysis. It is worth emphasizing that for the small value of phytoplankton cell size, the increase of zooplankton body size can not change the phytoplankton density or zooplankton density; for the middle value of phytoplankton cell size, the increase of zooplankton body size can decrease zooplankton density or phytoplankton density; for the large value of phytoplankton body size, the increase of zooplankton body size can increase zooplankton density but decrease phytoplankton density. Besides, it should be noted that the increase of zooplankton body size can not affect the effect of random environmental disturbance, while the increase of phytoplankton cell size can weaken its effect. There results may enrich the dynamics of phytoplankton-zooplankton models.

Comparisons of Zooplankton Community Structure between with- and without- Pesticide Applications on Rice Fields

Herbicide usage in rice fields over time may have a direct and indirect influence on the biodiversity of the fields. The impacts of herbicide usage on non-target organisms were assessed by examining the species richness and zooplankton density of two rice fields. One was 2.08 hectares in size and had been treated with pesticides during the sampling year (RF-PA). The second field, measuring 1.76 hectares, had received no pesticide treatment (RF-NPA). Every two weeks, zooplankton was quantitatively collected from ten sampling sites in each field. At each station, 20 L of measured water was filtered through a plankton net with a mesh size of 20 µm and preserved in 1% Lugol’s solution. The results revealed that RF-NPA and RF-PA had 112 and 88 species of zooplankton, respectively, with an abundance-based Jaccard index (Jabd) of 0.438. The total zooplankton density in RF-NPA was 24.4 ind./L, significantly higher than the 16.6 ind./L in RF-PA (p < 0.001). The Shannon-Wiener diversity index (H’) and evenness (J) were highest in RF-NPA at the second sampling (3.45 and 0.75, respectively). These results indicate that glyphosate application affects the diversity of species and density of zooplankton in rice fields.

Keanekaragaman Jenis dan Kepadatan Zooplankton di Perairan Pulau Makassar Kota Baubau

The purpose of the study was to determine the type and amount of zooplankton in the waters of Makassar Island, Baubau City. From the results of this study, it is expected that significant information regarding the types and zooplankton found in the sea around Makassar Island, Baubau City, whose waters are suitable for aquaculture. Furthermore, it is hoped that the results of this study can help improve and optimize the use of aquatic biological resources in the future. This research was conducted in the waters of Makassar Island, Baubau City, from August to October 2021. Sample identification was carried out at the Biology Laboratory of the Muhammadiyah University of Buton. The tool in this research field is plankton net no. 25 to filter zooplankton, GPS determines the sampling location, thermometer measures temperature, handrefactometer measures salinity, DO (Dissolved Oxygen) meter measures sea air oxygen, plastic bottles store seawater samples, small plastic bottles store zooplankton samples, and cool boxes for storing samples. Materials in the field are label paper and markers to label the sample, 70% alcohol to preserve the sample, and aqua water to sterilize the instrument. 1) From the three highest locations found 18 genera of zooplankton belonging to the Crustacea group. 2) With 33 ind/l, the genus OIthona dominates the waters of Makasar Island, Baubau City. 3) In the three locations, there was no variation in zooplankton density.

Zooplankton community in Thi Nai lagoon in the period of 2001–2020

This paper presents the results of the surveys on zooplankton in Thi Nai lagoon from 2001 to 2020. There were 179 species found in the lagoon, among which Copepod was the dominant group with 97 species (50.78% of total species), followed by Cladocera with 20 species (10.36%), Hydrozoa with 18 species (9.33%), Tunicata with 11 species (5.7%) and Siphonophora with 10 species (5.18%). Based on Bray-Curtis similarity analysis of zooplankton community and the station position, the sampling stations in the lagoon were grouped into three areas: The upper lagoon (UP), the middle (MI), and the mouth of the lagoon (MO). Among the surveyed years, there was a slight variation in the species number, while the density decreased by time and was especially low in 2020. Zooplankton density was much lower in the rainy season compared to that in the dry season, while the species number was less varied. Analysis of the differences between the areas in the lagoon demonstrated a clear distribution pattern of zooplankton with a decreasing density and an increasing number of species from upper lagoon to the mouth of the lagoon. Zooplankton diversity was less affected by time and only the Pielou index in the MI area between 2004 and 2009 was significantly different. Analysis of the various indices between seasons showed that the MO area was less volatile than the two other regions. The multi-dimensional scaling analysis demonstrated that zooplankton community was less variable by regions (50% similarity) compared to by the years (only 30% of similarity), except in 2009 and 2020 when differences among the areas were significant. Seasonal community change between the dry and rainy seasons was 30%.

Spatial Distribution of Plankton in Response to Ecological Dynamics in Tropical Shallow Lakes: Insight from Lake Malombe, Malawi

This study assessed plankton density and biomass in an attempt to better understand their spatial and seasonal variation in Lake Malombe. Samples were collected for analysis during the hot dry season (HDS) and cool dry windy season (CDWS). The zooplankton identified were T. cunningtoni (TC), M. aEq. Aequatorialis (MAA), T. neglectus (TN), Bosmina longirostris (BL), Diaphanosoma spp (DS), Nauplii, and Rotifer. These zooplankton groups belong to copepods, Cyclopidae, Cladocera, Ctenopod, and Rotifers. The phytoplankton biomass exhibited a strong seasonal variation with the highest value observed in HDS and lowest in CDWS. Zooplankton such as T. cunningtoni, M. aEq. Aequatorialis, T. neglectus, Bosmina longirostris, Diaphanosoma spp, Nauplii, and Rotifer were dominant during the HDS. The WT, pH, and DO, Chlo-a positively correlated with all zooplankton groups. The Na+ and K+ positively correlated with TC, MAA, DS, Nauplii, and Rotifers. The Cl− positively correlated with DS, Rotifers while, CO32− positively correlated with TC. HCO3− correlated with DS and Rotifers positively while TDS correlated with BL, Nauplii, and Rotifers negatively. Nitrite affected all zooplankton groups negatively while SRP had a positive effect on all zooplankton density. The study revealed that physical-chemical variables, some major ions, and Chlo-a are the most important factors influencing the spatial and seasonal variation of zooplankton density in the lake. These findings demonstrate the interaction between physical-chemical variables, phytoplankton, and zooplankton and highlight the significance of ecological understanding of the complex dynamics of food web system in tropical shallow lakes - under the changing climate.

Evaluating the Potential for Rearing Walleye in Lined Ponds Filled with Well Water

Walleye (Sander vitreus) fingerlings (30 to 35 mm) are commonly reared in ponds filled with surface (i.e., lake) water, but the use of ground (i.e., well) water would provide increased biosecurity. We assessed the potential for using well water to rear walleye by comparing plankton and water quality over 30 days between organically fertilized lined ponds that were filled with either unfiltered lake or well water. All ponds were inoculated with plankton that originated from Blue Dog Lake, filled by May 15, 2020, and remained fishless. Zooplankton density and body size were consistently reduced in well ponds suggesting that fry survival and growth would be reduced. Initially, well ponds exhibited higher ammonia-nitrogen and alkalinity, but lower pH owing to the inherent chemistry of the well water. Later, reduced ammonia-nitrogen combined with increased dissolved oxygen and pH suggest that decomposition of the organic fertilizer occurred slower in well ponds. A phytoplankton bloom was successfully initiated but was difficult to maintain despite consistently lower zooplankton density in well ponds. While the use of well water would enhance biosecurity, these data suggest that walleye fingerling production would be reduced relative to lined ponds filled with productive, lake water. Increasing organic fertilizer, supplementing with liquid 28N:0P:0K, and/or filling ponds earlier (e.g., 30 days) may provide a more favorable environment for walleye culture in lined ponds filled with well water.

Seasonal Variation of Zooplankton Density and Physicochemical Parameters of A Perennial Freshwater Body, Samudrabundh of Joypur, Bankura, West Bengal, India

Water is the most essential and vital component required for the survival of all organisms in this earth. The physico-chemical and biological characteristics of a water body determine its efficacy for the production of plankton especially the zooplankton. Zooplankton are the most important primary consumer of aquatic food chain which in turn influence the productivity of finfishes in an aquatic body .The present study is primarily based on assessment of seasonal density and diversity as well as the physico-chemical condition of Samudrabundh, of Joypur block of Bankura district, West Bengal. Such type of assessment on this water body has not been done before this.. The study was carried during March.2019 to February, 2020. The water quality parameters which were used for study were temperature, PH, Dissolved Oxygen (DO), Free carbon dioxide (CO2),Chloride, salinity, alkalinity and total hardness. A total of 26 taxa of zooplankton were recorded. Out of which 8 sp ecies comprises of Rotifera, 05 species of Copepoda, 10 species of Cladocera and 03 species of Ostracoda. The total zooplankton density ranges from 756 (Ind/L) to 957 (Ind/L) which is quiet lower than the desired value required for good fish culture. The study concludes that the water body is of soft water type and medium productive in nature.

ZOOPLANKTON OF TWO SHALLOW LAKES IN THE SOUTH OF MEAUCO FORMATION (LA PAMPA PROVINCE, ARGENTINA)

The Meauco Formation, a dune region of the central Pampa province, has numerous shallow lakes. Although there is hydrological information about them, it is very scarce about their limnological characteristics. The objectives are to know the physical-chemical and zooplankton parameters of two nearby shallow lakes, with and without fishes: Santa Isabel I (SI I) and Santa Isabel II (I II) respectively, and determine the influence of zooplankton on phytoplankton biomass and transparency. It was sampled during 2018 and 2019. In both the mean salinity were less than 1g.L-1 and the Secchi disk depth was around 0.45m. The chlorophyll concentrations varied between 9.32 and 11.63 mg.m-3. Seven cladocerans, 4 copepods and 20 rotifers were recorded. Most of the taxa were shared by both lakes, however, 20 rotifers were recorded in SI I and 13 in SI II. The total zooplankton density did not differ, but SI I had greater abundance of rotifers (69% of total) and SI II of crustaceans (72%). The presence of fish influences the zooplankton composition but its small size, even in the absence of fish, makes it have little influence on the phytoplankton; therefore, no differences were found in the transparency and phytoplankton biomass of both lakes.

Zooplankton communities in a river downstream from a lake restored with hypolimnetic withdrawal

Restoring lakes with hypolimnetic withdrawal can severely threaten water quality and biocenosis downstream. The objective of this study was to evaluate the effect of lake restoration on riverine zooplankton during a period of intense hypolimnion water inflow. Zooplankton density and biomass were determined in water samples. The water samples were also analyzed to determine the following physicochemical parameters: flow rate, dissolved oxygen, hydrogen sulphide, sulphate, ammonium nitrogen, nitrate nitrogen, total phosphorous, soluble reactive phosphorus, total organic carbon, and temperature. The results of multiple regression indicated that water flow was the most significant variable and was the best predictor of total zooplankton and rotifer density. Soluble reactive phosphorous was the main predictor of copepod biomass and density. Our study showed that hypolimnetic withdrawal disturbed the natural process of planktic community transformation, which was linked to the environmental shift from lacustrine to riverine. During the study, zooplankton density and biomass were low, but not as low as when the pipeline was operating at maximum output. At present, this lake restoration method has become more sustainable, because the adverse effects of hypolimnetic withdrawal on the recipient river have been minimized and limited to several weeks.

Is the zooplankton of mesosaline lakes in protected areas in the semiarid Pampa of Argentina different from those in lakes with high anthropic influence?

Most of the mesosaline lakes in the semiarid central Pampas have a high anthropic influence. The objective was to determine the limnological and zooplankton parameters of a mesosaline lake with little human impact, the West Lake of the Parque Luro Reserve, and compare it with previously studied aquatic ecosystems. Monthly samples were taken (2014–2015). The mean depth and salinity were 0.66 m and 29.33 g/L, respectively. The transparency was high and favored the growth of the macrophyte Ruppia cirrhosa. Zooplankton diversity was low, with autochthonous halophilic crustaceans (Daphnia menucoensis and Boeckella poopoensis). Zooplankton density was 20 to 100 times lower than that of other pampean lakes, probably due to the presence of the macrophyte, which distinguishes this lake from others in the region.