Spatiotemporal Dynamics of Water Body Changes and Their Influencing Factors in the Seasonal Lakes of the Poyang Lake Region

Poyang Lake is the largest freshwater lake in China, an internationally important wetland and the largest migratory bird habitat in Asia. There are numerous seasonal lakes in the Poyang Lake region, and these lakes create a complex and diverse wetland landscape and serve as the main activity area for migratory birds. Seasonal lakes have significant effects on hydrological and ecological processes and are highly susceptible to various changes, but research on seasonal lakes is relatively limited. Based on long-term remote sensing images, this study analyzed the spatiotemporal variation characteristics of seasonal lakes and their influencing factors and ecological effects. The conclusions were as follows: the average water area of seasonal lakes showed a unimodal change during the year, reaching a maximum in July and a minimum in January. The interannual water area fluctuated greatly, and the overall water area showed a small downward trend. In terms of spatial variation, the seasonal lakes were connected with the main lake in the wet season and separated from the main lake in the dry season. Among the natural factors, the influences of temperature, evaporation, and rainfall on the water area of the seasonal lakes were successively reduced. In addition, the incoming water from the Yangtze River had an important influence. Among the human factors, the traditional fishing method “enclosing sublakes in autumn” had the greatest impact on the water area in a specific period, followed by the indirect impact of the Three Gorges Project.

Occurrence of BIOMPHALARIA GLABRATA and PHYSA ACUTA (gastropoda: mollusca) snails in Quinta da Boa Vista municipal park, Rio de Janeiro, RJ, Brazil

The human species has an emotional connection with nature called “biophilia” (or, love for life). This connection goes from generation to generation, being one of the reasons why green spaces are present in large cities. Quinta da Boa Vista is a municipal park in Rio de Janeiro located in the São Cristóvão neighborhood in the northern part of the city. Its main attraction is the artificial lake system, a leisure attraction for the local community. This article reports the presence of Biomphalaria glabrata and Physa acuta snails around the main lake in the Quinta da Boa Vista Municipal Park in Rio de Janeiro, RJ. Seventy-one B. glabrata and twenty-seven P. acuta snails were collected. The snails were measured and examined for the presence of trematode larvae according to standardized procedures. The prevalence rate of B. glabrata was estimated at 15.5%. Rediae and cercariae resembling those of the species Typhlocoelum cucumerinum (Typhlocoelidae, Digenea) which parasitizes aquatic birds of the order Anseriformes were found. This study reinforces the importance of monitoring park lakes and ponds to better understand the risk of helminth transmission by molluscan vectors.KEY WORDS: Snails; Schistosomiasis; Digenea; Quinta da Boa Vista; Rio de Janeiro.

Population characteristics of Oreochromis niloticus (Linnaeus, 1758) in light of varying water quality conditions of adjoined Lakes Naivasha and Oloidien in Kenya

Nile tilapia Oreochromis niloticus (L.) is a recent re-introduction in Lake Naivasha and is one of the fish species that has crossed into Lake Oloidien. This study assessed and compared the population characteristic of O. niloticus under different physicochemical conditions of water in L. Naivasha (main) and L. Oloidien. Samples of water for selected water quality parameters and fisheries data from catch survey were collected between 2017 and 2018. Results indicate the highest conductivity levels recorded in 2018 as 2916 ±11.30 µScm-1 and 282.33 ± 4.33 µScm-1 for L. Oloidien and L. Naivasha respectively. Mean total lengths of O. niloticus were 19.1± 1.8 cm and 23.6 ± 2.9 cm for L. Oloidien and L. Naivasha respectively. Mean weight of O. niloticus was 129.3 ± 37.8 g in L. Oloidien and 260.9 ± 81.0 g in L. Naivasha. Length-weight relationship analysis showed a negative allometric growth (b = 2.526) and (b = 2.983; p > 0.05) in lakes Oloidien and Naivasha respectively. The relative condition factor (Kn) values were slightly lower in O. niloticus from L. Oloidien compared to the main Lake. Differences between the two lakes in the population characteristics of O. niloticus may be attributed to the observed differences in the habitat conditions, including the conductivity and pH levels.

Physics and geochemistry of lakes in Vestfjella, Dronning Maud Land

Shallow Antarctic surface lakes belong to the most extreme aquatic environments on the Earth. In Vestfjella, proglacial surface lakes and ponds are characterized by a 2–5 month long period with liquid water and depths < 2 m. We give a detailed description of nine seasonal lakes and ponds situating at three nunataqs (Basen, Plogen and Fossilryggen) in western Dronning Maud Land. Their physical and geochemical properties are provided based on observations in four summers. Three main ‘lake categories‘ were found: 1) supraglacial lakes, 2) epiglacial ponds and 3) nunataq ponds. Category 3 lakes can be divided into two subgroups with regards to whether the meltwater source is glacial or just seasonal snow patches. Supraglacial lakes are ultra-oligotrophic (electrical conductivity < 10 μS cm−1, pH < 7), while in epiglacial ponds the concentrations of dissolved and suspended matter and trophic status vary over a wide range (electrical conductivity 20–110 μS cm−1, pH 6–9). In nunataq ponds, the maxima were an electrical conductivity of 1042 μS cm−1 and a pH of 10.1, and water temperature may have wide diurnal and day-to-day fluctuations (maximum 9.3°C) because snowfall, snow drift and sublimation influence the net solar irradiance.

Distribution of arsenic, silver, cadmium, lead and other trace elements in water, sediment and macrophytes in the Kenyan part of Lake Victoria: spatial, temporal and bioindicative aspects

This is the first detailed report on the distribution of Ni, As, Sr and Ag in water, sediments and macrophytes from Lake Victoria, complemented with recent data on the heavy metals Cr, Cu, Zn, Cd and Pb. The study was conducted over an 11-month period at five sites in the Kenyan part of Lake Victoria: four sites in the Winam Gulf influenced by various anthropogenic pressures including a site near Kisumu City, and one in the main lake, perceived to have lesser direct anthropogenic influence. Compared with the main lake site, the water in Winam Gulf had significantly higher values for electrical conductivity and concentrations of dissolved components: organic carbon and bound nitrogen, as well as major and most trace elements. This contamination is also evident in surface sediments, which contained significantly higher levels of Cr, Zn, As, Ag, Cd and Pb compared with the main lake site. The mean levels of Cr, Cu, Zn, Ag and Pb exceeded probable effect levels at least at one of the gulf sites. The sediments at the Kisumu City site were classified as severely polluted with Cu (up to 259 mg/kg dw) and Pb (up to 1188 mg/kg dw). The sediment cores showed significantly higher levels of Cu, Zn, Ag, Cd and Pb in the surface (0–3 cm) versus subsurface (22–25 cm) layer at the Kisumu City site, indicating increasing pollution by these elements within the last 15 years. This is also the first report on trace elements in the emergent water plant Vossia cuspidata and submerged plant Ceratophyllum demersum from this lake. Even though the accumulation of most elements is comparable between C. demersum (whole plant) and V. cuspidata roots, the latter shows a better bioindicative potential. Contamination of the gulf with Ni, Cu, Zn, Ag, Cd and Pb is well mirrored in V. cuspidata roots. V. cuspidata strongly restricts the acropetal transport of trace elements, and hence using the shoots as fodder does not pose a risk to livestock.

Size-fractionated chlorophyll a and phycocyanin temporal variations in a highly eutrophic lake and its isolated karstic springs

Monthly variations of size-fractionated chlorophyll a and phycocyanin were studied in Lake Pamvotis between August 2016 and January 2017. Sampling was conducted at two sampling sites: in the main lake (Site 1: Lake) and in an adjacent man-made water ski lake with karstic springs (Site 2: Springs). Samples were fractionated into three size classes: 0.2–2 μm (pico), 2–20 μm (nano) and 20–180 μm (micro). According to chlorophyll a values, eutrophic to hypereutrophic conditions prevail at Site 1 and oligotrophic to mesotrophic conditions – at Site 2. Similarly, Site 1 was distinguished by higher concentration of phycocyanin compared to Site 2. Fractionated chlorophyll a showed monthly variations at Site 1 with alternations in the dominance between the two larger fractions. The maximum of the 0.2–2 μm fraction was observed in October but it contributed less to the total chlorophyll a content than nano- or microphytoplankton. Its contribution was higher at Site 2, reaching occasionally ~ 40% of the bulk chlorophyll a. However, nanophytoplankton was the fraction found to respond faster when disturbances occurred. At Site 1, phycocyanin correlated well with total chlorophyll a as well as with the micro- and nanophytoplankton fractions, indicating that cyanobacteria represent an important component of the large-sized phytoplankton in Lake Pamvotis.

How To Discriminate Athalassic and Marginal Marine Microfaunas: Foraminifera and Other Fossils from an Early Holocene Continental Lake in Northern Saudi Arabia

The occurrence of athalassic foraminiferal species, along with the brackish-water ostracod Cyprideis torosa, the barnacle Amphibalanus amphitrite, and brackish-water gastropods, prove the existence of a saline lake at Tayma, northern Saudi Arabia, during the early to mid-Holocene. Outcrops at the former shoreline, as well as a single sediment core, allow a reconstruction of the history of the main lake phase. Whereas these outcrops contain masses of calcareous micro- and macrofossils, the core from the modern sabkha does not. Four foraminiferal species were identified: Ammonia tepida is dominant, Quinqueloculina seminula is common, Flintinoides labiosa and Discorinopsis aguayoi are rare. Sieve-pore analysis and shell chemistry of C. torosa, as well as varying but generally high proportions of test anomalies (up to 50%) in foraminifers, indicate fluctuating, mostly hypersaline lacustrine conditions. We suggest, based on these results and on a literature overview on the worldwide distribution of Quaternary athalassic foraminifer taxa, that a combination of low diversity, exclusively marginal marine taxa, combined with occurrences of test anomalies >10% can be used to recognize athalassic saline waters in the fossil record.

Importance of Canals for Florida Largemouth Bass: Lake Griffin, Florida

Canal systems are commonly found across the country and are rarely constructed to increase fish habitat or angling opportunities. From 2009 to 2011, we assessed the benefits of canals to the fishery at Lake Griffin, Florida, by measuring and comparing the Florida Largemouth Bass Micropterus salmoides floridanus population and angler use to the main lake. We used electrofishing, angler creel surveys, and a high-reward tagging study. Results from electrofishing surveys revealed a high relative abundance of Florida Largemouth Bass in the canals, with similar electrofishing catch rates and size structure to those in the main lake. The canal creel showed that anglers used canals throughout the study, with peak use during the spawning season. The tagging study revealed anglers caught Florida Largemouth Bass in canals throughout the 12-mo study and that Florida Largemouth Bass migrated between the lake and canals. We conclude that the canals support a significant portion of the overall angler effort for the Lake Griffin fishery. Failing to consider the canals at Lake Griffin results in substantial underestimates of fish populations, angler use, and the fishery's economic impact. Our data suggest, however, that monitoring only the lake section still may represent trends occurring throughout the entire body of water, resulting in lowering sampling time and financial requirements. Fishery managers can identify any impacts canal systems or other lake sections may have to the fishery by including additional sections of a body of water into their sampling protocol.