Limnetic Water Research Articles

Seasonal Dynamics of Lake Winnipeg's Microbial Communities Reveal Aerobic Anoxygenic Phototrophic Populations Coincide with Sunlight Availability.

In this first comprehensive study of Lake Winnipeg’s microbial communities, limnetic and littoral euphotic zones were examined during each season from 2016 through 2020. Classical cultivation and modern high-throughput sequencing techniques provided quantification and identification of key phototrophic populations, including aerobic anoxygenic phototrophs (AAP). Annual dynamics found total heterotrophs reached 4.23 × 106 CFU/g in littoral sands, and 7.69 × 104 CFU/mL in summer littoral waters on oligotrophic media, higher counts than for copiotrophic compositions. Limnetic numbers inversely dipped to 4.34 × 103 CFU/mL midsummer. Cultured AAP did not follow heterotrophic trends, instead peaking during the spring in both littoral and limnetic waters as 19.1 and 4.7% of total copiotrophs, or 3.9 and 4.9% of oligotrophs, decreasing till autumn each year. Complementary observations came from environmental 16S V4 rRNA gene analysis, as AAP made up 1.49 and 1.02% of the littoral and limnetic sequenced communities in the spring, declining with seasonal progression. Spatial and temporal fluctuations of microbes compared to environmental factors exposed photosynthetic populations to independently and regularly fluctuate in the ecosystem. Oxygenic phototrophic numbers expectantly matched the midsummer peak of Chl a and b, oxygenic photosynthesis related carbon fixation, and water temperature. Independently, AAP particularly colonized spring littoral areas more than limnetic, and directly corresponded to habitat conditions that specifically promoted growth: the requirement of light and organic material.

Quadricoccopsis gen. nov., a new genus of Quadricoccus-like algae in Oocystaceae from China (Trebouxiophyceae, Chlorophyta)

Members of Quadricoccus-like algae are characterized by oval to ellipsoid cells adherent to the bowl-shaped or stretched, empty mother cell walls and are common in phytoplankton of inland waters. To date, the morphologically similar genera Quadricoccus and Lobocystis are accepted for this group and the former had been phylogenetic positioned in Oocystaceae. In this study, seven strains of Quadricoccus-like algae were identified and successfully cultured in the laboratory. Light and electron microscope observations and phylogenetic analysis revealed that the strains represent three different species within a new genus, described here as Quadricoccopsis gen. nov. It differed from genus Quadricoccus by characteristically cell adherent mode that two pairs of daughter cells connected to the mother cell remnant respectively by the pole and median portion and distinguished from Lobocystis by variable 2-4-8 autospores, characteristically cell adherent mode and only found in limnetic water. The three new species, described here as Q. simplex, Q. parva and Q. glomerata, differed in cell size, colony morphology and autospore number. Phylogenetic analysis revealed the genus Quadricoccopsis in Oocystaceae and a close relationship with Oocystidium, which is far away from the phylogenetic position of Quadricoccus in one of the granulated clades. The Quadricoccus-like algae were, therefore, proved to be a paraphyly. Furthermore, apart from Planctonema-like algae, the Oocystaceae characteristic cell wall ultrastructure, which is multi-layered with cellulose fibrils in each layer perpendicular to those of the adjoining layer, is not shown again in genus Quadricoccopsis. Different cell wall substructures may be related to the colony formation mechanism. Whether the ultrastructure criterion is applied to all the Oocystaceae needs to be re-evaluated and, further, the definition of this family should be discussed.

Новый подход к организации сети станций для мониторинга озёрных водоёмов Бурятии по организмам макрозообентоса: первые результаты применения и анализ пространственного распределения амфипод в озёрах Еравнинской системы как пример его реализации

Новый подход к организации сети станций для мониторинга озёрных водоёмов Бурятии по организмам макрозообентоса: первые результаты применения и анализ пространственного распределения амфипод в озёрах Еравнинской системы как пример его реализации

Effects of phytoplankton extracts containing the toxin microcystin-LR on the survival and reproduction of cladocerans.

The use of ecotoxicological techniques for the evaluation of the quality of limnetic waters allows the early detection of toxic agents that pose risks to human health. In this study Moina micrura (two clones), Daphnia laevis (two clones) and Daphnia similis, a temperate species, were used to evaluate the toxicity of six Microcystis extracts from two Colombian reservoirs. Toxin was detected and quantified by HPLC. Microcystin-LR was found in all extracts with the highest concentrations in one sample from each reservoir (434μgg(-1) and 538μgg(-1)). The extracts that had the highest toxin concentration also had the highest toxicities to cladocerans. Measurement of 48-h LC50 showed consistent differences between cladoceran species but not clones, Also, reproduction data in two species were consistent with the MC-LR content of one sample tested, with decreased reproduction and disruption of egg production. However, only some growth results of neonates exposed to extracts were consistent with the acute response. In conclusion, Daphnia species are a good model for monitoring cyanotoxins as they respond in a sensitive way to natural phytoplankton samples containing microcystin-LR.

Diel patterns of temperature, conductivity and dissolved oxygen in an Amazon floodplain lake: description of a friagem phenomenon

AIM: The aim of this work was to study the diel stratification parameters temperature, dissolved oxygen and conductivity, providing a more detailed description of a friagem event. METHODS: the mixing behavior of the limnetic water column in Lago Catalão, an Amazon floodplain lake flooded by two of the world’s largest rivers (Solimões and Negro), was studied through diel profiling of temperature, conductivity and dissolved oxygen, between 2006 and 2007. Measurements were made every four hours at 1m depth intervals to the lake bottom. RESULTS: The water column remained stratified during most of the year with the exception of one month with low water level, when nocturnal mixing occurred and one friagem event during high water (May 2007) when an isothermal temperature profile and an atypical orthograde oxygen profile were observed. CONCLUSIONS: The friagem event, a large drop in air temperatures due to the intrusion of a polar air mass in the Amazon, constitutes an important force in the dynamics of the water column, which produces a profound redistribution of dissolved gases and solutes in the system. This is the first time that the effects of the friagem on the mixing patterns in a lowland Amazon lake have been documented in detail. The decline in air temperature, observed during the friagem event destabilized the normally stratified water column, which can be associated with an environmental disturb.

An overview of the limnetic Cyclopidae (Crustacea, Copepoda) of the Philippines, with emphasis on Mesocyclops

Approximately 120 (sub)species of Cyclopidae have been reported from South and Southeast (SE) Asia, where the Philippine archipelago – with 16 (including two endemic) taxa – is one of the least explored parts of the region. Our study, part of current efforts to assess freshwater biodiversity, was undertaken to update the diversity and geographic distribution of the cyclopid copepods living in the limnetic zone of the freshwater lakes in the Philippines. Examination of the samples from 22 lakes in five islands (Luzon, Mindoro, Cebu, Leyte and Mindanao) revealed a novel species from lake Siloton (Mindanao), Mesocyclops augusti n. sp. The new species can be distinguished from the congeners by the surface ornamentation of the hindgut, among others. The same character state was found in a Mesocyclops from North Vietnam, which is provisionally identified as M. augusti n. sp., though the Vietnam and Mindanao specimens differ in a few (yet polymorphic in the close relatives) characters. Mesocyclops microlasius Kiefer, 1981 endemic to the Philippines is redescribed, based on females and males from lake Paoay (North Luzon). Sister relationships of M. augusti n. sp. and M. microlasius were tested in a phylogenetic analysis that included the closely related Old World representatives of the genus. The max. parsimony trees show M. dissimilis Defaye et Kawabata, 1993 (East Asia) as the closest relative of M. augusti n. sp. (Mindanao, Vietnam), and support sister relationship between M. geminus Holynska, 2000 (East Borneo) and M. microlasius (Luzon, Mindanao). A mainland clade (M. francisci, M. parentium, M. woutersi, M. dissimilis, M. augusti) appears in most reconstructions; all members of the clade occur in continental Asia though some species also live in islands that have never been connected to the SE Asian shelf. In most trees with the mainland clade the insular taxa (M. microlasius, M. geminus, M. friendorum) form either a paraphyletic (basal to mainland) or monophyletic sister group of the mainland clade. We also established the first records of Thermocyclops taihokuensis (Harada, 1931) in the Philippines (Luzon), so far known from East and Central Asia. In all, 11 taxa [Mesocyclops (4), Thermocyclops (4), Microcyclops (1), Tropocyclops (1) and Paracyclops (1)] including only one endemic species (M. microlasius) have so far been found in the limnetic waters. We expect significantly higher diversity and higher rate of endemism of the freshwater cyclopids in the littoral (paludal) and subterranean habitats in the Philippines.

Octadecyltrimethoxysilane functionalized ZnO nanorods as a novel coating for solid-phase microextraction with strong hydrophobic surface

In this paper, we have, for the first time, proposed an approach by combining self-assembled monolayers (SAMs) and nanomaterials (NMs) for the preparation of novel solid-phase microextraction (SPME) coatings. The self-assembly of octadecyltrimethoxysilane (OTMS) on the surface of ZnO nanorods (ZNRs) was selected as a model system to demonstrate the feasibility of this approach. The functionalization of OTMS on the surface of ZNRs was characterized and confirmed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The OTMS-ZNRs coated fiber exhibited stronger hydrophobicity after functionalization, and its extraction efficiency for non-polar benzene homologues was increased by a factor of 1.5-3.6 when compared to a ZNRs fiber with almost identical thickness and façade. In contrast, the extraction efficiency of the OTMS-ZNRs coated fiber for polar aldehydes was 1.6-4.0-fold lower than that of the ZNRs coated fiber, further indicating its enhanced surface hydrophobicity. The OTMS-ZNRs coated fiber revealed a much higher capacity upon increasing the OTMS layer thickness to 5 μm, leading to a factor of 12.0-13.4 and 1.8-2.5 increase in extraction efficiency for the benzene homologues relative to a ZNRs coated fiber and a commercial PDMS fiber, respectively. The developed HS-SPME-GC method using the OTMS-ZNRs coated fiber was successfully applied to the determination of the benzene homologues in limnetic water samples with recovery ranging from 83 to 113% and relative standard deviations (RSDs) of less than 8%.

Responses of antioxidant enzymes, lipid peroxidation, and Na+/K+-ATPase in liver of the fish Goodea atripinnis exposed to Lake Yuriria water

Lake Yuriria, located in the heavily populated and polluted Mexican Central Plateau, receives domestic sewage, industrial effluents, and municipal wastewaters that are still directly discharged without treatment into the tributaries and the lake. Pollutants in water and sediments include heavy metals, aromatic hydrocarbons, and organochlorine pesticides. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), as well as Na⁺/K⁺-adenosine triphosphatase (Na⁺/K⁺-ATPase) activity, and lipid peroxidation (LPO) were evaluated in the livers of the fish Goodea atripinnis after 96 h of exposure to water collected in March and June 2005 from three sites: Y (limnetic zone), L (Lerma tributary), and C (la Cinta tributary). Physical and chemical parameters of the lake water were also analyzed. Increases in CAT activity and LPO levels at all three sites were detected compared with control fish (P < 0.05), while GPx and SOD activities decreased significantly (P < 0.05). Na⁺/K⁺-ATPase activities were similar to the control in fish exposed to limnetic water from both March and June but were higher than control at the two tributary sites in March (P < 0.05); fish exposed to water from the Lerma tributary in June exhibited lower Na⁺/K⁺-ATPase than the control (P < 0.05). During March, CAT and Na⁺/K⁺-ATPase activities were increasing more than in June in Y and L, respectively, while in June, SOD and GPx were depleted more than March in L and Y and L, respectively. Despite the antioxidant defenses of the fish liver, exposure to all water samples from Lake Yuriria exerted alterations in hepatic LPO levels, antioxidant enzymes, and Na⁺/K⁺-ATPase activities that could substantially impair the mechanisms of fish defenses against oxidative stress.

New Chorological Data of Some Submerged Macrophytes in Bulgaria

ABSTRACTThe data on the distribution of some submerged macrophytes from different types of limnetic water bodies from the ecoregions of Bulgaria were summarized. New chorological data for 11 species were found: Ceratophyllum demersum, Ceratophyllum submersum, Elodea canadensis, Hydrocharis morsus-ranae, Myriophyllum spicatum, Najas marina, Nymphaea alba, Potamogeton gramineus, Potamogeton pectinatus, Potamogeton pusillus, Trapa natans. The distribution of Potamogeton berchtoldii Fieb. has been confirmed for the territory of Bulgaria.

Axial Zonation Patterns of Subtidal Macrozoobenthos in the Gamtoos Estuary, South Africa

The distribution of macroinfauna was quantified in subtidal, soft-bottom habitats, extending from the estuarine mouth to the tidal head of the Gamtoos—a small, shallow, temperate estuary situated on the south coast of South Africa. Sampling covered the full salinity gradient from fresh to marine waters, and all sediment types from marine sands to fluvial silts. A total of 35 taxa was recorded, of which 22 occurred throughout the year. Species richness and diversity declined from the seawater-dominated mouth region toward the fresh water section at the tidal head of the estuary. Sediment type generally bore no clear relation to biotic diversity. A marked drop in salinity between winter and summer sample series (Δ 0.2‰ to 24‰) coincided with a reduction of mean macrofaunal density by 70%, a more seaward relocation, and a compression of axial ranges of most taxa. Numerical classification and ordination of faunistically similar regions and of co-occurring species delineated four habitat zones along the longitudinal axis of the estuary which harbour four distinct macrofaunal assemblages: 1) A tidal inlet area with salinities close to seawater; clean, coarse, marine sands, rich in CaCO3 harbour a stenohaline fauna normally found on adjacent, marine sandy beaches. 2) In the lower reaches, where fine, fluvial silts of high organic content prevail, euryhaline polychaetes dominate the macrozoobenthic community; bottom salinities in this zone seldom dropped below 25‰ 3) The middle reaches, characterized by oligohaline- to polyhaline waters, stretch over sandy sediments of intermediate carbonate, silt, and organic fractions; the fauna comprises typical estuarine forms, which occurred throughout most of the estuary except at its seaward and landward limits. 4) The upper reaches encompass the limnetic waters near the tidal head of the estuary with sediments in this zone being composed mostly of coarse, clean sands, low in CaCO3; the macrobenthos in this region is dominated by taxa of freshwater origin, which generally do not penetrate seaward beyond the oligohaline waters, and by exceptionally euryhaline estuarine species. Salinity appears as the main factor in controlling faunal assemblages at both extremes of the estuarine gradient (i.e., tidal inlet and head), whereas sediment type delineates between communities in the mesohaline to polyhaline reaches. Axial (i.e., from tidal inlet to tidal head of the estuary) zonation patterns of macroinfauna broadly matched those of mesozooplankton and fishes, supporting the notion of a general structure underlying species distribution patterns in the Gamtoos estuary.

Origin and trophic importance of detritus-evidence from stable isotopes in the benthos of a small, temperate estuary.

Ratios of 13C/12C and 15N/14N were measured in dissolved inorganic carbon (DIC), marginal vegetation, benthic macrodetritus (diameter > 1 mm) and selected invertebrate consumers in the Gamtoos estuary, South Africa to: (1) trace the provenance of benthic detrital deposits, and (2) determine the extent to which three abundant species of macroinvertebrates utilise this resource. DIC was strongly depleted in 13C with average δ13C values (-9.5±0.5‰) being typical of limnetic waters. Benthic detrital particles (δ13C-24.1±0.3‰) originated mainly from marginal vegetation (δ13C-25.7±0.3‰), but their slightly elevated carbon ratio suggests additional input from 13C-rich sources-possibly C4 plants cultivated on the floodplain. Populations of the fossorial ghost shrimp Callianassa kraussi, the bentho-pelagic amphipod Grandidierella lignorum and the epifaunal crab Hymenosoma robiculare together account for 96% of total benthic biomass in the upper regions of this estuary. Marked differences in trophic niches were evident among these three consumer species. Ghost shrimp (δ13C -32.5±0.3‰) foraged by filter-feeding on fine suspended particulate organic matter (δ13C-31.2±0.5‰). Amphipods (δ13C-28.0±0.6‰) utilised some benthic detritus but fed mainly on suspended material. Only the relatively rare crabs (δ13C-23.8±1.5‰) appeared to utilise benthic detrital particles to any significant extent. In the benthic consumer community of the upper Gamtoos estuary, suspension feeders make up 98% of biomass and thus clearly dominate over deposit feeders. This can be traced to the low contribution of higher plants (c. 13%) to overall carbon production, and detritus originating from macrophytes is consequently relatively unimportant in supporting invertebrate secondary production in this particular system.

Use of the thermotolerant Aeromonas group for the trophic state classification of freshwaters

Data obtained from 68 lakes surveyed in the United States showed a highly significant correlation between the densities of a specific group of autochthonous, heterotrophic bacteria, thermotolerant aeromonads and the trophic state of fresh waters. This measurement provides a sensitive, accurate and facile descriptor of limnetic water quality and shows strong correlations with certain other commonly employed physical, chemical and biological parameters used in this regard. The best correlations were obtained with Secchi depth ( r = −0.70 ), total phosphorus ( r = 0.72 ) and chlorophyll α ( r = 0.67 ). An even stronger correlation was obtained with a trophic index derived from these three parameters ( r = −0.84 ). Alternatively, total heterotrophic bacterial populations, as enumerated by epifluorescence microscopy, were very poorly correlated with all the individual trophic state measurements, and the indices derived from them. An analysis of correlation coefficients for trophic state parameters and indices used for this study indicated that the level of thermotolerant aeromonads was one of the most discriminating single parameters for defining trophic state. The economy of the measurement, coupled with its facility, makes it an exceptionally promising technique for assessing the degree and rate of fresh water eutrophication.

Effect of microhabitat on fitness components of larval tiger salamanders, Ambystoma tigrinum nebulosum.

Survivorship and growth of larval tiger salamanders, Ambystoma tigrinum nebulosum, in the White Mountains of east-central Arizona were compared in six microhabitats using field enclosures during summers, 1983-85. Microhabitats were vegetated and nonvegetated shallows, surface, middle, and bottom horizontal layers of limnetic areas, and the vertical limnetic water column. Initial enclosure densities (0.025 larvae per 1) were identical among microhabitats. Three enclosures were placed in each microhabitat in two ponds. Larval survivorship and growth were usually greatest in vegetated shallows in lowest in middle and bottom limnetic enclosures, despite several population dieoffs. Lower fitness, as reflected in survivorship and growth, in these latter enclosures was correlated with lower food levels, temperatures, and oxygen concentrations in deeper limnetic areas. Relative fitness varied greatly between years while food levels, temperatures, and oxygen concentrations within microhabitats remained relatively constant indicating additional factors affected fitness. Disparities in fitness between microhabitats apparently affect habitat use patterns of larvae.

Growth characteristics of Aeromonas hydrophila in limnetic waters of varying trophic state

Growth characteristics of Aeromonas hydrophila in limnetic waters of varying trophic state

PHOTOINHIBITION: ALGAL RESPONSES TO BRIGHT LIGHT DURING DIEL STRATIFICATION AND MIXING IN A TROPICAL ALPINE LAKE1

ABSTRACTNear surface thermoclines form each day in the limnetic waters of Lake Titicaca (Peru‐Bolivia) and thereby retain phytoplankton under extreme irradiances. This bright light exposure results in strongly depressed chlorophyll fluorescence and photosynthesis which both decay (bright light) and recover (dim light) by first order rate kinetics. During each afternoon the phytoplankton are redistributed by wind‐induced mixing, and full recovery is accomplished soon after nightfall. In vivo fluorescence was measured over this diet cycle both with (Fb) and without (Fa 3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea. Strongest bright light effects were on the parameter (Fa– Fa), a crude measure of operational photosystem II reaction centers (RC IIs). On dates of strong thermocline development, surface (FFa– Fa) was reduced to 5% or less of that for the mixed layer maximum. Fluorescence depression was greater in the lake than in Pyrex bottles incubated at fixed depths for 4 h. Ultraviolet light intensified the photoinhibitory response, but strong (Fb– Fa) depression could be induced by photosynthetically available radiation alone. In Lake Titicaca, photoinhibition apparently operates by reversible in‐activation of RC IIs. It occurs in the natural water column and is not simply an artifact affixed bottle incubations.

Structure and dynamics of zooplankton communities in the littoral zone of some North Carolina lakes

Species composition and seasonal, dynamics of zooplankton in the littoral zone were studied in three piedmont North Carolina lakes for one year. Nygaard's compound index indicated oligotrophic conditions in Belews Lake and eutrophic conditions in Salem Lake and Lake 150. A total of 32 species of zooplankton were found in the samples. Significantly fewer species of truely littoral zooplankton were present in the oligotrophic lake regardless of season (P < 0.05). Eutrophication appears to favor increased diversity in zooplankton of the littoral zone. Habitat heterogeneity, provided by a well developed littoral zone containing aquatic macrophytes, may be the major factor contributing to the maintenance of more taxa of zooplankton in eutrophic systems. Distinct taxa of Cladocera and Copepoda are present in the littoral zone, exhibiting seasonal dynamics that are largely different from the limnetic fauna. Such dynamics may result from predation by characteristically limnetic species of cyclopoid copepods which seek prey in the littoral zone. The numerical and seasonal abundance of predators and prey are inversely related and the true littoral taxa, represented in the present study by the genera Alona, Chydorus, Pleuroxus, Sida, Simocephalus, and Eucyclops, contained no predaceous species. The seasonal dynamics of these genera are very similar even in widely separated geographical regions, indicating that the factor(s) responsible operate independently of climatic and chemical variables. Intrazooplankton predation appears to be a more plausable explanation than segregation along depth which, although consistent with data from studies of limnetic waters, cannot be related to populations of zooplankton in shallow littoral areas.

Annotated Checklist of the Free-Living Copepods of the Great Lakes

An annotated checklist of the free-living copepods of the Laurentian Great Lakes is developed on the basis of published records. Synonymies are included for each species, relating, wherever possible, invalid names in the literature with currently recognized taxonomy. Twelve species of calanoids, six species of planktonic cyclopoids, nine species of benthic/ littoral cyclopoids, and fourteen species of harpacticoids have been reported from the Great Lakes. Ten of the calanoids and four of the cyclopoids are characteristic of limnetic waters. Three calanoids and two planktonic cyclopoids have been reported infrequently and are perhaps accidental occurrences. The composition of the planktonic copepod fauna in most subregions of the Great Lakes is well-known. In contrast, the sampling of benthic/littoral cyclopoids and harpacticoids has been so infrequent that their kinds, areas of occurrence, and relative abundances are still poorly understood.

USE OF MODIFIED DIURNAL CURVES FOR THE MEASUREMENT OF METABOLISM IN STANDING WATER.

A modification of diurnal oxygen curves is described, whereby community metabolism can be easily estimated from a succession of twice‐nightly points. The method can be adapted to stratified limnetic waters by using suitable sampling techniques. Results of a study using the method are given for a small, fertile Georgia farm pond. Gross photosynthesis averaged 6.0 g O2 m−2 day−1, ranging from 1.0 to 14 g O2 m−2 day−1. The approximate net loss of oxygen due to diffusion was 101.1 g O2 m−2 yr−1, less than 5% of total gross photosynthesis.