Primary productivity and trophic status of a Kashmir Himalayan Lake

The paper deals with general limnology, phytoplankton production and trophic status of a Himalayan lake of Kashmir. The primary production as measured by in situ ¹⁴C istope technique ranged from 36 to 906 mgC.m^–2 d^–1 with characteristic seasonal variation. The photosynthetic efficiency was from 0.02 to 0.48% during the same period. The yearly (1975–1976) production was estimated at 134 gC.m^–2 m^–2, which shows that the lake has not yet reached a high level of eutrophication. The waterbody has been classified as mesotrophic.Formed part of thesis for which Ph. D. was awarded to MAK by Kashmir University, India     

On the trophic status and conservation of Kashmir Lakes

The lakes of the Kashmir Valley are generally shallow and situated in the flood plain of the river Jhelum. Thermal stratification is fairly uncommon, and stable stratification occurs in deeper lakes (12 metres, Manasbal lake). The waters are mostly low in dissolved solids, medium hard and slight to highly alkaline.The eutrophic typology of the lakes has been developed by using various physico-chemical and biological parameters. Greater habitational influence and tourist traffic seems to be a major factor contributing towards higher trophic levels of these lakes. Certain methods for conservation of these lakes have been suggested.Cold Water Fisheries Research Unit of the Central Inland Fisheries Research Institute (I.C.A.R.), Harwan-Kashmir, India     

The effect of diatom populations on silica concentrations of Lakes Sorell and Crescent,Tasmania, and the utilisation of tripton as a source of silica

Lakes Sorell and Crescent are very alike in most physico-chemical features but differ markedly in silica concentrations. The small diatom crops of Sorell have little effect on silica levels which average 12·2 mg l^-1 but in Crescent large crops of Diatoma and Synedra maintain low silica concentrations and often cause complete depletion. Silica is supplied to Crescent from Sorell but derivation of a budget is complicated by artificial regulation of Crescent inflow and outflow and lack of sufficient hydrological data. Cultural studies show that silica may frequently limit the Crescent diatom population and that, at least when dissolved silica is scarce, the diatoms may utilise the abundant triptonic silica of the lake.     

Epiphytic,littoral diatoms as bioindicators of shallow lake trophic status: Trophic Diatom Index for Lakes (TDIL) developed in Hungary

Littoral diatoms are important contributors of the primary production in shallow aquatic ecosystems and they can be used as indicators of the trophic status. The aim of the study was to develop an index to assess trophic status of Hungarian lakes as suggested by the Water Framework Directive. In spring of 2005 and 2006, epiphytic diatom samples were collected from 83 shallow lakes. Weighted average method was used to develop and test the TP model. In the developed TP model correlation between the observed and diatom inferred TP was high (r ² = 0.96, n = 67). The optimum and tolerance TP parametrics of 127 species were determined and trophic indicator and sensibility values were defined for the Trophic Diatom Index for Lakes (TDIL). The TDIL was applicable to assess the ecological status of Hungarian shallow lakes. According to the TDIL the ecological status of 4 lakes were in excellent, 25 in good, 21 in medium, 21 in tolerable and 12 in bad status. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: K. Martens     

A Comparative Study of Primary Production and Related Factors in Four Saline Lakes in Victoria,Australia

The purpose of the study was to compare the primary plankton productivities of lakes of different salinities and to determine the causative factors involved in their production rates. Four lakes (specific conductivity —mS cm⁻¹ at 18°C) were initially chosen: Coragulac (9), Red Rock (25), Corangamite (38), Pink (250). Sampling and production measurements were made every two to three weeks. Three lakes were dominated by specific phytoplankton blooms: Red Rock (Anabaena spiroides), Corangamite (Nodularia spumigena). Pink (Dunaliella salina). Coragulac Lake had more diverse populations. Red Rock Tarn had some of the highest production values ever recorded. Extremely high soluble phosphate and inorganic carbon concentrations were the most important causative factors. Pink Lake had very low production rates. High salinity and low nutrient concentrations were limiting factors. The other lakes were intermediate in production and nutrient levels. Zooplankton populations were also determined.     

Limnological characteristics of subtropical Lakes Phewa, Begnas, and Rupa in Pokhara Valley, Nepal

Limnological characteristics were studied and analyzed in the subtropical Lakes Phewa, Begnas, and Rupa of Pokhara Valley, Nepal, from 1993 to 1997. The annual water temperature ranged from 12° to 29°C in all lakes. Lake Phewa and Lake Begnas were monomictic and anoxic in the hypolimnion during thermal stratification from April to September. Dissolved oxygen was drastically depleted in April and/or May in shallow Lake Rupa when the macrophyte community began to decompose. NH₄ ⁺-N accumulated below 5 m during March–September when dissolved oxygen was depleted in Lakes Phewa and Begnas. The PC : PP ratio was higher, but the PC : PN and PN : PP ratios were close to the Redfield ratio (106C : 16N : 1P) in Lakes Phewa and Begnas, denoting that P was limited. Annual net primary production showed that the lakes were productive but will tend to become heterotrophic in the future. The seasonal variation of chlorophyll a concentration was high, but its annual variation was low. Ceratium hirundinella and Peridinium spp. in Lake Phewa, Microcystis aeruginosa and Aulacoseira granulata in Lake Begnas, and Tabellaria fenestra in Lake Rupa were the dominant species. The zooplankton population and species varied irregularly. On the basis of chlorophyll a concentration in the euphotic zone and phytoplankton species composition, the lakes seem to be oligoeutrophic and to have some characteristics of temperate lakes rather than tropical lakes. Received: April 26, 1999 / Accepted: September 20, 1999     

Iron Constraints on Planktonic Primary Production in Oligotrophic Lakes

Phototrophic primary production is a fundamental ecosystem process, and it is ultimately constrained by access to limiting nutrients. Whereas most research on nutrient limitation of lacustrine phytoplankton has focused on phosphorus (P) and nitrogen (N) limitation, there is growing evidence that iron (Fe) limitation may be more common than previously acknowledged. Here we show that P was the nutrient that stimulated phytoplankton primary production most strongly in seven out of nine bioassay experiments with natural lake water from oligotrophic clearwater lakes. However, Fe put constraints on phytoplankton production in eight lakes. In one of these lakes, Fe was the nutrient that stimulated primary production most, and concurrent P and Fe limitation was observed in seven lakes. The effect of Fe addition increased with decreasing lake water concentrations of total phosphorus and dissolved organic matter. Possible mechanisms are low import rates and low bioavailability of Fe in the absence of organic chelators. The experimental results were used to predict the relative strength of Fe, N, and P limitation in 659 oligotrophic clearwater lakes (with total phosphorus ≤ 0.2 μM P and total organic carbon < 6 mg C l⁻¹) from a national lake survey. Fe was predicted to have a positive effect in 88% of these lakes, and to be the nutrient with the strongest effect in 30% of the lakes. In conclusion, Fe, along with P and N, is an important factor constraining primary production in oligotrophic clearwater lakes, which is a common lake-type throughout the northern biomes. This paper is dedicated to the memory of Prof. Peter Blomqvist (deceased 2004).     

The sediment column as a record of trophic status: examples from Bosherston Lakes,SW Wales

Bosherston Lakes are a series of interconnected, mesotrophic to hypereutrophic, artificially-created coastal marl lakes in Dyfed, South West Wales. Progressive eutrophication of the lake system has been produced by a high external phosphorus loading which includes phosphorus-rich effluent from a sewage treatment works (STW) in the catchment of the Lakes.Cores were taken from four sites of varying eutrophic status within the Lakes. In the surface sediment layer, organic C, N and P concentrations generally correlate directly with trophic status and reflect distance from the source of P input. At one site, sediment stratigraphy records a clear transition at 20–15 cm depth, marked by a sharp upward increase in porosity, organic C, N, and P, and iron-associated-P; decreases in organic matter C/N, C/P and N/P ratios; a sharp decrease in carbonate, and a change in the subfossil diatom assemblage. Lead-210 dating indicates that this change occurred in the period 1919 to 1938.The diatom stratigraphy and sediment geochemistry suggest that this transition reflects an increase in trophic status at this site, probably as a result of the influx of nutrient-rich water. This took place when the management of the Stackpole estate surrounding the lake system, fell into decline during the period 1919–1938.     

Limnology and trophic status of glacial lakes in the tropical Andes (Cajas National Park,Ecuador)

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Seasonality in Nutrients and Phytoplankton Production in Two Shallow Lakes: Waigani Lake,Papua New Guinea,and Barton Broad,Norfolk, England

Waigani Lake, near Port Moresby, Papua New Guinea and Barton Broad, Norfolk, England are both shallow lakes nutrient-enriched from sewage effluent disposal. In Waigani Lake phytoplankton biomass varied seasonally with lower levels (100-200 mg chlorophyll α m⁻³) during the wet season increasing to over 400 mg chlorophyll α m⁻³ at the end of the dry season. Secchi disc depths varied between 0. 11 and 0. 34 m. Phytoplankton productivity in Waigani Lake was very high throughout the year (range: A_max 4,370-21,000 mg O₂ m⁻³ h⁻¹) but production was lower during the wet season (range: A_max 4,370-12,700 mg O₂ m⁻³ h⁻¹). High surface productivity was recorded from August to December except on sampling days when the weather was overcast. Productivity throughout the year declined rapidly with depth. Algal biomass in Barton Broad varied from 3-10 mg chlorophyll α m⁻³ in winter but increased in spring and was very high in summer (200-500 mg chlorophyll α m⁻³). Secchi disc depth varied from 0.21 m in August 1976 to 1.76 m in December. Phytoplankton production in Barton Broad was low in winter (range: A_max 247-1,250 mg O₂ m⁻³ h⁻¹) but increased markedly in spring and summer with the highest rate (A_max 6,850 mg O₂ m⁻³ h⁻¹) being recorded in August. Surface inhibition was observed during summer except when the weather was overcast. Seasonality in nutrients and phytoplankton in Waigani Lake appear to be related to rainfall. Nutrient concentrations in Barton Broad are more closely related to phytoplankton activity which, in turn, correlates with seasonality in solar radiation.     

Occurrence,Dynamics and Production of Picoplankton in Hungarian Shallow Lakes

Phototrophic picoplankton were detected in 10⁵-10⁶ cells/ml concentrations in seven water bodies of differing chemistry and trophic level. Dominant picoplankters were, at all sites, coccoid cyanobacteria of 0.8-1.2 μm dimensions, exhibiting red or yellow autofluorescence. Apart from the effects of water temperature their quantitative dynamics were significantly influenced by the nitrogen supply and the herbivorous zooplankton (Cladocera). Their maximum contribution to the total planktonic primary production was about 50%, both in mesotrophic and hypereutrophic environments. However during the bloom of filamentous nitrogen-fixing blue-greens their role became negligible. In phytoplankton communities the significance of picoplankton is overestimated several times, when based on the cell count, while it is underestimated on the basis of biomass. The most useful characteristics of phytoplankton size groups was the total surface area of their cells.     

Rotifer occurrence in relation to age,depth and trophic state of quarry lakes

An effect of age of quarry lakes on rotifer abundance and species composition has been evaluated. Rotifers occurred in all lakes under study. They were even found in the youngest (2 years of age) one, Rogonica 4, but both rotifer density and species richness were low there. Rotifer communities of much higher density and species diversity were noted in lakes only 4–6 years older. Lakes of over 30 years of age were strongly differentiated in rotifer numbers and species structure. In general, age of quarry lakes has an impact on rotifer communities only at the very beginning of the process of colonization. Several years later other factors become more important, e.g., depth or trophic state of the lakes.     

Aquatic ecosystem health and trophic status classification of the Bitter Lakes along the main connecting link between the Red Sea and the Mediterranean

The Bitter Lakes are the most significant water bodies of the Suez Canal, comprising 85% of the water volume, but spreading over only 24% of the length of the canal. The present study aims at investigation of the trophic status of the Bitter Lakes employing various trophic state indices, biotic and abiotic parameters, thus reporting the health of the Lake ecosystem according to the internationally accepted classification criteria’s. The composition and abundance of phytoplankton with a dominance of diatoms and a decreased population density of 4315–7376?ind. l^?1 reflect the oligotrophic nature of this water body. The intense growth of diatoms in the Bitter Lakes depends on silicate availability, in addition to nitrate and phosphate. If the trophic state index (TSI) is applied to the lakes under study it records that the Bitter Lakes have an index under 40. Moreover, in the total chlorophyll-a measurements of 0.35–0.96?µg?l^?1 there are more indicative of little algal biomass and lower biological productivity. At 0.76–2.3?µg?l^?1, meanwhile, the low quantity of Phosphorus is a further measure of low biological productivity. In the Bitter Lakes, TN/TP ratios are high and recorded 147.4, and 184.7 for minimum and maximum ratios, respectively. These values indicate that in Bitter lakes, the limiting nutrient is phosphorus and confirm the oligotrophic status of the Bitter Lakes. The latter conclusion is supported by Secchi disc water clarity measurements, showing that light can penetrate, and thus algae can photosynthesize, as deep as >13?m. This study, therefore, showed that the Bitter Lakes of the Suez Canal exhibit oligotrophic conditions with clear water, low productivity and with no algal blooming.     

An initial measurement of photosynthetic productivity in Lake Tanganyika

Measurements of ¹⁴C uptake and oxygen evolution by phytoplankton in Lake Tanganyika provide the first direct estimates of the lake's primary productivity. These measurements at the expected nadir of the annual range suggest that Lake Tanganyika is as productive as other large, deep tropical lakes.     

Planktonic indices in the evaluation of the ecological status and the trophic state of the longest lake in Poland

Due to the intensive mixing polymictic lakes should be homogenous. However, morphometric diversity and high water dynamics contribute to the differentiation of many parameters in various areas of the lakes. This study analyzes both phytoplankton and zooplankton to assess differences in water quality along the north–south axis of the longest lake in Poland. New phytoplankton indicators were applied for determining the lake's ecological status: the Q index based on functional groups and the PMPL (Phytoplankton Metric for Polish Lakes) index based on phytoplankton biomass. TSI_ROT index (Rotifer Trophic State Index), which comprises the percentage of species indicating a high trophic state in the indicatory group and the percentage of bacteriovorus in the Rotifera population, was used for zooplankton analysis.TP content was different at different sites – we observed its gradual increase from the south to the north. Spatial variation of phosphorus did not considerably affect plankton diversity. The phytoplankton was dominated by Oscillatoriales, typical of shallow, well-mixed eutrophic lakes. The ecological status of the lake based on the EQR (Ecological Quality Ratio) was poor or moderate. The zooplankton was dominated by rotifers (at almost all sites), which indicates a eutrophic state of the lake. The values of phytoplankton indices at the studied sites did not differ considerably; the differences resulted more from local conditions such as the contaminant inflow and the macrophyte development than water dynamics.We have demonstrated that in the lake dominated by filamentous Cyanobacteria the ecological status should be determined according to the PMPL index or other indices dependent on the dominant Cyanobacteria species. Since the Q index does not include the functional group S1, the results can lead to the false conclusion that water quality improves with an increased amount of phytoplankton. The high abundance of Cyanobacteria in the lake may have contributed to the poor growth of rotifers.     

湖北四湖泊营养类型与轮虫群落的关系

对湖北梁子湖水系不同营养类型(中营养型、富营养型)4个湖泊中轮虫的群落结构和物种多样性进行了周年研究,分析比较了不同营养类型湖泊的轮虫种类组成、分布、优势种组成、密度、生物量和多样性指数。结果表明：轮虫的种类数、物种多样性与营养水平呈负相关关系,轮虫密度大体上随营养水平提高而增大,富营养化引起轮虫空间异质性降低,受污染湖泊与非污染湖泊轮虫种类数、寡污性种类数及分布差异尤为明显。用多样性指数评价湖泊营养状态与TLIc方法一致。     

Driving forces shaping phytoplankton assemblages in two subtropical plateau lakes with contrasting trophic status

1. We studied driving forces shaping phytoplankton assemblages in two subtropical plateau lakes with contrasting trophic status, the oligotrophic deep Lake Fuxian and the eutrophic shallow Lake Xingyun. 2. Phytoplankton samples were taken monthly for a year and phytoplankton species were sorted into the main taxonomic groups and associations proposed by Reynolds. A canonical correspondence analysis (CCA) was used to test the occurrence of these classification schemes and to determine their discriminatory power. 3. The results suggest that the major driving forces in Lake Fuxian were physical variables, and particularly the underwater light climate, whereas, nutrients were the important driving force in Lake Xingyun. 4. Top–down control through zooplankton grazing in Lake Fuxian was hardly ever a significant determinant itself, because of the scarcity of zooplankton and their low grazing efficiency of predation while a dominance of inedible cyanobacteria throughout the year rendered top–down controls ineffective failing in Lake Xingyun. Hence phytoplankton communities in both lakes appear to be regulated primarily by bottom–up controls.     

Links between Terrestrial Primary Production and Bacterial Production and Respiration in Lakes in a Climate Gradient in Subarctic Sweden

We compared terrestrial net primary production (NPP) and terrestrial export of dissolved organic carbon (DOC) with lake water heterotrophic bacterial activity in 12 headwater lake catchments along an altitude gradient in subarctic Sweden. Modelled NPP declined strongly with altitude and annual air temperature decreases along the altitude gradient (6°C between the warmest and the coldest catchment). Estimated terrestrial DOC export to the lakes was closely correlated to NPP. Heterotrophic bacterial production (BP) and respiration (BR) were mainly based on terrestrial organic carbon and strongly correlated with the terrestrial DOC export. Excess respiration over PP of the pelagic system was similar to net emission of CO₂ in the lakes. BR and CO₂ emission made up considerably higher shares of the terrestrial DOC input in warm lakes than in cold lakes, implying that respiration and the degree of net heterotrophy in the lakes were dependant not only on terrestrial export of DOC, but also on characteristics in the lakes which changed along the gradient and affected the bacterial metabolization of allochthonous DOC. The study showed close links between terrestrial primary production, terrestrial DOC export and bacterial activity in lakes and how these relationships were dependant on air temperature. Increases in air temperature in high latitude unproductive systems might have considerable consequences for lake water productivity and release of CO₂ to the atmosphere, which are ultimately determined by terrestrial primary production.     

Synechococcus as an indicator of trophic status in the Cochin backwaters,west coast of India

Eutrophication is a major problem in coastal water bodies. Information about the trophic status of water bodies will enable proper management of coastal ecosystems. In this regard, biological organisms which are sensitive to environmental changes can serve as indicators of ecosystem trophic status. In this study, seasonal and spatial variations of picophytoplankton (PP; <3 μm size) community structure was assessed in the Cochin backwaters (CB) with respect to the prevailing environmental conditions during three seasons, post-monsoon (PM-I; October 2011 and PM-II; November 2012), pre-monsoon (PrM; May 2012) and monsoon (MON; August 2012). CB, along the west coast of India, receives continuous load of nutrients throughout the year through anthropogenic wastes. Trophic status index (TRIX) scores showed that CB is highly eutrophic with a high phytoplankton biomass. Synechococcus was the dominant PP observed in the study area. Seasonal and spatial salinity variations influenced the PP distribution, especially Synechococcus where PE-rich Synechococcus (SYN-PE) were dominant in higher saline (>30) and PC-rich Synechococcus (SYN-PC) in lower saline (<30) waters. SYN-PC showed a significant positive relation with chlorophyll a suggesting that this group contributes substantially to the total phytoplankton biomass. TRIX scores and SYN-PC: SYN-PE abundance ratio were negatively correlated with salinity suggesting an influence of the tidal amplitude. SYN-PC correlated positively and SYN-PE negatively with TRIX scores suggesting that these groups occupy contrasting ecological niches. These findings imply that PP distribution pattern can serve as an indicator of the trophic status of coastal water bodies.