The significance of alkaline phosphatase activity in Lough Neagh

SUMMARY. A study of the eutrophic Lough Neagh was undertaken to ascertain the use of alkaline phosphatase activity as an indicator of phosphorus-limited algal growth. Lough Neagh and its surrounding rivers were monitored during 1974 and 1975. Alkaline phosphatase activity increased in the lough when the algal crop increased and depleted orthophosphate to a growth-limiting concentration. Enzyme activity was appreciable, however, at all other times of the year and may on occasions have been associated with zooplankton. The enzyme activity in the inflowing rivers was much greater than in the lough itself. Depending on enzyme stability the enzyme inputs from rivers could contribute significantly to the lough activity. Sewage disposal works effluent appeared to be a major source of enzyme activity in river water. As the alkaline phosphate activity in Lough Neagh resulted from several sources, increased activity could not be used as a reliable indicator of phosphorus limited algal growth.     

The effect of bacteria on the solubilization of silica in diatom frustules

P atrick , S heila & H olding , A.J. 1985. The effect of bacteria on the solubilization of silica in diatom frustules. Journal of Applied Bacteriology 59 , 7–16.
Natural bacterial populations in samples of water from Loch Leven and Lough Neagh increased the rate of solubilization of frustule silica from an axenic Cyclotella meneghiniana culture, compared with sterile autolysis, at 25C. In the inoculated cultures 50–60% of the silica was solubilized over a period of 30 d. Bacterial populations in Loch Leven water also enhanced the solubilization of silica from non-axenic cultures of Asterionella formosa, Tabellaria flocculosa, Navicula pellicu-losa and C. meneghiniana , compared with control cultures sterilized with mercuric chloride. Similar results were obtained with Lough Neagh populations incubated with A. formosa . In comparison with untreated cells, the treatment of diatom cells with ultra-sonication did not increase the release of silica. Pure cultures of bacteria from Loch Leven water enhanced the release of silica from non-axenic A. formosa and axenic C. meneghiniana compared with sterile control treatments. The variation in the ability of cultures to solubilize the frustule silica appeared to be related to their potential to produce hydrolytic enzymes. Natural populations of Loch Leven and Lough Neagh water bacteria and certain bacterial cultures caused the diatoms to aggregate, which did not enhance the release of silica.     

Metagenomic Characterisation of the Viral Community of Lough Neagh,the Largest Freshwater Lake in Ireland

Lough Neagh is the largest and the most economically important lake in Ireland. It is also one of the most nutrient rich amongst the world’s major lakes. In this study, 16S rRNA analysis of total metagenomic DNA from the water column of Lough Neagh has revealed a high proportion of Cyanobacteria and low levels of Actinobacteria, Acidobacteria, Chloroflexi, and Firmicutes. The planktonic virome of Lough Neagh has been sequenced and 2,298,791 2×300 bp Illumina reads analysed. Comparison with previously characterised lakes demonstrates that the Lough Neagh viral community has the highest level of sequence diversity. Only about 15% of reads had homologs in the RefSeq database and tailed bacteriophages (Caudovirales) were identified as a major grouping. Within the Caudovirales, the Podoviridae and Siphoviridae were the two most dominant families (34.3% and 32.8% of the reads with sequence homology to the RefSeq database), while ssDNA bacteriophages constituted less than 1% of the virome. Putative cyanophages were found to be abundant. 66,450 viral contigs were assembled with the largest one being 58,805 bp; its existence, and that of another 34,467 bp contig, in the water column was confirmed. Analysis of the contigs confirmed the high abundance of cyanophages in the water column.     

A Long Term Study of the Phosphorus Cycle in Lough Neagh,Northern Ireland

Eleven years of weekly observations on the phosphorus cycle in Lough Neagh are analysed. The data comprised inputs, outputs and lake concentrations of the soluble and particulate phosphorus fractions. It is shown that the particulate phosphorus input quickly sediments to the bottom and the particulate phosphorus in the lake is largely made up of phytoplankton. The average phosphorus retention in the lake was 34 %, similar to the particulate phosphorus input. Climate has a big influence on the phosphorus input and sediment release, both of which varied two-fold. A simulation model suggested that suppression of sediment P release would reduce lake winter phosphorus concentrations by an average of 29 %.     

Preliminary results on phosphorus reduction in Lough Neagh - Assessing the effect against a background of change

Lough Neagh is a large (387 km²), shallow (mean depth 8.9 m) eutrophic lake. The phosphorus budget is described in order to illustrate that 75% of the particulate phosphorus input sediments to the bottom and that there is little retention of SRP in the lake. 54% of the SRP loading comes from sewage works and this is being reduced by phosphorus reduction at the major sewage works. There has been a downturn in the maximum algal crops, particularly of blue-green algae. However, there is an underlying upward trend in SRP loading and the paper stresses the importance of analysing trends in nutrient budgets to get an accurate evaluation of reduction strategies.     

不同形态的磷源对球形棕囊藻生长及碱性磷酸酶的影响

研究了不同浓度和形态的无机磷(DIP)和有机磷(DOP)对球形棕囊藻细胞生长、培养基中磷浓度的变化以及碱性磷酸酶活性的变化的影响。在缺磷和大分子DOP(卵磷脂)作为磷源的情况下,碱性磷酸酶活性迅速提高,在第9天达到了最大值,其活性分别为19.11U和18.28U,显然在缺磷胁迫下和大分子DOP的利用过程中碱性磷酸酶起着重要作用。DIP(磷酸二氢钾)和小分子DOP(β-甘油磷酸钠)都容易直接被球形棕囊藻吸收利用,碱性磷酸酶活性变化不明显。     

Aulacoseira subarctica: taxonomy,physiology, ecology and palaeoecology

Knowledge of the morphology, taxonomy, physiology, ecology and palaeoecology of the filamentous freshwater diatom Aulacoseira subarctica (O. Müller) Haworth is reviewed from the literature. The species is widely distributed across Northern Europe, Scandinavia and North America, Japan, China, Australia and New Zealand, in the last usually as fo. subborealis. The species is rare in the Tropics and positive identifications are lacking for Africa. The importance of correct identification is stressed because literature reports of its occurrence often need revision. A comparison is made between two sites with detailed records of its seasonal cycle. Blelham Tarn, England, is a clear-water seasonally stratified lake; Lough Neagh, Northern Ireland, is a very large turbid and unstratified lake. In spite of their contrasting characters, Aulacoseira subarctica succeeds in both lakes. In Blelham Tarn, there is a strong seasonal cycle of growth, dormancy on the sediment and further growth on re-suspension. In Lough Neagh, there is a large deposition of cells at the end of the spring bloom but few of these cells survive grazing by benthic animals. Fossil occurrences are summarized from the species’ initial appearance in the Pliocene and its later occurrence during the last inter-glacial (Eemian) deposits in NW Europe, where it is an important ecological indicator. Palaeolimnological studies are reviewed to describe the contemporary distribution and ecological preference of this widespread diatom. Aulacoseira subarctica usually appears in response to moderate increases in nutrients but is disadvantaged by further enrichment. In Blelham Tarn the species only became abundant during the twentieth century, reaching a peak between 1930 and 1960. With nutrient enrichment, abundance has declined. In Lough Neagh, it has been present for much of the post-glacial period and still thrives today in spite of the highly enriched state of the lake. The species has disappeared from many eutrophic lakes and its sustained existence in Lough Neagh is anomalous. Lough Neagh may continue to offer a favourable habitat in spite of the poor light climate because the water depth, lack of stratification and long water retention time reduce losses to a sustainable level.     

Dynamics of water-extractable phosphorus during the degradation of Microcystis aeruginosa by four bacteria species

We carried out a laboratory experiment for studying the dynamics of water-extractable phosphorus release during the decomposition of dead Microcystis aeruginosa driven by the four bacteria strains. Our results showed that water-extractable phosphorus had significant correlation to alkaline phosphatase but without obvious correlation to acid phosphatase, suggesting that alkaline phosphatase was the primary enzyme decomposing organic phosphorus. Also, water-extractable phosphorus exhibited an obvious correlation to pH, indicating that the alkaline environment contributed to the release of water-extractable phosphorus. The quantity of bacteria hardly correlated to the release of water-extractable phosphorus for all species. This could result from decrease of bacterial quantity after consumption of substrate in closed system. Obvious variation in water-extractable phosphorus was observed across the strains in two water treatments. Sporolactobacillus sp. and Bacillus macerans had the strongest ability for decomposing organic phosphorus among five strain treatments in the lake water. In the distilled water, Bacillus sp. had the strongest ability to degrade organic phosphorus. In both water treatments, mixed species exhibited intermediate ability for decomposing organic phosphorus. It was true that water quality strongly affected the release of phosphorus by regulating phosphatase activity.     

Phosphatases; origin,characteristics and function in lakes

Phosphatases catalyze the liberation of orthophosphate from organic phosphorus compounds. The total phosphatase activity in lake water results from a mixture of phosphatases localized on the cell surfaces of algae and bacteria and from dissolved enzymes supplied by autolysis or excretion from algae, bacteria and zooplankton. External lake water phosphatases usually have pH optima in the alkaline region. Acid phosphatases generally seem to be active in the internal cell metabolism. The synthesis of external alkaline phosphatases is often repressed at high phosphate concentrations and derepressed at low phosphate concentrations. Phosphatase activity has therefore been used as a phosphorus deficiency indicator in algae and in natural plankton populations. The possibilities for this interpretation of phosphatase activity in lake water are limited, however, and this is discussed. The in situ hydrolysis capacity, i.e. the rate by which orthophosphate is released from natural substrates, is unknown. However, we advocate that this process is important and that the rate of substrate supply, rather than phosphatase activity, limits the enzymatic phosphate regeneration.     

The planktonic and benthic bacterial populations of Lough Neagh

The planktonic and benthic bacterial populations of Lough Neagh, Northern Ireland, were studied over a one-year period. Direct counts of bacteria in the water column averaged 6 times 10⁷/ml with limited spatial or temporal variation; viable counts, however, showed a pronounced late spring maximum of 1.7 times 10⁶/ml and were consistently higher at a littoral sampling station. Direct counts of bacteria in the profundal sediments averaged 8 times 10⁹/ml whilst viable benthic counts rose steeply during spring to reach a June maximum of 1 times 10⁸/ml. Direct: viable count ratios were much greater in the more sandy littoral zone. The predominant benthic isolate was an Aeromonas sp. which was also common in samples from the water column. These results confirm the eutrophic status of Lough Neagh indicated by other biological and chemical surveys.     

Characterization of orthophosphate release from dissolved organic phosphorus by gel filtration and several hydrolytic enzymes

The molecular weight distribution of dissolved organic phosphorus (DOP) and the possible mechanisms of orthophosphate (Pi) release were examined by gel filtration and incubation with some hydrolytic enzymes. Sixty five percent of the DOP appeared to have apparent molecular weights between 300 to 10000 daltons. Less than 10% of the DOP estimated higher molecules greater than 10000 daltons. Alkaline phosphatase released Pi more easily from low molecular weight (< 1500 daltons) DOP than from high molecular weight fractions. While, addition of nucleases or phosphodiesterase alone did not appear Pi release from high molecular weight DOP compounds. Pi release from those DOP compounds increased markedly (more than 30%) when alkaline phosphatase was incubated with nucleases or phosphodiesterase. However, 60% of DOP did not release Pi when alkaline phosphatase was incubated with either enzymes.     

Effects of Nutrients on Specific Growth Rate of Bacterioplankton in Oligotrophic Lake Water Cultures

The effects of organic and inorganic nutrient additions on the specific growth rates of bacterioplankton in oligotrophic lake water cultures were investigated. Lake water was first passed through 0.8-μm-pore-size filters (prescreening) to remove bacterivores and to minimize confounding effects of algae. Specific growth rates were calculated from changes in both bacterial cell numbers and biovolumes over 36 h. Gross specific growth rates in unmanipulated control samples were estimated through separate measurements of grazing losses by use of penicillin. The addition of mixed organic substrates alone to prescreened water did not significantly increase bacterioplankton specific growth rates. The addition of inorganic phosphorus alone significantly increased one or both specific growth rates in three of four experiments, and one experiment showed a secondary stimulation by organic substrates. The stimulatory effects of phosphorus addition were greatest concurrently with the highest alkaline phosphatase activity in the lake water. Because bacteria have been shown to dominate inorganic phosphorus uptake in other P-deficient systems, the demonstration that phosphorus, rather than organic carbon, can limit bacterioplankton growth suggests direct competition between phytoplankton and bacterioplankton for inorganic phosphorus.     

Changes in phytoplankton physiology and morphology in response to dissolved nutrients in Lough Neagh, N. Ireland

SUMMARY. Cell phosphorus and anthrone-reactive carbohydrate contents were measured over a 6-month period in the phytoplankton of Lough Neagh, N. Ireland. When all the soluble reactive phosphorus had disappeared from the water column, cell phosphorus contents began to decrease, reaching a minimum value of 0.4% ash-free dry weight. At this time, cell carbohydrate contents greatly increased and phosphorus sorption assays showed rapid uptake of orthophosphate. Following a presumed sediment phosphorus release, cell carbohydrate and phosphorus uptake rate decreased greatly and there was a subsequent increase in cell phosphorus content to 1.6% ash-free dry weight. As the cell phosphorus content declined, blue-green algal filaments became progressively shorter. On the basis of these responses it is likely that phosphorus limitation occurred over a 4-week period.     

Predicting the spring algal biomass in Lough Neagh using time series analysis

1. Lough Neagh is a large eutrophic lake covering 387 km² with a mean depth of 8.9 m. It is an important natural resource, being the largest single source of potable water for Belfast, Northern Ireland. 2. This report examines the causes of the year-to-year variation in the April–June (spring) algal biomass, measured as chlorophyll a, for the period 1974–92. 3. The spring chlorophyll a declined following the introduction of a phosphorus (P) reduction programme at major sewage treatment works in 1981. However, since 1990 the chlorophyll a concentrations in the spring have increased. 4. Time series methodology was employed to develop a model which explained 76% of the annual variation in spring chlorophyll a concentrations. 5. The independent variables used in the multiple regression model were the previous year’s spring chlorophyll a concentration, soluble reactive P inputs for April–June and the particulate P concentration in the Lough during the previous summer.     

A simple method for fitting Bělehrádek's equation to embryonic development data of zooplankton

A method is described whereby a Bělehrádek function is fitted to experimentally derived data for embryonic development duration at a range of temperatures. The method is applied to data for the freshwater copepods Cyclops abyssorum and Eudiaptomus gracilis from Lough Neagh, Northern Ireland. Differences in duration of embryonic development of Lough Neagh populations and that of previously published data for these species are discussed.     

The past and future of phytoplankton in the UK's largest lake,Lough Neagh

Lough Neagh is the largest lake in the UK and has been extensively monitored since 1974. It has suffered from considerable eutrophication and toxic algal blooms. The lake continues to endure many of the symptoms of nutrient enrichment despite improvements in nutrient management throughout the catchment, in particular a permanently dominant crop of the cyanobacterium Planktothrix agardhii. This study examines the historical changes in the Lough, and uses the PROTECH lake model to predict how the phytoplankton community may adapt in response to potential future changes in air temperature and nutrient load. PROTECH was calibrated against 2008 observations, with a restriction on the maximum simulated mixed depth to reflect the shallow nature of the lake and the addition of sediment released phosphorus throughout the mixed water column between 1 May and 1 October (with an equivalent in-lake concentration of 2.0 mg m⁻³). The historical analysis showed that phytoplankton biomass (total chlorophyll a) experienced a steady decline since the mid-1990s. During the same period the key nutrients for phytoplankton growth in the lake have shown contrasting trends, with increases in phosphorus concentrations and declines in nitrate concentrations. The modelled future scenarios which simulated a temperature increase of up to 3 °C showed a continuation of those trends, i.e. total chlorophyll a and nitrate concentrations declined in the surface water, while phosphorus concentrations increased and P. agardhii dominated. However, scenarios which simulated a 4 °C increase in air temperature showed a switch in dominance to the cyanobacteria, Dolichospermum spp. (formerly Anabaena spp.). This change was caused by a temperature related increase in growth driving nutrient consumption to a point where nitrate was limiting, allowing the nitrogen-fixing Dolichospermum spp. to gain sufficient advantage. These results suggest that in the long term, one nuisance cyanobacteria bloom may only be replaced by another unless the in-lake phosphorus concentration can be greatly reduced.     

Phosphorus enhancement of mineralization of low concentrations of p-nitrophenol by Flavobacterium sp. in lake water

Abstract A study was conducted to determine whether the supply of inorganic phosphorus in lake water was sufficient for the mineralization of p -nitrophenol (PNP) by a Flavobacterium sp. The bacterium grew following its inoculation into sterile lake water amended with only 20 or 200 ng PNP per ml, but depending on when the water sample was taken, either PNP was not mineralized or it was mineralized slowly. PNP at both concentrations was rapidly mineralized if 10 mM P was added. The degradation of 200 ng PNP per ml was most rapid if the lake water was amended with 10 mM P, it proceeded more slowly with 1 mM P and the initiation of mineralization was delayed to equal extents if the sterile water received 0.1 mM, 0.01 mM or no P. The possible significance of these findings to biodegradation in natural waters is discussed.     

A comparison of chlorophyll a and carotenoid concentrations as indicators of algal volume

SUMMARY. 1. Carotenoid concentration, as measured hy absorbance at 480 nm. was a better indicator of algal volume than chlorophyll a when the results from two lakes and laboratory studies on Osciltaloria agardhii var. isothrix Skuja were compared. The correlation between algal volume and carotenoid in White Lough ( r =0.91) was significantly higher (0.001 P <0.01) than ihat between algal volume and chlorophyll a (r=0.77). The Lotigh Neagh correlation coefficient lor algal volume with carotenoid (r=0.89) was only marginally stronger than that with chlorophyll a (r=0.87).
2. The relatively weak correlation between algal volume and chlorophyll a in White Lough was a result of a summer decline in the chlorophyll a content of O. agardhii var. isothrix , which dominated the phytoplankton. The chlorophyll a content of the phytoplankton was depressed by high summer daily totals ol light hours received by the phytoplankton in White Lough of up to 14 h in comparison to a maximum value of 3.8 h in Lough Neagh. where no seasonal cycle of chlorophyll a content was evident.
3. Laboratory studies demonstrated that while chlorophyll a per unit algal volume of O. agardhii var. isothri.x declined with increasing light dose, carotenoid content did not. Nitrogen and phosphorus limitation depressed the carotenoid content but to a lesser degree than was observed for chlorophyll a.     

River lamprey present an unusual predation threat to Atlantic salmon smolts in Lough Neagh,Northern Ireland

A new monitoring programme on the Lough Neagh catchment has documented a high incidence of river lamprey, Lampetra fluviatilis L., predation on Atlantic salmon smolts, Salmo salar L. In total 470 smolts were examined during the 2020 emigration period with 168 fish (36%) exhibiting lamprey scars of which 57 were lightly scarred and 111 were classed as heavily scarred. Lamprey predation was not size selective on Lough Neagh S. salar smolts.     

UV-sensitive P compounds: release mechanism, seasonal fluctuation and inhibitory effects on alkaline phosphatase activity in a shallow Chinese freshwater lake (Donghu Lake)

Filtrable phosphorus compounds in a shallow Chinese freshwater lake (Donghu Lake) were fractionated by Sephadex G-25 gel-filtration chromatography. Some portions of those compounds released soluble reactive phosphorus upon irradiation with low dose ultraviolet light. Catalase and a hydroxyl radical scavenger (mannitol) markedly prevented photosensitive phosphorus release. The observed effects may be explained by the action of oxidizing reagents such as hydroxyl radicals, produced in photochemical reactions between UV irradiation and humic substances in the water. There was a strong seasonality in UV-sensitive P (UVSP) release. Michaels constants (K _m) of total alkaline phosphatase in the lake water showed a direct positive relation to UVSP Plot of K _m against the UVSP/phosphomonoester ratio reveals a strong relationship between the two variables. These results suggest that in some situations UVSP may be a competitive inhibitor of alkaline phosphatase activity in the lake. The competitive inhibition of fractionated UVSP on alkaline phosphatase reagent (Sigma) apparently supports this hypothesis.