Uptake of phosphate and inorganic nitrogen by a sediment-algal system in a subarctic lake

SUMMARY.

• 1 The uptake of phosphate and inorganic nitrogen by sediment and phytoplankton was studied under natural conditions (1977) and during lake fertilization with phosphorus and nitrogen (1978–79) in Lake Gunillajaure, a small, stratified, subarctic lake in northern Sweden. The experiments were performed in situ in plexiglass cylinders, to which additions of nutrients were made, and the uptake followed by consecutive sampling and analysis of the water phase.
• 2 Additions of HgCl₂ to the experimental vessels reduced the phosphate uptake to the sediment to less than 10% and it could therefore be concluded that the sediment uptake was mainly of biological nature.
• 3 Dark assimilation was 30–40% of that in light. Since light clearly stimulated the sediment uptake the epipelic algae were probably responsible.
• 4 The phosphate uptake to the sediment could be described by Michaelis-Menten kinetics and the calculated constants (V_max, ks) were very alike in 1977 and 1978 but appeared to have increased in 1979.
• 5 The sediment uptake of ammonium and nitrate was very slow indrcating that the epipelic algae were not nitrogen starved.
• 6 Even though the epipelic algae had a potential for efficient uptake of phosphorus, the phytoplankton took up 92–96% of the phosphate added to the lake on each fertilization occasion due to the relatively large water volume in the epilimnion in relation to the bottom area available for the epipelic algae.

     

Changes in phosphorus and nitrogen cycling following food web manipulations in a shallow Dutch lake

1. The flow of phosphorus and nitrogen through the food web of the shallow, eutrophic lake Wolderwijd was analysed for 2 different years before and for 1 year after food web manipulation.
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column.     

Changes in phosphorus and nitrogen cycling following food web manipulations in a shallow Dutch lake

1. The flow of phosphorus and nitrogen through the food web of the shallow, eutrophic lake Wolderwijd was analysed for 2 different years before and for 1 year after food web manipulation.
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column.     

Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment

1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes.     

Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment

1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes.     

The nature of a shield lake sediment

The nature of the sediment of Drinking Lake in the Churchill River Basin in Canada was studied with special reference to its chemical and colloidal composition. Crystalline minerals present in the colloidal fractions of the sediment are quartz, cristobalite, feldspars, micas, amphiboles, vermiculite, chlorite and kaolinite. Sesquioxidic components and the extractable Ca and Mg are present not only in the colloidal fractions but also in the non-colloidal fractions of the sediment. Over 99% of the nitrogen in the sediment is organic and about 60% of the sediment phosphorus is inorganic. The importance of the crystalline and non-crystalline mineral components of the sediment studied in the exchange of nutrients between the sediment and its overlying water is discussed. In view of the important roles of these mineral components in affecting the transfer of nutrients, possible significant modifications of the quality of the lake water after impoundment, if a dam were constructed in the basin for a hydro-electric development, deserve close attention.     

Effects of nutrients and grazers on periphyton phosphorus in lake enclosures

SUMMARY. 1. Periphyton. measured as particulate phosphorus (PP) and expressed as periphyton PP, growing on vertically oriented substrata (polyvinyl impregnated nylon) under different nutrient loadings, light intensities (exposures), and grazer communities was examined in eight large enclosures (750 m3) where nutrients (N and P) and planktivorous fish (1+yellow perch) were added in a 2x2 factorial design.
2. During the first 3 weeks of the experiment (25 June to 15 July), there was a significantly higher accumulation of phosphorus into periphyton (periphyton PP) with fertilization, but fish addition had no effect. During the fourth to seventh weeks (16 July to 12 August), addition of fish was associated with lower abundance of amphipods and chironomids and higher concentration of periphyton PP. In the enclosures without fish, these invertebrates were over 25 times more abundant, and periphyton PP decreased substantially compared to the June-July period. Fertilization increased periphyton PP only at high exposures in the enclosures with fish.
3. Exposure had a significant effect on periphyton PP. In the enclosures with fish, high abundance of nanoplankton reduced water transparency, and periphyton PP was lower in the deeper waters which may have been due to limitation by low light. Lower periphyton PP was also observed at the surface on sunny sides of enclosures without fish, and therefore with high water transparency. This pattern may have been due to inhibitory effects of high light intensity.
4. Periphyton communities in the enclosures with fish had higher uptake rates for planktonic phosphorus, and lower rates of phosphorus release, suggesting that periphyton with high phosphorus demand may have high internal cycling of assimilated phosphorus.     

Does sediment resuspension have persistent effects on phytoplankton? Experimental studies in three shallow lakes

1. The persistence of effects of sediment resuspension on chlorophyll a , phytoplankton production and plant nutrients was examined by artificially resuspending sediment in enclosures in three shallow lakes and monitoring concentrations for 4–8 days. Realism was assessed by relating initial suspended solids concentrations to those observed during natural wind events.
2. Positive effects on the phytoplankton, persisting for at least 4–6 days were detected in eight of the nine experiments, and similar effects on nutrient concentrations were also common, although suspended solids had normally returned to control levels within 24 h
3. The phytoplankton during the periods of persistence was normally dominated by planktonic rather than benthic/meroplanktonic genera.
4. Several of the positive responses appeared to be associated with relief of nitrogen deficiency in the algae.
5. Persistent effects from previous resuspension events may cause baseline concentrations of phytoplankton and nutrients in shallow lakes to be overestimated and the effects of resuspension on phytoplankton and nutrients to be underestimated     

Sedimentation in a large lake: the importance of fluctuations in water level

1. A sediment trap study was conducted in the central basin of Lower Lough Erne, Northern Ireland.
2. The material caught was low in organic matter, ash weight was 77% of dry weight on average.
3. Mass deposition of material was shown to be correlated with lake water level. When lake water level fell or rose above the middle range, the amount of material caught by the trap increased markedly. The effect was exaggerated by an unusually dry summer in 1995 which caused abnormally low water levels in the lake.
4. Comparison of Erne data with Windermere shows similar deposition rate of many substances, but the deposition rate of iron is thirteen times higher in Erne than in Windermere, and iron made up 39% of the ash weight in the Erne trap data.
5. Only 17% of the silica removed from the water column during diatom growth was recovered in the trap over the same time period.
6. Trap data are compared with historical data for sediment deposition and the implications of sediment focusing are discussed.     

Nutrient availability and the carnivorous habit in Utricularia vulgaris

1. Carnivory in plants is thought to enhance growth through an increased supply of nutrients, although there are considerable costs involved. It has been assumed that the relative investment of biomass in traps is inversely proportional to the availability of nutrients from non-carnivorous sources. Our aim was to test the effect of increasing nutrient concentration on investment in carnivory by Utricularia vulgaris .
2. Plants were grown under controlled conditions and nitrogen and phosphorus added at three loadings in a crossed design. Investment in carnivory was assessed as the proportion of (i) leaf biomass and (ii) leaf area comprising traps.
3. There was no effect of nutrient additions on plant growth or periphyton abundance. Investment in carnivory declined with increasing phosphorus loading. There was no effect of nitrogen, despite this being the nutrient commonly thought to be sought by carnivorous plants. Analysis of previously published data also indicated a decline in investment with increasing P availability.
4. Investment in carnivory in U. vulgaris is inversely proportional to the availability of phosphorus from non-carnivorous sources.     

The relative importance of shading and nutrients on algal production in subtropical streams

1. We used artificial substrata in forested and open streams in South-East Queensland, Australia, to determine the relative importance of shading from riparian vegetation and of nutrients on periphyton growth, and whether nitrogen and/or phosphorus limited algal productivity.
2. Nutrient-diffusing substrata consisting of agar enriched with N, P and N + P, and controls without nutrients, were deployed in duplicate at 15 sites in headwater streams with riparian canopy cover ranging from 0 to 88%.
3. Shading was the over-riding factor controlling periphyton biomass accrual on the artificial substrata, with nutrients playing a relatively minor role. Microscopic examination of periphyton scrapings taken after 7 weeks revealed that diatoms dominated on the artificial substrata in shaded streams, whereas filamentous green algae dominated the algal assemblage in the more open canopy streams.
4. Whilst nutrients had little effect on the accrual of algal biomass compared with riparian shading, there was evidence that nitrogen, and not phosphorus, stimulated periphyton production in streams with sufficient light.     

Hypolimnetic phosphorus and nitrogen dynamics in a small,eutrophic lake with a seasonally anoxic hypolimnion

In situ estimates of sediment nutrient flux are necessary to understand seasonal variations in internal loading in lakes. We investigated the sources and sinks of nutrients in the hypolimnion of a small (0.33 km²), relatively shallow (18 m max. depth), eutrophic lake (Lake Okaro, New Zealand) in order to determine changes in sediment nutrient fluxes resulting from a whole lake sediment capping trial using a modified zeolite phosphorus inactivation agent (Z2G1). Sediment nutrient fluxes in the hypolimnion were estimated as the residual term in a nutrient budget model that accounted for mineralisation of organic nutrients, nutrient uptake by phytoplankton and mixing, nitrification, adsorption/desorption and diffusion of dissolved nutrients at the thermocline. Of the total hypolimnetic phosphate and ammonium fluxes during one period of seasonal stratification (2007–08), up to 60 and 50%, respectively, were derived from the bottom sediments, 18 and 24% were due to mineralisation of organic species, 36 and 28% were due to phytoplankton uptake and 9 and 6% were from diffusion across the thermocline. Adsorption/desorption of phosphate to suspended solids and nitrification were of minor (<8%) importance to the total fluxes. Any reduction in sediment nutrient release by Z2G1 was small compared with both the total sediment nutrient flux and the sum of other hypolimnetic fluxes. Uneven sediment coverage of Z2G1 may have been responsible for the limited effect of the sediment capping layer formed by Z2G1.     

The effect of nutrient addition on the phytoplankton community of an oligotrophic lake

This investigation was performed during a 5-yr period (1974–1978) in the oligotrophic Lake Langvatn, Central Norway. In 1975 and 1976 the lake was enriched with a commercial fertilizer, In 1975 increase in phytoplankton biomass was first recorded more than three weeks after the fertilization started, despite a near fivefold increase in the primary production after fertilizer application. The mean seasonal biomass increased from c. 3500 mg wet weight m⁻² in 1974 to 4400 mg in 1975. In 1976 the biomass increased to near 9600 mg ⁻² and the seasonal primary production to 49.0 g C m⁻² (22.2 g C in 1975), despite a reduction in the nutrients added. Chrysophytes constituted the largest share of the seasonal algal biomass in all years, but in fertilization periods cryptophytes dominated in 1975 and diatoms, chlorophytes and cryptophytes in 1976. The highest biomass turnover rate was recorded during a period of cryptophyte dominance. The different biomass and production development in the fertilization years may be explained by a change in the consumer level.     

水氮运筹对棉花花后生物量和氮素利用率的影响

在池栽和大田条件下,以‘美棉33B’为材料,研究不同水分(自然降水、自然降水 灌水)和氮素(0、240、480kgN/hm2)运筹下棉花花后生物量和养分累积及氮素利用率动态变化特征。结果表明:施氮使棉花(整株、营养器官、生殖器官)生物量和养分快速累积期持续时间缩短、最大累积速率增大且出现时间提前、累积量及皮棉产量增加。灌水使240 kgN/hm2处理棉花(整株、营养器官、生殖器官)生物量和养分快速累积期持续时间缩短、最大累积速率出现时间提前、最大累积速率和累积量增大、氮素累积利用率和产量提高;而使480 kgN/hm2处理棉花营养器官生物量和养分快速累积期持续时间延长、最大累积速率出现时间推迟、生物量和养分最大累积速率及累积量增大、氮素累积利用率提高,而生殖器官相应指标呈降低趋势;灌水对不施氮处理棉花生物量和养分累积各项特征参数影响较小。营养器官生物量和氮磷钾最大累积速率出现时间较生殖器官早23 d左右,而快速累积期持续时间长于生殖器官11 d左右。研究发现,水分和氮素运筹可通过影响棉花生物量和养分累积的动态特征参数来影响棉花生长,进而影响最终产量品质形成;在本实验条件下,以灌水的240 kgN/hm2处理棉花的生长特征参数最为协调,皮棉产量和氮素利用率最高,品质较优。     

Does low nutritional quality act as a plant defence? An experimental test of the slow‐growth,high‐mortality hypothesis

Abstract.  1. The slow-growth, high-mortality hypothesis was experimentally tested in this study by investigating the effects of plant quality and natural enemies on leaf-miner growth, performance, and survivorship. Two leaf miners ( Acrocercops albinatella and Brachys tesselatus ) occurring on the turkey oak Quercus laevis were studied using a factorial design that manipulated predation/parasitism pressure and plant nutritional quality.
2. Forty trees were randomly divided into four treatments: (1) control plants (nutrients and natural enemies unaltered); (2) nutrients added, natural enemies unaltered; (3) nutrients unaltered, natural enemies reduced; and (4) nutrients added and natural enemies reduced. Water content, leaf toughness, tannin concentration, and foliar nitrogen were quantified monthly for each plant, and mine growth and survivorship were assessed by tracing mines on a 2–3-day interval and by following the fates of 50 mines per species per treatment combination.
3. Fertilised plants exhibited significantly higher amounts of nitrogen, but no significant differences among treatments were observed for water content, leaf toughness, and tannin concentration. These results only partially support the slow-growth, high-mortality hypothesis, as mines were significantly smaller and developed faster on fertilised plants, but neither fertilisation nor natural enemy exclusion significantly affected mine survivorship or mortality caused by natural enemies.     

Occurrence of phosphorus and its potential remohilization in the littoral sediments of a productive English lake

SUMMARY. 1. Vertical profiles of pH were measured at nine shallow water (<5m) locations in Esthwaite Water. These indicate strong gradients of pH near the sediment water interface suggesting a marked buffering capacity of the sediments.
2. Thirteen littoral sediment cores were horizontally sectioned and sequentially extracted (0.5 M NaHCO₃, 0.1 M NaOH, 1 M HCI) and analysed for soluble reactive phosphorus. The core sections were also analysed for total phosphorus and per cent organic content to determine the vertical and areal variability of phosphorus within the littoral sediments of Esthwaite Water.
3. The rate of release of phosphorus from intact sediment cores was measured in the laboratory as a function of the pH of overlying water, yielding the relationship log K=0.54 pH−3.94, K=mg Pm⁻²day⁻¹. The maximum release rate measured was 75 mg P m⁻² day⁻² at pH = 10.5.
4. Experiments on sediment slurries indicate that the release of phosphorus at pH 10 is rapid with approximately 50% of the total NaHCO₃+ NaOH extractable phosphorus being released within 3 h.
5. Phosphorus release from the littoral sediments may equal or exceed external sources plus hypolimnetic inputs during periods of high pH associated with times of maximum algal biomass.     

Wastewater treatment at the Houghton lake wetland: Soils and sediments

This paper describes the sediment and soils responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation (1978–2007), during which large changes in the wetland soils occurred. An average of 600,000 m³ y⁻¹ of treated water was discharged each warm season to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen. Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 t) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. Peat probings, water level increases and topographical surveys established quantitative measures of soil accretion. Over 30 cm of new soil developed, in which nutrient storage occurred. Phosphorus concentrations in the new soil were approximately 2000 mg P/kg, and the nitrogen concentration was 2–3%DW. The removal of TSS was effective, but minor in comparison to the internal generation and cycling of produced particulates. Later in the project history, the interior portion of impacted area became a floating mat. Sedimentation processes then occurred with no exposure to above-mat detrital processes. Trace element analyses showed no appreciable accumulation of heavy metals, other than the calcium and iron that characterized the antecedent wetland and the incoming water. Biomass cycling models were found to produce reasonable estimates of the measured nutrient accumulations. The light loadings of nutrients to this system produced dramatic effects in the ecosystem, but were lower than the range seen in some other treatment wetlands. Insufficient nitrogen was added to support the new biomass, and nitrogen fixation was identified as a possible compensatory mechanism.     

东海赤潮高发区沉积物中营养盐再生速率的研究

2001年5月和2002年5月在东海赤潮高发区的4个站位(E4、E5、DB6、DCl0)对沉积物表面分别充氮气和空气进行培养,研究沉积物．水界面营养盐交换通量在不同条件下的变化规律,以及该海域沉积物中营养盐的再生对水体中营养盐的贡献．结果表明,各溶解态营养盐在还原条件下的迁移较为活跃．在距离陆地较近的海域,营养盐一般由水向沉积物中扩散,且距陆地越近,交换通量越大;而在上升流区,营养盐多由沉积物中向水中扩散．东海赤潮高发区沉积物是SiO3^2-的源,对初级生产力的贡献占6％．同时,东海赤潮高发区沉积物是氮、磷营养盐蓄积库．该海域沉积物每年从水体中吸附的DIN、PO4^3-分别占长江输入的5．9％、67％,沉积物一水界面对水体中SiO3^2-的贡献占7．8％．       

Tissue nutrient concentrations in freshwater aquatic macrophytes: high inter-taxon differences and low phenotypic response to nutrient supply

1. The elemental composition and stoichiometry of aquatic plants has often been suggested to reflect the nutrient enrichment of aquatic habitats. However, the relationship is often weak. Moreover, uncertainties remain in the relevance of laboratory derived critical plant tissue nutrient concentrations to maximum yield or growth rates in the field.
2. Aquatic vascular plants and bryophytes, overlying water and sediment samples were collected to test whether freshwater aquatic macrophytes: (i) show tissue nutrient deficiencies when growing in oligotrophic freshwater habitats, and (ii) have strict homeostatic stoichiometry.
3. Plant nutrient concentrations were significantly related to total inorganic nitrogen (or nitrate), total dissolved phosphorus and sediment total phosphorus. However, these relationships were weak. Virtually all the variance in plant tissue nutrient concentrations, however, could be explained by species (taxon) identity.
4. Critical tissue nutrient concentrations for 95% maximum yield or 95% maximum growth rate in aquatic angiosperms, determined from laboratory bioassays, suggested that nutrients should not limit yield in wild aquatic macrophytes. However, there were a substantial number of samples where potential growth rate limitation was possible, particularly due to phosphorus.
5. Strict C : N : P stoichiometric ratios were found for both vascular plants and bryophytes, suggesting little scope for plants as indicators of nutrient enrichment, but provide robust stoichiometric data for studies on ecosystem metabolism and nutrient cycling.     

Resistance and tolerance to herbivory in Salix cordata are affected by different environmental factors

Abstract.  1. Effects of sand burial and nutrients on the ability of sand-dune willow ( Salix cordata ) to tolerate or resist herbivory by the beetle Altica subplicata were evaluated in field experiments.
2. To assess tolerance, all combinations of sand burial (none, 50%), nutrients (presence, absence), and beetles (presence, absence) were applied to caged plants and growth responses to herbivory were measured. Sand burial increased plant growth rate, but decreased S. cordata 's tolerance to herbivory. Although nutrients increased growth, tolerance to herbivory was unaffected.
3. To assess resistance, plants were exposed to all combinations of sand burial and nutrients, and then to natural beetle colonisation. The presence of nutrients, but not sand burial, significantly increased the percentage of plants with beetles, for both adults and larvae. This decreased resistance to beetles of plants grown with added nutrients occurred only in the absence of sand burial.
4. The performance and preference of beetles were examined in laboratory experiments. Larvae developed faster and had increased pupation success on plants with nutrients added. Beetles also showed a marginally significant feeding preference for leaves grown with added nutrients. Thus, S. cordata tolerance to herbivory was affected by sand burial, whereas resistance, preference, and performance were affected by nutrient level.