The loss of submerged plants with eutrophication I. Experimental design, water chemistry, aquatic plant and phytoplankton biomass in experiments carried out in ponds in the Norfolk Broadland

SUMMARY. 1 During eutrophication of shallow lakes, communities of submerged plants are often replaced by dense phytoplankton populations, but the mechanism by which this occurs is obscure though often assumed to involve shading. 2. This paper introduces a series investigating this change and describes a system of experimental ponds which were variously fertilized with nitrogen and phosphorus, had fish added or removed, and had their submerged aquatic plants cleared or left intact. 3. Fertilization with phosphate and ammonium nitrate in quantities effectively greater than those in a series of lakes in the adjacent Norfolk Broads, which have lost their submerged plants, did not displace the plant populations. 4. Total phosphorus and soluble reactive phosphorus concentrations in the water did not increase much with increasing loading in the presence of submerged plants but did so if the plants were manually cleared. Ammonium and nitrate concentrations were kept low, despite large additions in both plant dominated and manually cleared ponds. 5. In the absence of fish there were modest increases in chlorophyll a concentrations with phosphorus loading in the presence or absence of submerged plants. The concentrations achieved, however, were much lower than anticipated probably because of grazing by large-bodied Cladocera. 6. Ponds dominated by plants continued to have low phytoplankton populations even when fish were stocked. Low fish survival in these ponds permitted grazing zooplankters to flourish. In ponds cleared of plants, however, there were significant relationships between cholorophyll a concentration with Daphnia biomass (inverse) and log stock of potentially zooplanktivorous fish (positive). There was a significant relationship between chlorophyll a and total phosphorus concentrations in the plant and cleared ponds in 1982 but only in the plant ponds in 1983. In all cases the phytoplankton communities were dominated by small, often flagellated, organisms.     

The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. II. Long-term trends in water chemistry and ecology and their implications for restoration of the lake

• 1 Hickling Broad underwent major changes from a clear water, charophyte-dominated state in the decades previous to 1970 to a turbid, phytoplankton-dominated state by the mid 1970s. These changes were complexly linked with increasing eutrophication by black-headed gulls and increased salinity due to agricultural changes in the catchment.
• 2 At the turn of the 1970s, the lake began to change again and during the 1980s a submerged plant community, of tall, vigorously growing species (e.g. Myriophyllum spicatum, Patamogeton pectinatus) had recovered, despite a major reduction in the roosting gull population, no change in salinity, and only small reductions in phytoplankton biomass and total phosphorus concentration.
• 3 Recovery of the plants may be linked to grazing of periphyton on them by an increased population of a mysid Neomysis integer which had been suppressed by toxicity from an alga, Prymnesium parvum formerly stimulated by the ingress of gull guano.
• 4 A cladoceran community present in the clear-water phase has not recovered and may be suppressed by continued high salinities. Further restoration of the lake requires displacement of the large phytoplankton biomass and this might best be contemplated by land use changes leading to lowered salinity and predicted recovery of grazing Cladocera.
• 5 Models are given which summarize the likely workings of the system in the early twentieth century, the mid-twentieth century, the 1970s and the late 1980s.

     

Release of inorganic N,P and K in peat soils; effect of temperature,water chemistry and water level

In the Netherlands, fens that are fed by polluted river water are often eutrophic, whereas fens fed by calcium-rich groundwater often are mesotrophic. Differences in trophic status can not always be attributed to differences in the nutrient load of the water. In this paper we try to determine if the inflow of river water in fens, in fact, accelerates the soil nutrient release, thereby creating more eutrophic conditions (‘internal eutrophication’). For this purpose, we compared nutrient release rates (N, P and K) in soil cores fromSphagnum peat andCarex peat saturated with different media, that were artificially created to mimic the three basic water sources: polluted river water, unpolluted calcium-rich groundwater and rainwater. In addition, we studied the effect of temperature and water level on nutrient release rates. The experiments proved thatSphagnum peat released much more P and ammonium thanCarex peat. The strong site effect proved consistent throughout the water chemistry treatments, which indicates that soil quality may be the most important agent determining nutrient release rates. Nevertheless, it was established that water chemistry and water level are of significant influence on nutrient release rates in peat soils. In particular, river water stimulated P release by the peat, most notably in theSphagnum peat. P-release in both soils was only minor when the soils were incubated in clean Ca-rich groundwater. It is suggested that P release is strongly associated with soil chemical processes, and that high P release rates after incubation in river water are due to the high sulphate content of the water. The net release from the soil of ammonium, potassium and phosphate increased with increasing temperature. A freezing treatment significantly increased nutrient availability. The results of the experiments are examined in the context of hydrologic management strategies for the conservation of fens in agricultural landscapes.     

The relation between vegetation and soil chemistry gradients in a ground water discharge fen

Abstract. The soil chemistry of a headwater valley fen is influenced by local ground water discharge that supplies base cations and alkalinity to the fen. An irrigation canal just upward of the fen is the source of this alkalinity. The ecological consequences of this artificial system are studied both on the soil and vegetation level. Rich-fen species of the alliance Caricion davallianae are connected to soil water alkalinity and soil base status. They depend directly on the alkaline ground water discharge. In addition, the local input of this water causes a gradient-rich pattern from poor to rich fen, and it is therefore concluded that it is responsible for the presence of intermediate fen vegetation too. High nutrient levels in the irrigation water have not influenced the fen until now. This case study illustrates the possibility for rich fen restoration after acidification. Irrigation with alkaline water is efficient if excess nutrients can be removed.     

The relationships of vegetation to surface water chemistry and peat chemistry in fens of Alberta,Canada

The relationships between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient. Each of the three fen types have their own characteristic species. The extreme-rich fens are characterized by Calliergon trifarium, Drepanocladus revolvens, Scirpus hudsonianus, S. cespitosus, Scorpidium scorpioides, and Tofieldia glutinosa. Moderate-rich fens are characterized by Brachythecium mildeanum, Carex diandra, Drepanocladus vernicosus, D. aduncus, and D. polycarpus. Poor fens are characterized by Carex pauciflora, Drepanocladus exannulatus, Sphagnum angustifolium, S. jensenii, and S. majus. Moderate-rich fens have fewer species in common with poor fens than with extreme-rich fens, while species richness is highest in the moderate-rich fens and lowest in poor fens. Variation in vascular plant occurrence appears to be more associated with nutrient levels, while bryophytes are more affected by changes in acidity and mineral elements. Based on chemical criteria, the three fen types are clearly separated by surface water pH, calcium, magnesium, and conductivity, but are less clearly differentiated by the nitrogen and phosphorus components of the surface waters. Moderate-rich fens are chemically variable both temporally and spatially, whereas poor fens and extreme-rich fens are more stable ecosystems. Whereas components of alkalinity-acidity are the most important factors that distinguish the three fen types in western Canada, nutrient concentrations in the surface waters generally do not differ appreciably in the three fen types.     

Experimental restoration of a fen plant community after peat mining

Question: Which restoration measures (introduction of donor diaspore material, application of straw mulch, alteration of residual peat depths) contribute to the establishment of a fen plant community on minerotrophic surfaces after peat mining? Location: Rivière‐du‐Loup peatland, southern Québec, Canada at 100 m a.s.1. Methods: The effectiveness of introducing fen plants with the application of donor diaspore material was tested. The donor diaspore material, containing seeds, rhizomes, moss fragments, and other plant propagules, was collected from two different types of natural fens. We tested whether the application of straw mulch would increase fen species cover and biodiversity compared to control plots without straw mulch. Terrace levels of different peat depths (15 cm, 40 cm, and 56 cm) were created to test the effects of different environmental site conditions on the success of re‐vegetation. Results: Applying donor seed bank from natural fens was found to significantly increase fen plant cover and richness after the two growing seasons. Straw mulch proved to significantly increase fen plant richness. The intermediate terrace level (40 cm) had the highest fen plant establishment. Compared to reference sites, the low terrace level (15 cm) was richer in base cations, whereas the high terrace level (56 cm) was much drier. Conclusions: The application of donor diaspore material was demonstrated as an effective technique for establishing vascular fen plants. Further re wetting measures are considered necessary at the restoration site to create a fen ecosystem rather than simply restoring some fen species.     

Surface peat structure and chemistry in a tropical peat swamp forest

Background and Aims

Tropical peat swamp forests (PSF) are great stores of terrestrial carbon and host unique biodiversity. Despite their importance for carbon accounting, the peat characteristics are sparsely studied, and the effect of microtopography on peat properties has not been reported before.

Methods

We compared PSF peat soil characteristics down to 70 cm under differing microtopographical conditions and hydrology.

Results

Long-term water table level data combined with the data from peat structure and chemistry analyses showed differences in most of the measured properties between hummocks and hollows. Decomposition degree was lowest at hummock and hollow surfaces while bulk density and C content increased towards deeper peat. Ash, P, K, Ca and Mg had highest concentrations on hummock surfaces with declining trend downwards, whereas N had no clear concentration pattern along the elevation gradient.

Conclusions

The microtopographical features may not only differ in regards to the water table-induced oxygen conditions but also due to differences in nutrient dynamics.     

Spring fen vegetation and water chemistry in the Western Carpathian flysch zone

In the western part of the Carpathian flysch zone, aquifers host several springwater chemistry types. Four vegetation types, distinguished along the poor-rich gradient (tufa-forming and peat forming brown moss fens, moderately rich and poorSphagnum fens), have been compared with respect to the main habitat factors. Water calcium and magnesium concentrations, pH and conductivity as well as the soil organic carbon content were the properties measured that showed the strongest correlation with the main vegetation gradient (the poor-rich gradient). Further, significant differences in iron, sodium, potassium, sulphate and phosphate concentrations were also found between pairs of related vegetation types. The range of calcium concentrations is wide (2–300 mg/l). The calcium concentration in tufa-forming springs is higher than values usually reported from northern and western Europe. Tufa formation is influenced not only by high calcium concentrations, but also by the total chemical composition of springwater and both climatic and topographic conditions. There is a great excess of cations over Cl⁻ and SO ₄ ²⁻ , balanced by HCO ₃ ⁻ and CO ₃ ²⁻ in springs with the most intense tufa precipitation. Unusually high calcium concentrations combined with high iron concentrations were found in peat-forming brown moss fens. RichSphagnum-fens with calcitolerantSphagnum species are distinctively low in phosphates. The Western Carpathian poor fens dominated bySphagnum flexuosum have water and soil calcium concentrations comparable to those reported from rich fens of some other areas. The springwater of these fens are rich in iron, phosphates and sulphates. The poorest spring fens withSphagnum fallax, S. magellanicum, S. papillosum andS. auriculatum are not only poor in calcium, but also in iron, sodium and potassium.     

Peat and water chemistry at Big Run Bog,a peatland in the Appalachian mountains of West Virginia,USA

At Big Run Bog, aSphagnum-dominated peatland in the unglaciated Appalachian Plateau of West Virginia, significant spatial variation in the physical and chemical properties of the peat and in surface and subsurface (30 cm deep) water chemistry was characterized. The top 40 cm of organic peat at Big Run Bog had average values for bulk density of 0.09 g · cm^–3, organic matter concentration of 77%, and volumetric water content of 88%. Changes in physical and chemical properties within the peat column as a function of depth contributed to different patterns of seasonal variation in the chemistry of surface and subsurface waters. Seasonal variation in water chemistry was related to temporal changes in plant uptake, organic matter decomposition and element mineralization, and to varying redox conditions associated with fluctuating water table levels. On the average, total Ca, Mg, and N concentrations in Big Run Bog peat were 33, 15, and 1050 mol · g^–1, respectively; exchangeable Ca and Mg concentrations were 45 and 14 eq · g^–1 , respectively. Surface water pH averaged 4.0 and Ca⁺⁺ concentrations were less than 50 eq · L^–1 . These chemical variables have all been used to distinguish bogs from fens. Physiographically, Big Run Bog is a minerotrophic fen because it receives inputs of water from the surrounding forested upland areas of its watershed. However, chemically, Big Run Bog is more similar to true ombrotrophic bogs than to minerotrophic fens.     

Bryophytes from some travertine-depositing sites in France and the U.K.: relationships with climate and water chemistry

Abstract

The bryophyte florash of 14 travertine-depositing sites in the French Alps and Britain were investigated and consisted of 34 taxa (26 mosses and eight hepatics), with the commonest species, Eucladium verticillatum and Palustriella (Cratoneuron) commutata, occurring in both countries. Species richness ranged from 3-15 and was related mainly to site size and heterogeneity with respect to water flow. Bryophytes grew within or close to Ca-bicarbonate waters with base concentrations (HCO₃ ) ranging from 1.42 to 7.58 mM at pH 6.9-8.3. P. commutata sensu lato was found to extend to more northerly sites in Europe than E. verticillatum, although the two species were frequently present at the same site. Principal component analysis suggested that the distribution of P. commutata var. commutata was influenced more by temperature than water chemistry.     

Aspects of the ecology of Prymnesium parvum (Haptophyta) and water chemistry in the Norfolk Broads, England

SUMMARY. Prymnesium parvum , an ichthyotoxic phytoplankter, has been recorded, at times abundantly, in the River Thurne, Norfolk, and its associated Broads. Its occurrence has been apparently more frequent and its population sizes probably larger since the late 1960s than previously and fish mortalities due to it now occur almost annually.
The Thurne system is brackish and may have become more so, due to exploitation by drainage pumps, of a saline water table, in recent years. Evidence for this is conflicting, but in any case an increase in salinity is unlikely to have made increased Prymnesium growth more likely. Eutrophication of some Broads in the system is most likely to have increased the populations of Prymnesium since the late 1960s and data are presented on the present water chemistry of the system for comparison with previous records, and on current phytoplankton and Prymnesium crops in different parts of it.
P. parvum has been isolated from the system as a unialgal culture and compared in morphology, salinity tolerance and ichthyotoxicity with a strain of P. parvum from Israel. The Broads strain differs slightly in size and pigmentation, but not in salinity tolerance. In culture it produces more ichthyotoxin than the Israeli strain.     

Co-existence of larval zygoptera (Odonata) common to the Norfolk Broads (U.K.)

Summary The temporal and spatial components of resource partitioning were investigated in an assemblage of zygopterans. Spatial separation appeared to be relatively more important to their co-existence than temporal separation. Spatial differences separated Coenagrion pulchellum from the other species, Enallagma cyathigerum from both Ischnura elegans and Erythromma najas, and to a small extent I. elegans from E. najas. Difference in size (temporal separation) was important to the co-existence of I. elegans and E. najas (through a difference in final instar size), and may have been important in assisting the spatial separation of E. cyathigerum (through displacement of life cycles). This arrangement appears to differ from that of other aquatic insects for whom temporal separation through life cycle displacement is a very important component of community structure.     

Hydrologic variability, water chemistry, and phytoplankton biomass in a large floodplain of the Sacramento River, CA, U.S.A.

The Yolo Bypass, a large, managed floodplain that discharges to the headwaters of the San Francisco Estuary, was studied before, during, and after a single, month-long inundation by the Sacramento River in winter and spring 2000. The primary objective was to identify hydrologic conditions and other factors that enhance production of phytoplankton biomass in the floodplain waters. Recent reductions in phytoplankton have limited secondary production in the river and estuary, and increased phytoplankton biomass is a restoration objective for this system. Chlorophyll a was used as a measure of phytoplankton biomass in this study. Chlorophyll a concentrations were low (<4 μg l^?1) during inundation by the river when flow through the floodplain was high, but concentrations rapidly increased as river inflow decreased and the floodplain drained. Therefore, hydrologic conditions in the weeks following inundation by river inflow appeared most important for producing phytoplankton biomass in the floodplain. Discharges from local streams were important sources of water to the floodplain before and after inundation by the river, and they supplied dissolved inorganic nutrients while chlorophyll a was increasing. Discharge from the floodplain was enriched in chlorophyll a relative to downstream locations in the river and estuary during the initial draining and later when local stream inflows produced brief discharge pulses. Based on the observation that phytoplankton biomass peaks during drainage events, we suggest that phytoplankton production in the floodplain and biomass transport to downstream locations would be higher in years with multiple inundation and draining sequences.     

The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. I. Trophic relationships with special reference to the role of Neomysis integer

• 1 Hickling Broad, a shallow, brackish lake in England, changed from dominance by submerged aquatic plants to dominance by phytoplankton in the 1970s. These changes were ascribed to the effects of guanotrophicatioh by black-headed gulls, and increased salinity which together resulted in fish kills caused by a toxic alga, Prymnesium parvum. A mysid, Neomysis integer, was believed to be important in switching the system to plankton dominance through its presumed selective feeding on Cladocera and increasing population size as fish predation decreased.
• 2 Studies on laboratory predation rates of the mysid on Cladocera and on the population dynamics, predation rates and diet of the mysid and the populations of the major zooplankter, Eurytemora affinis in the Broad in the 1980s, have shown that the former explanations were incomplete. The mysid could have markedly reduced the cladoceran community, for it has potentially high predation rates, but Cladocera were probably lost through salinization. Neomysis feeds efficiently on Eurytentora affinis, but the latter reproduces rapidly and its populations are unlikely to be controlled by mysid predation. Nauplii and small copepodites are selectively taken. Alternative and probably major food sources for the mysid are periphyton and benthic algae and detritus.
• 3 Roach and bream readily take the mysid but the present fish stock in the Broad is very low and can now exert minimal pressure on the mysid population. An invertebrate predator on the mysid, Palaemometes varians, is also unlikely to have major effects. The former model of the operation of the Broad's ecosystem needs reconsideration in view of the findings.

     

Effect of sulfuric acid discharge on river water chemistry in peat swamp forests in central Kalimantan,Indonesia

To estimate the range of area that is affected by sulfuric acid pollution after pyrite oxidation, the surface water chemistry of two rivers in peat swamp forests in central Kalimantan, Indonesia, was surveyed at 1.0- to 3.0-km intervals in September 2003 and 2004 (dry season) and March 2004 and 2005 (rainy season). Water discharged from canals into the main stream of the Sebangau River and the Kahayan River showed lower pH compared to the mainstream water of the rivers, implying sulfuric acid loading from the canal to the main stream of the rivers. The ratio of concentrations of sulfate ion/chloride ion, which was used as a parameter for estimating the contribution of pyritic sulfate to river water chemistry, showed that sulfuric acid loading from pyrite oxidation occurred from the river mouth up to 150 km upstream in both rivers. Water of the main stream of the rivers as well as water discharged from artificial canals into the main stream in the rainy season showed much higher acidity and a higher ratio of sulfate ion/chloride ion than that in the dry season. This result implies that the discharge of pyritic sulfate from peat swamp forests to the limnological system is much higher in the rainy (high water table) season than the dry (low water table) season. Water in the canal in the rainy season was found to be highly acidic (pH = 2.0–3.0). Pyrite oxidation after peatland development causes not only acidification of soil but also acidification of the limnological ecosystem.     

Groundwater and surface water hydrology of a small groundwater-fed fen

The hydrology of a small quaking fen was investigated by measuring all components of the water budget. Water-level measurements indicated that the fen is a focus for groundwater discharge, and that there is a lateral (subsurface) flow from the fen toward surrounding areas during most of the year. The hydrology, however, is strongly influenced by man, as water tables are maintained during dry periods by pumping water into the area. This action results in a reversal of flow patterns as surface water from a ditch infiltrates the fen and groundwater recharge occurs.Two approaches for calculation of groundwater and surface water terms were compared. The two procedures differ in the way that vertical and horizontal hydraulic conductivity of the soil is calculated. Hydraulic conductivity estimated from in situ tube experiments was one to two orders of magnitude lower than hydraulic conductivity estimates from numerical water budget analyses.Four one-month periods were selected for calculations of complete water budgets. Results of calculations of water flow were compared in respect to the overall error in the water budget (calculated as percent difference between inputs and outputs). Water budgets calculated from data on hydraulic conductivity gave high residual errors (56.% ± 16.3%). When hydraulic conductivity was derived from numerical analyses, the errors were very small (2.8% ± 3.1%) and the difference between inputs and outputs over a period of 127 days was only 2.6 mm (0.45%).     

Effects of wildfire ash on water chemistry and biota in South-Western U.S.A. streams

1. We monitored streams within the Gila River drainage in south‐western New Mexico, U.S.A., over a 5‐year period, to investigate the influence of ash input on water quality and stream biota following forest wildfires. 2. Nutrients [ammonium, nitrate, soluble reactive phosphate (SRP)], potassium and alkalinity were most affected by fires; all were increased in stream water following ash input. Concentrations of each returned to prefire conditions within 4 months. Ammonium and nitrate also increased in stream water as a result of atmospheric fallout (e.g. smoke) from fires outside the catchment. 3. Periphyton biomass was not affected significantly by wildfires, although there was a shift in diatom assemblage to smaller more adnate taxa. Cocconeis placentula was frequently the dominant postfire species. 4. The influence of wildfires on macroinvertebrates ranged from minimal to dramatic reductions in density depending upon the duration of ash flows and the characteristics of the ash material that entered each system. Macroinvertebrate densities returned to prefire conditions within 1 year. 5. An in‐situ ashing experiment was conducted on a first‐order stream in the Gila River drainage to monitor on‐site physiochemical and biotic responses during and after fire ash addition, for comparison with ash delivery from real wildfires on monitored streams. Physical–chemical parameters and algae and macroinvertebrates were monitored in an ashed and upstream reference reach for 13 months. Results generally substantiated findings from monitored streams. 6. Concentrations of major ions and nutrients, as well as turbidity, conductivity and pH, increased immediately in stream water below the point of ashing, while dissolved oxygen decreased. Changes in water chemistry were short‐lived (=24 h) except for SRP. The concentration of SRP in stream water was significantly higher in the ashed reach than the control reach for at least 1 month after ash input. 7. Periphyton biomass and diatom assemblages were not significantly altered in the ashing study, whereas macroinvertebrate density was measurably lower in the ashed reach for nearly a year. Macroinvertebrate drift was over 10‐fold greater in the ashed reach compared with the reference reach during ashing. Dissimilarity between macroinvertebrate communities in the reference and ashed reaches was significantly greater than variation within reaches for nearly a year.