Nutrient Levels In Water Column Research Articles

Assessment of the efficiency of river macrophytes to detect water-column nutrient levels and other environmental conditions in Irish rivers

Macrophytes are an essential biological element of freshwater aquatic ecosystems and are well known to reflect prevailing ecological conditions in rivers. Their use as bioindicators of nutrient status in river systems is widespread yet their reliability is hotly debated. The aim of this investigation was to assess whether macrophytes are reliable indicators of nutrient levels or better applied as indicators of other non-nutrient environmental conditions. The importance of two water-column nutrients; nitrates (N) and orthophosphates (P) were assessed in terms of their influence on macrophyte species richness and diversity in relation to other non-nutrient environmental factors using 395 river plots from Ireland. Then, in this context, the efficiency of macrophytes to detect nutrient levels was assessed by selecting two macrophyte-based water quality assessment tools; the Mean Trophic Rank (MTR) and the Predictions And Classification System for river macrophytes (LEAFPACS2). Finally, the ability of phytosociological communities within these rivers to reflect trophic levels was examined using the same two water quality assessment tools. It was shown that water-column nutrients N and P have a minor influence on macrophyte richness and no significant influence on macrophyte diversity and that MTR and LEAFPACS2 were only weakly correlated with N and P levels. It was concluded that macrophytes are sensitive to environmental changes but respond to a combination of ecological factors rather than N or P alone. Therefore, this study suggests that macrophytes are not the most efficient taxon group to apply when assessing trophic changes in isolation of other non-nutrient factors.

Depth-Dependent Response of Fecal Indicator Bacteria in Sediments to Changes in Water Column Nutrient Levels.

Concentrations of in bottom sediments can influence the assessment of microbial stream water quality. Runoff events bring nutrients to streams that can support the growth of in sediments. The objective of this work was to evaluate depth-dependent changes in populations after nutrients are introduced to the water column. Bovine feces were collected fresh and mixed into sediment. Studies were performed in a microcosm system with continuous flow of synthetic stream water over inoculated sediment. Dilutions of autoclaved bovine manure were added to water on Day 16 at two concentrations, and KBr tracer was introduced into the water column to evaluate ion diffusion. Concentrations of , total coliforms, and total aerobic heterotrophic bacteria, along with orthophosphate-P and ammonium N, were monitored in water and sediment for 32 d. Sediment samples were analyzed in 0- to 1-cm and 1- to 3-cm sectioned depths. Concentrations of and total coliforms in top sediments were approximately one order of magnitude greater than in bottom sediments throughout the experiment. Introduction of nutrients to the water column triggered an increase of nutrient levels in both top and bottom sediments and increased concentrations of bacteria in the water. However, the added nutrients had a limited effect on in sediment where bacterial inactivation continued. Vertical gradients of concentrations in sediments persisted during the inactivation periods both before and after nutrient addition to the water column.

Effects of common carp (Cyprinus carpio) on water quality in aquatic ecosystems dominated by submerged plants: a mesocosm study

Common carp (Cyprinus carpio) have been introduced into aquatic systems across the world, where their benthivorous feeding behavior has resulted in serious water quality problems. A 12-week mesocosm experiment was set up to test the hypotheses that common carp increase water column nutrient levels and decrease water clarity in aquatic ecosystems dominated by submerged plants. Further, we tested whether the effect of common carp on macrophytes depended on the species of plants. Relative to the controls, the presence of carp decreased water clarity by increasing total suspended solids (TSS) and light attenuation. However, levels of total nitrogen (TN) and total phosphorus (TP) in the water column were reduced. No significant change in phytoplankton biomass (measured as chlorophylla) and the biomass ofHydrilla verticillatawas observed between common carp treatment mesocosms and controls, but the common carp did reduce the biomass of the submerged macrophyteVallisneria denseserrulata. We conclude that removal of common carp is likely to improve water clarity in aquatic ecosystems dominated by submerged plants primarily by decreasing TSS and that the effect of common carp on macrophytes is stronger for the meadow formingVallisneriathan for the canopy formingHydrilla.

Submerged Macrophytes Exhibit Different Phosphorus Stoichiometric Homeostasis.

Phosphorus (P) is a limiting element in many aquatic ecosystems. Excessive P input often leads to cyanobacterial bloom, thus triggering ecological imbalances and a series of environmental problems. Submerged macrophytes have a strong ability to absorb P and play important roles in maintaining aquatic ecosystem functions. However, the degree to which submerged macrophytes maintain their tissue P contents in various nutrient levels and the corresponding influencing factors are still not very clear. In this study, the stoichiometric characteristics and stoichiometric homeostasis of P in the aboveground and belowground parts of three submerged macrophytes, Vallisneria natans (Lour.) Hara, Hydrilla verticillata (L.f.) Royle, and Ceratophyllum demersum (L.), with great differences in growth forms, were studied under different growth times and nutrient levels via laboratory experiments. The results showed that the water conductivity, turbidity, and chlorophyll content increased significantly with the increasing nutrient levels. The variation of species, organ, growth time, and nutrient level could significantly affect the P contents of submerged macrophytes. Among these factors, the variance contribution rates caused by the differences of nutrient levels in water column were the highest at more than 50%. The P stoichiometric homeostasis index (HP) in the belowground parts of the three submerged macrophytes was higher than that of the aboveground parts. The HP decreased by the growth time; the HP of V. natans was significantly higher than those of H. verticillata and C. demersum. In summary, the P stoichiometric homeostasis in submerged macrophytes could reflect their responses to environmental changes, and the P content of submerged macrophytes was an indicator of the bioavailability of external P. H. verticillata exhibited a high growth rate and a high accumulation of P content, making it the most suitable species in this study for removing large amounts of P from water in a short term.

Aeration and plant coverage influence floating treatment wetland remediation efficacy

Nutrient contamination of waterways is a growing concern, instigating the emergence of floating treatment wetland systems (FTWs) to remove nutrients from water. To determine if aeration of water systems enhances nutrient removal efficacy or nutrient fixation within plant tissues, aeration in combination with FTW installation techniques were investigated. During two separate trials with Juncus effusus and Canna flaccida, treatments consisted of either aerated or non-aerated mesocosms, with varying coverage and planting density combinations. Aeration increased the dissolved oxygen levels within each mesocosm, but reduced the removal of nitrogen and phosphorus from the water column in comparison to non-aerated systems. Plant samples collected from 100% planting density treatments that were aerated had a greater nitrogen uptake than non-aerated by as much as 55% or 13.5 g/m2 at harvest. Some discrepancies between plant uptake and water column nutrient levels can be attributed to microbially-mediated nitrogen losses (e.g., denitrification).

Characteristics of sediment resuspension in Lake Taihu, China: A wave flume study

Lake Taihu is a typical shallow lake which frequently happens sediment resuspension induced by wind-induced waves. The experiments are carried on to simulate the wave disturbance processes in wave flume by setting a series of wave periods (1.2 s, 1.5 s, 1.8 s) and wave heights (2 cm, 10 cm). It aims to analyze the characteristics of sediment resuspension and the mechanisms of nutrients release and to evaluate the effects of sediment dredging on sediment resuspension and nutrients release in Lake Taihu. The results show that wave shear stress during 2 cm and 10 cm wave height processes ranges 0.018–0.023 N/m2 and 0.221–0.307 N/m2, respectively. Wave shear stress has no significant differences between wave periods. Wave height has much more effects on sediment resuspension. Wave height of 2 cm could induce total suspended solids (TSS) reaching up to 5.21 g/m2 and resuspension flux of sediment (M) up to 1.74 g/m2. TSS sharply increases to 30.33–52.41 g/m2 and M reached up to 48.94 g/m2 when wave height reaches to 10 cm. The disturbance depth under different sediment bulk weights ranges from 0.089 to 0.161 mm. Variation of suspended solids in 3 layers (1 cm, 5 cm, 20 cm above sediment interface) has no significant differences. Organic matter, TN and TP have positive relationship with SS. Organic matter is only accounted for 5.7%–7.3% of SS. The experiments under different sediment bulk densities (1.34 g/cm3, 1.47 g/cm3 and 1.59 g/cm3) find that TSS and M fall by 44.2% and 39.8% with sediment bulk density increasing, respectively. Total TN, DTN, TP and DTP decrease by 24.3%–33.6%. It indicates that sediment dredging could effectively reduce SS concentration and nutrient levels in water column. The researches provide a theoretical basis for sediment dredging to control the shore zone of Lake Taihu for lake management.

Macrophyte-induced thermal stratification in a shallow urban lake promotes conditions suitable for nitrogen-fixing cyanobacteria

Densely vegetated shallow lakes often experience low water column nutrient levels and reduced phytoplankton growth, but in some cases a high phytoplankton biomass can co-exist with submerged macrophytes. The conditions that favour phytoplankton blooms within areas colonized by submerged macrophytes remain largely unexplored. We investigated changes in water quality variables and phytoplankton community composition data in relation to macrophyte-induced thermal stratification in a shallow urban lake. The results indicate that submerged macrophytes may favour internal loadings of phosphorus and low DIN:TP ratios, in periods when macrophyte-induced thermal stratification of the water column is common. Blooms of nitrogen-fixing cyanobacteria occurred under the strongly stratified conditions triggered by the high macrophyte biomass and elevated canopy, even though nitrogen limitation was apparent during the whole growing season. These findings suggest that submerged macrophytes can promote blooms of nitrogen-fixing cyanobacteria once they are sufficiently tall and dense to induce stable water column conditions.

Long-term monitoring of the impact of a capture-based bluefin tuna aquaculture on water column nutrient levels in the Eastern Aegean Sea, Turkey

Capture-based aquaculture of Atlantic bluefin tuna in the Mediterranean has been expanding rapidly but little is known about its environmental impact. In order to understand the consequences of this new sector, long-term monitoring is needed. For this purpose, we investigated the impact of a capture-based tuna farm located in the Gerence Bay (Aegean Sea) on the water column on a seasonal basis from 2005 to 2008, where in the water column, temperature, salinity, pH, dissolved oxygen, nutrients (nitrite, nitrate, ammonium, and phosphate), and chlorophyll a, in the sediment organic carbon variables were measured. Although highest nutrient concentrations were observed at the cage station as compared to the two controls in the production period, differences were not statistically significant between stations. Monitoring of physico-chemical parameters, nutrients, and chlorophyll a in water column together with organic carbon in sediment did not show detectable impact of fattening of Atlantic bluefin tuna. This was probably caused by strong currents present in the area, location of the cages away from the coast, hence high water depth, controlled feeding, and periodic presence of tuna farming activity in the study area.

Effects of nutrient levels in surface water and sediment on the growth of the floating-leaved macrophyte Trapa maximowiczii: implication for management of macrophytes in East Bay of Lake Taihu, China

Trapa maximowiczii is a floating-leaved macrophyte common in China. The plant population in East Bay, Lake Taihu, has been expanding rapidly in recent years. In order to better understand the mechanisms controlling the population dynamics in this species, two outdoor experiments were conducted from 9 May to 8 July 2007, evaluating the effect on the growth of T. maximowiczii of different nutrient levels in water column and sediment. Results showed that high concentration of nutrients (nitrogen and phosphorous) in water led to significant increases in rosette diameter and plant dry weight, dry weight of aquatic roots and anchoring roots, but had no effect on plant height or main stem node count. Phosphorus enrichment resulted in increases in plant dry weight and seed number. However, no such difference was observed between the nitrogen enrichment treatment and the control. Sediment fertility had significant effects on plant growth. Plant height, plant dry weight, dry weight of aquatic and anchoring roots, and maximum rosette diameter were significantly greater in high-nutrient sediment than those in low-nutrient sediment. This study suggests that eutrophication of water (especially increasing phosphorus loading) and accumulated nutrients in sediment may be among the causes leading to increasing biomass of the floating-leaved macrophyte T. maximowiczii in East Bay of Lake Taihu.

Epifaunal community composition and nutrient addition alter sediment organic matter composition in a natural eelgrass Zostera marina bed: a field experiment

Eutrophication and fishing are common perturbations in aquatic ecosystems that have pervasive effects on community structure, including species diversity and abundance. While sedi- ment biogeochemical processes probably respond to these stressors, the linkages to ecosystem func- tioning remain poorly understood. To explore these linkages, we experimentally manipulated water column nutrient levels and food web composition (i.e. predator and grazer presence and absence) in a factorial design using field enclosures situated in a natural eelgrass Zostera marina bed. After 28 d, we quantified sediment organic matter (SOM) abundance and composition using measures of total organic carbon and nitrogen as well as fatty acid (FA) biomarkers. Nutrient enrichment led to a rapid increase of epiphytes and a decline in Z. marina biomass. Responding to the available algae, grazers reduced epiphytes and the abundance of microalgal FAs in the sediment. Predators reduced Z. marina abundance and possibly its ability to trap particulate organic matter (OM), leading to lower sediment organic carbon content and total FA abundance. There was evidence of a trophic cascade as FA contributions to sediments from epiphytes and diatoms were higher in treatments with both grazers and predators than in treatments with grazers only. Predators increased contributions of labile diatom-derived OM, which probably resulted in higher proportions of bacterial FA. Inter- actions between nutrient additions and food web composition indicated that SOM responses were complex and not predictable from single variables. Changes in SOM composition, combined with a rapid heterotrophic bacterial response, suggest that resource levels and aboveground community structure are important to sediment biogeochemistry in natural seagrass systems.

Agent‐based modeling of the complex life cycle of a cyanobacterium (Anabaena) in a shallow reservoir

The cyanobacterium Anabaena flos‐aquae and many other phytoplankton species have a complex life cycle that includes a resting stage (akinete). We present a new agent‐based (also known as individual‐based) model of Anabaena that includes the formation and behavior of akinetes. The model is part of a coupled Eulerian‐Lagrangian model and can reproduce the main features of the observed seasonal and interannual population dynamics in Bugach Reservoir (Siberia), including an unexpectedly large bloom in a year with low nutrient concentrations. Model analysis shows that the internal loading of phosphorus (P) due to germination from the sediment bed is ~10% of the total input. However, most of the long‐term nutrient uptake for Anabaena occurs in the sediment bed, which suggests that the sediment bed is not just a convenient overwintering location but may also be the primary source of nutrients. An in silico tracing experiment showed that most water column cells (~90%) originated from cells located in the sediment bed during the preceding winter. An in silico gene knockout experiment (akinete formation is prohibited) showed that the formation of resting stages is of critical importance to the survival of the population on an annual basis. A nutrient‐reduction management scenario indicates that Anabaena densities increase because they are less sensitive to water column nutrient levels (because of the sediment bed source) than other species.

Influence of autochthonous dissolved organic carbon and nutrient limitation on alachlor biotransformation in aerobic aquatic systems.

Much work has suggested that the rate of attenuation of water-soluble organic contaminants in aerobic aquatic systems is dependent on the level of secondary nutrients in the water column. For example, the decay rate of alachlor, a common herbicide, was over 10 times higher under hypereutrophic compared with oligotrophic water conditions. It has been presumed that higher water column nutrient levels produce larger microbial communities, resulting in higher rates of alachlor cometabolism. However, most earlier field studies only assessed alachlor fate in systems with full light exposure (FLE). Therefore, new experiments were performed to assess how variations in light level affect alachlor cometabolism in such systems. Twelve tank mesocosms were maintained using identical nitrogen (N) and phosphorus (P) supply conditions: four units with full light exposure (100% FLE), four with partial shading (19.3% FLE), and four with near complete shading (0.5% FLE). Alachlor half-lives were found to vary broadly, from 50 to 60 days in higher light units to > 180 days in the 0.5% FLE units. Nutrient analysis indicated that the low light units were severely carbon (C)-limited for microbial decomposition, whereas the other units had excess C relative to N and P. Apparently, reduced light levels cause decreased production of bioavailable C for decomposition, which significantly reduces alachlor cometabolism. The data suggest that water column nutrient levels only correlate with the alachlor decay rate when light levels are high, and that the biodegradable carbon supply must be considered when the fate of water-soluble contaminants in aerobic aquatic systems is assessed.

Zostera marina (eelgrass) growth and survival along a gradient of nutrients and turbidity in the lower Chesapeake Bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 142:247-259 (1996) - doi:10.3354/meps142247 Zostera marina (eelgrass) growth and survival along a gradient of nutrients and turbidity in the lower Chesapeake Bay Moore KA, Neckles HA, Orth RJ Survival of transplanted Zostera marina L. (eelgrass), Z. marina growth, and environmental conditions were studied concurrently at a number of sites in a southwestern tributary of the Chesapeake Bay to elucidate the factors limiting macrophyte distribution in this region. Consistent differences in survival of the transplants were observed, with no long-term survival at any of the sites that were formerly vegetated with this species but that currently remain unvegetated. Therefore, the current distribution of Z. marina likely represents the extent of suitable environmental conditions in the region, and the lack of recovery into historically vegetated sites is not solely due to lack of propagules. Poor long-term survival was related to seasonally high levels of water column light attenuation. Fall transplants died by the end of summer following exposure to levels of high spring turbidity (Kd > 3.0). Accumulation of an epiphyte matrix during the late spring (0.36 to 1.14 g g-1 dry wt) may also have contributed to this stress. Differences in water column nutrient levels among sites during the fall and winter (10 to 15 µM dissolved inorganic nitrogen and 1 µM dissolved inorganic phosphates) had no observable effect on epiphyte accumulation or macrophyte growth. Salinity effects were minor and there were no symptoms of disease. Although summertime conditions resulted in depressions in growth, they did not alone limit long-term survival. It is suggested that water quality conditions enhancing adequate seagrass growth during the spring may be key to long-term Z. marina survival and successful recolonization in this region. Chesapeake Bay · Zostera marina · Seagrass · Growth · Survival · Epiphytes · Water quality · Inorganic nutrients · Turbidity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 142. Publication date: October 24, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Mechanisms of benthic algal recovery following spates: comparison of simulated and natural events.

We conducted a manipulative field experiment to examine individual and interactive effects of scour and short-term nutrient enrichment (4 h exposure) on postspate recovery of benthic algae in a desert stream. We then compared recovery from these simulated-spate conditions to algal recovery patterns following a natural spate that increased water-column nutrient levels for 2 weeks. That event differentially scoured communities on artificial substrata in place for a long-term experiment, significantly reducing biomass in 49-day-old communities but causing no significant reduction of biomass in older, 133-day-old communities. Thus, we were able to examine recovery of scoured and non-scoured benthic algal communities under natural post-spate conditions. Both natural and simulated spates reduced actual and relative abundances of diatoms within communities. In the manipulative experiment, scoured communities accrued biomass more rapidly than those not subjected to scour, but short-term enrichment had not effect. Accrual of diatoms and green algae was stimulated by the scour manipulations, while cyanobacteria maintained equal rates of growth in all treatments. Following the natural spate, diatom and green-algal densities increased in scoured communities, but recovery of algal biomass was slow on both scoured and non-scoured substrata, primarily because cyanobacteria, the dominant algal group on all tiles, did not increase under exposure to highly nitrate-enriched waters. Rates of algal cell accrual were inversely correlated with the amount of algal biomass present at the start of a recovery sequence. Algal immigration rates measured immediately after the natural spate and during an interflood period in the same season did not differ, indicating that the algal drift pool was not augmented by disturbance. Benthic algal recovery following spates is strongly influenced by the degree of scour generated by the event, but recovery patterns are also affected by the length of post-spate enrichment and the taxonomic composition of the affected community.

Effect of stocking density on shrimp growth rates in manure-fertilized ponds

Ecuadorian Penaeus vannamei were cultured in eight 200-m 2 dirt ponds at four stocking densities (5, 10, 15 and 20 shrimp/m 2). No commercial feed was given to the shrimp. The only input to the ponds was about 36 kg of feedlot cattle manure per pond per week (1800 kg manure ha −1 week −1). Shrimp growth was not correlated with variations in water quality among treatments (e.g., temperature, pH, DO, secchi visibility). Water-column nutrient levels were less than or equal to nutrients in incoming water and did not increase with addition of cattle manure. Water ATP concentrations were correlated with shrimp stocking density while numerous other biochemical parameters were not. No coliform bacteria were detected in any pond water samples during the study period. Phytoplankton densities and species composition were not different among treatments but varied over time. Two diatoms were the dominant species throughout the study. There was a negative correlation between stocking density and growth. Mean (±SD) weekly shrimp growth across treatments was 0.68±0.00, 1.06±0.02, 1.72±0.2 g individual −1 week −1 for densities of 20, 15, 10, and 5 shrimp/m 2, respectively. Survival averaged 70.8±6.3% for all ponds and was not different among treatments. Shrimp production was 19.3±0.1, 23.0±0.4, 22.8±1.2, 12.3±1.1 kg ha −1 day −1 for densities 20, 15, 10, and 5 shrimp/m 2, respectively. Shrimp production and carrying capacity were not significantly different among the three higher stocking densities.