Wide Range Of Nutrient Concentrations Research Articles

Preliminary results of the combined production of duckweed Spirodela polyrhiza and common carp (Cyprinus carpio) in an aquaponic system

As a result of population growth, increasin amount of food is needed, and agriculture is under an increasing burden to meet these needs. Traditional agriculture is often attacked due to its environmental impact. We must find alternative, environmentally friendly ways to produce more food. Aquaponics is a closed system in which we can produce both fish and plants at the same time. Duckweed species are small, aquatic, floating plants belonging to angiosperms. It can potentially be an alternative protein source, due to its high protein content, good amino acid supply, and rapid growth. Under suitable conditions, it doubles its weight in 2–4 days, and can reach a yield of 30 t ha-1 year-1in dry matter. It forms a carpet on top of the water and can be found in slow-moving or still waters. Since they are resistant to a wide range of nutrient concentrations, they are also suitable for cleaning wastewater (such as eutrophicated lakes, sewage reservoirs, liquid manure storage). Fish feed is the primary nutrient source for aquaponic systems, which usually contains fishmeal. If duckweed can be used as an alternative for fishmeal in the feed, it could improve the sustainability of the aquaponic and aquaculture systems. In this study, the aim was to develop an optimal harvesting protocol for duckweed Spirodela polyrhiza under aquaponic conditions. In a four weeks experiments, four harvesting protocols were set up, a control where only biomass measurements were made, a 25% group where 25% of the biomass at the time of measurement was harvested, and a 50% and a 75% group where at the time of measurement 50% and 75% of the biomass was harvested. Three replicates were used per treatment. We weighed the biomass every week and removed the amount corresponding to the group. Based on the preliminary results, it can be said that more biomass was obtained in the groups with the 25% harvesting protocol and the control group.

The relationship between inorganic nutrients and diversity of dinoflagellate cysts: An evaluation from the perspective of species abundance distribution

The relationships between the inorganic nutrients and diversity of dinoflagellate cysts (the N-Dc relationships) are one of the most central issues in coastal ecology. It is not only an important pathway to explore the ecological processes of plankton, but also a key element for assessing eutrophication in marine ecosystems. Although the N-Dc relationships have been studied for many years, they have remained controversial, which may be attributed to (1) using samples collected from a single source (2) considering an insufficient range of nutrient concentrations (3) rarely taking into account species abundance distributions (SAD) that could better represent diversity. In this study, the N-Dc relationships are evaluated according to a compiled dataset, which cover the wide range of nutrient concentrations. Species diversity of cysts are estimated by four common diversity metrics and a new SAD parameter. Results show that all diversity metrics are negative with nutrients, which supports that low diversity of cysts could be considered as a signal of eutrophication. Additionally, this study finds a new pattern that SAD of cysts (Nr/N1, Nr and N1 is the abundance of the r-th and the first species in descending order) with decreasing nutrients appears to gradually approach 1: 1/2: 1/3…. In the future, if this pattern can be verified by more investigations, understanding the negative N-Dc relationships is more likely to provide new direction for assessing and managing eutrophication in coastal ecosystem, and even for exploring the general mechanisms determining diversity.

Seasonal Development of Phytoplankton in South Bohemian Fishponds (Czechia)

Fishponds with a relatively small water volume, high fish abundance, and wide range of nutrient concentrations serve as suitable models for ecological studies. Intensified fish production, together with increased input of nutrients from the watershed, resulted in hypertrophic conditions in the majority of fishponds, the most common type of lentic ecosystems worldwide. In order to understand the processes driving plankton succession, we analyzed eight-year data from nine fishponds in Czechia with differing trophic status. The mean concentration of phosphorus (P) was 200 µg L−1 in hypertrophic ponds, 130 µg L−1 in eutrophic, and 40 µg L−1 in mesotrophic. Correspondingly the mean concentration of phytoplankton was 14.9 mg L−1 in hypertrophic ponds, 7.3 mg L−1 in eutrophic, and 1.96 mg L−1 in mesotrophic. Although the fish stock of 200–900 kg ha−1 eliminated zooplankton in eutrophic and hypertrophic ponds the faster-growing algae did not prevail over cyanobacteria. Zooplankton grazing pressure on algae is thus not relevant in studied food webs. Due to the rapid biological denitrification in hypertrophic and eutrophic fishponds resulting in low concentration of mineral nitrogen (N), these ponds were dominated by N-fixing cyanobacteria throughout the whole season. Similarly, the faster-growing algae prevail over cyanobacteria in mesotrophic ponds until the decrease of available mineral nitrogen. The limitation by mineral N is thus the primary driver of phytoplankton composition reflected in cyanobacterial dominance, independently of the trophic status and fish density in studied fishponds.

Interplay of Nutrients, Temperature, and Competition of Native and Alien Cyanobacteria Species Growth and Cyanotoxin Production in Temperate Lakes.

Global warming and eutrophication contribute to formation of HABs and distribution of alien cyanobacteria northward. The current study assessed how alien to Europe Sphaerospermopsis aphanizomenoides and Chrysosporum bergii will co-occur with dominant native Planktothrix agardhii and Aphanizomenon gracile species under changing conditions in temperate freshwaters. The experiments were carried out to examine the effect of nutrients and temperature on the growth rate of cyanobacteria, production of cyanotoxins, and interspecies competition. The highest growth rate was determined for A. gracile (0.43 day−1) and S. aphanizomenoides (0.40 day−1) strains at all the tested nutrient concentrations (IP and IN were significant factors). S. aphanizomenoides adapted to the wide range of nutrient concentrations and temperature due to high species ecological plasticity; however, A. gracile was able to suppress its dominance under changing conditions. Regularity between tested variables and STX concentration in A. gracile was not found, but IP concentration negatively correlated with the amount of dmMC-RR and other non-ribosomal peptides (NRPs) in P. agardhii strains. The relative concentration of NRPs in nontoxic P. agardhii strain was up to 3-fold higher than in MC-producing strain. Our study indicated that nutrients, temperature, and species had significant effects on interspecies competition. A. gracile had a negative effect on biomass of both alien species and P. agardhii.

Monsoonal Influence and Variability of Water Quality, Phytoplankton Biomass in the Tropical Coastal Waters – A Multivariate Statistical Approach

Rushikulya estuary is rich in biodiversity facing significant changes in recent periods due to pollution/anthropogenic impacts from the industries and growing urbanization along the banks of the river. This estuary caters mass nesting of Olive Ridley sea turtles and one of the world's largest rookery in India. In view of the above the present study examined, the seasonal variability of water quality parameters (water temperature, pH, salinity, dissolved oxygen, total suspended matter, inorganic nutrients (NO2-N, NO3-N, NH4-N, PO4-P and SiO4-Si) and the phytopigment i.e. Chlorophyll-a (chl-a) from the seawater samples of three different seasons pre-monsoon, monsoon and post-monsoon.Time-series observations were made at five locations off Rushikulya estuary, Bay of Bengal from March 2011 to February 2013. A wide range of nutrient concentrations except for NO2-N varied from 0.89 - 3.62 µmol/l in the NO3-N, from 1.36 - 6.81 µmol/l in the NH4-N, from 0.66 - 3.45 µmol/l in the PO4- P and from 0.89 -7.97 µmol/l in the SiO4-Si. The highest chl-a (3.72 mg/m3) was recorded during pre-monsoon than monsoon and post monsoon. Factor analysis (FA), showed that three underlying factors, each during pre-monsoon, monsoon and post-monsoon influencing the water quality to the extent of 75.02 %, 67.33 % and 66.37 % respectively. The significant result from a statistical view of non-metric multidimensional scaling (nm-MDS) and cluster analysis (CA) revealed that the chl-a variability was due to the direct influence of nutrients than the physical parameters.Correlation analysis revealed that chl-a was positive correlation with DO, NO2, NO3, PO4 and SiO4, while negative with salinity in pre-monsoon and monsoon. The composite results indicated that the study area is well oxygenated, rich in nutrients and chl-a distribution represents typical upper ocean dynamics and food chain linked to the pristine coastal and ecologically rich ecosystem.

Isotopic biomonitoring of N pollution in rivers embedded in complex human landscapes

The dynamic and hierarchical structure of rivers, together with disruption of the natural river continuum by human activities, makes it difficult to identify and locate sources of nutrient pollution affecting receiving waters and observe its dispersion, thus impairing monitoring efforts. The identification of reliable indicators of anthropogenic nitrogen inputs in catchments is therefore key to achieving effective management of polluted rivers. We tested the capacity of N isotopic signatures (δ15N) of epilithon and snails to provide useful indications of organic and inorganic anthropogenic N inputs in three Mediterranean rivers differing in terms of surrounding land use and physicochemical conditions. We used a combined approach based on (i) analysis of nutrient concentrations in water, (ii) CORINE land cover classification and drainage patterns in catchments and (iii) isotopic analysis of river biota to verify whether isotopic variations were indicative of anthropic activities in the watershed, the associated alteration of water quality, and the consequent impact on snail abundance and diversity.Variation in the δ15N of epilithon within and between rivers reflected localised and diffuse N inputs from inorganic and organic sources. Negative epilithon δ15N values (<0‰) indicated inorganic pollution from agriculture. Values between 4‰ and 8‰ and those above 8‰ respectively indicated moderate organic pollution from urban areas, and high organic pollution, mostly from waste waters. The diversity and abundance of snails decreased with increasing water pollution. While their isotopic variations reflected between-river differences, they failed to indicate within-river variations in anthropogenic N inputs, since the proportion of epilithon in their diet varied along the rivers. Concluding, epilithon was a reliable indicator of anthropogenic N sources across a wide range of nutrient concentrations and anthropogenic inputs, and the proposed approach allowed us to determine the nature of nitrogen pollutants, their sources, location and dispersion along rivers embedded in complex human landscapes.

Use of diatoms for developing nutrient criteria for rivers and streams: A Biological Condition Gradient approach

Nutrient enrichment is one of the most important causes of ecological impairment in surface waters. More effective management of this problem is constrained by a lack of nutrient criteria that link phosphorus and nitrogen concentrations to levels of biological impairment as defined in management agency regulations. We used a new approach for identifying potential nutrient criteria using diatom assemblages and the Biological Condition Gradient (BCG). We first used diatom count data to assign study sites to BCG impairment categories (levels), then determined P and N concentrations corresponding with the boundaries between those levels. We studied diatom counts and environmental data from 95 river and stream sites throughout the state of New Jersey (NJ), USA. The sites represent five ecoregions, primarily forested uplands and coastal plains, and a wide range of nutrient concentrations (total P range of 15 to >200 µg L−1 and total N 0.5 to >4 mg L−1). Advantages of NJ as a study region are the ready availability of streams with a large gradient in nutrient concentrations and similarity to nutrient-stressed systems in many other geographic regions. BCG levels represent a range of ecological conditions from natural to highly impaired. A panel of experts on use of diatoms as ecological indicators assigned 57 study sites to BCG levels based on diatom assemblage composition. Potential nutrient criteria were subsequently derived by determining the measured TP and TN concentrations associated with the boundary between impaired sites and non-impaired sites (BCG levels greater than 4). Based on this approach, statewide criteria of no greater than 50 µg L−1 TP and 1.0 mg L−1 TN are indicated for maintaining or restoring sites to unimpaired condition. In some least-disturbed ecoregions, lower concentrations (e.g., 25 µg L−1 of TP) would be more appropriate to maintain current ecological conditions. Existing diatom TP and TN metric values for the study sites correlate well with BCG level assignments and can be used to determine if nutrient criteria are met. Overall, results demonstrate the usefulness of data derived from diatom assemblages in management of nutrient issues, and the potential widespread applicability of the BCG approach to develop nutrient criteria and to monitor compliance.

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems.

Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. Yet the in situ study of DOM is difficult as the molecular complexity of the DOM pool cannot be easily reproduced for experimental purposes. Nutrient additions to streams however, have been shown to repeatedly alter the in situ and ambient DOM pool. Here we demonstrate an easily replicable field-based method for manipulating the ambient pool of DOM at the ecosystem scale. During nutrient pulse experiments changes in the concentration of both dissolved organic carbon and dissolved organic nitrogen can be examined across a wide-range of nutrient concentrations. This method allows researchers to examine the controls on the DOM pool and make inferences regarding the role and function that certain fractions of the DOM pool play within ecosystems. We advocate the use of this method as a technique to help develop a deeper understanding of DOM biogeochemistry and how it interacts with nutrients. With further development this method may help elucidate the dynamics of DOM in other ecosystems.

Thresholds of copper toxicity to lettuce in field-collected agricultural soils exposed to copper mining activities in Chile

Several previous studies highlighted the importance of using field-collected soils instead of artificially spiked contaminated soils for phytotoxicity tests. However, the use of field-collected soils presents several difficulties for interpretation of results, due to presence of various contaminants in the soil and unavoidable differences in the physicochemical properties of the tested soils. The objective of this study was to estimate thresholds of copper phytotoxicity in topsoils of 27 agricultural areas historically contaminated by mining activities in Chile. We performed standard emergence and early growth (21 days) tests (OECD 208 and ISO 11269-2) with lettuce. The response of lettuce was best explained by Cu toxicity and P deficiency. Growth of lettuce was related to soil total Cu concentration and Olsen-P and was not affected by soluble Cu (extractable by 0.1 M KNO3) or Cu2+ free ion activity of the soil solution. Thus, lettuce has a limited applicability for metal toxicity assessment in metal-contaminated soils, due to sensitivity of its response to P deficiency. However, it was possible to determine toxic thresholds for shoot concentrations of Cu in lettuce for responses of shoot and root length, suggesting that shoot concentrations of Cu in lettuce can be useful as indicators of Cu toxicity even in soils with a wide range of nutrient concentrations.

Chlorophyll a and nutrient distribution around seamounts and islands of the tropical south-western Atlantic

Data collected on two large-scale surveys around the seamounts and islands off north-eastern Brazil during 1997 and 1998 provided information on the distribution of Chlorophyll a and inorganic nutrients. During both surveys, the concentrations of Chlorophyll a and nutrients were highly patchy. The highest measurement of Chlorophyll a was 3.91 µg L–1 during 1997. A wide range of nutrient concentrations were found, from undetectable values to a maximum of 17.52 µm L–1 (Si), 1.37 µm L–1 (PO4), 10.02 µm L–1 (NO3) and 0.72 µm L–1 (NO2). In 1998, concentrations of Chlorophyll a and nutrients (nitrite and nitrate) were far more uniform, with Chlorophyll a concentrations lower and phosphate concentrations generally higher than in 1997. Topography–flow interaction on thermohaline structures was observed around Saint Peter and Saint Paul Archipelago and in the Fernando de Noronha Chain, creating a patchy pattern around the island and seamounts. Nutrients exhibited an inverse linear relationship with temperature and salinity and an exponential decay relationship with Chlorophyll a.

Isolation of oligotrophic yeasts from supraglacial environments of different altitude on the Gulkana Glacier (Alaska)

Psychrophilic yeasts have been isolated from supra- and subglacial ice at many sites worldwide. To understand the ecology of psychrophilic yeasts on glaciers, we focused on their adaptation to wide range of nutrient concentrations and their distribution with altitude on the Gulkana Glacier in Alaska. We found various culturable psychrophilic yeasts on the ice surfaces of the glacier, and 11 species were isolated with incubation at 4 °C in four different dilutions of agar medium. Some of our isolated species (Rhodotorula psychrophenolica, Rhodotorula aff. psychrophenolica, Rhodotorula glacialis, and Basidiomycota sp. 1) can grow on the low dissolved organic matter (DOC) concentrations medium (7.6 mg L(-1)) which is close to the typical level of supraglacial melt water, suggesting that these species can inhabit in any supraglacial meltwater. Otherwise, most of other species were isolated only from higher DOC concentration medium (183 mg L(-1) -18.3 g L(-1)), suggesting that these are inhabitant around the cryoconite, because DOC concentrations in melted surface-ice contained cryoconite is much higher than in melted water. Similarity of altitudinal distribution between culturable yeast and algal biomass suggests that the ecological role played by the cold-adapted yeasts is as organic matter decomposers and nutrient cyclers in glacier ecosystem.

Biomechanical and Nutrient Controls in the Growth of Mammalian Cell Populations

Growth kinetics and morphologies of growing mammalian cell populations are part of the growth dynamics of tumors. A biophysical agent-based simulation model describes a biological cell by a homogeneous elastic adhesive object able to migrate, grow and divide, and die. A comparison of simulation results with experimental data shows that the growth kinetics of growing multicellular spheroids (MCS) over a wide range of nutrient concentrations is explained by a bio-mechanical form of contact inhibition between cells. This inhibition mechanism explains the growth kinetics of the tumor diameter and the cell population size, the size of the necrotic core, the median cell volume, which decreases when the tumor diameter increases, and the spatial distribution of cell volumes in the tumor. The same model is used to predict how cell populations survive in low nutrient concentrations. Spatial patterns are different for changes of the cell phenotype by regulation or mutation. The cells appearing in the simulations decrease cell-cell adhesion, display chemotaxis movement, increase micro-motility and decrease cell cycle time. Each of these have been observed in invasive cancers.

A filamentous green algae-dominated temperate shallow lake: Variations on the theme of clear-water stable states?

Shallow lakes can have two alternative stable states over wide range of nutrient concentrations: a macrophyte-dominated clear-water state and a phytoplankton-dominated turbid-water state. Little Budworth Pool, Cheshire, UK is a small (surface area 3 ha), shallow (max. depth < 1m), clear-water lake with very high nitrate concentrations (annual mean 9.2 mg NO 3 -N 1 -1 ), relatively low phytoplankton growth (annual mean 13.5 μg chlorophyll-a 1 -1 ) and high metaphytic filamentous green algal abundance (FGA, mainly Spirogyra), but without any submerged plant-beds. To understand the mechanism limiting phytoplankton biomass in summer, the lake was sampled every two weeks for two years (November 2001-October 2003) for water chemistry, phytoplankton, zooplankton, benthic macroinvertebrates, FGA and benthic diatoms. Phytoplankton growth was mainly dominated by small species like Cyclotella spp., Chroomonas acuta and Cryptomonas spp., whereas among the zooplankton Cladocera showed high abundance of both small and large species (Bosmina longirostris and Daphnia longispina) especially in summer and autumn. FGA attained highest biomass in the warmer months and showed negative correlations with nitrate-N and total nitrogen concentrations suggesting nutrient removal ability of these plants, but also possible increased denitrification in summer. While phytoplankton growth was negatively correlated with FGA biomass, cladoceran densities were positively related to the latter. A comparison among macrophyte-dominated lakes and FGA-dominated lakes showed similarities among them regarding water clarity, nutrient concentrations, phytoplankton growth and species composition, zooplankton assemblage and abundance, but not for abundance of benthic macroinvertebrates. We suggest that in a lake lacking submerged plants, abundance of FGA may act as a buffer against a forward switch to phytoplankton dominance, thus maintaining a clear-water state. The control of phytoplankton growth was primarily not through FGA removing nutrients from the water because sufficient available nutrients were recorded in water during summer. Rather it was by intense grazing by cladocerans ostensibly supported in refuges provided by FGA.

水耕レタスの無機成分吸収に及ぼす培養液濃度の影響

1. 非結球性のレタス(サラダナ)を材料にし, NFTシステムを用いて, 無機成分吸収に及ぼす培養液濃度の影響を調査した.2. 本試験で採用した無機成分吸収量の測定方法は, イオン交換水を自動補給して, システム内の培養液を一定容量に保持しながら, 培養液濃度の低下速度から求める方法である.本システムによりレタスの無機成分吸収速度に及ぼす培養液の無機成分濃度の短期的な影響が明らかになった.3. レタスのN, P, Kは, いずれの成分の養分吸収速度も, 高濃度から1 me・liter-1程度の低濃度まで広い培養液濃度範囲で, あまり変化しなかった.つまり, レタスのN, P, K吸収速度は培養液濃度に直接的に影響されなかった.4. NH4-N濃度の低下速度は極めて速かったが, これはNH4-Nの吸収濃度比(培養液中の濃度に対するみかけの吸収濃度の比)が他の無機成分に比べて高いことが原因であると考えた.5. N, P, Kの吸収速度が培養液濃度にあまり影響されなかったことから, 養液栽培における培養液管理濃度は現状よりかなり低く設定できると考えられる.

Diversity peaks at intermediate productivity in a laboratory microcosm.

The species diversity of natural communities is often strongly related to their productivity. The pattern of this relationship seems to vary: diversity is known to increase monotonically with productivity, to decrease monotonically with productivity, and to be unimodally related to productivity, with maximum diversity occurring at intermediate levels of productivity. The mechanism underlying these patterns remains obscure, although many possibilities have been suggested. Here we outline a simple mechanism--involving selection in a heterogeneous environment--to explain these patterns, and test it using laboratory cultures of the bacterium Pseudomonas fluorescens. We grew diverse cultures over a wide range of nutrient concentrations, and found a strongly unimodal relationship between diversity and productivity in heterogeneous, but not in homogeneous, environments. Our result provides experimental evidence that the unimodal relationship often observed in natural communities can be caused by selection for specialized types in a heterogeneous environment.

Existence of a macrophyte-dominated clear water state over a very wide range of nutrient concentrations in a small shallow lake

Little Mere, a small shallow lake, has been monitored for four years, since its main source of nutrients (sewage effluent) was diverted. The lake has provided strong evidence for the persistence of a clear water state over a wide range of nutrient concentrations. It had clear water at extremely high nutrient concentrations prior to effluent diversion, associated with high densities of the large body-sized grazer, Daphnia magna, associated with low fish densities and fish predation. Following sewage effluent diversion in 1991, the nutrient concentrations significantly declined, the oxygen concentrations rose, and fish predation increased. The dominance of large body-sized grazers shifted to one of relatively smaller body-sized animals but the clear water state has been maintained. This is probably due to provision of refuges for grazers by large nymphaeid stands (also found prior to diversion). There has been a continued decrease in nutrient concentrations and expansion of the total macrophyte coverage, largely by submerged plants, following effluent diversion. The grazer community of Little Mere has also responded to this latter change with a decline in daphnids and increase in densities of weed-associated grazers. The presence of large densities of such open water grazers was the apparent main buffer mechanisms of the clear water state until 1994. The lake has, so far, maintained its clear water in the absence of such grazers. Thus, new buffer mechanisms appear to operate to stabilize the ecosystem. Little Mere appears to have shifted from previous top-down controlled clear water state to a bottom-up controlled clear water state.

Variations in the distribution of chlorophyll a and inorganic nutrients around South Georgia, South Atlantic

Data collected on four large-scale surveys around the subantarctic island of South Georgia provide information on the variability in the distribution of chlorophyll and inorganic nutrients during the austral summer and winter. During three summer surveys, surface water cholorophyll and nutrient concentrations were highly patchy over scales ranging from a few to hundreds of kilometres. The highest measurement of chlorophyll a was 8 mg m−3 and a wide range of nutrient concentrations were found; 5–32 mmol m−3 NO3−N, 1.1–2.2 mmol m−3 PO4−P and 8–60 mmol m−3 Si(OH)4−Si. In winter, chlorophyll and nutrient levels were far more uniform, with chlorophyll concentrations lower and nutrient concentrations generally higher than in summer. The spatial variability in nutrient concentrations was due to a variety of factors acting over a range of scales, however biological processes appeared most important in creating the mesoscale patchiness around the island. Although phytoplankton abundance and nutrient concentrations were not directly correlated, the scales of variability were clearly similar.