Phosphorus Limitation Of Phytoplankton Growth Research Articles

Nitrogen and phosphorus limitation of phytoplankton growth in different areas of Lake Taihu, China

Lake Taihu has attracted attention worldwide because of its extensive cyanobacterial blooms in the warm season. A better understanding of nutrient controls over phytoplankton is critical if the blooms are to be controlled. In the present study, we investigated the effects of nutrient addition on the growth of phytoplankton collected from Meiliang Bay (Station 1), Lake Center (Station 2), and Xukou Bay (Station 3) in July and September 2011. Cyanophyta was dominant in all water samples. Nevertheless, we observed higher proportions of other phyla and lower concentrations of microcystin-LR in September than in July. Further, Station 3 possessed many fewer Cyanophyta, but disproportionately higher concentrations of microcystin-LR than the other two stations. The overall phytoplankton biomass decreased in the order Station 1 > Station 2 > Station 3 and July > September. More interestingly, phosphorus-induced phytoplankton growth coincided with a distinct drop in particulate organic carbon (or nitrogen) to phosphorus ratio at Stations 2 and 3. By contrast, nitrogen, applied either alone or together with phosphorus, had negligible effect on phytoplankton growth. These results suggest that phytoplankton at Stations 2 and 3 were limited by phosphorus and no nutrient limitation occurred at Station 1. Therefore, nutrient limitation in Lake Taihu may be more dynamic and sporadic than previously thought and has implications for management of phytoplankton blooms.

Factors Affecting Nutrient Concentration and Stable Carbon and Nitrogen Isotope Ratio of Particulate Organic Matter in the Ishikari River System, Japan

Water and particulate organic matter samples were analyzed for dissolved nutrients and stable carbon and nitrogen isotope ratio, respectively, in the Ishikari River system, from August 2009 to July 2010. Dissolved nutrient concentration showed significant spatial and seasonal variations within the river system. Mean concentration and standard deviation of ammonium, nitrite, nitrate, phosphate, silica, and dissolved organic carbon were 0.17 ± 0.17, 0.01 ± 0.01, 0.93 ± 0.59, 0.03 ± 0.01, 9.07 ± 2.40, and 3.7 ± 0.93 (mg l−1), respectively. The δ 13C, δ 15N, and molar C/N ratio of particulate organic matter samples ranged from −34.6 to −24.6‰, −4.8 to 15.8‰, and 5.3 to 17.8, respectively, in the Ishikari River system. Nutrient concentration showed increasing trend during the past 50 years owing to increased urban growth and development taking place in the river basin. The molar ratio of dissolved inorganic nitrogen (DIN)/dissolved inorganic phosphate (DIP) was higher than the Redfield ratio (16:1), which implies phosphorus limitation of phytoplankton growth in the river water. The negative value of the indicator of coastal eutrophication potential for nitrogen for the Ishikari River system indicated the absence of eutrophication problem in its coastal areas. Annual nutrient fluxes from Ishikari River for dissolved inorganic nitrogen (DIN-N), phosphate (PO4-P), dissolved silica (SiO2-Si), and dissolved organic carbon (DOC-C) were 1.6 × 104, 379, 13.2 × 104, and 5.4 × 104 t year−1, respectively.

Atmospheric phosphorus deposition may cause lakes to revert from phosphorus limitation back to nitrogen limitation

Recent findings indicate that increased atmospheric deposition of nitrogen of human origin has caused changes in the pattern of ecological nutrient limitation in lakes in the northern hemisphere. An increase in the nitrogen to phosphorus ratio, and hence a shift from pristine nitrogen limitation to human-induced phosphorus limitation of phytoplankton growth, seems to have been driven by deposition of atmospheric nitrogen. These findings challenge the classical paradigm of lake phytoplankton productivity being naturally limited by phosphorus availability. However, atmospheric phosphorus deposition may also be highly relevant. Here we show how dissolved inorganic nitrogen concentration has decreased in the Pyrenean lake district over recent decades, despite there being an increase in deposition of atmospheric nitrogen. This is related to an increased atmospheric phosphorus load in the lake water, as a result of higher atmospheric inputs. These changes are causing phytoplankton to revert from being phosphorus-limited to being nitrogen-limited.

Decrease in anthropogenic nutrients and its effect on the C/N/P molar ratio of suspended particulate matter in hypertrophic Dokai Bay (Japan) in summer

Biologically important nutrient concentrations in Dokai Bay have declined as a result of reductions in anthropogenic inputs of total nitrogen and total phosphorus. A decrease in nutrient concentrations affects phytoplankton growth, thereby changing the biochemical characteristics of autochthonous particulate matter. We therefore investigated changes in the C/N/P molar ratio of suspended particulate matter (SPM) in the summer, when phytoplankton growth is vigorous, before environmental quality standards (EQSs) were attained (1995–1998) and afterward (2006–2009). We found that the ratio of particulate organic nitrogen (PON) to particulate phosphorus (PP) changed in conjunction with changes in the ratio of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIP) that resulted from reductions in nutrient loading. Furthermore, we suggest that because the DIP concentration in seawater was high before EQSs were attained, inorganic phosphorus was possibly adsorbed onto SPM. After the attainment of EQSs, however, the DIP concentration fell, and PON/PP was high. Phosphorus limitation of phytoplankton growth in the mouth of the bay may explain the high PON/PP ratios after EQS attainment.

Nitrogen and Phosphorus Limitation of Phytoplankton Growth in New Zealand Lakes: Implications for Eutrophication Control

We examine macronutrient limitation in New Zealand (NZ) lakes where, contrary to the phosphorus (P) only control paradigm, nitrogen (N) control is widely adopted to alleviate eutrophication. A review of published results of nutrient enrichment experiments showed that N more frequently limited lake productivity than P; however, stoichiometric analysis of a sample of 121 NZ lakes indicates that the majority (52.9%) of lakes have a mean ratio of total nitrogen (TN) to total phosphorus (TP) (by mass) indicative of potential P-limitation (>15:1), whereas only 14.0% of lakes have mean TN:TP indicative of potential N-limitation (<7:1). Comparison of TN, TP, and chlorophyll a data between 121 NZ lakes and 689 lakes in 15 European Union (EU) countries suggests that at the national scale, N has a greater role in determining lake productivity in NZ than in the EU. TN:TP is significantly lower in NZ lakes across all trophic states, a difference that is driven primarily by significantly lower in-lake TN concentrations at low trophic states and significantly higher TP concentrations at higher trophic states. The form of the TN:TP relationship differs between NZ and the EU countries, suggesting that lake nutrient sources and/or loss mechanisms differ between the two regions. Dual control of N and P should be the status quo for lacustrine eutrophication control in New Zealand and more effort is needed to reduce P inputs.

The role of inorganic nutrients and dissolved organic phosphorus in the phytoplankton dynamics of a Mediterranean bay: A modeling study

The effect of Dissolved Organic Phosphorus (DOP) availability and nutrient limitation of phytoplankton growth in an estuarine bay (Alfacs Bay, NW Mediterranean) have been studied by means of a zero-dimensional ecological model including nitrogen, phosphorus (organic and inorganic), two groups of phytoplankton (diatoms and flagellates), one group of zooplankton, and detritus. Simulations with and without DOP as an extra source of phosphorus for phytoplankton growth suggest that DOP plays an important role in the dynamics of the Alfacs Bay ecosystem. DOP is indeed necessary to simulate the observed draw-down of nitrate and build up of phytoplankton biomass. Two non-exclusive mechanisms allowing DOP availability for phytoplankton are possible: direct uptake, or remineralization to Dissolved Inorganic Phosphorus. Including both gives a better agreement with the observations. Inclusion of DOP in the model leads to predominance of phosphorus limitation of phytoplankton growth in fall and winter, and of nitrogen limitation in late spring and summer. Simulations with and without sediment resuspension suggest that this process does not significantly affect the nutrient budget in the bay.

Nitrogen versus phosphorus limitation of phytoplankton growth in Ten Mile Creek, Florida, USA

Ten Mile Creek (TMC) is a major tributary of the Indian River Lagoon (IRL), one of the largest and most ecologically diverse estuaries of the east coast of Florida. Recent algal blooms within the IRL have focused attention on the role of different watersheds playing in the supply of growth-limiting nutrients. The goal of this study was to determine the nutrient-limiting status of the TMC outflow, which is influenced by both agricultural input and urban development. Four laboratory experiments were conducted with water samples from TMC, adding different concentrations of phosphorus (P) and nitrogen (N) under controlled conditions. The results showed that turbidity and phytoplankton biomass (in terms of chlorophyll a concentration) in TMC water samples were responsive to N additions. Turbidity and phytoplankton biomass increased with addition of available N, but were not affected by addition of reactive P. The results indicate that available N is the limiting nutrient for the growth of phytoplankton in the TMC.

Phosphorus and nitrogen cyclings in the pelagic system of hiroshima bay: Results of numerical model simulation

A numerical ecosystem model expressing both phosphorus and nitrogen cyclings in the pelagic system of Hiroshima Bay, Japan, was developed in order to investigate the seasonal variations of these elements and their annual budgets. Based on the geophysical and chemical structures of the bay, Hiroshima Bay was divided into northern and southern boxes, themselves divided into two layers of an upper 5 m and a lower layer according to the stratification of the water column. The model consists of equations representing all relevant physical and biological processes. The results revealed that the internal regeneration of materials was an important source of bioavailable nutrients for phytoplankton growth in the water column. The incorporation of phytoplankton aggregation improved the accuracy of the outputs in comparison to the observed data, especially during the stratified summer season. The results also indicated that phosphorus limitation of phytoplankton growth occurs in the upper layer during summer while light limitation occurs in the lower layer. In addition, physical processes such as diffusion and advection were also important as they ensured that most of regenerated nutrients in the lower layer were transported to the upper layer. Thus, these processes might support the high primary production and the production of oysters that are extensively cultured in this bay. Considering the informative results obtained, the model used in this study provides a sound basis and tool to describe the dynamics of phosphorus and nitrogen cyclings in Hiroshima Bay.

Global patterns of dissolved N, P and Si in large rivers

The concentration of dissolved inorganic nitrogen (DIN), dissolved nitrate-N, Total-N (TN), dissolved inorganic phosphate (DIP), total phosphorus (TP), dissolved silicate-Si (DSi) and their ratios in the world's largest rivers are examined using a global data base that includes 37% of the earth's watershed area and half its population. These data were compared to water quality in 42 subbasins of the relatively well-monitored Mississippi River basin (MRB) and of 82 small watersheds of the United States. The average total nitrogen concentration varies over three orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations in dissolved nitrate concentration, rather than particulate or dissolved organic matter or ammonium. There is also a direct relationship between the DIN:DIP ratio and nitrate concentration. When nitrate-N exceeds 100 μg-at l−1, the DIN:DIP ratio is generally above the Redfield ratio (16:1), which implies phosphorus limitation of phytoplankton growth. Compared to nitrate, the among river variation in the DSi concentration is relatively small so that the DSi loading (mass/area/time) is largely controlled by runoff volume. The well-documented influence of human activities on dissolved inorganic nitrogen loading thus exceeds the influences arising from the great variability in soil types, climate and geography among these watersheds. The DSi:nitrate-N ratio is controlled primarily by nitrogen loading and is shown to be inversely correlated with an index of landscape development – the “City Lights” nighttime imagery. Increased nitrogen loading is thus driving the world's largest rivers towards a higher DIN:DIP ratio and a lower DSi:DIN ratio. About 7.3 and 21 % of the world's population lives in watersheds with a DSi:nitrate-N ratio near a 1:1 and 2:1 ratio, respectively. The empirical evidence is that this percentage will increase with further economic development. When the DSi:nitrate-N atomic ratio is near 1:1, aquatic food webs leading from diatoms (which require silicate) to fish may be compromised and the frequency or size of harmful or noxious algal blooms may increase. Used together, the DSi:nitrate-N ratio and nitrate-N concentration are useful and robust comparative indicators of eutrophication in large rivers. Finally, we estimate the riverine loading to the ocean for nitrate-N, TN, DIP, TP and DSi to be 16.2, 21, 2.6, 3.7 to 5.6, and 194 Tg yr−1, respectively.

Factors Affecting the Abundance of Phytoplankton in a Restricted Subtropical Lagoon, the Indian River Lagoon, Florida, USA

Phytoplankton dynamics in the Indian River Lagoon was examined from the point of view of several key controlling factors, including: nutrient limitation, light availability, temperature, wind, hydrodynamic restriction and grazing. Water was collected at eight sampling sites in the lagoon on a monthly basis for a two and a half year period. Samples were analysed for nutrient content and phytoplankton abundance. Site measurements of salinity and light extinction were made at all sites. Regional data on rainfall, wind and water temperature was obtained for correlation analyses. Bioassays were performed to determine nutrient limiting status and a series of preliminary grazing experiments were carried out on selected samples. The results indicate that the Indian River Lagoon is a nutrient-rich environment where phytoplankton standing crops are often held below their potential by several key loss functions, including hydraulic flushing and grazing. Spatial patterns of phytoplankton abundance generally reflected the degree of restriction to water turnover in different regions of the lagoon, with higher mean abundances in restricted regions. Spatial and temporal patterns of nutrient content and limitation suggest that patterns of external nutrient loading also play a significant role in phytoplankton dynamics. High phosphorus levels in the southern portion of the lagoon contribute to the predominance of nitrogen limitation in the region. In contrast, relatively high N/P ratios in the northern portions of the lagoon contribute to greater potential for phosphorus limitation of phytoplankton growth. As might be expected from the subtropical location of the lagoon, temporal patterns of phytoplankton abundance appear to be less strictly dependent on season than in temperate habitats, and more closely linked to variations in weather conditions, like rainfall (including storm events). The latter considerations bring into play issues like temporal variation in salinity and wind-induced mixing. The high light flux and shallow depth in the lagoon also presents the potential for photoinhibition.

Development and Parameterization of a Kinetic Framework for Modeling Light- and Phosphorus- Limited Phytoplankton Growth in Cannonsville Reservoir

ABSTRACT A mechanistic framework for simulating phytoplankton growth kinetics in lakes and reservoirs is described. The framework is based on published physiological submodels describing light- and phosphorus-limitation of phytoplankton growth and the relationship between the rates of growth and respiration. The physiological submodels were tested and related kinetic coefficients defined through a program of field measurement and laboratory experimentation. Values for kinetic coefficients were determined using the natural phytoplankton assemblage of Cannonsville Reservoir, a part of the New York City drinking water supply system. The suite of submodels was shown to satisfactorily represent the phytoplankton response to variation in the light and nutrient regime of the reservoir. Efforts to test submodels and determine kinetic coefficients on a site-specific basis are believed to enhance the credibility and reliability of the model framework in its application for water quality management.

Plankton and water chemistry in Lake Njupfatet before and after liming

Moderately acidified Lake Njupfatet was studied during 2 consecutive years, before and after liming (calcite), and compared with corresponding data from six reference lakes. After liming, the concentration of total phosphorus in the lake water decreased by some 30% as did the concentrations of particulate carbon, particulate nitrogen, particulate phosphorus, and phytoplankton biomass. Because of significant increases of inorganic nitrogen and dissolved organic carbon, the concentrations of total nitrogen and total organic carbon remained unchanged after liming. Before liming, there was a close balance between phosphorus and nitrogen limitation of phytoplankton growth, but we conclude that after liming the reduced concentrations of phosphorus induced phosphorus limitation of phytoplankton growth. Liming changed the phytoplankton community structure, most importantly causing the complete loss of the dominant species before liming, the cyanophyte Merismopedia tenuissima. The decrease in total biomass of phytoplankton was not compensated for by a corresponding increase in other species. After liming total biomasses of bacterioplankton and protozoan zooplankton did not change, while total biomass of metazoan zooplankton increased; hence, total plankton community carbon remained unchanged. Phytoplankton, protozoan, and metazoan zooplankton diversity (Shannon index) did not change after liming. Zooplankton biomass remained heavily dominated by calanoid copepods, typical of acidified lakes.

Nutrient Flux in a Landscape: Effects of Coastal Land Use and Terrestrial Community Mosaic on Nutrient Transport to Coastal Waters

Long-term interdisciplinary studies of the Rhode River estuary and its watershed in the mid-Atlantic coastal plain of North America have measured fluxes of nitrogen and phosphorus fractions through the hydrologically-linked ecosystems of this landscape. These ecosystems are upland forest, cropland, and pasture; streamside riparian forests; floodplain swamps; tidal brackish marshes and mudflats; and an estuarine embayment. Croplands discharged far more nitrogen per hectare in runoff than did forests and pastures. However, riparian deciduous hardwood forest bordering the cropland removed over 80 percent of the nitrate and total phosphorus in overland flows and about 85 percent of the nitrate in shallow groundwater drainage from cropland. Nevertheless, nutrient discharges from riparian forests downslope from croplands still exceeded discharges from pastures and other forests. The atomic ratio of nitrogen to phosphorus discharged from the watersheds into the estuary was about 9 for total nutrients and 6 for inorganic nutrient fractions. Such a low N:P ratio would promote nitrogen rather than phosphorus limitation of phytoplankton growth in the estuary. Estuarine tidal marshes trapped particulate nutrients and released dissolved nutrients. Subtidal mudflats in the upper estuary trapped particulate P, released dissolved phosphate, and consumed nitrate. This resulted in a decrease in the ratio of dissolved inorganic N:P in the estuary. However, the upper estuary was a major sink for total phosphorus due to sediment accretion in the subtidal area. Bulk precipitation accounted for 31 percent of the total nongaseous nitrogen influx to the landscape, while farming accounted for 69 percent. Forty-six percent of the total non-gaseous nitrogen influx was removed as farm products, 53 percent either accumulated in the watershed or was lost in gaseous forms, and 1 percent entered the Rhode River. Of the total phosphorus influx to the landscape, 7 percent was from bulk precipitation and 93 percent was from farming. Forty-five percent of the total phosphorus influx was removed as farm products, 48 percent accumulated in the watershed, and 7 percent entered the Rhode River. These nitrogen and phosphorus discharges into the Rhode River, although a small fraction of total loadings to the watershed, were large enough to cause seriously overenriched conditions in the upper estuary.

GROWTH RATE VARIATION IN THE N:P REQUIREMENT RATIO OF PHYTOPLANKTON1

ABSTRACTTheoretical considerations predict that the cell N:P ratio at transition from nitrogen limitation to phosphorus limitation of phytoplankton growth (critical ratio, Rc) varies, as a function of population growth rate. This prediction is confirmed by experimental, data from the literature along with new experimental data for the marine, prymnesiophyte Pavlova lutheri (Droop) Green. Rc passes through a maximum at intermediate growth rates for the three phytoplankton species for which data, are available, but there is significant interspecific variability in its value. There is no theoretical or experimental evidence to support the idea that the ratio of subsistence N and P cell quotas is equal to Rc over the range of growth rates, or that the subsistence quota ratio equals the ratio of the N and P cell quotas minus a storage fraction. Examination of N:P composition ratios can be used to determine which nutrient is limiting, but cannot be used to determine relative growth rates or competitive advantage between species limited by the same nutrient. Growth rates are determined by environmental conditions and by the cell quota of the limiting nutrient, without reference to the cell quota of the non‐limiting nutrient.

Alkaline phosphatase activity in the Laholm Bay, south-eastern Kattegat

Measurements of alkaline phosphatase activity (APA) and experimental investigations of limiting nutrients for phytoplankton biomass formation were performed using water from Laholm Bay, SE Kattegat. Alkaline phosphatase activity was insignificant during the autumn and spring phytoplankton blooms which indicates that phosphorus is not a limiting nutrient for phytoplankton growth in the area. Nitrogen additions greatly increased chlorophyll production in the enrichment experiments during the spring bloom, and to a lesser extent the rest of the year. Water from rivers entering the Laholm Bay greatly stimulated phytoplankton growth when mixed with Laholm Bay water. APA increased in flasks with river water additions indicating phosphorus limitation of phytoplankton growth. The results are explained by the high N/P ratio in river water and low ratio in Bay water.