SEASONAL CYCLING OF ALGAL NUTRIENT LIMITATION IN CHAUTAUQUA LAKE,NEW YORK1

Algal nutrient enrichment bioassays were conducted between May 1975 and August 1978 using water samples collected from Chautauqua Lake, New York. Photosynthetic fixation rates of natural phytoplankton assemblages were enhanced by additions of phosphorus and nitrogen, although enrichment with other nutrients had no significant stimulatory effect on algal photosynthesis. Whereas phosphorus stimulated in spring and early summer, both nitrogen and phosphorus enhanced photosynthesis in midsummer and fall. Relative to the effect of phosphorus enrichment, enhancement of photosynthesis by nitrogen during the summer and fall was highest in the northern part of the lake. During the period of ice cover, photosynthesis did not appear to be limited by nutrients in that nutrient additions (P, N, Si, C, Fe, trace metals) did not enhance fixation rates. Observed temporal fluctuations in the response of the algae to P and N correlated with changes in the lake water N:P ratio as well as with temporal changes in dissolved orthophosphate and nitrate-nitrite nitrogen. The N:P ratio decreased drastically in the summer and remained at ca. 10 or less through mid-fall, suggesting that N concentrations were inadequate for the non-N-fixing phytoplankton. Studies over 3 yr indicate that states of P and N limitation undergo time-space fluctuations that occur in a cyclic pattern in the surface waters of Chautauqua Lake.     

Contrasting responses of phytoplankton and benthic algae to recent nutrient enrichment in Arctic tundra ponds

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SALINITY AND NUTRIENT LIMITATIONS ON GROWTH OF BENTHIC ALGAE FROM TWO ALKALINE SALT LAKES OF THE WESTERN GREAT BASIN (USA)1

Enrichment cultures of littoral benthic algae from Mono Lake, California, and Abert Lake, Oregon, were grown under conditions of varied salinity and nutrient content. Field-collected inocula were composed mainly of diatoms and filamentous blue-green and green algae. The yield of long-term cultures (30 days) showed tolerance over a broad salinity range (50–150 g·L^?1) for Mono Lake-derived algae. Algae from Abert Lake had a lower range of tolerance (25–100 g·L^?1) Organic content and pigment concentrations of algae from both lakes were also reduced above the tolerated salinity level. Within the range of salinity tolerance for Mono Lake algae, initial growth rates and organic content were reduced by increased salinity. The effects of macro- and micronutrient enrichment on algal growth in Mono Lake water were also tested. Only nitrogen enrichment (either as ammonium or nitrate) stimulated algal growth. Although the benthic algae cultured here had wide optima for salinity tolerance, the rates of growth and storage were limited by increased salinity within the optimum range. Although the lakes compared had similar species composition, the range and limits of tolerance of the algae were related to salinity of the lake of origin.     

Changes in species composition of phytoplankton due to enrichment by N,P, and Si of water from a North Florida Lake

Water samples were collected from Lake Jackson, near Tallahassee, Florida, and enriched with N, P, N + P, and Si in the laboratory in April, 1969 and January, 1970. After time intervals of 3 and 6 days in April, and 13 days additionally in January, phytoplanktonic algae in the cultures were enumerated as to species composition and cell numbers with an inverted plankton microscope. Controls, to which no nutrients were added, were also maintained to determine changes arising from culture-room conditions. The addition of N and P, alone or in combination, caused increased numbers of algae, along with differences in species composition. This indicated that these two nutrient elements were limiting to production in Lake Jackson besides exerting a chemical control on succession. Si additions increased diatom numbers, but also stimulated Anacystis cyanea to grow in the April sample. Species attributed as indicators of organic pollution were found to be stimulated by inorganic sources of N, P, or Si. Such changes indicated caution must be exercised in interpreting long-term nutrient enrichment experiments using natural phytoplankton communities.     

Nitrogen limitation of the phytobenthos in Alpine lakes: results from nutrient‐diffusing substrata

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Biogenic silica and phosphorus accumulation in sediments as indices of eutrophication in the Laurentian Great Lakes

Biogenic silica (BSi), total phosphorus (TP), and biologically available phosphorus (AVP) were measured in short cores from Lake Michigan, Lake Erie, and Lake Ontario. Peaks in BSi concentration and peaks in BSi:TP or BSi:AVP ratios provided stratigraphic signals of water column silica (Si) depletion as a response of increased diatom production to P enrichment and decreased diatom production resulting from silica depletion. By contrast the stratigraphic record of P accumulation provided very weak signals of the historical nutrient enrichment in the water column. These results indicate that system P recycling has a higher rate constant than Si recycling and, as a consequence, that relatively small levels of P enrichment can increase diatom production and sedimentation eventually causing Si depletion and Si-limited diatom production in the water mass.     

Seasonal Dynamics of Benthic and Planktonic Algae in a Nutrient‐Rich Lowland River (Spree,Germany)

We studied chlorophyll a (chl. a), biovolume and species composition of benthic algae and phytoplankton in the eutrophic lower River Spree in 1996. The chl. a concentration was estimated as 3.5 (2.7–4.5) µg/cm² for epipsammon, 9.4 (7.4–11.9) µg/cm² for epipelon and 6.7 (5.7–7.8) µg/cm² for the epilithon (median and 95% C. L.). The mean total biomass of benthic algae was significantly higher (6.0 µg chl. a/cm²) than the areal chl. a content of the pelagic zone (1.6 µg chl. a/cm²). Although certain phytoplankton taxa were abundant in the periphyton, benthic taxa generally dominated the assemblages. Seasonal dynamics of benthic algae were probably controlled by light and nitrate supply (sand), discharge fluctuations (sand, mud) and invertebrate grazing (stones). This paper shows the importance of benthic algae even in phytoplankton‐rich lowland rivers with sandy or muddy sediments. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Responses of benthic algae to nutrient enrichment in a shallow lake: Linking community production,biomass, and composition

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Benthic algal response to N and P enrichment along a pH gradient

Nutrient enrichment and its effect on benthic algal growth, community composition, and average cell size was assessed across two sites of differing pH within a single habitat. Nutrients were added using in situ substrata, which released either N, P, or no additional nutrients (controls) at each site for 21 days. Upon collection, chlorophyll and biovolume standing stocks of the attached algal microflora were measured. Chlorophyll concentration was different among all treatments, accumulating greatest on P, followed by N, and the least on C substrata (P < 0.001) and was highest at site-2 (P < 0.001), while total algal biovolume was highest on P compared to both N and C substrata (P < 0.05) and did not vary between sites. Increased growth on P substrata was due to the enhanced biovolume of filamentous green algae, although the affected taxa varied between sites. Biovolume to cell density ratios (as a measure of average cell size) were highest on P substrata over both N-enriched and control substrata (P < 0.05) and this pattern was similar between sites. Progression towards a community composed of larger cells following P enrichment observed along this pH gradient, seems to be related to the dominance of larger celled filamentous green algae. Thus, nutrients exhibited greater control on benthic algal growth than did changes in hydrogen ion concentration.Contribution number 581, Great Lakes Environmental Research LaboratoryContribution number 581, Great Lakes Environmental Research Laboratory     

A synoptic study of the limnology of Lake Thonotosassa,Florida

Limnological sampling of Lake Thonotosassa was initiated in 1970 to document current conditions following 15 years of artificial enrichment by organic wastes from primary treated sewage and citrus processing plants, and to provide base-level data for a long-term study of the rates of change following the installation of a secondary sewage treatment facility. Results from the first year of study indicated that the lake was in an advanced state of eutrophy. Inorganic nutrient levels were high; oxygen deficits occurred in the hypolimnion and at the mud-water interface; phytoplankton volumes were large and dominated by blue-green algae; primary productivity rates were comparable with those of grossly polluted lakes; small-bodied herbivores dominated the zooplankton; and benthic invertebrate populations were comprised of an overwhelming abundance of oligochaetes and chironomids. Construction of the new sewage treatment plant reduced the organic load and B. O. D. of the incoming waters and benthic diversity in the inlet subsequently increased. However, in the lake itself decreases in coliform bacteria concentrations were the only signs of immediate influence.     

Production and chlorophyll concentration of epipelic and epilithic algae in fertilized and nonfertilized subarctic lakes

The production and chlorophyll concentration of epipelic and epilithic algae was measured during four years (1972–1975) in two shallow, Swedish subarctic lakes. One lake (Lake Hymenjaure) was fertilized with phosphorus or a combination of phosphorus and nitrogen while the other (Lake Stugsjön) served as a reference. The benthic algae in both lakes were dominated by Cyanophyceae of the same species during the whole investigation. The chlorophyll concentration of epipelic and epilithic algae was 100 and 20 mg·m^–2 respectively and fairly constant during the season. In 1974–1975 there was a significant increase in chlorophyll concentration of the benthic algae in Lake Hymenjaure, probably as a response to the poorer light climate in the lake due to a large phytoplankton development. The annual benthic production was 3.4–7.2 gC·m^–2 and it was not enhanced by the fertilization. Compared to the other primary producers (phytoplankton and macrophytes) the benthic algae constituted 70–83% of the total production in Lake Stugsjön. In Lake Hymenjaure, however, the importance of the benthic algae decreased from 50 to 22% of the total due to the great increase in phytoplankton production induced by the lake fertilization.     

Changes in the abundance of blue-green algae related to nutrient loadings in the nearshore of Lake Michigan

Nutrient loadings to the nearshore of southeastern Lake Michigan have undergone a remarkable reduction. This reduction can affect the nutrient supply and result in biological changes. Changes in phytoplankton community, particularly the blue-green algae, can be related to nutrient changes. After thermal stratification, sudden increases in the blue-green algae population were significantly correlated to soluble reactive phosphorus concentrations. Phosphorus-stimulated low dissolved silica and phosphorus limitations after stratification appear to be primary factors contributing to the success of these algae.     

Effects of light and nutrients on the net accumulation and elemental composition of epilithon in boreal lakes

1. Two experiments in the Experimental Lakes Area (ELA) in north-western Ontario, Canada examined the effects of light and two key elements on the net accumulation and elemental composition of epilithon. In Lake (L) 224, benthic algae were grown under different light intensity and phosphorus supply, while in L302S we provided three levels of two different carbon sources (bicarbonate and glucose) to algae colonizing nutrient-diffusing substrata. After 1 month of accumulation, we sampled biofilms for chlorophyll (chl), carbon (C), phosphorus (P) and algal C.
2. Increased C supply did not significantly affect algal growth (C or chl) or elemental composition (C/P ratios) in L302S. However, P enrichment increased chl and algal C, dramatically reduced the C/P ratio of epilithon, and did not affect total organic C in L224. Phosphorus enrichment also increased the proportion of algal material in the total particulate organic matter and altered the taxonomic composition of algae in L224 biofilms. Shading had no significant effect on the C/P ratio and total organic C in epilithon from the L224 experiment.
3. Our results demonstrate that P supply affects the elemental composition of organic matter that collects on rock substrata. It thus appears that low availability of P relative to C and light drives the formation and retention of high C/P organic matter on rock surfaces in oligotrophic boreal lakes.     

A comparison of natural and human determinants of phytoplankton communities in the Kentucky River basin,USA

Physical, chemical, and biological characteristics of the Kentucky River and its tributaries were assessed for one year to compare effects of seasonal, spatial, and human environmental factors on phytoplankton. Phytoplankton cell densities were highest in the fall and summer and lowest in the winter. Cell densities averaged 1162 (± 289 SE) cells m1^–1. Cell densities were positively correlated to water temperature and negatively correlated to dissolved oxygen concentration and to factors associated with high-flow conditions (such as, suspended sediment concentrations). Chrysophytes, diatoms, and blue-green algae dominated winter, spring, and summer assemblages, respectively. Ordination analyses (DCCA) indicated that variation in taxonomic composition of assemblages was associated with stream size as well as season.Spatial variation in phytoplankton assemblages and effects of humans was investigated by sampling 55 sites in low flow conditions during August. Phytoplankton density increased with stream size. Assemblages shifted in composition from those dominated by benthic diatoms upstream to downstream communities dominated by blue-green algae and small flagellates. Human impacts were assumed to cause higher algal densities in stream basins with high proportions of agricultural or urban land use than in basins with forested/mined land use. While density and composition of phytoplankton were positively correlated to agricultural land use, they were poorly correlated to nutrient concentrations. Phytoplankton diversity changed with water quality: decreasing with nutrient enrichment and increasing with conditions that probably changed species composition or inhibited algal growth. Human impacts on phytoplankton in running water ecosystems were as great or greater than effects by natural seasonal and spatial factors. Our results indicated that phytoplankton could be useful indicators of water quality and ecosystem integrity in large river systems.     

Nutrient limitation in a tropical saline lake: a microcosm experiment

There is increasing evidence that nitrogen limitation is of widespread occurrence in tropical lakes. Nonetheless, data on the deep tropical Lake Alchichica (Mexico) show that dissolved inorganic nitrogen (DIN) to soluble reactive phosphorus (SRP) ratio fluctuates widely. To elucidate further the role of nitrogen and phosphorus limitation on the phytoplankton growth in tropical saline lakes, we present the results of a series of nutrient enrichment experiments with natural assemblages of Lake Alchichica phytoplankton conducted monthly for a year. Our assays indicate that phosphorus and nitrogen alternate in limiting Lake Alchichica phytoplankton biomass. Phosphorous limited phytoplankton growth most (41.7%) of the time, followed by nitrogen (33.3% of the time), and both nutrients for the rest of the time (25.0%). This alternation in nitrogen and phosphorus responsible for phytoplankton growth limitation in Lake Alchichica is attributed to the combination of natural conditions (e.g., young volcanic terrain rich in phosphorus) that would favor nitrogen limitation and anthropogenic impacts (e.g., agricultural nitrogen fertilization) which would cause phosphorus limitation. Guest Editors: J. John & B. Timms Salt Lake Research: Biodiversity and Conservation—Selected papers from the 9th Conference of the International Society for Salt Lake Research     

Comparing Effects of Nutrients on Algal Biomass in Streams in Two Regions with Different Disturbance Regimes and with Applications for Developing Nutrient Criteria

Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations. Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic algal biomass occurred in nutrient concentrations between 10 and 30 μg TP l⁻¹ and between 400 and 1000 μg TN l⁻¹.     

The Role of Substrate Type on Benthic Diatom Assemblages in the Daly and Roper Rivers of the Australian Wet/Dry Tropics

The selection of one or more river substrata for the collection of benthic diatoms is fundamental to any monitoring or research programme because it can potentially bias the diatom data set. In the wet/dry tropics of Australia, where the use of benthic diatoms for river health assessment is in its infancy, the comparability of diatom assemblages on river substrata has been assessed. Benthic diatoms were sampled from seven river sites, with a range of ionic chemistries (conductivities 27–6500 μS cm⁻¹) but low nutrient concentrations. At each site, triplicate samples were collected from 3 to 6 substrata. The diatom assemblages sampled were: epilithon (assemblages on rock), epiphytes on macroalgae and macrophytes, epidendron (assemblages on wood), epipsammon (assemblages on sand), epipelon (assemblages on mud) and bacterial slime. The variability between substrate assemblages, at each site, were assessed according to the following: (1) a multivariate analysis of diatom assemblages, (2) ANOVA tests of species richness, (3) ANOVA tests of the relative abundance of common species (defined by an abundance of at least 10% in any one sample), and (4) a comparison of the number of species unique to a substrate. A total of 198 taxa were identified, with some taxa common to temperate Australia. Common species were found on all substrata, with sometimes statistically significantly different relative abundances. Taxa unique to a substrate had low relative abundances (0.1–2%), were most often found on only one replicate, and are unlikely to be substrate specific because many are known to occur on other substrata. The assemblages on hard substrata, epilithon and epidendron, were found to be most similar. Diatom assemblages on macroalgal and macrophyte substrata, compared to other substrata, were highly variable. This is attributed to the loss of diatoms from grazing and sloughing, followed by recolonisation of newly exposed substrate. Other assemblages, notably epipsammon, were similar to epilithon and epidendron but sometimes differed in their relative abundance of common species. The principal finding of the study was the similarity of the epilithon and epidendron, which are considered to be indistinguishable. Rock and wood hard substrata can be substituted for one another during field surveys, thereby increasing the number of potential sample sites available for monitoring activities that standardise to a hard substrate.     

Nutrient addition effects on chlorophyll a,phytoplankton biomass,and heterocyte formation in Lake Erie’s central basin during 2014–2017: Insights into diazotrophic blooms in high nitrogen water

1. Phosphorus (P) usually is the primary limiting nutrient of phytoplankton biomass, but attention towards nitrogen (N) and trace nutrients, such as iron (Fe), has surfaced. Additionally, N-fixing cyanobacterial blooms have been documented to occur in N-rich, P-poor waters, which is counterintuitive from the paradigm that low N and high P promotes blooms. For example, Lake Erie's central basin has Dolichospermum blooms when nitrate concentrations are high, which raises questions about which nutrient(s) are selecting for Dolichospermum over other phytoplankton and why an N-fixer is present in high N waters?
2. We conducted a 4-year (2014–2017) study in Lake Erie's central basin to determine which nutrient (P, N, or trace nutrients such as Fe, molybdenum [Mo], and boron [B]) constrained chlorophyll concentration, phytoplankton biovolume, and nitrate assimilation using nutrient enrichment bioassays. The enriched lake water was incubated in 1-L bottles in a growth chamber programmed at light and temperatures of in situ conditions for 4–7 days. We also quantified heterocytes when N-fixing cyanobacteria were present.
3. Compared to the non-enriched control, the P-enriched (+P) treatment had significantly higher chlorophyll and phytoplankton biovolume in c. 75% of experiments. Combination enrichments of P with ammonium-N, nitrate-N, Fe, Mo, and B were compared to the +P treatment to determine secondary limitations. +P and ammonium-N and +P nitrate-N resulted in higher chlorophyll in 50% of experiments but higher phytoplankton biovolume in only 25% of experiments. These results show that P was the primary limiting nutrient, but there were times when N was secondarily limiting.
4. Chlorophyll concentration indicated N secondary limitation in half of the experiments, but biovolume indicated only N secondary limitation in 25% of the experiments. To make robust conclusions from nutrient enrichment bioassays, both chlorophyll and phytoplankton biovolume should be measured.
5. The secondary effects of Fe, Mo, and B on chlorophyll were low (<26% of experiments), and no secondary effects were observed on phytoplankton biovolume and nitrate assimilation. However, +P and Fe resulted in more chlorophyll than +P in experiments conducted during Dolichospermum blooms, and +P and B significantly increased the number of heterocytes in Dolichospermum. These results indicate that low Fe availability might select for Dolichospermum, and low B constrains heterocyte formation in the central basin of Lake Erie. Furthermore, these results could apply to other lakes with high N and low P where diazotrophic cyanobacterial blooms occur.

     

Periphyton distribution and abundance on substrata of different size along a gradient of stream trophy de Montréal

In stream, substrata of different size present different degree ofstability, current, erosion, and deposition to colonizingorganisms. In this study, we tested the importance of substratumsize ranging from sand to small boulders for periphytondistribution and abundance. Because trophy strongly affect streamorganisms, we sampled at nine sites chosen to represent the rangeof nutrients typical of Eastern Ontario and Western Québec. Alarge part of the variability in algal biomass (as chlorophyll)among sites was explained by trophy (as seston or totalphosphorus). However, there was also an effect of substratum size.Cobbles had the highest biomass, and gravel the lowest; sand andboulders were intermediate. Assemblages on different substrata weredifferent in taxonomy and life forms. Cyanobacterial colonies andmotile diatoms dominated the finer substrata while adnate andfilamentous algae were more developed on the larger ones.Consequently periphyton on fine sediments was more loosely attachedthan on rocks. Average algal size was not related to substratumsize but increased significantly with trophy confirmingobservations in benthic and planktonic assemblages inlakes.     

PHOSPHORUS,NITROGEN AND THE GROWTH OF ALGAE IN LAKE KINNERET1

The intracellular concentrations of carbon, nitrogen, phosphorus and chlorophyll a of phytoplankton and zooplankton in Lake Kinneret were determined from 1969 to 1973. The ratios C:P, C:N, chlorophyll a:P, chlorophyll a:N of the algae showed fluctuations which could be related to the nutrient conditions that influence the annual pattern of phytoplankton development, especially in respect to the dinoflagellate bloom of Peridinium cinctum (OFM) Ehr. f. westii (Lemm.) Lef. Relatively high intracellurar P values at the start of the bloom indicated adequate availability of this nutrient and luxury consumption over a short period of time. Later, Peridinium continued to grow despite unusually high C:P ratios (> 300:1). In most years, phosphorus may have eventually limited growth, however, in 1970, the bloom censed despite comparatively high intracellular P concentrations. These observations, together with supplementary evidence from nutrient addition experiments and determinations of specific alkaline phosphatase levels, indicated that, for most of the growth phase of the bloom, Peridinium cells were not directly limited by P. The decline of the bloom usually, but not always (e.g., in 1970), was marked by very high C:P ratios. Thus, a shortage of P may often be a contributory factor to the cessation of the Peridinium bloom and may be limiting phytoplankton growth in the fall. Over the years 1969–73, possibly due to an overall drop in salinity, there appears to be a trend to lower levels of biologically bound phosphorus in Lake Kinneret, without a concomitant decrease in carbon biomass.