Controls on phytoplankton physiology in Lake Ontario during the late summer: evidence from new fluorescence methods

2007 ◽  
Vol 64 (1) ◽  
pp. 58-73 ◽  
Author(s):  
Katharine L Pemberton ◽  
Ralph EH Smith ◽  
Greg M Silsbe ◽  
Todd Howell ◽  
Susan B Watson
Keyword(s):  
Anthropogenic Disturbance ◽  
Late Summer ◽  
Lake Ontario ◽  
Lower Surface ◽  
Nutrient Ratios ◽  
Surface Mixed Layer ◽  
P Deficiency ◽  
Photosynthetic Physiology ◽  
Physiological Variations

Fast repetition rate fluorescence (FRRF) and spectral fluorescence, together with measures of nutrients and pigments, were used to characterize the composition and photosynthetic physiology of Lake Ontario phytoplankton in late summer and relate them to environmental conditions. Two stations demonstrated effects from relatively heavy anthropogenic disturbance and showed that the response of phytoplankton physiology to different impacts is highly variable. Other stations were more similar in phytoplankton composition, and in situ fluorescence yields ([Formula: see text]) in the lower surface mixed layer suggested good physiological condition (0.45–0.50). Nutrient ratios and mean irradiance indicated a general state of light saturation and slight phosphorus (P) deficiency, but physiological variations among stations were unrelated to measures of P deficiency. Fluorescence yields often decreased when surface layer samples were held in the dark, consistent with an induction of chlororespiration and prior exposure to supersaturating levels of irradiance. Comparative estimates of photosynthesis by FRRF and 14C revealed disparities suggestive of substantial differences between in situ and incubation methods, while spectral fluorescence appeared to underestimate cyanobacterial abundance. FRRF parameters, particularly [Formula: see text], were effective in identifying higher-impact stations and showed promise as an efficient means of characterizing variations in phytoplankton condition that may underlie phenomena such as taste and odour production.

scholarly journals Characteristics of the Exchange Flow of the Bay of Quinte and Its Sheltered Embayments with Lake Ontario

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1857
Author(s):  
Jennifer A. Shore
Keyword(s):  
Bottom Water ◽  
Late Summer ◽  
Lake Ontario ◽  
Exchange Flow ◽  
3 Dimensional ◽  
Flushing Rate ◽  
Algae Growth ◽  
In Situ Observations ◽  
Water Speed

The nature of the exchange flow between the Bay of Quinte and Lake Ontario has been studied to illustrate the effects of the seasonal onset of stratification on the flushing and transport of material within the bay. Flushing is an important physical process in bays used as drinking water sources because it affects phosphorous loads and water quality. A 2-d analytical model and a 3-dimensional numerical coastal model (FVCOM) were used together with in situ observations of temperature and water speed to illustrate the two-layer nature of the late summer exchange flow between the Bay of Quinte and Lake Ontario. Observations and model simulations were performed for spring and summer of 2018 and showed a cool wedge of bottom water in late summer extending from Lake Ontario and moving into Hay Bay at approximately 3 cm/s. Observed and modelled water speeds were used to calculate monthly averaged fluxes out of the Bay of Quinte. After the thermocline developed, Lake Ontario water backflowed into the Bay of Quinte at a rate approximately equal to the surface outflow decreasing the flushing rate. Over approximately 18.5 days of July 2018, the winds were insufficiently strong to break down the stratification, indicating that deeper waters of the bay are not well mixed. Particle tracking was used to illustrate how Hay Bay provides a habitat for algae growth within the bay.

Photoinhibition of DCMU-Enhanced Fluorescence in Lake Ontario Phytoplankton

1987 ◽  
Vol 44 (12) ◽  
pp. 2144-2154 ◽  
Author(s):  
M. Putt ◽  
G. P. Harris ◽  
R. L. Cuhel
Keyword(s):  
Vertical Mixing ◽  
Natural Populations ◽  
Bright Light ◽  
Euphotic Zone ◽  
Lake Ontario ◽  
Enhanced Fluorescence ◽  
Low Light ◽  
Light Levels ◽  
Phosphorus Status

Measurement of 1-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) enhanced fluorescence (FDCMU) suggested that photoinhibition of photosynthesis was frequently an artifact of in situ bottle incubations in Lake Ontario phytoplankton. In a seasonal study, FDCMU of all populations was depressed by bright light in an incubator. However, when the euphotic zone did not exceed the depth of the mixed layer, vertical transport of phytoplankton into either low-light or dark regions apparently allowed reversal of photoinhibition of FDCMU. Advantages of FDCMU as a bioassay of vertical mixing include rapidity of response time, ease of measurement in the field, and insensitivity of this parameter to changes in phosphorus status of the population. Because of seasonal changes in the photoadaptive response of natural populations, the rate constants and threshold light levels required to cause the response must be determined at each use if the method is to be quantitative.

scholarly journals Concentrations, ratios, and sinking fluxes of major bioelements at Ocean Station Papa

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Montserrat Roca-Martí ◽  
Claudia R. Benitez-Nelson ◽  
Blaire P. Umhau ◽  
Abigale M. Wyatt ◽  
Samantha J. Clevenger ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Late Summer ◽  
Euphotic Zone ◽  
Particulate Phosphorus ◽  
Particulate Nitrogen ◽  
Sinking Particles ◽  
Ocean Station Papa ◽  
Particle Size Classes

Fluxes of major bioelements associated with sinking particles were quantified in late summer 2018 as part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign near Ocean Station Papa in the subarctic northeast Pacific. The thorium-234 method was used in conjunction with size-fractionated (1–5, 5–51, and >51 μm) concentrations of particulate nitrogen (PN), total particulate phosphorus (TPP), biogenic silica (bSi), and particulate inorganic carbon (PIC) collected using large volume filtration via in situ pumps. We build upon recent work quantifying POC fluxes during EXPORTS. Similar remineralization length scales were observed for both POC and PN across all particle size classes from depths of 50–500 m. Unlike bSi and PIC, the soft tissue–associated POC, PN, and TPP fluxes strongly attenuated from 50 m to the base of the euphotic zone (approximately 120 m). Cruise-average thorium-234-derived fluxes (mmol m–2 d–1) at 120 m were 1.7 ± 0.6 for POC, 0.22 ± 0.07 for PN, 0.019 ± 0.007 for TPP, 0.69 ± 0.26 for bSi, and 0.055 ± 0.022 for PIC. These bioelement fluxes were similar to previous observations at this site, with the exception of PIC, which was 1 to 2 orders of magnitude lower. Transfer efficiencies within the upper twilight zone (flux 220 m/flux 120 m) were highest for PIC (84%) and bSi (79%), followed by POC (61%), PN (58%), and TPP (49%). These differences indicate preferential remineralization of TPP relative to POC or PN and larger losses of soft tissue relative to biominerals in sinking particles below the euphotic zone. Comprehensive characterization of the particulate bioelement fluxes obtained here will support future efforts linking phytoplankton community composition and food-web dynamics to the composition, magnitude, and attenuation of material that sinks to deeper waters.

Effects of age and state of incisor dentition on faecal output of dry matter and on faecal and urinary output of nitrogen and minerals, of sheep grazing hill pastures

1974 ◽  
Vol 83 (1) ◽  
pp. 151-160 ◽  
Author(s):  
A. C. Field ◽  
A. R. Sykes ◽  
R. G. Gunn
Keyword(s):  
Body Weight ◽  
Urine Volume ◽  
Late Summer ◽  
The Body ◽  
The Other ◽  
Urinary Output ◽  
Sheep Grazing ◽  
Total N ◽  
P Deficiency ◽  
Daily Intakes

SUMMARYExcretion of D.M., N, Ca, P and Mg in faeces, and N, P and Mg in urine were measured at intervals over 12 months in breeding Scottish Blackface sheep grazing hill pastures. These values were used with data on reproductive performance and body compositional changes, to calculate the energy, nitrogen and mineral balances. The sheep were: 11 6½-year-old with sound mouths (SM), 16 6½-year-old with broken mouths (BM), 16 5½-year-old with all permanent incisors clipped to gum level (CM) and 16 2½-year-old (Y). An energy supplement was given at the end of gestation and during early lactation. All faeces were collected and creatinine was used as an internal marker to estimate urine volume.Faecal D.M. output ranged from 443 to 662 g/day, with highest values in November and lowest in May. Average values for the BM sheep were lower than those for the other groups but when output was expressed as a power function of body weight, the values for the Y sheep were 15% higher than those for the other groups. Faecal excretions of Ca and P in January and February were very low and the values for P were half the expected endogenous faecal loss.Urinary output ofN ranged from 6·0 g/day in February to 22·2 g/day in August and the corresponding urinary urea N: total N ratios were 0·24 and 0·69. Urinary Mg output was highest in late summer and early winter but urinary P showed no consistent trends.The estimated daily intakes of DOM (g) were 936 in November 1969, 599 in January, 414 in February, 1075 in May, 1150 in August and 946 in November 1970.The loss of energy from the body between mating (November) and mid-lactation (June) ranged from 9·5 to 16·8% of the total calculated ME requirements in the Y and BM sheep, respectively. Maintenance requirements averaged 204 kJ/kg body weight/day and the value for the Y sheep was 12% higher than the mean for the older sheep.Nitrogen and mineral balances were calculated for February, May, August and November. The sheep were protein-deficient in winter, not from a shortage of crude protein in the diet but because of its low digestibility (34%). Intakes of Ca and P in winter were low and a real possibility of a P deficiency exists. Estimates of the concentrations of N and of minerals in the herbage consumed by the sheep were made and compared with those obtained for cut herbage from the same pastures. It would appear that the sheep selected herbage of a higher protein content than that of the cut herbage. Herbage selection was greatest in November.

scholarly journals Mechanisms of Barrier Layer Formation and Erosion from In Situ Observations in the Bay of Bengal

2019 ◽  
Vol 49 (5) ◽  
pp. 1183-1200 ◽  
Author(s):  
Jenson V. George ◽  
P. N. Vinayachandran ◽  
V. Vijith ◽  
V. Thushara ◽  
Anoop A. Nayak ◽  
...  
Keyword(s):  
Time Series ◽  
Barrier Layer ◽  
Bay Of Bengal ◽  
High Salinity ◽  
Layer Structure ◽  
Surface Mixed Layer ◽  
Study Region ◽  
In Situ Observations ◽  
Differential Advection

AbstractDuring the Bay of Bengal (BoB) Boundary Layer Experiment (BoBBLE) in the southern BoB, time series of microstructure measurements were obtained at 8°N, 89°E from 4 to 14 July 2016. These observations captured events of barrier layer (BL) erosion and reformation. Initially, a three-layer structure was observed: a fresh surface mixed layer (ML) of thickness 10–20 m; a BL below of 30–40-m thickness with similar temperature but higher salinity; and a high salinity core layer, associated with the Summer Monsoon Current. Each of these three layers was in relative motion to the others, leading to regions of high shear at the interfaces. However, the destabilizing influence of the shear regions was not enough to overcome the haline stratification, and the three-layer structure was preserved. A salinity budget using in situ observations suggested that during the BL erosion, differential advection brought high salinity surface waters (34.5 psu) with weak stratification to the time series location and replaced the three-layer structure with a deep ML (~60 m). The resulting weakened stratification at the time series location then allowed atmospheric wind forcing to penetrate deeper. The turbulent kinetic energy dissipation rate and eddy diffusivity showed elevated values above 10−7 W kg−1 and 10−4 m2 s−1, respectively, in the upper 60 m. Later, the surface salinity decreased again (33.8 psu) through differential horizontal advection, stratification became stronger and elevated mixing rates were confined to the upper 20 m, and the BL reformed. A 1D model experiment suggested that in the study region, differential advection of temperature–salinity characteristics is essential for the maintenance of BL and to the extent to which mixing penetrates the water column.

II.—On upright Equisetites Stems in the Oolitic Sandstone in Yorkshire

1913 ◽  
Vol 10 (1) ◽  
pp. 3-7 ◽  
Author(s):  
T. G. Halle
Keyword(s):  
Lower Surface ◽  
Upright Position ◽  
The Other ◽  
Mineral Matter ◽  
Vertical Position ◽  
Other Hand ◽  
Mode Of Occurrence ◽  
Coal Measures

Stems of Ecquisetites columnaris (Brong.) have long been known to occur in a vertical position in the sandstones of the Inferior Oolite on the Yorkshire coast. This mode of occurrence has commonly been held as proving that the stems are preserved in the position in which they once grew, having been buried in situ beneath the layers of sand that accumulated on the spot. On the other hand, it has been argued that the upright position need not be primary; it might be as readily explained if the stems are regarded as drifted and secondarily deposited on the spots where they are now found. It is well known and has been pointed out, particularly in the discussions of the upright stems in the Coal-measures, that a drifting tree often has a tendency to sink in a vertical position, the root-end being heavier because of adhering mineral matter or from some other reason. Phillips describes, in his Geology of the Yorkshire Coast, a locality at High Whitby where upright stems of Equisetites columnaris occur in the sandstone. He continues: “They … are broken off or imperfect above, and seldom reach to the upper surface of the bed; they are also broken off below, but commonly pass to the lower surface; and some of the lower joints nearest the roots are found in the subjacent bed of shale.”

Interpretation of elastic – strain – recovery measurements near Elliot Lake, Ontario

1970 ◽  
Vol 7 (2) ◽  
pp. 576-578
Author(s):  
G. H. Elsbacher ◽  
H. U. Bielenstein
Keyword(s):  
Stress Field ◽  
Elastic Strain ◽  
Sedimentary Rocks ◽  
Lake Ontario ◽  
Strain Recovery ◽  
Tectonic Deformation ◽  
In Situ Stresses ◽  
Stress Environments ◽  
Mine Openings

In situ stresses obtained by measurements of elastic – strain – recovery in quartzose sedimentary rocks near Elliot Lake are interpreted in terms of two stress environments: one stress field induced by mining close to the mine openings and a remanent stress field preserved in the rocks from a time of tectonic deformation in the area.

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