Photoinhibition of Respiration in Epilithic Periphyton

To determine whether respiration in the light was equal to respiration in the dark we examined epilithic periphyton from a lake acidified experimentally with sulfuric acid. Because of the low concentrations of dissolved inorganic carbon, we could use both 12C and 14C uptake techniques. Using the 14C technique we could correct for residual photosynthesis in samples treated with the photosynthetic inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dsmethyiurea). DCMU did not alter rates of dark respiration. However, respiration of DCMU-treated samples in the light was less than in the dark (P < 0.01). This photoinhibition of respiration was about 40% of dark control values. If we had calculated gross photosynthesis for the specific conditions of this experiment, but assumed incorrectly that light and dark respiration were equal, we would have overestimated gross photosynthesis by about 30%. Thus, if the ratio of respiration to photosynthesis is high, researchers will have to evaluate the effect of light on respiration to better estimate gross photosynthesis. The technique we describe, of monitoring both 12C and 14C flux in DCMU-treated samples in the light, will provide an underestimate of respiration in the light.

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Early Responses of Periphyton to Experimental Lake Acidification

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f87-289 ◽

1987 ◽

Vol 44 (S1) ◽

pp. s135-s149 ◽

Cited By ~ 63

Author(s):

Michael A. Turner ◽

Michael B. Jackson ◽

David L. Findlay ◽

Roger W. Graham ◽

Edwin R. DeBruyn ◽

...

Keyword(s):

Nitric Acid ◽

Littoral Zone ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Dark Respiration ◽

Net Photosynthesis ◽

Taxonomic Composition ◽

Filamentous Algae ◽

Low Concentrations ◽

Selection Of

We studied the periphyton in two small lakes acidified experimentally with either sulfuric or nitric acid. For comparison, we monitored periphyton in one previously acidified (sulfuric) lake and in two neutral lakes. Net photosynthesis declined in epilithic periphyton in the middle littoral zone (1–2 m) of both recently acidified basins in response to reduced concentrations of dissolved inorganic carbon. Dark respiration and taxonomic composition remained largely unchanged in this zone. Attached filamentous algae proliferated early [Formula: see text] in the upper littoral zone (< 1 m) of the sulfuric acid basin confirming earlier observations made in the previously acidified lake. These Zygnematales-dominated filamentous algae (largely Mougeotia sp.) developed conspicuously on submerged rock and log surfaces. In contrast, growth on macrophytes was variable in both the neutral and nitric acid systems. We hypothesize that during the early stages of acidification proliferation of filamentous Chlorophyceae is due to selection of algae tolerant of increased H+and better adapted to obtain inorganic carbon at low concentrations, in combination with reduced grazing.

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Effect of light and CO2 on inorganic carbon uptake in the invasive aquatic CAM-plant Crassula helmsii

Functional Plant Biology ◽

10.1071/fp09281 ◽

2010 ◽

Vol 37 (8) ◽

pp. 737 ◽

Cited By ~ 13

Author(s):

Signe Koch Klavsen ◽

Stephen C. Maberly

Keyword(s):

Native Species ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

High Light ◽

Photosynthetic Rates ◽

Co2 Compensation Point ◽

Low Co2 ◽

Co2 Concentrations ◽

Invasive Aquatic Plant ◽

Effect Of Light

Crassula helmsii (T. Kirk) Cockayne is an invasive aquatic plant in Europe that can suppress many native species because it can grow at a large range of dissolved inorganic carbon concentrations and light levels. One reason for its ecological success may be the possession of a regulated Crassulacean Acid Metabolism (CAM), which allows aquatic macrophytes to take up CO2 in the night in addition to the daytime. The effect of light and CO2 on the regulation of CAM and photosynthesis in C. helmsii was investigated to characterise how physiological acclimation may confer this ecological flexibility. After 3 weeks of growth at high light (230 µmol photon m–2 s–1), C. helmsii displayed 2.8 times higher CAM at low compared with high CO2 (22 v. 230 mmol m–3). CAM was absent in plants grown at low light (23 µmol photon m–2 s–1) at both CO2 concentrations. The observed regulation patterns are consistent with CAM acting as a carbon conserving mechanism. For C. helmsii grown at high light and low CO2, mean photosynthetic rates were relatively high at low concentrations of CO2 and were on average 80 and 102 µmol O2 g–1 DW h–1 at CO2 concentrations of 3 and 22 mmol m–3 CO2, which, together with mean final pH values of 9.01 in the pH drift, indicate a low CO2 compensation point (<3 mmol m–3) but do not indicate use of bicarbonate as an additional source of exogenous inorganic carbon. The relatively high photosynthetic rates during the entire daytime were caused by internally derived CAM-CO2 and uptake from the external medium. During decarboxylation, CO2 generated from CAM contributed up to 29% to photosynthesis, whereas over a day the contribution to the carbon balance was ≤13%. The flexible adjustment of CAM and the ability to maintain photosynthesis at very low external CO2 concentrations, partly by making use of internally generated CO2 via CAM, may contribute to the broad ecological niche of C. helmsii.

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Gas Exchange, Photosynthetic Uptake, and Carbon Budget for a Radiocarbon Addition to a Small Enclosure in a Stratified Lake

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f80-060 ◽

1980 ◽

Vol 37 (3) ◽

pp. 464-471 ◽

Cited By ~ 16

Author(s):

Peter Bower ◽

Daniel McCorkle

Keyword(s):

Mass Transfer ◽

Gas Exchange ◽

Primary Productivity ◽

Carbon Budget ◽

Inorganic Carbon ◽

Net Primary Productivity ◽

Dissolved Inorganic Carbon ◽

Dark Respiration ◽

Late Summer ◽

Transfer Coefficients

9250 kBq (250 μCi) of 14C as NaHCO3 were added to the mixed-layer waters inside a long, cylindrical plastic enclosure anchored in an oligotrophic lake of the Canadian Shield. Loss of 14C from the epilimnion was predominantly in the form of irreversible gas-exchange across the liquid–air interface. This loss was measured by 14C inventory of the epilimnion and thermocline waters. Using the Lewis and Whitman boundary layer model, values for the mass transfer coefficient of 126, 58, and 100 cm/d were determined for three distinct phases in the deepening of the epilimnion during autumn cooling. The relationship between these mass transfer coefficients and the average wind speeds over the same three time periods were consistent with the results of previous wind-tunnel, gas-exchange experiments.Two significant features of the carbon budget during the course of the experiment were the large net outflux of CO2 from the corral (with [Formula: see text] in the epilimnion 3–7 times atmospheric levels) and the doubling of the total dissolved inorganic carbon (DIC) content of the epilimnion. The major source of carbon for these two processes was the entrainment of dissolved inorganic carbon as the epilimnion deepened during the cool days of late summer. Particulate organic carbon was also entrained and its oxidation contributed to the net DIC increase and CO2 loss. Simultaneous determinations of daily integral primary productivity by an incubator technique and by direct measurement of 14C uptake inside the enclosure were consistent. Dark respiration was 45–53% of daily integral primary productivity, but total respiration was nearly two times that for dark plus light respiration. Net primary productivity was thus substantially negative.Key words: Gas exchange, photosynthetic uptake, carbon budget

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Eutrophication of Lake 227 by Addition of Phosphate and Nitrate: the Second, Third, and Fourth Years of Enrichment, 1970, 1971, and 1972

Journal of the Fisheries Research Board of Canada ◽

10.1139/f73-233 ◽

1973 ◽

Vol 30 (10) ◽

pp. 1415-1440 ◽

Cited By ~ 107

Author(s):

D. W. Schindler ◽

H. Kling ◽

R. V. Schmidt ◽

J. Prokopowich ◽

V. E. Frost ◽

...

Keyword(s):

Standing Crop ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Low Carbon ◽

Particulate Carbon ◽

Water Renewal ◽

Anoxic Conditions ◽

Natural Lakes ◽

Low Concentrations ◽

Carbon Concentrations

Lake 227, a small lake with extremely low concentrations of dissolved inorganic carbon, was fertilized with PO4 and NO3 for 4 years, beginning in 1969. The additions increased natural inputs of phosphorus and nitrogen about five times.Phytoplankton standing crop increased nearly two orders of magnitude, and the Cryptophyceae and Chrysophyceae present in natural lakes of the area were replaced by Chlorophyta and Cyanophyta. The standing crop of phytoplankton per square meter was near the maximum which could theoretically be maintained by surface light, in spite of the low carbon concentrations. Added phosphate and nitrate were rapidly removed by phytoplankton, so that concentrations in the lake remained low.Almost all of the added nutrient was retained by the lake, in spite of relatively fast water renewal times. An average of 80% of the phosphorus income of the lake was sedimented. There was no return of phosphorus from sediments in spite of anoxic conditions in the hypolimnion.Photosynthesizing plankton reduced dissolved inorganic carbon concentrations severely, causing a flux of atmospheric CO2 into the lake. From 69 to 95% of the inorganic + particulate carbon supplied to the lake was from the atmosphere. Results demonstrate that low carbon concentrations do not hinder eutrophication if phosphorus and nitrogen supplies are adequate.

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