Short-Term Effects of Zooplankton Manipulations on Phosphate Uptake

1987 ◽  
Vol 44 (5) ◽  
pp. 1038-1044 ◽  
Author(s):  
Daniel T. Hamilton ◽  
William D. Taylor
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Phosphate Uptake ◽  
Phosphorus Uptake ◽  
Turnover Time ◽  
Relative Increase ◽  
Short Term ◽  
Nutrient Environment ◽  
Resource Levels

Samples of epilimnetic water were collected, manipulated to alter their zooplankton fauna, and incubated in situ for 24 h. We hypothesized that removal and concentration of zooplankton would decrease and increase phosphate turnover time, respectively, and that the presence of zooplankton would increase the accumulation of added 32PO4 by algae (particles greater than 1.0 μm) relative to bacteria (particles 0.2–1.0 μm). Although the treatments produced significant changes in turnover time and size distribution, neither hypothesis was supported; removal of zooplankton did not decrease turnover time, and it reduced the dominance of 0.2- to 1.0-μm particles in phosphorus uptake. However, concentrating microzooplankton frequently increased turnover time. Zooplankton removal caused a relative increase in ciliates, suggesting that these protozoa may be limited by their predators rather than by resource levels. Our results suggest that microzooplankton were the most important grazers and that the nutrient environment of phytoplankton was not directly affected by mesozooplankton. Phosphate dynamics were probably determined by bacteria, the protozoan predators of bacteria, and the supply of dissolved organic carbon.

scholarly journals Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors: Natural Fluctuations or Artefacts?

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 859
Author(s):  
Suzanne R. Jacobs ◽  
Björn Weeser ◽  
Mariana C. Rufino ◽  
Lutz Breuer
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Stream Water ◽  
Visible Spectrum ◽  
Mobile Sensor ◽  
Stream Water Quality ◽  
High Resolution Data ◽  
Diurnal Patterns ◽  
Solute Dynamics

In situ spectrophotometers measuring in the UV-visible spectrum are increasingly used to collect high-resolution data on stream water quality. This provides the opportunity to investigate short-term solute dynamics, including diurnal cycling. This study reports unusual changes in diurnal patterns observed when such sensors were deployed in four tropical headwater streams in Kenya. The analysis of a 5-year dataset revealed sensor-specific diurnal patterns in nitrate and dissolved organic carbon concentrations and different patterns measured by different sensors when installed at the same site. To verify these patterns, a second mobile sensor was installed at three sites for more than 3 weeks. Agreement between the measurements performed by these sensors was higher for dissolved organic carbon (r > 0.98) than for nitrate (r = 0.43–0.81) at all sites. Higher concentrations and larger amplitudes generally led to higher agreement between patterns measured by the two sensors. However, changing the position or level of shading of the mobile sensor resulted in inconsistent changes in the patterns. The results of this study show that diurnal patterns measured with UV-Vis spectrophotometers should be interpreted with caution. Further work is required to understand how these measurements are influenced by environmental conditions and sensor-specific properties.

In situ dissolved organic carbon (DOC) release by submerged macrophyte–epiphyte communities in southern Quebec lakes

2009 ◽  
Vol 66 (9) ◽  
pp. 1522-1531 ◽  
Author(s):  
M. Demarty ◽  
Y. T. Prairie
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Myriophyllum Spicatum ◽  
Dry Weight ◽  
Release Rates ◽  
Doc Production ◽  
Epiphyte Communities ◽  
Benthic Chambers ◽  
Freshwater Macrophyte

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte–epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C·m–2·h–1. Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C·m–2·h–1 (standard deviation (SD), ±0.65) or 56 µg C·g dry weight–1·h–1 (SD, ±8), which we suggest can be used for extrapolations at the lake scale.

scholarly journals In-situ fluorescence spectroscopy indicates total bacterial abundance and dissolved organic carbon

2020 ◽  
Vol 738 ◽  
pp. 139419 ◽  
Author(s):  
James P.R. Sorensen ◽  
Mor Talla Diaw ◽  
Abdoulaye Pouye ◽  
Raphaëlle Roffo ◽  
Djim M.L. Diongue ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Carbon ◽  
Bacterial Abundance ◽  
Total Bacterial Abundance

Rates of carbon fixation, organic carbon release and translocation in a reef-building foraminifer, Marginopora vertebralis

1977 ◽  
Vol 28 (3) ◽  
pp. 311 ◽  
Author(s):  
DF Smith ◽  
WJ Wiebe
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Particulate Organic Carbon ◽  
Carbon Fixation ◽  
Turnover Time ◽  
In Situ Incubation ◽  
Carbon Release ◽  
Hermatypic Corals ◽  
Shell Carbonate

Rate measurements obtained in this study and the population densities of foraminifera reported elsewhere suggest that such organisms may well exceed the hermatypic corals in their contribution to reef biogensis and energy fluxes. The average rates at which M. vertebralis photosynthetically fixes carbon into particulate organic carbon, dissolved organic carbon, and shell carbonate, per square centimetre of organism, were estimated to be 50, 1 .5, and 26 ng C min-1 respectively. Exogenously supplied dissolved organic carbon was taken up by M. vertebralis at a rate of 0.05 ng C min-1 in the light, and 0.09 ng C min-1 in the dark per square centimetre of organism. The turnover time of particulate organic carbon (91 h) was measured in a long-term in situ incubation during which 19% of the radioactivity lost from the particulate organic carbon entered the calcareous foraminiferal shell.

Optical in-situ sensors capture dissolved organic carbon (DOC) dynamics after prescribed fire in high-DOC forest watersheds

2019 ◽  
Vol 28 (10) ◽  
pp. 761 ◽  
Author(s):  
Christopher I. Olivares ◽  
Wenbo Zhang ◽  
Habibullah Uzun ◽  
Cagri Utku Erdem ◽  
Hamed Majidzadeh ◽  
...  
Keyword(s):  
South Carolina ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Optical Sensors ◽  
Prescribed Fire ◽  
Second Order ◽  
In Situ Sensors ◽  
Forest Watersheds ◽  
Doc Load

Fires alter terrestrial dissolved organic carbon (DOC) exports into water, making reliable post-fire DOC monitoring a crucial aspect of safeguarding drinking water supply. We evaluated DOC optical sensors in a pair of prescribed burned and unburned first-order watersheds at the Santee Experimental Forest, in the coastal plain forests of South Carolina, and the receiving second-order watershed during four post-fire storm DOC pulses. Median DOC concentrations were 30 and 23mgL−1 in the burned and unburned watersheds following the first post-fire storm. Median DOC remained high during the second and third storms, but returned to pre-fire concentrations in the fourth storm. During the first three post-fire storms, sensor DOC load in the burned watershed was 1.22-fold higher than in the unburned watershed. Grab samples underestimated DOC loads compared with those calculated using the in-situ sensors, especially for the second-order watershed. After fitting sensor values with a locally weighted smoothing model, the adjusted sensor values were within 2mgL−1 of the grab samples over the course of the study. Overall, we showed that prescribed fire can release DOC during the first few post-fire storms and that in-situ sensors have adequate sensitivity to capture storm-related DOC pulses in high-DOC forest watersheds.

Hurricanes accelerate dissolved organic carbon cycling in coastal ecosystems

2020 ◽  
Author(s):  
Ge Yan ◽  
Jessica Labonté ◽  
Antonietta Quigg ◽  
Karl Kaiser
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Flood Plain ◽  
Extreme Weather Events ◽  
Flood Events ◽  
Decay Constants ◽  
Continental Shelves ◽  
Weather Events ◽  
Organic Carbon Cycling

<p>Extreme weather events such as tropical storms and hurricanes deliver large amounts of<br>freshwater (stormwater and river discharge) and associated dissolved organic carbon (DOC)<br>to estuaries and the coastal ocean, affecting water quality and carbon budgets. Hurricane<br>Harvey produced an unprecedented 1000-year flood event in 2017 that inundated the heavily<br>urbanized and industrialized Houston/Galveston region (Texas, USA). Within a week, storm-<br>associated floodwater delivered 105±10 Gg of terrigenous dissolved organic carbon (tDOC)<br>to Galveston Bay and the Gulf of Mexico continental shelves. In-situ decay constants of<br>8.75-28.33 yr<sup> -1</sup> resulted in the biomineralization of ~70% of tDOC within one month of<br>discharge from the flood plain. The high removal efficiency of tDOC was linked to a diverse<br>microbial community capable of degrading a wide repertoire of dissolved organic matter<br>(DOM), and suggested hurricane-induced flood events affect net CO<sub>2</sub> exchange and nutrient<br>budgets in estuarine watersheds and coastal seas.<br><br></p>

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