Use of a whirling cup rotor to stir benthic chambers

Cahoon, Lawrence B.

doi:10.1007/bf00007134

Cited by 9 publications

(21 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In practice only 2 incubations exceeded 8 h duration. The benthic chambers used in microalgal production determinations were made of clear plastic domes of 30 cm diameter (Cahoon 1988). These domes transmitted ca 85 % of photosynthetically active radiation (PAR).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Benthic microalgal production in Onslow Bay, North Carolina, USA

Cahoon¹,

Cooke²

1992

Mar. Ecol. Prog. Ser.

123

View full text Add to dashboard Cite

Benthic microalgal production and sediment respiration were measured in situ at 8 locations in Onslow Bay, a portion of the North Carolina continental shelf, between 1984 and 1989, by measuring changes in dissolved oxygen concentrations inside clear and opaque benthic chambers placed by divers. Measurements were also made of water column productivity, phytoplankton biomass, benthic microalgal biomass, light flux, and temperature. Benthic production and respiration were measured from March through October at locations ranging from 14.6 to 41 m deep. Gross benthic microalgal production averaged 24.9 mg C m-'h-', compared to average integrated water column production of 27.4 mg C m-' h-' Sediment respiration rates averaged 18.1 mg C m-' h-'. Benthic microalgal biomass averaged 36.4 mg chl a m-2, and always exceeded integrated phytoplankton biomass, which averaged 8.2 mg chl a m-'. Benthic mlcroalgae had much lower average assimilation numbers than phytoplankton (0.8 vs 5.2 mg C (mg chl a ) -' h -' ) . Benthic microalgae make a significant contribution to total shelf production in Onslow Bay Open sand bottom habitats in this ecosystem must now be viewed as productive, rather than relatively barren.

show abstract

Section: Methodsmentioning

confidence: 99%

“…Dark chambers were constructed of the same domes by painting the outside with > 4 coats of flat black latex paint. Stirring of the contents of the domes was provided by a whirling cup rotor device (Cahoon 1988).…”

Section: Methodsmentioning

confidence: 99%

Benthic microalgal production in Onslow Bay, North Carolina, USA

Cahoon¹,

Cooke²

1992

Mar. Ecol. Prog. Ser.

123

View full text Add to dashboard Cite

show abstract

“…Attempts to match in situ boundary layer flow by the use of open channels aligned into the flow (Asmus et al 1992) can be successful with careful design, but flow disturbance by the physical structure may result in entrance condition and container artifacts (Snelgrove et al 1995). Stirring away from the boundary can produce realistic sediment-water fluxes (Cahoon 1988, Buchholtz-ten Brink et al 1989, but at a cost of too much internal energy. Small scale pressure gradients induced by stirring a n enclosure also may result in advective flushing of pore waters in sandy sediments (Huettel & Gust 1992).…”

Section: W E L L -M I X E D M E S O C O S M S T R a T I F I E D M E Smentioning

confidence: 99%

Turbulent mixing in experimental ecosystem studies

Sanford¹

1997

Mar. Ecol. Prog. Ser.

122

View full text Add to dashboard Cite

ABSTRACT. Turbulent mixing is an integral aspect of aquatic ecosystems Turbulence affects ecosystem features ranglng from phytoplankton blooms at large scales through microscale interactions in the plankton. Enclosed experimental ecosystems, if they are to mimic the function of natural ecosystems, also must mimic natural turbulence and its effects. Large-scale velocity gradients and unstable buoyancy fluxes generate turbulent mixing in nature, most often at the surface and bottom boundaries and in the pycnocline. Large eddy sizes are controlled by the mixed layer depth, boundary layer thickness, or overturning length in the pycnocl~ne. Turbulent energy cascades through smaller and smaller eddy scales until it can be dissipated by molecular viscosity at the smallest scales. In contrast, artificial apparatuses frequently are used to generate turbulent m~x i n g in the interior of experimental ecosystem enclosures Large eddy sizes are controlled by the size of the generation apparatus, and they usually are much smaller than in nature Mismatched large eddy length scales and differences in turbulence generation mechanisms are responsible for the difficulties in mimicking natural turbulent mixing in experimental enclosures. The 2 most important turbulence parameters to consider in experimental ecosystem research are overall mixing time, T,,,, and turbulence dissipation rate, E. If the levels, spatial dlstribut~ons, and temporal variability of T,,, and E can be matched between an enclosure and the natural system it IS to model, then potential mixing artifacts can be minimized. An important additional consideration is that benthic ecosystems depend on the time-averaged boundary layer flow a s much as the turbulence. Existing designs for m i x~n g experimental ecosystems are capable of reasonably representing some aspects of natural turbulent mixing Paddle and grid stirring are the best available techniques for water column mixing, and flumes are best for benthic turbulence. There is no design at present that represents both environments adequately. More work also is needed on mixing of flexiblewall in situ enclosures. A more serious problem, however, is that turbulent mixing in experimental ecos)~stem studies too often is ignored, inadequately characterized, or unreported. Several methods are available for reasonable characterlzation of mixing in enclosures without sophisticated technology, and the technology for direct velocity measurements is becoming more accessible. Experimental ecosystem researchers should make a concerted effort to implement, characterize, and report on turbulent mixing In t h e~r enclosures.

show abstract

“…The opening was stoppered after insertion into the sediment to a depth of 5 cm and withdrawal of initial samples. Whirling cup rotors used the natural flow of the creek to drive slow stirring (<15 rpm) in the chamber in proportion to external flows as slow as 0.02 m s -1 (Cahoon, 1988), allowing for continual mixing and thus uniform DO concentration within the chambers. Clear 0.3 cm diam PVC tubing inserted into the side of the chamber allowed for extraction of water samples.…”

Section: Dissolved Oxygen Fluxesmentioning

confidence: 99%

Water column oxygen demand and sediment oxygen flux: patterns of oxygen depletion in tidal creeks

2007

Self Cite

View full text Add to dashboard Cite

Low dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD 5 ) and sediment oxygen flux (SOF) at selected tidal creek sites monthly over a 1-year period. Ancillary physical, chemical and biological data were collected to identify factors related to oxygen loss. BOD 5 rates ranged from 0.0 mg l -1 to 7.6 mg l -1 and were correlated positively with organic suspended solids, total suspended solids, chlorophyll a concentrations, temperature, and dissolved oxygen, and negatively with pH and nitrate + nitrite. SOF rates ranged from 0.0 to 9.3 g O 2 m -2 d -1 , and were positively correlated with temperature, chlorophyll a, and total suspended solids, but negatively with dissolved oxygen. Both forms of oxygen uptake were seasonally dependent, with BOD 5 elevated in spring and summer and SOF elevated in summer and fall. Average oxygen loss to sediments was greater and more variable than oxygen loss in the water column. Oxygen deficits at three of five locations were significantly related to BOD 5 and SOF, but not at two sites where ground water discharges were observed. Correlation and principal component analyses suggested that BOD 5 and SOF responded to somewhat different suites of environmental variables. BOD 5 was driven by a set of parameters linked to warm season storm water inputs that stimulated organic seston loads, especially chlorophyll a, while SOF behaved less strongly so. Runoff processes that increase loads of organic material and nutrients and ground water discharges low in dissolved oxygen contribute to occurrences of low dissolved oxygen in tidal creeks.

show abstract

Use of a whirling cup rotor to stir benthic chambers

Cited by 9 publications

References 25 publications

Benthic microalgal production in Onslow Bay, North Carolina, USA

Benthic microalgal production in Onslow Bay, North Carolina, USA

Turbulent mixing in experimental ecosystem studies

Water column oxygen demand and sediment oxygen flux: patterns of oxygen depletion in tidal creeks

Contact Info

Product

Resources

About