scholarly journals Refining the interpretation of oxygen isotope variability in free-swimming organisms

2018 ◽  
Author(s):  
Benjamin Linzmeier
Keyword(s):  
Water Column ◽  
Null Model ◽  
Swimming Velocity ◽  
Time Averaging ◽  
Similar Data ◽  
Free Swimming ◽  
Column Temperature ◽  
Swimming Depth ◽  
And Behavior ◽  
The Tropics

Serially sampled δ18O from fossil and modern cephalopods may provide new insight into the behavior and longevity of individuals. Interpretation of these data is generally more difficult than similar data from bivalves or brachiopods because the measured δ18O from shell combines both seasonal change and depth change over the life of an individual. In this paper, a simple null model is presented combining the three fundamental controls on a measured δ18O profile in a free-swimming organism: swimming behavior, seasonal water column temperature change, and time averaging in sampling. Model results indicate that seasonal variability in δ18O in a free-swimming organism can be interpreted in locations with strong seasonality through most of the swimming range but is complicated by swimming velocity and is sometimes best expressed by changes in δ18O variance rather than simple sinusoidal patterns. In other locations with a stable thermocline or seasonal ranges in only a small portion of the water column, no variability caused by seasonality would be expected. Furthermore, large ranges of δ18O (~4‰) are possible within and between individuals in settings with persistent thermoclines like the tropics, depending on the swimming depth limits and behavior of individuals. These results suggest that future interpretation of serially sampled δ18O should consider seasonal water column variation from either modern or modeling sources in addition to comparison to co-occurring benthic and planktic organisms. Additionally, this modeling casts doubt on the promise of isotope sclerochronology alone as a growth chronometer in ammonites and other free-swimming fossil organisms and highlights the need for other methods of quantitatively determining age.

Paddlefish Management, Propagation, and Conservation in the 21st Century

2009 ◽  
Keyword(s):  
Flow Field ◽  
Water Column ◽  
21St Century ◽  
Small Diameter ◽  
Fork Length ◽  
Water Velocity ◽  
Ichthyophthirius Multifiliis ◽  
Free Swimming ◽  
Burst Swimming ◽  
And Behavior

<em>Abstract</em>.—Rheotaxis, endurance, and behavior of juvenile paddlefish <em>Polyodon spathula </em>(<115 mm eye-to-fork length) were measured in a laboratory swim tunnel. Paddlefish were positively rheotactic (>80% of individuals tested). They exhibited sustained swimming ($200 min) at water velocities up to 40 cm/s, prolonged swimming (0.5–52 min) at 30–50 cm/s, and burst swimming (<0.5 min) at water velocities 60–75 cm/s. Behavior consisted exclusively of free swimming in the water column. Fish recovered from white spot <em>Ichthyophthirius multifiliis </em>disease appeared healthy but had reduced endurance at low to moderate water velocities. Data were used to quantify risk of entrainment by dredges at a given water velocity as an index, values of which ranged from 0.00 (unlikely) to 1.00 (inevitable). Entrainment risk was evaluated for escape speeds considered environmentally conservative (based on prolonged swim speed) and operationally conservative (based on burst swim speed), using flow field models of three cutterhead dredges having pipe diameters of 71, 51, and 30 cm. Entrainment was likely within a radius of 1.25 m of the cutterhead, but degree of risk and distance of entraining flow varied substantially with pipe size. Entrainment risk of paddlefish can be reduced by (1) temporal restrictions on dredging, (2) stocking juveniles that have not been treated for disease, and (3) use of small diameter pipes (ideally < 30 cm).

Phytoplankton Biomass and Water Column Temperature Dynamics of Lake James, NC USA

2004 ◽  
Vol 1 (1) ◽  
pp. 23-26
Author(s):  
Kemal Celik ◽  
James Schindler . ◽  
William Foris . ◽  
Jonathan Knight .
Keyword(s):  
Water Column ◽  
Phytoplankton Biomass ◽  
Column Temperature ◽  
Temperature Dynamics ◽  
Lake James

Suprabenthic crustacean fauna of a denseAmpeliscacommunity from the English Channel

1996 ◽  
Vol 76 (4) ◽  
pp. 909-929 ◽  
Author(s):  
Jean-Claude Dauvin ◽  
Souaad Zouhiri
Keyword(s):  
Atlantic Ocean ◽  
Water Column ◽  
Vertical Migration ◽  
Fine Sand ◽  
Abundant Species ◽  
Sexually Dimorphic ◽  
English Channel ◽  
Free Swimming ◽  
Sea Bottom ◽  
Sea Bed

Ninety-six species (97, 677individuals) were collected over the course of 6 h in five suprabenthic sledge hauls from a very denseAmpeliscafine sand community from the Bay of Morlaix (western English Channel). All the species migrated into the water column at night (98% of the specimens collected in the suprabenthos were found in the night hauls). The 23 most abundant species collected were classified into five groups based on their height within the water column, but two groups predominated: the upper suprabenthic species, abundant at 0–80–145 m above the sea-bed; and the lower suprabenthic species which were abundant only near the sea bottom (-0–1–0–75 m high). Three different patterns of nocturnal vertical migration were distinguished based on the timing of maximum swimming activity: at dusk; at the beginning of the night; or later in the night. Sexually dimorphic patterns of free-swimming behaviour was observed inAmpeliscaand some other species of Amphipoda (Bathyporeia teniupes, Metaphoxusfultoni), and Cumacea (Bodotria pulchella, Pseudocuma longicornis), with many more males than females migrating into the water column at night. Finally, the density of suprabenthic crustaceans in nocturnal hauls was amongst the highest reported from infralittoral or circalittoral suprabenthic studies on other parts of the Atlantic Ocean sampled during spring.

A model for the light-limited growth of buoyant phytoplankton in a shallow, turbid waterbody

1994 ◽  
Vol 45 (5) ◽  
pp. 847 ◽  
Author(s):  
BE Sherman ◽  
IT Webster
Keyword(s):  
Wind Speed ◽  
Water Column ◽  
Chlorophyll Concentration ◽  
Light Attenuation ◽  
Euphotic Zone ◽  
Limited Growth ◽  
Potential Growth ◽  
Column Temperature ◽  
Turbid Waters ◽  
Neutrally Buoyant

A computer model was used to explore the relationship between buoyancy and the light-limited growth of phytoplankton in very turbid waters. The model simulates the potential growth of phytoplankton as a function of flotation speed, using field observations of photosynthetically active radiation, wind speed, surface-layer thickness (from water-column temperature data), and light attenuation made at Rushy Billabong on the River Murray from 28 November 1991 to 26 March 1992. A unique feature of the model is the simulation of the development and dispersal of surface scums as a function of wind speed. Under nutrient-replete conditions, the model predicted that phytoplankton with a flotation speed of 1-10 m day-1 (typical of Anabaena flos-aquae and Microcystis aeruginosa) would grow up to four times faster than would neutrally buoyant phytoplankton with the same maximum specific growth rate. In the shallow system modelled, high flotation speeds allowed a large proportion of the total population to rise into the euphotic zone shortly after the onset of stratification each day. Surface scums played an important role in maintaining the more buoyant phytoplankton populations close to the water surface. Under the very turbid conditions in the billabong (100 nephelometric turbidity units), self-shading became significant only when the mean chlorophyll concentration in the water column approached 100 mg chla m-3.

scholarly journals Swimming mediated by ciliary beating: comparison with a squirmer model

2019 ◽  
Vol 874 ◽  
pp. 774-796 ◽  
Author(s):  
Hiroaki Ito ◽  
Toshihiro Omori ◽  
Takuji Ishikawa
Keyword(s):  
Cell Body ◽  
Hydrodynamic Interactions ◽  
Swimming Velocity ◽  
Energy Costs ◽  
Theoretical Studies ◽  
Free Swimming ◽  
Ciliary Beating ◽  
Aspect Ratios ◽  
Swimming Efficiency ◽  
Micro Organisms

The squirmer model of Lighthill and Blake has been widely used to analyse swimming ciliates. However, real ciliates are covered by hair-like organelles, called cilia; the differences between the squirmer model and real ciliates remain unclear. Here, we developed a ciliate model incorporating the distinct ciliary apparatus, and analysed motion using a boundary element–slender-body coupling method. This methodology allows us to accurately calculate hydrodynamic interactions between cilia and the cell body under free-swimming conditions. Results showed that an antiplectic metachronal wave was optimal in the swimming speed with various cell-body aspect ratios, which is consistent with former theoretical studies. Exploiting oblique wave propagation, we reproduced a helical trajectory, like Paramecium, although the cell body was spherical. We confirmed that the swimming velocity of model ciliates was well represented by the squirmer model. However, squirmer modelling outside the envelope failed to estimate the energy costs of swimming; over 90 % of energy was dissipated inside the ciliary envelope. The optimal swimming efficiency was given by the antiplectic wave; the value was 6.7 times larger than in-phase beating. Our findings provide a fundamental basis for modelling swimming micro-organisms.

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