Limnology and Oceanography: Fluids and Environments最新文献

{"title":"Hydrodynamic effects of spines: A different spin","authors":"Hoa Nguyen,&nbsp;Lee Karp-Boss,&nbsp;Peter A. Jumars,&nbsp;Lisa Fauci","doi":"10.1215/21573698-1303444","DOIUrl":"10.1215/21573698-1303444","url":null,"abstract":"<div>\u0000 <p>Many small planktonic organisms bear spines, some of whose potential functions have been explored, for example, in increasing drag during gravitational settling or in defense against predators. Using an immersed boundary framework, we performed computational fluid dynamic simulations that examine the rotational dynamics of model diatoms in shear flows with varying spine number, length, and angle. We found that the motion of spined cells could be accurately predicted from simple theory for motion of spheroids by applying that theory to the smallest spheroid that could inscribe the cell inclusive of its spines. The poorest fits were for small numbers or extreme angles of spines that left large volumes of the inscribing spheroid unoccupied by any spines. Although the present work provides a simple means of predicting motions of rigid, spined cells in shear flows, the effects of spines on nutrient exchange remain to be explored.</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"110-119"},"PeriodicalIF":0.0,"publicationDate":"2011-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1303444","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physical and biological controls of vertical gradients in phytoplankton","authors":"Jennifer C. Prairie,&nbsp;Peter J. S. Franks,&nbsp;Jules S. Jaffe,&nbsp;Mark J. Doubell,&nbsp;Hidekatsu Yamazaki","doi":"10.1215/21573698-1267403","DOIUrl":"10.1215/21573698-1267403","url":null,"abstract":"<div>\u0000 <p>Small-scale vertical heterogeneity in phytoplankton distributions is common in coastal waters and may be a critical feature influencing trophic coupling in planktonic systems. Here we develop a model to investigate the biological and physical dynamics that control vertical gradients in phytoplankton abundance. The model includes phytoplankton layer formation and layer destruction through mixing and predicts that the local maximum scaled phytoplankton gradient is controlled by the relative strengths of these dynamics. We compare the predictions of this model to highly resolved profiles of phytoplankton concentration and fluorescence collected using a free-falling planar laser imaging fluorometer (FIDO-Φ) and turbulence microstructure profiler data (TurboMAP-L). From these profiles, we estimate the model parameters: the maximum rate of layer formation and minimum possible layer thickness. The maximum rate of layer formation ranged from 0.46 to 0.94 d^− 1, which is comparable to maximum reported growth rates of the most common phytoplankton taxa found in our samples. The minimum layer thickness estimated from our data suggests that persistent phytoplankton layers thinner than approximately 0.5 m may be rare in coastal waters. This study provides a mechanistic explanation for some of the underlying dynamics governing phytoplankton layer formation, maintenance, and destruction and will allow us to better predict the magnitude and occurrence of these ecologically important structures in the field.</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"75-90"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1267403","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Horizontal internal-tide fluxes support elevated phytoplankton productivity over the inner continental shelf","authors":"Andrew J. Lucas,&nbsp;Peter J. S. Franks,&nbsp;Christopher L. Dupont","doi":"10.1215/21573698-1258185","DOIUrl":"10.1215/21573698-1258185","url":null,"abstract":"<div>\u0000 <p>The narrow continental shelf of the Southern California Bight (SCB) is characterized by elevated primary productivity relative to the adjacent open ocean. This persistent gradient is maintained by the nitrate fluxes associated with internal waves of tidal frequency (the internal tide). Here we provide the first estimates of the internal-tide–driven horizontal fluxes of nitrate, heat, energy, and salinity, calculated from high-resolution, full water-column data gathered by an autonomous wave-powered profiler and a bottom-mounted current meter. The vertically integrated nitrate, heat, and energy fluxes were onshore over the 3-week period of the field experiment. The inner-shelf area- and time-averaged dissipation rate due to the onshore horizontal energy flux, 2.25 × 10^− 7 W kg^− 1, was elevated relative to open ocean values. The magnitude of the vertically integrated horizontal nitrate flux (136.4 g N m^− 1 d¹) was similar to phytoplanktonic nitrate uptake rates over the inner-shelf. This nitrate flux was variable in time, capable of supporting 0–2800 mg C m^− 2 d^− 1 (mean approx. 774 mg C m^− 2 d^− 1) of “new” primary productivity, depending on the energetics of the internal tide and the cross-shore distribution of nitrate. We postulate that the horizontal, internal-tide–driven nitrate flux is the primary cause of the persistently elevated phytoplankton biomass and productivity over the narrow SCB inner shelf. Furthermore, these results suggest that horizontal fluxes of nutrients driven by internal waves may contribute significantly to primary productivity along the boundaries of aquatic environments.</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"56-74"},"PeriodicalIF":0.0,"publicationDate":"2011-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1258185","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wave-driven porewater and solute circulation through rippled elastic sediment under highly transient forcing","authors":"M. Bayani Cardenas,&nbsp;Houshuo Jiang","doi":"10.1215/21573698-1151658","DOIUrl":"10.1215/21573698-1151658","url":null,"abstract":"<div>\u0000 <p>Waves induce porewater flow and solute transport through permeable marine sediment. However, past studies have ignored high-frequency pressure pulses, under the assumption that the porewater flow field is adequately represented by a time-averaged one or that the saturated sediment is incompressible. We modeled porewater flow and solute transport inside ripples, forced by instantaneous pressure profiles along the sediment-water interface (SWI) with 0.1-s temporal resolution. The transient pressure profiles were taken from a field data–driven large-eddy simulation model of wave-driven oscillatory flow. The simulations suggest that in elastic, permeable, and saturated sediment, a time-averaged representation of the flow field may be inadequate and that this also leads to shortcomings in how transport is modeled. Bursts in fluid flushing occur when high-frequency pressure fluctuations were considered, leading to larger long-term average fluid fluxes compared to a steady flow field driven by a time-averaged pressure profile. The pressure perturbations along the SWI propagate within a few milliseconds to meter depths within the sediment leading to strongly transient porewater velocity fields. This leads to enhanced dispersion of solutes and larger time-averaged solute fluxes. However, enhanced solute flux across the SWI diminished through time with increasing permeability. The high-frequency transient pressures and sediment elastic properties we considered have been largely ignored and unrecognized. Future observational and modeling studies should consider these processes, especially since they mediate timing-sensitive biogeochemical reactions.</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"23-37"},"PeriodicalIF":0.0,"publicationDate":"2011-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1151658","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The influence of current speed and vegetation density on flow structure in two macrotidal eelgrass canopies","authors":"Jessica R. Lacy,&nbsp;Sandy Wyllie-Echeverria","doi":"10.1215/21573698-1152489","DOIUrl":"10.1215/21573698-1152489","url":null,"abstract":"<div>\u0000 <p>The influence of eelgrass (<i>Zostera marina</i>) on near-bed currents, turbulence, and drag was investigated at three sites in two eelgrass canopies of differing density and at one unvegetated site in the San Juan archipelago of Puget Sound, Washington, USA. Eelgrass blade length exceeded 1 m. Velocity profiles up to 1.5 m above the sea floor were collected over a spring-neap tidal cycle with a downward-looking pulse-coherent acoustic Doppler profiler above the canopies and two acoustic Doppler velocimeters within the canopies. The eelgrass attenuated currents by a minimum of 40%, and by more than 70% at the most densely vegetated site. Attenuation decreased with increasing current speed. The data were compared to the shear-layer model of vegetated flows and the displaced logarithmic model. Velocity profiles outside the meadows were logarithmic. Within the canopies, most profiles were consistent with the shear-layer model, with a logarithmic layer above the canopy. However, at the less-dense sites, when currents were strong, shear at the sea floor and above the canopy was significant relative to shear at the top of the canopy, and the velocity profiles more closely resembled those in a rough-wall boundary layer. Turbulence was strong at the canopy top and decreased with height. Friction velocity at the canopy top was 1.5–2 times greater than at the unvegetated, sandy site. The coefficient of drag <i>C</i>_<i>D</i> on the overlying flow derived from the logarithmic velocity profile above the canopy, was 3–8 times greater than at the unvegetated site (0.01–0.023 vs. 2.9 × 10^− 3).</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"38-55"},"PeriodicalIF":0.0,"publicationDate":"2011-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1152489","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interactions between the mat-forming alga Didymosphenia geminata and its hydrodynamic environment","authors":"Scott T. Larned,&nbsp;Aaron I. Packman,&nbsp;David R. Plew,&nbsp;Kay Vopel","doi":"10.1215/21573698-1152081","DOIUrl":"10.1215/21573698-1152081","url":null,"abstract":"<div>\u0000 <p>Benthic autotrophs in oligotrophic rivers must adapt to and modify their hydrodynamic environment to balance the conflicting requirements of minimal drag (to minimize detachment risks) and maximal exposure to turbulent flow (to maximize nutrient acquisition). We explored flow–organism interactions using the benthic, freshwater alga <i>Didymosphenia geminata. D. geminata</i> forms large mats in swift, oligotrophic alluvial rivers. The physical properties that allow <i>D. geminata</i> to resist detachment and proliferate under these harsh conditions are unknown. We transplanted cobbles with attached <i>D. geminata</i> mats from a riverbed to a flume and used velocimetry and microelectrode profiling to measure hydrodynamic and transport conditions above and within the mats over a wide range of flows. We then removed the mats from the cobbles and repeated the velocimetry measurements. Experiment results indicated that <i>D. geminata</i> mats reduce form-induced stresses and near-bed turbulent velocity fluctuations, which may reduce the risk of detachment. <i>D. geminata</i> mats also increase turbulent shear stress just above mat surfaces, which may enhance water column–mat solute exchange. High friction associated with flow at mat surfaces leads to very low velocities and predominantly diffusive transport within mats, which may in turn favor the retention of solutes derived from organic matter within and below mats. Enhanced mass transfer at mat surfaces and effective solute retention in mat matrices suggest a mechanism by which <i>D. geminata</i> cells acquire nutrients from different sources: advection-dominated transport of water-column nutrients to cells at mat surfaces, and diffusion-dominated transport from decomposing organic matter within mats, with minimal advective losses.</p>\u0000 </div>","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"4-22"},"PeriodicalIF":0.0,"publicationDate":"2011-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1152081","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The launch of Limnology and Oceanography: Fluids and Environments, a new interdisciplinary journal","authors":"Josef Daniel Ackerman","doi":"10.1215/21573698-1154398","DOIUrl":"10.1215/21573698-1154398","url":null,"abstract":"<p>Welcome to <i>Limnology and Oceanography: Fluids and Environments</i> (<i>L&amp;O:F&amp;E</i>), the new journal published by the American Society of Limnology and Oceanography (ASLO) and Duke University Press.</p><p>Our aims and scope are to publish interdisciplinary papers dealing with the interplay of fluid dynamics and biological, chemical, and/or geological processes in aquatic systems. We encourage manuscripts treating research in any aspect of limnology and oceanography in which advection and/or diffusion or the mechanics of the medium interact with biological, chemical, or geological processes. We recognize a variety of approaches, including modeling, theory, and empiricism in the forms of both observation and experiments, from large-scale currents to organism-induced motions and molecular-level transfers. Interactions of fluid dynamics and transport processes with biology, chemistry, or geology, or any combinations of them are essential to <i>L&amp;O:F&amp;E</i> papers and define the uniqueness of the journal. Environments of interest include oceans, coastal seas, estuaries, rivers, streams, lakes, ponds, reservoirs, groundwaters, and wetlands, as well as the mats, sediments, and rocks that underlie and are permeated by these waters and the atmosphere immediately above them. Appropriate topic areas include, but are not limited to, carbon dynamics, gas exchange, diagenesis, animal movement, hyporheic flows, life in boundary layers, sediment transport, particle coagulation, flow effects on ecosystems, groundwater discharge, biological feeding and growth, environmental fluid dynamics, biogeochemistry, hydrothermal flows, gel formation, nutrient uptake and release, and contaminant dispersal.</p><p>The statement that water is the key characteristic that links aquatic scientists is by no means controversial. Thirty years ago the interface between fluid dynamics and biology, chemistry, and geology was being explored by a handful of scientists who recognized the important contributions that each of these seemingly disparate fields could make to one another. Indeed, a number of seminal books emerged that stimulated several generations of students. Among them were the late <span>Akira Okubo's (1980)</span> <i>Diffusion and Ecological Problems</i> and <span>Steve Vogel's (1981)</span> <i>Life in Moving Fluids</i>. Of them, Okubo's was the more mathematical, stemming from his background and experience as a chemical-physical oceanographer, whereas Vogel's was more phenomenological, speaking directly to many who were students of biology. Both served, and continue to serve in their revisions (<span>Vogel 1994</span>; <span>Okubo and Levin 2001</span>), as excellent introductions and inspirations because they highlight and synthesize the interface between biology and fluids and, to a lesser extent, chemistry and mathematics.</p><p>It was not unreasonable for a beginning graduate student to assume that everyone else in science was like-minded. A rude a","PeriodicalId":100878,"journal":{"name":"Limnology and Oceanography: Fluids and Environments","volume":"1 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2011-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1215/21573698-1154398","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66027581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}