Water pumping and analysis of flow in burrowing zoobenthos: an overview
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588; e-ISSN 1573-5125, more
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| Keywords |
Aquatic communities > Benthos
Irrigation
Sedimentary structures > Flow structures
Technology
Marine/Coastal |
| Authors | | Top |
- Riisgård, H.U.
- Larsen, P.S.
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| Abstract |
Burrowing animals maintain contact with the water above the sediment by pumping water through a tube system and therefore measurements of water pumping rate of burrowing animals is of crucial importance for the study of many processes both within and above the sea floor. This review deals with the measuring of water pumping and the analysis of flow generated by burrowing deposit- and filter-feeding zoobenthos in order to determine the type of pump and mechanisms involved, flow rate, pump pressure, and pumping power. The practical use of fluid mechanical principles is examined, and it is stressed that not only the pump pressure that a burrowing animal can apply is of interest for assessing the energy cost of pumping, but also the distribution of excess pressure along its burrow is of importance for assessing the seepage flow of oxygen-rich water into the sediment surrounding the burrow because this bioirrigation exerts a considerable effect on the chemistry and microbiology of sediments. Dense populations of burrowing filter-feeding zoobenthos also interact with the water above the sediment interface and this is reflected in the development of phytoplankton concentration profiles above the filter-feeding animals. In stagnant situations the near-bottom water may be depleted of food particles, depending on the population filtration rate and the intensity of the biomixing induced by the filtering activity. But moderate currents and the biomixing can presumably generate enough turbulence to facilitate mixing of water layers at the sea bed with the layers above where food particle concentrations are relatively higher. Following a brief summary of types of burrowing benthic animals, common methods for measuring pumping rates are described along with examples. For estimating the required pump pressure, biofluid mechanical theory for flow in tube–pump systems is summarised (elaborated in Appendix A). Specific examples are given to illustrate general principles and to give an idea of typical values of flow rate, pressure drop and power involved. Finally, some flow effects generated by burrowing animals in and above the sediment are described. |
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