Ecological Archives E085-091-A4

Per R. Jonsson, Kent M. Berntsson and Ann I. Larsson. 2004. Linking larval supply to recruitment: flow-mediated control of initial adhesion of barnacle larvae. Ecology 85:2850–2859.

Appendix D. Measurements of local flow speed.

Integrated measurements of local flow speed at the seven study sites was achieved through a wind-fetch model calibrated with short-term deployment of gypsum blocks. Wind data were collected every 3 h at a height of 10 m above sea level ~ 5 km west of the seven study sites. At each station fetch was measured in 10° increments from a nautical chart and combined with the time series of wind speed and direction to calculate significant wave height (Hs) according to the relation (Anonymous 1989):


where Uw is wind speed (m/s) and F is fetch (m). Accordingly, local flow speed was calculated for the same days as each panel was immersed. Wave height was assumed to be approximately proportional to local flow speed according to shallow-water linear wave theory (Denny 1988) These derived flow speeds were calibrated using short-term deployment of gypsum blocks (cast as 60-g cylinders). In the field the blocks were suspended in the water column (1 m depth) at the same sites as the panels. Immersion time was approximately 5 h keeping mass loss within 40% as recommended in Porter et al. (2000). The empirical relation between the estimated wave heights (m) and flow speed (m/s) was:

flow speed = 2.62 × wave height + 0.14 (r2 = 0.93) 

The dissolution rate of gypsum in the field was compared with rates determined in a 7-m laboratory flume (see description of flume in Jonsson and Johansson 1997) in known free-stream velocities, using natural seawater with similar salinity (25–30 ppt) and temperature (13–15° C). Dissolution rate in the flume was near linear in time (r2 = 0.99) for 35% mass loss indicating little effects of reduction in surface area and reduction in diffusive loss due to the accumulation of Ca2+. The relationship between the dissolution rate of gypsum (g/h) and flow speed (m/s) was:

flow speed = 0.28 × dissolution rate – 0.08 (r2 = 0.95)

We estimate a total error for calculated local flow speeds of 20% of the mean.


Anonymous. 1989. Engineering and design - water levels and wave heights for coastal engineering design. EM 1110-2-1414. U.S. Army Corps of Engineers.

Denny, M. W. 1988. Biology and the mechanics of the wave-swept environment. Princeton University Press, Princeton, New Jersey, USA.

Jonsson, P. R., and M. Johansson. 1997. Swimming behavior, patch exploitation and dispersal capacity of a marine benthic ciliate in flume flow. Journal of Experimental Marine Biology and Ecology 215:135–153.

Porter, E. T., L. P. Sanford, and S. E. Suttles. 2000. Gypsum dissolution is not a universal integrator of "water motion". Limnology and Oceanography 45:145–158.

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