Ecological Archives E085-091-A3

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 C. Upwelling events and regional changes in larval supply.

Despite large spatial variation, the larval supply changed concordantly among stations over short time scales. This regional change in time suggested that downwelling and upwelling events may control the regional supply of cyprid larvae. Wind direction and sea level changes were used as indicators of downwelling/upwelling events and were correlated to changes in cyprid supply. Wind data (station Nordkoster) and sea level data (station Kungsvik) were collected from within 5 km of the study area. Fig. C1 shows that cyprid supply increases with westerly winds leading to downwelling. This is further supported by the positive correlation between larval supply and sea level (Fig. C2). These correlations suggest that larval supply increases during downwelling events caused by onshore transport.

 
   FIG. C1. Daily water column larval concentration of Balanus improvisus  (mean no. individuals/L) during weeks 27 and 30 plotted against sea level (cm), (Spearman rank correlation, Z = 3.5, P < 0.01).

 

 
   FIG. C2. Daily concentrations of cyprids in the water column during weeks 27 and 30 as a function of wind direction. The arrows represent different directions of wind direction, where the length correspond to larval concentration (Mann-Whitney U test, Z = -3.33, P < 0.01).


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