Effect of suspended kelp culture on water exchange as estimated by in situ current measurement in Sanggou Bay, China

• Suspended kelp culture affects water exchange by changing the spatial pattern of tidal fluxes but not the tidal prisms
• Tidal fluxes at surface reduced by 70% at northern entrance from kelp seeding to harvesting periods
• Tidal fluxes at near bottom increased 140% at central entrance from kelp seeding to harvesting periods
• The total water exchange did not significantly reduce from the kelp seeding to kelp harvesting periods

Water exchange between Sanggou Bay and the Yellow Sea in China was estimated based on current profiles measured by four bottom-mounted Acoustic Doppler Current Profilers at the entrance of the bay during the kelp seeding and kelp harvesting periods. Hydrodynamics in the bay were dominated by tidal currents, especially semi-diurnal constituents. The effect of suspended kelp culture on the water exchange was investigated in terms of the tidal flux and tidal prism of the bay during a semi-diurnal period. Suspended kelp culture was found to significantly affect water exchange by changing the spatial pattern of the tidal flux but not the tidal prism. The inward tidal flux was reduced by 10% to 70% in the upper layers in the kelp seeding to kelp harvesting periods. Meanwhile, the inward tidal flux was increased by 10% to 140% in the lower layers. The mean inward tidal prism was 2.31 × 108 m3 and 2.17 × 108 m3 during the kelp seeding period and kelp harvesting period, respectively. Comparing with previous numerical simulations, our results did not show a prominent reduction in total water exchange across the entrance of the bay by suspended kelp culture.