Experimental investigation of eelgrass seed settling and clustering for ecosystem restoration

Eelgrass is a type of aquatic vegetation that is an essential part of the ecosystem in the Great Bay Estuary in New Hampshire, USA. This vegetation performs many ecosystem functions such as providing habitat for marine organisms, attenuating waves and currents, and reducing coastal erosion. Unfortunately, the eelgrass population in the estuary has been in decline over the past several decades. A proposed method to increase the eelgrass population and help with reproduction is to harvest eelgrass seeds from nearby locations and introduce these seeds into the estuary. So far, this technique has not produced a significant increase in eelgrass population due to the seeds not settling into the sediment and germinating. The work presented herein will provide preliminary results discussing which water conditions are the most suitable for eelgrass seed dissemination, settling, and germination.

The laboratory tests are performed in a 10m long oscillating water tunnel with a vegetative meadow made from eelgrass mimics. The water tunnel can be set-up with either a sediment bed or a vegetative canopy and the water can be run as unidirectional or oscillatory. The results presented here are for both a sediment bed and a vegetative canopy in still and unidirectional flow. We present statistics for where cylidrical model eelgrass seed particles are most likely to settle given various vegetation patterns, seed release points, and water conditions.