Using a Digital Echosounder to Estimate Eelgrass (Zostera marina L.) Cover and Biomass in Kwangyang Bay

doi:2008.23.1.83

Algae > Volume 23(1); 2008 > Article

Algae 2008;23(1): 83-90. doi: https://doi.org/10.4490/algae.2008.23.1.083

Keunyong Kim, Ju-hyoung Kim and Kwang Young Kim^*

Department of Oceanography, Chonnam National University, Gwangju 500-757, Korea

*Corresponding Author

Email: kykim@chonnam.ac.kr

ABSTRACT

Eelgrass beds are very productive and provide nursery functions for a variety of fish and shellfish species. Management for the conservation of eelgrass beds along the Korean coasts is critical, and requires comprehensive strategies such as vegetation mapping. We suggest a mapping method to spatial distribution and quantify of eelgrass beds using a digital echosounder. Echosounding data were collected from the northeast part of Kwangyang Bay, on the south of Korea, in March, 2007. A transducer was attached to a boat equipped with a DGPS. The boat completed a transect survey scanning whole eelgrass beds of 11.7 km2 with a speed of 1.5-2 m s-1 (3-4 knot). The acoustic reflectivity of eelgrass allowed for detection and explicit measurements of canopy cover and height. The results showed that eelgrass bed was distributed in depth from 1.19 to 3.6 m (below MSL) and total dry weight biomass of 4.1 ton with a vegetation area of 4.05 km2. This technique was found to be an effective way to undertake the patch size and biomass of eelgrass over large areas as nondestructive sampling.

Key words: acoustic reflectivity, biomass, canopy cover, digital echosounder, eelgrass beds, Kwangyang Bay, vegetation