The distribution of large floating seagrass (Zostera marina) clumps in northern temperate zones of Bohai Bay in the Bohai Sea, China

Abstract

Seagrass meadows (Zostera marina) are important coastal ecosystems with high levels of productivity and biodiversity. They are subject to considerable natural and anthropogenic threats in China, such as oyster and snail aquaculture, wastewater discharge, electro-fishing, shellfish collection, typhoons and floods. When seagrass communities are disturbed, they can become removed from the sediment and converted into floating clumps, which then serve as marine hot spots attracting a variety of marine organisms that then inhabit them. They are important nursery habitats for many economic fish such as red drum (Sciaenops ocellatus), Atlantic cod (Gadus morhua), queen conch (Strombus gigas), and blue crab (Callinectes sapidus). Thus, it is necessary to study the distribution and biological characteristics of these floating seagrass clumps. In September 2016 we observed large scale floating Z. marina clumps in the northernmost area of Bohai Bay (38{degrees}571.14\"-39{degrees} 041.28\" N, 118{degrees}4523.22\"-118{degrees}476.96\" E), in the Bohai Sea, China. We observed characteristics that precluded their origination from the nearby Caofeidian seagrass meadows. Two research cruises were undertaken, during which we did not observe other marine organisms accompanying these floating Z. marina clumps. The dominant frond lengths were 40-50 cm, with less than 5% of the total number of fronds found in larger size categories (80-90 and 90-100 cm). We aim to pursue future research into the breakdown and dislodgement characteristics of Z. marina clumps and the processes whereby they sink and integrate with the sediment.