Adult seagrass shoots govern the fate of seedlings in a large seagrass meadow in the eutrophic bay in northern China

Seagrasses are submerged marine angiosperms, which play key ecological roles in coastal ecosystems. Seagrass Zostera marina L. (eelgrass) is a marine founding species and is the most common seagrass species on the Atlantic and Pacific coasts of the temperate northern hemisphere.

Bohai Bay, the representative semi-enclosed bay in northern China, has experienced severe eutrophication and overfishing in recent decades. There is a large eelgrass bed located northwest of eutrophic bay.

Recently, a research team led by Professor Zhou Yi from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) provided new insights into the variability of Z. marina population recruitment in the large seagrass .

The study was published in Marine Pollution Bulletin April 7.

Researchers studied eelgrass density, height, biomass, plant reproductive effort, and seed bank density to analyze the temporal dynamics of asexual growth and sexual reproduction of eelgrass. They also identified the nutritional status of seawater and seagrass beds, as well as their ecological interactions in the large seagrass meadow.

They found that eelgrass seedlings appeared from April to July and that their density reached the highest level (~220 shoots m^-2) in May before decreasing. No seedlings were found in the vegetated areas in June 2019, although a considerable number of seedlings, with a density of about 110 shoots m^-2, survived in gaps in the seagrass bed. Vegetative shoot density increased significantly during the fall sampling period, with vegetative shoot density more than quadrupling.

“Asexual growth has played an important role in maintaining existing grasslands, and sexual reproduction has played a critical role in colonizing new areas. ‘seagrass,’ said Dr. Xu Shaochun, first author of the study. This discovery will provide fundamental information for the large-scale restoration of seagrass in northern China.

Researchers also analyzed nutrient concentrations in seawater and seagrass beds and found that the nutrient resources of nitrogen (N) and phosphorus (P) there met the demand for seagrass growth. . N/P ratios of seawater and seagrass beds indicated a limitation of N relative to P in the eutrophic bay based on the Redfield ratio of seagrass beds (25–30).

“It is likely that efficient nutrient uptake by seagrass plays an important role in reducing the likelihood of a red tide in the study area,” said Professor Zhou, the corresponding author of the study. ‘study.