The combined effect of planting density and sediment fertilization on survival, growth and physiology of eelgrass Zostera marina.

We subjected shoots of eelgrass Zostera marina to different combinations of planting density [300 (control), 450, 600, 750, 900 shoots m] and sediment fertilization [0 (control), 35, 70, 105, 140 g m] for 6 weeks under controlled conditions. We measured eelgrass responses in terms of survivorship, growth, productivity, leaf pigmentation and carbohydrate concentrations. The ramet frequency of Z. marina reached 47.8 % when exposed to the combination of 600 shoots m and 70 g m, which was 3.2 times higher than that of shoots under the control. Survival analysis combined with growth assessment suggested that the optimal ranges of planting density and sediment fertilization for the propagation of Z. marina shoots were 501 to 530 shoots m and 51 to 60 g m, respectively. The promotion of survival and propagation of Z. marina that stemmed from planting density and sediment fertilization mainly depended on the increase of chlorophyll content and accumulation of non-structural carbohydrate. The total chlorophyll content of Z. marina leaves exposed to the combination of 600 shoots m and 70 g m was 2.1 times higher than that of shoots under the control. The results will provide data that could prove helpful in the development of efficient artificial propagation technology for Z. marina shoots.