Production of reproductive shoots, vegetative shoots, and seeds in populations of Ruppia maritima L from the Chesapeake Bay, Virginia

The production of reproductive shoots, vegetative shoots, and seeds was characterized for Ruppia maritima populations in the Virginia portion of Chesapeake Bay in 1988 and 1989. The study locations included two previously unvegetated sites recently colonized by R. maritima in the Rappahannock River and an established site and an irregularly flooded marsh panne site, both in the York River. A corer was used to collect plant material, which was then separated into reproductive shoots, vegetative shoots, and seeds. Sampling took place at approximately 2-week intervals from the time of first observation of flowering shoots until reproductive senescence. Reproductive shoot and seed production were high for all sites, particularly the previously unvegetated sites. The percent of reproductive shoots ranged from less than one percent to 52 percent. One previously unvegetated site produced 23,390 seeds m(-2) in 1988, the highest level of seed production measured during this study. Dramatic decreases in production from 1988 to 1989 at two of the study locations, the salt panne and one previously unvegetated site, are attributable to the effects of drought and cownose ray (Rhinoptera bonasus) activity, respectively. High levels of seed production, frequently above 20,000 seeds m(-2), and their eventual dispersal may account for the rapid colonization in certain areas of Chesapeake Bay by R. maritima.