Chemical Changes During the Seasonal Cycle of Growth and Decay in Eelgrass (Zostera marina) on the Atlantic Coast of Canada

Abstract

In a submerged bed of eelgrass, newly formed leaves in winter and spring had their maximum levels of total organic matter (90% of dry weight), soluble organic fraction (45%), carbon (42%), and nitrogen (4.8%). These components all decreased as the leaves matured, aged, and died. Soon after death, a leaf had only 70% total organic matter, 28% soluble organic matter, 30% carbon, and 1.5% nitrogen. Intact dead leaves showed little further change in chemical composition. The commonly used crude protein determination (6.25 × nitrogen content) overestimated true protein by up to 180%. The carbon to nitrogen ratio (C:N) was an unreliable index of the nutritional value of the plant. Two growth forms were present, most probably in response to wave action and substrate composition. Daylength, not temperature, most probably controls the seasonal cycle of growth.

Nitrogen dynamics of eelgrass Zostera marina during a late summer period of high growth and low nutrient availability

“…The observed tissue nitrogen contents were in the lower end of the range found in other studies on eelgrass (Harrison & Mann 1975, Thayer et al 1977. Average leaf nitrogen content was below the 1.8 % of dry wt reported from a n experiment under N-limited growth (Short 1987) and was in a range where eelgrass photosynthesis is positively correlated with leaf nitrogen content (Pedersen 1990).…”

Nitrogen Fixation (Acetylene Reduction) by Rhizosphere Sediments of the Eelgrass Zostera marina

“…These values are consistent with previously published results (McRoy and McMillan, 1977). The nitrogen content of green leaves averages about 2.5 % (Patriquin, 1972;Harrison and Mann, 1975;Thayer et al, 1977;Aioi and Mukai, 1980). Assuming that nitrogen is required at this percentage by photosynthesis, one can calculate a total nitrogen demand of from 75 to 100 mg X m-'d-l.…”

δ15N and δ13C reveal differences in carbon flow through estuarine benthic food webs in response to the relative availability of macroalgae and eelgrass

“…Shifts in benthic producer communities also alter the quality of live and detrital food resources available to consumers because macroalgae and seagrasses differ considerably in nutritional value, chemical defenses, and structural components (Harrison & Mann 1975, Zapata & McMillan 1979, Thayer et al 1984, Hay & Fenical 1988. The composition of benthic consumer diets may change in relation to the availability, supply and quality of different food sources.…”