The seagrass, Zostera Marina L.: plant morphology and bed structure in relation to sediment ammonium in Izembek Lagoon, Alaska

The relationship between the morphology of eelgrass, Zostera marina L., and ammonium in the sediment interstitial water was examined. The size of eelgrass plants collected from an intertidal terrace showed a consistent relationship with the size of the interstitial ammonium pool. Leaf area, length, and width all showed a linear increase in size towards stations having higher ammonium, while within the stations with the highest ammonium the leaf size was relatively unchanged. The size and extent of the root system in eelgrass varied across the environmental gradient. Eelgrass shoot density and flower abundance were inversely correlated with sediment nitrogen across the eelgrass meadow. Shoot density described a strong logarithmic relation with interstitial ammonium, opposite to the relationships for leaf size. Comparison of these results indicates the importance of sediment nitrogen in determining eelgrass bed structure.