Wax and wane of eelgrass Zostera marina and water column silicon levels

Abstract

Long-term observations in an enclosed estuanne branch in The Netherlands showed a remarkably strong correlation between water column levels of dissolved sihcon (DSi) and standlng stock of eelgrass Zostera marina. Si levels in the leaves of Z. marina varied between 0.02 and 0.66% of tissue dry weight, they were lower in the declining population than in other populations in neighbouring areas. We hypothesize that decreased concentrations of DSi, which may coincide with eutrophlcation of coastal waters, may be a factor in the worldwide decllne of estuarine eelgrass populations whose significance has so far been ignored.