Zostera marina (eelgrass) growth and survival along a gradient ofnutrients and turbidity in the lower Chesapeake Bay

Survival of transplanted Zostera marina L. (eelgrass), Z. marina growth,and environmental conditions were studied concurrently at a number of sitesin a southwestern tributary of the Chesapeake Bay to elucidate the factorslimiting macrophyte distribution in this region. Consistent differences insurvival of the transplants were observed, with no long-term survival at anyof the sites that were formerly vegetated with this species but thatcurrently remain unvegetated. Therefore, the current distribution of Z.marina likely represents the extent of suitable environmental conditions inthe region, and the lack of recovery into historically vegetated sites is notsolely due to lack of propagules. Poor long-term survival was related toseasonally high levels of water column light attenuation. Fall transplantsdied by the end of summer following exposure to levels of high springturbidity (K(d) > 3.0). Accumulation of an epiphyte matrix during the latespring (0.36 to 1.14 g g-1 dry wt) may also have contributed to thisstress. Differences in water column nutrient levels among sites during thefall and winter (10 to 15 ??M dissolved inorganic nitrogen and 1 ??Mdissolved inorganic phosphates) had no observable effect on epiphyteaccumulation or macrophyte growth. Salinity effects were minor and there wereno symptoms of disease. Although summertime conditions resulted indepressions in growth, they did not alone limit long-term survival. It issuggested that water quality conditions enhancing adequate seagrass growthduring the spring may be key to long-term Z. marina survival and successfulrecolonization in this region.