Department of Estuarine and Ocean Sciences, School for Marine Science and Technology, University of Massachusetts Dartmouth, 706 South Rodney French Blvd., New Bedford, MA 02744, USA.
J Environ Manage. 2013 Dec 15;131:129-37. doi: 10.1016/j.jenvman.2013.09.033. Epub 2013 Oct 23.
The relationship of eelgrass survival and habitat quality to water column nitrogen level, phytoplankton biomass, particulate matter, bottom light intensity, and light attenuation was quantified at 70 sites within 19 Massachusetts estuaries through 4 growing seasons (2007-2009, 2011). Sites included a range of eelgrass habitat quality, from stable productive eelgrass beds, to degraded beds, to areas that have lost all eelgrass coverage. Survival of transplanted eelgrass culms was used as a bio-indicator of habitat quality. Habitat quality based upon both changes in stability of eelgrass coverage and transplant survival was positively related to light intensity and percent transmittance. Transplant survival was consistent with habitat designations based upon long-term changes in eelgrass coverage, with lowest light coinciding with areas that lost eelgrass in earlier decades. Bottom light declined in proportion to increases in total nitrogen levels, phytoplankton biomass, and water column particulates determined from long-term water quality data. Field surveys indicated that eelgrass survival required bottom light ≥100 μE/m(2)/s and healthy eelgrass existed where tidally-averaged total nitrogen was less than 0.34 mg/L, equivalent to a mid-ebb tide water-column total nitrogen of <0.37 mg/L. Traditional sampling of water column nitrogen at mid-ebb tide was found to slightly overestimate the average nitrogen level over a complete tidal cycle. However, since long-term, ebb-tide and tidally-averaged total nitrogen are correlated, it is possible to use the monitoring average to guide management until tidally-averaged TN becomes available. Nitrogen thresholds that support eelgrass communities provide a fundamental tool for managing this habitat and for selection of transplant sites aimed at accelerating restoration of this resource under increasing nitrogen loading of the coastal zone.
在四个生长季节（2007-2009 年、2011 年）中，通过 4 个生长季节，在马萨诸塞州 19 个河口的 70 个地点量化了鳗草生存和栖息地质量与水柱氮水平、浮游植物生物量、颗粒物、底层光强和光衰减的关系。这些地点包括鳗草栖息地质量的一系列范围，从稳定的、有生产力的鳗草床到退化的床，再到已经失去所有鳗草覆盖的区域。移植鳗草茎的成活率被用作栖息地质量的生物指标。基于鳗草覆盖稳定性和移植成活率的变化的栖息地质量与光强和透光率呈正相关。移植成活率与基于鳗草覆盖长期变化的栖息地分类一致，最低的光强与几十年前失去鳗草的区域相对应。底层光强随着长期水质数据确定的总氮水平、浮游植物生物量和水柱颗粒物的增加而按比例下降。实地调查表明，鳗草的生存需要底层光强≥100 μE/m2/s，而在潮汐平均总氮小于 0.34mg/L 的地方，健康的鳗草存在，相当于中潮时水柱总氮<0.37mg/L。在中潮时对水柱氮的传统采样被发现略微高估了整个潮汐周期的平均氮水平。然而，由于长期的低潮和潮汐平均总氮是相关的，因此可以使用监测平均值来指导管理，直到获得潮汐平均 TN 为止。支持鳗草群落的氮阈值为管理这种栖息地提供了一个基本工具，并为选择移植地点提供了指导，目的是在沿海地区氮负荷增加的情况下加速这种资源的恢复。
