COMPARATIVE EFFECTS OF WATER-COLUMN NITRATE ENRICHMENT ON EELGRASS ZOSTERA-MARINA, SHOALGRASS HALODULE-WRIGHTII, AND WIDGEONGRASS RUPPIA-MARITIMA
COMPARATIVE EFFECTS OF WATER-COLUMN NITRATE ENRICHMENT ON EELGRASS ZOSTERA-MARINA, SHOALGRASS HALODULE-WRIGHTII, AND WIDGEONGRASS RUPPIA-MARITIMA
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DOI：
10.3354/meps105121
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发表时间：
1994-02-01
影响因子：
2.5
通讯作者：
COOKE, JE
中科院分区：
文献类型：
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作者：
BURKHOLDER, JM;GLASGOW, HB;COOKE, JE
在夏末秋季的实验中生态系统中，我们检查了未添加硝酸盐的大叶藻码头的芽生产（通常环境水柱浓度<2μM NO3--N）与先前暴露于低硝酸盐富集（在异常凉爽的春季期间向水中脉冲添加5μM NO3--N d-1 12周）的大叶草的芽生产。在夏末秋末，先前富集的植物承受更高的硝酸盐负荷（10μM NO3--N d-1，持续14周），而对照植物则像春季一样保持不添加硝酸盐的状态。我们还比较了最近田间移植的 Z. marina、Halodule wrightii 和 Ruppia maritima 在添加和不添加 10 μM 水柱 NO3--N d-1 的情况下秋季的芽产量。使用低水交换量 (10% d-1) 来模拟受庇护的海湾或泻湖的条件，并通过用中性密度屏幕覆盖中层来模拟涨潮时的光减少，该屏幕按轮流计划在 3 小时 d-1 内将入射光减少 30%。在春季低浓度的 NO3--N 暴露期间，富集和未富集 Z 码头的芽产量相当。然而，在春季和秋季富含硝酸盐的鳗草的芽产量显着低于未富含硝酸盐的对照植物。这种减少与藻类生长引起的光照减少无关，表明长期暴露于水柱硝酸盐对 Z 码头产生了直接不利影响。最近移植的没有先前富集历史的鳗草也显示出在适度升高的硝酸盐下横向生长减少的趋势。相反，相对于对照的生长，硝酸水柱对H. wrightii 的生长有轻微的刺激，而R. maritima 的生长则受到高度的刺激。到秋季实验结束时，Z marina (+/- NO3--N)、H. wrightii (+/- NO3--N) 和未富集的 R. maritima 使芽密度增加了小于或等于 50%，而富含硝酸盐的 R. maritima 将芽产量增加了 > 300%。数据表明，通过在鳗草草甸消失的富含硝酸盐的水域进行移植作为管理策略，可以成功地建立赖特氏藻或海藻。与 Z marina 不同，这些物种显然已经发展出更有效地控制硝酸盐吸收和代谢的生理机制。
In an experimental mesocosm system during late summer-fall, we examined shoot production by eelgrass Zostera marina without nitrate additions (generally with ambient water-column concentrations < 2 muM NO3--N) versus production by eelgrass that previously had been exposed to low nitrate enrichment (pulsed additions of 5 muM NO3--N d-1 to the water for 12 wk during an unusually cool spring season). During late summer-fall, the previously enriched plants were subjected to higher nitrate loading (10 muM NO3--N d-1 for 14 wk), while control plants were maintained without nitrate additions as in spring. We also compared shoot production in fall by recent field transplants of Z. marina, Halodule wrightii, and Ruppia maritima with and without additions of 10 muM water-column NO3--N d-1. Low water exchange (10 % d-1) was used to simulate conditions in sheltered embayments or lagoons, and light reduction from high tide was simulated by covering the mesocosms with neutral-density screens that reduced incident light by 30 % for 3 h d-1 on a rotating schedule. Shoot production by both enriched and unenriched Z marina was comparable during the spring low-level NO3--N exposure. However, eelgrass enriched with nitrate in both spring and fall attained significantly lower shoot production than control plants without enrichment. This decrease, unrelated to light reduction from algal growth, suggests a direct adverse effect of long-term water-column nitrate exposure on Z marina. The more recent transplants of eelgrass without prior enrichment history also showed a trend for decreased lateral growth under moderately elevated nitrate. In contrast, H. wrightii was slightly stimulated and R. maritima was highly stimulated by water-column nitrate relative to growth of controls. By the end of the fall experiment, Z marina (+/- NO3--N), H. wrightii (+/- NO3--N), and unenriched R. maritima had increased shoot densities by less-than-or-equal-to 50%, whereas nitrate-enriched R. maritima increased shoot production by > 300 %. The data indicate that H. wrightii or R. maritima could be established successfully by transplanting efforts as a management strategy in nitrate-enriched waters where eelgrass meadows have disappeared. Unlike Z marina, these species apparently have developed physiological mechanisms to more effectively control nitrate uptake and metabolism.