WAMSI 2 - Dredging Node - Project 5.5.1 - Defining thresholds and indicators of primary producers - Seagrass pressure-response relationships - Experiment 1

Objectives of Project 5.5 are to:
(1) determining the pressure:response relationships that relate the effects of dredging-generated sediments on tropical primary producers,
(2) examine the pathways, rates and timeframes of recovery from impacts and;
(3) identify and examine the effects of key environmental variables on the pressure:response relationships and recovery.

Specifically *Experiment 1* will be studying "Effect of different intensity, duration & timing of light reductions on seagrasses (Laboratory)"

Measurements included:
Absorbancy Factors
Biomass - Above ground mass (g DW per pot), Below ground mass (g DW per pot), Total plant mass (g DW per pot)
Carbohydrates (%DW) and Starch (%DW)
Growth & Morphology - leaf area (cm2), shoot density (per pot), Shoot production rate (shoots d-1)
Nutrient & isotope data - Leaf ‰ 15 Nitrogen, Leaf ‰ 13 Carbon, Leaf Nitrogen (% DW) Leaf Carbon (% DW) Leaf Carbon to Nitrogen ratio (g g-1)
Photosynthesis - Electron transport rate (um photons m-2 s-1), Alpha (um photons m-2 s-1), Half-saturating irradiance (um photons m-2 s-1)
Pot Biomass - Pot mass (mass of all plants in a pot, g DW per pot)

Species studied included - Cymodocea serrulata and Halodule uninervis

项目5.5的目标如下：
(1) 明确疏浚沉积物对热带初级生产者的胁迫效应对应的压力-响应（pressure:response）关系；
(2) 探究干扰后恢复的路径、速率与时间框架；
(3) 识别并探究关键环境变量对压力-响应关系及恢复过程的影响。

具体而言，**实验1**将围绕"不同强度、时长与时机的光照削减对海草的影响（实验室研究）"展开研究。

本次实验的测定指标如下：
吸光度参数
生物量：地上生物量（g DW/盆，干重，Dry Weight, 缩写DW）、地下生物量（g DW/盆）及植株总生物量（g DW/盆）
碳水化合物（占干重百分比）与淀粉（占干重百分比）
生长与形态指标：叶面积（cm²）、茎枝密度（每盆茎枝数）、茎枝生成速率（茎枝·天⁻¹）
营养与同位素数据：叶片δ¹⁵N值、叶片δ¹³C值、叶片氮含量（占干重百分比）、叶片碳含量（占干重百分比）及叶片碳氮比（g·g⁻¹）
光合生理指标：电子传递速率（μmol光子·m⁻²·s⁻¹）、初始量子效率α（μmol光子·m⁻²·s⁻¹）、半饱和光强（μmol光子·m⁻²·s⁻¹）
盆体生物量：盆内全部植株总生物量（g DW/盆）

本次实验选用的研究物种为：齿叶丝粉藻（Cymodocea serrulata）与单脉海菖蒲（Halodule uninervis）