The Effect of Ulvoid Macroalgae on the Inorganic Carbon Utilization by an Intertidal Seagrass Thalassia hemprichii

利用沉水性葉綠素螢光分析儀實測石蓴類海藻對期間帶海草Thalassia hemprichii於無機碳源使用的影響

劉少倫(Shao-Lun Liu) ； 王璋龍(Wei-Lung Wang) ； Danlio T. DY ； 傅正昌(Cheng-Chang Fu)

《Botanical Bulletin of Academia Sinica》 46卷3期 (2005/07) Pp. 197-203

https://doi.org/10.7016/BBAS.200507.0197

摘要

Blooms of ulvoid macroalgae (mainly Enteromorpha and Ulva) have covered 80% of the intertidal seagrass bed at Wanlitung, southern Taiwan, effectively shading the seagrasss species Thalassia hemprichii resulting in a decrease in photosynthetic performance and low inorganic carbon (C(subscript i)) uptake. We looked for evidence of C(subscript i) limitation and investigated the C(subscript i) utilization characteristics of ulvoid-free and ulvoid-covered T. hemprichii. The rapid light curve (RLC) function of the Diving-PAM (Diving-PAM. Walz, Germany) was used to measure in situ photosynthetic performance (based on the effective quantum yield of PSⅡ [Y] values) of intact seagrasses that were placed in small incubating chambers. Significantly, a lower RETR(subscript max) (maximum relative electron transport rate) and E(subscript k) (light intensity at the onset of saturation) were noted in the ulvoid-covered compared to the ulvoid-free T. hemprichii, suggesting that the former has acclimatized to the low light environment becoming a ”shade type” plant. The ulvoid-covered T. hemprichii showed some evidence of C(subscript i) limitation since a significant increase in RETR(subscript max) (up to 46%; P＜0.05) was noted after an increase in the concentration of NaHCO3 from 2.2 (normal seawater) to 6.2mM. In terms of C(subscript i) utilization characteristics, T. hemprichii could directly absorb HCO3(superscript -) as the major C(subscript i) source but partially depended on the extracellular carbonic anhydrase (CA) to convert HCO3(superscript -) to CO2 prior to uptake in the ulvoid-free, high light-adapted populations. A wastewater stream with a high nutrient load coming from the urbanized area may have caused the frequent blooms of ulvoid macroalgae.

關鍵字

重碳酸鹽 ； 窒息 ； 光合作用 ； 台灣 ； 石蓴類藻華

並列摘要

Blooms of ulvoid macroalgae (mainly Enteromorpha and Ulva) have covered 80% of the intertidal seagrass bed at Wanlitung, southern Taiwan, effectively shading the seagrasss species Thalassia hemprichii resulting in a decrease in photosynthetic performance and low inorganic carbon (C(subscript i)) uptake. We looked for evidence of C(subscript i) limitation and investigated the C(subscript i) utilization characteristics of ulvoid-free and ulvoid-covered T. hemprichii. The rapid light curve (RLC) function of the Diving-PAM (Diving-PAM. Walz, Germany) was used to measure in situ photosynthetic performance (based on the effective quantum yield of PSⅡ [Y] values) of intact seagrasses that were placed in small incubating chambers. Significantly, a lower RETR(subscript max) (maximum relative electron transport rate) and E(subscript k) (light intensity at the onset of saturation) were noted in the ulvoid-covered compared to the ulvoid-free T. hemprichii, suggesting that the former has acclimatized to the low light environment becoming a ”shade type” plant. The ulvoid-covered T. hemprichii showed some evidence of C(subscript i) limitation since a significant increase in RETR(subscript max) (up to 46%; P＜0.05) was noted after an increase in the concentration of NaHCO3 from 2.2 (normal seawater) to 6.2mM. In terms of C(subscript i) utilization characteristics, T. hemprichii could directly absorb HCO3(superscript -) as the major C(subscript i) source but partially depended on the extracellular carbonic anhydrase (CA) to convert HCO3(superscript -) to CO2 prior to uptake in the ulvoid-free, high light-adapted populations. A wastewater stream with a high nutrient load coming from the urbanized area may have caused the frequent blooms of ulvoid macroalgae.

並列關鍵字

Bicarbonate ； Photosynthesis ； Taiwan ； Ulvoid bloom