Investigations on Fucus vesiculosus and Fucus serratus at outer Kiel Fjord over one year (August 2012 - July 2013)

Macroalgae, especially perennial species, are exposed to a seasonally variable fouling pressure. It was hypothesized that macroalgae regulate their antifouling defense to fouling pressure. Over one year, the macrofouling pressure and the chemical anti-macrofouling defense strength of the brown algae Fucus vesiculosus and Fucus serratus were assessed with monthly evaluation. The anti-macrofouling defense was assessed by means of surface-extracted Fucus metabolites tested at near-natural concentrations in a novel in situ bioassay. Additionally, the mannitol content of both Fucus species was determined to assess resource availability for defense production. The surface chemistry of both Fucus species exhibited seasonal variability in attractiveness to Amphibalanus improvisus and Mytilus edulis. Of this variability, 50-60% is explained by a sinusoidal model. Only F. vesiculosus extracts originating from the spring and summer significantly deterred settlement of A. improvisus. The strength of macroalgal antifouling defense did not correlate either with in situ macrofouling pressure or with measured mannitol content, which, however, were never depleted.

大型藻类（Macroalgae），尤其是多年生类群，长期处于随季节波动的大型附着污损压力之下。研究人员提出假说：大型藻类可根据污损压力调控其抗附着污损防御机制。本研究在为期一年的周期内，通过月度评估，对两种褐藻——泡叶藻（Fucus vesiculosus）和锯齿墨角藻（Fucus serratus）的大型附着污损压力以及化学型抗大型附着污损防御强度进行了测定。本次研究采用新型原位生物测定（in situ bioassay）方法，以近自然浓度测试墨角藻表面提取的代谢产物，以此表征其抗附着污损防御能力；此外还测定了两种墨角藻的甘露醇（mannitol）含量，以评估其用于防御物质合成的资源可获得性。两种墨角藻的表面化学特性对纹藤壶（Amphibalanus improvisus）和紫贻贝（Mytilus edulis）的吸引性呈现季节波动性，其中50%至60%的波动可通过正弦模型（sinusoidal model）解释。仅春季和夏季采集的泡叶藻提取物，可显著抑制纹藤壶的附着。大型藻类的抗附着污损防御强度既未与原位测得的大型附着污损压力呈现相关性，也与测得的甘露醇含量无关联，不过实验期间甘露醇含量始终未出现耗竭情况。