Contrasting impacts of warming and browning on periphyton

We tested interactive effects of warming (+2°C) and browning on periphyton accrual and pigment composition when grown on a synthetic substrate (plastic strips) in the euphotic zone of sixteen experimental ponds. We found that increased DOC alone, or in combination with warming, resulted in a substantially enhanced biomass accrual of periphyton, illustrating that periphyton is capable of using nutrients associated with DOC, and by this may affect nutrient availability for phytoplankton. However, warming weakened the positive impact of DOC on periphyton accrual, possibly by thermal compensation inferred from altered pigment composition, and/or changes in community composition. Our results illustrate that impacts of climate change on algal growth are multiple, which could have implications for productivity and consumer resource use, especially in shallow areas in northern lakes., Phytoplankton: Phytoplankton chla measurements by filtering 100 mL water, measured using spectrofluorometer (Perkin Elmer LS-55, MA, U.S.A.) with 433nm as excitation and 673nm as emission wavelength. Periphyton: periphyton grown on plastic strips (60cm long, 10cm wide, and 0.75mm thick, excluded the algae growing on the top 10cm), measured pigments (chla, chlc, fucoxanthin) on three dates, at each date a strip that has been introduced is harvested, i.e. no strips that have been harvested before were measured. Duplicate or quadruplicate measurements per pond.,本研究探究了增温（+2℃）与水色褐变（browning）对周丛生物（periphyton）生物量累积与色素组成的交互效应，实验将合成附着基质（塑料条）置于16个实验池塘的真光层（euphotic zone）中开展。研究发现，单独提升溶解性有机碳（DOC）水平，或与增温联合作用时，均可显著增强周丛生物的生物量累积，这表明周丛生物能够利用与溶解性有机碳结合的营养盐，进而可能影响浮游植物（phytoplankton）可获取的营养盐有效性。然而，增温会削弱溶解性有机碳对周丛生物生物量累积的正向作用，该效应可能源于色素组成改变及/或群落组成变化所指示的温度补偿过程。本研究结果显示，气候变化对藻类生长的影响具有多源性，这可能对生态系统生产力与消费者资源利用产生潜在影响，尤其在北方湖泊的浅水区域。 浮游植物（Phytoplankton）：叶绿素a（chla）的测定采用过滤100mL水样的方法，使用分光荧光计（Perkin Elmer LS-55，美国马萨诸塞州）进行检测，激发波长设定为433nm，发射波长设定为673nm。 周丛生物（periphyton）：定植于长60cm、宽10cm、厚0.75mm的塑料条上的周丛生物（排除顶端10cm区域附着的藻类），分别在三个采样日期测定其色素组分（叶绿素a（chla）、叶绿素c（chlc）、岩藻黄素（fucoxanthin））；每个采样日期仅收获当日首次投放的塑料条，此前已收获过的塑料条不再纳入检测。每个池塘设置2次或4次重复测量。