Abstract：
Seaweeds are important components of coastal benthic ecosystems along the Western Antarctic Peninsula (WAP), providing refuge, food, and habitat for numerous associated species. Despite their crucial role, the WAP is among the regions most affected by global climate change, potentially impacting the ecology and physiology of seaweeds. Elevated atmospheric CO2 concentrations have led to increased dissolved inorganic carbon (Ci) with consequent declines in oceanic pH and alterations in seawater carbonate chemistry, known as Ocean Acidification (OA). Seaweeds possess diverse strategies for Ci uptake, including CO2 concentrating mechanisms (CCMs), which may distinctly respond to changes in Ci concentrations. Conversely, some seaweeds do not operate CCMs (non-CCM species) and rely solely on CO2. Nevertheless, our understanding of the status and functionality of Ci uptake strategies in Antarctic seaweeds remains limited. Here, we investigated the Ci uptake strategies of seaweeds along a depth gradient in the WAP. Carbon isotope signatures (δ13C) and pH drift assays were used as indicators of the presence or absence of CCMs. Our results reveal variability in CCM occurrence among algal phyla and depths ranging from 0 to 20 m. However, this response was species specific. Among red seaweeds, the majority relied solely on CO2 as an exogenous Ci source, with a high percentage of non-CCM species. Green seaweeds exhibited depth-dependent variations in CCM status, with the proportion of non-CCM species increasing at greater depths. Conversely, brown seaweeds exhibited a higher prevalence of CCM species, even in deep waters, indicating the use of CO2 and HCO3-. Our results are similar to those observed in temperate and tropical regions, indicating that the potential impacts of OA on Antarctic seaweeds will be species specific. Additionally, OA may potentially increase the abundance of non-CCM species relative to those with CCMs.
摘要：
海藻是南极半岛西部沿海底栖生态系统的重要组成部分,提供庇护,食物,和许多相关物种的栖息地。尽管发挥了关键作用,WAP是受全球气候变化影响最大的地区之一，可能影响海藻的生态和生理。大气CO2浓度升高导致溶解的无机碳（Ci）增加，从而导致海洋pH值下降和海水碳酸盐化学发生变化。被称为海洋酸化(OA)。海藻具有不同的Ci吸收策略，包括CO2浓缩机制(CCM)，这可能对Ci浓度的变化有明显的反应。相反，一些海藻不操作CCM（非CCM物种），只依赖CO2。然而，我们对南极海藻中Ci吸收策略的地位和功能的理解仍然有限。这里,我们在WAP中沿着深度梯度研究了海藻的Ci吸收策略。碳同位素特征（δ13C）和pH漂移测定被用作存在或不存在CCMs的指标。我们的结果揭示了藻类之间CCM发生的变异性，深度范围为0至20m。但是，这种反应是物种特异性的。在红海藻中，大多数人完全依赖二氧化碳作为外源Ci源，非CCM物种的比例很高。绿色海藻在CCM状态下表现出深度依赖性变化，非CCM物种的比例在更大的深度增加。相反，棕色海藻表现出更高的CCM物种流行率，即使在深水区,指示CO2和HCO3-的使用。我们的结果与在温带和热带地区观察到的结果相似，表明OA对南极海藻的潜在影响将是物种特异性的。此外,相对于具有CCM的那些,OA可能潜在地增加非CCM物种的丰度。
