Food availability is a primary factor determining species distribution and success, especially for offshore benthic organisms that rely on sinking particles as their main food supply. Temporal changes in the quantity and quality of food sources, often linked to shifts in the prevailing hydrographic conditions, thus have important consequences for benthic community composition and ecosystem functioning. Here, we investigate variability in the biochemical composition of offshore benthic organisms and their food sources across different time-scales (3 weeks, 1 year, 2 years) at the Sub-Antarctic Prince Edward Islands (PEIs) using nitrogen and carbon stable isotope (SI; δ¹⁵N and δ¹³C, respectively) and fatty acid (FA) analyses. The δ¹⁵N of suspended particulate matter (SPM) did not show a consistent trend over time, probably because the primary driver of δ¹⁵N_SPM variability appears to be seasonality and we sampled at roughly the same time each year. In contrast, the δ¹³C_SPM increased with time, likely as a result of the changing proportion of macroalgal detritus relative to offshore phytoplankton biomass. The δ¹⁵N and δ¹³C of select trophic groups varied with time, but not necessarily in synchrony with the SPM, possibly due to differences in the SI turnover rates of the food sources versus the consumers. In contrast, the FA composition of most taxa did change over time, reflecting the shorter integration period for FA compared to SI. While taxa showed different FA patterns across the time-scales investigated, the dominant trend was one of decreasing food quality with time. Combined, the SI and FA results indicate that the response of the benthos to the factor Time is not straightforward. We conclude that the two techniques provide different yet complementary temporal information, with animal SI ratios reflecting the longer-term and FA composition the shorter-term response of the benthos to changing food availability. Our findings suggest that different species at the PEIs will respond differently to climate-driven changes in food quality and quantity, increasing the uncertainty facing this vulnerable ecosystem.

粮食供应是决定物种分布和成功的主要因素，特别是对于依靠下沉颗粒作为主要粮食供应的近海底栖生物而言。食物来源的数量和质量的时间变化通常与主要水文条件的变化有关，因此对底栖生物群落组成和生态系统功能产生重要影响。在这里，我们利用氮和碳稳定同位素（PEIs）研究了南极爱德华王子岛（PEIs）在不同时间范围（3周，1年，2年）上近海底栖生物及其食物来源的生化成分的变异性（ SI;δ ¹⁵ N和δ ¹³ C，分别地）和脂肪酸（FA）的分析。该δ ¹⁵悬浮颗粒物（SPM）N没有表现出随时间变化的趋势一致，可能是因为δ的主要驱动力¹⁵ ň _SPM的变化似乎是季节性和我们每年在大致相同的时间采样。与此相反，δ ¹³ C ^ _SPM随时间增加，可能是因为相对于离岸浮游植物生物质大型海藻碎屑的变化比例的结果。的δ ¹⁵ N和δ ¹³特定营养族的C随时间变化，但不一定与SPM同步，这可能是由于食物来源与消费者的SI周转率不同所致。相反，大多数分类单元的FA组成随时间变化，反映出FA的整合期比SI短。虽然在所调查的时间范围内，分类单元显示出不同的FA模式，但主要趋势是随着时间的推移食品质量下降。结合在一起，SI和FA结果表明，底栖动物对时间因子的响应不是简单的。我们得出的结论是，这两种技术提供了不同但又互补的时间信息，动物SI比率反映了长期的底栖动物和FA组成，对底栖动物对变化的食物供应量的短期响应。