Marine zooplankton are increasingly being affected by recent environmental changes, such as climate change, and respond with profound spatial relocations and shifts in phenology and physiology. In order to predict whether populations are able to persist or adapt to such new conditions, it is essential to understand the molecular basis of such adaptations, which ultimately get translated into these physiological responses. To explore variation in population gene expression across time and space, we investigated transcriptome-level profiles of the calanoid copepod Temora longicornis, that were collected at four different locations in the Belgian Part of the North Sea (BPNS) on three different time points (April, June, October) in 2018. RNA-seq analysis of field collected adults identified large seasonal differences in gene expression, mainly between spring-summer and autumn samples. The largest log-fold changes occurred in a set of genes encoding for ribosomal and myosin (heavy chain) transcripts. Enrichment analysis revealed a strong seasonal pattern in vitellogenin, cuticle and glycolytic gene expression as well. We also found a positive correlation between vitellogenin expression and densities of T. longicornis. No clear spatial variation in expression patterns was found in the BPNS. This study underlines the potential of field gene expression studies for biomonitoring purposes and the significance of considering seasonal variation in future studies.

海洋浮游动物正日益受到近期环境变化（例如气候变化）的影响，并以深刻的空间重新定位以及物候和生理学的变化做出响应。为了预测种群是否能够持久或适应这种新条件，必须了解这种适应的分子基础，最终将其转化为这些生理反应。为了探索跨时空的种群基因表达的变化，我们研究了cal足类pe足类天疱疮的转录组水平概况，是在2018年的三个不同时间点（4月，6月，10月）在北海比利时部分（BPNS）的四个不同地点收集的。对田间采集的成年人进行RNA序列分析发现基因表达存在较大的季节性差异，主要在春夏季和秋季样品之间。最大的对数倍变化发生在一组编码核糖体和肌球蛋白（重链）转录本的基因中。富集分析揭示了卵黄蛋白原，表皮和糖酵解基因表达方面的强烈季节性模式。我们还发现卵黄蛋白原表达与T. longicornis的密度之间呈正相关。在BPNS中未发现表达模式的明显空间差异。这项研究强调了用于生物监测目的的现场基因表达研究的潜力以及在未来研究中考虑季节变化的重要性。