Seasonal variation in parasite infection patterns of marine fish species from the Northern Wadden Sea in relation to interannual temperature fluctuations

Marine environmental conditions are naturally changing throughout the year, affecting life cycles of hosts aswell as parasites. In particular,water temperature is positively correlatedwith the development ofmany parasites and pathogenic bacteria, increasing the risk of infection and diseases during summer. Interannual temperature fluctuations are likely to alter host?parasite interactions, which may result in profound impacts on sensitive ecosystems.
In this context we investigated the parasite and bacterial Vibrionaceae communities of four common small fish species (three-spined stickleback Gasterosteus aculeatus, Atlantic herring Clupea harengus, European sprat Sprattus sprattus and lesser sand eel Ammodytes tobianus) in the Northern Wadden Sea over a period of two years. Overall, we found significantly increased relative diversities of infectious species at higher temperature differentials. On the taxon-specific level some macroparasite species (trematodes, nematodes) showed a shift in infection peaks that followed the water temperatures of preceding months, whereas other parasite groups showed no effects of temperature differentials on infection parameters.
Our results show that even subtle changes in seasonal temperatures may shift and modify the phenology of parasites as well as opportunistic pathogens that can have far reaching consequences for sensitive ecosystems.

海洋环境条件常年处于自然变化之中，会对宿主与寄生虫的生命周期产生影响。具体而言，水温与多种寄生虫及致病菌的生长发育呈正相关，提升了夏季的感染与病害风险。年际温度波动或可改变宿主-寄生虫互作关系，进而对敏感生态系统造成深远影响。
在此研究背景下，我们于两年周期内对北瓦登海（Northern Wadden Sea）四种常见小型鱼类——三刺鱼（Gasterosteus aculeatus）、大西洋鲱（Clupea harengus）、欧洲西鲱（Sprattus sprattus）及小沙鳗（Ammodytes tobianus）的寄生虫群落与弧菌科（Vibrionaceae）细菌群落展开了调查。整体而言，我们发现在更大的温度差值下，感染性物种的相对丰富度显著提升。在类群特异性层面，部分大型寄生虫（吸虫（Trematoda）、线虫（Nematoda））的感染峰值出现时间随前几月水温变化发生偏移，而其他寄生虫类群的感染参数则未受温度差值的显著影响。
本研究结果表明，即便季节性气温出现细微变化，也可能改变寄生虫与机会致病菌的物候特征，进而对敏感生态系统造成波及范围极广的影响。