Snapshot assessments of species, which live for a number of years, are often misleading if they are conducted at an inappropriately short temporal scale. Densities of the trochid gastropods Steromphala umbilicalis (da Costa, 1778) and S. cineraria (Linnaeus, 1758) fluctuated widely between 1996 and 2014 at ten rocky-shore sites within Lough Hyne, southwest Ireland. Between 2014 and 2019, the abundance of S. cineraria decreased to levels not seen in the previous two decades. This significant reduction was possibly in response to extreme dissolved oxygen fluctuations related to eutrophication of the semi-enclosed lough. Steromphala umbilicalis showed low density in 2018 and 2019, but this was within the limits of interannual fluctuations. The Lusitanian trochid Phorcus lineatus (da Costa, 1778) was first recorded by us in the lough in the early 2000s, just as it was establishing a flourishing population with densities of c. 6 snails/0.25 m². Although this native trochid survived the cold winters of 2009–2012, the population suffered high adult mortality and little recruitment. Between 2013 and 2019, the population increased and the population density stabilized. The increase in P. lineatus reflects its position high on the shore, where air temperatures have risen over the last two decades. It may, therefore, be a sentinel species to detect the effects of climate change. By contrast, the decrease in S. cineraria was related to its shallow subtidal habitat where hypoxia and superoxia have recently become marked in the lough. This trochid, therefore, offers potential as an indicator of eutrophication-associated stress. These temporal variations in trochid species emphasize the need for longer term assessments when estimating the importance of any one species to the ecosystem.

中文翻译：

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爱尔兰海湖中梭鱼种群的长期变化

如果对物种的快照评估已经存在多年，那么如果它们在不适当的短时间尺度上进行，往往会产生误导。1996年至2014年之间，爱尔兰西南部洛夫海恩（Lough Hyne）内十个岩岸点的旋足性腹足纲动物Steromphala umbilicalis（da Costa，1778）和S. cineraria（Linnaeus，1758）的密度波动很大。在2014年至2019年之间，瓜叶葡萄球菌的丰度下降到了过去二十年未见的水平。这种显着降低可能是由于与半封闭式湖泊富营养化有关的极端溶解氧波动。百里香在2018年和2019年显示出较低的密度，但这在年际波动的范围内。Lusitanian trochid Phorcus lineatus（da Costa，1778）最早是在2000年代初期由我们记录在该湖中的，当时它正以c的密度建立一个繁华的种群。6张蜗牛/0.25 m ²。尽管这种原生苗条虫在2009-2012年的寒冷冬季中幸免于难，但该人群的成年死亡率很高，招募人数很少。2013年至2019年，人口增加，人口密度稳定。P. lineatus的增加反映了它在海岸上的高位，在过去的20年中，那里的气温一直在上升。因此，它可能是检测气候变化影响的前哨物种。相比之下，瓜叶葡萄球菌的减少与其潮下浅生境有关，在该生境中低氧和高氧血症最近在湖中变得很明显。因此，该trochd具有潜在的富营养化相关压力的指标。旋毛虫物种的这些时间变化强调了在评估任何一种物种对生态系统的重要性时需要进行长期评估的必要性。