ABSTRACT: Biological invasions can dramatically affect the ecology of invaded regions, and globally have resulted in economic damages that total billions of dollars annually. In recent years, an invasive alga, Sargassum horneri, has become established and spread along the coast of southern California (USA). Using field observations and a field experiment, we explored how this non-native alga influences the structure of fish assemblages on temperate reefs in southern California where S. horneri has become prolific. Fish and algal assemblages were quantified along transects on rocky reefs at depths of 3 and 6 m at 6-8 study sites spanning 5 km on 4 occasions over 1.5 yr. Spatiotemporal variation in the fish assemblage was not strongly correlated with the abundance of invasive S. horneri over this period, although it became less variable as native giant kelp Macrocystis pyrifera disappeared from the study sites due to a warm-water event, during which the invasive S. horneri became more dominant. An experiment removing a total of 4.25 t of S. horneri from 6 × 6 m plots (n = 14) revealed that the invasive alga did not affect fish abundance, species richness, species diversity (H’), or multivariate assemblage structure over a 5 mo period. Overall, we found little evidence of negative effects of S. horneri on fishes even though it drastically changed the underwater landscape. Nevertheless, we advise cautionary management actions to limit the movement of this invasive alga because its effects on other community members, such as other algal species, may be detrimental, and longer-term effects on fishes might develop.

中文翻译：

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入侵藻类Sargassum horneri对温带礁鱼组合的影响有限

摘要：生物入侵会极大地影响被入侵地区的生态，并且在全球范围内造成的经济损失每年总计数十亿美元。近年来，一种入侵藻类海藻（Sargassum horneri）已经建立并在加利福尼亚南部海岸（美国）传播。通过野外观察和野外实验，我们探索了这种非原生藻类如何影响南加州桑尼河（S. horneri）多产的温带礁石上鱼群的结构。在1.5年内，在6-8个研究地点（跨越5公里）上，分别在3和6 m深度的岩礁上，对鱼和藻类组合进行了定量分析，深度分别为3和6 m。鱼群中的时空变化与侵袭性的丰度没有强烈关系S. horneri在此期间，虽然它变得不那么变量作为原生巨藻Macrocystis pyrifera从研究地点因温水事件，在此期间，侵入消失S. horneri变得更占优势。一项从6×6 m样地（n = 14）去除总计4.25 t霍恩沙门氏菌的实验表明，入侵藻类不影响鱼的丰度，物种丰富度，物种多样性（H'）或整个海域的多类集合结构。 5个月。总体而言，我们几乎没有发现霍尼沙门氏菌负面影响的证据。即使彻底改变了水下景观 但是，我们建议采取谨慎的管理措施来限制这种侵入性藻类的活动，因为它对其他社区成员（例如其他藻类）的影响可能是有害的，并且可能对鱼类产生长期影响。