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首页> 外文期刊>Marine biology >The Role Of The Amphipod Gammarus Locusta As A Grazer On Macroalgae In Swedish Seagrass Meadows
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The Role Of The Amphipod Gammarus Locusta As A Grazer On Macroalgae In Swedish Seagrass Meadows

机译：在瑞典海草草甸的大型藻类中，两栖类γ蝗虫作为放牧者的作用

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Mesograzers are thought to play a critical role in seagrass beds by preventing overgrowth of ephemeral algae. On the Swedish west coast, eelgrass Zostera marina has decreased in recent decades as a result of eutrophication and increased growth of macroalgal mats (mainly filamentous Ulva spp. and Ectocarpales), with no indication of grazer control of the algae. The aim of this study was to investigate the ability of the amphipod Gammarus locusta to control algal blooms during nutrient-enriched and ambient conditions, using a combination of laboratory, field and model studies. Laboratory experiments demonstrated that juvenile and adult G. locusta could consume both Ulva spp. and Ectocarpales, but that consumption of Ulva spp. was significantly higher. Cannibalism was common in individual treatments involving multiple size-classes of G. locusta, but only large, male gammarids consumed smaller juveniles in the presence of Ulva spp. as an alternative food source. However, no negative effects of cannibalism were found on total grazing impact. A model using size-specific grazing rates and growth rates of G. locusta and of Ulva spp. suggests that approximately 62 young juvenile, or 27 adult G. locusta are needed per gram DW of Ulva spp. to control the algal growth during ambient nutrient conditions, and approximately 2.6 times as many gammarids during enhanced nutrient conditions. On the Swedish west coast, densities and mean sizes of G. locusta in eelgrass beds are below these critical values, suggesting that the gammarids will not be able to control the growth of the filamentous macroalgae. However, in the field cage experiment, immigration of juveniles and reproduction of encaged adult G. locusta resulted in unexpectedly high densities of G. locusta (> 4,000 individual m~(-2) ), and very low biomass of Ulva spp. in both ambient and nutrient-enriched treatments. Although the high numbers of juveniles in all cages precluded any significant treatment effects, this suggests that in the absent of predators, the population of G. locusta can grow significantly and control the biomass of Ulva spp. Furthermore, low grazing of Ectocarpales in the laboratory and high biomass of these filamentous brown algae in the field indicate a preference for the more palatable green algae Ulva spp. This study indicates that the high grazing capacity of G. locusta, in combination with high reproduction and growth rates, would allow the amphipod to play a key role in Z. marina ecosystems by controlling destructive blooms of filamentous green algae. However, high predation pressure appears to prevent large populations of G. locusta in eelgrass beds on the Swedish west coast today.
机译：据认为，中型放牧者通过防止短暂藻类的过度生长在海草床上起着至关重要的作用。在瑞典西海岸，近几十年来，由于富营养化和大型藻类垫（主要是丝状Ulva spp。和Ectocarpales）的生长增加，鳗草的带状疱疹（Zostera marina）有所减少，但没有迹象表明食草者控制了藻类。这项研究的目的是结合实验室，田间研究和模型研究，研究两栖类γ-齿蝗在营养丰富和环境条件下控制藻华的能力。实验室实验表明，幼虫和成虫G. locusta可以同时食用Ulva spp。和角果皮，但食用Ulva spp。明显更高。同类相食在涉及多种大小分类的G. locusta的个体治疗中很常见，但是只有大的雄性γ-角类动物在存在Ulva spp的情况下才食用较小的幼体。作为替代食物来源。但是，没有发现同类相食对总的放牧影响有负面影响。一个模型，使用大小特定的放牧率和齿状短吻线虫和Ulva spp的生长速率。提示每克Dl Ulva spp需要大约62个年轻的少年或27个成年的G. locusta。在环境营养条件下控制藻类的生长，在增强营养条件下控制约2.6倍的γ射线。在瑞典西海岸，鳗草床中蝗的密度和平均大小均低于这些临界值，这表明γ-内酰胺不能控制丝状大型藻类的生长。然而，在田间笼实验中，少年的移栖和成虫被诱捕的成年G. locusta的密度出乎意料地高（> 4,000个个体m〜（-2）），而Ulva spp的生物量却非常低。在环境和营养丰富的治疗中都可以使用。尽管所有网箱中的幼鱼数量都很高，但没有任何明显的治疗效果，这表明在没有捕食者的情况下，蝗群可以显着生长并控制Ulva spp的生物量。此外，实验室中的角果皮草的低放牧和田间这些丝状褐藻的高生物量表明偏爱更可口的绿藻Ulva spp。这项研究表明，蝗草的高放牧能力，再加上高繁殖和高生长速率，将通过控制丝状绿藻的破坏性繁殖，使两足纲动物在滨海假单胞菌生态系统中发挥关键作用。然而，高捕食压力似乎阻止了当今瑞典西海岸鳗草床中的大量蝗虫。

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