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Green turtle (Chelonia mydas) grazing plot formation creates structural changes in a multi-species Great Barrier Reef seagrass meadow
Marine Environmental Research ( IF 3.3 ) Pub Date : 2020-10-10 , DOI: 10.1016/j.marenvres.2020.105183
Abigail L. Scott , Paul H. York , Michael A. Rasheed

The Great Barrier Reef (GBR) contains extensive seagrass meadows with abundant and diverse herbivore populations. Typically, meadows in the region are multi-species and dominated by fast growing opportunistic seagrass species. However, we know little about how herbivores modify these types of seagrass meadows by grazing. We conducted the first megaherbivore exclusion study in the GBR at Green Island (Queensland) to understand how green turtle grazing structures these multi-species tropical seagrass meadows. After excluding green turtles for three months, we found that grazing only impacted seagrasses at one site, where green turtles created a grazing plot by actively feeding on both above and below ground seagrass structures, a rare observation for the species. Within this grazing plot at the end of the experiment, the un-caged control treatments open to grazing had a 60% reduction in both above and below ground biomass, and shoot height was reduced by 75%, but there was no impact of grazing on the seagrass species mix. Our study shows that grazing plot formation by green turtles occurs in GBR fast growing seagrass communities and reduces both above and below ground seagrass biomass, this behaviour may be targeting elevated leaf nutrients, or nutritional content of rhizomes. This study is the first documented case of grazing plot formation by green turtles in the GBR and suggests that grazing pressure has a major influence on seagrass meadow structure.



中文翻译:

绿海龟(Chelonia mydas)放牧地块的形成在多物种大堡礁海草草甸上造成结构变化

大堡礁(GBR)拥有广阔的海草草甸,草食动物种群丰富多样。通常,该地区的草甸是多物种的,并以快速生长的机会性海草物种为主导。但是,我们对草食动物如何通过放牧改变这些类型的海草草甸知之甚少。我们在绿岛(昆士兰州)的GBR中进行了首次大型食草动物排斥研究,以了解绿海龟放牧如何构造这些多物种热带海草草甸。在将绿海龟排除了三个月之后,我们发现放牧仅对一个地点的海草产生影响,那里的绿海龟通过主动进食地面海草结构的上方和下方创建了一个放牧地,这是对该物种的罕见观察。在实验结束时,在该放牧区中,可以放牧的未笼养对照处理的地面生物量和地下生物量均降低了60%,枝条高度降低了75%,但放牧对海草物种组成没有影响。我们的研究表明,绿海龟形成的放牧地块发生在GBR快速生长的海草群落中,并降低了海藻地上和地下的生物量,这种行为可能以提高叶片养分或根茎的营养含量为目标。这项研究是GBR中绿海龟形成的第一个有记录的放牧案例,表明放牧压力对海草草甸结构有重要影响。我们的研究表明,绿海龟形成的放牧地块发生在GBR快速生长的海草群落中,并降低了海藻地上和地下的生物量,这种行为可能以提高叶片养分或根茎的营养含量为目标。这项研究是GBR中绿海龟形成的第一个有记录的放牧案例,表明放牧压力对海草草甸结构有重要影响。我们的研究表明,绿海龟形成的放牧地块发生在GBR快速生长的海草群落中,并降低了海藻地上和地下的生物量,这种行为可能以提高叶片养分或根茎的营养含量为目标。这项研究是GBR中绿海龟形成的第一个有记录的放牧案例,表明放牧压力对海草草甸结构有重要影响。

更新日期:2020-10-13
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