Recent (post-1930) changes in the extent of subtidal seagrass (Zostera muelleri) beds of the eastern Bay of Islands, New Zealand

The surface areas of 12 subtidal seagrass Zostera muelleri beds at the islands and adjacent mainland shores of the eastern Bay of Islands (35° 12′ S, 174° 10′ E), New Zealand were estimated from aerial images. It appears that little subtidal seagrass existed until after the early-1950s, so significant beds here may be a relatively recent biome. Possible explanations for recent emergence of subtidal seagrass include that debilitating periods of turbid water and pulses of sedimentation associated with the land clearances of the late 1800s had worked through the marine ecosystem. An overall peak in seagrass-cover in the 1960s to 1980s was followed by declines in several beds in the 1990s to 2000s, with recovery since. The temporal presence of seagrass was well-correlated among the three mainland beds, and moderately well among the south-facing beds on the islands, consistent with mechanisms driving seagrass establishment and persistence operating at reasonably broad scales.

本数据集通过航空影像估算了新西兰群岛湾东部（35°12′S，174°10′E）的岛屿及邻近大陆沿岸的12处潮下带穆氏大叶藻（Zostera muelleri）床的表面积。研究显示，直至20世纪50年代早期以前，该区域几乎不存在潮下带海草，因此此处的大规模海草床或许是相对较新的生物群落。关于潮下带海草近期出现的潜在解释包括：19世纪末土地清理活动引发的长期浑浊水体胁迫期与泥沙沉积脉冲，已逐步作用于该区域的海洋生态系统。20世纪60年代至80年代，海草覆盖率达到整体峰值；随后在90年代至21世纪初，多处海草床出现退化，此后海草床逐步恢复。三处大陆沿岸海草床的海草时序分布呈现显著相关，岛屿上的南向海草床则呈现中等程度相关，这与调控海草定植与存续的机制在较大空间尺度上共同运作的结论相符。