Range expansion of the sea urchin Centrostephanus rodgersii leads to loss of taxonomic diversity in a kelp bed habitat, eastern Tasmania

The long spined sea urchin Centrostephanus rodgersii (Diadematidae) has recently undergone poleward range expansion to eastern Tasmania (southeast Australia). This species is associated with barrens habitat which has been grazed free of macroalgae, and therefore has potentially important consequences for reef structure and biodiversity.

This study used urchin removal experiments from barrens patches in eastern Tasmania to monitor the subsequent response of the macroalgae relative to unmanipulated barrens patches.

In removal patches, there was a rapid proliferation of canopy-forming macroalgae (Ecklonia radiata and Phyllospora comosa), and within 24 months the algae community structure had converged with that of nearby areas without urchins.

Faunal species richness was comparatively low in barrens habitat, with C. rodgersii grazing activity resulting in an estimated minimum net loss of approximately 150 taxa compared with intact macroalgal habitats.

长棘海胆（long spined sea urchin）Centrostephanus rodgersii（冠海胆科Diadematidae）近期向东南澳大利亚的塔斯马尼亚东部发生了向极分布扩张（poleward range expansion）。该物种与已被啃食殆尽、无大型藻类（macroalgae）的贫瘠栖息地（barrens habitat）相关联，因此可能对珊瑚礁结构（reef structure）及生物多样性（biodiversity）产生重要影响。

本研究通过在塔斯马尼亚东部的贫瘠斑块（barrens patches）开展海胆移除实验（urchin removal experiments），监测大型藻类相对于未处理贫瘠斑块（unmanipulated barrens patches）的后续响应。

在移除斑块中，冠层形成大型藻类（canopy-forming macroalgae）（辐射海带Ecklonia radiata和梳状叶藻Phyllospora comosa）迅速增殖（proliferation），且在24个月内，藻类群落结构（algae community structure）与附近无海胆区域的群落结构趋同（converged）。

动物物种丰富度（faunal species richness）在贫瘠栖息地相对较低，与完整大型藻类栖息地（intact macroalgal habitats）相比，罗氏中心海胆（C. rodgersii）的摄食活动（grazing activity）导致估计至少约150个类群（taxa）的净损失。