Counts and abundance of macrozoobenthic organisms settled in artificial soft sediment at Brandal, Kongsfjorden, Spitsbergen

In the Arctic the currently observed rising air temperature results in more frequent calving of icebergs. The latter are derived from tidewater glaciers. Arctic macrozoobenthic soft-sediment communities are considerably disturbed by direct hits and sediment reallocation caused by iceberg scouring. With the aim to describe the primary succession of macrozoobenthic communities following these events, scientific divers installed 28 terracotta containers in the soft-sediment off Brandal (Kongsfjorden, Svalbard, Norway) at 20 m water depth in 2002. The containers were filled with a bentonite-sand-mixture resembling the natural sediment. Samples were taken annually between 2003 and 2007. A shift from pioneering species (e.g. Cumacea: Lamprops fuscatus) towards more specialized taxa, as well as from surface-detritivores towards subsurface-detritivores was observed. This is typical for an ecological succession following the facilitation and inhibition succession model. Similarity between experimental and non-manipulated communities from 2003 was significantly highest after three years of succession. In the following years similarity decreased, probably due to elevated temperatures, which prevented the fjord-system from freezing. Some organisms numerically important in the non-manipulated community (e.g., the polychaete Dipolydora quadrilobata) did not colonies the substrate during the experiment. This suggests that the community had not fully matured within the first three years. Later, the settlement was probably impeded by consequences of warming temperatures. This demonstrates the long-lasting effects of severe disturbances on Arctic macrozoobenthic communities. Furthermore, environmental changes, such as rising temperatures coupled with enhanced food availability due to an increasing frequency of ice-free days per year, may have a stronger effect on succession than exposure time.

北极当前观测到的气温上升，导致冰山崩解事件愈发频繁。此类冰山源自潮汐冰川（tidewater glaciers）。北极大型底栖软沉积群落（macrozoobenthic soft-sediment communities）会因冰山刮擦引发的直接撞击与沉积物再分配，受到严重干扰。为描述此类事件后大型底栖群落的原生演替（primary succession）过程，科研潜水员于2002年在挪威斯瓦尔巴群岛康斯峡湾布伦达尔附近20米水深的软沉积环境中，布设了28个陶土容器。容器内填充了模拟自然沉积物的膨润土-砂混合物（bentonite-sand-mixture）。研究团队于2003年至2007年间每年采集样本。研究观察到群落结构发生两类转变：一是从先锋物种（如涟虫目（Cumacea）的Lamprops fuscatus）向特化类群演变，二是从表面食碎屑者向地下食碎屑者转变。这符合促进-抑制演替模型（facilitation and inhibition succession model）下的生态演替特征。演替三年后，2003年布设的实验群落与未受干扰群落的相似性达到峰值。后续年份中二者相似性逐渐下降，这可能是由于气温升高导致峡湾系统无法结冰所致。部分在未受干扰群落中数量占优的物种（如多毛类（polychaete）的Dipolydora quadrilobata）未能在实验期间定植于实验底物。这表明该群落在前三年内并未完全成熟。后续定居过程则可能因气温变暖带来的连锁效应而受阻。该研究证实了重度干扰对北极大型底栖软沉积群落的长期影响。此外，诸如气温上升叠加每年无冰日数增加导致的食物可获得性提升等环境变化，对演替的影响可能比扰动暴露时长更为显著。