Species point records from 1977 SWBSS Lundy sublittoral survey

The present survey was carried out in order to describe the range and extent of the sublittoral habitats present around Lundy. The survey was also intended to test methods for quick survey and recording. The survey was carried out by a team of six university divers. Survey stations were located at depth intervals of 5 m mostly along Ordnance Survey Grid Line positions from 0 to 40 m. Check lists were used to record the habitats present and the main rock cover organisms. Descriptive surveys were carried out by swim lines, drift dives and with a towed sledge. Sediment samples were collected at some sites. The sites surveyed were distributed all around Lundy and extended to 1 km offshore. 206 stations were surveyed and descriptive surveys carried out at 13 locations. Supplementary information was obtained from 58 locations described by other workers. A wide variety of habitats were present around Lundy. Off the west coast there was a gradual slope of bedrock to a depth of about 35 - 40 m, 1 km offshore, followed by a sand or gravel plain. In pockets between the rocks small boulders, stones, gravel and mud were present. Along most of the south coast there was a gradual rock slope extending to up to 1 km offshore. However, extensive areas of sand were present in some places and, off the south-east of Lundy, the seabed was of broken slates. Sand and gravel was present as pockets amongst the rocks, but mud was recorded at only one station as 'minor'. The north coast was generally similar to the south coast but off Seals Rock, rock surfaces dropped very steeply to about 30 m. Off much of the east coast, a bedrock and boulder slope extended to about 9 m, was followed by a band of mud covered sediment several hundred metres wide and continued offshore as a plain of muddy gravel. Sand was present in the Landing Bay and offshore on the south part of the east coast. Steeply sloping rock surfaces were present at the Knoll Pins and at Gannets Rock. In many areas, rock surfaces were very broken with pinnacles and canyons present. A dense forest of Laminaria hyperborea was present to a depth of about 7 m around most of Lundy but only to about 5 m on parts of the east coast. The kelp forest was followed by a kelp park amongst dense foliaceous algae which extended to about 10 m. Around most of Lundy, the stable rock substrates below the zone of algal domination were characterised by dense bryozoa/hydrozoa populations with a wide variety of sponges and anthozoans present. Off the south-east corner in depths below 20 m, beds of brittle stars were present. The mud covered sediments off the east coast were characterised by burrows of Goneplax rhomboides and Cepola rubescens whilst the muddy gravel areas were characterised by sparse populations of Pecten maximus. The distribution of substrates around Lundy clearly reflects the predominant conditions of water movement. Thus, the extensive areas of rock present off the west, north and south coasts are kept mainly clear of sediment by strong wave action and tidal streams. The sheltered east coast is a deposition area. The extent of kelp and foliaceous algae around Lundy is accounted for largely by the turbidity of the water but also by the presence of silt on rocks and by grazing pressure on the east coast. The dense cover of bryozoa and hydrozoa around most of the island on rock is accounted for by the favourable conditions of water movement which brings food and maintains rock clear of silt. The location of sites provided a good basis for mapping and included all of the main habitats. However, the distance between depth stations was often considerable on gently sloping seabed and supplementary stations were required to map the limits of some features. Drift dives and the towed sledge provided a considerable amount of useful information. In future surveys of extensive areas of flat seabed, remote methods of observation might provide a better basis for mapping than the use of diving. Records currently considered sensitive have been removed from this dataset.

本次调查旨在描述围绕兰迪岛存在的海底栖息地的范围和广度。调查亦旨在测试快速调查和记录的方法。此次调查由一支由六名大学潜水员组成的团队执行。调查站点位于从0至40米的深度间隔，主要沿军械调查网格线位置布置。利用清单记录了现有栖息地和主要岩石覆盖生物。通过游泳线、漂流潜水和拖曳滑橇等方式进行了描述性调查。在一些地点采集了沉积物样本。调查地点遍布兰迪岛周围，并向海延伸至1公里。共调查了206个站点，并在13个地点进行了描述性调查。从其他工作者描述的58个地点获得了补充信息。兰迪岛周围存在多样的栖息地。在西海岸，海底基岩逐渐倾斜至约35至40米的深度，离岸1公里后，接着是一个沙或砾石平原。岩石之间的凹槽中存在小圆石、石头、砾石和泥土。在南海岸的大部分地区，岩石斜坡逐渐延伸至约1公里外。然而，在某些地方存在广阔的沙滩，而在兰迪岛东南部，海底由破碎的板岩组成。岩石之间存在沙和砾石的凹槽，但在只有一个站点记录到‘少量’的泥。北海岸总体上与南海岸相似，但在海豹岩附近，岩石表面陡峭地下降至约30米。在东海岸的大部分地区，基岩和圆石斜坡延伸至约9米，随后是一个数百米宽的泥覆盖沉积物带，并继续向海延伸为一个泥砾平原。在着陆湾和东海岸南部的海上存在沙子。在诺尔针和海燕岩处存在陡峭倾斜的岩石表面。在许多地区，岩石表面非常破碎，存在尖塔和峡谷。在兰迪岛的大部分地区，至约7米的深度存在密集的北极膜藻森林，但在东海岸的部分地区，深度仅为约5米。在膜藻森林之后，是密集的叶状藻类之间的膜藻公园，延伸至约10米。在兰迪岛的大部分地区，藻类统治区域以下的稳定岩石底质以密集的苔藓动物/水螅动物种群为特征，同时存在多种海绵动物和珊瑚动物。在东南角20米以下的深度，存在脆星虫的床。在东海岸的泥覆盖沉积物中，存在Goneplax rhomboides和Cepola rubescens的洞穴，而在泥砾区域，存在Pecten maximus的稀疏种群。兰迪岛周围底质的分布明显反映了水流的主导条件。因此，在西、北和南海岸存在的广阔岩石区域，主要通过强烈的波浪作用和潮流保持沉积物的主要清洁。受保护的东海岸是一个沉积区。兰迪岛周围海藻和叶状藻类的范围主要归因于水浑浊度，但也归因于岩石上的泥沙和东海岸的放牧压力。兰迪岛周围岩石上的苔藓动物和水螅动物的密集覆盖归因于有利于水流的有利条件，这种水流带来了食物并保持岩石免受泥沙的覆盖。提供的站点位置为绘制地图提供了良好的基础，包括所有主要栖息地。然而，在平缓的海底斜坡上，深度站之间的距离往往相当大，需要补充站点来绘制某些特征的极限。漂流潜水和拖曳滑橇提供了大量有用的信息。在未来对广阔平坦海底区域的调查中，远程观察方法可能比潜水提供更好的绘图基础。目前被认为是敏感的记录已被从本数据集中删除。