Habitat point records from 1981 James south Cornwall sublittoral survey

The principal aim of this survey was to record community and habitat information from the rocky sublittoral along the coast of Cornwall from Land's End to Nare Head (10 km north-east of Falmouth). The survey team comprised both biologically experienced and biologically 'naive' divers, education in marine life identification and survey techniques being a secondary aim of the expedition. Some sites in the survey area had been briefly examined during a joint UCS/NCC expedition in 1980 and descriptions of these are contained in the report of that expedition (Dipper, 1981). The south Cornish coast consists of a sequence of headlands seperating wide, shallow bays. The hard granite bedrock comprising much of the coast produces cliffs around the headlands, which drop more gently sublittorally, true vertical faces rarely being recorded over a large depth range although the massive, blocked structure of the granite makes smaller cliffs a feature of many sites. Outcrops of bedrock are commonly interspersed with areas of coarse shell sand, also present in the bottom of gullies. The large sweeping bays are predominantly sediment-bottomed with outcrops of either granite or of a finely bedded, slate-like rock with strata at a shallow angle to the horizontal (the sediment of these bays sometimes being finer). The 50 m depth contour generally runs to within 1.5 km of the major headlands, but does not penetrate the bays. Several of the many rock pinnacles present in the area were dived. Some of these rise to within 10 m of the surface and may drop to depths of over 40 m. With the prevailing wind south-westerly, from the open sea, south and west facing shores are very exposed or exposed to wave action, and north and east facing shores sheltered, few sites being very sheltered from wave action. Main tidal streams flow east-west, running principally between headlands with maximum current speeds of over 2.3 knots. Only subsidiary currents enter the bays. Additional water currents from river flow occur over the St Mawes' bank site. 19 sites were surveyed during the week, with as wide a range of exposure to tidal streams and wave action as was possible along the coast. Species lists were made, samples collected and habitats recorded. Profiles and brief descriptions of the seabed and dominant species at each site are provided in the report. The major sublittoral zone communities encountered are described, and comments on major species and groups of species noted. Some 'south-western' species are poorly represented in the results, particularly some of the conspicuous Anthozoa, which was surprising. Axinellid sponges were also scarce, as were the two Polymastia species and the bryozoan fauna was impoverished (similar to that of the west coast of Ireland). The area noted to be of greatest nature conservation interest was the Fal Estuary, particularly the St Mawes' Bank living maerl bed, which has been declared a Voluntary Marine Reserve since the survey took place. Carn Base and Porth Curno provide good examples of extremely exposed sublittoral habitats and the report suggests that further survey work should take place to the east of the Fal where reduced wave action and turbidity may give rise to some interesting communities. Two of the richest sites visited, were the Outer Bizzies and the Whelps and a wide range of habitats in a fairly small area was present at the Manacles. This site is much visited by sports divers (probably for the scenary and numerous wrecks) and the report suggests that this could be a potential base for a diver education site (e.g. a marine nature trail), a diving school being located nearby. The generally exposed nature of most of the survey area to waves and tidal streams and the precipitous coast both ensures that the communities present are not particularly suceptible to disturbance and that access to the area is limited. The main threat from divers is thought to be collection of marine curios such as Eunicella and Echinus (it is unknown whether this was the cause of low numbers of these species at many sites). The report also concludes that traditional fishing methods do not appear to pose a threat to the rocky littoral. Records currently considered sensitive have been removed from this dataset.

本调查的主要目的是记录康沃尔海岸从兰兹恩德至纳尔海角（法尔茅斯东北10公里）岩石浅海的社区和栖息地信息。调查队伍由生物经验丰富的潜水员和生物学‘新手’潜水员组成，海洋生物识别和调查技术的教育是探险的次要目标。调查区域的一些地点在1980年联合UCS/NCC探险中被简短考察，这些地点的描述包含在该探险报告（迪普尔，1981年）中。南康沃尔海岸由一系列的海岬构成，分隔出宽阔而浅的海湾。构成海岸大部分的坚硬花岗岩床岩在海岬周围形成悬崖，而悬崖下则逐渐倾斜至海底，真正的垂直面在较大深度范围内很少记录到，尽管花岗岩的巨大、阻塞结构使得许多地点存在较小的悬崖。基岩的露出部分通常与粗沙壳沙地区域相间，这些地区也存在于沟壑的底部。宽阔的海湾主要是沉积物底质，有花岗岩或细层状、类似板岩的岩石露出部分，其地层与水平面呈浅角度（这些海湾的沉积物有时较细）。50米深度等高线通常在主要海岬附近1.5公里范围内，但并未穿透海湾。该区域许多岩石尖塔中的一些已被潜水考察。其中一些上升至距水面10米处，可能下降至40米以上的深度。由于主导风向为来自开阔海的西南风，因此朝南和西的海岸非常暴露或暴露于波浪作用之下，而朝北和东的海岸则较为隐蔽，很少有地点能够免受波浪作用的影响。主要潮流流向东西，主要在头地之间流动，最大流速超过2.3节。只有支流进入海湾。来自河流的水流电流在圣马维斯银行地点发生。在那一周内调查了19个地点，尽可能在海岸线上广泛地暴露于潮流和波浪作用之下。制作了物种清单，收集了样本，并记录了栖息地。报告提供了每个地点的海底和主要物种的剖面和简要描述。描述了遇到的主要浅海区域群落，并对主要物种和物种群进行了注释。一些‘西南部’物种在结果中表现不佳，尤其是某些显眼的珊瑚动物，这令人惊讶。轴形海绵也很稀少，两种多柱海绵物种也是如此，而苔藓动物群也相对贫乏（与爱尔兰西海岸相似）。被认为具有最大自然保护价值的地区是法尔河河口，特别是圣马维斯银行的活石床，自调查以来已被宣布为自愿性海洋保护区。卡尔恩基地和波恩科诺提供了极端暴露的浅海栖息地的良好例子，报告建议在法尔河东部进行进一步调查，那里的波浪作用和浑浊度可能产生一些有趣的群落。访问的两个最丰富的地点是外比齐斯和威尔普斯，在相当小的区域内存在广泛的栖息地。该地点是运动潜水员常去的地点（可能是由于景色和众多沉船），报告建议这可以成为潜水教育场所的潜在基地（例如，海洋自然小径），附近已设有潜水学校。调查区域大多数地区普遍暴露于波浪和潮流以及陡峭的海岸，这既确保了现有的群落不太容易受到干扰，也限制了该地区的访问。潜水员的主要威胁被认为是收集海洋古玩，如环节动物门海葵和海胆（尚不清楚这是否是许多地点这些物种数量较少的原因）。报告还得出结论，传统的捕鱼方法似乎不会对岩石浅海构成威胁。目前被认为是敏感的记录已被从该数据集中删除。