Habitat point records from 1985 OPRU HRE Milford Haven and the Cleddau survey

Milford Haven and the estuary of the Rivers Cleddau (the Daucleddau) are situated at the south-west tip of Wales. The area under tidal influence includes over 110 km of coastline but with an entrance only 3.5 km wide. There is a main channel with some large bays near the entrance and muddy creeks (pills) at intervals along the length of the inlet. Geologically, the area is predominantly of Old Red Sandstone but with areas of Millstone Grit and Limestone. The inlet is a ria and the steep-sided valley east of the Cleddau Bridge continues into the subtidal. This results in the presence of extensive rocky shores which continue underwater as steep rock or boulder slopes in places. Mud flats are present in the wider parts of Milford Haven and in the pills. Sandy beaches are present near to the entrance. The seabed is predominantly of muddy sediments but with much shell and coarse material mixed-in Milford Haven whilst, in the narrow Daucleddau, cobbles and shell gravel are generally present. Depths in excess of 10 m below chart datum are present throughout Milford Haven and the Daucleddau as far east as Beggars Reach (almost 20 km from the entrance) and in excess of 5 m to Black Tar (a further 4km). Freshwater input to the system is about 7.5 x 10 to the power of five m3 per day, the average amounting to 0.4% of the tidal prism at neap tides and thus causing appreciable dilution only in the narrower landward parts of the inlet. The area has been an important centre for shipping and light industry for hundreds of years and currently provides sheltered berths for oil tankers at three refineries. Recent developments have included the cultivation of oysters and rearing of fin fish within the sheltered waters of the Daucleddua. Milford Haven and the Daucleddau have been the subject of many studies particularly since about 1960. These have provided descriptions of rocky intertidal and sediment subtidal communities in particular as well as records of effects of oil industry development and oil pollution in Milford Haven. Several studies have also been undertaken of the hydrography of the inlet. The present survey and a previous NCC commisioned survey in 1978/79 aimed to collect further information on the marine habitats and communities present in Milford Haven and the Duncleddau, particularly in areas and habitats inadequately sampled previously. The habitats present and abundance of conspicuous species were recorded on the shore and in the subtidal by diving. A dredge was used on one day to collect samples for analysis of species living in sediments. Fourteen intertidal, 17 subtidal diving and seven dredge sites were surveyed and sampled in 1985. Description of habitats and communities was based on these data together with the results of rocky shore and sediment shore surveys undertaken during work funded by the Institute of Petroleum, and with the results of surveys during 1978/79 of 37 sublittoral sites during the south-west Britain Sublittoral Survey. Ten intertidal and seven subtidal habitat/community types are described and the distribution of habitats and communities discussed in relation to hydrography and other factors. The area is considered to include a wide range of habitats and communities, several of which are of scientific and/or nature conservation interest. Particular attention is drawn to the muddy-sand beaches near the entrance to the Haven, the sheltered or very sheltered bedrock shores in Milford Haven and the Duncleddau, creek muds and mud banks, subtidal bedrock and stable boulders in the Haven, artificial substrata in the Haven, wave sheltered/tidal streams exposed hard substrata in the eastern Haven and Duncleddau, areas of Maerl near Stack Rock and areas of muddy sand colonised by Zostera marina. Fourteen algae and three animal species are noted as of particular scientific interest in their presence in Milford Haven and the Duncleddau. Records currently considered sensitive have been removed from this dataset.

米尔福德海港及其克莱德河（达乌克莱德河）河口位于威尔士西南角。受潮汐影响的区域涵盖了超过110公里的海岸线，但入口处仅有3.5公里宽。该区域拥有主航道，入口附近分布着一些大型海湾，而在入海口沿线每隔一段距离便可见到泥泞的溪流（沙洲）。地质上，该区域主要由古老的红砂岩构成，夹杂着石英砂岩和石灰岩区域。该入海口为里亚海岸，克莱德桥东部的陡峭山谷延伸至潮下带。这导致在潮间带存在广阔的岩石海岸，这些岩石海岸在局部地区以陡峭的岩石或砾石坡形式延伸至水下。米尔福德海港更宽阔的部分及沙洲上存在泥滩。靠近入口处有沙滩。海底主要由泥质沉积物构成，但在米尔福德海港中夹杂着大量贝壳和粗颗粒物质，而在狭窄的达乌克莱德河中，则以砾石和贝壳砾石为主。米尔福德海港和达乌克莱德河的海拔低于10米的海域遍布整个区域，直至贝格勒奇（从入口处向东约20公里）以及至布莱克塔尔（再往东4公里）超过5米深。该系统每天约有7.5 x 10^5立方米的新鲜淡水流入，平均约占小潮期间潮量体积的0.4%，因此在入海口较狭窄的内陆部分引起明显的稀释。该区域数百年来一直是航运和轻工业的重要中心，目前为三个炼油厂的油轮提供避风锚地。近期的发展包括在达乌克莱德乌亚的掩护水域中养殖牡蛎和饲养鲑鱼。米尔福德海港和达乌克莱德河自1960年以来一直是众多研究的对象，特别是对岩石潮间带和沉积潮下带群落以及米尔福德海港油工业发展及其污染影响的记录。还进行了对入海口水文地理的几项研究。本次调查和1978/79年NCC委托的前一次调查旨在收集关于米尔福德海港和达乌克莱德河中海洋栖息地和群落的更多信息，特别是之前采样不足的区域和栖息地。通过潜水在岸边和潮下带记录了现有栖息地和显眼物种的丰富度。在一天中使用疏浚设备收集样品，以分析生活在沉积物中的物种。1985年对14个潮间带、17个潮下带潜水点和7个疏浚点进行了调查和采样。栖息地和群落的描述基于这些数据，以及由石油研究所资助的岩石海岸和沉积海岸调查的结果，以及1978/79年西南不列颠海底调查期间对37个海底地点的调查结果。描述了10种潮间带和7种潮下带栖息地/群落类型，并讨论了栖息地和群落与水文地理以及其他因素的分布关系。该区域被认为包含了广泛的栖息地和群落，其中一些具有科学和/或自然保护价值。特别关注海港入口附近的泥沙海滩、米尔福德海港和达乌克莱德乌亚的掩护或非常掩护的基岩海岸、溪流泥质和泥岸、海港中的潮下基岩和稳定的砾石、海港中的人工底质、东部海港和达乌克莱德乌亚的避风/潮流暴露的硬质底质、斯塔克岩附近的梅尔草区域以及被海藻草覆盖的泥滩。有14种藻类和3种动物物种因其存在于米尔福德海港和达乌克莱德河而被视为具有特别的科学兴趣。目前认为敏感的记录已从本数据集中删除。