Habitat point records from 1987 OPRU HRE Christchurch Harbour survey

Christchurch Harbour is situated in east Dorset, approximately mid-way between Poole Harbour and the Solent. It was formed during the post glacial marine transgression which drowned the combined lower river valley of the Rivers Avon and Stour. It has a length of approximately 2.5km and an area of not more than 2km2. The harbour consist mainly of intertidal fine muddy sand, with small areas of salt marsh around its southern, western and north western shores. The combined river flow of the Avon and Stour occupies a shallow tide channel cutting through the sediment flats, but is deflected northward through a very constricted entrance, The Run, before reaching the sea. This deflection, and occlusion of the harbour entrance, is caused by a double spit feature resulting from coastal erosion and longshore drift. With high river flow rates, especially in winter, fresh water can become ponded within the harbour, restricting saline inputs from the sea at the same time. Consequently, most of the harbour is brackish but the degree of salinity reduction varies with tide and the season. THe harbour is attractive scenically, with no industrialised hinterland, and is an important centre on the south coast for recreational water sports. There is little commercial fishing within the estuary apart from netting for salmon, sea trout and eels. The River Avon in particular is noted both for its salmon run and for its coarse fishing. The area receives a lot of visitors, especially holiday makers from nearby Bournemouth and Southbourne, and attractions such as Hengistbury Head to the south of the harbour are under considerable pressure. The harbour is also of ornithological interest, because migrant birds crossing the Channel appear to favour the area as both a landfall and a dispersal point. Stanpit Marsh is a Local Nature Reserve, and most of Christchurch Harbour has been notified as an SSSI. Scientific interest in the past has been centred on the region's geology and physiography, together with its diversity of botanically interesting maritime habitats. The present survey, carried out in June 1987, aimed to collect information on the variety of habitats and communities present subtidally and intertidally in Christchurch Harbour. A total of 32 sites were visited, of which 23 were intertidal and 9 subtidal. At each intertidal site the abundance of flora, epifauna and conspicuous species were recorded in situ. Sediment cores were taken and sieved over a 0.5 mm mesh to obtain quantitative infaunal data. Subtidal areas were sampled using a combination of diving and dredging. Within the harbour, habitat diversity was low and predominantly sedimentary in nature, or sediment influenced. Epifaunal and algal diversity was also low due to the generally reduced salinity regime, and a lack of stable substrata. The most diverse fauna and flora found was on the isolated ironstone boulder outcrops outside the harbour. The macroinfauna was also of low diversity generally and was characterised by very dense populations of a restricted number of species. Within the length of The Run, the fauna changed from a coastal type dominated by Lanice conchilega, to an upper estuarine or brackish type dominated by Streblospio shrubsolii, Corophium volutator and Hediste diversicolor. This fauna type extended across the main open part of the harbour as far west as Wick Hams, after which estuarine species dropped out to be replaced by fresh-water or brackish forms. The scientific and nature conservation importance of the area has been assessed using standard criteria. These have been applied to each of the habitats or community types identified which have then been provisionally graded as being of Local, Regional, National or International importance. No species of particular scientific interest were found during this survey work, but the conservation importance of three invertebrate species recorded by other workers from brackish saltmarsh habitats has been assessed in a similar manner. These were two species of ostracods, Callistocythere murrayi Whittaker and Cytherios stephanidesi Klie, and an amphipod, Gammarus insensibilis Stock. Their gradings are provisional because these groups, and their habitats, have not received wide or intensive study and their distributions still require elucidation. Although the harbour has been assessed mainly as an estuary, it also possesses distinctly lagoonal properties, and the assessment of this interesting coastal inlet may require adjustment as the status of Britains's lagoonal habitats becomes better known.

基督城港位于多塞特郡东部，大致位于波尔特港与索伦特港之间。该港的形成源于冰川期后海平面上升，淹没了艾冯河与斯托尔河的汇合处。其长度约为2.5公里，面积不超过2平方公里。港内主要由潮间带细腻的淤泥沙组成，南部、西部及西北部沿岸有少量盐沼地。艾冯河与斯托尔河的河水汇流穿过沉积平原，形成浅水航道，但需通过极为狭窄的入口——‘跑道’，方能汇入大海。这一转向及港口入口的封闭，是由海岸侵蚀和沿岸漂移形成的双重沙嘴所造成。在河流流量较大，尤其是冬季时，淡水会在港口内积聚，从而限制海水盐分的输入。因此，该港大部分水域为半咸水，但盐度降低的程度随潮汐和季节而变化。该港风景宜人，周边无工业化区域，是南海岸重要的休闲水上运动中心。除捕获鲑鱼、海鳟和鳗鱼外，河口内商业捕鱼活动很少。特别是艾冯河，以其鲑鱼洄游和底层钓鱼而闻名。该地区吸引了众多游客，尤其是来自附近的博恩茅斯和索恩伯恩的度假者，港口南部的亨吉斯特伯里角等景点承受着巨大的压力。该港还具有鸟类学上的重要意义，因为横跨英吉利海峡的候鸟似乎偏好该地区作为登陆点和扩散点。斯坦皮特沼泽是地方自然保护区，基督城港的大部分区域已被列为特殊科学兴趣区域（SSSI）。过去，该区域的科学兴趣主要集中在地质和地形学，以及其生物多样性的海洋栖息地。本次调查于1987年6月进行，旨在收集关于基督城港水下及潮间带各种栖息地和群落的信息。共访问了32个地点，其中23个为潮间带，9个为水下区域。在每个潮间带地点，均就地记录了植物、地栖动物和显眼物种的丰富度。采集了沉积物芯，并使用0.5毫米的筛网进行筛选，以获取地栖动物的数量数据。水下区域通过潜水与疏浚相结合的方式进行采样。在港内，栖息地多样性较低，且以沉积性为主，或受沉积物影响。由于一般盐度较低，以及缺乏稳定的底质，地栖动物和藻类的多样性也较低。在港外孤立的铁质巨石露头处，发现了最为丰富的动植物种类。宏观地栖动物多样性也普遍较低，特征为数量极为密集的少数物种。在‘跑道’的长度范围内，动物群从以兰尼丝·康尼莉加为优势种的海岸型转变为以斯特雷布洛斯皮奥·什鲁布斯奥利、科洛菲乌姆·卷曲和赫迪斯特·多色为优势种的上河口或半咸水型。这种动物群类型一直延伸到港口主开阔区域最西端的威克哈姆，之后河口物种消失，被淡水或半咸水形态所取代。该区域的科学和自然保护重要性已使用标准准则进行评估。这些准则已应用于每个已识别的栖息地或群落类型，并临时分级为地方、区域、国家或国际重要性。本次调查工作中未发现具有特别科学兴趣的物种，但已类似地评估了其他工作者在半咸水盐沼地栖息地记录的三个无脊椎动物的保护重要性。这些物种包括两种端足类，即穆雷氏美星虫（Callistocythere murrayi Whittaker）和斯蒂芬尼德斯氏美星虫（Cytherios stephanidesi Klie），以及一种桡足类，即无感觉挠足类（Gammarus insensibilis Stock）。由于这些群体及其栖息地尚未得到广泛或深入研究，其分布仍需阐明，因此这些等级仅为临时。尽管该港主要被评估为河口，但它也具有明显的潟湖特性，因此随着英国潟湖栖息地状况的进一步了解，对该有趣海岸水道的评估可能需要调整。