Species 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.克赖斯特彻奇港（Christchurch Harbour）地处多塞特郡东部，大致位于普尔港（Poole Harbour）与索伦特海峡（Solent）的中点。其形成于冰川后海侵时期，当时埃文河（River Avon）与斯托尔河（River Stour）下游的汇合河谷被海水淹没。该港全长约2.5千米，面积不超过2平方千米。 港内基质以潮间带（intertidal）细质泥砂为主，南岸、西岸及西北岸分布有小片盐沼。埃文河与斯托尔河的汇流形成一条浅潮汐水道，穿过沉积滩，但在入海前会被狭窄的入口“海峡水道（The Run）”向北偏转。这种偏转及港入口的淤积，源于海岸侵蚀与沿岸漂沙形成的双沙嘴地貌。 在河流流量较高的时段（尤其是冬季），淡水会在港内淤积，同时限制海水的盐分输入。因此，港内大部分区域为咸淡水水域，但盐度降低的程度随潮汐和季节变化。 该港景观优美，腹地无工业化活动，是南海岸重要的休闲水上运动中心。河口内几乎无商业捕捞活动，仅有人捕捞鲑鱼、海鳟与鳗鱼。其中埃文河以其鲑鱼洄游景观和休闲粗钓闻名。 该区域游客众多，尤以来自附近伯恩茅斯（Bournemouth）和绍斯伯恩（Southbourne）的度假者为甚，港南侧的亨吉斯特伯里角（Hengistbury Head）等景点承受着巨大的游览压力。该港同时具有鸟类学研究价值，因为穿越英吉利海峡的候鸟倾向于将该区域作为登陆点与扩散中转站。 斯坦皮特沼泽（Stanpit Marsh）是本地自然保护区，克赖斯特彻奇港的大部分区域已被列为具特殊科学价值地点（Site of Special Scientific Interest，SSSI）。过往的科学研究主要聚焦于该区域的地质与地貌学特征，以及多样的滨海植物生境。 本次于1987年6月开展的调查，旨在收集克赖斯特彻奇港潮下带（subtidal）与潮间带现有生境及群落多样性的相关数据。调查共走访32个采样点，其中23个为潮间带位点，9个为潮下带位点。在每个潮间带位点，现场记录了植物、底上动物（epifauna）及显眼物种的丰度；采集沉积物岩芯并通过0.5毫米孔径的筛网过筛，以获取定量的底内动物（infaunal）数据；潮下带区域则结合潜水与疏浚作业进行采样。 港内生境多样性较低，整体以沉积型生境为主，或受沉积作用影响显著。受盐度普遍偏低的水环境以及缺乏稳定基底的影响，底上动物与藻类的多样性同样较低。港外孤立的铁质岩礁露头区域的动植物多样性最高。大型底栖动物（macroinfauna）的整体多样性也较低，特征为有限类群的种群密度极高。 在“海峡水道（The Run）”区段内，动物群落从以笋锥沙蚕（Lanice conchilega）为优势种的滨海型群落，逐渐转变为以斯氏旋鳃虫（Streblospio shrubsolii）、光滑盲蝟钩虾（Corophium volutator）与杂色疣吻沙蚕（Hediste diversicolor）为优势种的河口上部或咸淡水型群落。该群落类型横跨港内主要开阔水域，向西延伸至威克汉姆斯（Wick Hams），之后河口物种逐渐消失，被淡水或咸淡水物种取代。 该区域的科学与自然保护重要性已通过标准评估准则进行了评定。这些准则被应用于所有已识别的生境或群落类型，并将其初步划分为本地、区域、国家或国际级别的重要性等级。本次调查未发现具有特殊科学价值的物种，但其他研究者在咸淡水盐沼生境中记录的3种无脊椎动物的保护重要性已通过类似方式完成评估：分别为两种介形类（ostracods）——默里美星介（Callistocythere murrayi Whittaker）与斯蒂芬德西星介（Cytherios stephanidesi Klie），以及一种端足类（amphipod）——迟钝角钩虾（Gammarus insensibilis Stock）。由于这些类群及其生境尚未得到广泛或深入的研究，其分布仍有待阐明，因此上述物种的等级评定仍为暂定。 尽管该港主要被归类为河口，但它同时具备典型的泻湖属性。随着英国泻湖生境的研究现状逐步明晰，对这一独特滨海入口的评估或需进行调整。