1983 Alconbury Environmental Consultants, The Fleet, Dorset, Quadrat survey of Zostera and Ruppia

Survey “Holmes, N.T.H. 1983. The distribution of Zostera and Ruppia in the Fleet. Report to Nature Conservancy Council, Alconbury Environmental Consultants. A copy of the report is held at English Nature (Dorset Team). DK from report:- 1st of 3 surveys by author, covers Fleet (Dorset). Previous marine plant surveys carried out on Fleet shown few mapped exact species distribution. This survey collect data to form baseline, assess stability populations of Eelgrass species - Zostera noltii and Zostera angustifolia, and Tasselweeds species - Ruppia cirrhosa (entered onto database as R.spiralis) and Ruppia maritima. Other species included algaes: Fucus, Enteromorpha, Cladophora and Ulva. Method:- 1st two weeks August 1983. Survey area:- whole of Fleet, west and east ends less rigorously than main body of Fleet. In Fleet, and below the Narrows no aquatic angiosperms encountered, author took 20 quasi-quadrats on foot along north shore. Samples taken from quadrats (about 100m2), each quadrat (radius = 5.5 meters approx.) 2.5 meters loop of anchor rope over pole thrust into mud in centre of quadrat, distance from pole to end of boat = 5.5 meters. Using oars or punting pole, boat rotated around pole several times, about 100m2 inspected. Random site selection (A-J), determined by access (by foot / row boat). Appendix 1: quadrat position. Data collection on relative abundance of individual aquatic angiosperms species within each surveyed quadrats. Semi - quantitatively estimating area covered by individual species within quadrat, and percentage expressed of total area investigated. In practical terms obviously prone to considerable recorder error, but reduced by recording within 100m quadrats (simplifies percentage estimates regarded each 1m2 area as 1% of total). Report details on plant identification, information on depth, substrate and associated algae approx. 50 algal and mollusc species - samples collected for others; re Fleet Study Group. Presence of Sargassum noted, details passed to Dr Farnham, Portsmouth University. Results:- raw data pertaining to both substrate and flora within each 100m2 quadrats (Appendix 2). Table provides information on relative proportions of organic mud, inorganic mud, sand, gravel, pebbles and cobbles within each quadrat, and total vegetational cover. Algal data given for firmly attached fucoids, Lamprothamnion and free floating Enteromorphas, Cladophoraleans and Ulvas. Percentage surface area of quadrats covered by Zostera and Ruppia species given. Table summarises date and time quadrats sampled. Results show Z.angustifolia, Z. noltii and R. cirrhosa common in Fleet, and R. maritima less frequent and locally distributed, no other angiosperms recorded. Fig.1 importance of these species in different quadrats varied considerably, Fig.2 details distribution and extent for 4 angiosperms and Lamprothamnion, Fig.3, (Table 10) summarises relative importance of species in sites (A-H) of Fleet. Within discussion and recommendations, community succession throughout Fleet detailed, 1983 survey clearly illustrates zonation of individual species along length of Fleet, and results confirm previous findings although many new features of floras and fauna emerged. Reference given to each 4 species of angiosperms, L. papulosum and algae recorded. Survey data based on visual estimates of cover provided by individual species in 100m2 quadrats, at best survey data regarded valuable in evaluating relative abundance’s of various species in different areas of Fleet, and baseline for future changes. Author specifies that data not to be used, however crudely in quantitative evaluations of standingcrop. Tidal cover estimates (raw data tables) prone to additional problems due to unattached algal. Data to be regarded as accurate and representative record of distribution and relative importance of different aquatic flowering plants in Fleet (August 1983). Substrate records very subjective evaluations of organic / inorganic matter. Generally, clear black organic substrates dominant upperhalf of Fleet, grey inorganic muds predominate northern shore. Threats to Zostera and Ruppia discussed. Authors recommends future investigation within 3 years, raw data requires statistical treatment to evaluate significant correlations between species with depth, substrate, salinity and position. More control needed on discharges into Fleet and, Swannary (Abbotsbury) analyse swan population changes to assist nutrient budget investigations.本调查源自Holmes, N.T.H.于1983年完成的《菲利特潟湖（Fleet）内鳗草属（Zostera）与川蔓藻属（Ruppia）的分布情况》报告，该报告提交给自然保护委员会（Nature Conservancy Council），由Alconbury环境咨询公司编制。报告副本现存于英国自然保护协会（English Nature）多塞特分部。 报告数据说明：本次调查为作者开展的3项同类调查中的第一项，研究区域为多塞特郡的菲利特潟湖。此前针对该潟湖开展的海洋植物调查仅对物种分布进行了粗略制图，未精确标注具体物种的分布范围。本次调查旨在构建该区域海洋植物的本底基准数据，评估两种鳗草属物种——矮大叶藻（Zostera noltii）与狭叶鳗草（Zostera angustifolia），以及两种川蔓藻属物种——旋花川蔓藻（Ruppia cirrhosa，数据库中记录为R. spiralis）和海生川蔓藻（Ruppia maritima）的种群稳定性。此外，调查还记录了以下藻类：褐藻属（Fucus）、浒苔属（Enteromorpha）、刚毛藻属（Cladophora）以及石莼属（Ulva）。 调查方法：本次调查于1983年8月的前两周开展，覆盖整个菲利特潟湖，其中潟湖东西两端的调查强度低于潟湖主体区域。在潟湖内部及海峡（Narrows）下游区域未发现水生被子植物，作者沿北滩步行布设了20个准样方。 样方采样流程如下：以中心锚定的竹竿为圆心，将长2.5米的锚绳绕杆布设，锚绳末端至竹竿的距离约为5.5米，对应样方面积约100平方米。通过船桨或撑杆驱动小船绕竹竿旋转一周，完成约100平方米区域的勘查。样方位点（编号A-J）采用随机选取方式，选取依据为步行或划艇可达性。附录1记录了所有样方的位置。 数据采集方面，调查人员对每个样方内的水生被子植物物种的相对丰度进行记录：通过半定量方式估算各物种在样方内的覆盖面积，并以占样方总调查面积的百分比表示。实际操作中该方法易受调查者主观误差影响，但通过将每个100平方米样方拆分为100个1平方米单元，简化了百分比估算过程，一定程度上降低了误差。 报告中详细记载了植物鉴定方法、调查水深、底质类型以及伴生藻类等信息，共记录了约50种藻类和软体动物物种，其余物种样本已提交给菲利特潟湖研究小组。调查中发现了马尾藻属（Sargassum）的分布，相关细节已转交至朴茨茅斯大学的Farnham博士。 调查结果：所有100平方米样方的底质与植物群落原始数据详见附录2。附表记录了每个样方内有机泥、无机泥、沙子、砾石、卵石和鹅卵石的相对占比，以及总植被覆盖度。藻类数据涵盖了固着褐藻、串珠藻属（Lamprothamnion）、自由漂浮的浒苔属、刚毛藻目（Cladophoraleans）以及石莼属物种。附表同时给出了鳗草属与川蔓藻属物种在样方内的表面积占比，并汇总了各样方的采样日期与时间。 结果显示，狭叶鳗草、矮大叶藻以及旋花川蔓藻在菲利特潟湖内分布广泛，而海生川蔓藻的出现频率较低且呈局部分布，未记录到其他水生被子植物物种。图1表明，不同样方内各目标物种的重要性存在显著差异；图2详细展示了4种被子植物与串珠藻属的分布范围与覆盖规模；图3（即表10）汇总了潟湖内A-H位点各物种的相对重要性。 讨论与建议：报告对整个菲利特潟湖内的植物群落演替情况进行了详细阐述，1983年的本次调查清晰地展示了各物种沿潟湖纵向的分布分带现象，研究结果验证了此前的调查结论，同时也发现了诸多新的植物与动物群落特征。报告中对4种被子植物、串珠藻（Lamprothamnion papulosum）以及各类藻类的记录均附有参考文献。 本次调查数据基于100平方米样方内各物种覆盖度的目视估算，总体而言，该数据可用于评估菲利特潟湖不同区域内各物种的相对丰度，同时可作为监测未来群落变化的本底基准。作者特别说明，该数据不可用于任何形式的现存量（standingcrop）定量评估，即便采用粗略估算方式也不可行。 由于存在未固着藻类的干扰，基于原始数据表格的潮汐覆盖度估算存在额外误差。总体而言，本次调查数据可视为1983年8月菲利特潟湖内水生被子植物分布与相对重要性的准确且具有代表性的记录。底质记录属于对有机/无机物质占比的主观评估，通常情况下，潟湖上游区域以黑色有机底质为主，北滩则以灰色无机泥为主。 报告讨论了鳗草属与川蔓藻属物种面临的生存威胁。作者建议在未来3年内开展后续调查，原始数据需进行统计分析，以评估各物种与水深、底质、盐度以及区位之间的显著相关性。此外，需加强对排入菲利特潟湖及斯旺纳里（Abbotsbury，阿伯茨伯里）区域的污染物排放管控，并通过分析天鹅种群数量变化辅助开展营养盐收支调查。