Habitat point records from 1982 Dipper Wash sublittoral diving/dredging survey

This report notes the importance in the Wash of the sublittoral faunal populations, which may be a source of recruitment to the intertidal areas, for nature conservation and for fisheries. Although some information is available on the sublittoral of the Wash from remote sampling, very little diving has been done in the area due to low visibilities and strong tides. Although most of the area consists of mobile soft sediments, indications of some type of hard substratum are given by the masses of bryozoa and hydroids regularly washed up on the beaches. The aims of this preliminary survey were therefore to establish the feasibility of using diving to carry out a survey in this area, to collect information on the sublittoral, particularly in the Lynn Well area where 'rocky' outcrops were suspected and to make contacts with other organisations and individuals interested in the sublittoral of the Wash. The survey was carried out during a period of neap tides from a trawler owned by the Eastern Sea Fisheries Joint Committee. Two dives and three dredges were made. Descriptions of dive and dredge sites are provided, and species identified listed. No evidence of hard substrata was found, the sediments apparently consisting of muds and sands with a considerable amout of shell and pebble debris. The epifauna in the deeper areas dredged in Lynn Well was found to be fairly rich, with abundant hydroid material, Flustra foliacea and worm tubes attached to stones and shells on the sea bed. The infauna was also thought to be fairly rich, but only the top few inches of sediment could be sampled by dredge. In the Roaring Middle area a harder substratum may be present since little sediment was brought to the surface, and Modiolus beds are thought to occur here. Diving in the Wash is not a very effective method of survey due to the constraints of slack water and low visibility. However, it does provide a better indication of the composition and spatial arrangement of the communities and also allows collection of small organisms and other fragile material; information which may be lost from dredged collections. The report suggests therefore that diving would be a useful tool for backing up remote sampling methods in areas where interesting hauls have come to the surface.本报告指出，沃什湾（Wash）的潮下带（sublittoral）动物群对于自然保护与渔业具有重要价值——该类群可作为潮间带（intertidal）区域的种群补充来源。尽管已有通过远程采样获取的沃什湾潮下带相关数据，但由于该区域能见度低下、潮汐强劲，水下潜水调查开展极少。尽管该区域大部分为移动性软沉积底质，但海滩上频繁冲刷聚集的大量苔藓虫（bryozoa）与水螅虫（hydroids），暗示了此处存在某种硬质底质（substratum）。因此，本次初步调查的目标为：验证在该区域开展潜水调查的可行性；收集沃什湾潮下带相关数据，重点针对疑似存在"岩质"露头的林恩井（Lynn Well）区域；并与其他关注沃什湾潮下带生态的组织及个人建立联系。本次调查于小潮（neap tides）时段开展，依托东海洋渔业联合委员会（Eastern Sea Fisheries Joint Committee）所属的拖网渔船完成。本次调查共开展2次潜水作业与3次底拖采样（dredge）。文中附潜水及底拖采样点位的详细描述，并列出已鉴定的物种名录。本次调查未发现硬质底质存在的证据，沉积物主要由泥沙与砂质组成，并混杂有大量贝壳及卵石碎屑。林恩井区域深水底拖采样获取的底上动物（epifauna）群落多样性较为丰富，包含大量水螅虫类群、膜孔苔虫（Flustra foliacea）以及附着于海床石块与贝壳上的蠕虫栖管。底内动物（infauna）群落的多样性同样被认为较为丰富，但底拖采样仅能获取表层数英寸的沉积物样品。在咆哮中水道（Roaring Middle）区域，由于采样时仅获取了极少量沉积物，推测此处可能存在硬质底质，且被认为存在偏顶蛤（Modiolus）床。受限于平潮（slack water）窗口期与低能见度，在沃什湾开展潜水调查并非高效的调查手段。但潜水调查能够更清晰地反映群落组成与空间分布格局，还可采集小型生物及其他易碎样品——这类信息往往在底拖采样中会丢失。因此，本报告建议，在已有远程采样获取到优质样品的区域，潜水调查可作为辅助远程采样的有效工具。