Species point records from 1990 UMBSM Loch Etive survey

Loch Etive is a typical fjord, carved into grantie and metamorphic rocks by glaciers from the Rannoch Moor area. The steeply walled, deep upper basin is followed by a series of shallower basins and sills amongst low-lying lava hills towards the entrance. The ice left a bedrock bar across the outer sill which now forms the Falls of Lora, a spectacular tidal race. Rivers draining the glacier built an extensive plain of outwash gravel which partially dammed the loch entrance and formed the north bank of the loch near Connel. Two salmon farms and one trout farm have been established in the lower loch but the majority of mariculture is concentrated on mussel farming in the upper basin. Loch Etive is an Marine Consultation Area and there are 3 Sites of Special Scientific Interest adjoining the shoreline. Several marine biological studies have been carried out in the loch by workers based at the Dunstaffnage Marine Laboratory. Of most releveance is a series of papers by J. Gage and his co-workers based on surveys of the sediment infauna. Littoral studies were carried out by Powell et al. (1977). Forty-three sites were surveyed between the 15th and 22nd September 1990. These included 29 diving surveys, 3 anchor dredge samples and 11 littoral surveys; 25 habitat/community types have been described. Loch Etive is perhaps unique amongst Scottish sealochs for the extensive brackish conditions which influence the distritubtion of species. Freshwater draining into the loch from a vast catchment creates salinity gradients where salinities decrease towards the head and increase in deeper water. The surface layers are permanently brackish with salinities that vary considerably, but in deeper water, over approximately 15 m, conditions become more stable and salinities are higher. Consequently there is a noticeable changeover between shallow communities with brackish-tolerant species, such as Mytilus edulis, Carcinus meanas and Dendrodoa grossularia, which dominate the first few metres to more fully marine species in deeper water. However, certain stenohaline species, for example, the echinoderms Echinus esculentus and Psammechiuns miliaris were not found in the loch. Shallow substrata near the head of the loch were almost completely devoid of conspicuous flora and fauna. From a comparison made between this and an earlier visit it is clear that there is some turnover in species in the brackish layers controlled by fluctuations in the salinity (D.W.Connor and C.M.Howson, pers. com.). Brackish-tolerant and mainly opportunistic species colonize the shallow substrata when salinity levels increase and conditions stabilize. The deeper communities are affected to a lesser extent by brackish conditions. Large numbers of Neocrania anomala were found on deep bedrock along with Sarcodictyon roseum and Psolus sp.. The sediment communities in the deeper areas were reminiscent of those found in other fjordic sealochs, although diversity was somewhat reduced in all areas. There were prime examples of brackish tide-swept communities in the Falls of Lora and Kilmaronag Narrows. Much of the hard substrata in this area supported dense Laminaria hyperborea which was replaced in deeper water by a thick turf of Halichondria bowerbanki, Sertularia argentea and Alcyonidium diaphanum and there were also patches of bedrock with dense Flustra foliacea. Balanus crenatus was particularly abundant on the more scoured rocky substrata which included parts of the Bonawe Narrows. Seven habitat/community types and 11 species have been provisionally assessed to be of Local, Regional or National importance. Records currently considered sensitive have been removed from this dataset.

洛赫蒂夫湾乃一典型的峡湾，其由来自朗诺莫尔地区冰川侵蚀的花岗岩和变质岩切割而成。其陡峭的壁面和深邃的上部盆地之后，依次是数个较浅的盆地和位于低矮火山丘陵之间的门槛。冰川留下的基岩坝横跨外门槛，如今形成了洛拉瀑布，一处壮观的潮汐激流。融化的冰川河流在洛赫蒂夫湾入口处形成了广阔的冲积砾石平原，部分阻塞了湖口，并在康奈尔附近形成了湖的北岸。在较低的湖中已建立了两个鲑鱼养殖场和一个鳟鱼养殖场，但大部分水产养殖集中在上游盆地的贻贝养殖。洛赫蒂夫湾是海洋咨询区，其海岸线附近有三个具有特殊科学意义的地点。在邓斯塔芬海洋实验室的科研人员进行了多项海洋生物研究。其中，J. 盖奇及其同事基于对沉积物底栖动物群调查的一系列论文最为相关。Powell 等人（1977年）进行了海滩研究。1990年9月15日至22日之间，共调查了43个地点，包括29次潜水调查、3次锚拖样品和11次海滩调查；描述了25种栖息地/群落类型。洛赫蒂夫湾在苏格兰的类似海湾中可能独一无二，其广泛的半咸水条件影响了物种的分布。从广阔的集水区流入湖中的淡水创造了盐度梯度，盐度在湖头附近逐渐降低，而在较深的水中逐渐升高。表层水永久性半咸，盐度变化较大，但在大约15米深的水中，条件更加稳定，盐度更高。因此，在浅水群落中，如耐半咸水的紫贻贝、欧洲招潮蟹和网状海胆等物种占据前几米，而在较深的水中，则有更多完全海洋性的物种。然而，某些狭盐性物种，例如可食用的海胆和米粒状海胆，在湖中并未发现。湖头附近的浅层底质几乎完全缺乏显眼的植物和动物。通过与此前的访问进行比较，可以明显看出，在受盐度波动控制的半咸水层中，物种有所更迭（D.W.Connor 和 C.M.Howson，个人通信）。耐半咸水和主要机会主义的物种在盐度水平升高和条件稳定时殖民浅层底质。较深的水生群落受半咸水条件的影响较小。在深水基岩上发现了大量新克尼亚异常种，以及玫瑰状海藻和 Psolus sp.。较深区域的沉积物群落与在其他峡湾型海湾中发现的群落相似，尽管所有区域的多样性都有所降低。洛拉瀑布和基尔马龙纳狭窄处的半咸水潮汐群落是典型的例子。该区域的许多硬质底质上生长着茂密的北极膜藻，而在较深的水中则被厚厚的海藻层所取代，包括鲍尔班克海葵、银色管海绵和透明软珊瑚。还有密集的 Flustra foliacea 床岩斑块。在较被冲刷的岩石底质上，尤其是波纳韦狭窄处，巴兰纽斯 crenatus 非常丰富。初步评估了7种栖息地/群落类型和11个物种具有地方、区域或国家重要性。目前被认为敏感的记录已被从本数据集中移除。