The Loch Eil project: Planktonic pigments in sediments from Loch Eil and the firth of Lorne

Photosynthetic pigments and their derivatives were measured in sediments in the fjordic Loch Eil and the Firth of Lome, Scotland, between November 1975 and November 1976. After acetone extraction from the top 10 mm of sediment cores, pigments were crudely separated, by fluorescence change on acidification, into (chlorophyll a + chlorophyllide a) and phaeopigments. The greatest pigment concentrations (mean 73 μg · g sediment dry wt^?1) were found in the most reducing sediments which also had a high average proportion (23%) of chlorophyll. The least mean pigment concentration (23 μg · g^?1) and proportion of chlorophyll (17%) were found in the most oxidizing sediments in the Firth of Lorne where there was a clear seasonal cycle, with a peak in sediment pigment concentration and chlorophyll proportion in May and June, just after the planktonic spring increase. The Loch Eil stations showed a less clear or no seasonal cycle; the station most affected by organic input was the most variable from month to month. It was concluded that redox status was the most obvious control of sediment pigment content, whereas the effect of sedimentation of phytoplankton was complex.     

Long-term variation and regulation of internal phosphorus loading in Loch Leven

Long-term monitoring data (1968–2008) were used to investigate internal phosphorus (P) loading following external P loading reduction in shallow Loch Leven, Scotland. A whole-lake sediment P inventory (upper 3 cm of sediment; 2005) suggested a release-potential of 29.7 tonnes (t) from the release sensitive sediment P pools. 18.5 t was contained within shallow water sediments (<4.5 m water depth) with 7.6 t in deeper water sediments below the photic zone (>5 m water depth). The “observed” release (<5.1 t), estimated using a water column P mass balance approach (1989–2008), was <5.1 t, indicating the presence of regulating mechanisms. Observed P release declined between 1989 and 2008, with the exception of 2003–2006. Observed P release estimates were positively correlated with annual average water column P concentration after 1989, highlighting the role of internal loading in maintaining poor water quality conditions after management intervention. Multiple regression analysis suggested that internal loading was driven by the wave mixed depth in spring (positive driver), summer water temperature (positive driver) and spring water clarity transparency (negative driver). The potential importance of biological and physico-chemical feedback mechanisms in the regulation of benthic–pelagic coupling and water quality in Loch Leven are discussed.     

The Benthic Impacts of the Loch Linnhe Artificial Reef

Artificial reefs are man-made structures that are placed on the seabed to mimic natural reefs. The Loch Linnhe Artificial Reef will consist of up to 40 reef modules, when completed, each constructed using concrete blocks. As part of this complex, reef modules of approximately 200 tonnes were deployed in June 2001 and January 2002 and form the basis of this study. Sediment samples were taken adjacent to- and 5 m from the reef perimeters and characterised in terms of sediment oxygenation (redox), particle size, organic carbon (loss on ignition) and coarseness (material >1 mm and <5 mm). Changes in molluscs and ophiuroids (>1 mm) present in the sediment were linked to chemico-physical changes occurring as a consequence of the reef. Both reefs trapped macroalgal phytodetritus at the perimeters, which subsequently decomposed. This accumulated material isolated the seabed from the overlying water column and was associated with a decrease in sediment oxygenation that was linked to changes in community structure. LOI was significantly higher around one reef compared with 5 m from that reef. The reefs did not cause significant changes in the sediment texture (median particle size or coarseness) and neither LOI nor sedimentary texture changes were associated with community change.     

A comparative assessment of temporal variation in diet of powan, Coregonus lavaretus (L.), from Loch Lomond and Loch Eck, Scotland, U.K.

Stomach contents of powan caught throughout the year from Loch Lomond and Loch Eck were examined. Adult powan in Loch Lomond fed mainly on planktonic Cladocera, switching to benthic food during December-April. Bosmina coregoni was the principal planktonic food with Daphnia hyalina an important late summer and autumn prey. Loch Eck powan fed throughout the year on chironomid larvae and Pisidium spp. from the benthos and ingested large amounts of non-food material. Mean dry weights of food in stomachs were correlated with water temperature in Loch Lomond but not in Loch Eck and were higher in powan from Loch Eck over most of the year.     

Zooplankton in Loch Lomond: perspectives,predation and powan

Published and unpublished accounts of the zooplankton community of Loch Lomond are reviewed. Loch Lomond's zooplankton community is unique amongst those of Scotland's other large lochs. Holopedium gibberum appeared in Loch Lomond in the years between the studies of Slack & Hamilton in the 1950s and zooplankton surveys in the late 1970s.The annual cycles of Eudiaptomus gracilis, Cyclops strenuus abyssorum and Mesocyclops leuckarti are described for the mid basin of Loch Lomond. E. gracilis overwinter mainly as adult with variable egg production during their lifespan of 5–8 months. The cyclopoid copepods have variable life history characteristics. C. str. abyssorum produce a single generation per year, overwinter by means of resting eggs and a small population of planktonic adults, while M. leuckarti is present in the plankton throughout the year, but in low numbers during winter.Zooplankton populations in Loch Lomond are predated by the diverse fish community which includes a facultative planktivore in the powan, Coregonus lavaretus. Powan feed heavily on zooplankton from late spring until late autumn. Powan display selectivity in the prey species taken, in the size distribution and morph types taken within prey species. Zooplankton species, morphs and forms in Loch Lomond tend to reflect this predation.Zoology Department, University of St. AndrewsZoology Department, University of St. Andrews     

Geology of the Loch Lomond catchment

Loch Lomond is unusual in its geographical position and relationship to underlying geological structures. To the north-west of the Highland Boundary Fault the bedrock is composed mainly of the Dalradian Supergroup, a sequence of regionally metamorphosed Late Precambrian marine sediments. Immediately to the south-east of the Highland Boundary Fault the Highland Bonder Complex includes fragments and slices of ophiolitic origin and sediments with a range of Ordovician ages. The Dalradians may have originated in a remote location on the northern margin of Gondwanaland. To the south-east of the Highland Border the bedrock lies within the Midland Valley of Scotland and consists entirely of Upper Palaeozoic rocks of Devonian and Carboniferous age. The nature of the bedrock has an influence on the environment of Loch Lomond with respect to slope stabilities and water quality.     

Planktonic diatoms and silica in Loch Leven, Kinross, Scotland: a one month silica budget

Diatom populations and silica concentrations were monitored at frequent intervals in the shallow, eutrophic Loch Leven over a 27-day period (October 1972) and the influences of the inflows, outflow and the sediment were assessed. Changes in dissolved and particulate silica are accounted for by incorporating the results into a silica budget. During this period processes affecting silica within the loch were more important than those outside. The incorporation of diatom frustules into the sediments and the release of dissolved silica from the sediments appeared to be of particular importance. Evidence suggests that dissolution of the frustules of some planktonic diatom species was also important.     

The recent diatom history of Loch Leven, Kinross

Diatoms in the top metre of lake sediment have been studied for indications or recent changes in the environment of Loch Leven. The diatoms indicate a eutrophic, alkaline lake with Melosira italica ssp. subarctica, Tabellaria Flocculosa and Stephanodiscus astraea the dominant taxa at the base of the 1-m section. There is then an appeance of Melosira ambigua and Stephanodiscus hantzschii suggesting a richer environment. Post A.D. 1816 changes in taxa suggest possible correlation with the lowering of lake level in 1830 and the dominance of Diatoma elongatum, Cyclotella pseudostelligera, Stephanodiscus astraea var. minutula, S. tenuis, S. hantzschii, and Synedra rumpens and var. soctica in zone 4 agrees with present-day plankton records.     

A seasonal and ecological study of the phytoplankton of Loch Lomond

The seasonal succession of phytoplankton in Loch Lomond has been studied both quantitatively and from observations on net plankton. From a qualitative investigation of net phytoplankton Loch Lomond may be described as diatom-desmid in nature although from the quantitative studies the general domination of the population by diatoms becomes clear. During the vernal phytoplankton increase diatoms contributed more than 90% of the population throughout the loch. The bulk of the phytoplankton production occurred in the southern region, where the standing crop was considerably greater throughout the year than in other regions of the loch.Patterns of seasonal succession are described for all species which make an important contribution to the productivity of the loch and the observed successions related to measured physical and chemical changes in the water. Explanations are put forward to account for the absence of a second (autumnal) pulse ofMelosira in Loch Lomond. The appearance ofAnabaena circinalis is a possible indication of the changing trophic status of the southern region of the loch.     

Vegetation and land use in the Loch Lomond catchment

The Loch Lomond catchment lies across the boundary between the Lowlands and Highlands of Scotland, and its vegetation and land-use are influenced by the environmental contrasts which occur on either side of the Highland Boundary Fault. In the northern part of the catchment area elevations exceed 800 metres, and thus there is an altitudinal zonation component to vegetation and land-use patterns.The role of man has been profound in modifying natural vegetation, and recent land-utilisation is reviewed. Changing human and environmental circumstances have a significant effect on vegetation and land-use, and these factors are evaluated. Though natural and semi-natural vegetation occupies only a small fraction of the catchment, its conservation importance is considerable. In terms of scenic and heritage resources, the whole area has international significance and the Loch Lomond catchment requires special protection and management.     

Aspects of the hydrology and hydrography of Loch Lomond

A review is made of the rather limited studies that have been conducted into the available hydrological data for the catchment, and of the sparse hydrographic data relating to the Loch itself.     

The Loch Eil project: The bacterial flora and heterotrophic nitrogen fixation in sediments of Loch Eil

The organically enriched sediments of Loch Eil reduced acetylene (fixed nitrogen) at a higher rate than sediments in the Firth of Lome and other near shore marine locations. Sulphate-reducing bacteria (SRB) were implicated in nitrogen fixation although fixation rates did not correlate with the SRB numbers found in these sediments. The data suggest that a negative relationship may exist between nitrogen fixation and the sulphide content of sediments.     

Freshwater and wetland plant communities of Loch Lomond

Information on the aquatic and wetland vegetation of Loch Lomond, Scotland, is summarised for the period 1957–90. Aquatic macrophyte growth is estimated to occupy about 1% of the loch's total surface area, being limited to the 0–10 m euphotic zone, and probably excluded from much of this area by wave disturbance and unsuitable substrates. Aquatic vegetation is however abundant in sheltered bays and less-exposed shorelines, particularly in the South Basin of the loch. Although Littorella uniflora (L.) Aschers is the commonest, ubiquitous, submerged plant of the loch, three separate euhydrophyte communities have been identified within the loch. One of these is characterised by abundant stands of Elodea canadensis Michx., which appears to have invaded Loch Lomond some time between 1967–88, and has rapidly spread throughout the loch.     

A history of scientific research at Loch Leven,Kinross, Scotland

Loch Leven is a large, shallow lake in lowland Scotland, UK. Scientific research began here almost 200 years ago. Early research characterised the biodiversity and physical characteristics of the loch, providing an important historical background for future research. In the mid-1960s, this ad hoc approach was superseded by a more structured research programme under the umbrella of the International Biological Programme. This was the beginning of the Loch Leven long-term monitoring programme. Today, the results of these studies form one of the longest and most comprehensive limnological datasets for shallow freshwater lakes in the world, comprising more than 500 physical, chemical and biological variables collected at two-weekly intervals. To celebrate the 40th anniversary of the start of the long term monitoring programme, and to highlight the scientific investigations still being conducted at Loch Leven, the NERC Centre for Ecology & Hydrology (CEH) organised a symposium entitled “Loch Leven: 40 years of scientific research” in Kinross, Scotland, UK, on 11 December 2008. This examined the role of long-term monitoring in developing our understanding of the links between pollution, climate change and ecological responses in shallow lakes. This article introduces a series of papers summarising the scientific results presented at this meeting.     

Identifying from recent sediment records the effects of nutrients and climate on diatom dynamics in Loch Leven

1. Changes in nutrients and climate have occurred over approximately the same timescales in many European lake catchments. Here, we attempt to interpret the sedimentary diatom record of a large shallow lake, Loch Leven, in relation to these pressures using information gained from analysis of long‐term data sets of water quality, climate and planktonic diatoms. 2. The core data indicate the enrichment of Loch Leven starting in c. 1800–1850, most likely from agricultural practices in the catchment, with a more marked phase since c. 1940–1950 caused by increased phosphorus inputs from sewage treatment works, land drainage and a woollen mill. 3. While the recent diatom plankton remains are dominated by taxa associated with nutrient‐rich conditions, an increase in Aulacoseira subarctica relative to Stephanodiscus taxa since the mid‐1980s suggests that reductions in external catchment sources of nutrients (since 1985) may have resulted in partial recovery. This observation accords well with the long‐term monitoring series of water chemistry and phytoplankton. 4. On a decadal‐centennial scale, the eutrophication signal in the sediment record outweighs any evidence of climate as a control on the diatom community. However, at an inter‐annual scale, while the diatom data exhibit high variability, there are several changes in species composition in the recent fossil record that may be attributed to climatic controls. 5. The study highlights the value of a palaeolimnological approach, particularly when coupled with long‐term data sets, for developing our understanding of environmental change at a range of temporal scales. The diatom record in the sediment can be used effectively to track recovery from eutrophication, but requires greater understanding of contemporary ecology to fully interpret climate impacts. 6. The study illustrates the complexity of ecosystem response to synchronous changes in nutrients and climate, and the difficulty of disentangling the effects of these multiple, interacting pressures.     

Assessment of eutrophication in Loch Lomond by desk analysis

Phosphorus and chlorophyll a levels were predicted for Loch Lomond from desk-derived P loss coefficients and flushing rates related according to existing eutrophication models. These were in close keeping with measured values.     

A hermaphroditic Arctic charr from Loch Rannoch, Scotland

An individual Arctic charr from Loch Rannoch was found to contain a gonad the anterior portion of which consisted of ovarian tissue. This is an extremely rare condition in salmonid fish and in this instance is possibly the result of environmental contamination.     

Chemical investigations of Loch Etive,Scotland. III. Participate organic carbon and particulate organic nitrogen

The concentration of the suspended matter in Loch Etive varies with river discharge, biological production, and water movement. The contribution from phytoplankton production shows a seasonal trend, with the highest values in the spring and the lowest in winter. The carbon: chlorophyll a and nitrogen: chlorophyll a ratios in the photic zone (1,4–5, and 10 m) during the period of high production ranged from 54.0 to 400.0 and 6.0 to 38.0, respectively, the autumn bloom having higher ratios than the spring bloom. The increase of these ratios in the landward direction indicates the influence of terrestrial material. The C/N ratios in the surface (1 m) of the loch throughout the year fluctuated between 6.5–20.0, being the highest in winter. The C/N ratios in the bottom layers of the Lower Basin (40–50 m), Deep Basin (115–140 m) and the Head of the Loch (25–35 m) during the year ranged between 2.25–14.0, 5.0–38.0, and 3.0–28.5, respectively. The lowest ratios were mainly found in early autumn and associated with high levels of dissolved organic nitrogen and amonium. The accumulation of suspended matter in the deeper layers of the Deep Basin was caused by the input of organic detritus from the Lower Basin and eroded sediment from the basin slope. The lateral distribution of the C/N ratios may be related to the hydrographical features of the loch.     

The importance of Loch Lomond National Nature Reserve for Fish

Loch Lomond NNR with 19 fish species is ranked top in fish conservation value of 235 NNRs in Great Britain due to species diversity, presence of rare species and unusual forms and combinations.     

The physico-Chemical limnology of Loch Lomond

Loch Lomond, the largest freshwater lake in Britain, is physically divided into a number of distinct basins by geological structures. The northern part of the loch is long, narrow and deep whilst the southern area is broad and shallow with many islands scattered throughout it.The water chemistry of the loch is dictated by the geology of catchment and the quality of the rivers flowing into it. The two major rivers, the Falloch and the Endrick Water, are both of good quality with low nutrient content. Consequently, the loch is regarded as oligotrophic, though the southern area verges towards being mesotrophic.