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.     

The Loch eil project: Simulation of the hydrology and sediment inputs to Loch Eil

The two objectives of the study were the assessment of the water and sediment response of the ungauged catchments draining to Loch Eil, and the analysis of the sensitivity of erosion processes to the variation of input precipitation and sediment characteristics. The technique employed was the application of the Strathclyde Sediment Model I, which had already been tested on the Scottish river basins using data from several sources. The method showed some potential but provided only a rough comparison with the actual sedimentation in the Loch.     

Environmental change and the chemical record in Loch Lomond sediments

The chemical record in Loch Lomond sediments deposited since the end of the last Ice Age provides evidence of the Flandrian marine transgression some 5500–7000 ¹⁴C years B.P., sedimentation rates and the influence of man's local activities, environmental pollution and its sources since the onset of the Industrial Revolution, and of elemental mobility linked with the reduction-diffusion-oxidation cycle of early sedimentary diagenesis. Information derived from vertical profiles of halogen elements bromine and iodine, radionuclides ¹⁴C and ²¹⁰Pb, heavy metals lead, zinc, and cadmium, stable lead isotopes ²⁰⁶Pb and ²⁰⁷Pb, and redox-sensitive elements manganese, iron and arsenic is reviewed and assessed.     

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.     

Planktonic foraminifera of the northern Indian Ocean: Distribution and preservation in surface sediments

In the northern Indian Ocean, planktonic foraminiferal tests accumulate in a wide variety of surface-water environments and depositional settings. This variability enables us to isolate the effects that surface-water ecology and differential dissolution have on the distribution of planktonic foraminifera from 251 geographically widespread surface sediment samples.Foraminiferal abundance varies from 0 to > 10⁴ whole foraminifera in the greater than 150 μm fraction per gram dry sediment. Values < 10 characterize the three deep basins of the equatorial Indian Ocean and the western Bay of Bengal. Foraminiferal tests are most abundant on carbonate covered Ninety-East and Carlsberg Ridges. Absolute abundance patterns are mainly controlled by non-ecological processes. Variations in dissolution resistant species (RSP) with water depth reveal that the foraminiferal lysocline (FL) varies regionally. The FL is deepest (3,800 m) in the equatorial region, rises abruptly to 3,300 m in the Arabian Sea, and varies from 2,600 m to near 2,000 m moving northward in the Bay of Bengal. Deep samples with anomalously low RSP (< 30%) suggest redeposition.Systematic geographic and depth-related variation is observed for the 17 most abundant foraminiferal species. Dissolution resistant species (G. menardii, G. tumida, G. dutertrei, P. obliquiloculata) generally exhibit a rapid and continuous increase in relative abundance at and below the FL. Susceptible species (G. ruber, G. bulloides, G. glutinata, for example) exhibit a rapid and continuous decrease in relative abundance at and below the FL. Moderately susceptible species (G. conglobatus, G. aequilateralis, G. conglomerata, for example) rapidly increase in abundance at the FL and systematically decrease with depth below the FL.Principal components analysis (PCA) of faunal data from minimally dissolved (< 30% RSP) samples reveals important ecologically related species intercorrelations. The major biogeographic gradient is the negative covarying relationship between aG. bulloides-G. glutinata species pair and a grouping ofG. sacculifer, G. conglobatus, G. aequilateralis, andG. ruber. PCA of all samples demonstrates how differential dissolution alters this and other species relationships. Species groupings that incorporateG. ruber, G. menardii, andG. dutertrei are particularly affected by dissolution.Comparison of average faunal data from minimally dissolved samples in the northern Indian Ocean with similar samples from other tropical regions suggests varying environmental factors produce distinct faunas within the tropical ocean. For example,G. bulloides, G. falconensis, andG. hexagona are significantly more abundant in northern Indian Ocean surface sediments while such species asG. ruber, G. sacculifer, G. dutertrei, andP. obliquiloculata dominate in other tropical regions.     

Plant pigments and light penetration in intertidal sediments

Summary 1. Chromatographic analyses were used to determine the concentration of plant pigments in the sediments at four intertidal stations at Barnstable Harbor, Massachusetts, U.S.A. Two of the stations were sand flats exposed to relatively strong tidal currents and two were mud flats subject to weak currents. In general, highest concentrations of all pigments were found in the upper mm. Chlorophyll-a, chlorophyll-c and fucoxanthin concentrations decreased with depth but considerable quantities (20 to 50% of surface values) were found at 5 cm. Diatoxanthin, diadinoxanthin and carotene concentrations did not decrease with depth. Quantitative differences between the stations were noted.2. With one exception, measurements of light attenuation through these sediments, were roughly correlated with mean particle size.3. On one station, living diatoms were found as deep as 5 cm, but the vertical distribution of the pigments could not be explained by the diatom distribution.

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Pflanzliche Pigmente und Lichtpenetration in Sedimenten des Gezeitenbereichs

Kurzfassung Die Verteilung pflanzlicher Pigmente und die Lichtpenetration wurden in vier verschiedenen Sedimenttypen untersucht, und zwar bei Barnstable Harbor, Massachusetts, USA. Mit einer Ausnahme erwies sich die Lichtattenuation als Funktion der Partikelgröße des Sediments. Obgleich lokale Unterschiede in der Pigmentverteilung an den einzelnen Untersuchungs-stationen beobachtet wurden, war das Verteilungsmuster grundsätzlich ähnlich. Die Konzentrationsmaxima lagen bei allen Pigmenten im obsersten Sedimentmillimeter. Die Konzentrationen der Chlorophylle und des Fucoxanthins verringerten sich allmählich mit zunehmender Tiefe; sie waren jedoch bei 5 cm Tiefe mit 20 bis 50% der Oberflächenwerte noch sehr hoch. Die Konzentrationen von Karotinen und anderen Xanthophyllen verringerten sich nicht mit der Tiefe. Die Verbreitung beweglicher pennater Diatomeen wurde an einer Station geprüft; es zeigte sich, daß die Mehrzahl der Individuen auf die obersten 3 mm beschränkt war. Lebende Diatomeen wurden bis zu einer Tiefe von 5 cm gefunden. Der Gehalt an organischer Substanz im Sediment wurde bestimmt und mögliche Korrelationen zwischen dessen prozentualem Pigmentanteil und einigen physikalischen Parametern der Stationen erörtert.

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Contribution No. 90 Chesapeake Bay Institute, The Johns Hopkins University. Partially supported by the U. S. Atomic Energy Commission (Contract AT [30-1] 1477), and the Office of Naval Research (Contract Nonr 248 [54]) and NIH training grant 5 T1 GM 535-04.     

The fauna of a polluted shore in the firth of forth

Summary 1. During a survey of the Edinburgh shore fauna it was found that on one stretch, similar to neighbouring areas in the habitats available, there occurred only about 33% of the larger invertebrates found regularly elsewhere. This can be related to the onshore movement of sewage by local currents to a greater degree than in neighbouring areas.2. A more detailed survey of selected common animals and rock surfaces made by a simple method which avoids detailed searching and sampling, has shown that several animals which would normally be present are scarce or absent. These includeActinia equina, Pomatoceros triqueter, Patella vulgata andThais lapillus.3.Balanus spp.,Mytilus edulis andLittorina littorea are common in most suitable places, but the lower shore is dominated by dense populations ofPolydora ciliata forming in some places a thick mat of tubes which excludes many other sessile organisms. This mat blends with, and on higher rocks is replaced by, a mat of small algae withFabricia sabella also present in high densities. Both of these matforming worms also occur among barnacles andFabricia is common in the more varied association living under stones and boulders not bedded in mud.4. The density of suspended matter in the water is thought to be the main factor causing the scarcity of some animals and the abundance of others, notably the matforming species. The effect may be direct, e. g. on feeding and respiratory mechanisms, or by provision of food and tube-building materials, or it may be indirect through its influence on other species.5. The absence of certain common species and the abundance of mat-forming organisms are regarded as possible indicators of the degree of shore pollution.

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Die Fauna einer verunreinigten Küstenstrecke im Firth of Forth

Kurzfassung Bei einer Untersuchung der Küstenfauna an den Ufern in der Nähe der Stadt Edinburgh, die bis zu einem gewissen Grade von Kloakenwasser-Verunreinigung betroffen ist, wurde festgestellt, daß eine Strecke von ungefähr 1 1/2 km westlich des Hafens von Granton bemerkenswert arm an Arten ist. Dies scheint in Beziehung zu stehen zur Bewegung der Abwässer auf diese Küste hin während der Flutzeit; sie wird durch lokale Strömungen hervorgerufen. Die Untersuchungen beschränken sich hauptsächlich auf Organismen, die auf einer Reihe von Sandsteinklippen leben, welche voneinander durch Strecken von Schlick oder schlammigem Sand getrennt sind. Die am häufigsten vorkommenden Tiere sind — genau wie an den beachbarten Strecken der Küste — Balaniden,Mytilus edulis undLittorina littorea. Größere Algen sind verhältnismäßig selten, doch treten Grünalgen zahlreicher auf als in den anliegenden Gebieten. Wie an anderen verunreinigten Fundorten weist die Fauna eine Verringerung an Arten, zugleich jedoch eine sehr große Individuenzahl an widerstandsfähigen Arten auf. Vergleiche, die zwischen diesen Klippen und anderen ähnlichen Fundorten östlich und westlich davon angestellt wurden, zeigen, daß mehrere häufig auftretende Spezies in diesem Gebiet selten oder gar nicht vorhanden sind, darunterHalichondria panicea, Actinia equina, Pomatoceros triqueter, Patella vulgata, Thais lapillus, und gewisse Polyzoen.Fabricia sabella, Polydora ciliata und andere mit ihnen assoziierten Tiere sind weit verbreitet, scheinen aber nur in schlickigen Substraten in dichten Beständen vorzukommen.

     

Depth distribution of photosynthetic pigments and diatoms in the sediments of a microtidal fjord

The depth distribution of photosynthetic pigments and benthic marine diatoms was investigated in late spring at three different sites on the Swedish west coast. At each site, sediment cores were taken at six depths (7–35 m) by scuba divers. It was hypothesized that (1) living benthic diatoms constitute a substantial part of the benthic microflora even at depths where the light levels are <1% of the surface irradiance, and (2) the changing light environment along the depth gradient will be reflected in (a) the composition of diatom assemblages, and (b) different pigment ratios. Sediment microalgal communities were analysed using epifluorescence microscopy (to study live cells), light microscopy and scanning electron microscopy (diatom preparations), and HPLC (photosynthetic pigments). Pigments were calculated as concentrations (mg m^–2) and as ratios relative to chlorophyll a. Hypothesis (1) was accepted. At 20 m, the irradiance was 0.2% of surface irradiance and at 7 m, 1%. Living (epifluorescent) benthic diatoms were found down to 20 m at all sites. The cell counts corroborated the diatom pigment concentrations, decreasing with depth from 7 to 25 m, levelling out between 25 and 35 m. There were significant positive correlations between chlorophyll a and living (epifluorescent) benthic diatoms and between the diatom pigment fucoxanthin and chlorophyll a. Hypothesis (2) was only partly accepted because it could not be shown that light was the main environmental factor. A principal component analysis on diatom species showed that pelagic forms characterized the deeper locations (25–35 m), and epipelic–epipsammic taxa the shallower sites (7–20 m). Redundancy analyses showed a significant relationship between diatom taxa and environmental factors – temperature, salinity, and light intensities explained 57% of diatom taxa variations.     

Factors influencing the variability of pigments in the surface sediments of mountain lakes

1. Surface sediment biofilm samples from 82 Pyrenean lakes were analysed for marker pigment composition using high performance liquid chromatography (HPLC). 2. Variability in the pigment composition among lakes was investigated by multivariate statistical analyses using a large data set of factors describing lake chemical, physical, morphological and catchment characteristics. 3. Due to the widely varying light penetration in the lakes, the most significant gradient of pigment composition extended from a benthic to a planktonic signal. The most important pigments in the gradient were alloxanthin (cryptophytes marker pigment, planktonic signal) and diatoxanthin (diatoms marker pigment, benthic signal). The molar ratio between these two marker pigments was positively correlated with lake depth. 4. Chlorophyll‐a preservation was found to be positively related to light penetration and the development of an autothrophic biofilm on the surface sediment and negatively related to decreasing pH and the percentage of alpine meadows in the lake catchments. 5. Zooplankton marker pigments in the surface sediment, including grazing by‐products (e.g. phaeophorbides) and carotenoids (astaxanthin, canthaxanthin, echinenone) incorporated into their tissues, were correlated with the areal abundance of zooplankton. 6. Marker pigments for photosynthetic bacteria, BChl‐e and okenone, were found mainly in relatively shallow lakes with large catchments that are forested, probably because of their higher loading of allochthonous organic matter. 7. The evaluation of a preservation index (Chl‐a expressed as a percentage of a‐phorbins) and the alloxanthin/diatoxanthin ratios throughout the sediment record of mountain lakes can provide evidence of historical changes in the relative importance of planktonic versus benthic primary production and might ultimately be interpreted in terms of climatic or environmental changes.     

The diatom assemblage of a marl core from Linton Loch

Summary

Diatom data from Linton Loch show five diatom assemblage zones, together with stratigraphic evidence indicating some aspects of the development of the lake basin during the Flandrian. Results show an early Flandrian dominance of planktonic diatom species in the lake waters with the later development of epiphytic species as the hydrosere encroached. Following deforestation in the catchment, water levels rose in the basin when benthic diatoms became dominant.     

Breakdown of phytoplankton pigments in Baltic sediments: effects of anoxia and loss of deposit-feeding macrofauna

We examined the decay of chlorophyll a and the carotenoid fucoxanthin in oxic and anoxic sediment microcosms, with and without the deposit-feeding benthic amphipod Monoporeia affinis, over 57 days at 5 degrees C. Deep frozen phytoplankton from the Baltic Sea proper was added to all but a few microcosms. The range of chlorophyll a and fucoxanthin decay rate constants observed in microcosms with phytoplankton addition was 0.04-0.07 day(-1). The fastest pigment decay and build-up of chlorophyll breakdown products after phytoplankton addition were found in oxic treatments with amphipods. No effects of amphipods on pigment breakdown were found in anoxic treatments, or in treatments without phytoplankton addition. Greater losses of chlorophyll a in oxic (96%) than in anoxic (80%) treatments after 57 days indicates that preservation of sedimentary organic matter will be enhanced during periods of anoxia. Due to slow recruitment and recolonization in Baltic sediments, a single anoxic event may cause long-term (years) absence of significant macrobenthos. Anoxic events will thus not only reduce decay of plant pigments, and presumably other organic matter, while they last, but will also have longer-term effects, through elimination of macrofauna, which when present enhance organic matter decomposition.     

Reproductive isolation and genetic differentiation of ferox trout from sympatric brown trout in Loch Awe and Loch Laggan, Scotland

Molecular marker studies reported here, involving allozymes, mitochondrial DNA and microsatellites, demonstrate that ferox brown trout Salmo trutta in Lochs Awe and Laggan, Scotland, are reproductively isolated and genetically distinct from co-occurring brown trout. Ferox were shown to spawn primarily, and possibly solely, in a single large river in each lake system making them particularly vulnerable to environmental changes. Although a low level of introgression seems to have occurred with sympatric brown trout, possibly as a result of human-induced habitat alterations and stocking, ferox trout in these two lakes meet the requirements for classification as a distinct biological, phylogenetic and morphological species. It is proposed that the scientific name Salmo ferox Jardine, 1835 , as already applied to Lough Melvin (Ireland) ferox, should be extended to Awe and Laggan ferox.     

The laminated sediments of Loch Ness, Scotland: Preliminary report on the construction of a chronology of sedimentation and its potential use in assessing Holocene climatic variability

Two sediment cores, ca. 6 m long, have been recovered from the north basin of Loch Ness, Scotland. Each consists of ca. 4.5 m of laminated gyttja, terminating in a basal grey, unlaminated clay. A suite of three ¹⁴C AMS dates have been obtained, and place the base of the gyttja at ca. 9500 yr B.P. Investigations into the structure, composition and formation of the laminae are in progress. Analysis by Backscatter Scanning Electron Microscopy (BSEM) has demonstrated that they consist of couplets comprising dark, clay-rich sediments thought to be deposited from spring to autumn, and pale, silt-rich layers believed to represent sedimentation through winter. The laminae are thus thought to record incidence and intensity of streamflow into the Loch over the past nine millennia, and thus illustrate environmental change over the region for most of the Holocene. X-ray densitometry has been utilised in order to count the laminations and test the hypothesis that they are varves. It has, however, proved difficult to obtain a continuous sequence of countable laminations, although it has been possible to construct a fragmented, floating chronology which indicates that the hypothesis may be correct. Examination of lamination thickness reveals that although the average rate of sedimentation throughout the time periods studied seems to have remained fairly constant, significant variations have occurred. As Loch Ness is located on the northwest oceanic fringe of Europe, any climatic signal which the laminations contain will be closely related to even larger scale events over and within the North Atlantic Ocean, which is a major controller of global climate. Preliminary statistical investigation of sequences of laminae is being carried out in order to search for periodicity of sedimentation which may then be related to appropriate climatic indices.     

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.     

The nature of melanin pigments from some micro- and macromycetes

New inhibitors of melanin formation by micromycetes Aspergillus carbonarius, Alternaria alternata, and Paecilomyces variotii and basidiomycetes Inonotus obliquus and Phellinus robustus were found. Precursors of melanin pigments were isolated and identified. p-Hydroxybenzoic acid was identified among the products of alkaline degradation of melanin formed by micromycetes, whereas in the case of macromycetes this was protocatechuic acid. Therefore, melanins of the former were found to belong to the dihydronaphthalene group, whereas those of the latter belong to catechols.     

How fish-helminth associations arise: an example from Arctic charr in Loch Rannoch

Three sympatric morphs of Arctic charr Salvelinus alpinus occur in Loch Rannoch, Scotland, and are identified by their differing head morphology and diet. These are small-headed benthic, large-headed benthic and pelagic morphs. Six species of endoparasitic helminth were found in the fish, but the morphs had different patterns of infection. Overall infections in pelagic charr were heavier than in large-headed benthics, which were in turn heavier than in small-headed benthics, even though benthic charr live longer than pelagics. Pelagic fish had high prevalences and intensities of pseudophyllidean tapeworms, the intermediate hosts of which are copepods. The prevalence and intensity of metacercariae of Diplostomum sp. (the intermediate hosts of which are snails) were high in the benthic morphs. The results are discussed in terms of the effects of ecological factors on transmission of helminth parasites to their hosts and the evolution of host-parasite associations.     

The distribution of intertidal algae in a Hebridean Loch

Summary

Ten species of Rhopalostroma are currently known and all are from either Africa or Asia. Rhopalostroma gracile D. Hawksw. and R. kanyae Whalley &; Thienhirun have previously been reported from Thailand. A further species, R. lekae sp. no v., is now described from Thailand. Thus three out of the eleven known species of Rhopalostroma are from Thailand.