Ecological and palaeoecological studies of endolith boring, molluscan grazing and echinoid feeding traces
Başlık:
Ecological and palaeoecological studies of endolith boring, molluscan grazing and echinoid feeding traces
Yazar:
Akpan, Etie Ben, author.
ISBN:
9780438052987
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (303 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: G. E. Farrow.
Özet:
Calcareous substrates, principally dead molluscan shells collec mainly with naturalist's dredge from the sea bottom in the Firths of Clyde and Lorne (off the west coast of Scotland) and the sea around Orkney Islands (North Scotland) were examined. From this survey, the distribution of micro-borings, molluscan and regular echinoid feeding traces from sites encompassing a range of depths from about 2-l60m have been made. Binocular microscope and scanning electron microscope as well as X-ray radiography have been used in the analysis of the samples. The following micro-algal vegetation or their borings are recognised and described:- Conchocelis phase of red algae in the Bangiaceae family (Rhodophyta); Ostreobium quekettii, Eugomontia sacculata, Phaeophila sp. (Chlorophyta); Plectonema terebrans and Hyella sp. (Cyanophyta). Other micro-endolithic borers include Fungi, clionid sponges Cliona celata and C. vastifica as well as phoronids. Distinguishable bioabrasion marks are mainly products of the teeth of the limpet Acmaea virginea, the chiton Lepidopleurus asellus and regular echinoids, Acmaea is solely dependent on micro-algae for nutrition and the presence of its feeding traces implies algal boring activity or encrustation; chiton and regular echinoid feeding traces are not necessarily connected with algae. Endolithic algae are bathymetrically zoned. Fungi, sponges and phoronids apparently are not depth controlled. Eugomontia and Phaeophila are limited to the upper part of the water column probably because of their adaptation to strong light intensities. Ostreobium and Conchocelis are the deepest growing and widest ranging algae. The photic limit in the three regions therefore is defined biologically by the deepest positive occurrence of one of these two algae. This depth is about 30m in the Firths of Clyde and Lorne (approx. 56°N) and 40m in the sea around Orkney Islands (approx, 59°N). Variations in the photic limit are caused by the difference in water clarity: the Firths of Clyde and Lorne being more turbid than Orkney sea. Algal boring density is high in sheltered bay sites with little or no movement of the shells, but low in areas of sandy bottom above wavebase. The distribution and depth ranges of Acmaea grazing traces are similar to those of the algae. Although most regular echinoid feeding traces were found within the photic zone, substrates with echinoid marks have been encountered in deeper water. Traces made by chitons have been found at a depth of l60m in the Firth of Lorne. The results of the study of recent endolithic borings and feeding traces have been applied to early Holocene sediments and the associated shells at Ardyne Point and Irvine 'great bend' succession in order to suggest the environmental conditions under which they were formed. It is proposed that the post-Glacial Ardyne Point sediments were formed in shallow (<13m) marine, low energy conditions. Analysis of microborings from the 'great bend' succession at Irvine shows changing environmental conditions from a deeper (approx. 10m) and relatively low energy bottom to an intertidal habitat subjected to tidal currents and waves. Acmaea-like grazing traces occur on ammonite moulds from the Gault sediments (M. Albian) at Folkestone, south-east England, from which it may be inferred that these sediments were deposited within the photic zone.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684444.1) | 684444-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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