Calcareous organisms composition

Figure 5.7. Isotopic composition of various groups of calcareous organisms. (After Swart, 1983.)...

In this paper we summarize our recent findings on paralytic shellfish toxins in tropical waters (8-15) with new assignment of a component previously unreported. It includes the confirmation of paralytic shellfish toxins in the dinoflagellate Pyrodinium bahamense war, aompressa and bivalver exposed to the organism (, with structural elucidation of three components (9,1 ). The detailed analyses of the toxin composition of crabs (11-13) and marine snails (13,14) and confirmation of a calcareous red alga Jania sp. as the primary source of the toxins ( 15) are also described. 

The process of removal of calcium by marine organisms in the water column is well known. Production of calcium carbonate by water column biological processes may be estimated from primary productivity and from the mean chemical composition of plankton. After death of the organisms and removal of the organic protective layer, the skeletons may undergo dissolution if they encounter water undersaturated with respect to their mineral composition. Active dissolution of calcium carbonate occurs mainly near the sediment-water interface in deep waters that are undersaturated with respect to both calcite and aragonite (see Chapter 4). Thus, calcium is regenerated from calcareous skeletons and, finally, only a small fraction of the initial production of these materials accumulates in sediments. An... 

Mitterer R.M. (1968) Amino acid composition of organic matrix in calcareous oolites. Science 167, 1498-1499. 

Many species of cestodes, especially the larvae, contain large numbers of curious concretions, termed calcareous corpuscles, made up of an organic base together with inorganic material. They are composed of concentric lamellae and vary in size in some species they are very large - 16-32 /xm (Spirometra mansonoides, E. granulosus) - but, in most species, they measure about 12 jam. They have been the subject of a number of studies (36, 135, 351, 385, 386, 594, 796, 912, 913, 914), but their composition, formation and, particularly, function still remain poorly understood. 

Inorganic sediment is supplied by erosion of material from exposed areas of high relief, and can be transported a considerable distance to the area of deposition. The composition of this detrital (or clastic) material varies, but aluminosilicate minerals are usually important. There are also biogenic sediments, resulting from the remains of organisms (e.g. calcareous and siliceous tests, peat) and chemical sediments formed by precipitation of minerals from solution (e.g. evaporites, some limestones and authi-genic infills of pores by quartz and calcite cements). 

The calcareous deposit formed on cathodically protected metal surfaces will also be affected by the presence of micro-organisms and macro-fouling. Physical disruption and alteration of structure, composition and crystal form will influence the response to cathodic protection. The consequent economic implications of changes in current density requirement for protection, and the engineering design implications and associated economics may be significant [Maines 1993]. Work is therefore required to improve the understanding of the relationship between... 

Turner, B.L., Cade-Menun, B.J. and Westermann, D.T. (2003a) Organic phosphorus composition and potential bioavailability in calcareous soils of the western United States. Soil Science Society of America Journal 67, 11 58-11 79. 

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