|
Maerl (or marl) is a collective name for Coralline red algae with a certain growth habit. Maerl grows at a rate of ∼1mm per year.〔 Blake, C. and Maggs, C.A. (2003) Comparative growth rates and internal banding periodicity of maerl species (Corallinales, Rhodophyta) from northern Europe. ''Phycologia'' 42, 606–612.〕 It accumulates as unattached particles and forms extensive beds in suitable sublittoral sites.〔Vize, S.; Blake, C.; Hinojosa, G. and Maggs, C.A. 2003. The distribution and composition of maerl beds in Northern Ireland. ''PMNHS Newsletter'' No.13 p.26〕 ==Description== In Europe maerl beds occur throughout the Mediterranean, along most of the Atlantic coast from Portugal to Norway, and in the English Channel, Irish Sea and North Sea. 〔Grall, J., Le Loc’h, F., Guyonnet, B., and Riera, P. (2006) Community structure and food web based on stable isotopes (δ15N and δ13C) analysis of a North Eastern Atlantic maerl bed. '' Journal of Experimental Marine Biology and Ecology '' 338, 1-15 () Available at: http://horizon.documentation.ird.fr/exl-doc/vcc/2006/11/010037649.pdf〕 The distribution of maerl is dependent on water movement, light and salinity concentration. 〔Wilson, S., Blake, C., Berges, J.A., and Maggs, C.A. (2004) Environmental tolerances of free-living coralline algae (maerl): implications for European marine conservation. '' Journal of Biological Conservation '' 120, 279-289. () Available at: ftp://ftp.soc.soton.ac.uk/pub/falmouth/Falmouth2009/.../Mearl2.PDF〕 Maerl beds occur in the photic zone, and can be found to around 30 m depth in the British Isles and up to 120 m deep in the Mediterranean.〔Hall-Spencer, JM. and Moore, PG. (2000) Scallop dredging has profound, long-term impacts on maerl habitats. '' ICES Journal of Marine Science '' 57, 1407-1415.〕 Maerl deposits can reach up to 10 m thick, but are usually much thinner; carbon dating has shown that they can be more than 5500 years old.〔Grall, J. and Hall-Spencer, J.M. (2003) Problems facing maerl conservation in Brittany. '' Journal of Aquatic Conservation: Marine and Freshwater Ecosystems '' 13, 55-64. () Available at: http://www.ukmpas.org/pdf/Grall_Hall-Spencer_2003.pdf〕 In the British Isles maerl is composed of three species of coralline algae growing loose in beds of fragmented nodules in the sub-littoral. The species generally involved are: ''Lithothamnion corallioides'',() ''Lithothamnion glaciale'' and ''Phymatolithon calcareum''.〔Irvine, L.M and Chamberlain, Y.M. 1994. ''Seaweeds of the British Isles.'' Volume ''1'', Part 2B. The Natural History Museum, London. ISBN 0-11-310016-7〕() Maerl is dredged from the sea floor and crushed to form a powder. It is still harvested around the coasts of Brittany in France and Bantry Bay, Ireland, and is a popular fertilizer for organic gardening. It was also dredged off Falmouth, Cornwall, but this ceased in 2004. Scientists investigated Falmouth maerl and found that ''L. corallioides'' predominated down to 6 m and ''P. calcareum'' from 6-10 m (Blunden ''et al.'', 1981).〔 Blunden, G.; Farnham, W. F.; Jephson, N.; Barwell, C. J.; Fenn, R. H. and Plunkett, B. A. (1981) The composition of maerl beds of economic interest in northern Brittany, Cornwall, and Ireland. ''Proceedings of the International Seaweed Symposium.'' 10: 651 - 656〕〔Blunden, G; Campbell, S A; Smith, J R; Guiry, M D; Hession, C C and Griffin, R L (1997) Chemical and physical characterization of calcified red algal deposits known as maërl. ''J. Applied. Phycol.'' 9: 11 - 17〕 Chemical analysis of maerl showed that it contained 32.1% CaCO3 and 3.1% MgCO3 (dry weight). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「maerl」の詳細全文を読む スポンサード リンク
|