|Basic Information||Biotope classification||Ecology||Habitat preferences and distribution||Species composition||Sensitivity||Importance|
Image Sue Scott - A dense mat of Ascophyllum nodosum mackaii. Image width ca 40 cm.
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LR.SLR.FX.AscX.mac recorded () and expected () distribution in Britain and Ireland (see below)
An ecad is a distinctive form of a species which develops in response to environmental conditions rather than genotypic differences. Ascophyllum nodosum ecad mackaii arises when detached fragments of the species are deposited onto sheltered shores where they continue to multiply and branch independently of the original fragment (Chock & Mathieson, 1976). The frond has extensive dichotomous branching and bears few air bladders. The plants drift in large, spherical masses in sheltered waters.
Extensive beds sometimes develop in appropriate conditions. However, more often beds are very local, often only a few metres across, and typically in small bays between rock outcrops (Anonymous, 1999(t)).
The presence of the Ascophyllum nodosum ecad mackaii in any particular situation depends on the combination of a number of conditions applying at a tide level between high and low water neaps: frequent alternation of high and low salinities. Very sheltered sea loch shores where freshwater runs or seeps across the shore can provide suitable conditions. The freshwater forms a brackish layer at the loch surface over the saline waters beneath, which moves up and down with the tides and subjects the shores to regularly fluctuating salinities. Therefore, a supply of freshwater is of primary importance
good shelter from wave action because of the unattached state of the ecad
absence of fast moving water, whether caused by freshwater streams or tidal conditions
flat, undulating or slightly sloping shore profile where stability is high
substratum type, the porosity of which affects the conditions of salinity also influences, to some extent, the development of the ecad.
Chock & Mathieson (1979) demonstrated the physiological responses of Ascophyllum nodosum and its detached ecad scorpioides were similar under varying conditions of light intensity, temperature and salinity.
The loose mats of Ascophyllum nodosum ecad mackaii provide a sheltered and humid habitat for many mobile mid-shore animals which would otherwise be unable to live on open sediments or shingle. Gammarid amphipods, shore crabs and littorinid snails hide and feed amongst the weed, while barnacles and mussels are often attached to stones beneath. Fish such as young common eels Anguilla anguilla and viviparous blennies Zoarces viviparus may also shelter in the weed.
This review can be cited as follows:
Hill, J.M. 2001. Ascophyllum nodosum ecad mackaii beds on extremely sheltered mid eulittoral mixed substrata. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 04/03/2015]. Available from: <http://www.marlin.ac.uk/habitatecology.php?habitatid=138&code=1997>