Environmental Engineering Reference
In-Depth Information
Figs. 1 and 2. Intertidal and subtidal communities at Puerto Madryn, Chubut Province,
Argentina. 1. Dense, interwoven branches of Corallina offi cinalis , Dictyota sp., Ulva spp. and
Leathesia difformis macroalgae form dense turfs in the low intertidal zone. 2. Subtidal turf
formed by red ( Polysiphonia spp., Ceramium spp.), brown ( Dictyota sp.) and green ( Codium
spp., Ulva spp.) macroalgae.
The term seaweed traditionally includes only macroscopic, multicellular
red, green, and brown marine algae. These algae can grow from a few
millimetres in size up to more than 60 m, but all of them have microscopic
life stages.
Seaweeds are used in eastern countries as sea-vegetables for food
consumption, as Porphyra (Nori), Rhodymenia (Dulse), Laminaria saccharina
(Kombu) , Chondrus and Ulva blades, because they are rich in vitamins,
minerals, and proteins, and also have been reported as potential sources of
bioactive compounds, and act as antibacterial and antiviral agents (Mabeau
and Fleurence 1993, Vo and Kim 2010).
Seaweed assemblages grow mainly on rocky shores, being one of the
most complex and compact habitats (Morton 1991). The most impressive
feature of rocky shores is the zonation of the available space into distinct
vertical bands (Lobban and Harrison 1997). These vertical subdivisions are
separated on the basis of light penetration in the euphotic region where
submarine light supports plant growth, and the aphotic region where
light does not penetrate (Lüning 1990). There is also a horizontal gradient
associated with exposure to wave action with greater wave force and
frequency at exposed headlands than in bays or inlets (Santelices et al.
2009). Along with the depth gradient, the seaweeds are exposed to other
environmental parameters. Species settling in the supralittoral zone are
exposed to desiccation, high solar radiation and also atmospheric changes
in temperature while species settling in the eulittoral zone (intertidal fridge)
are exposed to regular and extreme changes in abiotic conditions, based on
tidal infl uence (Davison and Pearson 1996). In the upper intertidal, seaweeds
are usually controlled by abiotic factors that result in desiccation due to high
temperatures and intense solar radiation (Davison and Pearson 1996). In
constrat, in the lower intertidal, seaweed species are more often infl uenced
by biotic factors such as competition or grazing (Dawes 1998).
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