Biology Reference
In-Depth Information
Chapter 5
Seaweed Acclimation to Salinity
and Desiccation Stress
Ulf Karsten
Dedicated to my mentor Professor Dr. Gunter O. Kirst on the
occasion of his 70th birthday.
5.1 Variability of Salinity in Seaweed Habitats
Salinity is a technical term in marine sciences and represents the sum of all
dissolved salts of a defined body of water. Therefore, marine biologists for a long
time used the expression
promille
(
)or
parts per thousands
(ppt) to describe
salinity concentration. In contrast, since 1978 oceanographers defined salinity in the
Practical Salinity Scale as dimensionless Practical Salinity Units (PSU) which is the
conductivity ratio of a seawater sample to a standard KCl solution. In October 2010,
the Intergovernmental Oceanographic Commission (IOC), International Associa-
tion for the Physical Sciences of the Oceans (IAPSO), and the Scientific Committee
on Oceanic Research (SCOR) jointly adopted a new standard for the calculation of
the thermodynamic properties of seawater. This new standard, called TEOS-10,
uses Absolute Salinity
S
A
(mass fraction of salt in seawater) to describe the salt
content of seawater. Ocean salinities now have units of g dissolved salts kg
1
water
(
http://www.teos-10.org
; Wright et al.
2010
). Therefore, all salinities throughout
the text are expressed as Absolute Salinity
S
A
.
The chemical composition of the dissolved salts is relatively constant throughout
the open oceans due to intensive mixing, and it varies only between 33 and 37
S
A
,
gradually decreasing from the subtropics toward the tropics and polar seas. In
contrast, salinity strongly varies in nearshore waters and estuaries where river
freshwater mixes with marine water bodies. Here horizontal and vertical gradients
between 0 and 33
S
A
can be measured. The degree of salt dilution in estuaries
‰
U. Karsten (
*
)
Institute of Biological Sciences, Applied Ecology, University of Rostock,
Albert-Einstein-Strasse 3, 18059 Rostock, Germany
e-mail:
ulf.karsten@uni-rostock.de
