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13
Fig. 19.1
d
C signatures of different macroalgae as a proxy of their carbon use strategy
( n ¼ 857, representing 370 species sampled from ten thermographic regions described by Adey
and Steneck 2001 ). Horizontal lines and bars to the right delimit the range of possible values for
species restricted wholly to CO 2 or HCO 3 ¯ (see text and cf Maberly et al. 1992 ). The sources of
data used here are Black and Bender ( 1976 ), Bode et al. ( 2006 ), Corbisier et al. ( 2006 ), Dunton
( 2001 ), Fischer and Wiecke ( 1992 ), Kang et al. ( 2008 ), Kevekordes et al. ( 2006 ), Kubler and
Raven ( 1994 ), Laurand and Riera ( 2006 ), Maberly et al. ( 1992 ), Pinnegar and Polunin ( 2000 ),
Raven et al. ( 1995 , 2002b ), Runcie et al. ( 2008 ; unidentified Corallinales not included), Vizzini
and Mazzola ( 2006 ), Wang and Yeh ( 2003 ), and Wozniak et al. ( 2006 )
13 C more negative than -30
diffusive CO 2 uptake where macroalgae with
d
also
have
(Raven et al. 1995 ; Runcie et al. 2008 ). Several conditions of
using stable isotopes to describe the carbon physiology of macroalgae are discussed
by Raven et al. ( 2002b ).
Using pH drift experiments and carbonic anhydrase activity measurements, the
preference of different macroalgae for either CO 2 or HCO 3 or both as source of
inorganic carbon has previously been compiled and reviewed (Table 3 in Gao and
McKinley 1994 and references therein). For example, pH drift measurements showed
that the brown alga Carpophyllum sp. most likely uses CO 2 rather than HCO 3
(Dromgoole 1978 ). On the other hand, using
D
above 20
13 C data in the literature as a proxy
for carbon use, the values for seaweeds (Fig. 19.1 )varyfrom-0.64
d
for Halimeda
distorta (Chlorophyta: Bryopsidophyceae) collected from 99 m depth at Penguin
Bank off the island of Moloka'i, Hawaii archipelago (Runcie et al. 2008 )to
for Georgiella confluens (Rhodophyta: Floridiophyceae) from Anvers
Island off the Antarctic Peninsula (Dunton 2001 ). Most seaweeds have
35.3
13 Cbetween
d
, within the range in which both CO 2 and HCO 3 use can occur
(Maberly et al. 1992 ; Raven et al. 1995 ). Macroalgae that rely solely on HCO 3 as
carbon source (
30 and
10
13 C
) are 10 greens, 5 browns, and 6 reds while macroalgae
that depend on CO 2 diffusion (
d
>
10
13 C
) consist of 6 greens, 1 brown, and 51
reds. Most of these CO 2 -using deep water red macroalgae belongs to the Class
Florideophyceae (94%), with 51% from the Order Ceramiales, 18% Plocamiales,
d
<
-30
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