Biology Reference
In-Depth Information
Fig. 17.5
Conceptual figure of the main abiotic and biotic factors affecting the growth of floating
algae and thus their persistence at the sea surface
photoinhibition when transplanted close to the sea surface (Karsten et al.
2001
). At
low latitudes these photoacclimation responses were costly for
M. pyrifera
, which
was reflected in their overall diminished growth responses, implying lower persis-
tence due to combined effects of high water temperatures and high light conditions
(Roth
ausler et al.
2011a
). While short-term exposure to UVA and UVB radiation
induces the production of UV-absorbing phlorotannins in blades of benthic
M. pyrifera
(Swanson and Druehl
2002
), at present it is not known whether floating
M. pyrifera
can also increase the phlorotannin content in response to elevated UV
exposure as a protection of their photosynthetic tissues.
€
17.3.2 Temperature
Temperature is one of the most important factors controlling growth and persis-
tence of floating seaweeds (Hobday
2000a
; Roth
ausler et al.
2009
). For instance,
algae from temperate waters lose biomass (Fig.
17.6
), and thus floating capacity,
when experiencing thermal stress on their floating voyages into warmer oceanic
regions. Hobday (
2000a
) showed for the temperate
M. pyrifera
from southern
California that
€
the aging rate of kelp blades was low at surrounding water
20
C but substantially increased above this threshold. Recent
temperatures
<
