Biology Reference
In-Depth Information
trends of eutrophication and overfishing and their impact on algal blooms in combi-
nation with other global changes. We will conclude with a discussion on management
options to help reduce the escalation of bloom occurrences worldwide.
21.2 Occurrence of Macroalgal Blooms and Their Ecological
Consequences
Macroalgal blooms are widespread along the coasts of the world (Table
21.1
;
Morand and Merceron
2005
; Ye et al.
2011
), forming dense mats or canopies in
shallow estuaries and coastal lagoons (Valiela et al.
1992
; Sfriso et al.
1992
),
accumulating on beaches as wrack (Morand and Merceron
2005
), overgrowing
corals (Smith
1981
; Hughes
1994
; Lapointe et al.
2005a
,
b
), and affecting seagrass,
soft-bottom, and rocky shore benthic communities (D´az et al.
2002
; Fox et al.
2009
). Blooms of green, red, and brown macroalgae are common, although among
these there are a few cosmopolitan species belonging to the genera
Ulva,
Chaetomorpha, Cladophora
,
Gracilaria
, and
Pylaiella
(Table
21.1
). Recent
reviews on green algal tides showed bloom occurrences in most marine water
bodies adjacent to highly urbanized or agricultural areas throughout Europe,
Australia, New Zealand, Asia, and North and Central America (Morand and
Merceron
2005
; Teichberg et al.
2010
; Ye et al.
2011
). Some of the most famous
examples of macroalgal blooms include the drift mats of
Ulva
spp. in Brittany,
France (Morand and Merceron
2005
) and Venice Lagoon (Sfriso et al.
1992
; Sfriso
and Marcomini
1997
),
Cladophora
spp. in Peel Harvey Estuary, Australia (Lavery
et al.
1991
), and the more recent widely publicized
Ulva prolifera
blooms in the
Yellow Sea, China during the 2008 summer Olympics with an estimated biomass of
approximately 20 million wet tons (Liu et al.
2009
; Gao et al.
2010
; Ye et al.
2011
).
Blooms of macroalgae have become a major ecological and economic problem in
coastal habitats (Table
21.1
, Fig.
21.1
). Seaweed wrack accumulating on beaches
can produce foul odors and release toxic hydrogen sulfide gas (Wilce et al.
1982
),
mats and deep canopies of seaweeds physically obliterate other primary producers
including seagrasses (Valiela et al.
1997
; Hauxwell et al.
2001
; McGlathery
2001
)
and corals (Hughes
1994
; Lapointe
1997
; Lapointe et al.
2005a
,
b
), and their decay
causes anoxic conditions that lead to fish and shellfish kills (D'Avanzo et al.
1996
;
Valiela et al.
1997
; Diaz
2001
). Macroalgal blooms not only affect natural coastal
communities and ecosystem function (Duarte
1995
), but have high economic
consequences by making coastal environments increasingly undesirable for recrea-
tional uses and threatening commercially important harvests (Valiela et al.
1992
;
Raffaelli et al.
1998
; Oesterling and Pihl
2001
). Often, the macroalgal species that
form blooms are nonnative, such as
Gracilaria vermiculophylla
,
Codium
spp., and
Undaria pinnatifida,
and have the ability to quickly adapt to new environments and
outcompete native species due to high stress tolerances, rapid nutrient uptake and
growth rates, and varying reproductive strategies (Smith et al.
2002
; Piriz et al.
2003
;
