Biology Reference
In-Depth Information
habitat quality. Most large occurrences of algal blooms have been associated with
increased nutrient enrichment, primarily nitrogen, although phosphorus may also
play a role (Howarth
2008
; Teichberg et al.
2010
). Here, we focus primarily on
occurrences of macroalgal blooms reported worldwide that are linked to coastal
eutrophication. Ecophysiological uptake and utilization mechanisms of nutrients,
nitrogen and phosphorus limitation, assimilation of carbon, and the role of nutrient
availability in stimulating macroalgal growth rates are reviewed in the Chap.
4
by Gordillo.
In the USA, approximately 65% of estuaries surveyed showed moderate to high
levels of eutrophic conditions, influenced primarily by land-based nutrient loads
from human activities (Bricker et al.
2008
). In many of these estuaries, extensive
chlorophyte and rhodophyte blooms are prevalent and have caused anoxic
conditions (Bricker et al.
2008
) and changes in the benthic community (Table
21.1
).
Waquoit Bay, in Cape Cod, Massachusetts, serves as a good example of how
increased urbanization has led to drastic changes in the marine community structure
over the past six decades (Valiela et al.
1992
,
1997
; Hauxwell et al.
1998
,
2001
; Fox
et al.
2008
). Macroalgal blooms of
Cladophora
,
Gracilaria
, and
Ulva
spp. have
been directly linked to increased nitrogen loading rates in the subestuaries of
Waquoit Bay predominantly due to increases in wastewater nitrate from septic
systems that enters the estuary via groundwater (Valiela
2006
; Fox et al.
2008
;
Fig.
21.1
). Along the Florida coast, blooms of green macroalgae, including invasive
species of
Codium
and
Caulerpa
, and drift red macroalgae have also been linked to
increasing in nutrient inputs from sewage, shown through their high tissue N and P
content and heavier nitrogen isotopic signatures that reflect that of wastewater
nitrogen (Lapointe et al.
2005a
,
b
; Lapointe and Bedford
2007
,
2010
).
Outside of North America, frequency of macroalgal blooms driven by high
nutrient loads has also been reported (Table
21.1
). Most sites where macroalgal
blooms reach a remarkably high standing crop are locations where waters are
enriched with nutrients as a result of urban growth in surrounding areas.
A 20-year study in Peel Harvey Estuary, Australia, showed how large blooms of
Cladophora
,
Ulva
, and
Chaetomorpha
spp. have been caused by high nutrient
loading, with interannual differences in biomass associated with nutrient and light
conditions (Lavery et al.
1991
). In San Antonio Bay, Argentina, high wastewater
nitrogen and phosphorus inputs have been linked to high growth rates and biomass
of
Ulva lactuca
that forms extensive blooms in the main channel of the bay
(Teichberg et al.
2010
; Martinetto et al.
2011
; Fig.
21.1
). Other sites known for
macroalgal blooms that have been linked to coastal pollution include Venice
Lagoon, Italy and Mondego Estuary, Portugal (Table
21.1
, Fig.
21.1
). In these
sites,
Ulva
blooms persist under high nutrient loads (Sfriso et al.
1992
; Martins et al.
2001
; Teichberg et al.
2010
).
