Biology Reference
In-Depth Information
between hosts and colonizers that were hardly investigated. These interactions have
positive effects, such as providing additional ecological niches, food and protective
habitat for animals (Pavia et al.
1999
; Karez et al.
2000
; Viejo and
˚
berg
2003
;
Bittick et al.
2010
), as well as negative effects, such as competition with the host for
light and nutrients (D'Antonio
1985
; Cebrian et al.
1999
; Honkanen and
Jormalainen
2005
); increasing drag (D'Antonio
1985
; Hemmi et al.
2005
); and
favoring the attraction of grazers to the host alga (Bernstein and Jung
1979
; Wahl
and Hay
1995
; Wahl et al.
1997
). During the last decades, sustained nutrient
enrichment from land-based activities resulted in increased biomass of attached
epiphytes in many ecosystems (Ronnberg and Bonsdorff
2004
; Russell et al.
2005
,
see also Chap.
21
by Teichberg et al.) and consequences of global warming may
also strongly affect these biotic interactions (Eggert et al.
2010
). In addition, closed
associations between seaweeds are involved in human affairs when they impact the
mariculture or the harvesting of wild populations of economically important
seaweeds (Friedlander
1992
; Critchley et al.
2004
; Hurtado et al.
2006
; Vairappan
2006
; Gachon et al.
2010
, see also Chap.
22
by Buchholz et al.) or when opportu-
nistic species foul artificial substrates (Callow and Callow
2011
).
This chapter attempts to summarize a part of the literature available on the
biology and ecology of such close associations. The particular focus will be on
cross-talk mechanisms involved in host specificity, the role of bacterial biofilms in
mediating some interactions, as well as the role of host chemical defenses that
impact the diversity of associations through allelopathic interactions. In the context
of coastal eutrophication and climate change, these subtle relationships between
seaweeds and colonizers at the community level and in human affairs, including
algal mariculture or the search for environment-friendly antifouling and antimicro-
bial strategies, will be an important and emerging field of research.
11.2 Ecology and Biology of Close Biotic Interactions
of Seaweeds
11.2.1 Epiphytes
Algal epiphytes are ubiquitous and play major ecological functions in coastal
benthic communities. Therefore, the available literature on algal epiphytes is
abundant but also very diverse with a lack of a comprehensive review. Algal
epiphytes have been studied mainly in terms of species diversity and community
ecology. However, in comparison with the abundant literature available on
seagrasses, considerably less work has concerned the distribution and effects of
epiphytic populations on macroalgal hosts (D'Antonio
1985
; Rindi and Guiry
2004
). The composition of epiphytic assemblages on macrophyte host surfaces
displays strong seasonal and spatial variations (Markham
1969
; Whittick
1983
;
Arrontes
1990
; Rindi and Guiry
2004
; Leonardi et al.
2006
). Old or damaged
