Chapter 19 Epiphytes of Seagrasses
447
differences in the abundance of different functional
groups, and these patterns mimicked species-level
patterns.
Similarly, Bandeira (2002) showed significant
between-site differences in the assemblages of epiphytes on Thalassodendron ciliatum stems; in this
case only articulated coralline algae occurred at a
sandy site but elsewhere articulated coralline, encrusting, corticated filamentous, corticated foliose,
and leathery algae were present.
Few studies have examined the variability in composition of epiphytes across spatial scales larger than
within plants, despite recognition that the spatial
scale is likely to influence the difference between
assemblages (Fonseca, 1996). Most information on
larger-scale spatial variability has been obtained
incidentally, while studying the effects of nutrients or other environmental factors (e.g. Frankovich
and Fourquean, 1997; Kendrick and Burt, 1997;
Pinckney and Micheli, 1998). However, several recent studies have explicitly examined spatial variation at different scales (Kendrick and Burt, 1997;
Vanderklift and Lavery, 2000; Lavery and Vanderklift, 2002; Saunders et al., 2003). These studies generally show an increase in dissimilarity of epiphyte
assemblages with increasing distance apart. Significant differences occur in assemblages on P. sinuosa separated by kilometers on the same shallow
coastal bank and across a gradient of wave exposure
(Kendrick and Burt, 1997); filamentous browns and
reds and cyanobacteria dominated the more inshore
site, while articulated and encrusting coralline algae
dominated the offshore site. Further, within the filamentous rhodophytes that occurred at each site there
were differences; the inshore site was dominated by
Rhodomelaceae and the offshore site by Ceramiaceae. Frankovich and Fourqurean (1997) examined epiphyte assemblages across a nutrient gradient
and found compositional shifts, though these tended
to occur rapidly and close to the nutrient source.
Bandeira (2002) also observed a great difference in
epiphytes in Thalassodendron ciliatum growing on
either rocky substrata or sandy substrata at Ithaca
Island, Mozambique. He found that the communities at the rocky sites had a diverse epiphytic flora,
whereas at the sandy site epiphytes were restricted
almost completely to the coralline Jania adhaerens,
growing on the stems of the seagrass.
A small number of studies have attempted to look
at spatial patterns in epiphytes that are independent
of obvious environmental gradients. Trends across
different species appear similar but with some subtle differences. In Z. marina, a seagrass of relatively
simple structural complexity, epiphyte assemblages
showed no differences in composition or abundance
at the scales of less than 10 m, but highly significant differences at the kilometer scale (Saunders
et al., 2003). Similar observations were made by
Cullinane et al. (1985) also working on Z. marina;
differences in composition were found at the scale
of tens of kilometers, with only one species common
to six sites separated at this scale. The composition
of epiphytes has also been examined on the structurally complex seagrasses Amphibolis griffithii and
Posidonia coriacea at scales of tens, hundreds, and
thousands of meters (Vanderklift and Lavery, 2000;
Lavery and Vanderklift, 2002). As with Z. marina,
there were no differences at very small scales (1 m
or less) but, in contrast, differences were apparent at
scales as low as one to tens of meters. In P. coriacea,
where leaf turnover is in the order of 50–100 days,
there was a linear increase in dissimilarity of assemblages with distance apart but in A. griffithii, with
long-lived stems up to 2 years old, the differences in
assemblages increased almost exponentially with increasing distance apart. This was attributed to interactions of seagrass and algal life-history timescales.
These studies of structurally diverse seagrass species
indicate that assemblage structure of epiphytes are
likely to be variable between sites separated by as little as tens of meters and that these differences will be
more pronounced as the spatial scale increases. Furthermore, it appears that these differences hold not
only at species level but also at the functional group
level (Vanderklift and Lavery, 2000; Saunders et al.,
2003; Fig. 3). This implies that the differences have
the potential to affect the ecological function of the
epiphyte assemblages, and therefore the functional
attributes of the seagrass habitats separated at these
scales.
Epiphyte community structure and biomass also
vary over depth for a wide range of seagrasses.
Meadows of the Mediterranean seagrass P. oceanica supported a more diverse assemblage at shallow
sites, but by 30 m depth there were no epiphytic
algae. The relative abundance of rhodophytes increased with depth while phaeophyte abundance decreased (Cinelli et al., 1984; Lepoint et al., 1999).
These observations both confirm and contrast those
of Rindi et al. (1999) who compared the epiphyte
composition of the short-lived Mediterranean seagrass Halophila stipulacea at shallow (5 m) and deep
447
differences in the abundance of different functional
groups, and these patterns mimicked species-level
patterns.
Similarly, Bandeira (2002) showed significant
between-site differences in the assemblages of epiphytes on Thalassodendron ciliatum stems; in this
case only articulated coralline algae occurred at a
sandy site but elsewhere articulated coralline, encrusting, corticated filamentous, corticated foliose,
and leathery algae were present.
Few studies have examined the variability in composition of epiphytes across spatial scales larger than
within plants, despite recognition that the spatial
scale is likely to influence the difference between
assemblages (Fonseca, 1996). Most information on
larger-scale spatial variability has been obtained
incidentally, while studying the effects of nutrients or other environmental factors (e.g. Frankovich
and Fourquean, 1997; Kendrick and Burt, 1997;
Pinckney and Micheli, 1998). However, several recent studies have explicitly examined spatial variation at different scales (Kendrick and Burt, 1997;
Vanderklift and Lavery, 2000; Lavery and Vanderklift, 2002; Saunders et al., 2003). These studies generally show an increase in dissimilarity of epiphyte
assemblages with increasing distance apart. Significant differences occur in assemblages on P. sinuosa separated by kilometers on the same shallow
coastal bank and across a gradient of wave exposure
(Kendrick and Burt, 1997); filamentous browns and
reds and cyanobacteria dominated the more inshore
site, while articulated and encrusting coralline algae
dominated the offshore site. Further, within the filamentous rhodophytes that occurred at each site there
were differences; the inshore site was dominated by
Rhodomelaceae and the offshore site by Ceramiaceae. Frankovich and Fourqurean (1997) examined epiphyte assemblages across a nutrient gradient
and found compositional shifts, though these tended
to occur rapidly and close to the nutrient source.
Bandeira (2002) also observed a great difference in
epiphytes in Thalassodendron ciliatum growing on
either rocky substrata or sandy substrata at Ithaca
Island, Mozambique. He found that the communities at the rocky sites had a diverse epiphytic flora,
whereas at the sandy site epiphytes were restricted
almost completely to the coralline Jania adhaerens,
growing on the stems of the seagrass.
A small number of studies have attempted to look
at spatial patterns in epiphytes that are independent
of obvious environmental gradients. Trends across
different species appear similar but with some subtle differences. In Z. marina, a seagrass of relatively
simple structural complexity, epiphyte assemblages
showed no differences in composition or abundance
at the scales of less than 10 m, but highly significant differences at the kilometer scale (Saunders
et al., 2003). Similar observations were made by
Cullinane et al. (1985) also working on Z. marina;
differences in composition were found at the scale
of tens of kilometers, with only one species common
to six sites separated at this scale. The composition
of epiphytes has also been examined on the structurally complex seagrasses Amphibolis griffithii and
Posidonia coriacea at scales of tens, hundreds, and
thousands of meters (Vanderklift and Lavery, 2000;
Lavery and Vanderklift, 2002). As with Z. marina,
there were no differences at very small scales (1 m
or less) but, in contrast, differences were apparent at
scales as low as one to tens of meters. In P. coriacea,
where leaf turnover is in the order of 50–100 days,
there was a linear increase in dissimilarity of assemblages with distance apart but in A. griffithii, with
long-lived stems up to 2 years old, the differences in
assemblages increased almost exponentially with increasing distance apart. This was attributed to interactions of seagrass and algal life-history timescales.
These studies of structurally diverse seagrass species
indicate that assemblage structure of epiphytes are
likely to be variable between sites separated by as little as tens of meters and that these differences will be
more pronounced as the spatial scale increases. Furthermore, it appears that these differences hold not
only at species level but also at the functional group
level (Vanderklift and Lavery, 2000; Saunders et al.,
2003; Fig. 3). This implies that the differences have
the potential to affect the ecological function of the
epiphyte assemblages, and therefore the functional
attributes of the seagrass habitats separated at these
scales.
Epiphyte community structure and biomass also
vary over depth for a wide range of seagrasses.
Meadows of the Mediterranean seagrass P. oceanica supported a more diverse assemblage at shallow
sites, but by 30 m depth there were no epiphytic
algae. The relative abundance of rhodophytes increased with depth while phaeophyte abundance decreased (Cinelli et al., 1984; Lepoint et al., 1999).
These observations both confirm and contrast those
of Rindi et al. (1999) who compared the epiphyte
composition of the short-lived Mediterranean seagrass Halophila stipulacea at shallow (5 m) and deep