The Leaf Canopy of Seagrass Beds: Faunal Community in a Salinity Gradient
225
et al. (1977); Asmus et al. (1980); Bostrom (1996) and Bostrom and Bonsdorff
(1997). Lappalainen et al. (1977) carried out studies on the Tvarminne area
(SW Finland, northern Baltic Sea), but they did not separate the Zostera
infauna from the leaf fauna.
Abundance and biomass of leaf fauna are not linearly correlated with the
standing stock or leaf area of Zostera, as recorded elsewhere in fresh water by
Cooper and Crowder (1979), and in marine areas by Orth et al. (1984) and
Mattila et al. (1999). The standing stock and leaf area at localities 1-7 are
relatively similar (Fig. 10.3), whereas the abundance and biomass for these
localities vary quite remarkably (Fig. 10.4). However, moving into the Baltic all
these biological parameters are reduced.
Zostera localities with high exposure were mainly found in the Baltic (see
Sect. 10.2). With increasing exposure the Zostera beds change from detritus
sinks to detritus sources (Fonseca et al. 1983; Fonseca and Fischer 1986;
Bostrom and Bonsdorff 2000). Hence, due to such differing current regimes
(Gambi et al.1990), the amounts of organic matter available as food resources
or building materials (amphipod tubes) for the leaf fauna differ among the
regions studied.
Consequently, dividing the leaf fauna into feeding groups (Fig. 10.5), the
detritivores (Erichtonius difformis and Corophium insidiosum) and suspension feeders (juvenile Mytilus attached to the leaves) dominate in the
detritus-driven systems (localities 1-5) and, from localities 4-9, grazers (isopods, gammarids) take over successively (Figs. 10.5, 10.6). Among the meiofauna, copepodes (harpacticoids) and nematodes (dominated by Southermia
zostera on the west coast) probably play an important role as detritivores. The
leaf fouling on the west coast consists of detritus, filamentous algae and fauna
100
~
., u c:
'"
"0
c:
:l 50
~
"
"
.:::
E
<;
00:
0
o Gmzcrs • Dclritivores 0 Suspension feeders
2
3
4
5
Localit ie
6
7
9
Fig. 10.5. Composition of Zostera marina leaf fauna at localities 1-9 based on feeding
mode (grazers, detritivores or suspension feeders)
225
et al. (1977); Asmus et al. (1980); Bostrom (1996) and Bostrom and Bonsdorff
(1997). Lappalainen et al. (1977) carried out studies on the Tvarminne area
(SW Finland, northern Baltic Sea), but they did not separate the Zostera
infauna from the leaf fauna.
Abundance and biomass of leaf fauna are not linearly correlated with the
standing stock or leaf area of Zostera, as recorded elsewhere in fresh water by
Cooper and Crowder (1979), and in marine areas by Orth et al. (1984) and
Mattila et al. (1999). The standing stock and leaf area at localities 1-7 are
relatively similar (Fig. 10.3), whereas the abundance and biomass for these
localities vary quite remarkably (Fig. 10.4). However, moving into the Baltic all
these biological parameters are reduced.
Zostera localities with high exposure were mainly found in the Baltic (see
Sect. 10.2). With increasing exposure the Zostera beds change from detritus
sinks to detritus sources (Fonseca et al. 1983; Fonseca and Fischer 1986;
Bostrom and Bonsdorff 2000). Hence, due to such differing current regimes
(Gambi et al.1990), the amounts of organic matter available as food resources
or building materials (amphipod tubes) for the leaf fauna differ among the
regions studied.
Consequently, dividing the leaf fauna into feeding groups (Fig. 10.5), the
detritivores (Erichtonius difformis and Corophium insidiosum) and suspension feeders (juvenile Mytilus attached to the leaves) dominate in the
detritus-driven systems (localities 1-5) and, from localities 4-9, grazers (isopods, gammarids) take over successively (Figs. 10.5, 10.6). Among the meiofauna, copepodes (harpacticoids) and nematodes (dominated by Southermia
zostera on the west coast) probably play an important role as detritivores. The
leaf fouling on the west coast consists of detritus, filamentous algae and fauna
100
~
., u c:
'"
"0
c:
:l 50
~
"
"
.:::
E
<;
00:
0
o Gmzcrs • Dclritivores 0 Suspension feeders
2
3
4
5
Localit ie
6
7
9
Fig. 10.5. Composition of Zostera marina leaf fauna at localities 1-9 based on feeding
mode (grazers, detritivores or suspension feeders)