10 The Leaf Canopy of Seagrass Beds: Faunal
Community Structure and Function in a Salinity
Gradient Along the Swedish Coast
S.P. BADEN and C. BOSTROM
10.1 Introduction
10.1.1 Zostera marina 1.
The distribution of eelgrass (Zostera marina, hereafter Zostera) is mainly
concentrated along temperate coasts of the Northern Pacific and the Atlantic
oceans, and it is the only seagrass extending into Arctic areas (71°N) (Den
Hartog 1970). Eelgrass commonly inhabits muddy and sandy bottoms and
forms continuous meadows or patchy beds in non-tidal, intertidal as well as
subtidal areas.
Zostera is considered euryhaline and tolerates salinities from about 32 psu
to 5 psu (Luther 1951; Mathiesen and Nielsen 1956). In contrast to salinity
tolerance, eelgrass has relatively narrow temperature requirements as suggested many years ago by Setchell (1929). However, seagrasses may form
temperature-adapted populations and seagrass flowering has been observed
to occur below lOOC (Phillips and Menez 1988). Eelgrass meadows are generally more luxuriant in sheltered areas, the main habitats for Zostera on the
Swedish west coast, while it mainly occurs at exposed sites along the Swedish
east coast and in Finland (Baltic Sea). Leaf area, shoot length and leaf width
increase with higher levels of sediment ammonium concentrations, while
shoot density and abundance of flowering plants show an inverse relationship
to interstitial ammonium content (Den Hartog 1970; Short 1983a,b). However,
recent experimental work in the western Baltic Sea (Kiel area) implies that
eelgrass at exposed, sandy sites is not nutrient-limited, and that the positive
effects of shoot density (Worm and Reusch 2000) or fertilization by mussels
(Reusch et al. 1994) are more important than sediment nutrient availability
for plant growth and bed expansion. In regions with low environmental stress
in terms of salinity, temperature, tidal range and wave exposure, vegetative
propagation is important whereas seedling recruitment is more important in
extreme environments where disturbances occur (Phillips and Menez 1988).
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
Community Structure and Function in a Salinity
Gradient Along the Swedish Coast
S.P. BADEN and C. BOSTROM
10.1 Introduction
10.1.1 Zostera marina 1.
The distribution of eelgrass (Zostera marina, hereafter Zostera) is mainly
concentrated along temperate coasts of the Northern Pacific and the Atlantic
oceans, and it is the only seagrass extending into Arctic areas (71°N) (Den
Hartog 1970). Eelgrass commonly inhabits muddy and sandy bottoms and
forms continuous meadows or patchy beds in non-tidal, intertidal as well as
subtidal areas.
Zostera is considered euryhaline and tolerates salinities from about 32 psu
to 5 psu (Luther 1951; Mathiesen and Nielsen 1956). In contrast to salinity
tolerance, eelgrass has relatively narrow temperature requirements as suggested many years ago by Setchell (1929). However, seagrasses may form
temperature-adapted populations and seagrass flowering has been observed
to occur below lOOC (Phillips and Menez 1988). Eelgrass meadows are generally more luxuriant in sheltered areas, the main habitats for Zostera on the
Swedish west coast, while it mainly occurs at exposed sites along the Swedish
east coast and in Finland (Baltic Sea). Leaf area, shoot length and leaf width
increase with higher levels of sediment ammonium concentrations, while
shoot density and abundance of flowering plants show an inverse relationship
to interstitial ammonium content (Den Hartog 1970; Short 1983a,b). However,
recent experimental work in the western Baltic Sea (Kiel area) implies that
eelgrass at exposed, sandy sites is not nutrient-limited, and that the positive
effects of shoot density (Worm and Reusch 2000) or fertilization by mussels
(Reusch et al. 1994) are more important than sediment nutrient availability
for plant growth and bed expansion. In regions with low environmental stress
in terms of salinity, temperature, tidal range and wave exposure, vegetative
propagation is important whereas seedling recruitment is more important in
extreme environments where disturbances occur (Phillips and Menez 1988).
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001