214
E. W. Koch, J. D. Ackerman, J. Verduin and M. van Keulen
Fig. 12. Complex seagrass landscape due to the presence of sand waves (arrow) in a Zostera marina bed at Horn Harbor, Chesapeake
Bay, USA. Photo: R.J. Orth.
The disturbances that lead to patchiness in seagrass landscapes range in scale from the complete
but local destruction of seagrass ecosystems (Dan
et al., 1998) to the creation of smaller (10’s of meters) unvegetated depressions in continuous meadows, termed “blowouts” (Patriquin, 1975; see review
in Short and Wyllie-Echeverria, 1996; Fonseca and
Bell, 1998). The magnitude and frequency of disturbances is what determines the degree of patchiness of a seagrass meadow (Fonseca et al., 1983;
Fonseca and Bell, 1998; Hemminga and Duarte,
2000). It can therefore be assumed that more extreme events would result in erosion and complete
or partial loss of seagrasses (with little recovery),
whereas periods of reduced disturbance may result
in coalescence of the patches and the formation of
more continuous meadows (Fonseca et al., 1983;
Kirkman and Kirkman, 2000). This concurs with numerous reports of widespread loss of meadows as a
result of hurricanes and cyclones (Birch and Birch,
1984; Williams, 1988; Rodriguez et al., 1994; Preen
et al., 1995; Moncreiff et al., 1999; Whitfield et al.,
2002), and the extensive colonization of seagrasses
(pioneering or climax species) during periods of reduced disturbance (Kirkman, 1985; Kendrick et al.,
2000). Note that some studies report no damage to
seagrasses after the passage of hurricanes (Thomas
et al., 1961; Tilmant et al., 1994; Dawes et al., 1995).
In areas with continuous high wave energy, seagrass ecosystems can be: (i) non-existent (Dan et al.,
E. W. Koch, J. D. Ackerman, J. Verduin and M. van Keulen
Fig. 12. Complex seagrass landscape due to the presence of sand waves (arrow) in a Zostera marina bed at Horn Harbor, Chesapeake
Bay, USA. Photo: R.J. Orth.
The disturbances that lead to patchiness in seagrass landscapes range in scale from the complete
but local destruction of seagrass ecosystems (Dan
et al., 1998) to the creation of smaller (10’s of meters) unvegetated depressions in continuous meadows, termed “blowouts” (Patriquin, 1975; see review
in Short and Wyllie-Echeverria, 1996; Fonseca and
Bell, 1998). The magnitude and frequency of disturbances is what determines the degree of patchiness of a seagrass meadow (Fonseca et al., 1983;
Fonseca and Bell, 1998; Hemminga and Duarte,
2000). It can therefore be assumed that more extreme events would result in erosion and complete
or partial loss of seagrasses (with little recovery),
whereas periods of reduced disturbance may result
in coalescence of the patches and the formation of
more continuous meadows (Fonseca et al., 1983;
Kirkman and Kirkman, 2000). This concurs with numerous reports of widespread loss of meadows as a
result of hurricanes and cyclones (Birch and Birch,
1984; Williams, 1988; Rodriguez et al., 1994; Preen
et al., 1995; Moncreiff et al., 1999; Whitfield et al.,
2002), and the extensive colonization of seagrasses
(pioneering or climax species) during periods of reduced disturbance (Kirkman, 1985; Kendrick et al.,
2000). Note that some studies report no damage to
seagrasses after the passage of hurricanes (Thomas
et al., 1961; Tilmant et al., 1994; Dawes et al., 1995).
In areas with continuous high wave energy, seagrass ecosystems can be: (i) non-existent (Dan et al.,