Chapter 6
Seagrass Beds and Coastal Biogeochemistry
N ´
uria Marb `
a*
Grup d’Oceanografia Interdisciplinar, Institut Mediterrani d’Estudis Avan¸ cats (UIB-CSIC),
Miquel Marqu `
es 21, 07190 Esporles (Illes Balears), Spain
Marianne Holmer
Institute of Biology, University of Southern Denmark, Campusvej 55,
DK-5230 Odense M, Denmark; e-mail: holmer@biology.sdu.dk
Esperan¸ ca Gacia
Centre d’Estudis Avan¸ cats de Blanes (CSIC), Acc ´
es a la Cala Sant Francesc 14,
17300 Blanes (Girona), Spain; e-mail: gacia@ceab.csic.es
Christina Barr ´
on
Grup d’Oceanografia Interdisciplinar, Institut Mediterrani d’Estudis Avancats (UIB-CSIC),
Miquel Marqu `
es 21, 07190 Esporles (Illes Balears), Spain; e-mail: ieacbe@uib.es
I. Introduction
Seagrasses develop extensive beds at the interface
between the water column and sediment in tidal
or subtidal environments. The height of seagrass
canopy ranges from a few centimetres to more
than a meter (Koch et al., Chapter 8), and seagrass
rhizospheres may penetrate from centimetres (e.g.
Halophila sp; Duarte et al., 1998) to a few meters
(e.g. Posidonia oceanica; Mateo et al., 1997) into
the sediment, depending on the species. Seagrass
beds may support large above- and below-ground
biomasses (Fig. 1), and they rank amongst the
most productive marine primary producers (Duarte
and Chiscano, 1999; Mateo et al., Chapter 7). The
metabolic activities and the structure of seagrass
beds modify the physical and chemical conditions
of the water column and sediments of the areas
colonized. For instance, seagrass metabolism affects carbon and nutrient dynamics in coastal areas
(Mateo et al., Chapter 7; Romero et al., Chapter 9),
∗ Author for correspondence, email: naria.marb` a@uib.es
as well as oxygen concentration in the water column (Larkum et al., Chapter 14) and sediments
(Borum et al., Chapter 10). The structure of seagrass canopy, for instance, modifies water current
velocity and waves, enhancing sedimentation of suspended particles (Koch et al., Chapter 8), and preventing sediment resuspension (Gacia and Duarte,
2001). Similarly, the dense network of rhizomes and
roots effectively retains the sediments produced by,
and deposited in, seagrass rhizospheres.
The effects of seagrass beds on the physical and
chemical conditions of the areas colonized constrain benthic microbial communities, and, thus, the
processes involved in the mineralization of organic
matter and regeneration of nutrients in coastal areas. Seagrass beds, therefore, play an important engineering role (sensu Jones et al., 1997) in controlling coastal biogeochemistry. The input of organic matter and the accumulation of seagrass detritus in the sediments increase the amount of microbial substrates in the sediments (Gacia and Duarte,
2001), and, due to the relative refractory composition of seagrass detritus as a result of the high
135–157.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Seagrass Beds and Coastal Biogeochemistry
N ´
uria Marb `
a*
Grup d’Oceanografia Interdisciplinar, Institut Mediterrani d’Estudis Avan¸ cats (UIB-CSIC),
Miquel Marqu `
es 21, 07190 Esporles (Illes Balears), Spain
Marianne Holmer
Institute of Biology, University of Southern Denmark, Campusvej 55,
DK-5230 Odense M, Denmark; e-mail: holmer@biology.sdu.dk
Esperan¸ ca Gacia
Centre d’Estudis Avan¸ cats de Blanes (CSIC), Acc ´
es a la Cala Sant Francesc 14,
17300 Blanes (Girona), Spain; e-mail: gacia@ceab.csic.es
Christina Barr ´
on
Grup d’Oceanografia Interdisciplinar, Institut Mediterrani d’Estudis Avancats (UIB-CSIC),
Miquel Marqu `
es 21, 07190 Esporles (Illes Balears), Spain; e-mail: ieacbe@uib.es
I. Introduction
Seagrasses develop extensive beds at the interface
between the water column and sediment in tidal
or subtidal environments. The height of seagrass
canopy ranges from a few centimetres to more
than a meter (Koch et al., Chapter 8), and seagrass
rhizospheres may penetrate from centimetres (e.g.
Halophila sp; Duarte et al., 1998) to a few meters
(e.g. Posidonia oceanica; Mateo et al., 1997) into
the sediment, depending on the species. Seagrass
beds may support large above- and below-ground
biomasses (Fig. 1), and they rank amongst the
most productive marine primary producers (Duarte
and Chiscano, 1999; Mateo et al., Chapter 7). The
metabolic activities and the structure of seagrass
beds modify the physical and chemical conditions
of the water column and sediments of the areas
colonized. For instance, seagrass metabolism affects carbon and nutrient dynamics in coastal areas
(Mateo et al., Chapter 7; Romero et al., Chapter 9),
∗ Author for correspondence, email: naria.marb` a@uib.es
as well as oxygen concentration in the water column (Larkum et al., Chapter 14) and sediments
(Borum et al., Chapter 10). The structure of seagrass canopy, for instance, modifies water current
velocity and waves, enhancing sedimentation of suspended particles (Koch et al., Chapter 8), and preventing sediment resuspension (Gacia and Duarte,
2001). Similarly, the dense network of rhizomes and
roots effectively retains the sediments produced by,
and deposited in, seagrass rhizospheres.
The effects of seagrass beds on the physical and
chemical conditions of the areas colonized constrain benthic microbial communities, and, thus, the
processes involved in the mineralization of organic
matter and regeneration of nutrients in coastal areas. Seagrass beds, therefore, play an important engineering role (sensu Jones et al., 1997) in controlling coastal biogeochemistry. The input of organic matter and the accumulation of seagrass detritus in the sediments increase the amount of microbial substrates in the sediments (Gacia and Duarte,
2001), and, due to the relative refractory composition of seagrass detritus as a result of the high
135–157.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.