Chapter 18 The Biology of Thalassia
431
of the clones, spacing of clones in a meadow, consequences of clonal growth in acquisition of resources)
is also limited. An important reason for this our limited knowledge of population dynamics (at a higher
level than the shoots) and clonal biology are the high
degree of entanglement of rhizomes that makes it logistically almost impossible to tell individuals other
than the ramets (shoots) apart. It is hoped that with
the coming of high-resolution genetic markers will
greatly increasing our insights in this field.
Human development of the coastal zones not only
causes a decrease in total extend of seagrass meadows, but also cause fragmentation of these naturally extensive seagrass beds, and the formation of
edges and remnant patches through fragmentation
is considered to be critical in terms of conservation (Wilcox and Murphy, 1985). Fragmentation of
beds is thought to cause impoverishment of faunal diversity and distribution, although Bell et al.
(2002) found few differences between areas with and
without boat propeller scars. Uhrin and Holmqvist
(2003), on the contrary, reported lower faunal abundance and species richness in areas denuded of seagrasses by propellers. Habitat fragmentation may
also have consequences for nutrient retention. There
are clear indications that in oligotrophic areas, nutrient conservation for Thalassia depends on the
meadow as a whole (section 3), thus division into
smaller patches may have serious consequences for
the persistence of this genus in these environments.
On a larger scale, habitat fragmentation may increase
genetic drift in isolated populations, resulting in a decrease in genetic diversity, but knowledge concerning genetic diversity of Thalassia is just emerging,
and little is known about their capacity of dispersal
and (re-)colonization of distant perturbed areas. Future research into these and other basic aspects of
seagrass biology are urgently required before more
seagrass habitat is lost along the tropical coasts of
the Atlantic and Indo-Pacific.
Acknowledgments
Critical revision by M. Durako and another
anonymous reviewer considerable improved the
manuscript. The first author is grateful to M. Hutchings and C. den Hartog for useful comments on various sections of the text. This is NIOO publication
number 3309.
References
Agawin NSR and Duarte CM (2002) Evidence of direct particle
trapping by a tropical seagrass meadow. Estuaries 25: 1205–
1209
Agawin NSR, Duarte CM and Fortes MD (1996) Nutrient limitation of Philippine seagrasses (Cape Bolinao, NW Philippines):
In situ experimental evidence. Mar Ecol Prog Ser 138: 233–
243
Aliaume C, Louis M and Lasserre G (1993) Ecosystem of Thalassia testudinum beds in Guadeloupe (French
Antilles)—relations between fish recruitment and habitat.
Acta Oecologia—Int J Ecol 14: 627–641
Almasi MN, Hoskin CM, Reed JK and Mijo J (1987) Effects
of natural and artificial Thalassia on rates of sedimentation. J
Sedimentol Petrol 57: 901–906
Alpert P and Mooney HA (1986) Resource sharing among ramets
in the clonal herb, Fragaria chiloensis. Oecologia 70: 227–233
Arrivillaga A and Baltz DM (1999) Comparison of fishes
and macroinvertebrates on seagrass and bare-sand sites on
Guatemala’s Atlantic coast, Bull Mar Sci 65: 301–319
Bach SD (1979) Standing crop, growth and production of calcareous siphonales (Chlorophyta) in a South Florida Lagoon,
Bull Mar Sci 29: 191–201
Ballantine DL, Aponte NE and Holmqvist JG (1994) Multispecies algal balls and potentially imprisoned fauna: An unusual benthic assemblage. Aquat Bot 48: 167–174
Ballantine DL and Humm HJ (1975) Benthic algae of the Anclote Estuary I. Epiphytes of seagrass leaves. Fla Sci 38: 150–
162
Barber BJ and Behrens PJ (1985) Effects of elevated temperature
on seasonal in situ eaf productivity of Thalassia testudinum
Banks ex K¨ onig and Syringodium filiforme K¨ utzing. Aquat
Bot 22: 61–69
Beddingfield SD and McClintock JB (2000) Demographic characteristics of Lytechinus variegatus (Echinoidea: Echinodermata) from three habitats in a North Florida Bay, Gulf of
Mexico. Mar Ecol—Pubblicazioni della Stazione Zoologica
di Napoli I 21: 17–40
Bell SS and Hall MO (1995) Drift macroalgal abundance in seagrass beds: Investigating large-scale associations with physical
and biotic attributes. Mar Ecol Prog Ser 147: 277–283
Bell SS, Brokks RA, Robbins BD, Fonseca MS and Hall MO
(2002) Assessing the impact of boat propellor scars on fish
and shrimp utilization of seagrass beds. Ecolog Appl 12: 206–
217
Birch WR and Birch M (1984) Succession and pattern of tropical
intertidal seagrasses in Cockle Bay, Queensland, Australia: A
decade of observations. Aquat Bot 19: 343–367
Bologna PAX and Heck KL (1999) Differential predation and
growth rates of bay scallops within a seagrass habitat. J Exp
Mar Biol Ecol 239: 299–314
Bologna PAX and Heck KL (2000) Impacts of seagrass habitat
architecture on bivalve settlement. Estuaries 23: 449–457
Bosence D (1989) Biogenic carbonate production in Florida Bay.
Bull Mar Sci 44: 419–433
Brouns JJWM (1985) A comparison of the annual production
and biomass in three monospecific stands of the seagrass
Thalassia hemprichii (Ehrenb.) Aschers. Aquat Bot 23: 149–
175
431
of the clones, spacing of clones in a meadow, consequences of clonal growth in acquisition of resources)
is also limited. An important reason for this our limited knowledge of population dynamics (at a higher
level than the shoots) and clonal biology are the high
degree of entanglement of rhizomes that makes it logistically almost impossible to tell individuals other
than the ramets (shoots) apart. It is hoped that with
the coming of high-resolution genetic markers will
greatly increasing our insights in this field.
Human development of the coastal zones not only
causes a decrease in total extend of seagrass meadows, but also cause fragmentation of these naturally extensive seagrass beds, and the formation of
edges and remnant patches through fragmentation
is considered to be critical in terms of conservation (Wilcox and Murphy, 1985). Fragmentation of
beds is thought to cause impoverishment of faunal diversity and distribution, although Bell et al.
(2002) found few differences between areas with and
without boat propeller scars. Uhrin and Holmqvist
(2003), on the contrary, reported lower faunal abundance and species richness in areas denuded of seagrasses by propellers. Habitat fragmentation may
also have consequences for nutrient retention. There
are clear indications that in oligotrophic areas, nutrient conservation for Thalassia depends on the
meadow as a whole (section 3), thus division into
smaller patches may have serious consequences for
the persistence of this genus in these environments.
On a larger scale, habitat fragmentation may increase
genetic drift in isolated populations, resulting in a decrease in genetic diversity, but knowledge concerning genetic diversity of Thalassia is just emerging,
and little is known about their capacity of dispersal
and (re-)colonization of distant perturbed areas. Future research into these and other basic aspects of
seagrass biology are urgently required before more
seagrass habitat is lost along the tropical coasts of
the Atlantic and Indo-Pacific.
Acknowledgments
Critical revision by M. Durako and another
anonymous reviewer considerable improved the
manuscript. The first author is grateful to M. Hutchings and C. den Hartog for useful comments on various sections of the text. This is NIOO publication
number 3309.
References
Agawin NSR and Duarte CM (2002) Evidence of direct particle
trapping by a tropical seagrass meadow. Estuaries 25: 1205–
1209
Agawin NSR, Duarte CM and Fortes MD (1996) Nutrient limitation of Philippine seagrasses (Cape Bolinao, NW Philippines):
In situ experimental evidence. Mar Ecol Prog Ser 138: 233–
243
Aliaume C, Louis M and Lasserre G (1993) Ecosystem of Thalassia testudinum beds in Guadeloupe (French
Antilles)—relations between fish recruitment and habitat.
Acta Oecologia—Int J Ecol 14: 627–641
Almasi MN, Hoskin CM, Reed JK and Mijo J (1987) Effects
of natural and artificial Thalassia on rates of sedimentation. J
Sedimentol Petrol 57: 901–906
Alpert P and Mooney HA (1986) Resource sharing among ramets
in the clonal herb, Fragaria chiloensis. Oecologia 70: 227–233
Arrivillaga A and Baltz DM (1999) Comparison of fishes
and macroinvertebrates on seagrass and bare-sand sites on
Guatemala’s Atlantic coast, Bull Mar Sci 65: 301–319
Bach SD (1979) Standing crop, growth and production of calcareous siphonales (Chlorophyta) in a South Florida Lagoon,
Bull Mar Sci 29: 191–201
Ballantine DL, Aponte NE and Holmqvist JG (1994) Multispecies algal balls and potentially imprisoned fauna: An unusual benthic assemblage. Aquat Bot 48: 167–174
Ballantine DL and Humm HJ (1975) Benthic algae of the Anclote Estuary I. Epiphytes of seagrass leaves. Fla Sci 38: 150–
162
Barber BJ and Behrens PJ (1985) Effects of elevated temperature
on seasonal in situ eaf productivity of Thalassia testudinum
Banks ex K¨ onig and Syringodium filiforme K¨ utzing. Aquat
Bot 22: 61–69
Beddingfield SD and McClintock JB (2000) Demographic characteristics of Lytechinus variegatus (Echinoidea: Echinodermata) from three habitats in a North Florida Bay, Gulf of
Mexico. Mar Ecol—Pubblicazioni della Stazione Zoologica
di Napoli I 21: 17–40
Bell SS and Hall MO (1995) Drift macroalgal abundance in seagrass beds: Investigating large-scale associations with physical
and biotic attributes. Mar Ecol Prog Ser 147: 277–283
Bell SS, Brokks RA, Robbins BD, Fonseca MS and Hall MO
(2002) Assessing the impact of boat propellor scars on fish
and shrimp utilization of seagrass beds. Ecolog Appl 12: 206–
217
Birch WR and Birch M (1984) Succession and pattern of tropical
intertidal seagrasses in Cockle Bay, Queensland, Australia: A
decade of observations. Aquat Bot 19: 343–367
Bologna PAX and Heck KL (1999) Differential predation and
growth rates of bay scallops within a seagrass habitat. J Exp
Mar Biol Ecol 239: 299–314
Bologna PAX and Heck KL (2000) Impacts of seagrass habitat
architecture on bivalve settlement. Estuaries 23: 449–457
Bosence D (1989) Biogenic carbonate production in Florida Bay.
Bull Mar Sci 44: 419–433
Brouns JJWM (1985) A comparison of the annual production
and biomass in three monospecific stands of the seagrass
Thalassia hemprichii (Ehrenb.) Aschers. Aquat Bot 23: 149–
175