SOFT-BOTTOM NEAR-SHORE ECOSYSTEMS

Seagrass–sediment interactions, positive feedbacks

and critical thresholds for occurrence: a review

W. F. de Boer

Springer Science+Business Media B.V. 2007

Abstract This literature review summarizes the

limiting factors for seagrass occurrence, and the

effect positive feedbacks in seagrass systems have

on these threshold levels. Minimum water depth

is mainly determined by wave orbital velocity,

tide and wave energy; and maximum depth by

light availability. Besides these, other limiting

factors occur, such as an upper current velocity

threshold, above which seagrasses are eroded, or

a lower water current velocity threshold below

which carbon exchange is limiting. In some

locations organic matter content, sulphide concentration or nutrient availability are limiting. Nlimitation is mainly reported from temperate

terrigenous sediments, and P-limitation from

tropical carbonate sediments. However, limiting

factors sometimes change over the year, switching

from light limiting to N- or P-limiting, and show

at times regional variation. The effect seagrasses

have on current reduction, trapping sediment and

decreasing resuspension can lead to several

changes in both the sediment and the water

column. In the sediment, an increase in nutrient

availability has been reported, and increases in

organic matter, sediment height increases, and

burial of the seagrasses. In the water column the

effect is a reduction of the turbidity through a

decrease of the sediment load, decreasing the

attenuation coefficient, thereby increasing light

availability. Due to the large effect light availability has on seagrass occurrence, the effect of an

improvement of the light conditions by a reduction of the turbidity by seagrasses is probably the

most important positive feedback in seagrass

systems. The latter effect should therefore be

incorporated in models that try to understand or

predict seagrass changes. Generalization are

difficult due a lack of studies that try to find

relationships between seagrass architecture and

sediment trapping (studying both turbidity reduction and nutrient increase) on a global level under

a variety of different conditions. Areas for

research priorities are identified.

Keywords Water current velocity Nutrient

limitation Sediment trapping Resuspension 

Turbidity Light

Introduction

The importance of seagrasses in the marine

ecosystems has been documented in numerous

studies in which seagrasses are noted as a nutrient

Guest editors: Frank van Langevelde and Herbert Prins

Resilience and Restoration of Soft-Bottom Near-Shore

Ecosystems

W. F. de Boer (&)

Resource Ecology Group, Wageningen University,

Droevendaalsesteeg 3a, 6708 PB Wageningen,

The Netherlands

e-mail: fred.deboer@wur.nl

123

Hydrobiologia (2007) 591:5–24

DOI 10.1007/s10750-007-0780-9
source, nursery area, and as a habitat for fishes,

benthic organisms and marine mammals. However, seagrass habitats are highly dynamic, and a

decrease in seagrass extent has been documented

over the last centuries, mainly due to human

disturbance (Cambridge et al., 1986; Short &

Wyllie, 1996; Daby, 2003; Campbell & McKenzie,

2004; Cardoso et al., 2004; Hughes et al., 2004;

Morris & Viknstein, 2004; Gonzalez et al., 2005;

Polte et al., 2005; Waycott et al., 2005; Orth et al.,

2006). An important phenomenon in seagrass

meadows is that seagrasses are able to change

their own environment, by sediment fixation, or

by their capacity to enhance sediment and organic

matter trapping (Moriarty & Boon, 1989). These

processes are sometimes positive feedbacks (Herman et al., 2001; Rietkerk et al., 2004), and

seagrasses could benefit from the changes they

create, stimulating seagrass growth or decreasing

the chance of mortality from erosion (Cardoso

et al., 2004). The large, sometimes cascading

effects generated by seagrasses have been the

basis for some researchers to classify seagrasses as

ecosystem engineers (Koch, 2001). Field studies

normally emphasize only one or few mechanisms

that are responsible for the effect seagrasses have

at their specific study site. However, the effect

seagrasses have on their direct environment can

be the key in understanding seagrass distribution

(Fonseca & Bell, 1998), and thereby the associated faunal community (Walters & Moriarty,

1993; Asmus & Asmus, 2000; de Boer, 2000; de

Boer et al., 2001; de Boer & Prins, 2002a, b;

Fisher & Sheaves, 2003; Healey & Hovel, 2004),

or the nutrient coupling between mangroves,

corals and seagrasses (Slim et al., 1996; Mumby

et al., 2004).

A study is needed to describe the abiotic

conditions of seagrasses under which positive

feedbacks occur. Moreover, various authors

hypothesize that the above positive feedback

mechanisms operate (Moriarty & Boon, 1989;

Koch, 1999; Fonseca et al., 2002), but hard

evidence is often lacking. This review aims to fill

this gap, as such contributing to a better understanding of seagrass dynamics, and constructing a

knowledge-base that will be useful for modelling

seagrass dynamics. Modelling will provide a tool

for predicting the presence/absence or biomass of

seagrass, and the resilience or recovery changes of

seagrass systems. The objective of this review is to

describe these positive feedbacks, to examine the

effect they have on seagrass systems, and to

investigate whether these feedbacks change the

thresholds at which seagrasses are known to

occur, such as the thresholds, or tolerance levels,

related to water depth or water current velocity.

In the first part of the paper the limiting factors

and tolerance levels will be described: water

depth, light availability, water currents, and

nutrient availability. The second part of the paper

examines the effect seagrasses have on sediment

trapping, resuspension, and changes in the sediment, and in the water column, such as a

reduction in turbidity.

Seagrass depth limits

What are the water depths at which seagrasses

can be found, is there a maximum and minimum

depth limiting seagrass occurrence? Koch (2001)

reviewed the effect of waves and tides on the

occurrence of seagrasses as related to the minimum depth where seagrasses can be found.

Seagrass depth limits seem to be related to wave

energy, as waves erode seagrass beds. Chambers

(1987) reported a close correlation between the

depth of surface wave mixing and the minimum

depth of seagrass occurrence, suggesting that the

minimum depth where seagrasses can occur is the

wave mixing depth, calculated as:

Zmin 1⁄4 L=2;

where L can be calculated from L 1⁄4 ðgT2Þ=ð2pÞ,

and g is the acceleration of gravity, i.e. 9.8 m/s,

and

T 1⁄4 0:46W

g

 gF

W2

0:28

where w is the wind velocity (m/s) and F the wind

fetch.

The impact of waves also depends on the tidal

amplitude. Consequently the upper water depth

where seagrasses can occur is dictated by the

wave energy and the maximum tidal amplitude.

6 Hydrobiologia (2007) 591:5–24

123
Seagrasses are found in intertidal areas (especially Zostera spp., Halophila spp. Phyllospadix

spp.), but are generally not fully exposed for

prolonged periods, and disappear under excessive

desiccation or freezing (Ramirez et al., 1998;

Huong et al., 2003; Boese et al., 2005). So that

Zmin becomes:

Zmin 1⁄4 A

2 þ gT2=2p2

Numerous publications have assessed the

effect of light on seagrass distribution, and the

largest depth Zmax where seagrasses occur

(Duarte, 1991; Terrados & Ros, 1995; Abal &

Dennison, 1996; Jagtap, 1996; Olesen, 1996;

Moore et al., 1997; Nelson & Waaland, 1997;

Terrados et al., 1997). Turbidity is an important

factor decreasing irradiance, and thereby determining photosynthetic rates, plant survival and

recruitment, and hence influencing seagrass

occurrence (Duarte, 1991; Abal & Dennison,

1996; Jagtap, 1996; Olesen, 1996; Moore et al.,

1997; Terrados et al., 1997). The lower distribution boundary depth Zmax is set by light availability, and is influenced to a large extent by the

turbidity of the water, influencing Kd, the light

attenuation in the water column:

Zmax 1⁄4  lnðIz=IoÞ

Kd

where Iz/I0 is the species-specific percentage of

light required (or the percentage of light at the

maximum depth of the species).

From Zmax and Zmin the depth range at which

the species may be found can be calculated,

however the formula does not take into account

the effect of wave energy reaching the seagrasses.

Hence, with increasing wave energy Zmin will be

larger, and Zmax unaffected (Koch, 2001).

Hence, the factors that limit seagrass maximum

and minimum depth have been documented

clearly. An overview of the above mentioned

factors, such as wave energy and water column

depth, together with their relative influence on

seagrass occurrence is given in Table 1, and the

main factors impact schematically depicted in

Fig. 1.

Water current velocities

Erosion of bed material through shear stress or

catastrophic events is an important phenomenon

in seagrass meadows (Teeter et al., 2001). Seagrasses are absent under extreme water current

levels, so there is an upper water velocity threshold above which seagrasses do not occur (Fonseca

& Bell, 1998). The force acting on the seagrasses

can be described as (Dawson & Robinson, 1984,

cited in Madsen et al., 2001):

F 1⁄4 k  Vlbm

where F is force in N, V is velocity in m/s, B is the

seagrass biomass in kg Fresh Weight (FW) per

plant, and k,l and m are season and speciesspecific coefficients.

The erosion impact depends on the bed material, with lower erosion values reported for beds

with increased sand content (Aberle et al., 2004).

Bulk density, and thereby the porosity of the

sediment and the organic matter content, are

important predictors for erosion rates, as cohesive

sediments with increased clay content may reduce

erosion. Salinity also influences erosion, with

erosion rates up to five times lower in saltwater

environments than in freshwater (Aberle et al.,

2004). Especially in estuarine waters, with salinities <10&, an increase in salinity increases the

cohesive properties of sediments by influencing

the inter-particle electrochemical bonds (Parchure & Mehta, 1985). A reduction in resuspension of bed material in seagrass meadows also

contributes to an increase in sediment stability

(Gacia & Duarte, 2001).

Fonseca & Bell (1998) showed that seagrass

has a patchy distribution in North Carolina, and

the patchy distribution was attributed to current

speeds and the effect seagrasses have on sediment

stabilization among other factors. Above 50%

seagrass cover (i.e. the % seagrass cover within

the meadow), currents speeds were typically

<0.25 m/s, below the initial motion current speed

of sand. Fonseca & Bell (1998) predicted to find a

patchy distribution in high energy areas, whereas

continuous seagrass meadows would be more

typical for low energy areas. State transitions are

quite rapid once the thresholds have been

Hydrobiologia (2007) 591:5–24 7

123
Table 1 Overview of main factors influencing seagrass occurrence with a subjective estimate of their relative importance

Parameter Importance Spp References

Seagrass minimum depth limits

Maximum water column depth + y Koch (2001), Chambers (1987)

Wave energy + y Koch (2001), Madsen et al. (2001), Fonseca and Bell (1998)

Tidal range + n Koch (2001)

Maximum temperature – y Ramirez et al. (1998), Boese et al. (2005)

Wind force + n Preen et al. (1995), Bell et al. (1999)

Wind velocity + n Koch (2001)

Seagrass maximum depth limits

Light attenuation + n Duarte (1991)

Turbidity + n Duarte (1991), Abbal & Dennison (1996)

Sediment reflectance – n Zimmerman & Mobley (1997)

Tidal ranges + n Koch (2001)

Self-shading + y Fonseca et al. (1982), Ruiz & Romero (2001)

Hour of the day + n Van Duin et al. (2001)

Season + n Van Duin et al. (2001), Plus et al. (2003)

Waves (reflectance) – n Van Duin et al. (2001)

Wave focussing – n Van Duin et al. (2001)

Cloudiness + n Van Duin et al. (2001)

Epiphyte biomass + y Strand & Weisner (1996), Hays (2005)

Sediment burial + y Preen et al. (1995), Vermaat et al. (1997)

Seagrass erosion mortality

Grainsize – y Teeter et al. (2001)

Wave energy + y Koch (2001)

Water porosity + y Aberle et al. (2004)

Salinity – n Parchure & Mehta (1985), Aberle et al. (2004)

Seagrass aboveground biomass + y Madsen et al. (2001)

Rhizome architecture + y Marba` & Duarte (2001), Kendrick et al. (2005)

Above/belowground biomass ratio + y Madsen et al. (2001)

Seagrass critical erosion force + y Madsen et al. (2001)

Sediment plasticity + n Aberle et al. (2004)

External factors:, e.g. diatom films,

arenicola activity etc.

– y Herman et al. (2001), Cappuci et al. (2004), Louda et al.

(2004)

Seagrass sediment trapping and resuspension reduction

Water current velocity + n Herman et al. (2001), van Duin et al. (2001)

Sediment composition (e.g. clay/silt

fraction)

+ n Teeter et al. (2001), Aberle et al. (2004)

Sediment cohesiveness + n Aberle et al. (2004)

Seagrass vertical biomass profiles + y Gacia et al. (1999a), Madsen et al. (2001)

Seagrass architecture (e.g. leaf shape,

bending force)

+ y van Keulen & Borowitzka (2002)

Seagrass bending flexibility – y Madsen et al. (2001)

Water current attenuation + y Fonseca & Kenworthy (1987)

Wave energy (& wind energy) + n Madsen et al. (2001), Koch (2001)

Tidal energy + n Koch & Beer (1996), Herman et al. (2001)

Turbulence + n Wolanski (1992), Furukawa et al. (1997), Gacia & Duarte

(2001), Louda et al. (2004)

Edge/meadow ratio + y Fonseca et al. (1982)

Leaf/area index + y Gacia et al. (1999a)

Sediment surface roughness – y Madsen et al. (2001)

Sediment suitability

Grain size – n Erftemeijer & Middelburg (1993)

Nutrient composition (N, P) + y Hughes et al. (2004)

Organic matter content + y Koch (2001)

Sulphide concentration + n Isaksen & Finster (1996), Koch (2001)

8 Hydrobiologia (2007) 591:5–24

123
reached. Thresholds do however seem to be

species-specific, with different species exhibiting

different patterning at similar current speeds or

wave disturbance (Fonseca & Bell, 1998). The

authors also described the formation of halo-like

patterns in seagrass patches, and suggested that

the pattern was caused by radial growth from

plants that colonized the patches from the middle

of the circle.

Sediment stabilization by seagrasses may enhance seagrass survival rates especially during

periods of extreme conditions such as storms

(Preen et al., 1995; Bell et al., 1999; Gacia &

Duarte, 2001). However, few studies have been

able to document the threshold above which

meadows are eroded. Fonseca & Bell (1998)

showed that belowground biomass increased with

increasing wave disturbance, suggesting compensatory seagrass growth to adapt to unfavourable

local conditions. One study indicated that Zostera

marina beds can tolerate current velocities up to

120–150 cm/s (Fonseca et al., 1983). Koch (2001)

reported minimum current velocities of

0.04–16 cm/s, and maximum velocities between

7 and 180 cm/s tolerated by seagrass, depending

upon species, with intermediate velocities of 5–

100 cm/s for optimal development. The latter

values represent the upper water current velocity

threshold for seagrasses, but there is also a lower

water current velocity threshold. Low velocities

could decrease photosynthetic rates through a

reduction in the diffusion boundary layer limiting

carbon availability (Fonseca & Kenworthy, 1987;

Koch, 1994; Madsen et al., 2001), although carbon

limitation mainly occurs at low blade friction

velocities (<0.25 cm/s). These lower water velocities are probably only possible during slack tide.

Hence, CO2 exchange is improved and also

nutrient limitation reduced at increasing current

speed, with maximum values observed at 0.02–

0.06 m/s (Madsen et al., 2001). At lower current

speeds a thicker diffusion boundary layer will be

built up. Higher mortalities have been observed

due to carbon limitation if the diffusion boundary

layer is larger than the critical diffusion boundary

layer for each species (98–280 lm; Koch, 2001).

Low densities of epiphytes may disrupt the

diffusion boundary layer, stimulating carbon

exchange, but generally epiphytes are regarded

as having only negative effect on seagrasses

(Koch, 2001).

Sediment stability can also be enhanced by

numerous other factors, from diatom biofilms

(Herman et al., 2001; Cappuci et al., 2004) to

Corophium or Arenicola activity. Seagrasses

might be able to enhance sediment stabilization

indirectly, but according to Defew et al. (2002) it

is unlikely that universal proxy parameters for

sediment stability could be obtained. Louda et al.

(2004) showed that seagrasses could be important

catalysts in state transitions, by reducing wave

energy levels, facilitating the development of

hydrogels, built up from polysaccharides derived

Table 1 continued

Parameter Importance Spp References

Salinity – y van Katwijk et al. (1999)

Oxygen content + y Isaksen & Finster (1996)

(+ = often cited as being important, or with high effect size; – = infrequently cited, or with low effect size), whether the

factors are species-specific (y/n), and key references (for additional references consult the main text)

Seagrass

Biomass = f(light,

temp)

Zmax=

•light

•K-attenuation

Light=lattitude

•Month/hour

•Reflectance

•Focussing

k=k1+k2...ki

•depth

•sediment load

•water

PErosion=

• velocity

• Seagrass biomass

• Tide

• Wind fetch

• Wind force

• Depth

• Turbulence

• Water current

• Grain size ( % clay)

• OM

• Cohesiveness

• Biomass

• Architecture

• Size

• LAI

•Epiphytes

•Self-shading

•Detritus

•Burial

Zmin=

•wind fetch

•wind velocity

•tide

Fig. 1 Schematic representation of the main factors that

determine seagrass occurrence, see text for explanation

Hydrobiologia (2007) 591:5–24 9

123
from diatoms and cynobacteria, thereby enhancing sediment stabilization. Benthic microalgae

increased sediment stabilization due to their

production of extracellular polymeric substances

(Austen et al., 1999). Another effect generated by

lower water current levels, and impact of seagrass

meadows is found in the increase of filamentous

macroalgae in seagrass meadows (Piazi et al.,

2002; Keuskamp, 2004), potentially leading to an

even stronger negative effect on current speeds.

Erosion is an important process, affecting seagrass occurrence. However, the species-specific

thresholds, and the effect seagrasses have on

sediment stabilization, thereby decreasing the

erosion probability, are poorly documented.

Nutrient limitation

Some studies have addressed the role of seagrasses in increasing nutrient availability in seagrass meadows, thereby increasing seagrass

growth. However, this effect can only be important if seagrasses are nutrient limited. There is a

large ongoing debate (e.g. compare Koch, 2001;

Hughes et al., 2004) about the relative importance

of nutrient limitation versus light limitation.

N-limitation in seagrass has been reported in

various studies (Boon, 1986; Kenworthy & Fonseca, 1992; McGlathery et al., 1992; Lee & Dunton,

2000), similar to P-limitation (Short et al., 1985,

1990; Fourqurean et al., 1992; Erftemeijer &

Middelburg, 1993; Perez et al., 1994; Fourqurean

& Cai, 2001; Gras et al., 2003). An important

distinction between N- and P-limitation occurs in

relation to sediment type, with typical N-limitation of seagrasses in temperate areas on terrigenous or sandy sediments, and P-limitation in

tropical environments on carbonate sediments

(Short, 1987; Touchette & Burkholder, 2000).

However, some studies have reported N-limitation in carbonate sediments (Udy et al., 1999).

Terrigeneous run-off is larger in coastal systems

than in off-shore oligotrophic reefs systems, so

that the location of the seagrasses, i.e. the

distance to the nutrient source, is also important

(Carruthers et al., 2002; Fourqurean & Zieman,

2002). Nutrient availability is also determined

partly by sediment types, as porewater nutrient

concentrations depend on grain size and sediment

origin (Fourqurean et al., 1992; Holmer et al.,

2001). Coarse-grained carbonate sediments have

larger phosphate availability due to the sediments’ limited adsorption capacity, compared to

fine-grained sediments (Erftemeijer & Middelburg, 1993). However, carbonate sediments are

generally low in organic matter content (Erftemeijer, 1994).

In order to be able to study the potential effect

feedbacks have on seagrass performance, it is

important to distinguish the seagrass species in

terms of nutrient limitation. Duarte (1995)

described the effect of a gradient of nutrient

addition to seagrass sediments, and expected a

shift from slow-growing seagrasses and large

macro-algae, to fast-growing macro-algae, ultimately leading to a phytoplankton dominated

state, with these three states reflecting a change

from nutrient to light limitation (see also Harlin

& Thorne, 1981; Davis & Fourqurean, 2001; Plus

et al., 2003). Seagrasses have low nutrient requirements and are able to recycle nutrients efficiently,

so that they are strong competitors under low

nutrient levels (Koch, 2001; Armitage et al.,

2005). Seagrass species react differently to different nutrient levels so that changes in community

composition are expected when the nutrient pool

changes (Duarte 1992; Agawin et al., 1996; Udy &

Dennison, 1997; Ferdie & Fourqurean, 2004).

Seagrasses are however often limited by different factors according to the seasons, such as

light limitation in winter, and N-limitation in

summer or during the peak growing season (Short

et al., 1993; Herzka & Dunton 1998; McMahon &

Walker 1998; Campbell 2001; Plus et al. 2003).

Similarly, spatial variation exists in different

limiting factors at different locations (Terrados

et al., 1999; Ferdie & Fourqurean 2004). In fact,

some systems show both N- and P-limitation

depending on the local conditions (Fourqurean &

Zieman, 2002; Alcoverro et al. 1997). The various

seagrass life stages may exhibit different tolerance to nutrient levels (Kenworthy & Fonseca,

1992).

Effective nutrient resorption from senescing

leaves becomes important when nutrients are

limited (Hemminga et al., 1999). If the sediment

nutrient pool is limited, water nutrient flow

10 Hydrobiologia (2007) 591:5–24

123
becomes more important (Sfriso & Marcomini,

1999), emphasizing the role leaves have in nutrient intake (Stapel et al., 1996). Lepoint et al.

(2002) calculated that leaf and root contribute

respectively 40% and 60% to the annual Nuptake for Posidonia oceanica in the Mediterranean. In fact, standing stock nutrient pools are a

poor indicator of nutrient limitation, and understanding the dynamics of nutrient pools, sinks and

flows is important to untangle the role specific

nutrients have in limiting seagrass growth (McGlathery et al., 2001). The importance of nitrogen

fixation and denitrification in seagrass beds needs

to be understood (Rysgaard et al., 1996; Welsh

et al., 2000) in order to be able to estimate the

impact of an increased nutrient availability on the

nitrogen budget in seagrass systems.

Eutrophication is also important, as it stimulates macroalgae and phytoplankton growth,

increases the concentration of solids, and triggers

anoxic effects, resulting in reduced light availability and the loss of seagrass cover (Valiela

et al., 1990; Powell et al., 1991; Abal & Dennison,

1996; Livingston et al., 1998; Lee et al., 2004). The

global decrease in seagrass cover has been attributed to eutrophication increasing epiphyte biomass (Hughes et al., 2004). Direct toxic effects of

eutrophication, such as ammonia toxicity or

excessive nitrate concentrations, have also been

reported (Touchette & Burkholder, 2000; Peralta

et al., 2003). Salinity and eutrophication interact,

and can explain decrease in Zostera beds in the

northern hemisphere (van Katwijk et al., 1999).

Some authors do however emphasize light as

the main limiting factor for seagrass occurrence

or seagrass growth (Duarte, 1991; Terrados &

Ros, 1995; Hillman et al., 1995; Abal & Dennison,

1996; Jagtap, 1996; Olesen, 1996; Moore et al.,

1997; Nelson & Waaland, 1997; Terrados et al.,

1997). Various studies were unable to find any

effect of nutrient availability on seagrass performance or occurrence, both in correlative studies

or experiments (Erftemeijer et al., 1994; Vermaat

& Verhagen, 1996; Ceccherelli & Cinelli, 1999;

Rose & Dawes, 1999; Worm & Reusch 2000;

Holmer et al., 2001), so that it is still difficult to

generalize about the light versus nutrient limitation effects. In comparison to the limiting factors

described above, factors such as salinity or

temperature (Perez & Romero, 1992; Hillman

et al., 1995) have a smaller impact on seagrass

performance or on seagrass distribution.

Sediment trapping

One of the most frequently quoted impacts of

seagrasses on their environment is their capacity

to trap sediments. The ability of seagrass to

influence sediment settling is related to water

velocity and sediment particle size. Absolute

current velocities over time determine the fraction of the sediment that will be deposited,

depending on the differential settling velocity of

the different particles in relation to the upward

force. The fall velocity is proportional to the

diameter squared of the different particles and

densities differences (Stoke’s Law; van Duin

et al., 2001). Sand particles settle at speeds

<0.20 m/s, whereas coarse sand gravel settles at

higher current speeds (<1 m/s). The clay fraction

has the smallest grain size, but because of its

cohesiveness, requires larger current speeds to

erode. Deposition of finer particles is therefore

strongly influenced by tidal current and tracks the

tidal cycles (Herman et al., 2001). The silt and

clay fraction will only settle under very low

current levels, and is increased in areas that cope

with high siltation levels (Cappuci et al., 2004).

Seagrasses reduce the water flow above the

sediment, enhancing sedimentation (Fonseca &

Kenworthy, 1987). Sediment trapping has been

reported for various seagrass species and numerous locations (see overview in Koch, 2001 and

Madsen et al., 2001; Gacia et al., 2003), although

some studies, mainly concentrating on relatively

small species such as Halodule spp. and Halophila

spp. found no significant difference between

vegetated and unvegetated sites in terms of

sediment structure or nutrient status (Mellors

et al., 2002). Sediment trapping has also been

recorded for kelp forests (Eckman et al., 1989),

bryozoan meadows (McKinney & Jaklin, 2001)

and other macrophyte vegetations (Vermaat

et al., 2000; Madsen et al., 2001). Rhizome

architecture is highly variable among seagrass

species (Marba` & Duarte, 2001; Kendrick et al.,

2005; Sintes et al., 2005), and has probably an

Hydrobiologia (2007) 591:5–24 11

123
important impact on current reduction. Water

velocity profiles normally show log–profile relationships, and are reduced with a factor 2–10 in

seagrass beds compared to above the canopy

(Gambi et al., 1990; Koch, 2001). This reduction

in water velocity depends on the architecture and

biomass of the seagrass meadows. For instance, in

meadows where sheaths hold the leaves above the

surface, the water velocity near the bottom were

three times stronger than the ones passing

through the seagrass leaf strata (Koch, 1999).

Hence, the water velocity profile is strongly

influenced by the vertical seagrass biomass distribution. Seagrasses with branched erect stems with

terminal leave clusters, such as Amphibolis, are

characterized by high water velocities just beneath the leaf canopy (van Keulen & Borowitzka,

2002). When seagrasses cover the entire water

column (e.g. during neap tide), current velocities

are efficiently reduced and suspended sediments

can settle; in areas where the water depth is larger

than the meadow height, both resuspension and

deposition occurs simultaneously (Koch, 1999,

2001). Shoot bending is a mechanism to reduce

current velocity (up to 50% reduction in current

velocity; Madsen et al., 2001), but it also increases

self-shading and thereby reduces the photosynthetic capacity. The effect of current reduction on

sedimentation also depends on the local hydrodynamic climate, as unidirectional flows (tides)

lead to lower mixing between water above and

within the meadows, whereas waves increase

water exchange between the two layers (Koch &

Gust, 1999).

There is not only a vertical gradient in the

impact of seagrasses on water velocity but also a

horizontal component. Current velocity intrusion

into the meadows proceed by a factor 1.25 into

the meadow per cm/s current velocity, before

diminution, or by a factor 2.1 before maximum

current reduction (Fonseca et al., 1982), indicating that the meadow edge is the most dynamic

zone of seagrass habitats.

Fonseca & Kenworthy (1987) reported that

canopy height decreases linearly with increasing

current speed. However, there is no general

relationship between the water current reduction, wave attenuation and seagrass biomass

profiles, complicating the possibility of including

the latter relationship in mathematical models

(Madsen et al., 2001). Sedimentation is stratified

horizontally and vertically, and depends on

currents, waves, wind energy transfer (Lund

et al., 1993) and seagrass biomass profiles. The

effect of the seagrass biomass and architecture

on current reduction and associated increase in

sedimentation has been investigated in few

studies. Water current velocity reduction is

positively correlated with the height of the

plants, and the surface area of the plants is

significantly correlated with the amount of

trapped particles (Gacia et al., 1999a). Gacia

et al. (1999a) showed that the downward sediment flux increased from 5 to 11 g DW/m2

/d

under an increase of the Leaf Area Index from 1

to 5 m2 leaves/m2

. Gacia et al. (2003) documented daily deposition rates between 19 and

681 g DW/m2

/d, with the majority < 200 g DW/

m2

/d, and organic matter (OM) content <8%.

The latter study also made a summary of the

sedimentation values reported in other studies

showing average values 2.3–67.4 g DW/m2

/d.

Organic matter is also trapped in seagrass

meadows, however this is not always advantageous. Koch (2001) showed that sediment with

>5% OM had a negative effect on marine

macrophyte development. There is a negative

effect of current speeds on nutrient availability

and organic matter content (Chambers et al.,

1991), which might influence seagrass biomass

either linearly (nutrients) or unimodally (organic

matter). Hence, resuspension may be an important process, preventing OM from building up

above critical levels. Water currents are thus

able to constrain seagrass growth through their

effect on sediment composition. The silt concentration in the water column also has other

effects; seagrass species composition and leaf

biomass values change under an increasing silt

fraction in the sediment, with relatively low

species richness (from five to one species) and

reduced leaf biomass (from 150 to <50 g DW/

m2

) with increasing silt and clay content of the

sediment from about 3–45% (Terrados et al.,

1998).

Besides small organic matter particles, also

larger biogenic material can be trapped in seagrass beds. Posidonia oceanica beds accumulate

12 Hydrobiologia (2007) 591:5–24

123
roots, rhizomes and shoots over thousands of

years, with an average of 0.175 cm/yr, equivalent

to 58 g C/m2

/yr, 0.59 g N/m2/yr, and 0.03 g P/m2/

yr (Mateo et al., 1997). Other studies reported

accretion rates of 0.34–1.50 cm/yr (references

cited in Mateo et al., 1997).

Sedimentation of organic sediments is determined by the differential settling velocity of the

particles. Organic matter is a food resource for a

wide variety of benthic species and can be used as

a nutrient pool by the seagrasses. Besides a direct

impact on the nutrient and OM pools, the OM

content can also influence colonization of animals, for example corophiid amphipods (Ford

et al., 2001), or other benthic species (Fisher &

Sheaves, 2003). There is an interaction between

hydrodynamics and sediment composition in

determining colonization rate and size distribution of amphipods. High organic matter contents

(>1%), decreased oxygen levels and increased

sulphur levels had a negative effect on amphipod

colonization rate. Isaksen & Finster (1996) also

reported the positive effect of degradation of leaf

fragments in the sediment on pH, redox potential

and sulphate reduction. This could potentially

lead to the build-up of toxic sulphide concentrations from sulphate reducing bacteria in anoxic

sediment above seagrass tolerance levels. Sulphate reduction rates were about twice as high in

the root zone (0–4 cm) of by Zostera noltii

vegetated sediments than in unvegetated sediments, but no significant difference could be

found below the root zone (Isaksen & Finster,

1996). An increase in the clay and silt fraction in

the sediment through sediment trapping leads to a

reduction in pore water exchange with the water

column, contributing as such to anoxic conditions.

Koch (2001) reported that seagrasses normally

occur at sediment sulphide concentration <1–

2 mM. Clay and silt fraction in seagrass meadows

vary widely between 0.4% and 72%, with highest

values reported from lower salinity environments.

In higher salinity environments coarser sediments

are needed to reduce sulphide concentration can

be reduced through increased porewater advection rates (Koch, 2001). OM content >5% generally cause nutrient limitation due to the high

organic deposits, or increase sulphide concentrations to toxic levels (Koch, 2001). The negative

effect of sulphide concentrations on seagrass

production seems clear, but no hard thresholds

are available to characterize habitat suitability

(Koch, 2001).

Resuspension of deposited material

Sedimentation in seagrass beds is not only the

result of the reduced water current velocities and

subsequent sediment deposition, but also a

decrease in resuspension of deposited sediments

(Terrados & Duarte, 2000). Bed material is

normally eroded when critical friction velocity

ðUcritÞ is exceeded by the shear stress s, where

U2

 1⁄4 s=q (q is the water density; Madsen et al.,

2001). The suspended particle concentration normally increases exponentially until Ucrit has

been reached. However, this depends on the local

surface roughness, something which has not been

studied in seagrass meadows. Another factor is

whether wave energy reaches the sediment surface. Hence, resuspension is a frequent phenomenon in shallow water where the water column

depth is <1/3 of the wavelength (Carper &

Bachman, 1984). Local turbulence is another

key factor in resuspension of bed material (Wolanski, 1992; Furukawa et al., 1997). The effect of

seagrasses on turbulence has been described as

increasing, decreasing, or unaltering turbulence

levels by various studies (see review in Madsen

et al., 2001), complicating the matter further. One

of the problems in our understanding is that the

smaller particles (silt and clay) and OM tend to

form cohesive sediments, aggregates with special

properties, and that the resuspension and settling

of these sediments is poorly understood (Furukawa et al., 1997; Teeter et al., 2001). Terrados &

Duarte (2000) used dried leaf fragments in their

experiment and found daily particle loss rates of

38–98% in seagrass beds compared to 63–99%

outside these beds. Near-bottom turbulence stress

decreased with a factor 2.5–3 in seagrass meadows, restricting resuspension to the top 1 mm,

instead of the top 3 mm in unvegetated sediments

(Gacia & Duarte, 2001; Louda et al., 2004). The

resuspension rate depends on the local hydrological climate, and is typically lower in sediments

that are covered by bending seagrasses in areas

Hydrobiologia (2007) 591:5–24 13

123
dominated by unidirectional, skimming flows (e.g.

tide dominated), and higher in wave-dominated

areas where friction velocities can be as high as in

unvegetated areas (Koch & Gust, 1999). The

effect seagrasses have on water velocity and

especially on water currents just above the

surface also depends on the vertical biomass

stratification and architecture of the species,

differing for round or flat-bladed species (Fonseca

& Fisher, 1986), and meadow or canopy forming

species (Best et al., 2001).

Gacia & Duarte (2001) reported that the

effect Posidonia meadows had on sedimentation

was mainly through a reduction in resuspension,

than from an increase of captured material from

the water column. Resuspension accounted for

85–95% of the total deposited material in other

studies (Gacia & Duarte, 2001; Louda et al.,

2004). Dauby et al. (1995) estimated that 70% of

deposited sediment (1.3 kg/m2

/yr) consisted of

resuspended material, and emphasized that the

resuspended material consisted mainly of seagrass-derived detritus, while during phytoplankton blooms planktonic material was deposited.

Resuspension is increased during gales and is a

major factor in determining water column nutrient availability (Cowan et al., 1996). Unvegetated areas and vegetated areas show strong

differences in water column phosphorus concentration, with wind speeds having a positive effect

on water nutrient concentration, and stable

P-concentrations in areas covered by freshwater

macrophytes (Madsen et al., 2001), as the

meadows prevent the captured nutrients from

escaping. Resuspension is an important source of

nutrients, as nutrient release from resuspension

can provide the majority of nutrients required by

phytoplankton (Cowan et al., 1996; Asmus &

Asmus, 2000). Eckman et al. (1989) showed

similar processes in kelp environments. The

similar trends indicate that the higher sedimentation rates in kelp forests are not the result of

an increased primary deposition, but are created

by the inhibition of transport of suspended

particles, longer residence times, and higher

redeposition chances. Hence, the decrease in

resuspension in seagrass meadows is an important factor changing the local environment,

increasing OM content and nutrient availability.

Sediment changes

What are the consequences of increased sedimentation in seagrass meadows? Water depths of

seagrass meadows tend to decrease over time due

to net sedimentation, and seagrass meadows are

therefore slightly raised above the surrounding

unvegetated sediments. Hence, sedimentation

typically leads to larger exposure times during

low tide in intertidal areas (Madsen et al., 2001).

However, a decrease in depth increases the shear

stress, thereby increasing erosion rates. So a new

balance between sediment erosion and deposition

fixes the depth of the seagrass meadows, together

with other local factors (Koch, 1999). As seagrass

meadows accumulate sediments and increase in

height, water flow is directed towards the lower

lying areas and velocities increase as these channels become narrower; so erosion occurs in the

smaller channels and sedimentation within the

meadows (Madsen et al., 2001). Under extreme

conditions, meadows accumulate sediments until

they emerge and become islands (Hine et al.,

1987). Subaqueous dunes covered by seagrasses

can migrate over long distance, due to the

combined effect of erosion and sedimentation

(Marba` et al., 1994; Marba` & Duarte, 1995;

Vermaat et al., 1997; Koch, 1999). Sediments in

areas with dune transgressions and where seagrasses were present but disappeared are therefore

similar in grain size distribution (Hine et al.,

1987).

There are several adaptations seagrasses have

to assist survival following burial. Vermaat et al.

(1997) expected that seagrasses can cope with

sediment deposition of 2-13 cm/yr through their

vertical stem or rhizome growth (see also Marba`

et al., 1994; Sheridan et al., 1998). Horizontal

rhizome growth is another method to survive

burial. Large variations in horizontal elongation

are reported for different species. Elongation rate

depends on their location within the patch

(inside/edge), with values ranging from 1 cm/yr

to 1,000 cm/yr (Vermaat et al., 1997). Branching

and distances between internodes also increased

under increased burial (Marba` et al., 1994; Duarte

et al., 1997). Besides the impact of burial, stem or

rhizome growth is also seasonal, temperaturedependent, and species-specific (Duarte, 1989,

14 Hydrobiologia (2007) 591:5–24

123
1996; Vermaat et al., 1993, 1995; Marba` et al.,

1996; Vermaat & Verhagen, 1996). There is a

hump-shaped relationship between seagrass

growth and burial depth, with highest reaction

at burial depth of about 5 cm (Marba` & Duarte,

1994). Negative effects of storm events on seagrass meadows have been reported; massive

seagrass die-off have been recorded after storm

events that increased sediment loads far above

average levels or uprooting the plants (Preen

et al., 1995; Koch, 1999). Cyclones might resuspend so much sediments that seagrass meadows

become buried, seed germination is reduced, and

light penetration is below the minimum requirements resulting in meadows die-off (Preen et al.,

1995). Resuspension can also be caused by human

activities, such as eutrophication, trawling, or

dredging (Short & Burdick, 1996; Short & Wyllie,

1996). At high sedimentation levels a negative

effect on seagrass production is generally a

consequence.

A potentially important aspect of increase of

sedimentation and OM levels is the effect on the

nutrient pools in seagrass meadows. Nutrient

availability in sediments can be limited for

seagrass development; roots might not be able

to supply enough nutrients to the plants so that

the nutrient uptake capacity of leaves becomes

more important (Agawin et al., 1996; Stapel et al.,

1996, 1997; Gras et al., 2003; Hughes et al., 2004).

It is possible that the seagrass beds are mostly

closed systems, and that the trapped leaf fragments and other nutrient sources within the

meadows fulfil a key role in the nutrient balance

of seagrasses (Morell & Corredo, 1993; McGlathery et al., 1994; Stapel et al., 1997). Detritus is

important in terms of carbon, nitrogen and

phosphorus, but the importance of detritus in

terms of N-source is probably the most important

(Pedersen et al., 1997). Nutrient reclamation

increases during nutrient stress (Alcoverro et al.,

1997). Particulate detritus and dissolved compounds in the interstitial water accounted for 92-

99% and 0.4-0.9% respectively of the total

amount of nitrogen in the bed in subtropical

Australian study (Boon, 1986). However, detritus

can function both as a nutrient sink, as well as a

nutrient source, depending on the productivity of

the system (Perez et al., 2001). Nutrient trapping

by seagrasses in combination with the effect of

rhizophytic algae improve the sediments in such a

way that nutrients accumulate, facilitating seagrass colonization (Williams, 1990). However, few

studies have investigated the effect sediment

trapping has on nutrient limitation. Sediment

trapping is expected to be more important in offshore systems and in oligothrophic reef systems,

with lower turbidity and higher irradiance in

deeper waters, where carbonate sediments are

nutrient poor. In subtidal or tidal systems, closer

to shores or in estuaries (where most of the

fieldwork to date has been conducted, and where

the majority of the seagrass beds are located)

other limiting factors, such as light are likely to be

more important.

Another rare positive effect of sediment

trapping is an increased germination rate, as

documented in Zostera marina (Moore et al.,

1993). An interaction between water temperature and oxygen content are the main factors

controlling germination (Hootsmans et al.,

1987). Seeds buried 15–25 mm below the surface

had a significantly higher germination rate

(63%) than seeds buried at 5 mm. Postponed

germination could be an adaptation to allow for

bioturbation, stimulating burial deeper in the

sediment to permit the development of an

effective root-anchoring system, enhancing seedling establishment (Moore et al., 1993). This

effect has however only been documented for

Zostera, and no direct positive effect of

increased sedimentation on germination has

been recorded in other seagrass meadows.

A decrease in water velocity does not only

change sedimentation and resuspension rates,

altering indirectly the sediment composition, but

also decreases self-shading, resulting in lower

drag, so that photosynthesis is increased (Fonseca

et al., 1982; Perez & Romero, 1992; Vermaat &

Verhagen, 1996; Ruiz & Romero, 2001).

Sediment trapping and a decrease in resuspension operate in almost all seagrass beds,

leading to changes in the sediment. Besides the

effect of burial, increases in OM content or

available nutrients are the most important factors. However, little is known about the relative

importance of the latter feedback on seagrass

performance.

Hydrobiologia (2007) 591:5–24 15

123
Water column changes

Seagrasses depend on available penetrating light

for photosynthesis. Irradiance normally decreases

exponentially with increasing depth, and the

suspended sediment concentration has a direct

linear effect on light attenuation (van Duin et al.,

2001). The relation between irradiance and depth

is given by the Lambert–Beers Law:

Eðk; 0Þ 1⁄4 Eðk; 0ÞekdðkÞz

where E(k,0) is the irradiance at wavelength k at

the water surface, Kd the vertical attenuation

coefficient, and z is the depth.

Turbidity decreases the amount of light available for photosynthesis. Light attenuation is

wavelength specific, and often described by a

linear trend that sums the downward attenuation

coefficients of water, gilvin (plant degradation

products), solids and phytoplankton (van Duin

et al., 2001). The average attenuation coefficient

Kd for lakes in the Netherlands varied between 1

and 5. Turbidity is an important factor decreasing

irradiance and Zmax, and thereby determining

photosynthetic rates, plant survival and recruitment, and consequently seagrass occurrence

(Duarte, 1991; Terrados & Ros, 1995; Abal &

Dennison, 1996; Jagtap, 1996; Olesen, 1996;

Moore et al., 1997; Nelson & Waaland, 1997;

Terrados et al., 1997; Ruiz & Romero, 2003).

Tidal ranges are important in influencing turbidity and thereby light availability (Koch & Beer,

1996). Light availability is not only influenced by

depth, or turbidity, but also by seagrass shoot

density and the reflectance of the sediment, which

is higher for sand than for muddy sediments

(Zimmerman & Mobley, 1997)

Seagrasses increase sedimentation rates and

reduce resuspension rates; hence, the occurrence

of seagrasses reduces the water sediment load,

and thereby reduces turbidity, promoting further

seagrass growth (Madsen et al., 2001). Total

suspended material varied between 18 mg/l near

seagrass beds to 150 mg/l in unvegetated areas in

Laguna Madre, Texas (Brown & Kraus, 1997

cited in Teeter et al., 2001). Light extinction

depends on suspended sediment concentrations,

particle state and flocculation, adsorption and

water chemistry (van Duin et al., 2001). Teeter

et al. (2001) assumed that seagrasses can still

occur when 20% of the light reaches the meadows, and that the water column extinction coefficient can, even at low levels of resuspension,

limit the depth range of seagrasses. In fact Kemp

et al. (2004) were able to model seagrass occurrence in Chesapeake Bay with a high predictive

power (R2 = 75%) with light availability as the

driving factor, and tidal ranges, light attenuation

and epiphyte influence as covariates.

There is an annual time window during which

non-structural carbohydrates can be built up,

following seasonal trends in light availability

and turbidity (Auby & Labourg, 1996; Burke

et al., 1996; Zimmerman & Alberte, 1996).

During suboptimal conditions, biomass decreases

(Burke et al., 1996). The effect turbidity has is

related to the capacity of seagrasses to overcome

periods of reduced light availability, and is therefore strongly coupled to season (Alcoverro et al.,

1995; Nelson & Waaland, 1997; Madsen et al.,

2001).

Epiphyte biomass is another important factor

(Strand & Weisner-Stefan, 1996; Hays, 2005)

potentially limiting seagrass biomass. Best et al.

(2001) assumed that light attenuation due to

epiphytes is a hyperbolic function approaching

0.75 of maximum attenuation at maximum epiphyte biomass. Epiphyte biomass is negatively

related to wave exposure, illustrated by the

sometimes positive relationship between wave

exposure and macrophytes biomass (Pinckney &

Micheli, 1998; Gacia et al., 1999b; Hays, 2005).

Moreover, epiphytes are sometimes controlled by

grazers (invertebrates or fishes) and increase

under eutrophication, so that different trophic

levels and nutrient input become important variables in the system, indirectly determining seagrass growth (Gacia et al., 1999b; Hays, 2005).

Moore et al. (1996) reported an effect of epiphytes on seagrass biomass, but not on mortality,

indicating the necessity to separate these effects

when studying seagrasses.

Although a direct consequence of increased

sedimentation is an improvement in light availability, negative effects have also been reported,

such as burial of photosynthetic tissue (Duarte

et al., 1997; Manzanera et al., 1998; Brun et al.,

16 Hydrobiologia (2007) 591:5–24

123
2005). To my knowledge no study has measured

the effect of increased sediment load in the water

column within seagrass meadows on the seagrass

photosynthetic rate.

Modelling

Most of the processes and mechanisms mentioned

above are important for our understanding with

regard to the changes in seagrass occurrence.

These can be used in modelling studies to predict

changes in occurrence or performance under

changing conditions, e.g. under eutrophication.

Modelling sediment transport has been carried

out in various studies. It is difficult to include

wind, tide, seasonal effects or wave energy in a

three dimensional dynamic model that includes

the different sediment sources together with the

positive feedbacks in seagrass meadows (Fonseca

et al., 2002; Cappuci et al., 2004; Widdows et al.,

2004). A good overview of the modelling possibilities is given by Teeter et al. (2001) who

modelled the effect of aquatic vegetation on the

hydrodynamics of the area, and the consequences

for sediment transport. Van Duin et al. (2001)

modelled light availability in relation to sedimentation and resuspension, and Beste et al. (2001)

the relationship between macrophyte growth and

light. Valiela et al. (2004) modelled nitrogen

pools in seagrass meadows in relation to nitrogen

inputs (such as nitrogen fixation, external inputs,

atmospheric deposition), and losses (burial and

denitrification). The above approaches illustrate

the multidisciplinary character needed for modelling studies, but also the knowledge gaps. A

challenge would be to integrate the different

models in a spatially explicit 3D environment,

combining the effect of water currents and

turbulence on the differential sediment loads in

the water column, and the effects seagrasses have

on the sedimentation rates of the different sediment fractions and OM content.

From here to there, challenges for the future

Seagrasses occur in areas where the biotic and

abiotic conditions are within the specific tolerance

levels. Important factors are the minimum and

maximum water depths at which seagrasses can

be found, determined by wave orbital velocity,

tide, and light. Other factors such as maximum

and minimum current velocity pose other thresholds. Besides these factors others might be locally

important that could limit seagrass occurrence,

such as nutrient availability (mainly N or P), toxic

sulphide conditions, eutrophication, temperature,

oxygen, or organic matter content (unimodal

relationship). However, the latter factors are

likely to be globally less important.

Understanding the role seagrasses have on

their own system is fundamental in order to

predict or understand their distribution. Light

availability is a key factor in their distribution,

sometimes explaining about 75% of the variation

in seagrass distribution. Light availability is influenced to a large extent by attenuation, and

therefore by the sediment concentration in the

water column. The impact of seagrasses on

sedimentation, trapping sediments from the water

column and decreasing resuspension rates, is

therefore the most important positive feedback

within seagrass systems, as it increases light

availability, stimulating primary productivity and

increasing the maximum depth seagrasses can

occur (Fig. 1). A second factor that also increases

light availability is a reduction of self-shading due

to decreased water currents inside seagrass meadows. Seagrass models should incorporate these

positive feedbacks, especially the effect seagrasses have on light availability, in their algorithms, in

order to be able to improve prediction about

seagrass occurrence.

Besides these latter positive feedbacks others

have been reported, such as sediment stabilization, increased germination rates, or an increase

in nutrient or organic matter availability. All

these factors seem to be less important than

factors directly improving light conditions. It is

possible that these factors are limiting in certain

locations, as occurs in terrestrial systems, where

grass productivity is in some locations limited by

nutrient availability (e.g. moist savannas), in

others by water availability (desert). Similarly,

light limitation in seagrasses might occur in

winter, and N-limitation in summer, as also occurs

in terrestrial vegetation. It is difficult to compare

Hydrobiologia (2007) 591:5–24 17

123
the effect seagrasses have on turbidity reduction

compared to the increase in nutrient availability,

because, to my knowledge, no study has attempted to quantify these different effects in

seagrass meadows. Moreover, few studies have

investigated the effect seagrasses have on light or

nutrients availability at multiple scales over a

wide variety of local conditions, incorporating

different seagrass species differing in their impact

or reaction (Table 1). As such, generalizations

are difficult to make.

In order to improve our understanding of

seagrass biomass dynamics and occurrence, there

is an urgent need for data on the following

aspects:

• the impact of seagrasses on turbulence, and

the effect turbulence has on resuspension

rates; and modelling turbulence effect on

resuspension of bed material (including cohesive sediments) under the influence of seagrasses

• the effect of species-specific seagrass biomass

stratification and architecture on current

reduction and sedimentation rates; synthesize

field findings to general patterns

• the effect of seagrass sediment trapping on

sediment composition, and especially the

effect of the sediment composition via increasing sulphide concentrations on seagrass performance

• the impact of waves (under influence of wind

and tides) on the effect seagrasses have on

sedimentation and resuspension

• although light availability is often regarded as

the major limiting factor of seagrasses, an

overview is needed that describes the effect of

other limiting factors (e.g. nutrient limitation,

sulphide concentrations) in relation to seagrass occurrence.

Most of the papers reported important effects

seagrasses have, modifying their direct environment in terms of light availability or sediment

composition. Indeed, it is generally accepted that

this should have a positive effect on seagrass

growth, or extent of the seagrass meadows.

However, few publications have been able to

quantify the effects of positive feedbacks on

seagrass performance. The hypothesis that positive feedbacks are essential for the survival or

growth of seagrasses has not been tested yet. Will

seagrass primary production decrease, erosion of

seagrasses increase, or the extent of seagrass

meadows reduce when positive feedbacks are not

present? In order to be able to predict or model

the performance of seagrasses under changing

conditions these questions should be answered.

Hence, there remains an important challenge for

ecologists investigating the importance of positive

feedbacks in seagrass systems, necessitating an

experimental approach. We know they are there,

but how important are they for the performance

or resilience of the seagrass systems?

Acknowledgements I would like to thanks the participants

of the Open Science Meeting III, 2005 at Yogyakarta, and

two anonymous reviewers for their valuable comments that

have contributed to the improvement of the original

manuscript.

References

Abal, E. G. & W. C. Dennison, 1996. Seagrass depth range

and water quality in Southern Moreton Bay,

Queensland, Australia. Marine and Freshwater Research 47: 763–771.

Aberle, J., V. Nikora & R. Walters, 2004. Effects of bed

material properties on cohesive sediment erosion.

Marine Geology 207: 83–93.

Agawin, N. S. R., C. M. Duarte & M. D. Fortes, 1996.

Nutrient limitation of Philippine seagrasses (Cape

Bolinao, NW Philippines): In situ experimental evidence. Marine Ecology Progress Series 138: 233–243.

Alcoverro, T., C. M. Duarte & J. Romero, 1995. Annual

growth dynamics of Posidonia oceanica: contribution

of large scale versus local factors to seasonality.

Marine Ecology Progress Series 120: 203–210.

Alcoverro, T., J. Romero, C. M. Duarte & N. I. Lopez,

1997. Spatial and temporal variations in nutrient

limitation of seagrass Posidonia oceanica growth in

the NW Mediterranean. Marine Ecology Progress

Series 146: 155–161.

Armitage, A. R., T. A. Frankovich, K. L. Jr. Heck & J. W.

Fourqurean, 2005. Experimental nutrient enrichment

causes complex changes in seagrass, microalgae, and

macroalgae community structure in Florida Bay.

Estuaries 28: 422–434.

18 Hydrobiologia (2007) 591:5–24

123
Asmus, H. & R. Asmus, 2000. Material exchange and food

web of seagrass beds in the Sylt-Romo Bight: How

significant are community changes at the ecosystem

level? Helgoland Marine Research 54: 137–150.

Auby, I. & P. J. Labourg, 1996. Seasonal dynamics of

Zostera noltii Hornem in the bay of Arcachon

(France). Journal of Sea Research 35: 269–277.

Austen, I., T. J. Andersen & K. Edelvang, 1999. The

influence of benthic diatoms and invertebrates on the

erodibility of an intertidal a mudflat, the Danish

Wadden Sea. Estuarine, Coastal and Shelf Science 49:

99–111.

Bell, S. S., B. D. Robbins & S. L. Jensen, 1999. Gap

dynamics in a seagrass landscape. Ecosystems 2: 493–

504.

Best, E. P. H., C. P. Buzzelli, S. M. Bartell, R. L. Wetzel,

W. A. Boyd, R. D. Doyle & K. R. Campbell, 2001.

Modeling submersed macrophyte growth in relation

to underwater light climate: Modeling approaches and

application potential. Hydrobiologia 444: 43–70.

Boese, B. L., B. D. Robbins & G. Thursby, 2005. Desiccation is a limiting factor for eelgrass (Zostera marina

L.) distribution in the intertidal zone of a northeastern

Pacific (USA) estuary. Botanica Marina 48: 274–283.

Boon, P. I., 1986. Nitrogen pools in seagrass beds of Cymodocea serrulata and Zostera capricorni of Moreton

Bay Australia. Aquatic Botany 25: 1–20.

Brun, F. G., J. J. Vergara, I. Hernandez & J. L. PerezLlorens, 2005. Evidence for vertical growth in Zostera

noltii Hornem. Botanica Marina 48: 446–450.

Burke, M. K., W. C. Dennison & K. A. Moore, 1996. Nonstructural carbohydrate reserves of eelgrass Zostera

marina. Marine Ecology Progress Series 137: 195–201.

Cambridge, M. L., A. W. Chiffings, C. Brittan, L. Moore &

A. J. McComb, 1986. The loss of seagrass in Cockburn

Sound western Australia II; Possible causes of seagrass decline. Aquatic Botany 24: 269–286.

Campbell, S., 2001. Ammonium requirements of fastgrowing ephemeral macroalgae in a nutrient-enriched

marine embayment (Port Phillip Bay, Australia).

Marine Ecology Progress Series 209: 99–107.

Campbell, S. J. & L. J. McKenzie, 2004. Flood related loss

and recovery of intertidal seagrass meadows in

southern Queensland, Australia. Estuarine Coastal

and Shelf Science 60: 477–490.

Cappucci, S., L. Amos, T. Hosoe & G. Umgiesser, 2004. A

numerical model to evaluate the factors controlling

the evolution of intertidal mudflats in Venice Lagoon,

Italy. Journal of Marine Systems 51: 257–280.

Cardoso, P. G., M. A. Pardal, A. I. Lillebo, S. M. Ferreira,

D. Raffaelli & J. C. Marques, 2004. Dynamic changes

in seagrass assemblages under eutrophication and

implications for recovery. Journal of Experimental

Marine Biology and Ecology 302: 233–248.

Carper, G. L. & R. W. Bachmann, 1984. Wind resuspension of sediment in a prairie lake. Canadian Journal of

Fisheries and Aquatic Sciences 41: 1763–1767.

Carruthers, T.-J. B., W. C. Dennison, B. J. Longstaff, M.

Waycott, E. G. Abal, L. J. McKenzie & W.-J. L. Long,

2002. Seagrass habitats of northeast Australia: Models

of key processes and controls. Bulletin of Marine

Science 71: 1153–1169.

Ceccherelli, G. & F. Cinelli, 1999. A pilot study of nutrient

enriched sediments in a Cymodocea nodosa bed invaded by the introduced alga Caulerpa taxifolia.

Botanica Marina 42: 409–417.

Chambers, P. A., 1987. Nearshore occurrence of submersed aquatic macrophytes in relation to wave action. Canadian Journal of Fisheries and Aquatic

Sciences 44: 1666–1669.

Chambers, P. A., E. E. Prepas, H. R. Hamilton & M. L.

Bothwell, 1991. Current velocity and its effect on

aquatic macrophytes in flowing waters. Ecological

Applications 1: 249–257.

Cowan, J. L. W., J. R. Pennock & W. R. Boynton,

1996. Seasonal and interannual patterns of sediment-water nutrient and oxygen fluxes in Mobile

Bay, Alabama (USA): Regulating factors and

ecological significance. Marine Ecology Progress

Series 141: 229–245.

Daby, D., 2003. Effects of seagrass bed removal for tourism purposes in a Mauritian bay. Environmental

Pollution 125: 313–324.

Dauby, P., A. J. Bale, N. Bloomer, C. Canan, R. D. Ling,

A. Norro, J. E. Robertson, J. M. Theate, A. J. Watson

& M. Frankignoulle, 1995. Particle fluxes over a

Mediterranean seagrass bed: A one year case study.

Marine Ecology Progress Series 126: 233–246.

Davis, B. C. & J. W. Fourqurean, 2001. Competition between the tropical alga, Halimeda incrassata, and the

seagrass, Thalassia testudinum. Aquatic Botany 71:

217–232.

de Boer, W. F., 2000. Biomass dynamics of seagrasses and

the role of mangrove and seagrass vegetation as different nutrient sources for an intertidal ecosystem in

Mozambique. Aquatic Botany 66: 225–239.

de Boer, W. F. & H. H. T. Prins, 2002a. Human exploitation and benthic community structure on a tropical

intertidal flat. Journal of Sea Research 48: 225–240.

de Boer, W. F. & H. H. T. Prins, 2002b. The community

structure of a tropical intertidal mudflat under human

exploitation. ICES Journal of Marine Sciences 59:

1237–1247.

de Boer, W. F., A. M. P. van Schie, D. F. Jocene, A. B. P.

Mabote & A. Guissamulo, 2001. The impact of human

presence on the shorebird community structure at a

tropical intertidal mudflat. Environmental Biology of

Fishes 61: 213–229.

Defew, E. C., T. J. Tolhurst & D. M. Paterson, 2002. Sitespecific features influence sediment stability of intertidal flats. Hydrology and Earth System Sciences 6:

971–981.

Duarte, C. M., 1989. Temporal biomass variability and

production/biomass relationships of seagrass communities. Marine Ecology Progress Series 51: 269–276.

Duarte, C. M., 1991. Seagrass depth limits. Aquatic Botany

40: 363–377.

Duarte, C. M., 1992. Nutrient concentration of aquatic

plants: Patterns across species. Limnology and

Oceanography 37: 882–884.

Hydrobiologia (2007) 591:5–24 19

123
Duarte, C. M., 1995. Submerged aquatic vegetation in

relation to different nutrient regimes. Ophelia 41: 87–

112.

Duarte, C. M., M. A. Hemminga & N. Marba`, 1996.

Growth and population dynamics of Thalassodendron

ciliatum in a Kenyan back-reef lagoon. Aquatic Botany 55: 1–11.

Duarte, C. M., J. Terrados, S. R. Agawin-Nona, M. D.

Fortes, S. Bach & W. J. Kenworthy, 1997. Response of

a mixed Philippine seagrass meadow to experimental

burial. Marine Ecology Progress Series 147: 285–294.

Eckman, J. E., D. O. Duggins & A. T. Sewell, 1989.

Ecology of understory kelp environments i. Effects of

kelps on flow and particle transport near the bottom.

Journal of Experimental Marine Biology and Ecology

129: 173–188.

Erftemeijer, P. L. A., 1994. Differences in nutrient concentrations and resources between seagrass communities on carbonate and terrigenous sediments in

South Sulawesi, Indonesia, Bulletin of Marine Science

54: 403–419.

Erftemeijer, P. L. A. & J. J. Middelburg, 1993. Sediment–

nutrient interactions in tropical seagrass beds: A

comparison between a terrigenous and a carbonate

sedimentary environment in South Sulawesi (Indonesia). Marine Ecology Progress Series 102: 187–198.

Erftemeijer, P. L. A., J. Stapel, J. E. Smekens-Marret & M.

E. Drossaert-Wim, 1994. The limited effect of in situ

phosphorus and nitrogen additions to seagrass beds on

carbonate and terrigenous sediments in South Sulawesi, Indonesia. Journal of Experimental Marine

Biology and Ecology 182:123–140.

Ferdie, M. & J. W. Fourqurean, 2004. Responses of seagrass communities to fertilization along a gradient of

relative availability of nitrogen and phosphorus in a

carbonate environment. Limnology and Oceanography 49: 2082–2094.

Fisher, R. & M. J. Sheaves, 2003. Community structure

and spatial variability of marine nematodes in tropical

Australian pioneer seagrass meadows. Hydrobiologia

495: 143–158.

Fonseca, M. S. & S. S. Bell, 1998. Influence of physical

setting on seagrass landscapes near Beaufort, North

Carolina, USA. Marine Ecology Progress Series 171:

109–121.

Fonseca, M. S. & J. S. Fisher, 1986. A comparison of

canopy friction and sediment movement between four

species of seagrass with reference to their ecology and

restoration. Marine Ecology Progress Series 29:15–22.

Fonseca, M. S., J. S. Fisher, J. C. Zieman & G. W. Thayer,

1982. Influence of the seagrass Zostera marina on

current flow. Estuarine Coastal and Shelf Science 15:

351–364.

Fonseca, M. S. & W. J. Kenworthy, 1987. Effects of current

on photosynthesis and distribution of seagrasses.

Aquatic Botany 27: 59–78.

Fonseca, M., P. E. Whitfield, N. M. Kelly & S. S. Bell,

2002. Modeling seagrass landscape pattern and associated ecological attributes. Ecological Applications

12: 218–237.

Fonseca, M. S., J. C. Zieman, G. W. Thayer & J. S. Fisher,

1983. The role of current velocity in structuring eelgrass Zostera marina. Estuarine, Coastal and Shelf

Science 17: 367–380.

Ford, R. B., S. F. Thrush & P. K. Probert, 2001. The

interacting effect of hydrodynamics and organic matter on colonization: A soft-sediment example. Estuarine, Coastal and Shelf Science 52: 705–714.

Fourqurean, J. W. & J. C. Zieman, 2002. Nutrient content

of the seagrass Thalassia testudinum reveals regional

patterns of relative availability of nitrogen and phosphorus in the Florida Keys USA. Biogeochemistry 61:

229–245.

Fourqurean, J. W. & Y. Cai, 2001. Arsenic and phosphorus

in seagrass leaves from the Gulf of Mexico. Aquatic

Botany 71: 247–258.

Fourqurean, J. W., J. C. Zieman & G. V. Powell, 1992.

Relationships between porewater nutrients and seagrasses in a subtropical carbonate environment. Marine

Biology 114: 57–65.

Furukawa, K., E. Wolanski & H. Mueller, 1997. Currents

and sediment transport in mangrove forests. Estuarine, Coastal and Shelf Science 44: 301–310.

Gacia, E. & C. M. Duarte, 2001. Sediment retention by a

Mediterranean Posidonia oceanica meadow: The

balance between deposition and resuspension. Estuarine Coastal and Shelf Science 52: 505–514.

Gacia, E., C. M. Duarte, N. Marba`, J. Terrados, H. Kennedy, M. D. Fortes & N. H. Tri, 2003. Sediment

deposition and production in SE-Asia seagrass

meadows. Estuarine, Coastal and Shelf Science 56:

909–919.

Gacia, E., T. C. Granata & C. M. Duarte, 1999a. An approach to measurement of particle flux and sediment

retention within seagrass (Posidonia oceanica)

meadows. Aquatic Botany 65: 255–268.

Gacia, E., M. M. Littler & D. S. Littler, 1999b. An

experimental test of the capacity of food web interactions (fish-epiphytes-seagrasses) to offset the negative consequences of eutrophication on seagrass

communities. Estuarine Coastal and Shelf Science 48:

757–766.

Gambi, M. C., A. R. M. Nowell & P. A. Jumars, 1990.

Flume observations on flow dynamics in Zostera

marina eelgrass beds. Marine Ecology Progress Series

61: 159–169.

Gonzalez, C. J. M., J. T. Bayle, J. L. Sanchez-Lizaso, C.

Valle, P. Sanchez-Jerez & J. M. Ruiz, 2005. Recovery

of deep Posidonia oceanica meadows degraded by

trawling. Journal of Experimental Marine Biology

and Ecology 320: 65–76.

Gras, A. F., M. S. Koch & C. J. Madden, 2003. Phosphorus

uptake kinetics of a dominant tropical seagrass Thalassia testudinum. Aquatic Botany 76: 299–315.

Harlin, M. M. & M. B. Thorne, 1981. Nutrient enrichment

of seagrass beds in a Rhode-island USA coastal lagoon. Marine Biology 65: 221–230.

Hays, G., 2005. Effect of nutrient availability grazer

assemblage and seagrass source population on the

interaction between Thalassia testudinum (turtle

20 Hydrobiologia (2007) 591:5–24

123
grass) and its algal epiphytes. Journal of Experimental

Marine Biology and Ecology 314: 53–68.

Healey, D. & K. A. Hovel, 2004. Seagrass bed patchiness

effects on epifaunal communities in San Diego Bay,

USA. Journal of Experimental Marine Biology and

Ecology 313: 155–174.

Hemminga, M. A., N. Marba` & J. Stapel, 1999. Leaf

nutrient resorption, leaf lifespan and the retention of

nutrients in seagrass systems. Aquatic Botany 65: 141–

158.

Herman, M. J., J. Middelburg & H. R. Heip, 2001. Benthic

community structure and sediment processes on an

intertidal flat: results from the Ecoflat project. Continental Shelf Research 21: 2055–2071.

Herzka, S. Z. & K. H. Dunton, 1998. Light and carbon

balance in the seagrass Thalassia testudinum: Evaluation of current production models. Marine Biology

132: 711–721.

Hillman, K., A. J. McComb & D. I. Walker, 1995. The

distribution, biomass and primary production of the

seagrass Halophila ovalis in the Swan/Canning Estuary, Western Australia. Aquatic Botany 51: 1–54.

Hine, A. C., M. W. Evans, R. A. Davis, Jr. & D. F. Belknap, 1987. Depositional response to seagrass mortality along a low-energy barrier-island coast westcentral Florida USA. Journal of Sedimentary Petrology 57: 431–439.

Holmer, M., F. O. Andersen, S. L. Nielsen & T. S. Boschker-Henricus, 2001. The importance of mineralization based on sulfate reduction for nutrient

regeneration in tropical seagrass sediments. Aquatic

Botany 71: 1–17.

Huong, T. T. L., J. E. Vermaat, J. Terrados, T. N. Van, C.

M. Duarte, J. Borum & N. H. Tri, 2003. Seasonality

and depth zonation of intertidal Halophila ovalis and

Zostera japonica in Ha Long Bay (northern Vietnam).

Aquatic Botany 75: 147–157.

Hootsmans, M. J. M., J. E. Vermaat & W. van Vierssen,

1987. Seed-bank development germination and early

seedling survival of two seagrass species from the

Netherlands Zostera-marina L. and Zostera-noltii

Hornem. Aquatic Botany 28: 275–286.

Hughes, A. R., K. J. Bando, L. F. Rodriguez & S. L.

Williams, 2004. Relative effects of grazers and nutrients on seagrasses: A meta-analysis approach. Marine

Ecology Progress Series 282: 87–99.

Isaksen, M. F. & K. Finster, 1996. Sulphate reduction in

the root zone of the seagrass Zostera noltii on the

intertidal flats of a coastal lagoon (Arcachon, France).

Marine Ecology Progress Series 137: 187–194.

Jagtap, T. G., 1996. Some quantitative aspects of structural

components of seagrass meadows from the Southeast

coast of India. Botanica Marina 39: 39–45.

Kemp, W. M., R. Batiuk, R. Bartleson, P. Bergstrom, V.

Carter, C. L. Gallegos, W. Hunley, L. Karrh, E. W.

Koch, J. M. Landwehr, K. A. Moore, L. Murray, M.

Naylor, N. B. Rybicki, J. C. Stevenson & D. J. Wilcox,

2004. Habitat requirements for submerged aquatic

vegetation in Chesapeake Bay: Water quality, light

regime, and physical-chemical factors. Estuaries 27:

363–377.

Kendrick, G. A., N. Marba` & C. M. Duarte, 2005. Modelling formation of complex topography by the seagrass Posidonia oceanica. Estuarine Coastal and Shelf

Science 65: 717–725.

Kenworthy, W. J. & M. S. Fonseca, 1992. The use of fertilizer to enhance growth of transplanted seagrasses

Zostera marina L. and Halodule wrightii Aschers.

Journal of Experimental Marine Biology and Ecology

163: 141–161.

Keuskamp, D., 2004. Limited effects of grazer exclusion on

the epiphytes of Posidonia sinuosa in South Australia.

Aquatic Botany 78: 3–14.

Koch, E. W., 1994. Hydrodynamics, diffusion-boundary

layers and photosynthesis of the seagrasses Thalassia

testudinum and Cymodocea nodosa. Marine Biology

Berlin 118: 767–776.

Koch, E. W., 1999. Sediment resuspension in a shallow

Thalassia testudinum banks ex Ko ̈nig bed. Aquatic

Botany 65: 269–280.

Koch, E. W., 2001. Beyond light: Physical, geological, and

geochemical parameters as possible submersed aquatic vegetation habitat requirements. Estuaries 24: 1–

17.

Koch, E. W. & S. Beer, 1996. Tides, light and the distribution of Zostera marina in Long Island Sound, USA.

Aquatic Botany 53: 97–107.

Koch, E. W. & G. Gust, 1999. Water flow in tide- and

wave-dominated beds of the seagrass Thalassia testudinum. Marine Ecology Progress Series 28: 63–72.

Lee, K. S. & K. H. Dunton, 2000. Effects of nitrogen

enrichment on biomass allocation, growth, and leaf

morphology of the seagrass Thalassia testudinum.

Marine Ecology Progress Series 196: 39–48.

Lee, K. S., F. T. Short & D. M. Burdick, 2004. Development of a nutrient pollution indicator using the seagrass, Zostera marina, along nutrient gradients in

three New England estuaries. Aquatic Botany 78:

197–216.

Lepoint, G., S. Millet, P. Dauby, S. Gobert & J. M. Bouquegneau, 2002. Annual nitrogen budget of the seagrass Posidonia oceanica as determined by in situ

uptake experiments. Marine Ecology Progress Series

237: 87–96.

Livingston, R. J., S. E. McGlynn & X. Niu, 1998. Factors

controlling seagrass growth in a gulf coastal system:

Water and sediment quality and light. Aquatic Botany

60: 135–159.

Louda, J. W., J. W. Loitz, A. Melisiotis & W. H. Orem,

2004. Potential sources of hydrogel stabilization of

Florida Bay lime mud sediments and implications for

organic matter preservation. Journal of Coastal Research 20: 448–463.

Lund, H. L. C., M. Pejrup, J. Valeur & A. Jensen, 1993.

Gross sedimentation rates in the North Sea-Baltic Sea

transition: Effects of stratification, wind energy

transfer, and resuspension. Oceanologica Acta 16:

205–212.

Madsen, J. D., P. A. Chambers, W. F. James, E. W. Koch

& D. F. Westlake, 2001. The interaction between

water movement, sediment dynamics and submersed

macrophytes. Hydrobiologia 444: 71–84.

Hydrobiologia (2007) 591:5–24 21

123
Manzanera, M., M. Perez & J. Romero, 1998. Seagrass

mortality due to oversedimentation: An experimental

approach. Journal of Coastal Conservation 4: 67–70.

Marba`, N. & C. M. Duarte, 1994. Growth response of the

seagrass Cymodocea nodosa to experimental burial

and erosion. Marine Ecology Progress Series 107:

307–311.

Marba`, N. & C. M. Duarte, 1995. Coupling of seagrass

(Cymodocea nodosa) patch dynamics to subaqueous

dune migration. Journal of Ecology 83: 381–389.

Marba`, N. & C. M. Duarte, 2001. Growth and sediment

space occupation by seagrass Cymodocea nodosa

roots. Marine Ecology Progress Series 224: 291–298.

Marba`, N., J. Cebrian, S. Enriquez & C. M. Duarte, 1994.

Migration of large-scale subaqueous bedforms measured with seagrasses (Cymodocea nodosa) as tracers.

Limnology and Oceanography 39: 126–133.

Marba`, N., J. Cebrian, S. Enriquez & C. M. Duarte, 1996.

Growth patterns of western Mediterranean seagrasses: Species-specific responses to seasonal forcing.

Marine Ecology Progress Series 133: 203–215.

Mateo, M. A., J. Romero, M. Perez, M. M. Littler & D. S.

Littler, 1997. Dynamics of millenary organic deposits

resulting from the growth of the Mediterranean seagrass Posidonia oceanica. Estuarine, Coastal and Shelf

Science 44: 103–110.

McGlathery, K. J., P. Berg & R. Marino, 2001. Using

porewater profiles to assess nutrient availability in

seagrass-vegetated carbonate sediments. Biogeochemistry 56: 239–263.

McGlathery, K. J., R. W. Howarth & R. Marino, 1992.

Nutrient limitation of the macroalga Penicillus capitatus associated with subtropical seagrass meadows in

Bermuda. Estuaries 15: 18–25.

McGlathery, K. J., R. Marino & R. W. Howarth, 1994.

Variable rates of phosphate uptake by shallow marine

carbonate sediments: Mechanisms and ecological significance. Biogeochemistry 25: 127–146.

McKinney, K. & A. Jaklin, 2001. Sediment accumulation

in a shallow-water meadow carpeted by a small erect

bryozoan. Sedimentary Geology 145: 397–410.

McMahon, K. & D. I. Walker, 1998. Fate of seasonal,

terrestrial nutrient inputs to a shallow seagrass dominated embayment. Estuarine Coastal and Shelf Science 46: 15–25.

Mellors, J., H. Marsh & M. Waycott, 2002. Testing the

sediment-trapping paradigm of seagrass: Do seagrass

influence nutrient status and sediment structure in

tropical intertidal environments. Bulletin of Marine

Science 71: 1215–1226.

Moore, K. A., H. A. Neckles & R. J. Orth, 1996. Zostera

marina (eelgrass) growth and survival along a gradient

of nutrients and turbidity in the lower Chesapeake

Bay. Marine Ecology Progress Series 142: 247–259.

Moore, K. A., R. J. Orth & J. F. Nowak, 1993. Environmental regulation of seed germination in Zostera

marina L. (eelgrass) in Chesapeake Bay: Effects of

light, oxygen and sediment burial. Aquatic Botany 45:

79–91.

Moore, K. A., R. L. Wetzel & R. J. Orth, 1997. Seasonal

pulses of turbidity and their relations to eelgrass

(Zostera marina L.) survival in an estuary. Journal of

Experimental Marine Biology and Ecology 215: 115–

134.

Morell, J. M. & J. E. Corredo, 1993. Sediment nitrogen

trapping in a mangrove lagoon. Estuarine Coastal and

Shelf Science 37: 203–212.

Moriarty, D. J. W. & P. I. Boon, 1989. Interactions of

seagrass with sediment and water. In Larkum, A. W.

D. & S. A. Sheppard (eds), Biology of Seagrasses.

Elsevier, Amsterdam, 500–535

Morris, L. J. & R. W. Viknstein, 2004. The demise and

recovery of seagrass in the northern Indian River

Lagoon, Florida. Estuaries 27: 915–922

Mumby, P. J., A. J. Edwards, J. E. Arias-Gonzalez, K. C.

Lindeman, P. G. Blackwell, A. Gall, M. I. Gorczynska, A. R. Harborne, C. L. Pescod, H. Renken, C.

C. C. Wabnitz & G. Llewellyn, 2004. Mangroves enhance the biomass of coral reef fish communities in

the Caribbean, Nature 427: 533–536.

Nelson, T. A. & J. R. Waaland, 1997. Seasonality of eelgrass, epiphyte, and grazer biomass and productivity

in subtidal eelgrass meadows subjected to moderate

tidal amplitude. Aquatic Botany 56: 51–74.

Olesen, B., 1996. Regulation of light attenuation and eelgrass Zostera marina depth distribution in a Danish

embayment. Marine Ecology Progress Series 134:

187–194.

Orth, R. J., M. L. Luckenbach, S. R. Marion, K. A. Moore

& D. J. Wilcox, 2006. Seagrass recovery in the Delmarva Coastal Bays, USA. Aquatic Botany 84: 26–36.

Parchure, T. M., A. J. Mehta, 1985. Erosion of soft cohesive sediment deposits. Journal of Hydraulic Engineering 111: 1308–1326.

Pedersen, M. F., C. M. Duarte & J. Cebrian, 1997. Rates of

changes in organic matter and nutrient stocks during

seagrass Cymodocea nodosa colonization and stand

development. Marine Ecology Progress Series 159:

29–36.

Peralta, G., T. J. Bouma, J. van Soelen, J. L. Perez-Llorens

& I. Hernandez, 2003. On the use of sediment fertilization for seagrass restoration: A mesocosm study on

Zostera marina L. Aquatic Botany 75: 95–110.

Perez, M. & J. Romero, 1992. Photosynthetic response to

light and temperature of the seagrass Cymodocea

nodosa and the prediction of its seasonality. Aquatic

Botany 43: 51–62.

Perez, M., C. M. Duarte, J. Romero, J. K. Sand & T. Alcoverro, 1994. Growth plasticity in Cymodocea nodosa stands: The importance of nutrient supply.

Aquatic Botany 47: 249–264.

Perez, M., M. A. Mateo, T. Alcoverro & J. Romero, 2001.

Variability in detritus stocks in beds of the seagrass

Cymodocea nodosa. Botanica Marina 44: 523–531.

Piazzi, L., D. Balata & F. Cinelli, 2002. Epiphytic macroalgal assemblages of Posidonia oceanica rhizomes in

the western Mediterranean. European Journal of

Phycology 37: 69–76.

Pinckney, J. L. & M. F. Micheli, 1998. Microalgae on

seagrass mimics: Does epiphyte community structure

differ from live seagrasses? Journal of Experimental

Marine Biology and Ecology. 221: 59–70.

22 Hydrobiologia (2007) 591:5–24

123
Plus, M., A. Chapelle, A. Menesguen, J. M. Deslous-Paoli

& I. Auby, 2003. Modelling seasonal dynamics of

biomasses and nitrogen contents in a seagrass meadow (Zostera noltii Hornem.): Application to the

Thau lagoon (French Mediterranean coast). Ecological Modelling 161: 213–238.

Polte, P., A. Schanz & H. Asmus, 2005. The contribution

of seagrass beds (Zostera noltii) to the function of

tidal flats as a juvenile habitat for dominant, mobile

epibenthos in the Wadden Sea. Marine Biology 147:

813–822.

Powell, G. V., J. W. Fourqurean, W. J. Kenworthy & J. C.

Zieman, 1991. Bird colonies cause seagrass enrichment in a subtropical estuary observational and

experimental evidence. Estuarine Coastal and Shelf

Science 32: 567–580.

Preen, A. R., W.-J. L. Long & R. G. Coles, 1995. Flood

and cyclone related loss, and partial recovery, of more

than 1000 km2 of seagrass in Hervey Bay, Queensland, Australia. Aquatic Botany 52: 3–17.

Ramirez, G. P., A. Lot, C. M. Duarte, J. Terrados & N. S.

R. Agawin, 1998. Bathymetric distribution, biomass

and growth dynamics of intertidal Phyllospadix

scouleri and Phyllospadix torreyi in Baja California

(Mexico). Marine Ecology Progress Series 173: 13–23.

Rietkerk, M., S. C. Dekker, P. C. de Ruiter & J. van de

Koppel, 2004. Self-organized patchiness and catastrophic shifts in ecosystems. Science 305: 1926–1929.

Rose, C. D. & C. J. Dawes, 1999. Effects of community

structure on the seagrass Thalassia testudinum. Marine Ecology Progress Series 1999: 83–95.

Ruiz, J. M. & J. Romero, 2001. Effects of in situ experimental shading on the Mediterranean seagrass Posidonia oceanica. Marine Ecology Progress Series 107–

120.

Ruiz, J. M. & J. Romero, 2003. Effects of disturbances

caused by coastal constructions on spatial structure,

growth dynamics and photosynthesis of the seagrass

Posidonia oceanica. Marine Pollution Bulletin 46:

1523–1533

Rysgaard, S., P. N. Risgaard & N. P. Sloth 1996. Nitrification, denitrification, and nitrate ammonification in

sediments of two coastal lagoons in southern France.

Hydrobiologia 329: 133–141.

Sfriso, A. & A. Marcomini, 1999. Macrophyte production

in a shallow coastal lagoon. Part II. Coupling with

sediment, SPM and tissue carbon, nitrogen and

phosphorus concentrations. Marine Environmental

Research 47: 285–309.

Sheridan, P., G. McMahan, K. Hammerstrom & W. Pulich,

Jr., 1998. Factors affecting restoration of Halodule

wrightii to Galveston Bay, Texas. Restoration Ecology 6: 144–158.

Short, F. T., 1987. Effects of sediment nutrients on seagrasses literature review and mesocosm experiment.

Aquatic Botany 27: 41–58.

Short, F. T. & D. B. Burdick, 1996. Quantifying eelgrass

habitat loss in relation to housing development and

nitrogen loading in Waquoit Bay, Massachusetts.

Estuaries 19: 730–739.

Short, F. T. & E. S. Wyllie, 1996. Natural and humaninduced disturbance of seagrasses. Environmental

Conservation 3: 17–27.

Short, F. T., M. W. Davis, R. A. Gibson & C. F. Zimmermann, 1985. Evidence for phosphorus limitation

in carbonate sediments of the seagrass Syringodium

filiforme. Estuarine Coastal and Shelf Science 20: 419–

430.

Short, F. T., W. C. Dennison & D. G. Capone, 1990.

Phosphorus-limited growth of the tropical seagrass

Syringodium filiforme in carbonate sediments. Marine

Ecology Progress Series 62: 169–174.

Short, F. T., J. Montgomery, C. F. Zimmermann & C. A.

Short, 1993. Production and nutrient dynamics of a

Syringodium filiforme Kutz. seagrass bed in Indian

River Lagoon, Florida. Estuaries 16: 323–334.

Sintes, T., N. Marba`, C. M. Duarte & G. A. Kendrick,

2005. Nonlinear processes in seagrass colonisation

explained by simple clonal growth rules. Oikos 108:

165–175.

Slim, F. J., M. A. Hemminga, E. Cocheret de la Moriniere

& G. van der Velde, 1996. Tidal exchange of macrolitter between a mangrove forest and adjacent seagrass beds (Gazi Bay, Kenya). Netherlands Journal of

Sea Research 30: 119–128.

Stapel, J., T. L. Aarts, B. H. M. van Duynhoven, de J. D.

Groot, P. H. V. van den Hoogen & M. A. Hemminga,

1996. Nutrient uptake by leaves and roots of the

seagrass Thalassia hemprichii in the Spermonde

Archipelago, Indonesia. Marine Ecology Progress

Series 134: 195–206.

Stapel, J., R. Manuntun & M. A. Hemminga, 1997. Biomass loss and nutrient redistribution in an Indonesian

Thalassia hemprichii seagrass bed following seasonal

low tide exposure during daylight. Marine Ecology

Progress Series 148: 251–262.

Strand, J. A. & E. B. Weisner-Stefan, 1996. Wave exposure

related growth of epiphyton: Implications for the

distribution of submerged macrophytes in eutrophic

lakes. Hydrobiologia 325: 113–119.

Teeter, A. M., B. H. Johnson, C. Berger, G. Stelling, N. W.

Scheffner, M. H. Garcia & T. M. Parchure, 2001.

Hydrodynamic and sediment transport modeling with

emphasis on shallow-water, vegetated areas (lakes,

reservoirs, estuaries and lagoons). Hydrobiologia 444:

1–23.

Terrados, J. & C. M. Duarte, 2000. Experimental evidence

of reduced particle resuspension within a seagrass

(Posidonia oceanica L.) meadow. Journal of Experimental Marine Biology and Ecology 243: 45–53.

Terrados, J. & J. D. Ros, 1995. Temperature effects on

photosynthesis and depth distribution of the seagrass

Cymodocea nodosa (Ucria) Ascherson in a Mediterranean coastal lagoon: The Mar Menor (SE Spain).

Marine Ecology 16: 133–144.

Terrados, J., S. R. Agawin-Nona, C. M. Duarte, M. D.

Fortes, N. L. Kamp & J. Borum, 1999. Nutrient limitation of the tropical seagrass Enhalus acoroides (L.)

Royle in Cape Bolinao, NW Philippines. Aquatic

Botany 65: 123–139.

Hydrobiologia (2007) 591:5–24 23

123
Terrados, J., C. M. Duarte, M. D. Fortes, J. Borum, N. S.

R. Agawin, S. Bach, U. Thampanya, N. L. Kamp, W.

J. Kenworthy, H. O. Geertz & J. Vermaat, 1998.

Changes in community structure and biomass of seagrass communities along gradients of siltation in SE

Asia. Estuarine Coastal and Shelf Science 46: 757–

768.

Terrados, J., U. Thampanya, N. Srichai, P. Kheowvongsri,

O. Geertz-Hansen, S. Boromthanarath, N. Panapitukkul & C. M. Duarte, 1997. The effect of increased sediment accretion on the survival and growth

of Rhizophora apiculata seedlings. Estuarine, Coastal

and Shelf Science 45: 1–5.

Touchette, B. W. & J. M. Burkholder, 2000. Review of

nitrogen and phosphorus metabolism in seagrasses.

Journal of Experimental Marine Biology and Ecology

250: 133–167.

Udy, J. W. & W. C. Dennison, 1997. Growth and physiological responses of three seagrass species to elevated

sediment nutrients in Moreton Bay, Australia. Journal

of Experimental Marine Biology and Ecology 217:

253–277.

Udy, J. W., W. C. Dennison, W. J. Lee-Long & L. J.

McKenzie, 1999. Responses of seagrass to nutrients in

the Great Barrier Reef, Australia. Marine Ecology

Progress Series 185: 257–271.

Valiela, I., J. Costa, K. Foreman, J. M. Teal, B. Howes &

D. Aubrey, 1990. Transport of groundwater-borne

nutrients from watersheds and their effects on coastal

waters. Biogeochemistry 10: 177–198

Valiela, I., S. Mazzilli, J. L. Bowen, K. D. Kroeger, M. L.

Cole, G. Tomasky & T. Isaji 2004. ELM, an estuarine

nitrogen loading model: Formulation and verification

of predicted concentrations of dissolved inorganic

nitrogen. Water Air and Soil Pollution 157: 365–391.

van Duin, E. H. S., G. Blom, F. J. Los, R. Maffione, R.

Zimmerman, C. F. Cerco, M. Dortch & P. H. BestElly, 2001. Modeling underwater light climate in

relation to sedimentation, resuspension, water quality

and autotrophic growth. Hydrobiologia 444: 25–42.

van Katwijk, M. M., G.-H. W. Schmitz, A. P. Gasseling &

P. H. van Avesaath, 1999. Effects of salinity and

nutrient load and their interaction on Zostera marina.

Marine Ecology Progress Series 190: 155–165.

van Keulen, M. & M. A. Borowitzka, 2002. Comparison of

water velocity profiles through morphologically dissimailar seagrasses measured with a simple and inexpensive current meter. Bulletin of Marine Science 71:

1257–1267.

Vermaat, J. E. & F. C. A. Verhagen, 1996. Seasonal variation in the intertidal seagrass Zostera noltii Hornem:

coupling demographic and physiological patterns.

Aquatic Botany 52: 259–281.

Vermaat, J. E., N. S. R. Agawin, C. M. Duarte, M. D.

Fortes, N. Marba` & J. S. Uri, 1995. Meadow

maintenance, growth and productivity of a mixed

Philippine seagrass bed. Marine Ecology Progress

Series 124: 215–225.

Vermaat, J. E., N. S. R. F. Agawin, J. S. Uri, D. M. Duarte,

M. Marba` & W. van Vierssen, 1997. The capacity of

seagrasses to survive increased turbidity and siltation;

The significance of growth form and light use. Ambio

26: 499–504.

Vermaat, J. E., J. A. J. Beijer, R. Gijlstra, M. J. M.

Hootsmans, C. J. M. Philippart, N. W. van den Brink

& W. van Vierssen, 1993. Leaf dymanics and standing

stocks of intertidal Zostera noltii Hornem. and Cymodocea nodosa (Ucria) Ascherson on the Banc

d’Arguin (Mauritania). Hydrobiologia 258: 59–72.

Vermaat, J. E., L. Santamaria & P. J. Roos, 2000. Water

flow across and sediment trapping in submerged

macrophyte beds of contrasting growth form. Archiv

fuer Hydrobiologie 148: 549–562.

Walters, K. & D. J. W. Moriarty, 1993. The effects of

complex trophic interactions on a marine microbenthic community. Ecology 74: 1475–1489.

Waycott, M., B. J. Longstaff & J. Mellors, 2005. Seagrass

population dynamics and water quality in the Great

Barrier Reef region: A review and future research

directions. Marine Pollution Bulletin 51: 343–350.

Welsh, D. T, M. Bartoli, D. Nizzoli, G. Castaldelli, S. A.

Riou & P. Viaroli 2000. Denitrification, nitrogen fixation, community primary productivity and inorganicN and oxygen fluxes in an intertidal Zostera noltii

meadow. Marine Ecology Progress Series 208: 65–77.

Widdows, J., A. Blauw, C. H. R. Heip, P. M. J. Herman,

C. H. Lucas, J. J. Middelburg, S. Schmidt, M. D.

Brinsley & H. Verbeek, 2004. Role of physical and

biological processes in sediment dynamics of a tidal

flat in Westerschelde Estuary, SW Netherlands.

Marine Ecology Progress Series 274: 41–56.

Williams, S. L., 1990. Experimental studies of caribbean

seagrass bed development. Ecological Monographs

60: 449–469.

Wolanski, E., 1992. Hydrodynamics of mangrove swamps

and their coastal waters. Hydrobiologia 247: 141–162.

Worm, B. & T. B. H. Reusch, 2000. Do nutrient availability and plant density limit seagrass colonization in

the Baltic Sea? Marine Ecology Progress Series 200:

159–166.

Zimmerman, C. & S. Alberte, 1996. Effects of lights/dark

transition on carbon translocation in eelgrass Zostera

marina seedlings. Marine Ecology Progress Series 136:

309.

Zimmerman, C. & D. Mobley, 1997. Radiative transfer

within seagrass canopies: impact on carbon budgets

and light requirements. Proceedings SPIE 2963: 331–

336.

24 Hydrobiologia (2007) 591:5–24

123