Decline and Recovery of Seagrass Ecosystems—The Dynamics of Change

Walker, Diana; Kendrick, Gary A.; McComb, A.J.

doi:10.1007/1-4020-2983-7_23

Cited by 35 publications

(40 citation statements)

References 49 publications

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“…Other marine systems include seagrass meadows, which form unique, productive and diverse ecosystems (Bostrom et al, 2006;Duarte and Chiscano, 1999). They are affected by fragmentation through dredging and boating effects, eutrophication, extreme weather events, urchin grazing and wasting disease (Bostrom et al, 2006;Orth et al, 2006;Rasmussen, 1977; Continued BOX 1 Habitat Fragmentation in Aquatic Ecosystems-cont'd McComb, 1992;Walker et al, 2006). While many studies suggest that fragmentation of seagrass meadows has limited (Frost et al, 1999;Hirst and Attrill, 2008;MacReadie et al, 2009), inconsistent (Bell et al, 2001) or even positive (Eggleston et al, 1998;Hovel and Lipcius, 2001) impacts on epifaunal diversity and abundance, fragmentation beyond a threshold level can lead to rapid declines in species diversity and abundance (Reed and Hovel, 2006).…”

Section: Box 1 Habitat Fragmentation In Aquatic Ecosystemsmentioning

confidence: 99%

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

Hagen

Kissling

Rasmussen

et al. 2012

Advances in Ecological Research

361

352

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Section: Box 1 Habitat Fragmentation In Aquatic Ecosystemsmentioning

confidence: 99%

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

Hagen

Kissling

Rasmussen

et al. 2012

Advances in Ecological Research

361

352

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“…Coastal seagrass coverage is continuing to decline worldwide (Walker et al 2006, Waycott et al 2009). Eutrophication in the form of increased water column nutrients from anthropogenic inputs has been implicated as one of the major causes (Ralph et al 2006, Burkholder et al 2007.…”

Section: Introductionmentioning

confidence: 99%

Nutrient exposure causes epiphytic changes and coincident declines in two temperate Australian seagrasses

Bryars¹,

Collings²,

Miller³

2011

Mar. Ecol. Prog. Ser.

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We undertook a long-term (27 mo) field experiment to test if a chronic increase in water column nutrients could cause a decline in 2 temperate Australian seagrasses and if this decline could be linked to nutrient-mediated changes in epiphytes. Two seagrasses, Amphibolis antarctica and Posidonia sinuosa, were exposed to minor increases (~2 to 5×) in nutrient (N, P) concentrations utilising slow-release fertiliser over a 15 mo period at a shallow (~2 m depth), oligotrophic marine site in Gulf St Vincent, South Australia. Fertiliser had a significant detrimental effect on biomass, density, and canopy height in both seagrasses. Moreover, the seagrass biomass reductions coincided with increased epiphyte loads and changes in epiphyte composition. After a 12 mo recovery period, epiphyte loads in the fertiliser treatments had returned to levels comparable to the control, but the fertiliser-treated seagrasses had not recovered. While the precise mechanism of seagrass decline is still unclear, our results have demonstrated that (under certain circumstances) chronic, yet minor, increases in water column nutrient concentrations can cause the slow decline of Amphibolis and Posidonia spp. Furthermore, while future management decisions regarding anthropogenic nutrient discharges into seagrass ecosystems should be assessed on a case-by-case basis, our results and those of other workers investigating large-scale losses of Amphibolis and Posidonia in southern Australia indicate that extreme caution must be applied where these seagrasses occur in shallow, sheltered oligo trophic marine environments.

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“…For most of the experiment, eelgrass shoot density varied seasonally as has previously been described for populations not influenced by algal blooms (Duarte et al 2006, Walker et al 2006, with peak densities in the summer and lowest in the winter (Fig. 1).…”

Section: Seasonal and Interannual Variation In Control Plotsmentioning

confidence: 53%

“…Although some reductions in shoot density may alleviate intra-specific competition for light and nutrients, large declines in shoot density can lead to sediment re-suspension and increased turbidity (Hasegawa et al 2008), i.e. additional stresses that can cause further eelgrass decline (McGlathery 2001, Walker et al 2006. Also, the timing and duration of blooms are likely to be important.…”

Section: Bloom Size Timing and Durationmentioning

confidence: 99%

Multi-year study of the effects of Ulva sp. blooms on eelgrass Zostera marina

Olyarnik

Stachowicz²

2012

Mar. Ecol. Prog. Ser.

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Macroalgal blooms have contributed to declines in foundation species such as corals and seagrasses across the globe. Most studies of macroalgal bloom effects on seagrasses focus on the short-term effects, and have been conducted in locations that already begun the shift to macroalgal dominance, usually due to eutrophication. Our goal was to determine the degree to which the timing and magnitude of ephemeral, green macroalgal blooms (Ulva sp.) vary in Bodega Bay, California, USA, where there is little evidence for eutrophication, and how such blooms affect eelgrass Zostera marina. Over 38 mo, we conducted (1) an unmanipulated control treatment, and 3 manipulative treatments: (2) Ulva removal, (3) ambient Ulva, and (4) doubleambient Ulva ('2×'). We observed 4 blooms of varying magnitude and duration, ranging from < 0.5 to > 4 kg m −2. It was only during the largest bloom in 2006 (peak density 8 times that of the smallest observed bloom) that we saw a significant effect on eelgrass, resulting in declines in shoot density of > 50% that persisted for 4 to 6 mo. During this time, the 2× treatment reduced shoot biomass by up to 90%, an effect that persisted for up to 9 mo. Ulva did not affect rates of individual shoot growth, reproductive shoot density, epiphyte load, or sediment organic content at any time during the experiment, suggesting the effect occurs through shoot mortality and reduced shoot production. Interannual variation in the magnitude timing and duration of algal blooms is large and can dramatically alter the effects of blooms on eelgrass. These factors must be considered when interpreting the results of experimental algal additions.

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Decline and Recovery of Seagrass Ecosystems—The Dynamics of Change

Cited by 35 publications

References 49 publications

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

Nutrient exposure causes epiphytic changes and coincident declines in two temperate Australian seagrasses

Multi-year study of the effects of Ulva sp. blooms on eelgrass Zostera marina

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