Evidence for short-circuiting of the detritus cycle of seagrass beds by the green turtle, Chelonia mydas L.

Thayer, Gordon W.; Engel, David W.; Bjorndal, Karen A.

doi:10.1016/0022-0981(82)90090-9

Cited by 52 publications

(38 citation statements)

References 11 publications

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“…Abundant green turtles closely crop turtlegrass and greatly reduce the flux of organic matter and nutrients to sediments (59)(60)(61)(62)68). In the near absence of green turtles today, turtlegrass beds grow longer blades that baffle currents, shade the bottom, start to decompose in situ, and provide suitable substrate for colonization by the slime molds that cause turtlegrass wasting disease (65).…”

Section: Tropical and Subtropical Seagrass Bedsmentioning

confidence: 99%

Historical Overfishing and the Recent Collapse of Coastal Ecosystems

Jackson

Kirby

Berger

et al. 2001

Science

5,267

3,744

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Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.Few modern ecological studies take into account the former natural abundances of large marine vertebrates. There are dozens of places in the Caribbean named after large sea turtles whose adult populations now number in the tens of thousands rather than the tens of millions of a few centuries ago (1, 2).

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Section: Tropical and Subtropical Seagrass Bedsmentioning

confidence: 99%

Historical Overfishing and the Recent Collapse of Coastal Ecosystems

Jackson

Kirby

Berger

et al. 2001

Science

5,267

3,744

View full text Add to dashboard Cite

show abstract

“…Green turtles Chelonia mydas are important grazers in a number of seagrass communities throughout the tropics and subtopics, where they play a role in detrital cycles and affect the growth patterns of seagrass (Thayer et al 1982, Bjorndal 1997, Bjorndal et al 2000, Aragones 2000, Aragones & Marsh 2000, Bjorndal & Jackson 2003. Although their role in marine ecosystems is poorly known, loggerhead turtles Caretta caretta may influence benthic communities through trophic interactions or benthic disturbance (e.g.…”

Section: Introductionmentioning

confidence: 99%

Biology of sea turtles under risk from tiger sharks at a foraging ground

Heithaus

Frid²,

Wirsing³

et al. 2005

Mar. Ecol. Prog. Ser.

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It is important to understand the population structure and space use of sea turtles because of their potential effects on the dynamics of nearshore ecosystems. Much of our current understanding is skewed because the ecology of sea turtles on their foraging grounds is known best from areas where there are, or have been, major human impacts. We studied green Chelonia mydas and loggerhead Caretta caretta sea turtles on the relatively pristine feeding ground of Shark Bay, Western Australia, where tiger sharks Galeocerdo cuvier are a major mortality agent. Recapture rates were lower for green than for loggerhead turtles, possibly reflecting a larger population rather than low site fidelity for greens. The sex ratio of loggerhead turtles was not significantly different from 1:1, whereas green turtles showed a strong female bias. Size distributions of both species were skewed towards larger (and presumably older) individuals relative to a human-impacted feeding ground in eastern Australia. Body condition varied temporally for green turtles, but not for loggerhead turtles, possibly due to longer distances traveled to nesting beaches by green turtles. Rates of shark-inflicted injuries were higher for loggerhead turtles, especially males, than for greens. Sublethal effects of these injuries were not evident. There are notable differences between sea turtles threatened primarily by tiger sharks in Shark Bay and populations on feeding grounds where historical and current mortality causes are anthropogenic. We conclude that without baseline data from relatively pristine habitats our understanding of human impacts on sea turtle populations suffers from a limited scope.

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“…3). The effects of marine herbivores may include stimulated production of seagrass (Valentine et al, 1997;Moran and Bjorndal, 2005;Vonk et al, 2008b;Christianen et al, 2012), changes in seagrass meadow structure (Lal et al, 2010), and the reduction of the flux of organic matter and nutrients to sediments and plants (by short circuiting the detrital cycle; (Thayer et al, 1982;Vonk et al, 2008a) or their export to nearby habitats (Christianen et al, 2012). In salt marshes and aquatic ecosystems, an additional effect of herbivores is the return of nutrients through faeces and urine (Bazely and Jefferies, 1985;Hik et al, 1991;Frank et al, 2000), though in seagrass grazed by turtles this effect is reduced by nutrient transport to turtle resting areas (Christianen et al, 2012).…”

Section: Ecosystem Consequences Of Herbivorymentioning

confidence: 99%

Herbivory on freshwater and marine macrophytes: A review and perspective

et al. 2016

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on freshwater and marine macrophytes: a review and perspective.Aquatic Botany http://dx.doi.org/10. 1016/j.aquabot.2016.04.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractUntil the 1990s, herbivory on aquatic vascular plants was considered to be of minor importance, and the predominant view was that freshwater and marine macrophytes did not take part in the food web: their primary fate was the detritivorous pathway. In the last 25 years, a substantial body of evidence has developed that shows that herbivory is an important factor in the ecology of vascular macrophytes across freshwater and marine habitats. Herbivores remove on average 40-48% of plant biomass in freshwater and marine ecosystems, which is typically 5-10 times greater than reported for terrestrial ecosystems. This may be explained by the lower C:N stoichiometry found in submerged plants.Herbivores affect plant abundance and species composition by grazing and bioturbation and therewith alter the functioning of aquatic ecosystems, including biogeochemical cycling, carbon stocks and primary production, transport of nutrients and propagules across ecosystem boundaries, habitat for other organisms and the level of shoreline protection by macrophyte beds.With ongoing global environmental change, herbivore impacts are predicted to increase.There are pressing needs to improve our management of undesirable herbivore impacts on macrophytes (e.g. leading to an ecosystem collapse), and the conflicts between people 4 associated with the impacts of charismatic mega-herbivores. While simultaneously, the longterm future of maintaining both viable herbivore populations and plant beds should be addressed, as both belong in complete ecosystems and have co-evolved in these long before the increasing influence of man. Better integration of the freshwater, marine, and terrestrial herbivory literatures would greatly benefit future research efforts.

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Evidence for short-circuiting of the detritus cycle of seagrass beds by the green turtle, Chelonia mydas L.

Cited by 52 publications

References 11 publications

Historical Overfishing and the Recent Collapse of Coastal Ecosystems

Historical Overfishing and the Recent Collapse of Coastal Ecosystems

Biology of sea turtles under risk from tiger sharks at a foraging ground

Herbivory on freshwater and marine macrophytes: A review and perspective

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