Amphibolis antarctica

About: Amphibolis antarctica is a research topic. Over the lifetime, 82 publications have been published within this topic receiving 8360 citations.

Accelerating loss of seagrasses across the globe threatens coastal ecosystems

Abstract: Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km(2) yr(-1) since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr(-1) before 1940 to 7% yr(-1) since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth.

A Global Crisis for Seagrass Ecosystems

Abstract: Seagrasses, marine flowering plants, have a long evolutionary history but are now challenged with rapid environmental changes as a result of coastal human population pressures. Seagrasses provide key ecological services, including organic carbon production and export, nutrient cycling, sediment stabilization, enhanced biodiversity, and trophic transfers to adjacent habitats in tropical and temperate regions. They also serve as “coastal canaries,” global biological sentinels of increasing anthropogenic influences in coastal ecosystems, with large-scale losses reported worldwide. Multiple stressors, including sediment and nutrient runoff, physical disturbance, invasive species, disease, commercial fishing practices, aquaculture, overgrazing, algal blooms, and global warming, cause seagrass declines at scales of square meters to hundreds of square kilometers. Reported seagrass losses have led to increased awareness of the need for seagrass protection, monitoring, management, and restoration. However, seagrass science, which has rapidly grown, is disconnected from public awareness of seagrasses, which has lagged behind awareness of other coastal ecosystems. There is a critical need for a targeted global conservation effort that includes a reduction of watershed nutrient and sediment inputs to seagrass habitats and a targeted educational program informing regulators and the public of the value of seagrass meadows.

Extreme Temperatures, Foundation Species, and Abrupt Ecosystem Change: An Example from an Iconic Seagrass Ecosystem

Abstract: Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework.

Decline of seagrasses

Abstract: Other chapters underline the importance of seagrasses to our nearshore ecosystems, for example in supporting fish populations and modifying sediment movement wave energy, and it is clear that seagrasses are important components of major Australian ecosystems. While in the natural environment a variety of factors affect the dynamic processed involved in the establishment, maintenance and erosion of seagrass meadows in an unstable, often high-energy environment, one can only view with concern the more or less irreversible loss of meadows, often over extensive areas, which have taken place as a consequence of man's activities. It is this 'cultural' decline in seagrass meadows which is the subject of this chapter, which addresses case studies drawn from several States, reviews mechanisms which may be responsible for seagrass decline, and addresses management considerations. The most extensively documented example of seagrass decline on the western coast has occurred in Cockburn Sound, a marine embayment 30kmsouth of the capital city, Perth (Figure 12.1). A decision was taken to locate a major industrial development around the Sound, which is the only extensive, sheltered, deep-water area close to Perth on an otherwise inhospitable and high-energy coastline. A basin almost 20m deep, the Sound is protected on the east by Garden Island, and on the north and south by shallow banks covered by 3-5 m of water; these features restrict the exchange of water between the basin and the open ocean. A dredged channel through the northern bank allows access by deep-draught vessels. Development began in 1954. On the mainland several major industries were established, including an oil refinery, blast furnace and steel-rolling mill, superphosphate factory, and processing plants for alumina and nickel. Garden Island became the site for a major naval facility. Industrial effluents began to enter the Sound, and to the north a sewage treatment plant began discharging in the mid 1960's. Ten species of seagrasses were associated with the Sound. Posidonia sinuosa (formerly included in Posidonia australis) formed extensive meadows, with Posidonia australis, Amphibolis antarctica and Amphibolis griffithii at the edges of P. sinuosa meadows or in more turbulent, disturbed areas. Posidonia angustifolia is included tentatively; though no longer found there it was probably present around limestone rocks as it is in adjoining waters.