Seagrass meadows in a globally changing environment

Seagrass meadows are valuable ecosystem service providers that are now being lost globally at an unprecedented rate, with water quality and other localised stressors putting their future viability in doubt. It is therefore critical that we learn more about the interactions between seagrass meadows and future environmental change in the anthropocene. This needs to be with particular reference to the consequences of poor water quality on ecosystem resilience and the effects of change on trophic interactions within the food web. Understanding and predicting the response of seagrass meadows to future environmental change requires an understanding of the natural long-term drivers of change and how these are currently influenced by anthropogenic stress. Conservation management of coastal and marine ecosystems now and in the future requires increased knowledge of how seagrass meadows respond to environmental change, and how they can be managed to be resilient to these changes. Finding solutions to such issues also requires recognising people as part of the social-ecological system. This special issue aims to further enhance this knowledge by bringing together global expertise across this field. The special issues considers issues such as ecosystem service delivery of seagrass meadows, the drivers of long-term seagrass change and the socio-economic consequences of environmental change to seagrass

Seagrass communities in the Shoalwater Bay region, Queensland: Spring (September) 1995 and Autumn (April) 1996

The Commonwealth Commission of Inquiry into Shoal water Bay (Commission of Inquiry 1994) recommended equal priority be given to conservation and defence force training use in the Shoalwater Bay area, and that integrated management plans be developed for the terrestrial and marine environments. The Great Barrier Reef Marine Park Authority (GBRMPA) was given responsibility for developing management plans for a special Shoalwater Bay Marine Park. The GBRMPA commissioned a number of studies of marine resource inventories and use patterns in the Shoalwater Bay area for marine park zone planning. The present Spring and Autumn baseline surveys of seagrass resources is one of these studies. Seagrasses have seasonal differences in distribution and abundance, so two baseline surveys Spring (pre-wet) and Autumn (post-wet) - were recommended. This report presents the results of the two surveys conducted September 1995 and April 1996. The objectives were: to map the distribution of seagrass meadows in Shoa/water Bay during the Spring and Autumn periods; to estimate seagrass species biomass for the major seagrass meadows; to identify juvenile prawn and fish species present on selected seagrass areas; and to provide quantitative data 011 seagrass communities of Shoalwater Bay for use as a baseline for future monitoring of seagrass species composition, area or biomass

Seagrasses between Cape York and Hervey Bay, Queensland, Australia

The area of seagrasses in waters adjacent to the Queensland coast between Cape York and Hervey Bay is approximately 4000 km2. Seagrasses were found near estuaries, in coastal bays and associated with islands, at sites that provided shelter from the south-easterly trade winds and Pacific Ocean swells. Of the seagrass meadows mapped, 37% had a bottom vegetation cover greater than 50%. Two large continuous areas (total of approximately 2500 km2) of seagrass of predominantly Halophila species were found in deep water in Hervey Bay and between Barrow Point and Lookout Point and may be part of a much larger area of deep-water seagrass habitat not yet surveyed in the Great Barrier Reef province. Fourteen seagrass species were found in the surveyed region, and most were typical of the northern Australian and Indo-West Pacific region. The opportunistic Halophila and Halodule species were most common, with Halophila ovalis (R. Br.) Hook. f. and Halodule uninervis (Forsk.) Aschers. each being found in more than 15% of samples. High species richness occurred at depths of less than 6 m, predominantly in sheltered bays at coastal and island locations. Low species richness at estuary- associated sites may be due to stresses caused by low salinity during monsoonal runoff periods or exposure at low tides. Zostera capricorni Aschers. was restricted to these areas and may have a competitive advantage over other species with lesser tolerance to varying salinity. Species richness decreased with an increase in both latitude and depth. The latitudinal limits of recorded distributions for some of these tropical seagrasses were confirmed. Seagrass biomass decreased with increasing depth, but parameters of seagrass abundance showed no correlation with latitude, being dependent on a complex of site-related factors. High seagrass biomass occurred at sheltered sites, including estuary-associated, coastal-bay and island-associated sites. The maximum recorded above-ground biomass was 102.9 g m-2 for Zostera capricorni at Upstart Bay. Shoot densities reached 13 806 shoots m-2 for Halophila ovalis at Escape River, and the highest leaf area index was 1.81 for Zostera capricorni at Upstart Bay

Monitoring Oyster Point seagrasses : 1995 to 1999

In the present report, an assessment of changes in seagrass distribution and abundance since the baseline (November 1995) and previous monitoring surveys of December 1997 and November 1998 is included. We provide a quantification of changes between years and comment on the possible impacts of the dredging program

Seagrass and marine resources in the Dugong protection areas of Upstart Bay, Newry Region, Sand Bay, Llewellyn Bay, Ince Bay and the Clairview Region, April/May 1999 and October 1999

The Marine Plant Ecology Group (Queensland Fisheries Service, Queensland Department of Primary Industries) was commissioned by the Great Barrier Reef Marine Park Authority to undertake two (one autumn and one spring) detailed seagrass surveys of the Dugong Protection Areas in Upstart Bay, Newry region, Sand Bay, Llewellyn Bay, Ince Bay, and a reconnaissance survey in the Clairview region. The information gathered from these surveys enhances the understanding and subsequent management of seagrass resources for fisheries and as dugong feeding habitats

Baseline survey of Hinchinbrook region seagrasses - October (spring) 1996

Current coastal zone management issues in the Hinchinbrook region include protection of fisheries habitats, dugong habitat areas and increases in aquaculture, agriculture and tourist operations. A regional coastal management plan which is being developed, also requires detailed information on seagrass resources for the coastal zone from Dunk Island in the north, to Cleveland Bay in the south. Decreases in estimates of dugong abundance in the southern half of the Great Barrier Reef region since the 1980's have also prompted the need for detailed baseline and monitoring surveys of seagrasses in this and other regions

Vegetative fragment production as a means of propagule dispersal for tropical seagrass meadows

Background and aims: Long distance dispersal (LDD) contributes to the replenishment and recovery of tropical seagrass habitats exposed to disturbance, such as cyclones and infrastructure development. However, our current knowledge regarding the physical attributes of seagrass fragments that influence LDD predominantly stems from temperate species and regions. The goal of this paper is to measure seagrass fragment density and viability in two tropical species, assessing various factors influencing their distribution. Methods: We measured the density and viability of floating seagrass fragments for two tropical seagrass species (Zostera muelleri and Halodule uninervis) in two coastal seagrass meadows in the central Great Barrier Reef World Heritage Area, Australia. We assessed the effect of wind speed, wind direction, seagrass growing/senescent season, seagrass meadow density, meadow location and dugong foraging intensity on fragment density. We also measured seagrass fragment structure and fragment viability; i.e., potential to establish into a new plant. Key results: We found that seagrass meadow density, season, wind direction and wind speed influenced total fragment density, while season and wind speed influenced the density of viable fragments. Dugong foraging intensity did not influence fragment density. Our results indicate that wave action from winds combined with high seagrass meadow density increases seagrass fragment creation, and that more fragments are produced during the growing than the senescent season. Seagrass fragments classified as viable for Z. muelleri and H. uninervis had significantly more shoots and leaves than non-viable fragments. We collected 0.63 (±0.08 SE) floating viable fragments 100 m−2 in the growing season, and 0.13 (±0.03 SE) viable fragments 100 m−2 in the senescent season. Over a third (38%) of all fragments collected were viable. Conclusion: There is likely to be a large number of viable seagrass fragments available for long distance dispersal. This study's outputs can inform dispersal and connectivity models that are used to direct seagrass ecosystem management and conservation strategies

Seagrass spatial data synthesis from north-east Australia, Torres Strait and Gulf of Carpentaria, 1983 to 2022

The Gulf of Carpentaria and Torres Strait in north-eastern Australia support globally significant seagrass ecosystems that underpin fishing and cultural heritage of the region. Reliable data on seagrass distribution are critical to understanding how these ecosystems are changing, while managing for resilience. Spatial data on seagrass have been collected since the early 1980s, but the early data were poorly curated. Some was not publicly available, and some already lost. We validated and synthesized historical seagrass spatial data to create a publicly available database. We include a site layer of 48,612 geolocated data points including information on seagrass presence/absence, sediment, collection date, and data custodian. We include a polygon layer with 641 individual seagrass meadows. Thirteen seagrass species are identified in depths ranging from intertidal to 38 m below mean sea level. Our synthesis includes scientific survey data from 1983 to 2022 and provides an important evidence base for marine resource management

Interacting new agegraphic viscous dark energy with varying GG

We consider the new agegraphic model of dark energy with a varying gravitational constant, $G$, in a non-flat universe. We obtain the equation of state and the deceleration parameters for both interacting and noninteracting new agegraphic dark energy. We also present the equation of motion determining the evolution behavior of the dark energy density with a time variable gravitational constant. Finally, we generalize our study to the case of viscous new agegraphic dark energy in the presence of an interaction term between both dark components.Comment: 12 pages, accepted for publication in IJTP (2010

Heliolatitude and time variations of solar wind structure from in situ measurements and interplanetary scintillation observations

The 3D structure of solar wind and its evolution in time is needed for heliospheric modeling and interpretation of energetic neutral atoms observations. We present a model to retrieve the solar wind structure in heliolatitude and time using all available and complementary data sources. We determine the heliolatitude structure of solar wind speed on a yearly time grid over the past 1.5 solar cycles based on remote-sensing observations of interplanetary scintillations, in situ out-of-ecliptic measurements from Ulysses, and in situ in-ecliptic measurements from the OMNI-2 database. Since the in situ information on the solar wind density structure out of ecliptic is not available apart from the Ulysses data, we derive correlation formulae between solar wind speed and density and use the information on the solar wind speed from interplanetary scintillation observations to retrieve the 3D structure of solar wind density. With the variations of solar wind density and speed in time and heliolatitude available we calculate variations in solar wind flux, dynamic pressure and charge exchange rate in the approximation of stationary H atoms.Comment: Accepted for publication in Solar Physic