Richard Brinkman

Surface wave propagation in mangrove forests

Mangroves are a special form of vegetation as they exist at the boundary of terrestrial and marine environment. They have a special role in supporting fisheries and in the stabilizing the tropical coastal zones. Biochemical and trophodynamic processes in the mangroves are strongly linked to water movement, due to tides and waves. In this paper we present the theoretical attempt to predict the attenuation of wind-induced random surface waves in the mangrove forest. The energy dissipation in the frequency domain is determined by treating the mangrove forest as a random media with certain characteristics determined using the geometry of mangrove trunks and their locations. Initial nonlinear governing equations are linearized using the concept of minimalization in the stochastic sense and interactions between mangrove trunks and roots have been introduced through the modification of the drag coefficients. The resulting rate of wave energy attenuation depends strongly on the density of the mangrove forest, diameter of mangrove roots and trunks, and on the spectral characteristics of the incident waves. Examples of numerical calculations as well as preliminary results from observation of wave attenuation through mangrove forests at Townsville (Australia) and Iriomote Island (Japan) are given.

On the surface circulation in the western Coral Sea and residence times in the Great Barrier Reef

Surface velocity observations from satellite tracked drifters made between 1987 and 2008 were used to resolve the surface circulation of the western Coral Sea, west of 158°E, and the Great Barrier Reef (GBR). The mean surface current map depicts well the major circulation patterns of the region, such as the position of the north Vanuatu and north Caledonia jets (NVJ and NCJ) and the western boundary currents. The North Queensland Current (NQC) and the East Australian Current (EAC) are well defined, flowing at speeds greater than 50 cm s−1 to the north, south of 15°S and 19°S, respectively. The NQC/EAC is mainly formed by the NVJ/NCJ flows, respectively. The presence of the Queensland Plateau greatly affects the westward flow, causing a zone of weak and highly variable currents that extends from 15°S to 18°S between the Queensland Plateau and the GBR shelf. Of the 235 drifters that crossed the western Coral Sea, 75 entered the GBR. Analysis of the drifter trajectories inside the GBR reveals the presence of a northwestward circulation at speeds of 22 cm s−1 north of 18°S and 0.5 cm s−1 south of 18°S. Drifter travel times used to evaluate the water residence times within the GBR indicate residence times of a few weeks for most of the lagoon.

Monitoring, Predicting, and Managing One of the Seven Natural Wonders of the World

T he Great Barrier Reef (GBR) is a 2,000-km long reef and lagoon complex. It is a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site covering 347,800 km 2 , sandwiched between Australia’s northeast coastline and the Coral Sea. It includes an estimated 2,800 reefs, with an average depth of 35 m. One of the seven Natural Wonders of the World, the GBR is the world’s largest coral reef and a significant part of Australia’s natural heritage and economy. For example, a 2007 report by Access Economics for the Great Barrier Reef Marine Park Authority found that the total economic contributions to Australia from tourism, commercial fishing, and recreational activities in the GBR catchment area totaled more than

The distribution and abundance of dictyoceratid sponges in relation to hydrodynamic features: identifying candidates and environmental conditions for sponge aquaculture

AUS 5.7 billion (approximately

Tropical Marginal Seas: Priority Regions for Managing Marine Biodiversity and Ecosystem Function

US 5.9 billion) in 2005–06. The report also found that these activities accounted for a direct and indirect national contribution of 66,000 full-time equivalent jobs.

Seacage aquaculture in a World Heritage Area: the environmental footprint of a Barramundi farm in tropical Australia.

The distribution and abundance of dictyoceratid sponges was surveyed to a depth of 20 m at eleven locations within the Palm Island Group, Great Barrier Reef (GBR), Australia. These surveys were related to prevailing hydrodynamic conditions to identify candidates and environmental conditions for sponge aquaculture. Locations were classified as sheltered, intermediate and exposed using quantitative wave exposure and current force models. The species richness of dictyoceratid sponges was high with ten taxa, but the abundance of most species was low with patchy distributions. Two species, Coscinoderma sp. and Rhopaloeides odorabile, were abundant, and detailed surveys of these species were conducted at seven locations representing common habitats within the Palm Island Group. Coscinoderma sp. was present at all locations and although abundances differed significantly across locations, this was not related to hydrodynamic conditions. In contrast, R. odorabile was only present at exposed locations with low abundance. The higher abundance and broad distribution of Coscinoderma sp. supports its selection as an aquaculture candidate. In contrast, R. odorabile was less abundant and was restricted to high-energy environments making aquaculture more problematic. The present study demonstrates the importance of ecological data in the decision-making process for new species aquaculture.

Workshop on the ecosystem and fisheries of the Coral Sea: an Australian perspective on research and management

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems-coral reefs and emergent atolls, deep benthic systems, and pelagic biomes-and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence-from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas-but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.

Hydrology and Biogeochemistry of Mangrove Forests

The fate of aquaculture wastes from a seacage farm within a pristine mangrove environment was studied. Seasonal and tidal differences were most important in determining water quality within receiving waters and obscured any nutrient enrichment effect by the farm. Farm wastes added significantly to the N budget status of the creek system, but overall water quality conformed to Queensland EPA Water Quality standards. Mangrove trees throughout the creek system contained (15)N signatures traceable to aquaculture feeds, but the footprint of the farm itself was best indicated by the ratio of Zn:Li in sediments. The creek became hypoxic (<2 mgl(-1)) during wet season low tides. Consequently, we recommended monitoring of water-column oxygen concentrations to warn of hypoxic conditions threatening to fish health, as well as Zn:Li ratios in sediment accumulation zones to determine the area of influence of the farm.

Intrusive upwelling in the Central Great Barrier Reef

This report summarizes a workshop on the Coral Sea to determine key research findings and identify the research gaps needed to support sustainable management of a proposed Coral Sea Marine Reserve. Key research questions included determining the connectivity of apex predators with the broader southwest Pacific Ocean, and assessing the regions’ biodiversity in relation to seabed topography and oceanographic processes. The workshop concluded noting the importance of engaging surrounding countries in maintaining the sustainability and uniqueness of the Coral Sea.

Chapter 15 Merging scales in models of water circulation: perspectives from the great barrier reef

Situated at the interface between land and sea, the structure and function of mangrove forests, perhaps more than any other forest type, are closely linked to hydrology. For a part of every day, tidal waters flood and ebb through these coastal forests of low latitudes, and in most locations are influenced by waves and other circulatory processes. The pantropical distribution of mangroves is delimited by the major ocean currents and the 20°C winter isotherm of seawater. Mangroves are limited globally by temperature but rainfall, tides, waves, and river flow are of fundamental importance at the regional and local scale.