R.J. Morrison

Reef-island accretion and soil development on Makin, Kiribati, central Pacific

The late Holocene accretionary history of reef islands on Makin, the northernmost table reef of the Gilbert atoll chain, western Kiribati, has been reconstructed based on conventional radiocarbon dating of coral shingle and bulk sand samples, and AMS radiocarbon dating of individual grains. Makin is geomorphologically and sedimentologically simple, comprising one main island with only a minor residual lagoon, and composed of sand dominated by the reef-flat foraminifera Calcarina spengleri, Amphistegina lobifera and Baculogypsina sphaerulata. Deposition commenced in mid platform around 2500 years ago; in situ fossil coral (Heliopora) dated at 2400±80 years BP indicates that sea level was 0.4–0.5 m above present at that time. Progradation occurred progressively to westward at a relatively constant rate of 200–300 m ka−1. However, progradation was interrupted on the eastern side by lagoon encapsulation around 1400 years ago. The soil and vegetation characteristics are uniform over most of the reef islands as a result of clearance and the planting and maintenance of coconuts, and do not reflect reef-island depositional history. Remnant stands of Pisonia forest, with an associated phosphatic soil, are not related to any particular geomorphological feature, or period of deposition. The reef islands are continuing to accrete as a result of production of foraminifera on the reef flat.

Impact of a coastal dump in a tropical lagoon on trace metal concentrations in surrounding marine biota : A case study from Saipan, Commonwealth of the Northern Mariana Islands (CNMI)

Water and Environmental Research Institute of the Western Pacific, University of Guam, Mangilao, Guam 96923, USA b School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia Division of Environmental Quality, Commonwealth of the Northern Mariana Islands, Saipan, MP 96950, USA Coastal Resources Management Office, Commonwealth of the Northern Mariana Islands, Saipan, MP 96950, USA The objective of BASELINE is to publish short communications on different aspects of pollution of the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to ‘Baseline—The New Format and Content’ (Mar. Pollut. Bull. 42, 703–704).

Changes in the Marine Environment of Port Kembla Harbour, NSW, Australia, 1975–1995: A Review

Data on water quality, sediment quality and aquatic organisms in Port Kembla Harbour from the 1970s to the 1990s are reviewed. In the 1970s, the marine environment of Port Kembla Harbour was in poor condition as a result of pollution from heavy industries. Elevated concentrations of pollutants were found in water, sediment and fish in the harbour; aquatic biodiversity was limited and many fish kills were reported. With the implementation of pollution reduction programs (required by legislation changes) by the industries surrounding the harbour since the 1970s, pollution in the harbour has been reduced dramatically, and the quality of the marine environment of the harbour has noticeably improved. Large reductions in the concentrations of certain toxic wastes and heavy metals in water have occurred. Marine life has returned to the whole harbour (parts were described in 1977 as abiotic). Contaminants in fish have decreased. Despite this achievement, however, there is still considerable room for improvement in the quality of the marine environment of the harbour.

Contamination of Suva harbour, Fiji

Abstract Suva, the capital of Fiji, is a major commercial centre for the Pacific Islands, and is a rapidly expanding city both in terms of population and industrialization. Recent developments have had major impacts on the adjacent harbour. This paper reports the results of studies on two areas within the harbour—one adjacent to the major urban dump and the other close to a lead acid accumulator battery. Sediments and shell-fish were shown to be contaminated with metals in both areas, with the zone around the battery factory having sediment metal concentrations high enough to be considered a hazardous waste site. Results from the area around the dump indicated the movement of metals away from the dump into the surrounding marine environment. Similar impacts are expected in other Pacific Islands and developing countries where urban waste disposal sites are usually on the coast.

Inorganic nutrient and oxygen fluxes across the sediment–water interface in the inshore macrophyte areas of a shallow estuary (Lake Illawarra, Australia)

Rates of inorganic nutrient and oxygen fluxes, and gross community primary productivity were investigated using incubated cores in July, August and September 2001, in a seagrass meadow of Lake Illawarra, a barrier estuary in New South Wales, Australia. The results indicated that rates of gross primary productivity were high, varying from C = 0.62 to 1.89 g m−2 d−1; low P/R ratios of 0.28–0.48 define the system as heterotrophic and indicate that more carbon is respired than is produced. In order to determine the effect of macroalgae on O2 and nutrient fluxes, measurements were also conducted on cores from which the macroalgae had been removed. The results showed that the O2 fluxes during light incubations were significantly lower in the cores without macroalgae (P<0.01), indicating that macroalgae could be a significant contributor to the primary production in the lake. In general, nutrient fluxes showed a typical diurnal variation with an efflux from sediments in the dark and a reduced efflux (or uptake) in the light. Dissolved inorganic nitrogen (NO2−+ NO3−+NH4+) net fluxes were directed from the sediments towards the water column and dominated by the NH4+ fluxes (>80%). NO2−+ NO3− and o-P fluxes were always very low during the sampling period. The increasing tendency of net nutrient effluxes, especially NH4+ from July to September, is consistent with the increase of the water temperature and seagrass biomasses. However, in September, significantly lower light, dark and net NH4+ effluxes were found in the cores with macroalgae (SA-sediments) compared with the cores without macroalgae (S-sediments). These results support the hypothesis that actively-growing dense macroalgal mats (i.e., algal blooms in September) may act as a filter reducing the flux of nutrients to the water column.

Trace Element Studies in Laucala Bay, Suva, Fiji

The trace metal distribution in the sediments of Laucala Bay, a coastal lagoon with a barrier reef and significant freshwater input, adjacent to Suva, the capital of Fiji (150,000 people), was studied from the point of view of assessing the significance of anthropogenic sources relative to natural ones. Surface sediments from 25 sites in the Bay were analysed for particle size distribution, organic carbon and major (Si, Al, Fe, Ca, Mg) and trace metal (Mn, Zn, Cu, Pb, Cd, Hg) contents. Suspended sediments from one site and shellfish samples from five sites were also analysed. The sediments were found to be mostly of terrigenous origin. Particle size distribution, organic carbon and major elemental composition of the sediments were generally related to location within the Bay. A significant natural source of trace metals in the sediments is the suspended solids transported into the Bay by rivers. The spatial distribution of trace metals could not be fully explained by the particle size distribution and mineral composition of the sediments. Contributions from anthropogenic sources were also suspected, but the degree of enrichment from such sources is not great at the present time.

Marine pollution in the Arafura and Timor Seas

Abstract The management of the Arafura and Timor Seas, which form a major part of the maritime boundary between Australia and Indonesia, is of significant economic and environmental importance to both countries. Information available indicates that much of the marine environment in the region is in near pristine condition. Increasing pressure is being placed on this environment through expanding shipping and fishing activity, urban and industrial development including mining, port expansion, oil and gas exploration and production, changing land use in catchments, and tourism. These activities are affecting water and sediment quality, habitats and marine biodiversity. This paper review the available information on marine pollution in the Arafura and Timor Seas, including assessments based on physical, social and economic features of the region. A number of proposals for maintaining the high quality of this environment are presented, including a well planned monitoring program covering key points in the region and an expanded oceanographic information base which would provide an early indication of changing pollution conditions.

Potassium Studies on Some Sugarcane Growing Soils in Fiji

This study investigated the potassium (K) status of sugarcane growing soils in Fiji, using samples taken from fields under cultivation and also from sites that had not been cultivated for at least 30 years. Five sites were on highly weathered oxyhydroxide soils where the total K contents and K retention capacities were generally low. The two less weathered soils containing significant amounts of 2:1 expanding clay minerals had much higher total K and non-exchangeable K. Exchangeable K and soil solution K contents varied significantly, but were generally low for most soils. Exchangeable K contents were lower in the regularly cultivated fields at five sites out of the eight, were higher at 2 sites, while for one site there was no change. These variations may be due to different levels of K input, uptake by crop and losses due to leaching and erosion. The two less weathered soils (Sigatoka and Nawaicoba) had lower contents of both non-exchangeable and exchangeable K in the cultivated soil when compared with the fallow sites suggesting net loss of K due to cultivation. These soils, however, also had high surface negative charge and thus a better capacity to retain K. Since the K requirement of sugarcane is characteristically high and large amounts of K are removed in the harvested crop, K fertilizer practices need to be scrutinized carefully in Fiji.

Diagenetic stoichiometry and benthic nutrient fluxes at the sediment–water interface of Lake Illawarra, Australia

Benthic flux measurements of O2, TCO2 and inorganic nutrients were made at three stations (seagrass beds, shallow bare sand and deep mud) in Lake Illawarra (Australia) to compare the characteristics of diagenesis and benthic biogeochemical processes for different primary producers (seagrass or microphytobenthos, (MPB)) and/or sediment types (sand or mud).Seagrass beds exhibited the highest gross primary productivity while the lowest rates occurred at the deep mud station. At the shallow bare sand station only, the gross primary production (GPP) and respiration (R) were balanced, while at the other two stations, R exceeded GPP by as much as 2 fold, indicating more organic carbon was decomposed than produced at the time of sampling. In general, nutrient fluxes displayed typical diurnal variation.Organic carbon oxidation scenarios, evaluated by either calcium carbonate dissolution or sulfate reduction models, indicated that both models can represent organic matter mineralization. The difference of estimated total carbon oxidized in this lake using the two models was small, ranging from 0.2% at deep mud station to maximum of 21% at seagrass station. In addition, N2 flux rates (net denitrification), estimated using carbon and nitrogen stoichiometry, were of similar magnitude as the rates estimated using LOICZ budget modeling or measured using the N2/Ar technique.Finally, a comparison of calculated diffusive fluxes and measured fluxes using incubation cores indicated that the results were of similar magnitude at the deep mud station, but the incubation cores fluxes were much higher than the calculated diffusive fluxes at the other two stations. This may have been caused by bioturbation or bioirrigation.

Matrix-bound phosphine in sediments from Lake Illawarra, New South Wales, Australia

Matrix-bound phosphine (MBP) has been measured in sediment from two cores in Lake Illawarra on the south east coast of Australia. The sediments were also dated in the upper layers. MBP concentrations found range from 142 to 1813 ng kg(-1), dw (dry weight of sediment) with some values being amongst the highest ever measured. Values of MBP in deeper sediments were higher than for near surface samples, but the patterns with depth were not consistent. Strong correlations were noted between MBP and organic phosphorus (OP, r>0.8) and with total phosphorus (TP, r>0.7), but only moderate correlations were found with organic carbon (OC, r>0.5). No correlations were found between MBP concentrations and the age of the sediments. It was confirmed that high MBP concentrations are indicative of a phosphorus rich environment. The results tend to support the premise that MBP is generated by microbial attack on OP under anaerobic conditions.