Beginning integrated coastal management efforts in Madagascar

Integrated coastal management (ICM) is an emerging approach in East Africa for the solution of various coastal issues. This paper is intended to provide an update on the current practical aspects concerning the ICM process and related policies and strategies in Madagascar. Efforts are being made in Madagascar for the mutual integration of numerous coastal projects and activities within the Environment Program of the National Environmental Action Plan. The foundations for an ICM program, built during an ICM workshop, which took place at the end of 1996 upon existing activities, are being expanded presently. These developments concern, above all, the institutional aspects related to the formulation of an ICM program. Therefore, the actual situation sees an overgrowing collaboration of the national and international agencies involved in the implementation of coastal projects, in an expandingly integrating way, within an institutional framework that grows progressively stronger. The case of Madagascar suggests reflections on how ICM can mitigate potential sectoral conflicts as well as on, how the sometimes complex nature of the social and cultural issues may influence the development of an ICM program. The need for monitoring ICM is stressed and the role of outside partners clarified.     

A detailed geochemical and rock magnetic study of dredged basalt from the Sheba Ridge,Gulf of Aden

We report the results of petrological, geochemical and rock magnetic studies of basalt dredged from the eastern end of the west Sheba Ridge during cruise 11/1979 of R. R. S. Shackleton to the Western Gulf of Aden. The ridge is part of the Red Sea-Gulf of Aden spreading axis and the basalts are olivine tholeiites. The abundances of some elements are characteristic of normal MORB (mid-ocean ridge basalt) but other elemental abundances suggest affinites with transitional-type MORB.The observed magnetic properties are interpreted in terms of the composition, concentration and microstructure of the magnetic mineral fraction by recourse to the available data on synthetic analogues. The analysis has been carried out in greater detail than has been attempted in previous magneto-petrological studies. It appears that submarine weathering of the magnetic minerals (maghemitization) brings about not only the expected change in composition but also a fall in concentration of the magnetic fraction. This could result from the removal-of-iron oxidation mechanism operating in the submarine environment. It is also found that the fall in remanence with increasing degree of maghemitization is not explicable in terms of the change in composition and concentration of the magnetic minerals. A further influence—probably microstructural change—significantly reduces the remanence intensity.     

Measurement of water particle velocities in waves

Water surface profiles and horizontal and vertical water particle velocity components have been measured to investigate the properties of intermediate depth waves generated in the laboratory. The data has been compared with linear wave theory. It was found that linear theory predicted the attenuation of velocity field with depth successfully and that it overestimates both components of velocity slightly.     

Behavioural Effects of Chemically Dispersed Oil and Subsequent Recovery in Diploria strigosa (Dana)

Abstract. Survival and behaviour of the hermatypic coral Diploria strigosa was studied during 6–24 h doses with water-accomodated fractions of chemically dispersed crude oil, and for a subsequent recovery period of 1 month. Experiments utilized a flow-through laboratory dosing procedure and incorporated petroleum hydrocarbon measurements in order to simulate a major but short-term oil spill in shallow subtidal benthic reef environments. Chemically dispersed oil treatments consisted of Arabian Light Crude oil with Corexit 9527 or BP1100WD at 1–20 ppm concentrations of oil.
In general, effects observed were sub-lethal, temporary, and associated with the highest concentrations tested. Responses to the presence of dispersed oil at 20ppm for 24 h included mesenterial filament extrusion, extreme tissue contraction, tentacle retraction and localized tissue rupture. The nature and severity of reactions during the dosing phase varied between colonies and treatments, but colonies typically resumed normal behaviour within 2 h to 4 d of the recovery period. It therefore seems unlikely that observed biological effects would impair long-term viability.     

Short-term consequences of a benthic cyanobacterial bloom (Lyngbya majuscula Gomont) for fish and penaeid prawns in Moreton Bay (Queensland, Australia)

This study examined the phenology and ecological consequences of a benthic filamentous cyanobacterial bloom (Lyngbya majuscula) in Deception Bay (Moreton Bay, Queensland, Australia). Bloom initiation occurred in mid December 1999 and expanded to encompass an 8 km² area by April 2000. Small fish and penaeid prawns (<25 cm total length) were quantitatively sampled through periods designated as before, during and after the bloom using a combination of pop-netting within mangroves and beam trawling over adjacent seagrass beds. Data on larger-bodied fish were compiled from daily fishing logs provided by local commercial fishers. Changes in dry mass of bloom material caught in nets and changes in water chemistry were also measured. Mean concentrations of ammonia-N in residual water within mangroves were several orders of magnitude higher in the affected area than in the control and dissolved oxygen was markedly lower in affected areas. Across the study area, mean density, live mass and number of species declined during the bloom, with fish assemblages using mangroves showing greater decline than assemblages using seagrasses. Response at the species level was highly variable; generally, epibenthic species showed a more sustained decline than demersals. Mean monthly fish catch was significantly lower in bloom than non-bloom years. This study has also demonstrated that throughout the bloom, the affected area continued to support a highly diverse and abundant fish and prawn assemblage, and probably maintained its function as an important nursery habitat for many species.     

Nature and composition of shore-zone sediments between Jeddah and Yanbu, eastern Red Sea

The shore-zone sediments between Jeddah and Yanbu, west coast of Saudi Arabia, are composed mostly of skeletal carbonate sands. The nearshore sediments containing benthic foraminifera, algal fragments and molluscs are multimodal, the mean grain size varying between 0.76 and 2.35 ø. The beach sediments, except samples dominated by cerithid gastropods in some localities, are relatively finer than the nearshore sediments. Although the beaches to a great extent comprise sand-sized material, fine lime muds and coarse clastic gravels occur in certain areas. The dune sediments comprising mostly algal grains and ooids are very fine with 50 percent of the material in the 0.25–0.18 mm size grade. Except a general northward decrease in mean grain size, regional trends in the textural parameters of the sediments between Jeddah and Yanbu are not quite apparent. Lateral variations in the textural characteristics suggest a landward migration of the sediments in the shore zone under the influence of northerly and northwesterly winds. The carbon and oxygen (δ ¹³C + 4.80 to 4.84‰ PDB) (δ ¹³O − 0.04 to + 0.53‰ PDB) isotopic ratios of the lime muds occurring in certain shallow margins in the shore-zone, which are much higher than those of the green algae, indicate that the fine carbonates are at least in part inorganic in origin.

Like the shallow-water carbonates in tropical seas, aragonite and high Mg-calcite are the dominant carbonate minerals in the shore-zone sediments. There is a landward increase in aragonite contents caused by the landward migration of fine material from the nearshore. The dominant clay mineral in the nearshore sediments is kaolinite with subordinate swelling chlorite and little illite. Kaolinite is contributed by the coastal regions under the sub-tropical humid climate. Swelling chlorite is considered to have been formed in the nearshore by mechanical mixture of chlorite and montmorillonite derived from the metamorphic and igneous terrains of the Tertiary mountains bordering the coastal plain.