Diversity and stability of demersal species assemblages in the gulf of guinea

No Abstract

Climatic trends in continental shelf waters off Ghana and in the Gulf of Guinea, 1963-1992

Using time series analyses, some physical parameters of the continental shelf waters of the Gulf of Guinea were examined. Analysis of coastal sea surface temperatures from Ghana and Ivory Coast, and offshore sea surface temperatures from the Gulf of Guinea clearly shows spatial and inter-annual patterns of cooling in coastal waters of West Africa. The behaviour of the decomposed trend of coastal and offshore sea surface temperatures, sub-surface: temperature measured at 100 m depth off Ghana and salinity showed that the observational period (1963-1992) could be divided into three climatic periods: the period before 1972, from 1972 to 1982, and the period after 1982. In the first period, sea surface temperature at both coastal and offshore areas and bottom temperature declined and coastal salinity was relatively low. The second period was a cold one with less than average sea surface and sea bottom temperatures. The mixed layer was narrow with the thermocline remaining shallower than its: long-term average position. Coastal and bottom salinity (measured at the 100 m depth) were relatively high but the seasonal variation was minimal. This period of significant change in the physical components of the ecosystem of the Ghanaian shelf waters has hitherto not been documented in the literature. In the final phase, temperatures were high, and salinity was low and erratic. The observed localised environmental changes are consistent with global changes in the Gulf of Guinea and possibly in the tropical Atlantic basin.Les résultats dˈune analyse de séries temporelles de paramètres de lˈenvironnement du plateau continental du golfe de Guinée sont présentés. Une analyse de la température de surface côtière illustre les types de variabilité spatio–temporelle dans cette région. La température côtière, la température au large, ainsi que la température et la salinité de sub-surface (100 m) devant le Ghana montrent que la période 1963–1992 peut être divisée en trois épisodes : avant 1972, de 1972 à 1982 et après 1982. Dans la première période, la température de surface, tant à la côte quˈau large, ainsi que la température sur le fond se refroidissent, la salinité côtière restant basse. La seconde période est une période froide, caractérisée par des anomalies négatives de la température de surface et de fond. La couche de mélange est réduite et la thermocline se situe à une profondeur moindre que celle de la moyenne « climatique ». La température côtière et la salinité sur le fond (100 m) sont relativement élevées mais lˈamplitude des variations saisonnières est minimale. Cette période de changements de lˈécosystème du Ghana nˈavait pas été décrite jusquˈà présent. Dans la dernière phase, les températures sont élevées et la salinité basse, avec un comportement irrégulier. Les changements observés sont cohérents avec les changements globaux dans le golfe de Guinée et dans lˈAtlantique Sud

Biological control of cacao diseases

This chapter discusses the advances in biological control of cacao diseases over the last 15 years. Most attention has been focused on biological control of frosty pod rot (Moniliophthora roreri), witches' broom (Moniliophthora perniciosa) and black pod disease (Phytophthora spp.). Research on biocontrol of other diseases in the cacao phyllosphere or rhizosphere is scarce or in its infancy. There is, however, a steady increase in information regarding the factors influencing and the mechanisms underlying biological control of cacao diseases as well as practical aspects such as inoculum production, formulation and application. There has been a clear shift away from inundative approaches using epiphytic BCAs towards more classical biocontrol approaches using bacterial and fungal endophytes as well as vesicular arbuscular mycorrhiza. These have the advantage that they can permanently establish themselves in the cacao tree. Moreover, besides direct competition for space and nutrients, antibiosis and mycoparasitism, through induced resistance and growth promotion, endophytes have a larger arsenal of mechanisms through which they can help protect their host. Endophytic BCAs could thus provide more effective and sustainable disease control. Recent advances in our understanding of the mechanisms through which endophytic biocontrol agents can reduce pest and disease impact provide possibilities for innovative disease control strategies, including combination therapies together with natural or chemical products. Continued work on production, formulation and application is also necessary in order for biocontrol to become economically interesting. However, biological control will not become a stand-alone solution for disease control but should become part of integrated pest management strategies, with cultural management as a central and reinforcing pillar. (Résumé d'auteur