Mosquito fauna on the Cape Verde Islands (West Africa): an update on species distribution and a new finding

To evaluate the risk of transmission of vector-borne diseases, regular updates of the geographic distribution of insect vectors are required. In the archipelago of Cape Verde, nine mosquito species have been reported. Of these, four are major vectors of diseases that have been present in the archipelago: yellow fever, lymphatic filariasis, malaria and, currently, an outbreak of dengue. In order to assess variation in mosquito biodiversity, we have carried out an update on the distribution of the mosquito species in Cape Verde, based on an enquiry of 26 unpublished technical reports (1983-2006) and on the results of an entomological survey carried out in 2007. Overall, there seems to be a general trend for an expansion of biological diversity in the islands. Mosquito species richness was negatively correlated with the distance of the islands from the mainland but not with the size of the islands. Human- and/or sporadic climatic-mediated events of dispersal may have contributed to a homogenization of species richness regardless of island size but other ecological factors may also have affected the mosquito biogeography in the archipelago. An additional species, Culex perexiguus, was collected for the first time in the archipelago during the 2007 survey.

How geographic distance and depth drive ecological variability and isolation of demersal fish communities in an archipelago system (Cape Verde, Eastern Atlantic Ocean)

Cape Verde is a tropical oceanic ecosystem, highly fragmented and dispersed, with islands physically isolated by distance and depth. To understand how isolation affects the ecological variability in this archipelago, we conducted a research project on the community structure of the 18 commercially most important demersal fishes. An index of ecological distance based on species relative dominance (Di) is developed from Catch Per Unit Effort, derived from an extensive database of artisanal fisheries. Two ecological measures of distance between islands are calculated: at the species level, DDi, and at the community level, DD (sum of DDi). A physical isolation factor (Idb) combining distance (d) and bathymetry (b) is proposed. Covariance analysis shows that isolation factor is positively correlated with both DDi and DD, suggesting that Idb can be considered as an ecological isolation factor. The effect of Idb varies with season and species. This effect is stronger in summer (May to November), than in winter (December to April), which appears to be more unstable. Species react differently to Idb, independently of season. A principal component analysis on the monthly (DDi) for the 12 islands and the 18 species, complemented by an agglomerative hierarchical clustering, shows a geographic pattern of island organization, according to Idb. Results indicate that the ecological structure of demersal fish communities of Cape Verde archipelago, both in time and space, can be explained by a geographic isolation factor. The analytical approach used here is promising and could be tested in other archipelago systems.

Variation of the Chlorophyll a Related to Sea Surface Temperature, Wind and Geostrophic Currents in the Cape Verde Region Using Satellite Data

We present a comparative analysis of satellite derived climatologies in the Cape Verde region (CV). In order to establish chlorophyll a variability, in relation to other oceanographic phenomena, a set of, relatively long (from five to eight years), time series of chlorophyll a, sea surface temperature, wind and geostrophic currents, were ensembled for the Eastern Central Atlantic (ECA). We studied seasonal and inter-annual variability of phytoplankton concentration, in relation to the rest of the variables, with a special focus in CV. We compared the situation within the archipelago with those of the surrounding marine environments, such as the North West African Upwelling (NWAU), North Atlantic Subtropical Gyre (NASTG), North Equatorial Counter Current (NECC) and Guinea Dome (GD). At the seasonal scale, CV region behaves partly as the surrounding areas, nevertheless, some autochthonous features were also found. The maximum peak of the pigment having a positive correlation with temperature is found at the end of the year for all the points in the archipelago; a less remarkable rise with negative correlation is also detected in February for points CV2 and CV4. This is behavior that none of the surrounding environments have shown. This enrichment was found to be preceded by a drastic drop in wind intensity (SW Monsoon) during summer months. The inter-annual analysis shows a tendency for decreasing of the chlorophyll a concentration.

Variation of the Chlorophyll a Related to Sea Surface Temperature, Wind and Geostrophic Currents in the Cape Verde Region Using Satellite Data

We present a comparative analysis of satellite derived climatologies in the Cape Verde region (CV). In order to establish chlorophyll a variability, in relation to other oceanographic phenomena, a set of, relatively long (from five to eight years), time series of chlorophyll a, sea surface temperature, wind and geostrophic currents, were ensembled for the Eastern Central Atlantic (ECA). We studied seasonal and inter-annual variability of phytoplankton concentration, in relation to the rest of the variables, with a special focus in CV. We compared the situation within the archipelago with those of the surrounding marine environments, such as the North West African Upwelling (NWAU), North Atlantic Subtropical Gyre (NASTG), North Equatorial Counter Current (NECC) and Guinea Dome (GD). At the seasonal scale, CV region behaves partly as the surrounding areas, nevertheless, some autochthonous features were also found. The maximum peak of the pigment having a positive correlation with temperature is found at the end of the year for all the points in the archipelago; a less remarkable rise with negative correlation is also detected in February for points CV2 and CV4. This is behavior that none of the surrounding environments have shown. This enrichment was found to be preceded by a drastic drop in wind intensity (SW Monsoon) during summer months. The inter-annual analysis shows a tendency for decreasing of the chlorophyll a concentration.