Collapse and reorganization of a food web of Mwanza Gulf, Lake Victoria

Abstract

Starchy food products differ in the rate of starch digestion, which can affect their metabolic impact. In this study, we examined how the in vivo starch digestibility is reflected by the glycemic response, because this response is often used to predict starch digestibility. Ten healthy male volunteers [age 21 6 0.5 y, BMI 23 6 0.6 kg/m 2 (mean 6 SEM)] participated in a cross-over study, receiving three different meals: pasta with normal wheat bran (PA) and bread with normal (CB) or purple wheat bran (PBB). Purple wheat bran was added in an attempt to decrease the rate of starch digestion. The meals were enriched in 13 C and the dual isotope technique was applied to calculate the rate of appearance of exogenous glucose (RaE). The purple wheat bran in bread does not affect in vivo starch digestibility. However, the iAUC of RaE after men consumed PA was less than after they consumed CB (P , 0.0001) despite the similar glucose response. To conclude, the glycemic response does not always reflect the in vivo starch digestibility. This could have implications for intervention studies in which the glycemic response is used to characterize test products.

Niche expansion in a resilient endemic species following introduction of a novel top predator

“…The once-abundant endemic haplochromine cichlid fauna, which previously accounted for over 80% of the biomass of Lake Victoria (Kudhongania & Cordone, 1974), virtually disappeared from the deepwater and sublittoral regions of Lake Victoria in the mid-to late 1980s, with approximately 40% of the 500+ species in this group believed to have gone globally or locally extinct (Witte et al, 1992;Seehausen et al, 1997b). Many other native species also suffered serious declines during this time period and, as a result, a once diverse and complex assemblage composed of numerous trophic specialists was replaced by a much simpler assemblage dominated by a handful of generalist and omnivorous species (Balirwa et al, 2003;Ojwang et al, 2010;Downing et al, 2012). Similar faunal changes occurred in other lakes in the region where the Nile perch were introduced, including in Lake Kyoga and Lake Nabugabo (Ogutu-Ohwayo, 1993;Chapman et al, 2003).…”

The Resilience and Resistance of an Ecosystem to a Collapse of Diversity

“…The diversity collapse and Nile perch boom followed long-term increases in fishing pressure and eutrophication, two processes that had negative impacts on native species [28]. Interestingly, the collapse of haplochromine cichlids in Lake Victoria was accompanied by an increase in the abundance of the shrimp Caridina nilotica , a competitor of the largest cichlid trophic groups [29]. This shrimp became an important food source for Nile perch, but is an unlikely threat to juvenile Nile perch: it could thus represent a case where the insurance effect – seen in shrimp replacing vanishing haplochromines – decreased the resilience of the community to invasion by providing more food for Nile perch but without negatively affecting Nile perch recruitment.…”

Water hyacinth control in Lake Victoria: Transforming an ecological catastrophe into economic, social, and environmental benefits

“…It is known that the lake has seen a dramatic decrease in the native flora and fauna over the past several decades (Downing et al, 2012;Mkumbo and Marshall, 2014;Witte et al, 2012). Few studies could be found that linked the presence of the water hyacinth to the change in biodiversity (Balirwa et al, 2003;Kateregga and Sterner, 2009).…”