Sokoine University of Agriculture

Do grazers respond to or control food quality? Cross-scale analysis of algivorous fish in littoral Lake Tanganyika

Show simple item record Munubi, Renalda N. Mclntyre, Peter B. Vadeboncoeur, Yvonne 2021-07-09T07:05:48Z 2021-07-09T07:05:48Z 2018
dc.description Journal Article en_US
dc.description.abstract Food quality determines the growth rate of primary consumers and ecosystem trophic efficiencies, but it is not clear whether variation in primary consumer densities control, or is controlled by, variation in food quality. We quantified variation in the density and condition of an abundant algae-eating cichlid, Tropheus brichardi, with respect to the quality and productivity of algal biofilms within and across rocky coastal sites in Lake Tanganyika, East Africa. Adjacent land use and sediment deposi- tion in the littoral zone varied widely among sites. Tropheus brichardi maximized both caloric and phosphorus intake at the local scale by aggregating in shallow habitats: algivore density decreased with depth, tracking attached algae productivity (rETR MAX ) remarkably well (r 2 = 0.84, P = 0.00033). In contrast, algivore density was unrelated to among-site variation in algal productivity. Rather, there was significant increase in algal quality (r 2 = 0.44, P = 0.011) and decrease in algal biomass (r 2 = 0.53, P = 0.0068) with T. brichardi density across sites, consistent with strong top-down control of primary producers. The amount of inorganic sediment on rock surfaces was the strongest predictor of among-site variation in algivore density (r 2 = 0.69, P = 0.00096), and algivore gut length increased with sedimentation (r 2 = 0.36, P = 0.034). These patterns indicate extrinsic and top-down forcing of algal food quality and quantity across coastal landscapes, combined with adaptive habitat selection by fish at the local scale. Factors that degrade food quality by decreasing algal nutrient content or diluting the resource with indigestible material are likely to depress grazer densities, potentially dampening top-down control in high- light, low-nutrient aquatic ecosystems. en_US
dc.language.iso en en_US
dc.publisher Springer-Verlag GmbH Germany en_US
dc.subject Food quality en_US
dc.subject algivorous fish en_US
dc.subject ecosystem trophic en_US
dc.subject Microphytobenthos en_US
dc.subject Tropheus en_US
dc.subject Lake Tanganyika en_US
dc.subject Littoral en_US
dc.subject Sediment en_US
dc.title Do grazers respond to or control food quality? Cross-scale analysis of algivorous fish in littoral Lake Tanganyika en_US
dc.type Article en_US
dc.url en_US

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