Research expedition to the Benguela upelling system on the RV Meteor | Photo: Werner Ekau

Trophic TRAnsfer eFFICiency in the Benguela Current

Identifying differences in trophic pathways and ecosystem services in the Northern and Southern Benguela Upwelling Systems

TRAFFIC is a project involving five German and five Namibian and South African institutes. Its aim is to understand the reasons for the decrease in fishing yields in the northern Benguela current and the causes of the major changes in the southern part of the current in order to incorporate these into future sustainable management. Coastal upwelling systems account for about 20% of annual fish landings and thus play a significant role not only in the food supply of the world's population but also in the carbon and nutrient turnover in the ocean. Changes in the South-East Atlantic over the last decades have also changed ecosystem services, with different consequences in the northern and southern Benguela upwelling systems (see above, in addition to fisheries, e.g. CO2 uptake).

The Benguela current is one of the four highly productive coastal upwelling systems in the world whose export production is approximately as high as that of the unwilling system off Peru. However, the high phytoplankton productivity stands in surprising contratrast to the low productivity of the higher trophic levels: Fish, seabirds and seals. Nutrients that reach the surface during upwelling seem to be quickly re-exported, so that organisms of the higher trophic levels cannot effectively exploit the existing primary production. As a result of this inefficient recycling of nutrients, the biomass of the entire zooplankton in the northern Benguela system was only 1,3-1,8 g C m-2, almost the global average, and fishery yields in 2006 were only about 0.42 million tonnes. In the upwelling system off Peru, the yield in the same year was more than ten times as high at 6.8 million tonnes with similar size of fishing areas.

Studying and understanding the causes of this development is not only of great scientific interest. It is also crucial for future management that the essential processes and limiting factors in an ecosystem are understood. Important drivers of such processes are the structure of the wind fields, the upwelling and the strength of the water currents.
Since the conditions in the northern and southern parts of the Benguela upwelling system are very different, a comparison of these complex trophic systems and their interactions with fisheries and climate can provide important insights into the functioning of upwelling areas and their role in the global carbon cycle.

ZMT is responsible for the overall coordination of the project and for two subprojects on carbon cycles and the role of small pelagic fish in the food web. Project partners in Germany are the University of Hamburg with the Institute for Marine System and Fishery Science and the Institute for Geology, the BreMarE Institute of the University of Bremen and the Thünen Institute for Sea Fisheries in Bremerhaven.

 

Project Partners (Germany)

 

International Project Partners

Bremen Marine Ecology, Centre for Research and Education (BreMarE), University of Bremen

Institute for Marine System and Fishery Science (IMF), University of Hamburg

Institute for Geology (IfG), University of Hamburg

Thünen Institute for Sea Fisheries, Bremerhaven





 

University of Cape Town (UCT), Cape Town, South Africa

Department of Agriculture, Forestry and Fisheries (DAFF), Cape Town, South Africa

Department of Environmental Affairs (DEA), Cape Town, South Africa

National Museum, Information and Research Center (NatMIRC), Swakopmund, Namibia

University of Namibia (UNAM), Henties Bay, Namibia