How does the magnitude of wildlife input affect
a large river food web?
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Animal subsidies have important effects on aquatic food webs. With global declines in megafauna, the magnitude of animal subsidies into freshwater systems decline as well. Therefore, it is important to understand how the magnitude of animal subsidies affects aquatic food webs. The Mara River in Kenya is home to over 4000 hippos that cool off in the river during the day and graze on the surrounding grasslands at night. The Mara River is also famous for the annual wildebeest crossings, during which hundreds of wildebeest can drown in the river. I am working with David Post (Yale University), Amanda Subalusky and Chris Dutton (University of Florida), Laban Njoroge (National Museums of Kenya), and Emma Rosi (Cary Institute) to determine if the magnitude of the hippo dung and wildebeest carcass input affects production, energy flow, and stability of the Mara River food web.
River Production
The Mara River in Kenya is unique in that it has a well-constrained wildlife input gradient. In the northern parts there is virtually no wildlife input, but the hippo population increases up to over 4000 hippos as you move south towards the Kenya-Tanzania border. In addition, wildebeest river crossings and related drownings occur between sites 5 and 6 from July through November.
I am currently leading an amazing field team who collects algal and macroinvertebrate communities monthly at 6 sites along the gradient, to determine how changes in wildlife input affect algal production and invertebrate community structure and production. We also deploy sticky traps on the edge of the river to see if any benthic changes are reflected in the insect emergence. In collaboration with Edward Njagi (National Museums of Kenya), we are in the process of collecting fish biomass data along the same gradient. Results could show just how important shifts in animal subsidies are to terrestrial-aquatic linkages.
I am currently leading an amazing field team who collects algal and macroinvertebrate communities monthly at 6 sites along the gradient, to determine how changes in wildlife input affect algal production and invertebrate community structure and production. We also deploy sticky traps on the edge of the river to see if any benthic changes are reflected in the insect emergence. In collaboration with Edward Njagi (National Museums of Kenya), we are in the process of collecting fish biomass data along the same gradient. Results could show just how important shifts in animal subsidies are to terrestrial-aquatic linkages.
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Interested in the latest results? Click below to check out my recent talk for the annual Society of Freshwater Science meeting: Bugs care how many Hippos are there |
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Energy Flow through the river food web
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I am calculating the trophic basis of production for dominant invertebrate taxa at each site to quantify if and how the energy flow between resources and consumers changes along the wildlife input gradient. In addition to secondary production values, it incorporates assimilation efficiencies of various food types, net production efficiency, and percent availability of different food items within the invertebrate gut.
Curious how to quantify gut contents from tiny insects?
Here are some tips: Part 1: The dissection Part 2: The slide preparation Part 3: The identification Feel free to contact me with questions about this process. |
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Want to learn more?
I organized a free one week long virtual short course together with my collaborators where we discussed all the ins and outs of freshwater food webs in East Africa. We hosted this course in June 2021, but we are planning to repeat it!
Please email me if you would like to be on the alert list for when the course will be offered again!
Click below to check out the most recent course syllabus:
Please email me if you would like to be on the alert list for when the course will be offered again!
Click below to check out the most recent course syllabus:
