James Sinclair will speak on
‘Ecological surprises’ in a bottom-up/top-down stressor interaction
at 12:30 in the EEB lounge (BioSciences, 4th floor)
Interactions between multiple anthropogenic stressors can have unexpected synergistic or antagonistic effects, making it difficult to predict their combined effect using single stressor studies. The bottom-up/top-down interaction between invasive consumers and nutrient enrichment is particularly important as both of these stressors frequently co-occur, and their multi-trophic impacts can be severely damaging to affected communities.
We conducted a field mesocosm experiment that crossed an increasing nutrient addition gradient against an increasing zebra mussel invasion gradient. Native zooplankton communities were added to the mesocosms, and after three months we examined how the single stressor effects on available resources and the zooplankton community were altered by their multiple stressor interaction. Added nutrients had no effect on primary producer abundance, but increased the abundance and dominance of the top consumer, which likely increased predation pressure on the producers and so prevented their response to increased nutrients.
Zebra mussels reduced large phytoplankton abundance by ~75%, rotifer abundance by ~80%, and shifted community composition towards larger consumer species. When combined, the top-down control exerted by the mussels interacted antagonistically to prevent any bottom-up influence of nutrient enrichment on the zooplankton community. These results provide insight into the potential outcomes of bottom-up/top-down stressor interactions, and illustrate the need for researchers to consider single stressor problems in a multiple stressor context.
James is just finishing up his MSc in Shelley Arnott’s lab. Immediately following the seminar he will be defending his thesis and then, he hopes, will begin a PhD in Shelley’s lab, committing himself to endless servitude in the pursuit of more mussels. Unfortunately James goes immediately into his defence at 1:30 on Thursday so will not be able to hang around and receive your questions and accolades but don’t let that stop you from enjoying coffee and cookies after the seminar.