Program and Agenda

Abstract

GLOBAL RELATIONSHIP BETWEEN PHYTOPLANKTON DIVERSITY AND PRODUCTIVITY IN THE OCEAN: KILLING-THE-WINNER

The shape of the productivity-diversity relationship (PDR) is usually either unimodal or positive for most empirical datasets of both terrestrial and aquatic ecosystems. Our knowledge of the diversity patterns for marine phytoplankton is more limited although some analyses of field datasets also suggest an unimodal PDR. However, the exact mechanism(s) behind these observations are poorly understood. Theoretical studies have suggested several complementary hypotheses. Here we suggest a new theory: killing-the-winner predation (KTW). Using a marine ecosystem model we show that the relationship between primary production and diversity is unimodal at the global scale. The positive side of the PRD curve is due to stable predator-mediated co-existence of the prey resulting from KTW selective feeding. The negative side of the PRD curve is due to seasonal blooms of opportunist species that occur before they are down-regulated by selective feeding. The descending part of the curve at high productivity unveils when we change the temporal scale of observation from annual to weekly averages. Annually averaged data are close to a seasonal steady-state while weekly data also capture transient dynamics. However most of the data points lie on the positive side of the curve regardless of the temporal scale of data averaging. Therefore selective predation explains the positive side while transient competitive exclusion explains the negative side of the same unimodal PDR curve.

https://www.researchgate.net/profile/Sergio_Vallina/

Authors

Vallina, S. M., MIT / CSIC, USA, vallina@icm.csic.es

Follows, M. J., MIT, USA, mick@ocean.mit.edu

Dutkiewicz, S., MIT, USA, stephdut@mit.edu

Montoya, J. M., CSIC, Spain, montoya@icm.csic.es

Loreau, M., CNRS, France, michel.loreau@ecoex-moulis.cnrs.fr

Details

Oral presentation

Session #:108
Date: 2/24/2014
Time: 11:15
Location: 317 AB

Presentation is given by student: No