Our research activities involve the modelling and analysis of complex biological, ecological and socioeconomic systems. We are particularly interested in the organisation of such complex adaptive systems and in their emergent properties. We typically develop and work with continuous-time, differential equation models and we touch on aspects pertaining to systems theory, nonlinear dynamics, collective behaviour, evolution, and adaptation. Some of our current projects focus on biodiversitiy, incuding biodiversity and ecosystem function relationships, biogeochemical cycling of carbon, biogenic calcification and ocean acidification, impact of pollution on seabirds and marine megafauna, trait adaptation, behavioural economics, and collapse of societies. Plankton ecosystems, coral reefs, and human-resource interactions are currently at the centre of our research activities.
The Slow Demise of Easter Island
Easter Island has been considered a general model of human-environment interactions on a global scale and its supposed social-ecological collapse is often taken as a grim warning for our society. However, the island’s detailed history, in particular with respect to the rise and fall of the human population and to the disappearance of the forest, remains controversial. Is Easter Island a paradigm for resource overexploitation and self-destruction (ecocide), for a society destroyed by colonialism and slavery (genocide), or rather an example of a slow and long fall (slow demise)? Using a mathematical model, we showed that out of these three possibilities only the slow demise can best explain the available archeological evidence.
A. Merico (2017). Models of Easter Island human–resource dynamics: advances and gaps, Frontiers in Ecology and Evolution, 5(154):1-7.
G. Brandt & A. Merico (2015). The slow demise of Easter Island: insights from a modelling investigation, Frontiers in Ecology and Evolution, 3(13), 1-12.
We developed a model for studying coral polyp calcification. The model simulates the carbonate system in four different compartments: the seawater, the polyp tissue, the coelenteron, and the calcifying fluid. The model is adjusted to a state of activity as observed by direct microsensor measurements in the calcifying fluid. As aragonite precipitation removes carbonate ions, total alkalinity and dissolved inorganic carbonate (DIC) decrease. Simulated CO2 perturbation experiments reveal decreasing calcification rates under elevated pCO2 despite strong metabolic control of the calcifying fluid.
Decreasing coral calcification at elevated seawater pCO2 is the result of increased CO2 diffusion into the calcification site. However, we found that CO2 diffusion alone is not sufficient to sustain the observed calcification rates, an additional mechanism must exist to supplement carbon into the calcifying fluid. The model shows that calcification occurs only when a bicarbonate transport in symport with protons is considered.
S. Hohn & A. Merico (2015). Quantifying the relative importance of transcellular and paracellular ion transports to coral polyp calcification, Frontiers in Earth Science, 2(37), 1-11.
S. Hohn & A. Merico (2012). Modelling coral polyp calcification in relation to ocean acidification, Biogeosciences, 9, 4441-4454.
Indonesian peatland degradation and the global carbon cycle
Recent studies have estimated that CO2 released from drained peatland is between 355 Mt y−1 and 855 Mt y−1 in 2006 of which 82% mainly coming from Sumatra and Kalimantan. The effects of these emissions on the global carbon cycle are largely unknown. We investigated the effects of different emission and functioning scenarios of the "Indonesian carbon system" on the global carbon cycle. The Indonesian carbon system comprises various carbon reservoirs including the tropical rain forest, the peatlands, the seagrasses, the coral reefs, and the neritic plankton. We assessed and quantified the role of each of these components to different regional anthropogenic perturbations with a box model of the global ocean to identify potential positive or negative feedbacks to the global carbon cycle.
J.F. Abrams, S. Hohn, T. Rixen & A. Merico (2018). Sundaland peat carbon dynamics and its contribution to the Holocene atmospheric CO2 concentration. Global Biogeochemical Cycles, 32.
J.F. Abrams, S. Hohn, T. Rixen, A. Baum & A. Merico (2016). The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle. Global Change Biology, 22(1), 325-337.
We develop ecological models based on functional traits. Traits are characteristics or observable features of an organism that may be inherited or acquired and are generally considered as reflecting adaptations to variation in the physical and biotic environment and trade-offs.
Trait-based models can be constructed by incorporating principles derived from evolutionary biology and quantitative genetics to produce appropriate parameterisations of community behaviour. The use of traits to predict community composition can explain the organisation of ecological systems and predict their re-organisation in a changing environment. Trait-based models are able to describe the ecological community or the ecosystem as a whole entity making them also suitable for studying feedbacks between life and its environment on evolutionary time scales.
N.A. Raharinirina, G. Brandt & A. Merico (2017). A Trait-based model for describing the adaptive dynamics of coral-algae symbiosis, Frontiers in Ecology and Evolution, 5(31), 1-11.
S.L. Smith, S. Vallina & A. Merico (2016). Phytoplankton size-diversity mediates an emergent trade-off in ecosystem functioning for rare versus frequent disturbances, Scientific Reports, 6(34170), 1-11.
E. Acevedo-Trejos, G. Brandt, J. Bruggeman & A. Merico (2015). Mechanisms shaping size structure and functional diversity of phytoplankton communities in the ocean, Scientific Reports, 5(8918), 1-8.
Human cooperation in common pool resource systems
Many marine ecosystems that are exploited for natural goods can be regarded as common pool resources. The management of such systems requires a detailed knowledge of the ecological resource under investigation and of the human behaviour.
We developed a simple adaptive model with harvest behaviour as the main continuous trait describing the coupled dynamics of a renewable common pool resource and a group of human consumers. The balance between instantaneous harvest and potential future harvest determines the degree of cooperation among consumers. Consistent with Hardin's tragedy of the commons and numerous real examples, we found that maximising the instantaneous harvest of the common pool resource leads to declining long-term yields and finally to a collapse of the resource-consumer system. By contrast, incorporating potential future returns into the consumer fitness function significantly enhances the degree of cooperation.
G. Brandt & A. Merico (2013). Tipping points and user-resource system collapse in a simple model of evolutionary dynamics, Ecological Complexity, 13, 46-52.
G. Brandt, A. Merico, B. Vollan, & A. Schlüter (2012). Human adaptive behavior in common pool resource systems, PLoS ONE, 7(12), e52763.
INSIDE: Inter- and intra-specific size diversity of phytoplankton and its impacts on ecosystem functions (DFG)
E. Acevedo-Trejos, E. Marañón & A. Merico (2018) Phytoplankton size diversity and ecosystem function relationships across oceanic regions, Proceedings of the Royal Society B, in press.
J.F. Abrams, S. Hohn, T. Rixen & A. Merico (2018) Sundaland peat carbon dynamics and its contribution to the Holocene atmospheric CO2 concentration, Global Biogeochemical Cycles, 32.
A. Merico (2017) Models of Easter Island human-resource dynamics: advances and gaps, Frontiers in Ecology and Evolution, 5, 154.
D.C. Tavares, J.F. de Moura, A. Merico & S. Siciliano (2017) Incidence of marine debris in seabirds feeding at different water depths, Marine Pollution Bulletin, 119(2), 68-73.
A.N. Raharinirina, G. Brandt & A. Merico (2017) A trait-based model for describing the adaptive dynamics of coral-algae symbiosis, Frontiers in Ecology and Evolution, 5, 31.
S.L. Smith, S. Vallina & A. Merico (2016) Phytoplankton size-diversity mediates an emergent trade-off in ecosystem functioning for rare versus frequent disturbances, Scientific Reports, 6(34170), 1-11. Press release.
E. Acevedo-Trejos, G. Brandt, S.L. Smith & A. Merico (2016) PhytoSFDM version 1.0.0: Phytoplankton Size and functional Diversity Model, Geoscientific Model Development, 9, 4071-4085.
J.F. Abrams, S. Hohn, T. Rixen, A. Baum & A. Merico (2016) The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle. Global Change Biology, 22(1), 325-337.
T. Tyrrell, A. Merico & D.I. Armstrong McKay (2015) Severity of ocean acidification following the end-Cretaceous asteroid impact, Proceedings of the National Academy of Sciences of the USA, 112(21), 6556-6561. Press release.
Symposium: "14th International Coral Reef Symposium (ICRS2020)", 5-10 July 2020, Bremen, Germany
Winter School "Exploring Complex Systems Using Computational Tools", 3-9 February 2018, AIMS, Mbour, Senegal
Workshop "Trait-based approaches to ocean life", 20-23 August 2017, Solstrand, Bergen, Norway.
Workshop "The Carnian Pluvial Episode (Late Triassic): Climate Change and Evolutionary Innovations", 16-17 May 2017, HWK, Delmenhorst, Germany.
Workshop "Plankton biodiversity, dynamic eco-physiology, and ecosystem function", 15-17 February 2017. ZMT, Bremen, Germany.
Workshop "Trait-based approaches in ecology", 11 November 2014. ZMT, Bremen, Germany.
Workshop "Mathematichal tools for understanding and managing fisheries: synthesizing and refining data and models", 7-9 May 2014. Mbour, Senegal.
Workshop "Trait-based approaches and other tools to better understand coral reef functioning", 16.12.2013. ZMT, Bremen, Germany.
Workshop "Trait evolution and adaptation", 12.06.2013. ZMT, Bremen, Germany.
Workshop "CArbon and Nutrients through Ocean Ecosystems (CANOE)", 17.08.2012. Geomatikum, Hamburg, Germany.
Workshop "Evolution of cooperation in socio-ecological systems", 28 September 2011. ZMT, Bremen, Germany.
Recent media coverage
Deutsche Welle: Fishing for sustainability
Spektrum der Wissenschaft: Das Rätsel von Rapa Nui
Landeszeitung Lüneburg: Ökologischer Tanz auf der Rasierklinge
Leibniz Association: Das Rätsel der Rapa Nui