ZMT - Leibniz Zentrum für Marine Tropenforschung

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The resilience of coral reef systems, i.e. their ability to withstand stressors without fundamentally altering their structure and function, as well as the conditions under which phase shifts can be detected and reversed, are key aspects for the sustainable use, management and long-term integrity of these systems. Recent developments in ecological and resilience theory as well as in the integrated assessment of socio-economic and ecological dynamics allow for an improved understanding of the interplay of ecological processes, biodiversity, human agency, societal drivers of reef use, and social-ecological resilience.

In our working group, we combine studies of ecological processes with assessments of coastal livelihoods and marine management (in close collaboration with the working group ‘Social-Ecological Systems Analysis’) to arrive at a holistic understanding of linked social and ecological dynamics and implications for the sustainable use and management of coral reef systems.

Stony corals constitute the most prominent component of benthic communities in coral reefs, providing food and shelter to a rich variety of associated organisms and constructing the complex three-dimensional architecture of the reef by the deposition of calcium carbonate. Yet, the reef benthos comprises other sessile organisms as well, such as algae, sponges or soft corals. These organisms compete with each other for space and resources, and the benthic community is shaped by processes such as recruitment, growth, predation and competition. Human activities such as agriculture in the coastal zone, the use of destructive methods for fishing or the removal of fishes directly and indirectly impact the benthos, altering community dynamics and ultimately community composition and function. We combine underwater surveys of benthic communities with experimental approaches to assess the processes shaping reef communities and how they respond to anthropogenic impacts.

Fishes are crucial elements in coral reef systems. They influence benthic dynamics by feeding on algae and corals, and utilize the benthos for shelter, in some cases affecting the organisms they dwell in. Conversely, fish communities are shaped by the structure of the reef they live in. Using a range of methodological approaches, from underwater visual census to aquarium experiments, we assess the linkages between reef habitat and fish communities and the way these associations are modified by human activities.

Coral reefs display a rich diversity of species. Species diversity has been linked to ecosystem functioning – more species often relate to higher productivity or more effective turnover of biomass. At the same time, if several species fulfil similar ecological roles, diversity can contribute to higher resilience towards the reduction or loss of individual species. However, if important functions are provided by rare or particularly vulnerable species, higher diversity can actually contribute to a higher susceptibility of a system to disturbance. The interplay between species diversity, ecosystem functioning, and resilience, and the development of novel indicators for resilience and disturbance, are a particular area of interest of our group.

Given that local stressors are a widespread cause for damage and degradation of coral reefs, restoration methods for coral reefs are an important tool in the portfolio of reef management approaches. These methods may range from passive restoration in the form of banning of harmful activities to active restoration, for example the provision of artificial substrates or the transplantation of organisms. Drawing on aspects of community ecology, physiology and socio-economics, we are interested in the potential of restoration methods to augment the resilience of coral reef systems.

The livelihoods of coastal communities are usually closely linked to the adjacent coastal and marine ecosystems. Changes in these ecosystems thus have repercussions for the people depending on them, and the livelihood landscape and changes therein are important factors affecting the structure and dynamics of the ecosystems. For this topic, we collaborate closely with the WG Social-Ecological Systems Analysis and employ a range of qualitative and quantitative social science methods to assess existing and potential livelihood options, and the factors structuring these options as well as changes therein. The information generated in these assessments is linked with ecological studies, for example in the form of information on target species’ identity and amount caught.

Ultimately, the formulation of sound management approaches requires an acute understanding of the factors underlying the use of marine resources, and of the conditions leading to successful management or its failure. In an increasingly connected world, marine resources harvested in one place are often destined for markets far away from the country of origin. The structure and development of particular fisheries, and the institutions that govern them, are thus among the social aspects of coral reef social-ecological systems we are interested in. This topic is another one in which we work together closely with the social science department.