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GAME: 2000 - 2007: Projects I - IV
2005–2007: Diversity and Stability of Marine Communities
The project addressed the question whether the stability of a community towards changes in its abiotic and biotic environment is a function of its diversity. We tried to measure the time which aufwuchs-communities of different successional stage can survive when they are displaced to a new habitat, without changing their structure and composition. Since whole communities are dislocated over very far distances as aufwuchs on ship hulls, this is an important subject in the context of invasion ecology. The ability of communities to survive in the new habitat decides whether animal or plant species succeed to establish themselves in these habitats permanently.
For the purpose of their experiments GAME participants moored PVC rings with attached settlement plates in near-shore shallow water. Communities which settled on the plates were transplanted together with their substrate to new habitats with differing living conditions after varying periods of time. To avoid the actual introduction of alien species into habitats the transplantation experiments were not carried out on a global scale, but within a relatively small spatial range (< 10 km) in the different regions.
Southern hemisphere sites: Hobart (Tasmania), Niterói (Brazil), Coquimbo (Chile), Leigh (New Zealand)
Northern hemisphere sites: Åbo (Sweden), Chiba (Japan), Kuala Terengganu (Malaysia), Funchal (Madeira Islands, Portugal)
GAME IV Alumni
2004–2006: Impact of Temporal Variability of Disturbances on Diversity and Composition of Hard Bottom Marine Communities
In many ecological systems disturbances are decisive for the structure of the communities. The role of disturbances in ecological processes has been investigated oftentimes, in most cases with emphasis on medium frequencies and intensities. However, natural disturbance regimes are in many cases spatially and temporally highly variable, which aspect was often disregarded. Therefore, the project tried to measure the effect of temporal variability of disturbances on the diversity of marine aufwuchs-communities. For this purpose disturbance events were distributed in differing manner over a certain period of time, either evenly or lumped in clusters, while keeping the total number of events constant. Three months before beginning the experiments settlement plates were moored for colonisation by algae and sessile invertebrates. During the experiments, each disturbance event was simulated by removing all organisms from a random area of 20% of the plates to become free for recolonisation.
As was to be expected, at all sites the disturbances had an effect on the total biomass of the communities. Only at one site (Alexandria) the variability of disturbances significantly affected the community diversity. At another site, disturbance variability changed the biomass total; finally, at three sites the variability of disturbances produced an effect on the occurrence of certain species.
Southern hemisphere sites: Coquimbo (Chile), Wollongong (Australia), Leigh (New Zealand), Niterói (Brazil)
Northern hemisphere sites: Alexandria (Egypt), Newcastle upon Tyne (England), Kuala Terengganu (Malaysia), Gdynia and Gdansk (Poland), Funchal (Madeira Islands, Portugal)
GAME III Alumni
2003–2005: Effect of Disturbance and Productivity on the Diversity and Composition of Marine Hard Bottom Communities
Disturbances structure communities, unleash resources, and reduce the dominance of competitively strong species, which otherwise expel weaker species from the habitat. They are thus preserving the diversity in biological systems. A number of ecological models exist which try to predict under what circumstances the biodiversity of a system will be highest, e.g. the “Intermediate Disturbance Hypothesis” (IDH, Connell 1978), which describes the interconnection of disturbance and diversity. Beyond it, the “Dynamic Equilibrium Model” (Huston 1979, Kondoh 2001) concerns the interaction of the productivity of a system and the frequency of disturbances. This latter model claims that productivity counters the effects of disturbances and that, given a low rate of disturbances, a high community diversity is only possible when productivity is low. This GAME project tested both hypotheses, using aufwuchs-communities of different developmental stage.
Results are contrary to the importance which many ecologists attach to both concepts. While the IDH’s prediction of maximal diversity where disturbance is on a medium level could be confirmed at three sites out of nine, interaction of productivity and disturbance was not found in any of the systems.
Southern hemisphere sites: Adelaide (Australia), Niterói (Brazil), Coquimbo (Chile), Cape Town (South Africa)
Northern hemisphere sites: Newcastle upon Tyne (England), Pisa (Italy), Tohoku (Japan), Funchal (Madeira Islands, Portugal), Tjärnö (Sweden)
GAME II Alumni
2002–2004: Induction of Chemical Anti-Feeding Defence in Marine Macro Algae
During evolution, marine algae have developed a number of mechanisms to defend themselves against grazing by herbivores, e.g. isopods, amphipods, or snails and slugs. The GAME project investigated whether chemical defence in macro algae can be induced by the grazing.
During the experiments, after a phase of acclimatisation algae were exposed to grazing, whereafter the grazers were removed and the algae were allowed to recover. The algae were then converted into an extract which was used in tests of herbivore feeding preference. It was measured whether these extracts from already grazed algae would make artificial food less attractive for the grazers than food which was treated with extracts from ungrazed algae.
In many cases a preference for the food treated with ungrazed algae extract was found, which supports the hypothesis of chemical defence. On the other hand, the effect was mostly short-term. It may be concluded that the algae can switch on or off their chemical defence quite rapidly.
Southern hemisphere sites: Niterói (Brazil), Coquimbo (Chile), Mombasa (Kenya), Grahamstown (South Africa)
Northern hemisphere sites: Newcastle upon Tyne (England), Tjärnö (Sweden), Suwon (South Korea), Faro (Portugal)
GAME I Alumni
2000–2002 (Pilot Project): Impact of UV Radiation on the Diversity of Hard Bottom Marine Communities
The amount of UV light which reaches the earth’s surface has increased in the last decades. The GAME pilot project investigated the effects of different radiation regimes on the diversity and biomass of marine shallow water hard bottom communities.
Only sessile organisms, which are unable to evade the UV radiation actively, were taken into account. PVC settlement plates were mounted in a depth of 4 cm below the water surface and covered with differing filters to test the effects of radiation regimes with both types of UV radiation or with solely UVA or UVB radiation or no radiation at all. Growing aufwuchs-communities were exposed to the respective regimes for a duration of twelve weeks.
In general, both UVA and UVB radiation regimes had similar effects at all sites on the aufwuchs-communities’ diversity and biomass, since both parameters were reduced more by UVA radiation than by UVB radiation. However, the type of UV radiation had no impact on the composition of the communities. Only in some cases certain species exclusively occurred on plates which had been shielded from UV radiation totally. Quite surprisingly, all of the effects of UV radiation disappeared after two or three months of continued observation. This probably is due to positive interaction of the organisms by shadowing each other.
Southern hemisphere sites: Antarctica, Wollongong (Australia), Coquimbo (Chile), Lüderitz (Namibia), Mombasa (Kenya)
Northern hemisphere sites: Hong Kong (China), Israel, Nova Scotia (Canada), Kiel (Germany), Norway