GAME project IX - 2011

March to December 2011:

Which impact does ecological resource predictability have on distribution patterns of marine species?

The fact that organisms differ in their general ability to cope with fluctuating environmental conditions is a cornerstone of theoretical concepts that seek to explain the large-scale distribution of species. These inter-specific differences are most often ascribed to the adaptation of organisms to regionally prevailing abiotic and biotic regimes over evolutionary time scales. This concept predicts that organisms that originate from habitats in which, e.g., energy availability is constant, should be generally less tolerant towards fluctuating environmental conditions than species stemming from regions subjected to temporal variability. However, though the adaptionist viewpoint is widespread among ecologists, its significance has rarely been tested experimentally. In the upcoming GAME project we therefore intend to test whether organisms from habitats with a constant energy supply, such as tropical shallow subtidal systems, are generally worse in coping with fluctuations in energy abundance than species from less predictable habitats. This would be temperate regions where energy acquisition in primary but also in many secondary producers is subjected to annual fluctuations in solar radiation intensity.

Experimental Approach

Multi-site comparisons between various regions worldwide should enable us to test the hypothesis that the ability to cope with unpredictable energy supply is a function of latitude. For this, marine invertebrates or macroalgae should be reared under laboratory conditions for time spans that allow the reliable assessment of fitness components such as growth or mortality. At each of the sites, one or more species should be kept a) under predictable food/light/nutrient regimes, i.e. resource availability is constant throughout the experiment, and b) under stochastic regimes, i.e. food/light/nutrients are provided in pulses at irregular time intervals. However, the total amount of energy provided during the course of the experiment should be the same for both groups. Finally, the performance of the test organisms under the two scenarios will be compared. The resulting ratio (e.g. growth under variable food supply/growth under constant food supply) will provide us a species- and site-specific measure for tolerance towards unpredictable conditions and can be compared between sites/species. Furthermore, it can be correlated with latitude.

For this type of experiments, the most promising test organisms are either macroalgae or animals in which energy acquisition is subjected to annual fluctuations in the abundance of food items and which cannot migrate to avoid periods of suboptimal conditions. This will restrict us to benthic filter/tentacle feeders such as bivalves, ascidians and barnacles. However, previous GAME projects showed that the maintenance of these organisms under conditions that allow natural growth rates is demanding. We will make use of the competence acquired in previous GAME projects and in long-term studies on mussels and barnacles at IFM-GEOMAR. For this project the establishment of micro-algal cultures at the different institutes may be indispensable.

The above described trials may be supplemented by within-region comparisons between species or populations of conspecifics that live in habitats which differ in their inherent stability. Habitats suitable for such comparisons could be a) subtidal vs. intertidal, b) estuaries vs. seashores, c) lagoons vs. seashores.

Key words: habitat stability, habitat predictability, stress resistance, adaptation, selection, species tolerances, distributional ranges, energy acquisition, energy supply.

GAME IX Alumni

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GAME: Project VIII - 2010/2011

April 2010 to January 2011:

Invasive marine organisms: are populations living in an invaded habitat more resistant against environmental stress than their counterparts in the source regions?

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GAME: Project VII - 2008/2009/2010

October 2008 to July 2009 (southern hemisphere) and April 2009 to January 2010 (northern hemisphere):

Are populations in anthropogenically stressed habitats more susceptible to damage from climate change?

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GAME: Project VI - 2007/2008/2009

October 2007 to July 2008 (southern hemisphere) and April 2008 to January 2009 (northern hemisphere):

Interactions of algae and their predators: do algae react more rapidly if grazing pressure is intense or is their reaction speed unadjustable?

We will, in direct subsequence to our previous research, continue to investigate interactions between marine macro algae and their predators.

From earlier GAME research we already know that many macro algae have inducible defence mechanisms against grazing at their disposal. This means that under the presence of grazers these algae produce chemical substances which lower their attractivity as food. To minimize energy demand the defence can be switched off again when the grazers disappear. We now will try to find out whether the time delay (“induction time”) between appearance of the grazers and the begin of chemical defence is a function of the intensity of the grazing or whether the reaction speed is unadjustable. This question has not been analysed up to now, but we believe that the answer will be especially important for the understanding of temporal and spatial patterns in interactions between algae and herbivores. Experimentation started in autumn 2007 on the southern hemisphere and will be continued in 2008 on the northern half of the planet.

Detailed research outline (PDF).

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GAME: Project V - 2006/2007/2008

October 2006 to July 2007 (southern hemisphere) and April 2007 to January 2008 (northern hemisphere):

Impact of light stress on the self-defence capabilities of macro algae against predators and “aufwuchs” degradation

The project started in October 2006 with a preparatory course for a first group of students, who carried out their experiments on the southern hemisphere beginning in November 2006. In April 2007 a second group prepared for the northern hemisphere experiments.

The project investigated how and to what extent environmental stress can affect the self-defence capabilities of marine macro algae, i.e., whether stressed individuals become less viable in their habitat than their unstressed mates. Stress denotes more of a long-lasting and in most cases non-lethal influence on organisms, while disturbances are short-term events; possible stress factors of major importance affecting marine algae are therefore the physical parameters illumination, salinity, and temperature.

In our experiments we used illumination strength as independent variable because of those mentioned it is the easiest to manipulate in an aquatic context, e.g. by means of light filters, gossamer mats, artificial light, etc.

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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