Light Pollution: An Underestimated Environmental Stressor in the Ocean

Sixteen students, eight countries, and one research question: how does artificial light influence algae growth? This was the focus of the 2024 GAME project. GAME, short for Global Approach by Modular Experiment, offers German and international students the opportunity to work collaboratively on experimental research questions for a year and write their theses based on the results. This globally unique research and educational programme for marine science students has been run at GEOMAR for 21 years and was funded this year by the Klaus Tschira Foundation.

The 2024 Research Question: Macroalgae under Artificial Light

The focus for the 2024 GAME cohort was: “How does artificial light at night affect the growth, photosynthetic performance, and defence capabilities of macroalgae?” Project leader Dr Mark Lenz, a marine ecologist at GEOMAR, highlights the scientific importance of this work: “Artificial light as a form of pollution is increasingly recognised in the marine environment. Thanks to GAME’s global comparative approach, we can gain insights that would otherwise be impossible.”

Fourteen species of macroalgae were exposed to artificial light at night (ALAN) at an intensity of 30 lux for three weeks. Two light colours – white and yellow – were used.

Measurements and Results:

• Changes in Biomass: Seven of the 14 species showed distinct responses to the artificial nighttime light. These effects were both species- and location-specific: At some locations, the light led to increased growth, whereas at others, biomass was reduced.
• Attractiveness to Grazers: Feeding experiments were conducted to determine how strongly the algae were grazed upon by herbivores such as sea urchins, snails, or isopods. For two of the 14 species, artificial light at night increased their attractiveness to grazers.

A Global Experiment: From Kiel to the World

The participants first met in Kiel in spring, where they developed the uniform experimental design for their research question during an intensive workshop. In tandem teams of one German student and one international partner, they then travelled to their research locations across the globe in April. The teams conducted their fieldwork in Japan, Malaysia, Cape Verde, Wales, Finland, Croatia, Spain, and Madeira (Portugal). After six months of field research, the findings were brought together and analysed in Kiel in October.

Mark Lenz summarises: “The results show that light pollution can have both positive and negative effects, depending on the species and location. Particularly remarkable is the fact that the magnitude of these effects could potentially influence the population development of macroalgae.”

Why the Results Matter

Macroalgae are crucial for the stability and functionality of coastal ecosystems. The findings of the GAME project confirm that light pollution can impact these vital habitats.

“These effects have rarely been studied so far,” says Lenz. “Our study complements the only recently published research focusing on two algal species. Our findings underline the need to consider light pollution as a significant environmental factor in coastal ecosystems.”

Presentation of Results at North German Universities:

18 December (University of Oldenburg): 10:00, Campus Wechloy, Building W15, Carl-von-Ossietzky-Straße 9-11, Room W01-015

18 December (University of Bremen): 15:15, Natural Sciences 2, Room C300, University Central Area

15 January (University of Hamburg): 11:15, Kowwigsaal, Biozentrum Grindel, Martin-Luther-King-Platz 3

About: GAME

GAME is an international research and training programme for early-career marine scientists and stands for Global Approach by Modular Experiment. Each year, the programme tackles an ecological research question through synchronised, identical experiments conducted at multiple locations worldwide. This approach yields globally comparable results that span biogeographical regions and ecosystem boundaries.

Up to 20 students can participate each year, conducting their experiments in binational teams at up to ten global locations. The preparatory and concluding phases of each project take place collectively at GEOMAR in Kiel.

The next GAME cohort in 2025 will focus on the impact of artificial light at night on epiphytes – organisms that grow on the surfaces of macroalgae. Applications are open until 31 January 2025.