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Master's Programs in Informatics, Degree Programs in Comprehensive Human Sciences M2 Cai Danmeng

The allure of the ocean has captivated many, but for some, it's more than just a fleeting fascination. Growing up by the sea, marine ecologist Shigeki Wada, an assistant Professor from Institute of Life and Environmental Sciences at the University of Tsukuba, found himself immersed in the wonders of marine life from an early age. The personal connection to the sea laid the foundation for a journey into marine biology research, a field as vast and complex as the oceans themselves. In today's rapidly changing world, the impacts of climate change on ocean ecosystems and the ways organisms respond to these changes are becoming increasingly evident. To delve deeper into this pressing issue, I had the opportunity to sit down with Dr. Wada.

Climate Change and Ocean Acidification: A Silent Crisis Below the Waves

Approximately 30% of the CO₂ in the atmosphere, contributing to global warming, is absorbed by the oceans. However, when excess CO₂ from the atmosphere dissolves in the ocean, it results in ocean acidification, causing a decrease in pH levels. pH measures acidity with lower values indicating higher acidity. This shift in pH impacts a variety of marine organisms, particularly corals and shellfish, which rely on calcium carbonate for their skeletons and shells. As the pH decreases, forming calcium carbonate becomes increasingly energy-consuming, leading to detrimental effects on these organisms. In regions with low pH levels, noticeable declines in shellfish and coral populations are evident. As Dr. Wada mentioned, "Predictions suggest that corals near Japan may vanish within the next 50-100 years due to these changes. The implications of such rapid shifts are alarming."

What Happens If Corals are Gone?

One might often hear about the significance of coral reefs, emphasizing that they serve as vital habitats for a multitude of marine species. About a quarter of all fish, at some stage in their life—often during their younger years—associate with coral reefs. However, the importance of these ecosystems extends beyond just fish. The reality is that various marine organisms are affected by rising CO₂ levels and declining pH levels. While the impact varies across species, with some benefiting and others suffering, the overarching trend suggests a concerning decrease in marine biodiversity. Organisms sensitive to these changes will gradually vanish, leaving behind only those resilient to ocean acidification, potentially leading to an overall decline in marine biodiversity, as explained by Dr. Wada in one of his research projects (Fig.1).

Fig. 1: Representative ecological communities at increasing pCO2 levels

The top panels represent intertidal communities associated with mean levels of 300, 400 and 1100 μatm pCO₂. The bottom panels represent subtidal communities associated with mean levels of 300, 400 and 900 μatm pCO₂ (Agostini et al., 2018). We can observe that the level of biodiversity decreases when the level of CO₂ increases in both intertidal and subtidal communities. 

Nature's Ally from the Ocean: Seaweed's Role in Combating Global Warming

In his research regarding the effects of environmental changes on coastal marine ecosystems, Dr. Wada aims to evaluate the potential impacts of ocean acidification and the role of seaweed in coastal ecosystems (Fig.2). Often overlooked in discussions about climate change, seaweeds possess an astonishing capacity to absorb carbon dioxide. While they are predominantly found in specific coastal areas worldwide, their efficiency in CO₂ absorption per unit area is unparalleled.

Fig. 2: Algal settlement in different levels of CO₂

Panels retrieved from high CO2 (a and b on day 44 and 72) and reference sites (c and d on day 44 and 72). At the high CO2 site, we observe that the panels were covered with a homogeneous brown biofilm at both time points. A difference in the composition of algal communities grown under different CO2 levels is also noticeable. Macroalgae (e) dominated on settlement panels at the reference site, while diatoms Triceratium sp. (f) and Biddulphia sp. (g) dominated at the high CO2 site (Wada et al., 2021). 

Highlighting the real-world implications of understanding seaweed's role, Dr. Wada emphasized that the ecological significance of seaweeds has only been recognized in recent years. In the absence of this understanding, human activities, such as coastal developments, can inadvertently devastate local seaweed populations. Tragically, during periods of rapid economic expansion, Japan has already witnessed the loss of an estimated 30% to 40% of its native seaweed ecosystems. Recognizing and appreciating the role of seaweeds in carbon absorption is paramount. Only with this knowledge can we truly value these ecosystems and ensure their preservation for the betterment of our planet.

Diving into Research: The Challenges and Fun of Undersea Exploration

Diving is an integral part of Dr. Wada's methodology. He regularly dives for durations of 40-50 minutes to observe and collect data (Photo 1). During his data collection dives, Dr. Wada often collaborates with overseas researchers. This international collaboration has offered him a fresh perspective on both the nuances of different work cultures and the research process (Photo 2). He fondly recalled the contrasts between his Japanese colleagues and those from Europe. "Japanese researchers have a precision to everything they do," he observed. "In contrast, my colleagues from France and Italy, while meticulous in their research, also prioritize enjoying the process." He recounted amusing instances of cultural differences, from the meticulous time management of his Japanese peers to the laid-back approach of his Italian collaborators, who might prioritize a quick cigarette or coffee before diving into work. Beyond the day-to-day research activities, Dr. Wada also observed differences in academic approaches. "Japanese researchers often adopt a step-by-step approach, building on accumulated data," he noted. "On the other hand, many overseas researchers dive directly into what's most intriguing about a topic. It's a direct, to-the-point approach that offers a refreshing contrast."

Photo 1: A scene of Dr. Wada (left) collecting data during his field work (obtained from Dr. Wada)

Photo 2: A scene of Dr. Wada (middle) having a discussion with researchers from overseas (photo by Yasuhito Hayashi)

Embracing the Unexpected: The Dynamic Paths of Scientific Inquiry

When asked about advice for budding researchers, Dr. Wada emphasized, "Life in research is filled with twists and turns. You often find yourself venturing into territories you hadn't charted, whether it's collaborating with individuals from different corners of the world or delving into topics that once seemed outside your purview." With a note of encouragement, he added, "So, to anyone stepping into this realm, my advice is simple: stay open to opportunities. If a path intrigues you, embrace it. Such an approach has unveiled numerous possibilities in my own journey. Especially in the early stages of your career, it's paramount not to confine yourself. That's the ethos I've adhered to, and it has been immensely rewarding."

As we journey through the mesmerizing depths of our oceans with experts like Shigeki Wada, it becomes abundantly clear that the intricate balance of marine ecosystems is both delicate and paramount. Let’s remember that every ripple of change in the vast ocean starts with a single drop. By understanding, respecting, and advocating for our oceans, we can be that drop, contributing to a wave of positive change.

References:

Agostini, S., Harvey, B.P., Wada, S., Kon, K., Milazzo, M., Inaba, K., & Hall-Spencer, J. (2018). Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone. Scientific Reports, 8, 11354. https://doi.org/10.1038/s41598-018-29251-7

Wada, S., Agostini, S., Harvey, B., Omori, Y., & Hall-Spencer, J. (2021). Ocean acidification increases phytobenthic carbon fixation and export in a warm-temperate system. Estuarine, Coastal and Shelf Science, 250, 107113. https://doi.org/10.1016/j.ecss.2020.107113

Wada, S., & Hama, T. (2013). The contribution of macroalgae to the coastal dissolved organic matter pool. Estuarine, Coastal and Shelf Science, 129, 77-85. https://doi.org/10.1016/j.ecss.2013.06.007