Welcome to the inaugural edition of our EuroMarine Researchers in the Spotlight series, where we engage in captivating conversations with prominent researchers within our network.

Today we welcome João Silva, Senior Research Fellow at the Centre of Marine Sciences (CCMAR), who led the RHODOCARB Workshop - Rhodolith beds in the Global Carbon Budget. We talked talked to him about his experiences as a Foresight Workshop lead for EuroMarine.


The main objective of the RHODOCARB workshop was to devise a research strategy for the evaluation of the rhodolith beds’ contribution to the marine carbon cycle. Lead experts addressed and aimed to resolve the fundamental knowledge gaps that currently prevent such evaluation. Stemming from multiple discussions among experts, and evidenced by the existing literature, it has become clear that knowledge is still dramatically lacking in three essential areas:

  • Distribution (mapping) and characterization (biological, physical and chemical)
  • Structural and functional diversity (including rhodoliths and associated flora and fauna)
  • Carbon flux dynamics and carbon storage capacity (metabolic activity, biogeochemistry, C and CaCO3 cycling)


  • Synthesis/review paper on the current state of the art regarding known rhodolith distribution, areal extension, depth distribution, associated fauna and flora and carbon fluxes.
  • Perspective paper outlining a research roadmap for the next decade, including approaches and methodologies designed to ensure the generation of comparable datasets in rhodolith-bed research
  • Building and strengthening of an international research network to ensure knowledge transfer to a global scale and creating the conditions for the preparation of large-scale research proposals.


This workshop emerged as a response to the UN Decade of Ocean Science. RHODOCARB represents a step forward in our understanding of marine systems and the services they provide, and provides valuable insights for the sustainable management of rhodolith beds.


João Silva is a Senior Research Fellow at the Centre of Marine Sciences (CCMAR) located in the south of Portugal since 2006. His main area of expertise is marine plant ecology and ecophysiology.

One of the focuses of his recent research has been on the ecological impacts of climate change on seagrasses and calcifying macroalgae. He has coordinated or participated in more than 35 national and EC-funded research projects and has authored over 60 peer-reviewed publications (h=27). He is also an Invited Assistant Professor at the University of Algarve, teaching Marine Plant Ecophysiology and Marine Botany.

EuroMarine: What does the term ecophysiology mean and how did you get so interested in this field of research?

Let me start by thanking you for this opportunity to convey some of my impressions regarding this experience, which was my first experience with EuroMarine. Referring to your question, ecophysiology is actually the use of the physiological explanation for how plants and organisms respond to environmental variables. It is a field of research that goes back to the beginning of plant physiology, which traditionally searched to describe the main physiological processes happening within plants. Ecophysiology came maybe right after that pressure to understand the response of plants to environmental stimuli and how that affects the internal processes of the plants nowadays.

This is where my interest in this field appeared in the context of climate change, including ocean acidification in the beginning, and more recently the onset of marine heat waves. I've developed most of my research in trying to explain and trying to look at how the physiological mechanisms of marine plants and the calcifying macroalgae respond to these dramatic changes in environmental conditions.

That can give us insights not just on how the organisms are responding nowadays, but it also has a predictive potential in the sense that we can experimentally simulate future scenarios based on the IPCC projections. We can try to anticipate how organisms by themselves will respond to future oceanic conditions.

EuroMarine: Can you give us an insight into the biggest ecological impacts and what they mean for seagrasses? What have you maybe seen in your research already?

It’s a very interesting question because actually climate change is a simple term for a very complex matter. When we refer to climate change, the first things that comes to mind in the case of oceans are acidification and heat waves, but of course there's other phenomena associated. Most of all usually these things don’t come alone. Often we have combination of these global, what you can call global stressors like acidification or heat waves, which often appear associated to local stressors which vary depending on location.

In some cases, these may be terrestrial runoffs that increase water turbidity, or it can be nutrient discharges by this or other reason that leads to a eutrophication phenomena. It's often the combination of multiple stressors; that is the challenge and of course reality. And it's also a bigger challenge for us to simulate these conditions. Because we are thinking about complex scenarios, which are very difficult to simulate in controlled conditions in Aquaria and mesocosm experiments. These are actually the questions for which we need answers. The effects of climate change are, of course, as diverse as the combination of potential factors. If you choose acidification, for example, seagrasses are more or less widely accepted to be sort of “winners” because these plants are limited in the amount of dissolved inorganic carbon that they have available in the ocean.

In the context of a higher atmospheric CO2 that then translates into also higher amounts of CO2 in seawater, these plants will respond positively in regard to photosynthesis and growth. In some cases however, and we've done some trials on that as well, the combination of heat waves with high CO2 can be a bit of a problem because CO2 stimulates metabolism, heat waves, on the other hand, tend to induce stress defense processes, and that sometimes provokes conflicts. These conflicts at firsthand are internal conflicts and often not translated immediately into external aspects. That's why it is so important to look at the physiology inside, because if we just stick to growth and density and all these common parameters, which are of course useful, we easily get misled and fail to understand the real causes, the underlying mechanisms that can be of concern.

EuroMarne: Can you briefly introduce the research topic that the RHODOCARB foresight workshop was focused on and also describe the significance of it in the field of marine science?

Rhodoliths are calcareous red algae, which are free living organisms in the sea floor. They are in many ways a very cryptic group both from their own existence and abundance. That is because there is growing evidence that the abundance of these algae is largely underestimated. We are finding new rhodolite beds all over the world. The abundance of these algae is probably much larger by several orders of magnitude than we currently believe. They grow underwater and not so much at shallow waters, like seagrasses. They often start at a depth like 20, 30, 40 meters and extend even, and extend deeper into deeper waters because they have very low light requirements and so they can grow.

These algae, cryptic in their abundance, are also cryptic in the sense of their ecosystem function and their role in the different ecosystems. They can be found almost from the poles to the equator and southern and northern hemisphere all over the oceans inhabiting quite distinct climatic regions exposed to quite different conditions. There are different species that compose these beds.

And then there's also the fact that what makes rhodolits a bit different from general marine plants and macroalgae is the fact that they have these calcareous structures; they are calcifying organisms and they deposit calcium carbonate in their growth process. In their life cycle, they deposit huge amounts of calcium carbonate in the space between the cells and in some cases within the cells.

If you take one of these algae, the dried weight of them is an average around 95 percent is calcium carbonate. They grow extremely slow because the calcium carbonate precipitation takes forever. These algae grow at rates like from half a millimeter to one millimeter per year; extremely low rates which also makes them live forever. A single individual can live for more than a hundred years. These are very stable benthic deposits of calcium carbonates and it is believed that they are the largest biogenic calcium carbonate deposits in the ocean.

Calcification in macroalgae is a process that occurs simultaneously with photosynthesis. While photosynthesis captures CO2, respiration in macroalgae generates CO2. Additionally, calcification in these organisms results in the precipitation of calcium carbonate, removing carbonate from seawater and depositing it within the organisms' structures. This process also releases carbon dioxide, which is typically promptly utilized for photosynthesis. However, from a chemical standpoint, calcification serves as a source of CO2.

Considering the metabolic impact of these organisms in water, it's essential to account for three simultaneous processes: photosynthesis, respiration, and calcification. The key aspect is the carbon budget, which is cycled among these processes. This budget is crucial for determining whether a rhodolith bed is autotrophic or heterotrophic, essentially deciding if it acts as a CO2 source or sink. This distinction is especially significant because these organisms play a crucial role in the global ocean carbon cycle, given their extensive coverage. While we have substantial knowledge about various populations, one consistent finding is the substantial variation between species and populations across different latitudes.

That brings another challenge which is the difficulty to extrapolate what we measure and observe in one population into another. For example, here in the south of Portugal, we have the only continental rhodolite bed in known in Portugal. The conclusions that we draw from this population here are totally different from the ones that we observe, for example, in Brazil.

Within our research group and laboratory, we've conducted extensive research in various regions, including mainland Portugal, the Madeira archipelago, the Canary Islands, the Mediterranean, and Brazil. Our findings have shown distinct patterns in rhodolith beds. Some of these beds, like the ones in Brazil, act as carbon sinks and are autotrophic year-round. In contrast, others experience periods of heterotrophy, especially during the winter, where they produce carbon rather than absorbing it. There are also cases that are more challenging to classify. These patterns are often associated with latitudinal changes, making it challenging to generalize findings from one community or population to another. That brings us to the biggest reason for this workshop, which was to gather the people working on these rhodolite beds, particularly the ones that are observing these carbon fluxes and how do they vary along the year.

Our aim has been to harmonize our findings and develop a comprehensive, global interpretation of these algae's role in the ocean carbon cycle. This effort involves collaborating with researchers from various countries to achieve a broader perspective. The researchers we collaborated with came from different regions. The question arises regarding whether their findings significantly differed from ours, based on the locations of their research. Were the results quite dissimilar or somewhat similar? The discussion is centred around how the diverse research findings contribute to this broader, more holistic understanding of the topic.

We assembled a small group of researchers primarily from within the EuroMarine community. The participants came from countries like Spain, Italy, France, the UK, Brazil, Sweden, and Norway. This gathering primarily involved European groups working on topics related to rhodoliths. Typically, these research groups focus on specific locations rather than diverse ones. The rhodolith research community itself is relatively small. Given the community's small size, our decision to bring these researchers together aimed to address topics related to carbon fluxes and biodiversity, even within this niche community. Despite its size, the community is known for its welcoming atmosphere.

This workshop aimed to address the issue of disconnected research efforts in the rhodolith community. The primary goal was to strengthen a sense of a working community interested in related topics by bringing together researchers. The ultimate aim was to create a research roadmap for the next few years in Europe and, if possible, worldwide. A fortunate coincidence allowed Brazilian partners to join the discussion.

EuroMarine: What were the main findings that emerged from this workshop and what was the roadmap that you established for the next couple of years?

The workshop's outcomes are still a work in progress, but it was fascinating that the results exceeded initial expectations. The workshop was set up with specific predefined questions in mind, and it effectively summarized the state of the art in rhodolith research. This includes an ongoing review paper that compiles worldwide knowledge on carbon cycling in rhodolith beds, providing a foundational understanding of the current state of research.

Another focus was on harmonizing the description of new rhodolith beds. As new beds are continually being discovered, each research group tends to have its own methods for mapping and characterizing them. The goal was to create a commonly agreed protocol or handbook for different groups to use when mapping in different regions. This protocol would enable the creation of interactive and analyzable maps, pooling information globally.

The workshop also aimed to develop recommendations for funding agencies and environmental management entities. This includes raising awareness about the significance of rhodolith beds and encouraging environmental agencies to engage in monitoring and preserving these ecosystems. Some of the species are already included in the European habitats directive, but there may be a need for revision given the increased knowledge about these species.

We arrived at an unexpected but significant conclusion: these rhodolith habitats have what we call a "cascading effect." This means that the mere presence of a rhodolith bed initiates a domino effect, encouraging the occurrence and growth of various associated populations.

This effect encompasses a wide range of organisms, including other algae that use rhodoliths as a substrate for attachment in mobile substrates. This is especially vital in areas like the archipelago and the Canary Islands, where the seabed is primarily muddy or sandy. When a rhodolith bed is present, biodiversity substantially increases because many other organisms take advantage of the three-dimensional structure and the complex morphology of rhodoliths for nesting, shelter, and a source of food. We've termed this phenomenon the "cascading effect," and there are numerous examples of how it leads to associations with seaweeds, invertebrates, fish larvae, and more. We are in the process of compiling these examples into a comprehensive paper that's nearly complete.

From a scientific perspective, the workshop exceeded our expectations, which is remarkable considering its relatively small scale and funding. It's truly impressive how much we've been able to achieve with such limited resources.

EuroMarine: Have you or are you planning to apply for additional funding to further develop this research?

We haven't applied for funding opportunities yet because none have been available. However, this was part of our planned course of action, as outlined in the workshop objectives. During the workshop, we effectively brought together various research groups from Europe, creating what can be described as a consortium.

The intensive three-day collaborative environment in close proximity laid the groundwork for this consortium. Our intention is to leverage this consortium to apply for funding from various sources, such as research projects, which align with our focus on mapping rhodolith beds.

In terms of funding instruments, we've found that European-wide calls, while numerous, often don't fit the size and scope of our research consortium. Many of these calls are too large for our specific project, and the available funding structures have evolved over time. Previously, there were intermediate-sized opportunities, but such options have become scarce.

As part of our future goals, we are actively working on proposing a cost action. This instrument has been successful in bringing researchers together and offering vital training opportunities in the past, as demonstrated in a previous cost action related to seagrasses. We believe that a cost action holds promise for our community, particularly in addressing the need for training and fostering collaboration among students and junior scientists.

Overall, the aim is to attract more individuals to the field and provide enriching opportunities within a broader community context. We recognize the importance of training and encouraging interdisciplinary exchanges, as it's essential for nurturing new talent in our field.

EuroMarine: Have you talked to policymakers or is there a plan of involving policymakers into this research project as well?

We are indeed interested in translating our research into actionable policy insights, but it's important to note that the workshop itself has concluded. However, we drew inspiration from a successful pilot project conducted by my group in Madeira. This project, funded through a LIFE grant for the outermost regions of Europe, focused on mapping and characterizing rhodolith beds in the marine protected areas of Madeira.

What made this project stand out was our approach of involving the Nature Conservation Authority from the project's inception. They became project partners and played a vital role in shaping the project's context. Among the project's deliverables, we crafted a comprehensive mapping, monitoring, and conservation plan, with the Nature Conservation Institute as a leading participant.

The significance of this achievement lies in the fact that conservation authorities often have the means to conduct monitoring and preservation activities but may lack the expertise, particularly in lesser-known ecosystems like rhodolith beds. We provided them with a detailed monitoring plan and offered training to their staff, including the technicians and field personnel responsible for implementation.

Since these marine protected areas were already monitoring various species, we essentially introduced a ready-made package for rhodolith bed monitoring. It was seamlessly integrated into their existing efforts and proved highly effective.

Our current strategy is to expand upon this successful model. However, this process primarily needs to be carried out at regional and, more importantly, national levels. Each country has its own set of agencies responsible for environmental management, making it challenging to implement a uniform European monitoring plan. Nevertheless, our goal is to replicate and extend these efforts to various environmental agencies.

While this endeavor may take time, we have a well-defined strategy, giving us a clear roadmap to follow. The key is to identify ways to navigate this path effectively, which we are committed to achieving. I hope this clarifies our approach, which aims to involve policymakers from the project's outset and translate scientific research into practical policy actions.

EuroMarine: What advice or suggestions would you give to your younger self if you were just starting up as a researcher?

Addressing your question, I must admit it's a complex one, perhaps the most challenging of all. My advice would be to actively engage with the global scientific community and avoid confining yourself to a narrow focus within your field. Step out of your comfort zone and broaden your perspective because, over the years, I've discovered that there's immense enrichment in looking beyond the confines of pure science. Consider the broader context in which your work operates. Understand where your research fits in not only within the scientific realm but also in the wider community. This perspective can give you a profound sense of purpose. In today's world, this purpose, this understanding of how your work contributes to society as a whole, is exceptionally significant. It transcends the act of conducting science for its own sake and aligns it with a more profound and meaningful mission.

I believe this insight is invaluable, especially for young researchers who are embarking on their scientific journeys. It encourages them to find the broader purpose of their work and recognize the positive impact it can have on society.