The Antarctic continent and its surrounding ocean are crucial in regulating the climate and global biogeochemical cycles. For example, the circumpolar current around Antarctica connects the Atlantic, Indian, and Pacific oceans and is part of the so-called thermohaline circulation, which redistributes heat between the equator and the poles. Furthermore, Antarctic ice represents 70% of the planet’s freshwater reserves. Visiting Antarctica makes you much more aware of these global connections.

The Antarctic marine ecosystem has many interesting features. Phytoplankton, the mainstay of the food web, displays great diversity. Furthermore, in the Antarctic Ocean, both areas of high production, generally close to the coasts, and relatively poor areas have been shown to be lacking in iron, an essential micronutrient for microalgae. The presence of sea ice is also very important; if it does not have a significant layer of snow on top, light can penetrate and allow microalgae to grow on its underside and in the canaliculi within the ice. Krill, a crucial component of the Antarctic food web, feed on phytoplankton and in turn constitute the basis of the diet of many fish and other marine animals such as seals, whales and penguins. During the winter, krill can survive thanks to the microalgae that inhabit the underside of the ice, which represent a concentrated food source. Therefore, the decline in sea ice caused by climate warming in certain parts of Antarctica represents a major threat to krill populations and the organisms that depend on them.

To put it simply, phytoplankton is a group of microscopic, single-celled organisms that live suspended in water and possess chlorophyll. These microorganisms play a role in the sea similar to that of plants on land; they use solar energy, water, carbon dioxide and nutrients to produce organic matter and reproduce. They are the primary producers of the pelagic (i.e., open-water) food web, which includes animals such as fish, mammals and seabirds at its upper levels. Phytoplankton includes cyanobacteria and a wide variety of microalgae that are adapted to different marine conditions. For example, diatoms have a silica cell wall, with an elegant microstructure that has inspired nanotechnological applications; they thrive in turbulent, nutrient-rich waters and are the main protagonists of late winter-early spring phytoplankton blooms in seas such as the Mediterranean. Coccolithophores have a covering of calcareous platelets that can be extremely beautiful. Other microalgae, such as dinoflagellates, have flagella that allow them to change their position in the water column and can grow in stratified and poor waters.

The Mediterranean has a temperate climate, with strong seasonality and significant inter-annual variability. I have participated in many campaigns in this sea and have encountered a wide variety of situations; we all know that a given week in March, for example, can be colder or warmer in one year than in another. Therefore, to document the effects of climate change on a given variable (such as temperature or sea level), long data series are needed that allow us to separate long-term trends (increase or decrease) from small-scale fluctuations. For more than 50 years, Josep Pascual has been collecting seawater temperature data at various depths at a station located one mile off the coast of L’Estartit, Spain, in addition to recording sea levels and measuring various meteorological variables. This is currently the longest series of reliable data in the Mediterranean. These values have been analyzed by various oceanographers, including colleagues from my institute and show that, in surface waters, the temperature has increased at a rate of 0.28°C per decade; at the same time, the sea level has risen by about 3 mm per decade. One of the consequences of this warming has been that marine heatwaves have become more frequent and have caused die-offs of sessile organisms such as gorgonians and corals. These are, of course, worrying observations.

Furthermore, the marine ecosystem of the Mediterranean (and other seas) has for years suffered the impacts of pollution, overfishing, and other factors derived from human activity, which endanger both marine biodiversity and the services the sea provides us.

Since retiring, I have continued my research as an associate professor (emeritus); in addition to working on topics left over from my previous campaigns, I collaborate on projects led by younger colleagues. For example, earlier this year, together with several co-authors, I published a paper on the relationships between the hydrographic structure of the water column and the chlorophyll maximum that occur at a certain depth in stratified waters. In one of my current projects, we are studying the physiology and ecology of populations of a benthic (i.e., substrate-attached) microalga, Ostreopsis cf. ovata, which inhabits many temperate coastal areas around the world, including the Mediterranean. Ostreopsis cf. ovata produces a variety of toxins and its blooms on the coasts of Catalonia and elsewhere in the northwestern Mediterranean have been associated with episodes of respiratory irritation. Among other topics, the study aims to determine what environmental conditions favor the growth of this microalgae, what toxins may be responsible for respiratory illnesses and how these toxins pass from the marine environment to become aerosolized.

Comments can be made on various matters. Of course, it’s important to be curious and ask questions; a scientific career requires significant dedication, but it has its rewards, including contributing to our understanding of the world around us and perhaps, directly or indirectly, to human welfare. Regarding what is now called a gender perspective, I would tell young women who are drawn to science to pursue their interest and ignore negative stereotypes. From a practical point of view, I would recommend that young people study hard and learn English and computer science. Aside from the importance of having good preparation, they must keep in mind that if they later have to apply for scholarships to pursue research, their grades in college can play a decisive role. The issue of protecting the oceans and nature in general requires, on one hand, knowledge and on the other, what we might call activism, to confront purely economic interests and try to translate this knowledge into a sensible treatment of the natural environment.