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by Dr. Gesa Schulz

Group photo of scientists from the University of Hamburg— Leandro Nazzari, Tjark Andersch, and Dr. Gesa Schulz. (Photo by Isabell Schlangen)

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons in the atomic nucleus. Therefore, isotopes differ in their atomic mass.  They are divided into stable isotopes and unstable isotopes, with the latter exhibiting radioactive decay over time. The analysis of stable isotopes is a frequent used tool in the natural sciences, as it allows to determine sources and transformation processes. Even if the differences in the atomic masses are very small, they still lead to a different “reactivity” of the different isotopes of an element. The chemical bonds between so-called “heavy” isotopes, which have more protons than their “light” relatives, are stronger and therefore heavy isotopes react slower. An example: in microbiological turnover, microorganisms generally prefer the light isotopes and leave the heavy stronger bounded isotopes behind. This process is called “kinetic fractionation” and it enables us to use isotope analysis to investigate turnover processes and sources of elements.

Nitrogen isotopes: The lighter 14N has only seven protons and seven neutrons in the atomic nucleus, whereas 15N has eight neutrons and is therefore heavier.

At SO305, we are studying the nitrogen cycle. Nitrogen is one of the most important elements for biological systems, as it is an essential nutrient for all organisms. Nitrogen exists in various forms, which can be reactive or non-reactive, and can be rapidly converted by microorganisms. However, most organisms can only process reactive nitrogen. If only limited amounts of reactive nitrogen are available, life in the ocean is “nitrogen-limited”. Nitrogen has two stable isotopes: the more abundant light 14N (99.635 %) and the rare heavy 15N (0.365 %).

In the Bay of Bengal, nitrogen is important as its turnover processes are sensitive to oxygen. A pronounced zone with low oxygen levels already exists here and we currently investigate how the increasing nitrogen inputs caused by anthropogenic impacts change the occurring processes. If oxygen levels fall below a critical threshold, nitrogen degradation can occur, in which microorganisms adapted to low oxygen concentrations convert reactive nitrogen to unreactive N2. Around 30-50 % of all reactive nitrogen loss currently takes place in oxygen minimum zones, although they only account for around 0.1 % of the ocean volume. In the Bay of Bengal, this critical threshold has not yet been reached, but the system may be approaching a tipping point due to increasing inputs and climate change.

As the working group “Biogeochemistry in the Earth System” of the University of Hamburg in cooperation with “Aquatic Nutrient Cycles” of the Helmholtz Center Hereon, we study the nitrogen cycle with the help of stable isotopes: we take samples for the natural stable isotopes in the water column and filter large quantities of water to determine the isotopes of nitrogen bound to the particles in the water. We cannot measure the isotopes on board, we take all our samples back to Germany. During the cruise, we are mainly filtering. Either small volumes via syringe filters to take the frozen filtrates back home, or large volumes for the filters on which we analyze the particulate nitrogen. 

In addition to the filtration, we also use isotopes in incubation experiments in which we determine process rates. We do not measure which isotopes occur naturally, but instead label our samples with heavy 15N nitrogen. Over time, we track the turnover of the heavy isotope and use this to calculate the process rates.

At the end of the trip, we are faced with large quantities of frozen and cooled samples (approx. 80 liters of water and 200 filters as planned) that must be transported back to Germany to be measured for their isotopic composition in the lab.

https://www.oceanblogs.org/so305-biocat-iioe2/2024/05/06/isotopes-a-multitool-of-biogeochemistry-and-how-we-use-them-on-so305/

Ocean Acidification

METEOR Sets Sail on Its Final Voyage

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Welcome to the M219 ocean blog!

Here, we will share updates and stories about the scientific work taking place during this research expedition. We also hope to offer a glimpse into daily life and work at sea.

For many members of the scientific party, this is their first time aboard METEOR. It will also be their last, as METEOR is embarking on its final voyage before retiring from service as a German research vessel after more than 40 years at sea. Over the course of its distinguished career, METEOR has travelled more than 1.7 million nautical miles, which is equivalent to more than 8 times the distance between the Earth and the Moon. Throughout those decades the vessel has supported countless scientific discoveries and generations of marine scientists. We are very grateful and honored to be part of the final chapter of this remarkable ship’s history and to accompany her on the last few thousand miles of her legendary journey.

Planned cruise track for the research expedition M219.

The scientific program of this cruise focuses on long-term observations of ocean currents off the coast of Brazil and at the equator, as well as interdisciplinary measurements near the Cape Verde Islands. At all these sites, GEOMAR has maintained observational programs for the past 10 to 20 years. Over the next four weeks, we will introduce these regions and the measurements carried out there in more detail. But first, let’s look at what happened in Brazil before the cruise began.

On Thursday, May 28, many of the scientists and students left the hotel early in the morning to attend a seminar at the Universidade Federal de Pernambuco (UFPE), celebrating the long-standing scientific collaboration between Brazil and Germany.

The seminar was opened by Prof. Dr. Marius Müller, a former student at GEOMAR and now a professor for biological oceanography at UFPE. These meetings have become a valued tradition, having been organized for more than 20 years by now. This year marked the 9th edition of the seminar since its inception over 20 years ago.

A total of 8 scientists and students from Brazil, Germany, and the U.S. presented their research on various aspects of the tropical Atlantic Ocean. We would like to thank Marius Müller, Doris Veleda and all the Brazilian scientists and students who helped organize the seminar and provided such a warm welcome. We greatly enjoyed the exchange of ideas and look forward to celebrating the 10th seminar in the years to come.

Group picture at the 9th Brazil-German seminar at the Universidade Federal de Pernambuco (UFPE). Photo: Nadja Baumann

After the seminar we returned to the hotel, but there was little time to rest. Later that same day, the captain of METEOR and the German Consul General in Recife hosted a reception aboard METEOR in the Port of Recife.

The event brought together members of the scientific party, representatives of local institutions, and guests from the Brazilian and German scientific communities. It provided an excellent opportunity to celebrate the long-standing partnership between the two countries.

Reception onboard of R/V METEOR to celebrate the German-Brazilian collaboration. Photo: Nadja Baumann

On Friday, May 29, the scientific party finally boarded METEOR. There was little time to settle into our cabins and workspaces, as preparations for departure were already in full swing. We left the Port of Recife as soon as possible and at around 1pm METEOR set sail and began the final voyage of her remarkable career.

About 12 hours after leaving port, we arrived at our first station. Thanks to the dedicated efforts of technical and scientific teams, all instruments had been installed and prepared in time for the start of operations. This station marked the beginning of our observational program off the coast of Brazil, which includes the deployment and recovery of tall moorings as well as CTD measurements. An intensive first week lies ahead, with a demanding schedule of measurements and mooring operations. After months of planning and preparation, everyone is excited to finally begin the scientific work and make the most of the final weeks aboard METEOR.

Leaving the port of Recife on May 29th, 2026. Photo: Peter Brandt

METEOR Sets Sail on Its Final Voyage

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Ocean Acidification

All About Gobies

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There are more than 2,000 species of gobies (Gobiidae) known to science today, making them the largest family of fish in the ocean. But these small creatures are far more complex and essential to marine ecosystems than first meets the eye. Found all around the world in brackish, fresh and salt water in tropical and subtropical regions, they are an astonishingly diverse group of fish with several curious characteristics that set them apart.

Most gobies are quite small and don’t usually measure more than six inches long. Measuring just about eight millimeters long, the dwarf pygmy goby (Trimmatom nanus) is not only the tiniest goby known to science but also one of the smallest of all fish species in the world.

Primarily bottom-dwellers, gobies are known to be excellent foragers and have evolved expert burrowing behaviors over time. As they sift around looking for food like copepods, seaworms and tiny crustaceans, their movement helps to aerate sediment and keep algae in check. Some are even known to be “cleaner fish,” snacking on parasites they remove off larger creatures. It’s like a spa day for the animal being cleaned and a choose-your-own-adventure buffet for the gobies. Studies also show that cleaner goby activity is largely tied to the microbial health of coral reefs, showcasing that even the tiniest of species are essential to functioning marine ecosystems.

Gobies have some unique aspects to their anatomy, too. First, their fused pelvic fins are designed to help them form a strong suction cup to perch on coral reefs, rocks and other ocean terrain amidst turbulent currents. Some freshwater species are even known to use this suction to climb waterfalls. It may come as no surprise then that gobies are cousins to mudskippers, animals known to “walk” through mud. There are more species-specific features that set certain gobies apart. From the use of bioluminescence to symbiotic relationships with shrimp, the adaptations within the goby family are truly wide-ranging. Some species have even been found to use marine terrain memorization to navigate back to the tide pools where they were born. Isn’t nature mind-blowing sometimes?

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Gobies have equally complex and varied behaviors. Male gobies are infamous for being territorial protectors of their nests. Many larger males are known as “guarders;” these hopeful fish make careful nests to attract a mate, and once fertilization occurs, guarders will remain diligently near the nests to keep eggs safe. However, there’s another type of male goby that complicates this dynamic. These other males are known as “sneaker gobies” and are called that for one reason: They’re sneaky! If guarder gobies aren’t careful, sneakers can creep into the nest, fertilize some of the eggs and quickly escape. As if on an underwater episode of Maury, guarder males who aren’t careful could end up unknowingly babysitting little gobies that aren’t their actual offspring.

Gobies serve as indicators of ecological health and are essential to keeping delicate food webs in check. Unfortunately, many changes in our ocean threaten their ability to survive and thrive today. Coral bleaching and degradation endanger the health of one of their key habitats, and a combination of warming waters and coastal development can make it difficult for both juvenile and adult gobies to survive and thrive.

Healthy gobies mean a healthy ocean. Their essential role in marine ecosystems demonstrates that even the tiniest creatures play a major role in helping hold together the beautiful yet fragile habitats that make up our beloved ocean. Visit Ocean Conservancy’s Action Center and join the movement to protect our blue planet today and for years to come—from the tiniest goby to the largest whales, our ocean is counting on us.

Lemon Gobies Inhabit an old bottle

The post All About Gobies appeared first on Ocean Conservancy.

All About Gobies

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Ocean Acidification

Do You Know the Difference Between El Niño and La Niña?

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Recently, you may have heard about something called “El Niño.” But what exactly is El Niño and its sibling “La Niña”? Why do these terms seem to emerge from the depths of the scientific community and drop into popular vocabulary every few years? And how are they connected to extreme weather and our ocean?

What Are El Niño and La Niña?

El Niño and La Niña are part of a natural climate pattern in the tropical Pacific called the El Niño-Southern Oscillation, or ENSO. These two phases are different sides of the same coin, creating equally extreme shifts in temperature and air pressure.

El Niño occurs when surface water in the equatorial Pacific becomes warmer than average and easterly winds weaken. La Niña is the opposite: cooler-than-normal sea surface temperatures and stronger easterly winds. ENSO cycles can last up to seven years. El Niño and La Niña significantly impact weather patterns in all corners of the globe, often leading to more extreme weather, storm frequency and intensity.

A strong El Niño can cause flooding in some regions and drought, heat waves and wildfires in others. It often causes crop losses, coral bleaching and marine die-offs due to unusually warm ocean temperatures. El Niño tends to suppress Atlantic hurricane activity, though it increases the risk of heavy precipitation and harm to fisheries elsewhere. In the Northern Hemisphere, El Niño typically builds between March and June, peaks in December, and weakens by February.

La Niña, by contrast, often fuels an active Atlantic hurricane season and increases tornado frequency across the southern United States. Like El Niño, it builds in spring and peaks around December.

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Predicting ENSO

In 1923, the physicist Sir Gilbert Walker discovered the “Southern Oscillation,” or large-scale changes in sea level pressure across the tropical Pacific. However, it wasn’t until the late 1960s that the metorologist Jacob Bjerknes found that the changes in the ocean and the atmosphere were connected, and the hybrid term “ENSO” was born. In 1974, researchers at Oregon State University attempted to predict ENSO for the first time.

Modeling has greatly advanced since the early days. Today, scientists at the National Oceanic and Atmospheric Administration (NOAA) issue regular predictions about ENSO, which are now more accurate than ever.

NOAA gives a one-in-four chance that an El Niño could reach “very strong” intensity later in 2026, qualifying it as a “super El Niño.” This threshold has been crossed only a handful of times in recorded history, each triggering droughts, floods and record temperatures across multiple continents. NOAA’s data and models deliver life-saving early warning forecasts, like that of the predicted super El Niño, which allow communities to better prepare for and respond to extreme weather events.

a graphic depicting the el niño and la niña phenomena

Take Action

Every American, regardless of where they live, depends on NOAA’s scientists and professionals, whose work spans from the ocean floor to the far reaches of space. Unfortunately, NOAA is under threat. The Trump administration has proposed billions of dollars in cuts to the agency, which could weaken weather forecasting, disrupt fisheries management and stall critical ocean research, putting American lives and global scientific leadership at risk.

Ocean Conservancy is committed to working with NOAA to keep the public informed on climate and ocean science. We all benefit from a healthier ocean, and investing in research is the most effective way to restore ocean health and reduce the impact of severe  weather events caused by El Niño and La Niña. Our ocean is not partisan, and protecting it requires all hands on deck and all sides of the aisle. Now, it’s more important than ever to demand that members of Congress prioritize our ocean. Add your name now.

The post Do You Know the Difference Between El Niño and La Niña? appeared first on Ocean Conservancy.

Do You Know the Difference Between El Niño and La Niña?

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