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We explore the entire tree of life on the research vessel MARIA S. MERIAN: animals, algae, bacteria, and viruses. The cruise focuses on the food web and ocean biodiversity. However, some animals, especially hunters such as squid and whales, are too big, fast or camera-shy for our instruments. To detect these top predators, we search for and collect genetic traces, so to speak, working as zoological forensic scientists. Ocean animals constantly lose cells and DNA when swimming, breathing, eating and defecating, resulting in the release of genetic material. We collect and identify this so-called environmental DNA (eDNA for short) using a method specifically developed to analyse DNA traces collected from environmental samples. Specific DNA sections, such as ribosomal DNA or genes essential for energy production, are analysed and exist in all animals. The same or similar essential genes are used for bacteria or unicellular organisms. These genes are later amplified from the samples via PCR and sequenced via next-generation sequencing technologies. The results are later compared to genetic databases to discover which species occurred in the environmental sample.

So, while our colleagues filter water samples to study phytoplankton and microplankton, we filter water from the CTD in parallel and analyse the DNA later in Kiel in the GEOMAR laboratories. Based on the specific DNA traces, we can determine the presence of certain species, such as the deep-sea cephalopods Histioteuthis and Heteroteuthis. Water sampled every 100 m from the surface down to the seafloor can show us at what depths cephalopods occur and allows us to predict what species of prey predatory whales may encounter during their dives. For this, we work together with cetacean specialists. At the same time, we also analyse the biodiversity of other organisms in the samples, which we could then compare to predict the prey of the cephalopods. Ultimately, we can also compare our genetic results with the distribution and abundance of the diverse species of plankton and animals identified by the MSM126 team members, each of whom has their own taxonomic speciality.

Minutes after deployment of the deep-sea lander with bait in the black nets at 1500m depth, the first guests arrived. Photo: ROV team GEOMAR

We are also carrying out an innovative eDNA experiment on the deep seafloor during our expedition. For this, the deep-sea robot or ROV has deployed a deep-sea lander with bait on the seafloor to mimic the deposition of a carcass from the overlying water column. This carcass attracts and nourishes many organisms since deep-sea bottom organisms largely depend on food from the overlying water column. We returned to this site several times with the ROV robot to take sediment cores and water samples. These samples are immediately preserved on board for future eDNA analysis. The experiment will investigate 1) which species are attracted to the food deposition event and 2) to what extent the biodiversity and ecosystem of animals and bacteria change over time after the food deposition event.

Environmental genetics, the search for traces in the sea, is a modern addition that supports various classical approaches in marine research and contributes new information and perspectives. It is, therefore, also an essential part of MSM126 to combine research from different disciplines and gain new insights.

So-called push corers are used to collect sediment cores with the ROV robot. Photo: ROV team GEOMAR

Forensics in the sea

Ocean Acidification

How Many Species of Hammerhead Shark Are There?

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Hammerheads are some of the most recognizable fish in the sea—their iconic “hammer” head is unlike the head of any other shark out there. But did you know there are actually several species of hammerhead?

Get the scoop on these spectacular sharks!

What is a hammerhead shark?

Let’s start with the basics. Hammerheads are elasmobranchs, which are cartilaginous fish—meaning they have skeletons made of cartilage rather than bone. Other elasmobranchs include rays, skates and other sharks.

More specifically, hammerheads are fish within the family Sphyrnidae, defined by their hammer-shaped head called a cephalofoil. The cephalofoil serves a few purposes, including making it easier for hammerheads to maneuver when going after prey (although, the downside is it might not be as hydrodynamic as previously thought). The wide shape of the cephalofoil also means more surface area for sensory organs called ampullae of Lorenzini, which detect electrical fields and help the sharks find prey, including ones buried in the sand.

How many species of hammerhead shark are there?

Within the hammerhead family, there are two genera, or subgroups: Sphyrna, which has eight species, and Eusphyrna, which has only one species. The smallest species within the hammerhead family reaches to about three feet long, where the largest can grow to 15 feet or more.

Hammerhead sharks swims in the ocean

Read on for a spotlight on a few well-known—and some lesser-known—species of hammerheads.

Winghead shark (Eusphyra blochii)

Status: Endangered

Winghead sharks are the only species in the genus Eusphyrna, which is special already. If that wasn’t enough, they have one of the most dramatic cephalofoil shapes of all the hammerhead sharks—hence the “wing” in its name. They’re found in the Indo-Pacific region from China to Australia and can reach a maximum of six feet in length. They like to hang out in relatively shallow water and snack on small bony fish, crustaceans and cephalopods such as cuttlefish, octopus and squid.

Great hammerhead (Sphyrna mokarran)

Status: Critically endangered

Great hammerheads are the largest—and arguably most iconic—of the hammerheads. They are found in coastal and pelagic habitats in temperature and tropical regions around the world. They’re somewhat unusual among other coastal sharks because they will regularly go after other sharks and rays rather than primarily sticking to smaller bony fish or crustaceans. They will also go after larger prey and can consume prey about 25% their body size.

Scalloped hammerhead (Sphyrna lewini)

Status: Critically endangered

Scalloped hammerheads can be somewhat easily confused with the great hammerhead, but their cephalofoil is slightly “wavier”—hence the “scalloped” part of their name. Similar to greats, they are found around the world in tropical and temperate regions. During their seasonal migrations, they travel in large schools with hundreds of other scalloped hammerheads.

Bonnethead (Sphyrna tiburo)

Status: Endangered

The bonnethead is the smallest member of the hammerhead family, only reaching about four feet in length. They are found throughout the Western Atlantic, Eastern Pacific and Gulf of Mexico and are commonly seen in shallow bays, seagrass beds and sandy areas inshore. Unlike the other hammerheads, which are strictly carnivores, bonnetheads have been found to eat seagrass. One study found seagrass made up to 62% of a bonnethead’s stomach contents! That’s one shark that understands the importance of eating your veggies.

You might have picked up on something else these sharks have in common: All are considered endangered or critically endangered. Sharks like hammerheads depend on a sustainable ocean in order to thrive—visit Ocean Conservancy’s Action Center to see how you can take action to support a healthy ocean for all ocean animals.

The post How Many Species of Hammerhead Shark Are There? appeared first on Ocean Conservancy.

How Many Species of Hammerhead Shark Are There?

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Ocean Acidification

Watch Out for Nettles

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Sometimes when you live in a big city like Baltimore, you forget that you are still living in a vibrant ecosystem. One of my favorite things to do with friends is to spot some of the incredible sea creatures that live in our harbor. One of my favorite animal neighbors is the Atlantic bay nettles, which were recently discovered to be a different species of sea nettle that lives in the Chesapeake Bay. You can commonly see these gorgeous jellyfish here in the summer and fall. They have beautiful long tendrils that dance around as they glide in a pulsing motion. But before you get too lured in by this mesmerizing façade, I should warn you: Atlantic bay nettles, and their other sea nettle relatives, can be dangerous.

Hidden in the beautiful frills and ribbons of a sea nettle’s tentacles and arms are stinging cells. For their prey these stings can result in paralysis and death. Once stunned the jellyfish will use its arms to move the unfortunate creature into its mouth for snack time. If you’re not a fish egg, worm or other sea nettle prey, that doesn’t mean you don’t still have to worry about its stings. In humans, a sea nettle sting can leave a rash with a painful and burning sensation.

What do you do if you’re one of the unlucky few who gets stung? Start by looking through your kitchen cabinets. Cleaning the sting with a mixture of ocean water and baking soda or meat tenderizer is the most common recommendation for sea nettle stings. If you don’t want to worry about storing these items in your beach bag, its best to check on the local conditions before you jump in. For fellow Chesapeake Bay residents, you can check this NOAA Map to see the probability of encountering our local Atlantic bay nettles at your local beach.

If you do encounter a sea nettle on the beach, remember to look, don’t touch. Jellyfish aren’t great swimmers so they aren’t going to aim for you, but they can’t easily swim out of the way either. The best way to share our water with them is to be aware of your surroundings and give them a wide berth.

Sea nettles

There are actually a lot of pros to sharing our waters with sea nettles and other related sea nettles. They provide protection to some of the other animals around them. Pacific sea nettles give young cancer crabs a ride into shore as well as provide a snack as these crabs eat some of the mucus from their arms. When a predator scares a Pacific butterfish, they find safety in a sea nettle’s bell.

For my fellow residents of the Chesapeake Bay, we can thank our Atlantic bay nettles for protecting our oysters. Bay nettles eat comb jellyfish which are key predators for oyster larvae. In return, oyster beds offer a safe home for baby bay nettles to grow. Bay nettles can help our local oyster populations which in turn helps clean the waters in the bay. Oysters are filter feeders and can filter up to 50 gallons of water a day.

Sea nettles

In the Pacific, brown sea nettles are the favorite food of the endangered leatherback sea turtle. These turtles journey to the west coast every spring and summer to find the very jellies we humans would prefer to avoid. These sea turtles don’t have to worry about getting stung, however. Their scales and shells protect them on the outside, and papillae, a layer of spines from their throat to their esophagus, protect their insides.

A sea turtle’s love for jellyfish can also be its downfall and is an important reminder of the other dangers of human interaction with our ocean. Floating plastic bags that end up in the ocean can easily be confused for jellyfish and eaten by turtles. Scientists have found plastics in all seven species of sea turtles on the planet. We can play an important role in protecting our beaches, beyond dodging sea nettles, by keeping our ocean free of plastics. Take action now to tackle the plastic pollution crisis.

The post Watch Out for Nettles appeared first on Ocean Conservancy.

Watch Out for Nettles

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Ocean Acidification

Welcome Aboard SO305: BIOCAT-IIOE 2

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On 9 April 2024, 39 scientists from esteemed institutions such as the University of Hamburg, GEOMAR Helmholtz Centre for Ocean Research Kiel (GEOMAR), Helmholtz Centre hereon, University of Southern Denmark (SDU), and Leibniz Institute for Tropospheric Research (TROPOS) embarked on the research vessel Sonne for the BIOCAT-IIOE 2 (SO305) research expedition. The team comprises experts in marine biogeochemistry, microbiology, physical oceanography, and atmospheric chemistry.

The BIOCAT-IIOE 2 (SO305) expedition aims to decipher the biogeochemical processes occurring in the Bay of Bengal. This region, located in the northeast basin of the Indian Ocean, features a prominent oxygen minimum zone (OMZ) with dissolved oxygen concentrations nearing anoxic levels and experiences a heavily polluted atmosphere during spring. This research is an important contribution to the international programs 2nd International Indian Ocean Expedition (IIOE-2) and the Surface Ocean-Lower Atmosphere Study (SOLAS). Over the next five weeks, we will be investigating the efficiency of the biological pump, the nitrogen cycle within the OMZ, air-sea exchange fluxes of trace gases, and aerosol deposition.

Originally scheduled to depart from the Port of Colombo on 10 April, our departure was postponed due to the delayed arrival of our containers containing our materials and equipment. During this wait, we took the opportunity to get to know more our colleagues and explore the city of Colombo.

Some of the scientists enjoying the rooftop view in a hotel in Colombo before our containers arrive.

On 13 April 2024, with our containers finally in hand, we have set sail from the Port of Colombo, commencing our measurement campaign in the Bay of Bengal. We anticipate reaching the port of Singapore on 22 May 2024.

Stay tuned for updates as we navigate the challenges and discoveries that await us on SO305. As we embark on this important scientific expedition, we are excited to investigate the complexities of the Bay of Bengal’s biogeochemical processes. The collaboration between experts from various institutions promises a multidisciplinary approach that will yield valuable insights into this unique marine environment.

Welcome Aboard SO305: BIOCAT-IIOE 2

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