Sea butterfly life cycle threatened by climate change

An adult sea butterfly, a tiny free swimming sea snail.
Photo Credit: Victoria Peck – British Antarctic Survey

Shelled pteropods, commonly known as sea butterflies, are increasingly exposed to ocean changes, but some species are more vulnerable to this threat. In a new study, published this month in the journal Frontiers in Marine Science, British Antarctic Survey (BAS) scientists examining pteropod life cycles in the Southern Ocean have found that some species might be more vulnerable to this threat due to different timings of their life cycle.

Sea butterflies are tiny, free-swimming sea snails, which are an important part of the marine ecosystem. They are also vulnerable to climate change as their shells are sensitive to ocean acidification. Now, a team of researchers led by BAS has examined the life cycles of two free-swimming sea snail species. They found that one is less vulnerable to changes in the Southern Ocean than the other, which could affect the sea snails on a population level and in turn impact the marine ecosystem.

The world’s oceans absorb approximately a quarter of all carbon dioxide (CO2) emissions. During absorption, CO2 reacts with seawater and oceanic pH levels fall. This is known as ocean acidification and results in lower carbon ion concentrations. Certain ocean inhabitants use carbon ions to build and sustain their shells. Pteropods, which are important components of the marine ecosystem, are among them.

Sea anemone’s sweet efforts help reef ecosystems flourish

KAUST researchers have discovered how corals can thrive in nutrient-depleted oceans. Their study shows how sea anemones are able to recycle the essential nutrient Nitrogen.
Photo Credit: Morgan Bennett-Smith / King Abdullah University of Science and Technology

Tropical oceans are known for being low in nutrients, yet they support incredibly diverse and thriving reef ecosystems created by symbiotic cnidarians such as corals and anemones. This intriguing contradiction, referred to as the Darwin Paradox, has fascinated scientists ever since Charles Darwin first described it in 1842.

A group of researchers from KAUST conducted a study on sea anemones called Aiptasia. They found out that Aiptasia uses the sugar it gets from its partners to recycle waste in its body and survive in places where there are not many nutrients.

According to Guoxin Cui, a research scientist who worked on the project with Manuel Aranda, many studies in the past have tried to figure out where the limited nutrients in the ocean come from, especially nitrogen which is rare.

Guoxin Cui explains that some studies about coral have suggested that the partnership between coral and algae creates areas with lots of nutrients. But until now, researchers didn't fully understand how these organisms were able to create such large ecosystems.

Like ancient mariners, ancestors of Prochlorococcus microbes rode out to sea on exoskeleton particles

New research suggests the Prochlorococcus microbe’s ancient coastal ancestors colonized the ocean by rafting out on chitin particles.
Illustration Credit: Jose-Luis Olivares/MIT
(CC BY-NC-ND 3.0)

Throughout the ocean, billions upon billions of plant-like microbes make up an invisible floating forest. As they drift, the tiny organisms use sunlight to suck up carbon dioxide from the atmosphere. Collectively, these photosynthesizing plankton, or phytoplankton, absorb almost as much CO2 as the world’s terrestrial forests. A measurable fraction of their carbon-capturing muscle comes from Prochlorococcus — an emerald-tinged free-floater that is the most abundant phytoplankton in the oceans today.

But Prochlorococcus didn’t always inhabit open waters. Ancestors of the microbe likely stuck closer to the coasts, where nutrients were plentiful and organisms survived in communal microbial mats on the seafloor. How then did descendants of these coastal dwellers end up as the photosynthesizing powerhouses of the open oceans today?

MIT scientists believe that rafting was the key. In a new study they propose that ancestors of Prochlorococcus acquired an ability to latch onto chitin — the degraded particles of ancient exoskeletons. The microbes hitched a ride on passing flakes, using the particles as rafts to venture further out to sea. These chitin rafts may have also provided essential nutrients, fueling and sustaining the microbes along their journey.

Singing humpback whales respond to wind noise, but not boats

UQ researchers recorded humpback whales off the Queensland coast for the study.
Photo Credit: Mike Doherty

A University of Queensland study has found humpback whales sing louder when the wind is noisy, but don’t have the same reaction to boat engines.

Research lead Dr Elisa Girola from UQ’s Faculty of Science said this quirk of whale evolution could have consequences for breeding and behavior.

“Humpback whales evolved over millions of years with noise from natural sources but noise from man-made vessels is foreign to their instincts,” Dr Girola said.

“It’s a surprising finding given engine noise has a similar frequency range to the wind.

“It’s possible the whales are picking out other differences such as wind noise being broadband and the same over large areas, while vessel noise is generated by a single-point source with specific peaks in frequency.

“We don’t know yet if this lack of response to boat noise is making whales communicate less effectively or making breeding practices more difficult.

Researchers Track Endangered Nassau Grouper Eggs with Underwater Microscope

Nassau grouper spawning aggregation off Little Cayman, Cayman Islands. Credit: Jason Belport
 Photo Credit: Grouper Moon Project

Scripps Oceanography researchers show fertilized eggs stayed local, but in some years drifted to nearby islands.

Each winter off the western tip of the Caribbean island of Little Cayman, thousands of endangered Nassau grouper gather to spawn under the light of the full moon. The fish pack the coral reef and when the ritual begins individual females dash out of the fray straight up towards the surface with multiple males in pursuit. During these vertical bursts, females release their eggs and the males jostle to fertilize them, leaving milky plumes drifting in the moonlit sea.  

These precious fertilized eggs are the engine that powers the still-limited recovery of this critically endangered species that is a key reef predator and was once the target of an important fishery in the Caribbean. But where do these eggs end up after they’re cast adrift? 

Scientists at the University of California San Diego’s Scripps Institution of Oceanography, Oregon State University (OSU), and the conservation organization Reef Environmental Education Foundation (REEF) teamed up with the Cayman Islands Department of the Environment to address this question by physically tracking clouds of tiny, transparent Nassau grouper eggs through the night with an underwater microscope developed by Scripps Oceanography Marine Physical Laboratory scientist Jules Jaffe. 

Fish thought to help reefs have poop that’s deadly to corals

A coral-eating butterflyfish on a Moorea reef in July 2019.
Photo Credit: Carsten Grupstra

Feces from fish that are typically thought to promote healthy reefs can damage and, in some cases, kill corals, according to a recent study by Rice University marine biologists.

Until recently, fish that consume algae and detritus — grazers — were thought to keep reefs healthy, and fish that eat coral — corallivores — were thought to weaken reef structures. The researchers found high levels of coral pathogens in grazer feces and high levels of beneficial bacteria in corallivore feces, which they say could act like a “coral probiotic.”

“Corallivorous fish are generally regarded as harmful because they bite the corals,” said Carsten Grupstra, a former graduate student at Rice and lead author of the open-access study in Frontiers in Marine Science. “But it turns out that this doesn’t tell the whole story.”

Massive Caribbean sea urchin die-off caused by parasite

In a study led by Cornell microbiology professor Ian Hewson, scientists have discovered that a parasite is behind a severe die-off of long-spined sea urchins across the Caribbean Sea, which has had devastating consequences for coral reefs and surrounding marine ecosystems.

Video Credit: Noël Heaney/Cornell University 

Scientists have discovered that a parasite is behind a severe die-off of long-spined sea urchins across the Caribbean Sea, which has had devastating consequences for coral reefs and surrounding marine ecosystems.

The long-spined sea urchins (Diadema antillarum) serve as vital herbivores that graze on algae, which if left unchecked will outcompete corals for resources and space and blanket them, block light and kill them. By feeding on algae, the sea urchins are essential to maintaining coral health and balance in the marine ecosystem.

Diadema mortalities were first reported in St. Thomas in the U.S. Virgin Islands in late January 2022. By late March, the condition was found across the Lesser Antilles, Jamaica and the Mexican Caribbean. And by June of last year, it had been detected in most of the Greater Antilles, Florida and Curacao.

Prior to an experiment designed to verify the source of infections, a healthy sea urchin was swabbed to ensure it had never been exposed to the ciliate parasite.

Scientists have been trying to identify the cause of the mysterious illness, which has led to declines of between 85% and 95% compared to pre-mortality numbers in affected areas. When sea urchins die, they lose their spines and detach from their anchors.

Juvenile black rockfish affected by marine heat wave but not always for the worse, research shows

A juvenile black rockfish
Photo Credit: Will Fennie

Larvae produced by black rockfish, a linchpin of the West Coast commercial fishing industry for the past eight decades, fared better during two recent years of unusually high ocean temperatures than had been feared, new research by Oregon State University shows.

“The study is important for gauging the conditions and making management plans that will affect the species’ survival as the ocean experiences increasing variability because of climate change,” said Will Fennie, the study’s lead author.

Findings were published in Nature’s Scientific Reports.

Rockfish, a diverse genus with many species, are a group of ecologically as well as economically important fishes found from Baja California to British Columbia.

They are known for lifespans that can reach triple digits, an ability to produce prodigious numbers of offspring and variable survival during their early life stages, during which they are highly sensitive to environmental conditions.

Three newly discovered sea worms that glow in the dark

 Polycirrus onibi, a newly discovered marine worm that glows in the dark was named after a creature from Japanese folklore.
Photo Credit: Naoto Jimi / Nagoya University

A research group from Nagoya University in central Japan has discovered three new species of bioluminescent polycirrus worms from different parts of Japan. Usually found in shallow water, polycirrus are small worms, known for their bioluminescence. The researchers named one of their discoveries after a ghostly yokai, a creature in Japanese folklore; another after a lantern yokai; and the other after an influential Japanese marine biologist. They published their findings in the journal Royal Society Open Science. 

Scientists have studied only a small fraction of the more than 7,000 species of luminescent organisms in the world. Research remains limited to certain species because of the existence of specimens that are difficult to classify into species. Without correct identification of the species, comparisons of different results are of limited use.  

Naoto Jimi (he/him) and Special Assistant Professor Manabu Bessho-Uehara (he/him) at Nagoya University’s Graduate School of Science, led a research group with members from AIST, Olympus Corporation, and Japan Underwater Films Corporation, that organized Polycirrus according to their diversity. They discovered three new species, all of which emit blue-violet light.   

How whale shark rhodopsin evolved to see, in the deep blue sea!

Whale shark
Photo Credit: Mitsumasa Koyanagi, OMU

A new study reveals that the photoreceptor rhodopsin of whale sharks (Rhincodon typus), pictured here, evolved to improve sight for the low-light low-temperature deep-sea environment in a unique way.

A research group including Professors Mitsumasa Koyanagi and Akihisa Terakita of the Osaka Metropolitan University Graduate School of Science has investigated both the genetic information and structure of the photoreceptor rhodopsin, responsible for detecting dim light, of whale sharks to investigate how they can see in the dim light at extreme depths. The research group compared the whale sharks to zebra sharks, which are considered their closest relative, and brown-banded bamboo sharks, which are in the same group: the order orectolobiformes—commonly known as carpet sharks.

“This research used genetic information and molecular biological techniques to achieve stunning results—without harming whale sharks’ or their biology. Our research approach is to use these techniques to provide clues that reveal the mysteries of how these organisms live,” explained Professor Koyanagi. “The beautiful part is that it even works for species where information is limited, such as large or wild animals that are difficult to observe or follow in their natural habitat.”

With fewer salmon to eat, Southern Resident killer whales spend less time in the San Juan Islands

killer whales
Photo Credit: Michelle Klampe

As a key food supply declines, the endangered population of Southern Resident killer whales, known to frequent the Salish Sea off the coasts of Washington and British Columbia, is spending far less time in that region, a new study shows.

The Salish Sea around the San Juan Islands has traditionally been a hotspot for the whales. The Southern Residents would spend the summer months feeding on Chinook salmon, much of which belonged to the Fraser River stock that passes through the islands on its way to spawning grounds upriver.

But 17 years of whale sighting data shows that as the Fraser River Chinook salmon population dropped, the time spent by the Southern Residents around the San Juan Islands also declined ­– by more than 75%, said Joshua Stewart, an assistant professor with Oregon State University’s Marine Mammal Institute and the study’s lead author.

The findings were just published in the journal Marine Mammal Science. Co-authors of the paper are Jane Cogan, an independent researcher in Friday Harbor, Washington; John Durban, a professor with MMI who is also affiliated with the nonprofit SeaLife Response, Rehabilitation and Research (SR3); Holly Fearnback of SR3; David Ellifrit, Mark Malleson and Ken Balcomb of the nonprofit Center for Whale Research; and Melisa Pinnow of San Juan Orcas, a website dedicated to identification of individual orcas.

Recovery of endangered sunflower sea stars may play key role in restoring devastated submarine forests

Sunflower sea stars, such as the one that appears in the foreground, could help keep purple sea urchins in check, according to new research from Florida State University Assistant Professor Daniel Okamoto and colleagues published in Proceedings of the Royal Society B.
Photo Credit: Lynn Lee

Scientists working to understand the decimation of kelp forests on the Pacific Coast have found that the endangered sunflower sea star plays a vital role in maintaining the region’s ecological balance and that sea star recovery efforts could potentially help restore kelp forests as well.

The multi-institution team, which includes Florida State University Assistant Professor of Biological Science Daniel Okamoto, has published a new study showing that a healthy sea star population could keep purple sea urchins — which have contributed to the destruction of kelp forests — in check.

Their work is published in the Proceedings of the Royal Society B.

“Our work is focused on understanding what factors maintain healthy kelp forests as well as healthy urchin populations,” Okamoto said. “That is, what scenarios lead to collapse versus coexistence of these important species.”

New Study Provides First Comprehensive Look at Oxygen Loss on Coral Reefs

Coral reefs at a study site off Taiping Island, South China Sea.
Photo Credit: Yi Bei Liang

Scripps Oceanography scientists and collaborators provide first-of-its-kind assessment of hypoxia, or low oxygen levels, across 32 coral reef sites around the world

A new study is providing an unprecedented examination of oxygen loss on coral reefs around the globe under ocean warming. Led by researchers at UC San Diego’s Scripps Institution of Oceanography and a large team of national and international colleagues, the study captures the current state of hypoxia—or low oxygen levels—at 32 different sites, and reveals that hypoxia is already pervasive on many reefs.

The overall decline of oxygen content across the world’s oceans and coastal waters—a process known as ocean deoxygenation—has been well documented, but hypoxia on coral reefs has been relatively underexplored. Oxygen loss in the ocean is predicted to threaten marine ecosystems globally, though more research is needed to better understand the biological impacts on tropical corals and coral reefs.

The study, published March 16 in the journal Nature Climate Change, is the first to document oxygen conditions on coral reef ecosystems at this scale.

“Denoising” a Noisy Ocean

Study lead author Ella Kim (pink helmet) helps deploy a HARP instrument package.
Photo Credit: Ana Širović

Come mating season, fishes off the California coast sing songs of love in the evenings and before sunrise. They vocalize not so much as lone crooners but in choruses, in some cases loud enough to be heard from land. It’s a technique of romance shared by frogs, insects, whales, and other animals when the time is right.

For most of these vocal arrangements, the choruses are low-frequency. They’re hard to distinguish from the sounds of ships passing in the night among others.

Biologists, however, have long been interested in listening in on them in the name of understanding fish behavior toward an ultimate goal: They can help preserve fish populations and ocean health by identifying spawning seasons to inform fisheries management.

Now scientists at Scripps Institution of Oceanography at UC San Diego and colleagues have developed a way for computers to sift through sounds collected by field acoustic recording packages known as HARPs and process them faster than even the most trained human analysts. The method represents a major advance in the field of signal processing with uses beyond marine environments.

Stanford study reveals why the world's largest whales needed to be so big

Minke whales in Antarctica were studied by researchers using instrumented tags that can measure various aspects of their feeding activity.
Image Credit: Duke Marine Robotics and Remote Sensing.
This research was conducted under National Marine Fisheries Service permit #23095

Scientists studied a unique group of Antarctic minke whales and found that these gigantic mammals actually represent the smallest possible body size required for their style of feeding. The findings could inform which whale species are more vulnerable to future climate change impacts, like shifting food sources.

The largest animals to ever live owe their enormous size to feeding on the tiniest creatures in the sea, but their survival requires a minimum body size, Stanford-led research has found.

Published March 13 in Nature Ecology & Evolution, the study focuses on the “rorqual whales,” a lineage of filter feeders that includes the blue whale, the largest animal of all time. The group is characterized by a lunging maneuver where individuals engulf an enormous amount of water along with their prey, which they then strain through fringed structures at the roof of their mouth.

By examining the smallest living species in this group – the Antarctic minke whale – the authors found that individuals need to grow to at least 4.5 meters (approximately 15 feet, or weighing 1-2 tons), the length of weaned minke juveniles, in order to eat enough food to survive.

Does current shellfish culture gear curb ‘crunching’ rays?

Whitespotted eagle rays “crunching” on clams in a large outdoor tank with clams housed within a variety of anti-predator materials.

Video Credit: Florida Atlantic University / Harbor Branch Oceanographic Institute 

According to NOAA Fisheries, more than 80 percent of marine aquaculture production in the United States consists of bivalve mollusks such as oysters, clams and mussels. However, it’s not just humans who enjoy eating these shellfish, so do marine rays. They like to “crunch” on clams, which can sometimes take a big bite out of clammers’ profits.

Part of the process of culturing hard clams (Mercenaria mercenaria) involves deploying them in submerged bottom leases in the marine environment where clams can grow to market size. When deployed onto the clam lease, clammers incorporate a variety of anti-predator materials to protect their product, such as woven mesh netting and/or additional mesh, plastic or wire covers.

However, the effectiveness of these materials against highly mobile predators like rays has not been experimentally tested. Some rays, like the whitespotted eagle ray (Aetobatus narinari), are equipped with strong jaws, plate-like teeth and nimble pectoral fins, which make them formidable and highly maneuverable predators of clams.

Mysterious new behavior seen in whales may be recorded in ancient manuscripts

Flinders University Diagram of humpback engaged in trap feeding; with a jaw either flush with the waterline, or raised to a similar height to the rostrum.
Image Credit: John McCarthy 

In 2011, scientists recorded a previously unknown feeding strategy in whales around the world. Now, researchers in Australia think they may have found evidence of this behavior being described in ancient accounts of sea creatures, recorded more than 2,000 years ago.

They believe that misunderstandings of these descriptions contributed to myths about medieval sea monsters.

Whales are known to lunge at their prey when feeding, but recently whales have been spotted at the surface of the water with their jaws open at right angles, waiting for shoals of fish to swim into their mouths. 

This strategy seems to work for the whales because the fish think they have found a place to shelter from predators, not realizing they are swimming into danger.

It’s not known why this strategy has only recently been identified, but scientists speculate that it’s a result of changing environmental conditions - or that whales are being more closely monitored than ever before by drones and other modern technologies.

Blue whale foraging and reproduction are related to environmental conditions, study shows

A blue whale surfaces
Photo Credit: Three-shots

A new study of New Zealand blue whales’ vocalizations indicates the whales are present year-round in the South Taranaki Bight and their behavior is influenced by environmental conditions in the region.

The findings are a significant advancement in researchers’ understanding of the habitat use and behavior of this population of blue whales, which Oregon State University researchers first identified as genetically distinct from other blue whale populations less than a decade ago.  

“We went from not knowing 10 years ago whether this was a distinct population to now understanding these whales’ ecology and their response to changing environmental conditions,” said the study’s lead author, Dawn Barlow, a postdoctoral scholar in OSU’s Marine Mammal Institute. “These findings can inform conservation management of this blue whale population and their habitat.”

The patterns and intensity of the whales’ calls and songs over two years showed strong seasonality in their foraging and breeding behavior, and the vocalizations changed based on environmental conditions such as a documented marine heatwave, Barlow said.

“During the marine heatwave, feeding-related calls were reduced, reflecting poor foraging conditions during that period,” Barlow said. “But we also saw changes in vocalizations in the next breeding period, an indication that they put less effort into reproduction following a period of poor feeding conditions.”

Researchers find sea urchin die-offs threaten Caribbean coral reefs

The urchin species Diadema antillarum has long been considered the most important grazer in the Caribbean, feeding on algae that would otherwise overrun the reef and make it difficult for coral to thrive.
Photo Credit: Rachel Best

The sustained loss of a once abundant species of sea urchin in the Caribbean could also result in the functional extinction of diverse coral species from the region’s reefs, according to new research from a Florida State University team.

The urchin species Diadema antillarum has long been considered the most important grazer in the Caribbean, feeding on algae that would otherwise overrun the reef and make it difficult for coral to thrive. But two mortality events over the past 40 years have caused much of that urchin population to die off.

New research led by FSU Professor of Biological Science Don Levitan shows that the loss of these algae-free areas due to the sea urchin die-off is threatening the existence of the corals that populate Caribbean reefs.

Levitan, along with collaborator Peter Edmunds, a professor at California State University Northridge, has been collecting data on D. antillarum since his first research trip to St. John, U.S. Virgin Islands, in 1983, recording population density of the species and tracking it through mass mortality events in 1983-1984 and in 2022.

Trawlers intermix with whale ‘supergroup’ in Southern Ocean

Fin whales surround the research vessel National Geographic Endurance in January 2022.
Video Credit: Eric Wehrmeister

Trawlers working amidst a whale ‘supergroup’ raise red flag about human-whale conflicts in a changing ocean, Stanford study says

Scientists observed close to 1,000 fin whales foraging near Antarctica, while fishing vessels trawled for krill in their midst. Without action, such encounters are likely to become more common as this endangered species recovers and krill harvesting intensifies in the Southern Ocean.

Once driven nearly to extinction, the second-largest animals of all time have recently been spotted in big numbers in the Southern Ocean, competing directly with industrial trawlers for prey, according to research led by scientists from Stanford University and Lindblad Expeditions.

Published in Ecology, the study focuses on scientists’ sighting of an enormous “supergroup” of fin whales foraging for shrimplike animals called krill northwest of the South Orkney Islands in January 2022, with four commercial fishing vessels trawling among them for the same tiny creatures.

The researchers, led by Matthew Savoca of Stanford and Conor Ryan of Lindblad Expeditions, estimate at least 830 and possibly more than 1,100 fin whales were present. This ranks among the largest groups of baleen whales ever recorded since commercial whaling decimated their populations last century.