BAN DEEP SEA MINING

First study of its kind finds deep-sea mining waste threatens life and foodwebs in the ocean’s dim “twilight zone”

Particle plumes ejected by mining operations into deep Pacific waters threaten food source of more than half of the zooplankton types -- leading to bottom-up disruption of delicately balanced food system

University of Hawaii at Manoa

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image: 

Nodules on the abyssal seafloor in the Clarion Clipperton Zone with a mud cloud from a scientific remotely-operated vehicle (ROV) touching down. 

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Credit: UH/NOAA DeepCCZ Expedition

A new study led by researchers at the University of Hawai‘i (UH) at Mānoa published today in Nature Communications is the first of its kind to show that waste discharged from deep-sea mining operations in the Pacific’s biodiverse Clarion-Clipperton Zone (CCZ) could disrupt marine life in the midwater “twilight zone” — a vital region 200-1,500 meters below sea level that supports vast communities of zooplankton, tiny animals that serve as the ocean’s basic food building blocks. Specifically, it finds that 53% of all zooplankton and 60% of micronekton, which feed on zooplankton, would be impacted by the discharge, which could ultimately impact predators higher up on the food web.  

“When the waste released by mining activity enters the ocean, it creates water as murky as the mud-filled Mississippi River. The pervasive particles dilute the nutritious, natural food particles usually consumed by tiny, drifting Zooplankton,” said Michael Dowd, lead author of the study and Oceanography graduate student in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “Micronekton, small shrimp, fish and other animals that swim, feed on zooplankton. Some migrate between the depths and near surface waters and they are consumed by fish, seabirds and marine mammals. Zooplankton’s exposure to junk food sediment has the potential  to disrupt  the entire food web.” 

The study, Deep-sea mining discharge can disrupt midwater food webs, examines the content and effects of mining waste released during a 2022 mining trial in the midwater CCZ, an expansive area of the Pacific Ocean targeted for the extraction of deep-sea polymetallic nodules, which contain critical minerals, including cobalt, nickel and copper.  Researchers collected and tested water samples from depths where the mining waste was discharged, finding that these particles had far lower concentrations of amino acids — a key indicator of nutritional value — than the naturally-occurring particles that fuel life in these depths.   

“This isn’t just about mining the seafloor; it’s about reducing the food for entire communities in the deep sea,” said Erica Goetze, co-author, SOEST oceanography professor, and expert in marine zooplankton ecology. “We found that many animals at the depth of discharge depend on naturally occurring small detrital particles — the very food that mining plume particles replace.”

The study comes as some countries ramp up their efforts to meet growing global demand for metals needed for electric car batteries and other low-carbon technologies.  Currently, about 1.5 million square kilometers of the CCZ are under license for deep-sea mining.

Disrupting a system tuned to scarcity

During the deep-sea mining process, nodules are collected from the seafloor, along with seawater and sediments, and transferred through a pipe to a collection ship for separation of nodules from sediment waste. This seawater-containing sediment waste, as well as pulverized very small nodule particles, must be returned to the ocean. Although the release depth for this waste is currently unclear, some mining operators have proposed midwater mining discharge within the twilight zone. Until now, the impacts of this waste on midwater communities was poorly understood. These impacts will be critical for the establishment of regulations around waste discharge, which don’t yet exist--a gap in governance over the industry. 

The twilight zone hosts a staggering diversity of life, including tiny krill, fish, squid, octopus and gelatinous species such as jellyfish and siphonophores. By rising towards the ocean’s surface every night, then swimming back down again, these creatures support the transport of carbon to greater depths in the ocean, which is critical to ocean and human health. These creatures either feed on the particles in the twilight zone or prey on those that do, creating a tightly linked food web that connects the surface ocean to the abyss.

“Our research suggests that mining plumes don’t just create cloudy water — they change the quality of what’s available to eat, especially for animals that can’t easily swim away,” explained Jeffrey Drazen, co-author, SOEST oceanography professor, and deep-sea ecologist. “It’s like dumping empty calories into a system that’s been running on a finely tuned diet for hundreds of years.”

Urgent concerns with commercial mining

The findings raise urgent concerns about long-lasting, system-wide effects if large-scale commercial mining proceeds without strong environmental safeguards. Pacific tuna fisheries, for example, operate in the CCZ, which means that deep sea mining waste could impact fish that land on dinnerplates globally. 

“Deep-sea mining has not yet begun at a commercial scale, so this is our chance to make informed decisions,” said Brian Popp, co-author, SOEST earth sciences professor, and expert in marine stable isotope biogeochemistry. “If we don’t understand what’s at stake in the midwater, we risk harming ecosystems we’re only just beginning to study.” 

The authors hope their findings will inform international regulatory decisions currently being shaped by the International Seabed Authority, as well as the National Oceanic and Atmospheric Administration, which is responsible for reviewing environmental impacts of U.S.-led deep-sea mining initiatives. They also call for expanded research to protect the full vertical extent of ocean ecosystems.

"Before commercial deep-sea mining begins, it is essential to carefully consider the depth at which mining waste is discharged," added Drazen. "The fate of these mining waste plumes and their impact on ocean ecosystems varies with depth, and improper discharge could cause harm to communities from the surface to the seafloor."

Additional authors on the study include oceanography graduate students Victoria Assad and Alexus Cazares-Nuesser, and oceanography professor Angelicque White. 

Illustration on midwater impacts

Credit

Drazen et al., 2020 (Proceedings of the National Academy of Sciences), Amanda Merritt (graphic artist).

Zooplankton from the eastern Clarion Clipperton Zone.

Credit

© Goetze, Ellis, Cazares.

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Journal

Nature Communications

DOI

10.1038/s41467-025-65411-w 

Method of Research

Observational study

Subject of Research

Animals

Article Title

Deep-sea mining discharge can disrupt midwater food webs

Article Publication Date

6-Nov-2025

 

Sounds modify visual perception: A study reveals new links between hearing and vision in the rodent brain

A new study reveals the existence, in rats, of direct cross-modal interactions between distinct sensory modalities, capable of modulating perceptual processing. Specifically, auditory signals were found to compress the visual perceptual space 

Scuola Internazionale Superiore di Studi Avanzati

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Sounds can alter the way the brain interprets what it sees. This is the key finding of a new study by SISSA researchers in Trieste, published in PLOS Computational Biology. The research shows that, when sounds are paired with moving visual stimuli, the latter are perceived differently by rats. In particular, auditory cues systematically alter vision by compressing the animals’ “perceptual space”. Derived from the integration of behavioural experiments and computational modelling, the researchers’ findings indicate that auditory signals exert an inhibitory influence on visual perception. The study thus provides a new perspective on how the senses communicate within the brain, revealing that even direct connections between primary sensory areas — not only integration within higher-order association cortices — can profoundly influence perceptual experience.

How the Senses Communicate in the Brain

In the brain, information from the different senses is first processed within specialised regions devoted to each modality (known as unimodal areas). From these regions, sensory inputs then converge onto specialised areas, known as association cortices, where they are integrated to construct a coherent, multimodal representation of the environment. Such processing is highly sophisticated and occurs within cortical regions endowed with complex cognitive capabilities. “However, inputs from one sensory modality — such as sound — may directly affect the processing of another, such as vision, through connections linking unimodal cortical areas,” explains Davide Zoccolan, who coordinated the experimental component of the study. "This phenomenon appears to be less prominent in non-human primates and in humans, yet is believed to be more pronounced in rodents. Nevertheless, previous investigations have yielded inconsistent findings: while some reported an enhancement of visual neuronal responses in the presence of sounds, others identified a suppressive effect. With our work, we sought to clarify precisely this issue at the perceptual level.”

Experiments to Understand How sounds Influence Vision

The researchers at SISSA combined behavioural experiments with computational modelling. A group of rats was trained to classify visual stimuli according to their temporal frequency, while being simultaneously exposed to sounds that were entirely irrelevant to the task. The temporal frequency of these sounds, however, could either match that of the visual stimuli or not. Zoccolan explains: “One might expect that visual cortex spontaneously integrates sounds (although task irrelevant), and that auditory stimuli that are congruent with the visual ones would enhance visual perception, while incongruent sounds would impair it. But this is not the case.”

When Sound Inhibits Vision

The approach adopted by the Trieste research team made it possible to rule out high-level multisensory integration, thus assessing the direct influence of auditory signals on visual perception. As Eugenio Piasini, who coordinated the computational component of the study, explains, “the results show that rat visual classification performance was systematically altered by the presence of sounds, in a manner proportional to their intensity but independent of their temporal modulation. Specifically, pairing sounds with moving visual stimuli led to a compression of the visual perceptual space. The overall effect of auditory stimuli on visual ones was therefore inhibitory.” In summary, in the presence of intense sounds, the temporal frequency of visual stimuli was substantially underestimated by the rats.

Experimental Data Confirmed by Computational Modelling

To understand the mechanisms underlying this phenomenon, the researchers developed a Bayesian model combined with a neural coding scheme in which visual neurons were inhibited by concurrent sounds in proportion to their intensity. As Eugenio Piasini explains, “the model reproduced the experimental data with remarkable accuracy, supporting the hypothesis that auditory inputs can selectively inhibit the activity of visual neurons and thereby modify perception.”

A New Perspective on the Multisensory Brain

“Our study – concludes Zoccolan – provides a new perspective on how the senses communicate within the brain, showing that even direct connections between primary sensory areas — not only multimodal integration within higher-order association cortices — can profoundly influence perceptual experience. Once the inhibitory effect of sounds on vision has been established, it will certainly be interesting to determine whether the reverse also holds true. As for the evolutionary and ecological processes underlying this mechanism, we can only speculate. This inhibitory interaction between auditory and visual processing may reflect inter-areal competition mechanisms through which the brain enhances the salience of one modality while suppressing another – for instance, by prioritising auditory perception, which can more rapidly alert the organism to the presence of potential predators. Undoubtedly, these animals live in a multisensory world that is far more complex and integrated than we could imagine.”

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Journal

PLOS Computational Biology

DOI

10.1371/journal.pcbi.1013608 

Subject of Research

Animals

Article Title

Seeing what you hear: Compression of rat visual perceptual space by task-irrelevant sounds

 

Pioneering therapy could offer hope for psychosis patients struggling with disturbing mental images

University of Sheffield

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• A new therapy developed by University of Sheffield researchers shows promise in treating the distressing and intrusive mental images experienced by up to 74 per cent of UK people living with psychosis and schizophrenia 

• The ‘iMAPS’ therapy directly helps patients understand, make sense of, and change these 'mind's eye' images, replacing them with more positive ones

• The largest feasibility clinical trial to date of imagery-focused therapy for people with psychosis demonstrated its safety and has led to calls for a full clinical trial to assess its broader clinical and cost effectiveness as a vital addition  to existing psychosis treatments

• A participant in the study, who has visions of sinister featureless figures and paranoia, explains how iMAPS helped him to understand and change the narrative of the images he experiences and now works supporting others with mental health problems

A pioneering therapy targeting distressing and disturbing mental images for people with psychosis could lead to a transformative intervention for a condition estimated to cost England almost £12 billion a year.

As many as 74 per cent of people with psychosis, a condition which causes people to hear voices, unfounded fears others mean them harm, also see intrusive images in their mind’s eye. These images can be the result of trauma, anxiety, fear of anticipated future events and many other factors. A recent survey of over 10,000 UK adults found that imagery was the third most strongly linked factor with mistrust and paranoia. These vivid images can often be multi-sensory and associated with distressing voices, as well as unfounded belief that others mean them harm.

Existing psychological therapies, such as Cognitive Behavioural Therapy (CBT), have demonstrated a robust but small effect in the treatment of psychotic experiences, such as hallucinations and delusions. Similarly, while antipsychotic medication can alleviate some psychosis symptoms, around 74 per cent of patients discontinue or switch medications within 18 months. This is largely due to debilitating side effects or a lack of reported benefit, highlighting a critical need for more effective therapies.

The University of Sheffield research team believes imagery-focused therapy could be a valuable intervention to complement existing treatments.

iMAPS therapy aims to directly address such ‘mind's eye’ imagery by helping the patient to understand, make sense of and change the images, replacing them with more positive ones. It also targets negative beliefs about self and others (schemas) using imagery techniques. The National Institute for Health and Care Research (NIHR)-funded trial recruited 45 patients with psychosis who were seeking help with hallucinations and delusions, and had reported distressing and intrusive mental imagery linked to their symptoms.

The largest feasibility trial to date of imagery-focused therapy for people with psychosis with 45 patients, detailed in a University of Sheffield study published recently in the Schizophrenia Bulletin journal, demonstrated iMAPS safety and yielded promising results, leading to hopes for a multi-centre clinical trial to test the treatment’s clinical and cost-effectiveness.

Dr Christopher Taylor, a Senior Lecturer and NIHR Fellow in the University of Sheffield’s School of Psychology and Consultant Clinical Psychologist, Pennine Care NHS Foundation Trust, said: "Imagine someone experiencing psychosis, who has the terrifying belief that their home will be invaded and they will be attacked. They might then vividly picture an intruder breaking in, triggering intense fear and worsening their distress.

 “This intrusive image can amplify their suspicion and paranoia, making them feel even more vulnerable. Our goal is to help them understand and eventually gain control over these powerful images. When you try to suppress distressing mental images, they often return more intensely - like a New Year's resolution to avoid chocolate biscuits leading to stronger cravings. 

“In therapy, we address this by helping individuals understand these shared experiences. We gently introduce imagery work with 'safe place' exercises to foster feelings of safety, then practice altering the image's size, shape and texture to build a sense of control. We also use imagery rescripting, a technique borrowed from trauma therapy, where we guide individuals to imagine a new, positive ending to a past negative event, engaging all of their senses. While we can't change the past, we can empower individuals to re-script their experiences and change the meaning.”

In the trial, the talking therapy was administered over 12 weekly sessions, each patient had at least one distressing image linked with an hallucination or delusion. These might also include purely imagined images alongside those from a person's past or their future worries.

Thom Brandwood-Spencer, 28, a participant in the first iMAPS study, first began experiencing distressing symptoms when he was around nine-years-old. 

“It initially manifested as a general fear, where I’d be walking home from school and jumping from lamp post to lamp post to avoid this abstract fear. When I was 12 or 13 I started hearing unsettling voices and a year or so later I began seeing things, which developed into sinister, featureless figures making strange noises.

“It was very distressing and difficult to understand. I’d often feel like I was in danger, as if the images and sounds were portents of things to come.”

Thom was later referred to local mental health services and was ultimately diagnosed with paranoid schizophrenia with episodes of psychosis.Through support, his condition became easier to manage and he went on to study computer science at university - but his visions continued to fill him with dread and paranoia and eventually forced him to drop out.

It was at that point, while under the care of a first episode psychosis team, Thom became involved with iMAPS, and over eight weekly sessions his therapist helped him to understand and change the narrative of the images he experiences.

“At that point the condition was completely disrupting my life, and the prescribed medication I was taking wasn’t working,” he said.

“One of the most difficult aspects was the powerlessness - and the idea that what was happening to me was permanent and inescapable. iMAPS helped me to address this, by changing this narrative of powerlessness and understanding that my life and my experiences are not pre-ordained. Therapy enabled me to shift my concentration away from what I was seeing in my mind and separate the images from those menacing feelings of threat.

"I came to see that the threat wasn't from the figures, but from my own feelings, and grasping that made a significant difference. We also used a technique to imagine putting the featureless figures in a suit of armour or a diving suit, and it helped me feel like they couldn’t get me anymore.”

Thom went on to successfully complete an undergraduate degree in Psychology and then continued on to pursue a Master's in the same field. He now works in a role supporting others with mental health problems, and even discussed his experiences with iMAPS at an international conference.

“As well as the benefits of the iMAPS therapy itself, I’ve been able to act as a consultant on the latest study and an advocate to help others going through similar experiences. I’m now able to give people what I needed when it all began.

“One of the most important messages I’d like to get across to others is that whatever you are going through, it doesn't have to be forever. It can change, and there is hope.”

Dr Taylor from the University of Sheffield added: “We're greatly encouraged by feedback from patients like Thom, who serves as an excellent advocate not only for iMAPS but also for recovery and supporting others with similar experiences. 

“A full clinical trial is the necessary next step to assess iMAPS's broader clinical and cost effectiveness, paving the way for it to potentially complement the offer of existing NICE recommended psychosis treatments.”

Read the study in full here.

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DOI

10.1093/schbul/sbaf060