BAN DEEP SEA MINING
Rare glimpse at understudied ecosystem prompts caution on deep-sea mining
University of Hawaii at Manoa
image:
Some of the animals identified in the deep-sea that spend their life in the benthic boundary layer.
view moreCredit: Gabrielle Ellis
An enormous but poorly understood region of the global ocean—referred to as the abyssal benthic boundary layer—lies just a few meters above the seafloor and has only been sampled a handful of times. A groundbreaking study by oceanographers at the University of Hawaiʻi (UH) at Mānoa has provided the first in-depth look at this vast, understudied deep-ocean habitat, revealing a dynamic community that may be far more sensitive to seasonal changes than previously understood. The research, published in the journal Limnology and Oceanography, also concluded that deep-sea mining could have significant and unavoidable impacts on biodiversity, regardless of the time of year.
“Given the remoteness of this environment, we have extraordinarily limited knowledge of the animals that inhabit this zone,” said Gabrielle Ellis, lead author of the study and recent Oceanography graduate from the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “This study represents a significant contribution to our understanding of the benthic boundary layer community, and it starts to unravel temporal dynamics in the abyss.”
Sampling to assess seasonality
This community of organisms, like much of the deep-sea ecosystem, is reliant on organic material that falls from the surface ocean down to great depths. Using seawater pumps attached to an autonomous lander, the research team collected tiny animals from about 10 feet above the seafloor during both spring and fall. Through both genetic and visual analysis, they discovered that the community of zooplankton, such as snails, bivalves and barnacles, changes dramatically between seasons, responding to varying levels of food sinking from the surface ocean.
“We didn’t expect the results to be as stark as they were!” said Ellis. “These animals may be quite sensitive to changes in productivity in surface waters, which ultimately drive these patterns in the abyss.”
The benthic boundary layer is a crucial, interconnected part of the deep-sea ecosystem, serving as a home for unique animals and a vital pathway for the larvae of many species before they settle on the seafloor. The team’s observations highlight the complex behavior of animals across their life cycles, and the connectedness of the deep ocean more broadly.
Vulnerability to deep-sea mining impacts
“In the event of deep-sea mining, the organisms in this region will be impacted via ambient water removal and the generation of sediment plumes that interfere with feeding, in addition to the removal of nodules, which will effectively remove the settling habitat for larvae, likely leading to further declines in local recruitment,” said Erica Goetze, study co-author and oceanography professor. Goetze and Craig R. Smith, co-author and professor emeritus of oceanography, co-advised Ellis for her doctoral degree.
“These effects will not be isolated to nodule fields where the mining is occurring, but will also impact a variety of deep-sea habitats through the removal of their dispersing larvae that connect populations of wide-ranging abyssal species,” added Jeffrey Drazen, study co-author and oceanography professor. “Based on our findings, it appears that mining during any particular time period is likely to result in impacts to these organisms.”
Future research aims to conduct repeat sampling over several years to better understand what constitutes normal variability in this ecosystem.
“Our results highlight how much we have to learn about the dynamics of these abyssal ecosystems in order to provide a vital baseline for assessing the impact of both human activity and climate change,” concluded Smith.
Larvae collected from the benthic boundary layer. These animals later settle to the seafloor.
Credit
Gabrielle Ellis
The autonomous lander used in this study is retrieved by a shipboard crane. The pumps are attached on either side of the lander. A flag used to spot the lander from the ship is found in the lower left corner.
Credit
Gabrielle Ellis
Journal
Limnology and Oceanography
Method of Research
Observational study
Subject of Research
Animals
Article Title
Zooplankton community structure in the abyssal benthic boundary layer varies over time due to nonuniform species response to seasonal organic-matter fluxes
Unique videos show how trawling restrictions brings back life to the sea
University of Gothenburg
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The AI model was trained to recognise 17 different species that live on the sea slope in the Koster Sea. This is what it looks like when the species are identified.
view moreCredit: University of Gothenburg
Trawling restrictions not only benefits fish and shellfish; anemones and corals are also becoming more common, according to a new study from the University of Gothenburg. Twenty-six years of underwater videos from the depths of the Koster Sea also show long-term changes in the ecosystem as the water becomes warmer.
The marine wildlife in Kosterhavet National Park has changed rapidly in recent years. The introduction of trawling restrictions in the area for the national park during the last 25 years, brought about a change in the living conditions for the animals that live on the seabed.
“Animals that capture nutrients through filtration, such as mussels, anemones and soft corals, do not thrive when bottom trawls stir up sediment from the seabed. Several of these species have recovered significantly,” says Matthias Obst, researcher on marine ecosystems at the University of Gothenburg and research leader in the project.
Loss at shallow depths
At the same time, the study shows that large and heat-sensitive species are declining at shallow depths in the Koster Fjord or are disappearing completely from the area. The most dramatic decline has been in the football sponge Geodia barretti, while the excavated fileclam Acesta excavata also declined steadily. Both animals are important components of the Koster Sea ecosystems as they build habitats for many other organisms.
The study was made possible thanks to a large treasure of underwater videos taken at a rock wall in Koster Sea. The wall has been filmed with an underwater robot during various study visits, teaching sessions and projects at the Tjärnö Marine Laboratory from 1997 onwards.
Machine learning
“The videos were stored on a number of thick hard drives that were kept on a shelf. We are lucky that the underwater photographers at the Tjärnö Marine Laboratory chose to keep this data until now, when we can use machines to go through it,” says Matthias Obst.
Without machine learning, it would have been impossible to analyse such a large number of underwater videos with varying quality and count the abundance of 17 different species over 26 years, 1997–2023. Master's student Christian Nilsson reviewed selected parts of the material and taught an AI object detection model to recognise characteristic features of each species.
Good timeline
In the end, the AI model had become so good that the results could be trusted. It took the model only a few hours to analyse 4.4 million images from the selected videos. The National Academic Infrastructure for Supercomputers in Sweden, NAISS, was used for this purpose.
“We now have a good timeline showing how the 17 species have increased and decreased over the 26 years covered by the data, but also how they have responded to increasingly warmer water temperatures. We see that heat-sensitive species are losing their living environment in shallow waters due to the warm temperatures there,” says Matthias Obst.
Driven by climate change
The study is part of the EU-funded program Digital Twin of the Ocean (DTO), which combines marine research with modern technology development for the sustainable management of our marine ecosystems. It shows that the protective measures implemented in the Kosterhavet National Park have been effective and are helping to bring balance to the ecosystem.
“But there are some organisms that may not be saved by the protective measures in the national park. Rising temperatures in the Koster Sea are driven by climate change, which is difficult to stop. For these species, it may be appropriate to find new areas with deeper water where these species can find refuge,” says Matthias Obst.
The distribution of the excavated fileclam has declined as the water in the Koster Sea has become warmer.
Credit
Tomas Lundälv
AI-model species identification from video [VIDEO]
The AI model was trained to recognise 17 different species that live on the sea slope in the Koster Sea. This is what it looks like when the species are identified.
Journal
Ecology and Evolution
Method of Research
Imaging analysis
Subject of Research
Not applicable
Article Title
Applying Deep Learning to Quantify Drivers of Long-Term Ecological Change in a Swedish Marine Protected Area
