Biorock increases shellfish settlement while reducing hydroid fouling in Chile, Centro de Investigacion en Ecosistemas de la Patagonia, (in Spanish).

English machine translation:



Project called Bio-roca, led by the Patagonia Ecosystem Research Center, evaluated its potential to promote the restoration and bio-diversity of the marine ecosystem in the Puyuhuapi Fjord, through the development of a technology based on low electric fields. voltage.

The complex world that lives under water is key to climate change mitigation, where acidification, warming, deoxygenation (loss of oxygen) and pollution produced by humans are leaving their mark on relevant issues such as sequestration. carbon. The global scientific community has been working to find solutions to protect and restore coastal areas and thus promote the reduction of the impacts of greenhouse gases.

Over the last 35 years, a scientific team led by Dr. Thomas Goreau has developed technology called “Biorock” or Bio-rock (in Spanish), which uses small currents or low-voltage electric fields to stimulate better growth, survival and resilience of marine organisms, especially corals that are severely threatened by warming oceans. Through electrolysis in seawater, the Bio-rock acts as an artificial reef that has the potential to concentrate minerals such as calcite, which are required for the formation of the shells of certain marine organisms such as bivalves, thus generating , a high-energy environment that stimulates greater settlement of marine species, and in turn, works as a carbon sequestration mechanism. Goreau, who has been developing this technology for years, highlights its applicability, “we have been working on Biorock technology for 45 years, in more than 700 projects and 45 countries, mainly in coral reef restoration. A question in this project is whether we can grow organisms faster for the development of aquaculture, since Chile is a country with a great activity in this industry, which is very important.”

Dr. Bárbara Jacob from the Patagonian Ecosystem Research Center (CIEP) contacted Thomas Goreau’s research team and proposed experimenting with this technology to study its potential to restore natural banks of Mitylus chilensis , known as choritos or mussels. This resource is currently not only cultivated and exported extensively from southern Chile, but is also used as bait for the artisanal crustacean fishery in the Aysén Region. Human activities, such as fishing, degrade ecosystems in many regions of the world, which has been documented through the decrease in diversity status variables, the increase in the number of endangered species or the decrease in abundance of key groups of organisms. In this sense, it becomes relevant to articulate new approaches aimed at the conservation, restoration and better management of resources impacted by anthropic action (eg extractive fishing, aquaculture) through scientific-technological initiatives. With the aim of carrying out a first pilot of this technology in Chile, a multidisciplinary research group was formed by Dr. Bárbara Jacob, the MSc fisheries resources researcher. Gustavo Aedo and Dr. Paula Ortiz from the CIEP Center, together with the international collaboration of Dr. Thomas Goreau, who leads the NGO Global Coral Reef Alliance and Dr. Alejando Rodríguez from the University of Granada and researchers from national institutions; such as Dr. Laura Ramajo from CR 2  and researchers such as Dr. Marcelo Fuentes from the INCAR center and Dr. Eduardo Hernández from the U. Católica de la Santísima de Concepción. In addition, this project had the participation of the company Salmones Multi-export, who through a collaboration agreement contributed with important logistical support that made possible the development of a field experiment in the Puyuhuapi Fjord.

Investigation Development

The researchers set four objectives to develop, among which were; evaluate the physiological response of Mytilus chilensis , comparing its growth rate and shell formation under two different conditions: subjected to an electric field, and without an electric field. The second objective was to evaluate the level of mineral accretion, (deposition of minerals such as calcite), through the process of electrolysis in seawater, on metal plates electrified by means of an electric field. The third objective was to evaluate the spontaneous settlement of marine species, both on plates electrified with different intensities of amperage and voltage, as well as on plates without electricity. Finally, the fourth objective was to characterize the spontaneous settlement in the entire “reef-type” structure that was subjected to a very low voltage electric field.

A great task for the development of this project, which has been financed by an internal fund of the PATSER program (ANID financing – Regional Centers Strengthening Program), was to develop from scratch the construction of the structures that were placed 6 meters from depth (floating in water column from platforms). Then, maintain them for a period of 9 months, between March and December 2023. For the experiment, metal plates called cathodes and a central piece that contained the anode were also built, which allowed electric fields to be generated inside and outside the artificial reef. . Each metal plate or cathode was subjected to different electrical intensities, which would allow evaluating its effects on the spontaneous settlement of the species that inhabit that depth stratum. To evaluate the development of the main study species (Mytilus chilensis ) under conditions with and without electricity, hanging baskets (made of anchovy mesh) were built and individually marked mussels were placed inside, with the objective of evaluating their growth in Different times.

First results

One of the first visible results was that the hanging baskets of the reef without electricity presented a large coverage of a species of hydrozoan, which is a type of aquatic animal of the class cnidaria,  while the reef subjected to electricity did not show the presence of these organisms. These results suggest that electric fields inhibited their settlement and growth, which has already been documented in the past by studies dating back to 1930. Fouling by hydrozoans is very common in ecosystems impacted by aquaculture in many places around the world and along with other species, constitute a problem of maintaining floating networks and structures that requires high investments of money, especially during warm seasons when the growth of hydrozoans tends to increase.

Regarding the spontaneous settlement of the species M. chilensis , they presented a greater coverage on the plates subjected to electricity compared to the reef plates without electricity, while it was the plates subjected to intermediate current intensities that presented a greater coverage of choritos These results suggest that higher intensities of electrical current could inhibit the growth of mussels. Regarding the mineral accretion process by electrolysis, the electrified metal plates presented layers of whitish minerals, similar to the color of calcium carbonate, which gradually displaced the initial oxide that the plates had on the reef. The increase in the concentration and thickness of minerals in the plates, depending on their composition, has been proposed as a mechanism that promotes an alkaline (i.e., less acidic) microenvironment that would benefit the growth of many marine organisms.

Dr. Bárbara Jacob explains these first observed results. “The process of mineral accretion that occurs by electrolysis in seawater, is a process that restores itself while being charged by electrical currents, enhances the growth of qualifying species (that is, that use calcite to build their shells), and at the same time it functions as a carbon sink (or sequestration) mechanism, since it resembles the construction process of natural reefs of habitat-building species such as corals. It was precisely the plates subjected to a greater intensity of amperage and voltage that concentrated the greatest amount of minerals. However, as has been shown in other studies, the type of material that is deposited is dependent on the intensity of the current, the size of the crystal, its mineralogy, the deposition speed and the parameters of the electric current. Currently, we are preparing to send these minerals to the Department of Mineralogy and Petrology of the Scientific Instrumentation Center (CIC) of the University of Granada, who are collaborating with the project to determine the type of mineral and its structure.”

Biodiversity Attraction

Regarding the spontaneous settlement of species on the reefs, the differences were striking, where the Bio-rock proved to be an attractor of a greater diversity of marine species in relation to the reef without electricity. The greatest diversity of species found was characterized by a high abundance of an anemone of the species Metridium senile , some arthropods such as small decapod crustaceans, cirripeds and amphipods, bivalve species such as the southern oyster  (Austrochlamys natans) , the cholga (Aulacomya atra ) and the mussel ( Mytilus chilensis) , Nemertines (worms) and a high abundance of Ascidians (species to be determined).

The project director comments that this pilot project has been an enriching research experience, “my first astonishment is related to the difference in the development of hydrozoans between the bio-rock reef and the reef without electrodes, as well as the notable increase in the diversity of organisms throughout the reef, which suggests that the electric field, both inside and around the reef, stimulated greater settlement of larvae of different marine species. “The identification and classification of the observed species is still in development, so we do not know how many other species we will find within the arrays of organisms that are not easy to identify at first glance.”

Horizons of technology development

If we think about this technology on a larger scale, it could be used to mitigate impacts of human activities. For example, one could think that the development of these electrically charged reefs could be used to stimulate greater settlement and better growth of some species of bivalves of economic importance, such as mussels, cholga and oysters , which is relevant for the development and diversification of aquaculture. On the other hand, the prolific growth of the Mytilus chilensis resource  observed in the reef without electricity is relevant, due to the important role that filter-feeding organisms have in marine ecosystems, and this is because they filter large volumes of water when they feed, and In this process they clean the waters of excess organic matter from pollution. Additionally, the growth of M. chilensis,  in vertical hangings or in floating reef-type structures, demonstrates that they can become construction sites for “marine animal forests”, and in the long term promote great marine diversity, either because it offers greater availability as food for other species, or because it provides protection to some more vulnerable species. Dr. Thomas Goreau highlights, “what we are also trying to do in this project is to enhance the development of filter-feeding organisms, that is, to increase the organisms that can clean the water and thus obtain a healthier marine ecosystem. “We are just experiencing the optimal growth conditions for each species, but we believe that this can be a way to reduce the consequences of aquaculture activities such as salmon farming.”

On the other hand, the decrease in the growth of a hydrozoan species in the electrified reef has the potential to be used in salmon aquaculture to manage marine fouling (formation of unwanted organic and inorganic deposits) in its culture networks, which which could reduce the high costs of network maintenance, the proliferation of diseases and marine pollution due to the use of toxic chemicals. However, more research is required to determine the correct ranges of electrical treatment to control fouling in crop networks of a broader spectrum of species.

The greater marine biodiversity found in the Bio-rock reef suggests that the application of small electrical currents stimulates a high settlement of marine species and therefore promotes more diverse ecosystems as has been demonstrated for coral ecosystems by the research of scientist Thomas Goreau and other researchers around the world. In the Aysén region, both aquaculture and climate change are growing threats to the sustainability of the ecosystem services that the fjords provide to society, which are, in turn, highly dependent on marine biodiversity. Technological-scientific initiatives such as electrostimulation could be developed in coastal communities, such as the management areas of artisanal fishermen for the preservation and restoration of marine biodiversity and the sustainability of the resources that support their communities.

Finally, these reefs could also have a local role in carbon capture since the accretion of minerals such as calcium carbonate is a mechanism that allows carbon to be retained inside the ocean for long periods of time. “This pilot project inspires us to ask new questions and manage new future projects that include renewable energies and are aimed at the conservation, restoration and better management of resources impacted by anthropogenic action, such as extractive fishing and aquaculture, through solutions based on nature as a way to adapt and mitigate climate change.