Scalable Strategies to Enhance Sustainable Red Seaweed Aquaculture in Land-Based Cultivation Systems

SCALABLE STRATEGIES TO ENHANCE SUSTAINABLE RED SEAWEED AQUACULTURE IN LAND-BASED CULTIVATION SYSTEMS

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

ACTIVE

Funding Source

OTHER GRANTS

Reporting Frequency

Annual

Accession No.

1030654

Grant No.

2023-70007-40202

Cumulative Award Amt.

$300,000.00

Proposal No.

2022-06037

Multistate No.

(N/A)

Project Start Date

Jul 1, 2023

Project End Date

Jun 30, 2026

Grant Year

2023

Program Code

[AQUA]- Aquaculture Research

Recipient Organization
OREGON STATE UNIVERSITY
(N/A)
CORVALLIS,OR 97331

Performing Department
(N/A)

Non Technical Summary
Current Issue and Opportunity. Seaweeds are large, plant-like algae that grow in the ocean. Nearly 30% of global annual aquaculture production on a mass basis comes from seaweed, mainly from brown and red seaweeds. In 2019, over 35 million wet tons of seaweed were produced globally through aquaculture, mainly by Asian countries including China, Indonesia, Japan, and Korea. Unfortunately, the U.S. contributed less than 0.1% of this total. Gracilaria, a red seaweed, merits consideration as a priority emerging candidate for aquaculture development in the United States. Gracilaria species are rich in proteins, carbohydrates, and a diverse array of bioactive compounds including antioxidants. They are a quality source of food, food ingredients, and value-added products such phycocolloids used as thickeners in a variety of consumer products. G. pacifica is used as aquaculture feed for abalone, and Gracilaria species can also be integrated into multi-trophic aquaculture (IMTA) systems that contribute to restorative aquaculture practices.A critical barrier to red seaweed aquaculture development in the US is that the practices used in Asian countries to achieve scale and low cost cannot be duplicated in US coastal regions. For example, Gracilaria species in Asia are cultivated through manually-intensive inoculation and cultivation, and harvesting practices in the nearshore marine environment, such as planting in shallow ponds where seaweed plantlets are manually tied to rope lines. Although these operations have low productivity, they are economically feasible in many countries because labor costs are relatively low, environmental standards are relaxed, and the nearshore environment is made available for mass cultivation However, in the US marine coastal waters, more environmental regulation and natural resource policy factors come into play, and a low-cost manual labor pool is not readily available. Therefore, to work around these issues, this project will focus on land-based cultivation of red seaweeds, using engineered approaches that automate and intensify the productivity of the grow-out process.Methods and Approaches. The proposed research will support the development of sustainable aquaculture systems for intensified production of commercially-significant red seaweed in land-based cultivation systems. As described above, Gracilaria species are a source food as well as plant-based proteins and industrial phyco-colloids, which together constitute nearly 90% of biomass dry organic weight. The biomass is produced using non-potable seawater, carbon dioxide from air or waste combustion gases, and sunlight. This proposed project will address the USDA Aquaculture Program Area Priority relevant to the design of environmentally and economically sustainable commercial aquaculture production systems, focusing on the commercially-significant red seaweed Gracilaria as model system.The proposed research will focus on the combination of biological and engineering approaches to automate and intensify the grow out processes in land-based recirculating tanks, resulting in increased productivity and labor-saving production technologies designed to reduce risk for advancing the nascent red seaweed aquaculture enterprise in the United States. As part of this effort, robust cultivars for Gracilaria species of emerging commercial significance, G. pacifica and G. parvispora will be established, and scalable processes to grow these Gracilaria strains on modular mesh panels will be developed. These Gracilaria panels will be tested relevant industrial environments in collaboration with our private partner Oregon Seaweed to assess productivity and product quality. Based on the test results, economic analyses will be performed to estimate costs and target technical improvements for further cost reduction.The project includes extension and outreach efforts to support and promote the nascent red seaweed aquaculture enterprise in the Pacific Northwest region, including the initiation of a Red Seaweed Aquaculture Learning Group and a delivery of a workshop focused on land-based aquaculture of red seaweeds.Ultimate Goal. The ultimate goal of this project is to establish land-based cultivation of commercially-significant red seaweeds as a technically and economically viable agricultural enterprise for the United States. If successful, these processes will create jobs, particularly in rural coastal regions, and provide a steady supply of plant-based proteins for feeding a healthy population.

Animal Health Component

25%

Research Effort Categories

Basic

50%

Applied

25%

Developmental

25%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	2150	2020	90%
903	2150	3020	10%

Knowledge Area
903 - Communication, Education, and Information Delivery; 402 - Engineering Systems and Equipment;

Subject Of Investigation
2150 - Aquatic plants;

Field Of Science
2020 - Engineering; 3020 - Education;

Keywords

Goals / Objectives
Project Goal. The proposed research will support the development of environmentally and commercially sustainable aquaculture systems for intensified production of commercially significant red seaweed in land-based cultivation systems. In particular, Gracilaria species are a source of plant-based protein and industrial phyco-colloids, which together constitute nearly 90% of the ash-free dry weight of the biomass. The biomass is produced using non-potable seawater, CO2 from air or waste combustion gases, and sunlight. The research will focus on integration of biological and bioprocess engineering approaches to automate and intensify the inoculation and grow out processes in land-based cultivation systems, resulting in increased productivity and labor-saving production technologies designed to reduce risk for advancing the nascent red seaweed aquaculture enterprise in the United States.Project Objectives. This proposed project will integrate biological and engineering approaches to develop new propagation and intensified cultivations strategies for commercially-significant red seaweed within genus Gracilaria, and test these new strategies in land-based, scalable environments. The Project Objectives are to:1) Establish and maintain clonal strains for two Gracilaria species of emerging commercial significance, G. pacifica and G. parvispora;2) Develop scalable processes to inoculate Gracilaria onto a porous mesh support using a mechanical blending and fluidic injection process;3) Test inoculated Gracilaria panels in relevant scalable environments in collaboration with our private partner Oregon Seaweed;4) Develop extension programming to support and promote red seaweed aquaculture in the US Pacific region.

Project Methods
The Methods are organized around the Project Objectives.Objective 1: Establish and maintain clonal strains for Gracilaria species of emerging commercial significance by adapting techniques developed for Gracilaria vermiculophyllaTask 1-1. Establish new clonal strains. Previously, we developed procedures for establishing clean, clonal strains of G. vermiculophylla from field-collected plants adapted to both cold and warm waters through stepwise tissue surface decontamination, apical explant selection and growth under vigorous mixing to promote branching, and temperature acclimation. We will extend these methods to two Gracilaria species of emerging commercial significance for food and plant proteins: G. pacifica (California Ogo) and G. parvispora (Ogo).Task 1-2. Maintenance of clonal cultures. Clonal plantlets established under Task 1-1 will be maintained in 450 mL bubbler flasks within a temperature-controlled cold room with f/2 enriched artificial seawater medium to clean conditions for the progenitor stocks at 16 C. An array of aerated tanks (4 L, 20 L, 40 L) as well as 100 L raceway tanks will be used to generate inoculum at the 0.20 to 2.0 kilogram scale for use in activities described under Objectives 2 and 3.Objective 2: Develop scalable processes to inoculate Gracilaria onto a porous mesh support using a mechanical blending and fluidic injection processTask 2-1: Determine optimal conditions for fluidic injection of thallus tissue fragments onto porous mesh supports. Fluidic injection procedures recently developed in the OSU PI's laboratory for G. vermiculophylla will be adapted to G. pacifica or G. parvispora clonal cultures. Biodegradable, semi-rigid, mesh materials based on polybutylene succinate, which have a lifetime of up to 24 months in an open ocean environment before being microbially degraded will also be tested. Combinations of mesh opening size (e.g. 3 mm), fluid burst velocity (e.g. 10 m/sec, set by injection pressure) and burst duration (e.g. 0.5 sec) are tested until the blended fragments remain attached to the mesh. We will use a statistical design of experiments approaches to manage permutations of testing variables, and data will be statistically correlated (e.g. multi-variate ANOVA) to identify optimal parameters. Task 2-2: Fabricate and test scalable inoculation platform. To automate the inoculation process and facilitate scaling, a system that combines tissue blending and multiport injection onto a large mesh panels will be developed, tested, and used for scale-up studies under Objective 4. It will be designed to inoculate "panel elements" of 20 x 20 cm and 20 x 80 cm size at inoculation densities of 5-20 g FW per m2 panel area.Objective 3: Test inoculated Gracilaria panels in relevant scalable environments in collaboration with our private partner Oregon SeaweedTask 3-1: Cultivation of Gracilaria panels in re-circulating raceway. In the recirculating raceway cultivation system, seawater medium flows around the red seaweed panels, eliminating the need to use costly aeration to suspend the biomass. There are two unknown factors that must be addressed to reduce the technical risk for potential adopters of this technology: the effects of fluid velocity and panel spacing. Higher velocities will reduce boundary layer resistance and promote nutrient and dissolved carbon flux resulting in higher growth rates, but will require higher power consumption, increasing operating costs. Decreasing the spacing between rows of panels will increase areal density, but may result in light shading effects that reduce growth rate as the frond tissues are crowded closer together. Existing raceway systems will be used to characterize the effects of fluid velocity on the areal productivity for G. vermiculophylla panel arrays at 6.5 cm (dense) and 15 cm (open) spacing. Biomass accumulation on each panel will be measured with time and converted to areal productivity as detailed in our previous work, and photographs of panels will be used to assess effects of hydrodynamics on thallus morphology. Multi-variate ANOVA will be used to assess spatial variations in biomass accumulation, and Tukey's analysis will determine the statistical dependence of cumulative areal productivity on fluid velocity.Task 3-2: Cultivation of Gracilaria panels in open tanks at Oregon Seaweed. The Oregon Seaweed Garibaldi site presently has twenty 6000 L cylindrical tanks with nominal diameter of 3 m and liquid depth of 1.0 m. We will test the growth performance of Gracilaria on mesh panels at the Oregon Seaweed Garibaldi site, which is a two-hour drive from OSU-Corvallis. Clonal cultures of Gracilaria will be inoculated onto mesh supports (Task 3-2) at OSU and transported to the Oregon Seaweed site in Garibaldi, Oregon and placed into one of the 6000 L aerated tanks at their tank farm. Biomass growth on the panels will be measured weekly over a six-week grow out period by Oregon Seaweed personnel as part of the in-kind contribution to this project. Ash, total carbohydrate, pigment, and protein/amino acid (AA) content will be assayed at OSU. The presence of epiphytes (diatoms, filamentous algae, grazers) on thallus tissue will be assessed microscopically. bTests will be carried out in triplicate during fall, winter, spring, and summer grow out periods at a seawater exchange rate of 1-2 culture volumes per day. Nitrate in the effluent, a limiting nutrient, will be assessed weekly to determine if supplemental macronutrients (N,P via Proline f/2 Algae Food) are needed. In the test tank, the aeration rate, currently at nearly 0.1 vvm, will be reduced to below 0.02 vvm since with panel cultivation it is no longer necessary to use aeration to suspend the biomass. Average specific growth rate (% per day), areal productivity (g AFDW/m2-day in active zone), and total protein/amino acid content will be correlated to season by ANOVA. Water temperature, salinity, daily solar irradiance, pH, and aeration rate will also be monitored continuously by a Vernier Logger pro system.Task 3-3: Analytical procedures. Thallus morphology and extent of pigment formation will be assessed by microscopic image analysis using ImageJ. Standard techniques will be used to assay thallus tissue for total protein content, phycobiliprotein (R-phycoerythrin, phycocyanin) and chlorophyll a/carotenoid content, ash-free dry biomass, and C/N content. Amino acid profiles will be assayed by HPLC using facilities at the OSU Linus Pauling Institute Analytical Services Core. From the amino acid (AA) analysis, the PDCAAS score, a measure of protein digestibility corrected for essential AA content, will be determined. Carbohydrates will be profiled by HPLC available in the PI's laboratory.Task 3-4: Preliminary Techno-economic Analysis (TEA). The PI will assist Oregon Seaweed with preliminary TEA of the cultivation process, focusing estimation of operating and capital costs (OP/CAPX) for a hypothetical 1000 wet ton per year Gracilaria aquaculture facility that includes panel inoculation, grow-out, and monthly harvest. The analysis will be summarized in a spreadsheet model, a version of which will be made publicly available through our proposed Learning Group. We will compare outcomes, normalized to $ per ton, for cultivation of Gracilaria panels in aerated tanks vs. raceway technology using biomass productivity data obtained over the course of this proposed project. Cost sensitivity to nutrient addition, supplemental CO2 addition (e.g. a waste or combustion gas source), aeration rate, and current velocity will be assessed.

Progress 07/01/24 to 06/30/25

Outputs
Target Audience:Under Objectives 1 and 2, the target audience is the seaweed aquaculture research community. This audience matters because research outcomes must be documented and vetted if they are to find practical application. Under Objective 3, the target audience is land-based seaweed aquaculture growers, with specific emphasis on our industrial partner, Oregon Seaweed. This audience matters because research results must be translated to practical endpoints. Under Objective 4, the education and outreach activities are meant for broad education to a diverse audience on the unique and interesting attributes of land-based red seaweed aquaculture, using the USDA-supported research outcomes as resource material. This audience matters because red seaweed aquaculture, an emerging aquaculture sector in the US, needs a broader voice. Changes/Problems:The project was granted a one-year no-cost extension to complete the project objectives. What opportunities for training and professional development has the project provided?This project is providing training for two chemical engineering PhD students and one environmental engineering undergraduate student to apply process engineering principles to seaweed aquaculture technology development. This workforce training is unique because chemical engineers are vastly under-represented in the aquaculture workforce, and this is particularly true for chemical engineers in seaweed aquaculture, where a chemical engineering presence is essentially nonexistent, despite the strong need for process analysis in the land-based aquaculture sector. This project is also providing training in science communication for four undergraduate students in agriculture disciplines, as detailed in the Accomplishments for Objective 4. How have the results been disseminated to communities of interest?In Year 2, the team made 4 oral presentations at national/international aquaculture conferences highlighting research and outreach outcomes. Each presentation was selected for presentation based on peer review of submitted abstracts. Each conference presentations acknowledged USDA support. Details are provided below. Alzanbaki, H. (student speaker), Rorrer, G.L. Novel Cultivation Process for the Red Seaweed Gracilaria parvisopora. Breakout Session 2: Cultivation & Harvesting-Technologies toward enhanced algal cultivation, harvesting, and analyses, 18th Algae Biomass Summit 2024, Oct. 21, 2024, Houston TX. Veremchuk, A. (student speaker), Rorrer, G.L. Effects of Fluid Velocity on CO2 Uptake Rate by the Red Seaweed Agarophyton vermiculophyllum. Paper #983, Session on Macroalgae Aquaculture: Supporting a Successful Seaweed Sector, AQUACULTURE 2025, March 8, 2025, New Orleans, LA. Chan, S. (Co-PI, speaker), Rorrer, G., Alzanbaki, H., Veramchuk, A., Campbell, R., Hicks, E.,Sokolov, Y. The Red Seaweed Learning Collaborative: Extension Enhancing Research Impact. Session on Macroalgae Aquaculture: Supporting a Successful Seaweed Sector, AQUACULTURE 2025, March 8, 2025, New Orleans, LA. Rorrer, G.L. (speaker), Evans, S. Aeration and Power Requirements for CO2-Replete Cultivation of the Red Seaweed Devaleraea mollis (Pacific Dulse) in Land-Based Systems. Session O4.2 - Aquaculture Methods 2, 25th International Seaweed Symposium, May 9, 2025, Victoria, BC. What do you plan to do during the next reporting period to accomplish the goals?Selected activities under each Project Objective to achieve the project goals are highlighted below. Objective 1: Determine full biochemical composition of the highly branched, compacted Gracilariaparvispora cultivar to verify its value as a source of food and protein. Prepare one journal article describing culture development. File Invention Disclosure at Oregon State University on novel Gracilaria cultivar development. Objective 2: Prepare two journal articles, one focusing on hydrodynamics and a second focusing on grow-out as detailed in the Accomplishments. As part of the journal article development, develop mathematical model for CO2-delivery limited grow out process. File Invention Disclosure at Oregon State University for novel raceway tank modification, demonstration of intensified grow out, and microalgal contamination control system. Objective 3: Prepare journal article based on aeration cost and CO2 emissions detailed under Accomplishments. Objective 4: Post Red Seaweed Learning Group website that includes student-developed video Reels and Storyboard.

Impacts
What was accomplished under these goals? Accomplishments under Objective 1, Gracilaria cultivar development. During Year 1, under Objective 1, we developed strains of the red seaweed Gracilaria parvispora where the seaweed biomass was compacted into dense balls of highly-branched frond tissues of 2 to 7 cm diameter. During Year 2, we studied the fundamentals of the frond tissue branching process under different fluid agitation patterns with the goal of controlling tissue densification, which is key to intensification of volumetric biomass productivity. Details are provided under Objective 2. Accomplishments under Objective 2, intensified cultivation of Gracilaria ball cultivar in a raceway tank. During Year 1, we developed a paddle wheel raceway cultivation system for intensified, scalable grow-out of the Gracilaria compacted seaweed balls developed under Objective 1.In Year 2, these studies were continued with specific focus on characterization of hydrodynamic performance and biomass productivity under different aeration modes within the paddle wheel raceway system. Hydrodynamic Performance. With respect to hydrodynamic performance, we compared the circulation time distribution of the seaweed balls in the paddle wheel raceway under two aeration modes: (1) fine bubble aeration using a porous disk sparger positioned immediately downstream of the paddle wheel (disk aeration), and (2) coarse-bubble aeration using a tube aerator lining the length of the flow channel (channel aeration). The channel aeration mode created a helical secondary circulation pattern superimposed on the bulk flow provided by the paddle wheel. The average circulation time of the compacted seaweed balls was not affected by aeration mode. However, the velocity distribution for channel aeration was much higher relative to disk aeration due to the helical flow pattern superimposed on the bulk linear flow. This resulted in significant internal rotation of the seaweed balls, which in turn compacted the biomass density within the ball to at least 85 g FW/L through intensified frond branching. Therefore, biomass intensification can be externally controlled through secondary hydrodynamic flows induced by superimposing aeration on bulk fluid flow generated by the rotating paddle wheel. Biomass Productivity. The biomass grow-out of the compacted seaweed balls in the paddle wheel raceway cultivation system was tested under the two aeration modes (fine bubble disk aeration, coarse bubble channel aeration) described above. Enriched Provasoli f/4 nutrient (nitrate, phosphate) was added weekly to the cultivation system to prevent nutrient limitation and was verified by nitrate uptake and material balance measurements. The nominal growth rates were 7.4% / day for fine-bubble disk aeration, and 4.4% / day for coarse-bubble channel aeration. Although Gracilaria seaweed balls were compacted more densely under coarse-bubble channel aeration, the overall biomass productivity decreased by 40% relative to fine-bubble disk aeration. The volumetric mass transfer coefficient (kLa) for coarse-bubble channel aeration was 3.5 1/hr, which was only 50% of the fine-bubble disk aeration of kLa = 7.0 1/hr. Therefore, biomass productivity was CO2 delivery limited when ambient CO2 in air was used as the sole carbon source, and the biomass productivity scaled directly to kLa for CO2 mass transfer. Therefore, CO2 transfer rate must be optimized in these systems to achieve target biomass productivity. Contamination Control. The paddle wheel raceway tank liquid surface is open to the atmosphere. A complicating factor at high biomass loading is the appearance of green microalgae in the tank, which competes for nutrients, light, and CO2 delivery in the tank. To manage green microalgae contamination, we installed a submerged flow-through UV-sterilizer system directly into the tank. In control experiments, the UV power was optimized to keep the green microalgae contaminants below detectable levels (typically cell counts of less than 100 cells/mL) by increasing the UV power until the specific death rate exceeded the specific growth rate of the contaminant. Accomplishments under Objective 3, field tests in relevant commercial facilities with partner Oregon Seaweed. Under Objective 3 for Year 2, efforts focused the development of computational tools for aeration operating cost for tumble tank cultivation of Pacific dulse and CO2 emissions associated with powering the aeration system. Aeration is the dominant operating cost and is also main source of net CO2 emissions resulting from electrical power consumption of the air compressor. Aeration Operating Costs. We developed a computational model for prediction of operating costs and CO2 emissions for cultivation of Pacific dulse in aerated tumble tanks. The model predicts the aeration rate requirements for grow-out using ambient CO2 in air as the carbon source for biomass production, and the electrical power consumption by the air compressor during aeration based on air flow and pressure drop measurements. For example, consider a base case where the target areal biomass productivity of 28 g AFDW/m2-day. The required aeration rate using CO2 in ambient air as the sole carbon source is 0.68 L air/L-liq-min for coarse-bubble aeration, and the aeration energy to produce this biomass is 2.4 kW-hr/kg FW, which corresponds to $0.31 /kg FW biomass if the electricity cost is $ 0.10 kW-hr and the compressor efficiency is 75%. CO2 Emissions from Aeration. Using this model, the life cycle CO2 emissions were then estimated based on CO2 uptake (carbon credit) by biomass production and CO2 emission (carbon deficit) associated with electrical power consumption for aeration. This analysis showed that if CO2 in air is the sole carbon source for biomass production, the required aeration rate to sustain the target biomass productivity results in carbon emissions that exceed biomass carbon capture by a factor of10, if electrical power for the compressor is sourced from a natural-gas fired power plant. However, if waste CO2 from another sourceis added to the aeration gas, then the CO2 emissions can become negative. For example, at a target areal biomass productivity of 28 g AFDW/m2-day detailedin the base case above, using air supplemented with a waste CO2 source to final concentration of just 1050 ppm CO2 (2.5X ambient CO2), net CO2 emission is zero, and theaeration rate is reduced to 0.17 L air/L-liq-min for coarse-bubble aeration. The aeration energy to produce this biomass is now only 0.22 kW-hr/kg FW, which corresponds to aeration cost of $0.029 /kg FW biomass if the electricity cost is $ 0.10 kW-hr and the compressor efficiency is 75%. This is a cost reduction of over 10X relative to the base case. Accomplishments under Objective 4, develop extension and outreach program. Under Objective 4 for Year 1, we established the Red Seaweed Learning Collaborative, which focuses on red seaweed aquaculture science communication. These efforts are led by a diverse team of 4 undergraduate and 3 graduate students, in collaboration with the Oregon Sea Grant program. Under Objective 4 for Year 2, the undergraduate student team under the mentorship of co-PI Dr. Samuel Chan developed a storyboard for the video footage collected in Year 1. The video footage from Year 1 was edited into a series of narrated video clips, each of about 2 min duration, which highlighted research "in progress" under Objectives 1 and 2, and our field tests at Oregon Seaweed under Objective 3. The "real time" aspect of this effort featuring students in the videos and undergraduate students as the production team is a differentiating feature of our communications strategy. These videos and the storyline were loaded to the website for the Red Seaweed Learning Group. However, the website is still in development and is not yet live as of September 30, 2025.

Publications

Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Veremchuk, A. (student speaker), Rorrer, G. Effects of Fluid Velocity on CO2 Uptake Rate by the Red Seaweed Agarophyton vermiculophyllum. Paper #983, Session on Macroalgae Aquaculture: Supporting a Successful Seaweed Sector, AQUACULTURE 2025, March 8, 2025, New Orleans, LA.
Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Alzanbaki, H. (student speaker), Rorrer, G.L. Novel Cultivation Process for the Red Seaweed Gracilaria parvisopora. Breakout Session 2: Cultivation & Harvesting-Technologies toward enhanced algal cultivation, harvesting, and analyses, 18th Algae Biomass Summit 2024, Oct. 21, 2024, Houston TX.
Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Chan, S. (Co-PI, speaker), Rorrer, G., Alzanbaki, H., Veramchuk, A., Campbell, R., Hicks, E.,Sokolov, Y. The Red Seaweed Learning Collaborative: Extension Enhancing Research Impact. Session on Macroalgae Aquaculture: Supporting a Successful Seaweed Sector, AQUACULTURE 2025, March 8, 2025, New Orleans, LA.
Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Rorrer, G.L. (speaker), Evans, S. Aeration and Power Requirements for CO2-Replete Cultivation of the Red Seaweed Devaleraea mollis (Pacific Dulse) in Land-Based Systems. Session O4.2 Aquaculture Methods 2, 25th International Seaweed Symposium, May 9, 2025, Victoria, BC.

Progress 07/01/23 to 06/30/24

Outputs
Target Audience:Under Objectives 1 and 2, the target audience is the seaweed aquaculture research community. This audience matters because research outcomes must be documented and vetted if they are to find practical application. Under Objective 3, the target audience is land-based seaweed aquaculture growers, with specific emphasis on our industrial partner, Oregon Seaweed. This audience matters because research results must be translated to practical endpoints. Under Objective 4, the education and outreach activities are meant for broad education to a diverse audience on the unique and interesting attributes of land-based red seaweed aquaculture, using the USDA-supported research outcomes as resource material. This audience matters because red seaweed aquaculture, an emerging aquaculture sector in the US, needs a broader voice. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Under Objectives 1-3, during Year 1, two graduate students carried out the experimental work and received training in red seaweed cultivation techniques, and methodologies for land-based seaweed aquaculture. Under Objective 4, during Year 1, four undergraduate students received training in aquaculture science communication. How have the results been disseminated to communities of interest?None to date for Year 1. But for Year 2, planned activities are: Upcoming presentations featuring USDA-funded research: Algal Biomass Summit, Oct. 2024; Aquaculture America March 2025 3-4 publications (see next reporting publication activities below) Continued collaboration with industrial partner Oregon Seaweed (See Objective 3 below). What do you plan to do during the next reporting period to accomplish the goals?Selected activities under each Project Objective to achieve the project goals are highlighted below: Objective 1: Determine full biochemical composition and photosynthetic growth parameters of the highly-branched, compacted G. parvispora cultivar. Prepare one journal article. File Invention Disclosure at Oregon State University on novel Gracilaria cultivar development. Objective 2: Determine process conditions for optimal cultivation of compacted G. parvispora balls in the modified raceway tank. Prepare two journal articles, one focusing on hydrodynamics and a second focusing on grow-out. File Invention Disclosure at Oregon State University for novel raceway tank modification and demonstration of cultivation. Objective 3: Demonstrate optimal grow out of G. parvispora panels in commercial production tanks with private partner Oregon Seaweed. Provide scale-up and cost calculations for 1000 lb/month fresh biomass production. Prepare short article on outcomes to a trade publication such as Aquaculture Magazine. Objective 4: Post Red Seaweed Learning Group website that includes student-developed video Reels and Storyboard. Upcoming presentations featuring USDA-funded research: Algal Biomass Summit, Oct. 2024; Aquaculture America March 2025.

Impacts
What was accomplished under these goals? Accomplishments under Objective 1, Gracilaria cultivar development. Under Objective 1 for Year 1, a new cultivar for the red seaweed Gracilaria parvispora was developed, where the morphology was altered to create a compact, spherical ball of highly-branched cylindrical thalli tissue. Gracilaria parvispora is a popular edible seaweed native to Hawaii that is closely related to Gracilaria pacifica, which is found on the US pacific coastal waters. The native cultivar of G. parvispora consists of a loosely tangled mass of cylindrical thalli that does not does not suspend well in conventional aeration tank culture because the thalli become entangled and settle to the bottom of the tank. A collection of G. parvispora was introduced into tissue culture to generate clean clonal thalli tissue. Small linear fragments of thalli tissue were then grown up in a tumble tank. A rising stream of air bubbles promoted rapid rotation of the tissue fragments in the water column and induced branching and fractal growth of the thalli, ultimately forming a compacted spherical ball of highly-branched seaweed biomass with diameter ranging from 2 cm up to 7 cm, with mass of 4-6 g fresh weight (FW) per ball. This new morphological cultivar, the compacted Gracilaria ball, suspended easily under aeration, and did not aggregate or settle to the bottom of the tank. The biochemical composition and photosynthetic growth parameters of the G. parvispora clonal tissue culture was determined. The protein content of the biomass was typically 20 wt% of ash-free biomass. The photosynthesis-irradiance (P-I) curve was characterized by measuring oxygen evolution rate vs. light intensity. The P-I curve data were fitted to an exponential model, with light intensity at 63% of saturation equal to 40 mmol photons/m2-s. Under light-saturated cultivation in Provasoli enriched seawater medium, the typical specific growth rate was 7% per day. Accomplishments under Objective 2, intensified cultivation of Gracilaria ball cultivar in raceway tank. Under Objective 2 for Year 1, the direction of the project was changed to determining the feasibility of cultivating the Gracilaria compacted seaweed balls in a recirculating raceway tank. In the proposal narrative, it was originally proposed to immobilize and densify the thalli tissue onto a porous mesh panel, and then load an array of panels into the raceway tank. However, since the Gracilaria compacted ball cultivar developed under Objective 1 was already densified into a compact, highly-branched spherical mass, it made sense to determine if this cultivar could be cultivated directly as free suspension in the raceway tank without panel immobilization. The first step was to assess if the compacted Gracilaria balls could be suspended in a raceway tank without aeration. The raceway test tank was a 100 L Microbio Engineering RW0.5 tank with single paddle wheel of 50 cm diameter. Gracilaria balls of 100 g FW were loaded into the tank to density of 1 g FW/L. Two sizes of the Gracilaria balls (2 cm and 5 cm diameter) were tested. Selected Gracilaria balls were labeled with a colored tag so that their trajectory in the raceway tank could be tracked by video. The time to complete one circuit by a given Gracilaria ball in the tank was measured over circulation 30 cycles. The circulation time was then divided by the center path length of the raceway tank to estimate the average Gracilaria ball velocity. The effects of paddle wheel rotation rate (2 to 16 rev/min) on the suspension and velocity of the seaweed balls (2 cm vs. 5 cm) were then determined. The results showed that a minimum paddle wheel rotation rate of 4 rev/min was required to suspend the Gracilaria balls and keep them from settling to the bottom of the tank. The seaweed ball speed was then linearly dependent on the paddle rotation rate from 5 to 16 rev/min, ranging from 9 to 26 cm/sec for large (5 cm) Gracilaria balls and 5 to 18 cm/sec for small (2 cm) Gracilaria balls. The slower speed of the smaller balls was attributed to the observed deviations in linear trajectory as the smaller balls moved through tank. Under Objective 1, we learned that tumbling action of the Gracilaria balls was needed to promote continued fractal growth and thalli branching that leads to high biomass density. Therefore, to promote tumble action of the seaweed balls in the raceway tank, the tank was modified to include an aeration line along the straight section of the raceway. When the air flow was turned on, a secondary radial flow was superimposed on the axial flow generated by the paddle wheel rotation. Submerged video footage revealed that the Gracilaria balls moved in a corkscrew trajectory. The CO2/O2 mass transfer characteristics of the modified raceway configuration were determined. The aeration mass transfer coefficient ranged from 4 to 6 1/hr at 0.1-0.2 L air/L liquid-min air flow and 10 rev/min paddle wheel rotation rate, sufficient to provide CO2 delivery to the biomass to sustain a 7% per day average growth rate over 28 days from a 1 g FW/L initial stocking density. Accomplishments under Objective 3, field tests in relevant commercial facilities with partner Oregon Seaweed. Under Objective 3 for Year 1, we initiated pilot field cultivation tests of the compacted Gracilaria ball cultivar described under Objective 1. The field tests were conducted in August of 2024 in collaboration with our private partner, Oregon Seaweed, at their Garibaldi, Oregon tank farm. The inoculum for the field tests was generated in the PIs laboratory at Oregon State University, where seaweed balls were immobilized on a mesh panel. Specifically, compacted seaweed balls of 2-5 cm diameter were loaded between two ply of 0.5 inch netting around a square frame 30.5 cm per side to total 454 g (1.0 lb) fresh weight. Three Gracilaria seaweed panels, each with equivalent biomass loading of 4.8 kg/m2 panel area, were then submerged in a vertical orientation to a liquid depth of 30 cm into one of the 2500 gal production tanks at Oregon Seaweed. The tank was aerated from the center, the panels were aligned parallel to the current flow of 40-50 cm/sec nominal velocity generated by aeration. Seawater sourced from Tillamook Bay without treatment was added to each tank at nominally 1-2 exchanges per day, with nitrate concentration ranging from 10-20 micromol/L. No additional nutrients were added. The light intensity during the day averaged 25 microE /m2-sec incident to the center of the vertically-positioned panel, and temperature averaged 17 C. After 28 days, biomass generation nearly doubled to 7.7 kg/m2 panel area. No epiphytic growth was observed on the biomass itself, although some of the actively growing biomass changed from red to yellow-green color due to low nitrogen levels. Overall, these initial tests demonstrate the feasibility of grow-out for the compacted Gracilaria seaweed balls in relevant commercial environments. Accomplishments under Objective 4, develop extension and outreach program. Under Objective 4 for Year 1, we established the Red Seaweed Learning Collaborative, which focuses on red seaweed aquaculture science communication and broadening participation. These efforts are led by a diverse team of 4 undergraduate and 2 graduate students, in collaboration with the Oregon Sea Grant program. The team has initiated development of a website (still under construction), and has produced a series of ten "Red Aglae for Real" 30 sec narrated video reels of research conducted under Objectives 1-3 given above, that will be loaded to the website.

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