Tropical Seaweed Research
The main goal of the project is to optimize production of desirable macroalgal bioproducts and biofuel at a significantly lower cost than current technologies. Here we focus on the tropical red alga, Eucheumatopsis isiformis (Eucheuma isiforme), with an existing market for production of carrageenan as an essential step in the pathway towards viable conversion of macroalgal biomass to fuel. We have five principal objectives that address the risks and roadblocks that currently limit the economic viability of macroalgae as feedstock for biofuels:
Goals: Perfect our design and rigging methods to ensure a farm design and operations that are compatible with exposed, offshore conditions with minimal environmental impacts.
Starting in late 2020/early 2021, our experimental ocean farms will begin an optimization process based on field studies and smaller deployments during the first year of field deployments. Vertical test moorings will be used to determine the best culture depth. Mini-arrays will be studied for two harvest cycles (or four months) to understand the growth conditions and environmental forcing on planted growlines, as well as test new mechanized seeding and harvesting strategies. Load cells will inform our modeling efforts, and drag tests will be used to build a robust drag model.
Goals: Physicochemical – Characterize nutrient and hydrodynamic loads at the farm scale.
Biological – Identify the social and environmental impacts and benefits of macroalgal farms to ensure sustainability.
We will measure environmental parameters at farm sites including benthic structure before, during, and after installation of the farm system in the field to understand the range of conditions on a daily and seasonal cycle, and the impact of the installation on environmental conditions and ecosystem function. We will continue to work with local stakeholders to ensure farm systems are both environmentally and socially sustainable.
We will utilize a combination of instruments and methods in collaboration with MARINER Category 3 (, , and ) and 4 () teams and other partners to understand daily (e.g., underwater temperature loggers) and monthly (e.g., monthly pH, salinity, and nutrient sampling) environmental variations and algal health, as well as bathymetry changes (e.g., side scan sonar) to build a complete picture of the farm site pre- and post-deployment and to better inform and validate the modeling efforts. See Modeling for more details. Biological data from visual and acoustic surveys will help us better understand ecosystem services (e.g., nursery habitat or improved water quality) the algal farms might provide and how larger animals like sea turtles and marine mammals interact with the structure.
Goals: Understand how biology of tropical algae is impacted by environmental variables.
The red alga, Eucheuma isiforme, native to the tropical and subtropical western Atlantic, as well as the Gulf of Mexico, is the only species native to the U.S. EEZ with a ready, high-value market, namely via its high carrageenan content, as well as propagation via vegetative cuttings that eliminates the need for expensive nursery facilities. The global carrageenan market produces 60,000 tonnes from Eucheumoids vegetatively in mainly China and Indonesia, valued at $750 million/year.
We will measure how the metabolite composition and growth rate of macroalgae vary under different cultivation conditions to determine the optimal conditions for production of bioproducts or characteristics of interest, particularly carrageenan content and quality. Additionally, we will measure baseline parameters needed for the nutrient and growth models, including growth and photosynthesis, nutrient uptake, and mortality.
We will use transcriptomics to determine genetic markers (SNPs) in experimental strains and to identify differentially expressed genes correlated with characteristics of interest, particularly carrageenan content and quality. MARINER collaborators (UCSB) have developed autonomous and semi-autonomous technologies capable of monitoring biomass productivity and physiological status, as well as the environmental conditions that control its near-term production for temperate algae, but will be developing analogous systems for tropical algae.
Goals: Use computational modeling tools to facilitate the assessment and siting of macroalgae cultivation systems.
Simulation of offshore macroalgal farms requires knowledge of ocean conditions at the site of interest. This includes standard oceanographic physical, chemical, and biological parameters.
Macroalgae are grown from suspended structures that have the potential to generate new flow features that have yet to be computationally or observationally explored. Teams will develop a fine-scale turbulence model to assess how flow attributes, hydrodynamics forces, and nutrient availability respond to different farm designs and cultivation techniques.
