Sustainable Aquaculture for California – Make it Local
Assessment of practical methods for re-establishment of northern California bull kelp populations at an ecologically relevant scale
Mike Graham and Scott Hamilton received funding from California Sea Grant to identify cost-effective ways of enhancing bull kelp (Nereocystis luetkeana) recruitment at local to regional scales. Ocean warming and seastar wasting disease, which caused the collapse of populations of an important sea urchin predator (the sunflower star Pycnopodia), resulted in dramatic declines and overgrazing of bull kelp populations. Over broad scales, productive kelp forests shifted to unproductive sea urchin barren grounds. The lack of sources of bull kelp reproductive material paired with high grazing pressure make natural re-establishment challenging. Further, bull kelp is an annual species that primarily occupies areas of high water motion, thus it exhibits a high degree of natural temporal variability within and across seasons. Despite this, bull kelp is an ecologically and economically impactful species serving as habitat and food to many marine species. The goals of restoration efforts are to add bull kelp reproductive material and sporophytes (i.e., established juvenile size classes) to areas cleared of sea urchins to re-establish kelp populations through natural recruitment.
The four ways of re-establishment include: (1) concentration of reproductive sori in bags, (2) attachment of aquaculture produced free-floating sporophytes by SCUBA, (3) scattering of bull kelp seeded gravel by SCUBA, and (4) surface scattering of bull kelp seeded gravel by boat. The California Ocean Protection Council (OPC), California Department of Fish and Wildlife (CDFW) and Reef Check California have been working to establish urchin removal sites in Mendocino County, which will be used to test the different modes of outplanting bull kelp for our restoration efforts.
We have three 1000-gallon tanks at the MLML Aquaculture Facility that will serve as broodstock of bull kelp sporophytes. Smaller trough tanks will hold gravel for the establishment of seeded substrate. Initial testing is ongoing for production of seeded substrates and free-floating sporophytes via tumble culture.
Quantifying volatile bromocarbon emissions from seaweed aquaculture in California (Funders: CA Sea Grant: $59,445 and CSU COAST $29,723)
Max Grand and Luke Gardner were awarded $89,168 from California Sea Grant and CSU COAST to quantify bromoform (CHBr3) emissions from seaweed species that may be used as feed supplements to reduce methane emissions from ruminant livestock. Bromoform is a volatile gas emitted naturally by nearly all macroalgae, which is involved in atmospheric ozone depletion. It is also the active ingredient in experimental seaweed feed additives that yields substantial reduction in ruminant livestock methane production. The anticipated expansion of seaweed aquaculture for the cattle industry, particularly if focused on some of the strongest bromoform seaweed emitters (e.g., Asparagopsis), may significantly impact the natural sea-to-air flux of brominated substances thus the inventory of ozone in the atmosphere. Although the reduction of methane emissions from livestock is highly desirable from a climate change perspective, this project will help determine whether a seaweed additive feed remedy is reducing methane emissions only to introduce another equally or more deleterious climate pollutant. In this work PIs Grand & Gardner, MLML graduate student Jessica Metter (Chemical Oceanography Lab) and Dr. Michael Schuppenhauer (Lawrence Berkeley National Laboratory) will quantify bromoform emissions from a variety of seaweed species in aquaculture tanks mimicking long-line seaweed aquaculture practices. This work will provide much needed bromocarbon production data from a range of temperate seaweeds, which can then be used to facilitate the development of a truly sustainable seaweed aquaculture industry in California and beyond.
Tumble culture of seaweeds
String of shells settling substrate for Olympia Oysters
Ecophysiology of Olympia oysters grown in aquaculture, and implications for outplanting success (Funders: CA Sea Grant: $59,877 and CSU COAST: $29,974)
Amanda Kahn, Luke Gardner, and Kerstin Wasson (Elkhorn Slough National Estuarine Research Reserve) were awarded $89,851 from California Sea Grant and CSU COAST to study the ecophysiology and energetics of Olympia oysters grown in aquacultures. Olympia oysters (Ostrea lurida) are the only native oyster species in California. The O. lurida population in Elkhorn Slough has declined and has experienced several years of zero recruitment. Earlier work at the MLML Aquaculture Center by Drs. Wasson and Gardner have demonstrated that aquaculture can be used to grow up oysters, with the goal of outplanting them in Elkhorn Slough to supplement and support existing populations. With this context, PIs Kahn, Grand, and Wasson, and graduate students Jacob Harris and Anna Heasley (Invertebrate Ecology Lab) will now study the energetics and metabolism of captive-reared Olympia oysters to optimize growing conditions and identify energetic bottlenecks in the growth process across different life stages. Results from this work will support outplanting efforts by enhancing rearing success. It will identify the most sensitive life stages of captive and wild oysters, which will help in all restoration efforts up and down the coast. Results of this research will also be of interest to commercial aquaculture growers interested in including a native oyster species and diversifying their growing portfolio. This project is set to begin in February 2022.
MLML 15-Tank Setup and Seaweed Growth Testing
In 2019, MLML (Mike Graham) will perform rapid response experiments to gather initial data on seaweed nutrient uptake to parameterize initial growth models and design future multi-input tank experiments. The response of seaweed growth and productivity to nutrient inputs is difficult to study in natural systems due to (1) reliance of seaweeds on numerous essential nutrients, (2) high natural variability in nutrient concentrations, and (3) positive and negative correlations in concentration among numerous nutrients. As such, MLML will design a meso-scale tank experiment, whereby variability in seaweed growth and productivity will be studied in response to variability in individual nutrients (added to artificial seawater) under variable environmental conditions (e.g. light, temperature, salinity, etc.). Prior to such detailed studies, however, MLML will perform a simple natural-seawater nutrient depletion experiment to estimate the initial rates of nutrient uptake and identify the rank in which nutrients are depleted from natural seawater.
Green tanks in foreground used for new macroalgae growth experiments
Scallops: The Next Species to Culture at MLML
Most of the cultured scallops that are eaten in the U.S. come from Japan and China, so developing the methods to farm scallops in California would reduce the carbon footprint associated with shipping scallops across the oceans and would allow us to buy local. So MLML is working with local aquaculture companies to develop methods for rearing native scallops. This will entail establishing a hatchery and nursery, growing the microalgae to feed these filter-feeders, and experimenting with various environmental factors to formulate optimum growth. In 2019, we will begin a number of experiments with this new species to be included in our aquaculture facility. Pictured here are the first scallops brought in for spawning and the microalgae room with the ready food supply.
Olympia Oysters used as brood stock at MLML
Making Babies: Restoring the Native Olympia Oyster (Ostrea lurida) Population in Elkhorn Slough
With $32,000 of new 2019 funding and collaboration with the Elkhorn Slough National Estuarine Research Reserve and Elkhorn Slough Foundation, MLML has partnered with Kerstin Wasson to provide new Olympia oysters to Elkhorn Slough. This is an attempt to rebuild the small population of Olympia Oysters into a large enough biomass to self-populate and grow the population. In 2018, MLML spawned and grew Olympia oysters that were later transplanted into Elkhorn Slough. With new funding we hope to be more successful in greatly expanding this important Slough inhabitant in fall of 2019.