Current Projects ~ Marine Biogeochemistry & Phytoplankton Biogeography
Plastic Pollution in the Ocean
Plastics are a persistent pollutant that affect the growth rates of organisms, as well as their nutritional role in the food web and ability to transfer toxins. Plastics influence the carbon (C) cycle by affecting how well plastics attached to C float or sink, and can influence human health.
The Mackey Lab conducts experiments using laboratory cultures and natural assemblages of microscopic animals, called zooplankton, to determine their feeding behaviors on plastics of different type, size, shape, and color. The goal is to understand how plastic pollution could change marine microbial communities in the future.
Shipping Industry Emissions
Shipping of goods is a world wide industry that consumes fossil fuels and produces aerosol emissions that can influence phytoplankton growth. New regulations require the use of "cleaner" versions of fuels, but the outcome on marine microorganisms remains unknown.
The Mackey Lab measures the nutrients and trace metals in ship emissions that burn different types of fuel, and uses field experiments to understand how phytoplankton respond to these aerosols. We aim to inform policy decisions about clean fuel and alternative fuel technologies.
Southern California Aerosols
Santa Ana winds are fast, warm, and dry winds that blow from the Great Basin toward the Southern California coastline during fall and winter months, and that carry aerosol particles from wildfires, terrestrial dust, and human emissions toward the coastal ocean.
The Mackey Lab measures nitrogen content in local aerosols to understand if and how Santa Ana winds influence coastal phytoplankton communities, and uses carbon and nitrogen isotope and air mass back trajectory analyses to identify important nutrient sources.
Harmful Algal Blooms
Harmful algal blooms (HABs) can produce toxins that affect the health of animals and people. Some blooms are due to cyanobacteria that thrive in estuaries. The toxins they generate are called "cyanotoxins."
The Mackey Lab is partnering with the Southern California Coastal Water Resource Program (SCCWRP) to deploy bivalves as biological sensors of cyanotoxins in dozens of estuaries in S. California. We aim to understand the land management practices that give rise to toxic cyanobacteria, and to advise land management practices to mitigate HABs.
Newport Native Species
Prochlorococcus is the most abundant photosynthetic organism on Earth and is typically found in the open ocean. Recently, a population has been identified along the Newport Beach coastline that recurs each summer when the waters are warm.
The Mackey Lab is using high frequency in situ oceanographic monitoring and single cell genomics to determine if this population is introduced in warm surface currents, or if it is a novel strain specially adapted to the coastal environment.
Mercury Bioaccumulation
Mercury is a potent neurotoxin that bioaccumulates in aquatic food webs, increasing 10-fold with each trophic level. However, very little is known about how phytoplankton at the base of the food web take up mercury, even though this first step leads to a million-fold increase in concentration.
The Mackey Lab is collaborating with the San Elijo Lagoon Conservancy to understand the spatial and temporal factors that influence phytoplankton mercury uptake, such as tidal, diel, and seasonal cycles.
Wastewater Impacts
Southern California is home to ~23 million people, and Southern California beaches bring over $14 billion in tourism revenue each year. The health of coastal waters is vital to our economy, culture, and lifestyle.
The Mackey Lab partners with the Orange County Sanitation District to collect oceanographic and phytoplankton samples on monthly cruises offshore of Newport Beach. We measure the effects of wastewater outfall on local biogeochemistry and phytoplankton community composition, including monitoring changes in harmful algal bloom species.
Chromatic Acclimation
Chromatic adaptation is the process by which cells change their pigment compositions to preferentially absorb different wavelengths of light. The cyanobacterium Synechococcus undergoes chromatic adaptation by substituting different molecules into its phycobillisome antenna.
The Mackey Lab explores whether chromatic adaptation in Synechococcus occurs in response to factors other than spectral quality. We use sophisticated photophysiological and proteomic approaches to characterize pigment changes under controlled laboratory conditions.
Copper Toxicity
Nutrients can limit phytoplankton growth when the availability is low, affecting competition between species for shared nutrient resources. But what about resources like copper that are toxic at high levels?
The Mackey Lab is developing an ecological framework based on Resource Ratio Theory to explain how competition is affected when a resource is both a nutrient and a toxicant. We are using published literature toxicity thresholds for diverse species and newly-measured thresholds for marine diazotrophes to develop the modelling framework.
Southern California Wildfires
In December of 2017, the Thomas Fire burned 281,893 acres in Santa Barbara and Ventura Counties, sending large amounts of ash out to sea. Heavy rains in January 2018 then caused mudslides, which also reached the coastal ocean.
The Mackey Lab uses in situ monitoring and incubation studies to determine how fires and rain events affect coastal phytoplankton by influencing ash deposition and sediment transport. We compare responses at Santa Barbara where the fire was most intense, to Newport Beach, which is further south and unaffected by the fires.
Southern California Wildfires
In December of 2017, the Thomas Fire burned 281,893 acres in Santa Barbara and Ventura Counties, sending large amounts of ash out to sea. Heavy rains in January 2018 then caused mudslides, which also reached the coastal ocean.
The Mackey Lab uses in situ monitoring and incubation studies to determine how fires and rain events affect coastal phytoplankton by influencing ash deposition and sediment transport. We compare responses at Santa Barbara where the fire was most intense, to Newport Beach, which is further south and unaffected by the fires.
The Salton Sea: A Dwindling Oasis
In 1905 the Colorado River was accidentally diverted, creating the Salton Sea.In the mid 1900s, it was slated to be a tourist destination, seeded with fish and hosting over 400 species of birds. However, severe drought has caused the Sea to become too salty, resulting in fish die-offs and loss of bird migratory territory. The dust from exposed dry lake beds leaves toxic metals and pollutants behind, causing asthma in humans in SoCal.
The Mackey lab uses in situ and incubation measurements to understand how salt and toxins in the sediments affect plankton, .and how the plankton community in the Salton Sea will change in the coming decades.