My photo of Durvillaea antarctica was recently published in the Natural History Museum's (London) "Evolve Magazine", in which the article discusses the beauty and many uses of seaweeds. Rad.
September and October were dense with work and preparation. In late August, I switched gears with respect to scheduled research due to systemic equipment malfunction in the growth flumes, which can only be explained by demonic intrusion (Hurlbert 1972). So instead of investigating the influence of water flow + drag forces on the C and N metabolism of kelps, my current research in the Martone Lab now targets the identification of patterns in the activity of carbonic anhydrase (an enzyme that interconverts dissolved CO2 and HCO3-) across multiple macroalgal species within a single community. This includes investigating what might help explain these patterns in activity. Better understanding the expression and activity of carbonic anhydrase (CA) will allow more informed exploration of carbon use and partitioning within algal communities, as well as help refine the ecological function (with respect to carbon sequestration) of specific species or even species interactions.
How am I tackling this at the moment? I collected replicates of every species possible at one field site (Ogden Pt, Victoria, BC) and transferred them back to the lab at UBC in Vancouver. Upon returning to the lab, I learned that the collection included 39 species of macroalgae (2 green, 27 reds, 10 browns)! These were acclimated in the lab, each species exposed to the same light, nutrients, and temperature. After a day of acclimation, I sampled tissues for the following analyses: carbonic anhydrase activity, nitrate reductase activity, pigments, and oxygen evolution in seawater with low CO2 concentrations (this helps determine the importance of dissolved CO2, opposed to HCO3-, as a carbon source for photosynthesis).
What have I found so far? Here is a snapshot of the CA activity for each species:
What patterns can we identify from these data?
(1) Taxonomy and phylogeny: Can patterns in CA activity be explained by taxonomy/relatedness? Many assume that physiology/metabolism is conserved within closely related species; i.e. members of the same genus are more likely to have similar physiological function compared to more distantly related species. I am still waiting for molecular IDs on many of the algae that I collected (since reds tend to be cryptic!) so that I can build an appropriate phylogenetic tree that enables me to directly test the influence of relatedness, but I can at least comment on discrete taxonomy (refined to the within-genus level). So far, it appears that taxonomy does not explain the patterns
(2) Epiphyte-host associations: What if ecological function/associations are considered instead of taxonomy? There appears to be a pattern; an average, epiphytes have significantly higher CA activity than both host algae and other species within their sister species (within in the same genus in all cases except one). Hosts have significantly lower CA activity than their sister species.
(3) Morphological complexity / branching density: Macroalgae can also utilize external CA (eCA), which is CA that is located at the interface between the bulk seawater and the surface of algal tissue, allowing for the conversion of HCO3- to CO2 before carbon uptake. It appears that activity of eCA is positively correlated with the branching density of the species, that is to say, that species with higher branching density are more likely to have higher eCA activity. Why? There are two reasons that I consider most likely. First, a purely physical driver: branching density often increases the thickness of the diffusion boundary layer surrounding the algal individual (due to turbulence), higher branching density might reduce the risk that eCA is "swept away" as water flows past. Second, a mix of physical & chemical drivers: research by Cornwall et al. 2013 suggests that because pH at the surface of the algae is high under slow flow, CO2 would be reduced but instead HCO3- increased because of the equilibrium 'rules' between CO2 and HCO3- under high pH. So, its possible that highly branched algae have higher eCA activity because the theoretical thicker boundary layers around their thallus are likely to have more HCO3- than CO2 compared to algae with inherently thinner boundary layers under the same flow (like expected for less complex algae).
This work was recently shared at the annual meeting for the Western Society of Naturalists in Monterey, California! You can download the Powerpoint for the oral presentation, if you're excited enough. :)
The British Phycological Society announced that I was selected as the winner of the Hilda Canter-Lund photography award for 2016; rad! You can read more about the background of the photo by following this link:
In July and August 2016, I will be running two lab-based experiments. For one of them, I want to put 1-3 species of brown macroalgae in the flume tanks owned and operated by the Martone Lab at UBC but first needed to be sure that the algae are 'happy' in the flumes, as closed systems, for a period of 7-10 days. There are many ways to determine the health and happiness of macroalgae; for this trial, I was interested in monitoring their photosynthetic yield (Y), their change in biomass, and biomechanical tissue properties (e.g. modulus, toughness, strain).
Seven macroalgal species were collected: Pleurophycus gardneri, Agarum fimbriatum, Costaria costata, Egregia menziesii, Nereocystis leutkeana, Saccharina groenlandica, and Saccharina latissima. These were placed in two flumes set at two water velocities: 0.1 m per second and 0.6 m per second.
The macroalgae were left in the tanks for 10 days, after which the final biomass and PAM readings (photosynthetic yield) were re-measured. I also attempted to determine the biomechanical properties of the tissues but their were technical difficulties and the Instron ultimately ate the tissues without producing reliable results! While all algae had relatively high photosynthetic yields at the beginning and end of the trial (good!), some algae were thrashed in the high flow tank. The latter was not a surprise because the species that faired poorly are typically found in low flow environments.
Figure 2. The change in biomass for each species that was tested, represented as relative growth rates (RGR per day). Pleurophycus, Agarum, and Costaria are typically found in environments with lower flow, which is reflected by the loss or low accumulation of biomass in the fast flow treatment -- interestingly these had the highest biomass RGR in the slow flow treatments. The Saccharina species seem to love life in the flume!
As the name implies, NWASS is a platform for algae and seagrass aficionados in the PNW to get together and share their current research and/or ideas about research in their field(s). I’m clearly an algal nerd but also a closet seagrass lover so this event was my jam. The symposium typically draws around 50-70 people and is ran over 2-3 days, and this year NWASS was held at Camp Casey on Whidbey Island, WA during 6-8 May. This year’s conference was characterized by a biofuels workshop, which helped draw attention from an NSF funding body and they provided enough funds to waive all fees associated with the symposium (excluding travel costs). Amazing, and thanks NSF!
The Martone Lab contributed a significant number to the total body present; we had 10 people from our lab and there were about 45-50 that attended. Daaang. Laura Borden, Kyra Janot, Tiffany Stephens (me), Patrick Martone, and Sam Starko delivered talks; Lauran Liggan, Liam Coleman, Cassandra Jensen, and Gwen Griffiths presented their research in poster form. Allison Dennert provided support. As a lab, we swept the awards! Laura + Kyra were awarded 1st and 2nd best talks, respectively, and Lauran + Gwen were awarded 1st and 2nd best posters, respectively. Excellent job, ladies!
Scott Edmundson of Pacific Northwest National Laboratory opened the conference, sharing an overview of algal biofuel research at his facility. Although the facility is located on the often rainy and cloudy peninsula of WA Sate (in Sequim), their equipment allows them to mimic the climatic conditions of other geographical locations so that they can predict microalgal productivity using outdoor culture tanks in that specific climate on any given day – for example, Phoenix, AZ on 29 Feb 1996. I was particularly attracted to the lighting system, where overhead light apparatus included thousands of small bulbs that emit different light qualities + wavelengths, and each of these collective types of bulbs can be independently programmed to control for the intensity of one quality of light versus another. Verrry niiice.
The following day was filled with 15 min oral presentations, starting with seagrasses, then macroalgae, then biofuels. It was fantastic to be able to learn more about what those in my geographical region and academic field are getting up to these days. To my surprise, I hardly knew anyone! I had lived in Seattle and on San Juan Island for years during my undergraduate studies at the University of Washington – and was quite active in the algal + seagrass community during that time – but very cool to meet new people in my field.
Robin Kodner delivered a stimulating talk about the spatiotemporal patterns in microbiont (algae and bacteria) community structure in Bellingham Bay, relating it to zones of hypoxia. This was very cool and, really, her research and methods are applicable to pretty much any body of water. It elucidated that we don’t know very much about these communities but by using advanced molecular tools (i.e. environmental genomics and metagenomics) we can determine which tiny critters are contributing to community diversity and structure without needing to visually identify them. The aspect of her talk that I got really jazzed about was how these methods helped identify that there is a big shift in community structure between spring and late summer, where phytoplankton are important drivers of community structure in the spring and bacteria are important drivers in late summer.
NWASS organized a beach walk on Sunday to take advantage of the low tides, unfortunately the only people to show up were the Martone Lab and two other symposium attendees! It seems that others might have had personal collections relevant to their research scheduled at other shores – fair enough. Heaps of lovely algae were present. We found some kind of parasite or growth response to an invading fungus on one thallus of Osmundia pinnatifida. There was plenty of Stephanocytsis geminata, a personal favorite, and we all discussed the finer points between Saccharina latissima and Saccharina groenlandica.
Looking forward to next year…only that I was wrangled into organizing it! Thanks to Rob Fitch and Tim Nelson for their hard work with the 2016 symposium.
On 1 April, I began working as a postdoctoral fellow at the University of British Columbia, an exciting next step. I joined the Martone Lab (of the Patrick variety) and was very excited to meet everyone involved. Plenty of algal research happening! Last week I found Stephanocystis geminata (previously known as Cystoseira) and have been searching for a heathy, small population over the past two years -- however sporadically! Hopefully I can soon follow through with an experiment also involving Sargassum muticum. I'll keep you updated.
The fate of photons absorbed by phytoplankton in the global ocean
Published online here.
Phytoplankton, which serve as an important food source in the ocean, use photosynthesis to turn sunlight into cellular fuel. This study reports that nearly twice as much of the sunlight energy captured by phytoplankton in the ocean is released as heat than is used to make food. The finding suggests that phytoplankton don't photosynthesize as efficiently as researchers had thought.
While 35% of the absorbed light was used for making food to fuel the phytoplankton’s growth, nearly 60% of the light was converted to heat. In laboratory studies with nutrient conditions encouraging phytoplankton growth, the team observed the opposite result: Around 65% of absorbed light was used to make cellular fuel, while less than 35% was lost as heat. The team blames phytoplankton’s inefficient photosynthesis in the ocean on nutrient-poor waters, which cover 30% of the world’s oceans. Without sufficient nutrients, the photosynthesis structures in phytoplankton don’t work properly and struggle to efficiently convert sunlight into usable energy.