Heads up, some pictures related to this blog and our week are posted in the “photos” tab, check ‘em out!
Another week in the books here at TFS and as you may have guessed, it was filled with plenty of adventures. We began this week by collecting samples from each of the Fog lakes for stable isotope analysis. Stable isotopes (in our case 13Carbon and 15Nitrogen) are a great tool for ecologists and provide insightful information about the structure of the food web. Basically, it is a fancy way to see who eats what. For a brief and quick overview, these carbon and nitrogen isotopes regularly occur in nature (plants, microbes, animals, etc.) but in relatively low concentrations. Because you are what you eat, as you move higher up the food web towards top predators, the organisms occupying higher trophic levels have higher amounts of these carbon and nitrogen isotopes incorporated into their tissues compared to their prey (they obtained the isotopes from ingesting multiple prey items). Variations in isotope ratios and the relative amounts of these isotopes within a given organism make up its unique isotope signature. The difference in isotopic signatures between organisms is predictable based on trophic level/what they eat and thus the trophic status of an organism (producer, consumer, top predator, etc.) can be determined using stable isotope analysis (whether they have more or less 13C and 15N). These analyses will be useful in determining the sources and links in the food webs of the Fog lakes and how they may change overtime (season to season and/or year to year), in response to changes in the environment, like warmer temperatures. With this stable isotope sampling our goal was to collect specimens from each level of the food web. This included epilimnetic (top water column) phytoplankton and primary producers using an integrated tube sampler throughout the photic zone (where there is enough light available for photosynthesis) lowered to the top of the thermocline. This water is then filtered onto a small filter back in lab and will be analyzed back in Utah. We also scraped benthic algae from some rocks and filtered it in a similar fashion. We collected benthic bugs (snails, caddisflies, and chironomids) from these rocks as well. Zooplankton were collected via horizontal net tows from the water column, which was arguably my most favorite part of this sampling. These zooplankton samples were taken back to lab and sorted under a microscope, check out the photos in “photos” tab that I captured with my phone through the eyepiece to see why I have such a passion for these little zooplankters! Fog 2 and Fog 3 had very similar zooplankton assemblages with the common cladoceran, Daphnia middendorffiana/longiremis making up most of the biomass followed by some awesome bright-red calanoid copepods (diaptomus pribilofensis), and smaller cladocerans (Bosmina longirostris) with a few large predacious calanoids (Heterocope septentrionalis) and water mites. Fun fact, the bright red color of the Diaptomus is from carotenoid pigments and is used for photoprotection. This causes an interesting tradeoff to arise, be bright red and easier to be spotted by visually foraging fish or be protected from the harmful UV rays of the sun, quite the decision for this little zooplankter. In contrast to Fog 2 & 3, the samples from Fog 5 were overwhelmingly dominated by the large predacious Heterocope, which feeds on these other smaller zooplankton and therefore occupies a higher trophic position comparably. Finally, Fog 1 had many more water mites than the other lakes. The presence of the species listed above seemed to be similar between the lakes, but the proportions of these species differed vastly. Naturally, this gets me asking…Why? Is this just random chance, or is there ecological reasoning to explain these differences? These zooplankton assemblages and benthic bugs typically change season-to-season as well as year-to-year, which is certainly something we are interested in tracking and the fish are interested in eating. As for the fish, during our standard fish sampling we take fin clips that are later analyzed for stable isotopes. As you can see, this sampling encompasses all of the pieces of the food web (at least the pieces that we know of!) which will provide us with insightful information regarding the food web structure of these lakes and how they may change overtime and in response to a changing climate. While out at the Fog lakes, we also downloaded our temperature and dissolved oxygen data from the loggers. This data gave us an idea of the thermal structure in each of our lakes over the past week and a half. It has been a warm few weeks here with regular highs in the 70’s (I thought we were in the Arctic!?). In Fog 1, we saw a rise in surface temperatures from ~14.5°C to almost 18°C in just a week and a half. This temperature was relatively constant down to about 4m where the temperature dropped about 4°C over a very short range (0.5-1m). Despite large changes in the surface temperatures, we saw very little change in the temperature of the bottom waters with the bottom 7m+ of water staying just above 4°C. This area of large temperature change over a short vertical distance around 4m deep is called the thermocline. The thermocline develops in lakes due to the difference in densities between cold and warm water and lack of mixing. This difference in densities further prevents mixing of the warm, top layer water (the epilimnion) and cold, bottom waters (hypolimnion), with the “dividing line” being the thermocline (or metalimnion), resulting in thermal stratification. Stratification may or may not develop within any given lake and is dependent upon season, temperature, mixing regimes, lake depth, and morphometry. Thus, if the water does not mix, the things in the water do not mix either, this includes all things like small organisms, nutrients, and dissolved oxygen. As you could imagine, stratification can lead to all sorts of interesting and intriguing dynamics in the water column that can affect all of its inhabitants. As for the rest of the Fogs, we saw a very similar thermal pattern as explained in Fog 1 above with surface temperatures approaching 18°C (very warm for these systems!) and the thermocline developing around 4m deep. We shall see how the thermal structures of the Fogs change in response to our warming manipulations; hopefully we see some measurable effects, i.e., warmer temperatures so we are able to gauge the responses of these lakes to a changing climate. In addition to the fun outlined above, we took more sediment cores with Kristen from Fog 5 using a pole corer from about 3m deep. As past coring, these cores will be incubated with certain light regimes in order to calculate primary production and respiration form the sediments. We also slung the large platforms that will be used to house the warming equipment to Fog 1 and Fog 5 (the warmed lakes). The slinging was accomplished by the helicopter and its great pilot, which made a nearly impossible feat, possible in a matter of minutes. Slinging via helicopters will be a regular occurrence throughout the warming project. To wrap up the week my REU and I did some fishing for the ARC-LTER site on lakes E5 (experimentally fertilized lake) and I-6 on the inlet series to Toolik. As for this upcoming week, big plans are in store and I couldn’t be more excited! Monday we plan to get down and dirty with more sediment coring from Fog 2 & 3. Then Tuesday, the moment we have been waiting for…when more members of the lake warming crew arrive, including Phaedra Budy (lead PI and my advisor), Gary T., Peter M., Sarah N., and Thomas B. For the remainder of the week we plan to set up the warming equipment and initiate the warming of Fog 1 and Fog 5. The next 2 weeks in particular will be filled with a lot of hard work and planning from all those involved, but there is no doubt that the entire team is both excited and anxious to get this underway! Thanks for tuning in to another one of my blog posts and as always feel free to comment/contact me with questions, concerns, or just to chat! Until next time, take care.
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2/27/2021 11:07:47 pm
Keiken Engineering fabricates the customization options for water treatment pilot plants to help take advantage of the treatment processes, which include Nanofiltration, Reverse Osmosis, Microfiltration, as well as Ultrafiltration.
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Nick Barrett- PhD student on Arctic Lake Warming project Check out my personal Twitter page for various tweets about the project: @WaterWorks_NB |