It was fascinating to study the lakes the Suwalki region (Wigry National Park and the Suwalki Landscape Park), as the changes that have occurred here are due exclusively to climate change and the changes in the composition of flora and fauna in the region. This is the least populated region of Poland and the landscape was shaped by the Pleistocene Ice Age. The changes in the life cycles of the lakes are not tied to pollution or direct human impact through runoff or drawing down groundwater levels, unlike in other parts of the country and around the world. Claudocera (shown above) are “one of the most important biological indicators for environmental variables.” They are also quite sensitive to changes in the PH of water bodies. (Edyta Zawisza, Izabela Zawiska, and Alexander Correa-Metrio,“Cladocera Community Composition as a Function of Physicochemical and Morphological Parameters of Dystrophic Lakes in NE Poland,” Wetlands, vol 36, issue 6, December 2016 pp 1131-1142.) The species composition of Cladocera in Lake Suchar IV indicate that this lake is extremely dystrophic, or disharmonic. According to scientists, the lake’s shift from harmonic to disharmonic occurred during the Late Glacial and the Holocene ages and was caused by changes in the climate and the quality of the drainage basin. (https://www.limnetica.com/documentos/limnetica/limnetica-38-1-p-391.pdf)
The dystrophic lakes in this region are surrounded by pine-spruce forests such as those found in Scandinavia. The name “suchary”" means “poor at life.” In fact these lakes are characterized by few nutrients, a low PH (acidic) and a high humus content (humus is organic material created by the decomposition of leaves or in this case by peat mosses known as sphagnum). These lakes are characterized by high levels of organic acids and low visibility, and conductivity (this means they are poor at transmitting electricity). They also have a high oxygen demand and follow the Eutrophic (nutrient and phosphate rich) Phase in the life cycle of a lake. These types of naturally created dystrophic lakes are very unusual and are protected. In Scandinavia, Poland, Russia, and Canada the lake sediments portray an “environmental history that is almost entirely attributable to natural variability.” Lake Suchar IV, one of the lakes we sampled, has one of the highest distrophy indexes for the area and extremely high total organic carbon. The water is very dark brown and sunlight is unable to penetrate much below the surface. The lake is characterized by algae, cladoceran species that inhabit dystrophic lakes, and a proliferation of floating sphagnum mats. The sphagnum in the photo above illustrates how its long stringy structure allows it to hold water and absorb sunlight, so it can survive in environments that would be hostile to other aquatic plants.
Cladoceran species also exist in water where light does not penetrate to the bottom, so it was no surprise that we collected many of them while water sampling in the dsystrophic lakes in Wigry National Park. Cladoceran filter feed on small particles while attached to the surface film of the water. They also ingest phytoplankton (microscopic algae) that are the foundation of the aquatic food web, as well as bacteria. These water fleas are in turn eaten by damselfly larvae and aquatic beetles. There is so much I want to learn about how these microscopic creatures function within ecosystems and what they can tell us about water quality by the functioning of their cells or which types are present.
The image below is of micrasterias americana, a type of green algae. It is the energy base of the food web for all aquatic organisms. Algae are important because through photosynthesis they convert water and carbon dioxide into sugar. Micrasterias Americana is a member of the Desmidiaceae family, and is found in peat bogs around from tropic to polar regions. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4940373/) They are excellent indicators of environmental stressors. What is especially fascinating about this type of algae is that when conditions become unfavorable for its survival, some of the cells will undergo PCD or planned cell death, so that the rest of the colony can survive. (Peat bogs are often shallow and the algae that grows in them is exposed to higher solar radiation and increased temperatures, which can lead to large numbers of cells dying off so the population as a whole will survive. ) When the algae die, they consume even more oxygen making it impossible for aquatic life to survive. When algae decompose, they also can release toxins. Understanding algae is becoming increasingly critical, since many lakes around the world are experiencing large algae blooms which release toxins that kill zooplankton and the creatures that feed on them or those that come into direct contact with these blooms in the water. The lakes in Wigry National Park went from harmonic to dystrophic due to climate changes, warmer temperatures, and changing flora and fauna in a natural ecological evolution. This suggests that as temperatures warm, algae across the planet will proliferate even if waterbodies were not subject to nitrogen and phosphate pollution as is often the case. Toxins will also be released in greater quantities, and these toxins will be ingested by zooplankton and up through the food chain, impacting all creatures and human health.
The image bellows of Spirogyra with zygotes. Spirogyra and other zygnemids from stringy masses of filaments. They grow by mitosis, which is the process of filaments breaking off and forming new filaments, which means they can form a bloom or scum in mere days since they can reproduce so quickly. (https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/closterium) We saw this with some water samples we collected and let sit. This way of reproducing is asexual. However, under adverse conditions, spirogyra can also reproduce sexually. Protoplasts move though the conjugation tube and fuse with the protoplast of another to form a zygote, which develops a thick protective wall so the zygote can lie dormant until conditions are right. The image below illustrates this and also suggests why it is so difficult to rid the water of algae once a bloom starts.
Cladoceran can also survive in adverse conditions due to their own adaptive strategies. The image below shows cladoceran eggs that are encased with protective membranes. Though they can reproduce asexually, under adverse conditions some females can produce haploid eggs that need fertilization by males. These eggs can remain dormant for decades before hatching. fertilized eggs remain in a dormant state being enclosed by several protective membranes, the ephippium, and can survive strict conditions for many decades before hatching [5-7]. (https://www.omicsonline.org/open-access/how-daphnia-cladocera-assays-may-be-used-as-bioindicators-of-health-effects-2332-2543-S1-005.php?aid=63936
If dissolved oxygen falls below 3 ppm, cladoceran and other aquatic animals are stressed and may not survive. Fish kills occur when levels fall below 2 ppm, in lakes where fish live. (http://www.cotf.edu/ete/modules/waterq3/WQassess3f.html) The lakes in this region provide evidence that climate change has historically altered the make-up of aquatic ecosystems. Many waterways around the world have become highly eutrophic, as an abundance of phosphates and nutrients have washed into them and algae have begun taking over native aquatic vegetation. Studying the lakes in Northeast Poland has much to teach us about what is happening as our waterways are being impacted by both climate change and pollution, and what might happen to our water quality next.
The image below is of moss opening and when I saw it come into view, it immediately made me feel the fragility of life. It also made me want to learn as much as I can about what is happening to our aquatic ecosystems on a microscopic level, because algae, bacteria, cladoceran, rotifers, and other phytoplankton and zooplankton are the building blocks for all existence. If they become toxic, so does the rest of the food chain. Yet, their behavior and adaptive strategies may also contain clues for how we can solve some of the pressing survival issues we face.
I was very fortunate to have been instructed by biologist and photographer Marek Mis while I was in Poland and hope to return again next year to continue learning from him about this pristine region and aquatic systems. In the meantime, I have acquired my own microscope and am getting ready to embark on water quality testing in the Blue Ridge region where I live. It is a whole other world when you look through the eyepiece, but at the same time what you see is the foundation of all we observe with the naked eye. It has already added such a richness to my understanding of aquatic systems and life itself.