Month: December 2022

How Ancient Ocean Chemistry Might Have Increased Complexity of Life

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Ediacaran Reorganization of the Marine Phosphorus Cycle 

Thomas A. Laaksoa, Erik A. Sperling, David T. Johnstona, and Andrew H. Knoll

Summarized by Makayla Palm

What data were used? The purpose of this study was to measure if changes in the phosphorus cycle were linked to changes in the chemical composition of ocean water hundreds of millions of years ago. The phosphorus cycle is the study of the element phosphorus as it travels from deep-sea storage and rock formations into organic life, and back to the seas again. Why study phosphorus in the first place? Phosphorus is essential to life because it is an important component in DNA and RNA structure. Specifically, at the end of the Ediacaran (~625–542 million years ago or mya), there was a jump in complexity in the fossil record (i.e., life became more complex) found in the transition from the Ediacaran to the Cambrian (~542–485 mya); it may be the case that this change in phosphorus can help us understand the changes to life on Earth during this time. Previously collected phosphorite samples (rocks with a high phosphorus content) and newly found samples from the Doushantuo Formation (Ediacaran, China) were used in this study. These phosphorite samples were examined for the following: evaporite volume, strontium isotope ratios, and content of phosphate. Changes in these samples’ ratios and concentrations allow researchers to hypothesize the impacts on water and life during the Ediacaran. Originally, scientists thought the changes may have been due to increased weathering of rocks, but researchers in this study hypothesized that there may have been more to the story. 

Methods: Researchers from this study hypothesized that a change within deeper Ediacaran ocean chemistry may be the cause for the phosphorus cycle change. They tested this hypothesis by using the variables collected (e.g., isotopes) in an equation that measures the possible effects of the phosphorus evaporite remineralizing into phosphorite (typically how phosphorus is stored in the ocean) This equation measures the amount of phosphorus taken out of the storage bank by measuring the fraction of total organic phosphorus that is removed in relation to the amount of phosphorus that reverts back to its original form in the storage bank. 

Results: The changes in ocean chemistry can be found on the atomic scale, where there are electron acceptors (also known as oxidizers) and electron donors (or reducers). The ocean, having been in a state of consistent reducing reactions, may have shifted to have more oxidizers, which would have increased remineralization – specifically, phosphorus remineralization. This remineralization would explain the difference that eventually modified the Ediacaran phosphorus cycle to the modern-day phosphorus cycle. In order for phosphorus to reduce, something needs to accept its electron. In the absence of oxygen (which early Earth was lacking in for billions of years), research indicates sulfate may be a suitable candidate. Samples of sediment did not indicate a change in phosphorus content, so the hypothesis was not supported. This means that the phosphorus was likely staying within the same system and being removed. The phosphorus cycle, similar to the water cycle or carbon cycle, describes the formation, use and recycling of phosphorus from the oceans, to land, and back to the ocean. The data from this study indicate that upwelling, the mixing of nutrients from the bottom of the ocean back to the top, is the reason for increased phosphorus. Upwelling can be caused by deep water currents coming into contact with continents, where cold, nutrient rich water is propelled closer to the surface and warms. The increased upwelling makes sense in the phosphorus cycle because of the extra circulation happening, which would explain the increased presence of phosphorus without an added source of the element. 

This figure represents three different kinds of information collected over the same period of time. The top graph is a bar graph that measures the amount of phosphate evaporite that was removed and not returned to the phosphorus storage bank. The middle bar graph measures the total amount of phosphate resources stored in the form of P2O5. This graph represents the amount in millions of tons. The line graph at the bottom of the figure represents the number of strontium isotopes found within the rock samples. This graph represents inconsistent intervals of small increasing and decreasing values, showing an overall increase through time in each graph. Across all three graphs, columns highlight the appearance of phytoplankton and large animals within the fossil record. The appearance of phytoplankton is approximately 700 million years ago, and the appearance of larger animals is around 720-699 million years ago. The appearance of both is marked by horizontal black bars at the bottom; with each appearance, there is an uptick in strontium 87. More complex life is marked by more phosphate and evaporites. These bars represent the appearance of organisms in all three line graphs.
The figure represents the three different kinds of data discussed in the paper. The top demonstrates the volume ( km cubed) of phosphorite evaporite, with a general trend of increasing evaporite over time.The middle graph represents the amount of phosphate resources stored in the “storage bank” in the ocean (in millions of tons). The bottom graph represents the change in Strontium isotopes, with ebb and flow in value over time, with a general trend that after a strong dip ~ 700 million years, trends upward. Ice ages are indicated with gray vertical bars across all three graphs, indicating a change in ecosystem. The dark horizontal bars at the bottom of the figure indicate when the appearance of phytoplankton and macroscopic animals occur, which is ~ 680 million years for the phytoplankton and ~ 650 million years for the macroscopic animals. The vertical gray shading represents Ice Ages that occurred in the timeline measured on the figure. The figure as a whole points to the correlation of increased phosphorite levels and the first appearance of relatively large animals in the fossil record.

Why is this study important? This study aims to see why the change in phosphorus occurred to better understand the geologic context that precedes a big change in the fossil record. There is a large jump in complexity from Ediacaran to Cambrian organisms, and ocean chemistry (changes in phosphorus levels in this case) may have had something to do with that. The cycling of phosphorus because of upwelling, influenced by continental placement, could have been a driving reason behind these big changes, ecological and evolutionary. 

Big Picture. This study proposes a mechanism for the change in the phosphorus cycle that is observed between the phosphorus cycle today and the phosphorus cycle of the Ediacaran as we know it. Many questions still exist as to how oceans have changed through geologic time and this study provides an important piece to the puzzle. Understanding changes in ocean chemistry, too, better helps scientists understand how life evolves in response. 

Citation: Laakso, Thomas A., et al. “Ediacaran Reorganization of the Marine Phosphorus Cycle.” Proceedings of the National Academy of Sciences, vol. 117, no. 22, 2020, pp. 11961–11967., https://doi.org/10.1073/pnas.1916738117. 

Early childhood and connecting with nature

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Effect of environmental education on the knowledge of aquatic ecosystems and reconnection with nature in early childhood

Maria João Feio, Ana Isabel Mantas, Sónia R. Q. Serra, Ana Raquel Calapez, Salomé F. P. Almeida, Manuela C. Sales, Mário Montenegro, Francisca Moreira

Summarized by Habiba Rabiu, a student of environmental geosciences at Fort Hays State University. Habiba is interested in all aspects of environmental science and conservation & sustainability. She would like to work in educating others about those topics. In her free time, she likes to read, write, and bake.

What data were used? In 2018, the environmental educational project CresceRio was created in the city of Coimbra, Portugal, to encourage the populace to reconnect with nature, preserve and protect the streams found in the area, and teach children about the importance of the streams and preserving green and blue (terrestrial and aquatic) ecosystems. Most children who live in the city had little exposure to nature and expressed fear and incorrect knowledge about the streams and rivers in their area. It was proposed that introducing field trips to natural areas and hands-on activities to school curriculums would be a low cost yet effective way to improve their relationship with the natural world. 

Methods: Over the course of 14 months, the researchers conducted several surveys with a class of 24 students (aged 5–6 at the beginning of the program). At particular intervals (labeled M), the children were questioned about five main topics: their identification and background, their awareness of streams and rivers, their recognition of the biodiversity that existed in the rivers, their awareness of various factors negatively affecting the rivers, and their awareness of the ecosystem services provided by rivers to the population. 

M1 occurred at the beginning of the program (September 2018) and was followed the next month by a trip to a stream outside of the city that was not seriously affected by urban activity. M2 occurred in November 2018, and the students visited an urban stream that was visibly affected by urban activity including construction, removal of trees, and litter. In February 2019, the students participated in a laboratory class where they examined fallen leaves and were taught to identify various invertebrates and algae using microscopes. M3 took place in March 2019, followed by a workshop in June 2019 where they reviewed photos and videos and discussed what they learned from their previous activities. In October 2019 they visited another urban stream that was slightly less altered than the one they visited before. The last survey was conducted in November 2019 and was done in the form of group interviews. 

Results: The three main takeaways that the researchers identified were 1) that children in urban areas have little contact with or knowledge of nature, 2) after a year of exploring the streams and their ecosystems their knowledge increased (both about the ecosystems and the problems they face) and their fears decreased, and 3) the long duration of the program was key as changes in their attitude and knowledge only became clear after a few activities.

In all five categories explored (personal background and experience, awareness of aquatic ecosystems, recognition of biodiversity, awareness of issues affecting rivers, and awareness of services provided by rivers) the students showed increased interest and cognizance of the streams by the end of the program. Students were more aware of the streams close to where they live as well as the animals (other than fish) that lived there, such as birds and insects. The activities and field trips lessened their fears of imaginary creatures or animals like alligators that did not exist in Portuguese rivers and made them more appreciative of the streams as a resource for water and recreation. They also acknowledged the presence of trees on the banks of the streams that provided oxygen, shelter, and food for animals. The children also showed an increased negativity for litter, lack of trees, too many reeds (that grow unchecked when trees are removed and choke the stream) and too many buildings around the streams. The students were also reported as saying that they would not litter and would discourage others from doing so as well.

The bar graph shows 3 bars for each organism, showing the percentage of students that recognize that organism at the time of the M1, M2, and M3 surveys. Approximate values are: Fauna Fish: M1- 60%, M2- 92%, M3- 87% Invertebrates: M1- 30%, M2- 40%, M3- 75% Insects: M1- 42%, M2- 44%, M3- 33% Dragonflies: M1- 39%, M2- 50%, M3- 68% Butterflies: M1- 30%, M2- 25%, M3- 22% Mosquitoes: M1- 48%, M2- 45%, M3- 38% Shrimps: M1- 60%, M2- 47%, M3- 53% Aquatic snails: M1- 25%, M2- 59%, M3- 30% Mammals: M1- 21%, M2- 19%, M3- 38% Amphibians: M1- 12%, M2- 22%, M3- 25% Birds: M1- 27%, M2- 37%, M3- 30% Aquatic flora Algae: M1- 60%, M2- 82%, M3- 97% Filamentous green algae: M1- 39%, M2- 45%, M3- 79% Aquatic plants: M1- 39%, M2- 63%, M3- 70% Trees Alders: M1- 23%, M2- 18%, M3- 38% Willows: M1- 17%, M2- 27%, M3- 62% Poplars: M1- 10%, M2- 40%, M3-70 % Oaks: M1- 21%, M2- 50%, M3- 70% Ash trees: M1- 17%, M2- 18%, M3- 37%
Figure 1: The percentage of students that can recognize particular flora or fauna over time and as they are more exposed to streams and the organisms that live there.

Why is this study important? Children growing up in urban areas are exposed to various pollutants and obstacles that come from living in the city. Being consistently exposed to nature from an early age can help to combat those negative effects and promote health and wellbeing. Additionally, learning about the importance of aquatic ecosystems naturally inspires children to be interested in conservation and sustainability. This study showed that when given the opportunity to have real experiences in nature, they form their own positive opinions and ideas.

The big picture: Conservation of green and blue ecosystems is dependent on future generations having genuine understanding of and connections to nature. Introducing environmental studies, complete with hands-on activities, to primary education curriculums is an effective way to nurture those connections. Children should be exposed to the natural spaces close to their schools and homes in order to feel connected to nature and have a deeper learning experience.

In the “before” images (a) and (b), the children drew pictures where only a small portion depicts the stream. A few fish are shown, but most of the detail shows the dock, land, buildings and trees, a large portion of sky, and in image (b) lots of people. In the “after” images (c) and (d), the children’s pictures show a large amount of water and a lot of biodiversity, with pictures of insects, snails, and birds.
Figure 2: Pictures drawn by students after their first field trip (a and b) and after their second field trip and laboratory class (c and d)

Citation: Feio MJ, Mantas AI, Serra SRQ, Calapez AR, Almeida SFP, et al. (2022) Effect of environmental education on the knowledge of aquatic ecosystems and reconnection with nature in early childhood. PLOS ONE 17(4): e0266776. https://doi.org/10.1371/journal.pone.0266776

Trees Combat Climate Change in China by Reducing CO2 Levels

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Forest management in southern China generates short term extensive carbon sequestration

By: Xiaowei Tong, Martin Brandt, Yuemin Yue, Philippe Ciais, Martin Rudbeck Jepsen, Josep Penuelas, Jean-Pierre Wigneron, Xiangming Xiao, Xiao-Peng Song, Stephanie Horion, Kjeld Rasmussen, Sassan Saatchi, Lei Fan, Kelin Wang, Bing Zhang, Zhengchao Chen, Yuhang Wang, Xiaojun Li and Rasmus Fensholt

Summarized by Anna Geldert

What data were used? Researchers collected data on carbon storage (long-term carbon stocks) and sequestration levels (new uptake of carbon gasses) by forest type. Data was recorded between 2002 and 2017, and the area of study focused on eight provinces in southern China. This data was compared with existing published data on soil moisture levels and national CO2 emissions.

Methods: Researchers used satellite imagery data from MODIS (Moderate Resolution Imaging Spectroradiometer) for the basis of this study. Using approximately 10,000 MODIS images, they divided the area into a grid with a scale of 0.25km2. Using “training points” of known land cover, they trained a computer to estimate the probability of forest cover in each grid cell, as well as the level of change in forest cover over time. Based on this information, grid cells were classified into eight categories of forest types, including dense forest (probability of forest cover ≥ 0.8, with low change), persistent forest (probability ≥ 0.5, with low change), persistent non-forest (probability ≤ 0.5, with low change), recovery (regrowth of deforested areas, causing a gradual shift from non-forest to forest), afforestation (tree plantation in previously unforested areas, causing a rapid shift from non-forest to forests), deforestation (shift from forest to non-forest), rotation (harvested area, causing fluctuation between forest and non-forest) and rotationL (harvested area, causing fluctuations and low forest recovery). Researchers then estimated the carbon density of each forest type using data from a previous study 2015 from GLAS (Geoscience Laser Altimeter System, i.e., a satellite machine designed to measure the vertical structure of forests). MODIS data from this study was cross-referenced with existing passive microwave data from SMOS (soil moisture and ocean salinity), which also measured carbon density from this region, though on a broader scale. SMOS data were also used to determine the average soil moisture in the studied region.

Results: Both tree cover and fossil fuel emissions increased considerably between 2002 and 2017. Using the MODIS data, researchers estimates a carbon sink of 0.11 Pg C year-1 (i.e., petagrams of carbon per year, the equivalent of 0.11 billion metric tons per year) in the region studied. This accounted for roughly 33% of yearly carbon emissions since the year 2012. Unmanaged dense forest had the highest carbon density, accounting for 20.5% of carbon storage despite only occupying 8.8% of the land. However, dense forests had low levels of carbon sequestration, accounting for only 4% of the total uptake. Comparatively, persistent non-forests and managed forests (recovering, afforestation, and rotation areas) all had low levels of carbon storage but accounted for 65% the total carbon sequestration. Persistent forest areas lay somewhere in the middle, with moderate storage and sequestration levels. Heavily harvested forests (deforested and rotationL areas) had much lower sequestration rates, and served as carbon sources rather than sinks. Finally, SMOS data revealed that soil moisture levels tended to be lower in regions with lots of managed forests.

The figure shows a bar graph comparing the type of land to the level of sequestration of CO2 emissions. The x-axis is labeled “Type of land use,” and is numbered 1 through 8. A legend on the right of the graph indicates that each number corresponds to a type of forest or non-forest area: 1 represents dense forest, 2 represents forest, 3 is non-forest, 4 is recovery, 5 is afforestation, 6 is deforestation, 7 is rotation, and 8 in rotationL. A different y-axis is present on either side of the graph, so that both the relative percent of CO2 emissions sequestered and the numerical quantity of carbon sequestered per year are represented. The left axis represents the percentages, and spans from 0 to 7.5, increasing at increments of 1.25. The right axis represents the quantity of carbon sequestered in petagrams per year, spanning from 0.00 to 0.03 and increasing by a factor of 0.05. A separate legend on the bottom of the graph indicates that the dark orange portions of the bars represent the percentage/fraction of carbon sequestered compared to CO2 emissions from China as a whole, while light orange portions correspond to emissions from the eight provinces alone. The land use type with the highest percentage of carbon sequestered was non-forest, which accounted for approximately 6.5% of annual emissions for the eight provinces, or 0.026 total Pg of carbon per year. Non-forest was followed by forest and afforestation (both accounting for 5.2% of emissions and 0.21 total Pg), recovery (4% and 0.016 Pg), rotation (3.5% and 0.013 Pg) and dense forest (1% and 0.009 Pg). Deforestation and rotationL were the only types of land use to represent a negative percentage and quantity of carbon sequestered, indicating that they served as a carbon source rather than a carbon sink. Deforestation accounted for approximately -0.2% (or 0.001 Pg) of carbon sequestration, while rotationL was nearly negligible. The percentages of carbon sequestered when compared to national emissions (dark orange) were all about one fifth of the percentages when compared to the eight provinces alone.
Fig. 1. Average percent of CO2 emissions sequestered annually by each forest type. CO2 emissions from the eight provinces in the study region, as well as emissions from China as a whole, are both shown.

Why is this study important? This study compares the effectiveness of different types of forests in mitigating the impacts of climate change. While natural, dense forests were the best at storing carbon long-term, managed forests were most effective at rapidly removing CO2 from the atmosphere on a shorter timescale. Harvested forests, especially those classified as “rotation,” were especially successful as they were able to sequester relatively high levels of carbon while still providing significant economic revenue from timber for the region. Overall, changes in forest management policies in China in 2002 led to an impressive reduction in carbon emission levels (33%). However, it is important to note that an additional 3 million km2 of forested land would be needed to reach net zero carbon emissions, a number which is unreachable in this region. Likewise, reduced levels of soil moisture indicate that heavily managed forests may not be sustainable in the long run, and will likely be less effective during periods of drought. More research is needed to determine if these forest management policies have already reached maximum effectiveness, or if other adjustments can be made to further increase sequestration.

The big picture: As the main drivers of climate change, fossil fuel emissions continue to threaten our planet. Forestation and forest management policies, such as those established in China at the turn of the century, are a way to mitigate the impact of greenhouse gasses. Modeling future policies after these could help increase carbon sequestration worldwide, especially until renewable energy becomes available. However, as was revealed in this study, it is nearly impossible at current emission levels to reach net zero carbon emissions through forest management alone; in the long term, forest management will likely need to be combined with other policies to ensure a sustainable future.

Citation: Tong, X., Brandt, M., Yue, Y., Ciais, P., Rudbeck Jepsen, M., Penuelas, J., … Fensholt, R. (2020). Forest management in southern China generates short term extensive carbon sequestration. Nature Communications, 11(1). https://doi.org/10.1038/s41467-019-13798-8