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Transport of bioavailable organic carbon into the Baltic Sea

Jones, Kevin (2020) BIOM02 20201
Degree Projects in Biology
Abstract
The transport of terrestrial carbon through riverine systems to coastal water may have a negative impact on the oxygen concentration. However, information on seasonal variation and the impact of composition of the catchment area on bioavailability is lacking. This paper covers the January and April samplings, which are a part of a yearlong study. To examine the seasonal variation in composition and bioavailability of dissolved organic carbon (DOC) we sampled 9 river mouths that lead to the Baltic Sea. We utilized an oxygen sensing system that measured change in oxygen over a 13-day period. Based on oxygen consumption we were able to calculate the bioavailable fraction of carbon and carbon utilization rates. Both the bioavailable fraction... (More)
The transport of terrestrial carbon through riverine systems to coastal water may have a negative impact on the oxygen concentration. However, information on seasonal variation and the impact of composition of the catchment area on bioavailability is lacking. This paper covers the January and April samplings, which are a part of a yearlong study. To examine the seasonal variation in composition and bioavailability of dissolved organic carbon (DOC) we sampled 9 river mouths that lead to the Baltic Sea. We utilized an oxygen sensing system that measured change in oxygen over a 13-day period. Based on oxygen consumption we were able to calculate the bioavailable fraction of carbon and carbon utilization rates. Both the bioavailable fraction and the carbon utilization rates were significantly higher in April compared to January. Carbon composition was determined using absorbance and land cover was collected from databases. Using linear regression, we investigated how land cover and environmental variables may influence the bioavailable fraction of carbon and carbon utilization rates. In January variables that were significantly explaining bioavailable fraction were, PO4, temperature, pH, conductivity, DOC and the absorbance ratios for aromaticity, carbon origin, and humic content. In April we found that total nitrogen, pH, conductivity, DOC, watercolor, and the absorbance ratios for carbon size, aromaticity, and humic content were significant variables. When the carbon utilization rate was examined, in both January and April, the only significant variable was watercolor, which is usually an indicator of terrestrial DOC. However, during winter and spring, when bioavailability is low, watercolor is also related to DOC concentration and more DOC content results in greater utilization. Last we examined wetlands as a possible management effort, being able to lower the amount of carbon that is being transported through riverine systems. It was found that wetlands have an ability to lower watercolor and the bioavailability of the carbon if the water residence time (WRT) is long enough to allow for sequestration. (Less)
Popular Abstract
Transport of bioavailable organic carbon into the Baltic Sea

The Baltic Sea has been one of the most polluted bodies of water on earth, suffering from eutrophication and oxygen poor conditions (anoxia) due to severe excess of nutrient inflow. There have been extreme management efforts in the Scandinavian countries to help lower the nutrient input of phosphorus and nitrogen. However, recent science suggest that excess carbon could be to blame for these anoxic conditions and no longer phosphorus and nitrogen. Consumption of carbon by microorganisms requires oxygen and can therefore cause anoxia. This is a vital issue to address because the low oxygen causes mass die offs of key aquatic life which in turn affects businesses that help bring... (More)
Transport of bioavailable organic carbon into the Baltic Sea

The Baltic Sea has been one of the most polluted bodies of water on earth, suffering from eutrophication and oxygen poor conditions (anoxia) due to severe excess of nutrient inflow. There have been extreme management efforts in the Scandinavian countries to help lower the nutrient input of phosphorus and nitrogen. However, recent science suggest that excess carbon could be to blame for these anoxic conditions and no longer phosphorus and nitrogen. Consumption of carbon by microorganisms requires oxygen and can therefore cause anoxia. This is a vital issue to address because the low oxygen causes mass die offs of key aquatic life which in turn affects businesses that help bring money and food to a global market.

In this study we examined the biological degradation of carbon (bioavailability of carbon) in river mouths of 9 rivers draining into the Baltic Sea. These 9 rivers varied in catchment compositions (% of farmland, urban, forest, and wetland that surround the rivers) and were studied during different seasons. This experiment involved measuring how much of the carbon and how fast the carbon from collected water samples was degraded by bacteria. Those results were then compared to the catchment compositions and the composition of the carbon (based on absorbance measurements) to check for correlations. This would allow us to find a quick identifier for bioavailable hotspots of carbon.

The results show a trend with the carbon becoming more bioavailable from January to April. The amount of carbon that was degraded was related to the carbon composition and nutrient concentrations. In contrast, watercolor was the main variable responsible for explaining how fast the carbon was degraded. These two results taken together show that most carbon is utilized in rivers with high carbon concentrations. Therefore, rivers with darker water, having a lower fraction of bioavailable carbon but higher degradation rates, are more susceptible to causing anoxia and should be a focus of maintenance.

A potential management effort that we investigated is the creation of wetlands to lower the watercolor, as well as the bioavailable carbon. Increasing the water residence time (how long water stays in a system) gives more time for degradation by UV-light and bacteria. There needs to be more research into the application of these wetlands, but it seems that if they are constructed correctly, the wetlands could help lower the amount of carbon that ends up in the Baltic Sea. Water quality would improve, thereby increasing the health of the whole system and the organisms living in it.

Master´s Degree Project in Biology, 30 credits 2020
Department of Biology, Lund University

Advisor: Johanna Sjöstedt
Aquatic ecology (Less)
Please use this url to cite or link to this publication:
author
Jones, Kevin
supervisor
organization
course
BIOM02 20201
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9020177
date added to LUP
2020-06-18 12:37:04
date last changed
2020-06-18 12:37:04
@misc{9020177,
  abstract     = {The transport of terrestrial carbon through riverine systems to coastal water may have a negative impact on the oxygen concentration. However, information on seasonal variation and the impact of composition of the catchment area on bioavailability is lacking. This paper covers the January and April samplings, which are a part of a yearlong study. To examine the seasonal variation in composition and bioavailability of dissolved organic carbon (DOC) we sampled 9 river mouths that lead to the Baltic Sea. We utilized an oxygen sensing system that measured change in oxygen over a 13-day period. Based on oxygen consumption we were able to calculate the bioavailable fraction of carbon and carbon utilization rates. Both the bioavailable fraction and the carbon utilization rates were significantly higher in April compared to January. Carbon composition was determined using absorbance and land cover was collected from databases. Using linear regression, we investigated how land cover and environmental variables may influence the bioavailable fraction of carbon and carbon utilization rates. In January variables that were significantly explaining bioavailable fraction were, PO4, temperature, pH, conductivity, DOC and the absorbance ratios for aromaticity, carbon origin, and humic content. In April we found that total nitrogen, pH, conductivity, DOC, watercolor, and the absorbance ratios for carbon size, aromaticity, and humic content were significant variables. When the carbon utilization rate was examined, in both January and April, the only significant variable was watercolor, which is usually an indicator of terrestrial DOC. However, during winter and spring, when bioavailability is low, watercolor is also related to DOC concentration and more DOC content results in greater utilization. Last we examined wetlands as a possible management effort, being able to lower the amount of carbon that is being transported through riverine systems. It was found that wetlands have an ability to lower watercolor and the bioavailability of the carbon if the water residence time (WRT) is long enough to allow for sequestration.},
  author       = {Jones, Kevin},
  language     = {eng},
  note         = {Student Paper},
  title        = {Transport of bioavailable organic carbon into the Baltic Sea},
  year         = {2020},
}