Absence of vertical migration across a halocline for the cyanobacteria Nodularia spumigena
(2024) MVEK12 20241Centre for Environmental and Climate Science (CEC)
- Abstract
- Algae blooms, induced by eutrophication, have been an increasingly prevalent
environmental concern in the Baltic Sea since the 1970s, causing ecosystem
degradation and hypoxia in bottom layers. One predominant harmful algae bloom-forming species in the Baltic Sea is the cyanobacteria Nodularia spumigena. N. spumigena produces hepatotoxin nodularin and is a diazotrophic alga; hence, it should be phosphorus-limited. However, looking at the large bloom masses N. spumigena can sustain in the Baltic Sea, this does not seem to be true. Furthermore, excess phosphorus is usually trapped below the halocline in the Baltic Sea. In this study, we conducted a laboratory experiment to investigate whether N. spumigena has the ability to migrate over... (More) - Algae blooms, induced by eutrophication, have been an increasingly prevalent
environmental concern in the Baltic Sea since the 1970s, causing ecosystem
degradation and hypoxia in bottom layers. One predominant harmful algae bloom-forming species in the Baltic Sea is the cyanobacteria Nodularia spumigena. N. spumigena produces hepatotoxin nodularin and is a diazotrophic alga; hence, it should be phosphorus-limited. However, looking at the large bloom masses N. spumigena can sustain in the Baltic Sea, this does not seem to be true. Furthermore, excess phosphorus is usually trapped below the halocline in the Baltic Sea. In this study, we conducted a laboratory experiment to investigate whether N. spumigena has the ability to migrate over a halocline. We also explored whether this migration was triggered by phosphate depletion above the halocline and evaluated the impact of phosphate addition on N. spumigena’s average chlorophyll concentration. The experiment was conducted in artificial water columns with two different phosphate concentrations above the halocline (phosphate-depleted and phosphate-enriched). Measurements of chlorophyll- and phosphate concentration at different depths were taken once during the day (10:00) and once during the night (22:00), over a 96-hour sampling period. The results showed no clear vertical migration of N. spumigena over the halocline at any
point during the 96-h sampling period. This pattern was consistent in both the
phosphate-enriched and phosphate-depleted water columns, contradicting our
hypotheses that the vertical migration of N. spumigena might be induced by phosphate deficiency. Furthermore, our results suggest the unexpected finding that N. spumigena might not be as phosphate-dependent as initially thought. However, the reason behind this is still unsure. Despite the fact that N. spumigena does not seem to have the ability to migrate over a halocline, we believe that this research will, in the long term, contribute to the understanding of N. spumigena and other cyanobacteria in the Baltic Sea bloom-forming mechanisms, as well as to a comprehensive understanding of necessary mitigation efforts to battle ongoing eutrophication effects in the Baltic Sea. (Less) - Popular Abstract
- Imagine a hot summer’s day, and you are walking down to the water for a swim.
However, instead of the usually glittering blue water, you are met by a green, thick, foul-smelling mass. This is something that is becoming more and more common for summer guests on the east coast of Sweden. And one of the biggest culprits is the blue-green algae Nodularia spumigena. Nodularia spumigena is an alga that forms massive green blooms in the late summer in the Baltic Sea, and these blooms are not only unpleasant but can be toxic to both humans and other animals, as well as hurtful to the Baltic Sea’s ecosystems. All algae need nutrients, specifically nitrogen and phosphorus, to form these blooms. Nodularia spumigena is a nitrogen-fixating alga,... (More) - Imagine a hot summer’s day, and you are walking down to the water for a swim.
However, instead of the usually glittering blue water, you are met by a green, thick, foul-smelling mass. This is something that is becoming more and more common for summer guests on the east coast of Sweden. And one of the biggest culprits is the blue-green algae Nodularia spumigena. Nodularia spumigena is an alga that forms massive green blooms in the late summer in the Baltic Sea, and these blooms are not only unpleasant but can be toxic to both humans and other animals, as well as hurtful to the Baltic Sea’s ecosystems. All algae need nutrients, specifically nitrogen and phosphorus, to form these blooms. Nodularia spumigena is a nitrogen-fixating alga, meaning it can collect nitrogen from the air and water but needs to get phosphorus from somewhere else. Excess phosphorus is usually trapped in the deep water in the Baltic Sea. Therefore, in this study, we ask ourselves if Nodularia spumigena might swim all the way to the deep water in the Baltic Sea to get this phosphorus. Our study disclosed that this does not seem to be the case and that Nodularia spumigena does not seem to have the ability to swim down to the deeper, more saline water in the Baltic Sea. The study also found that adding phosphorus to the water had a smaller impact on the growth of Nodularia Spumigena than originally believed. However, the reason behind this is still unclear.
We hope this study will be useful in understanding and managing these large
algae blooms in the Baltic Sea and that, in the long run, this will lead to less
environmental degradation in the Baltic Sea area. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9158394
- author
- Lundin, Malin LU
- supervisor
-
- Per Carlsson LU
- organization
- course
- MVEK12 20241
- year
- 2024
- type
- M2 - Bachelor Degree
- subject
- keywords
- Cyanobacteria, Nodularia spumigena, Baltic Sea, Vertical migration, Phosphate, Algae blooms, Eutrophication
- language
- English
- id
- 9158394
- date added to LUP
- 2024-06-11 13:44:07
- date last changed
- 2024-06-11 13:44:07
@misc{9158394,
abstract = {{Algae blooms, induced by eutrophication, have been an increasingly prevalent
environmental concern in the Baltic Sea since the 1970s, causing ecosystem
degradation and hypoxia in bottom layers. One predominant harmful algae bloom-forming species in the Baltic Sea is the cyanobacteria Nodularia spumigena. N. spumigena produces hepatotoxin nodularin and is a diazotrophic alga; hence, it should be phosphorus-limited. However, looking at the large bloom masses N. spumigena can sustain in the Baltic Sea, this does not seem to be true. Furthermore, excess phosphorus is usually trapped below the halocline in the Baltic Sea. In this study, we conducted a laboratory experiment to investigate whether N. spumigena has the ability to migrate over a halocline. We also explored whether this migration was triggered by phosphate depletion above the halocline and evaluated the impact of phosphate addition on N. spumigena’s average chlorophyll concentration. The experiment was conducted in artificial water columns with two different phosphate concentrations above the halocline (phosphate-depleted and phosphate-enriched). Measurements of chlorophyll- and phosphate concentration at different depths were taken once during the day (10:00) and once during the night (22:00), over a 96-hour sampling period. The results showed no clear vertical migration of N. spumigena over the halocline at any
point during the 96-h sampling period. This pattern was consistent in both the
phosphate-enriched and phosphate-depleted water columns, contradicting our
hypotheses that the vertical migration of N. spumigena might be induced by phosphate deficiency. Furthermore, our results suggest the unexpected finding that N. spumigena might not be as phosphate-dependent as initially thought. However, the reason behind this is still unsure. Despite the fact that N. spumigena does not seem to have the ability to migrate over a halocline, we believe that this research will, in the long term, contribute to the understanding of N. spumigena and other cyanobacteria in the Baltic Sea bloom-forming mechanisms, as well as to a comprehensive understanding of necessary mitigation efforts to battle ongoing eutrophication effects in the Baltic Sea.}},
author = {{Lundin, Malin}},
language = {{eng}},
note = {{Student Paper}},
title = {{Absence of vertical migration across a halocline for the cyanobacteria Nodularia spumigena}},
year = {{2024}},
}