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Mixotrophy in aquatic flagellates under a climate change scenario

Palha Morais Soares, Ana Margarida (2014) BIOP35 20132
Degree Projects in Biology
Abstract
Abstract

Future climate change scenarios project a water temperature increase of 2 to 5 ˚C for the upcoming 100 years. Simultaneously, north temperate zones will face precipitation changes that will ultimately enhance humic content and water colour in freshwater systems.
I hypothesised that increased temperature and water colour would benefit the grazing activity of mixotrophs, and the dominance of mixotrophic organisms over strict autotrophs and heterotrophs. The hypothesis was tested in an outdoor mesocosm experiment. A gradient of both 1˚C temperature and 50% water colour increase was built in 5 steps up to 5°C and 250% respectively.
Results showed that mixotrophic species outcompeted heterotrophs for the entire period, but not... (More)
Abstract

Future climate change scenarios project a water temperature increase of 2 to 5 ˚C for the upcoming 100 years. Simultaneously, north temperate zones will face precipitation changes that will ultimately enhance humic content and water colour in freshwater systems.
I hypothesised that increased temperature and water colour would benefit the grazing activity of mixotrophs, and the dominance of mixotrophic organisms over strict autotrophs and heterotrophs. The hypothesis was tested in an outdoor mesocosm experiment. A gradient of both 1˚C temperature and 50% water colour increase was built in 5 steps up to 5°C and 250% respectively.
Results showed that mixotrophic species outcompeted heterotrophs for the entire period, but not autotrophs. With regards to grazing activity, important differences were found between the mixotrophic groups present in the mesocosm: Cryptomonas spp. and Dinobryon spp. Temperature and water colour strongly enhanced grazing rates on bacterial prey in Cryptomonas spp., but not in Dinobryon spp. This study also provides evidence that bacteria thrive in a climate change scenario and are grazed effectively by mixotrophic flagellates. This has important consequences for energy and carbon flow along trophic webs, and thus influences our understanding of the microbial loop efficiency. Therefore investigating group-specific responses as well as correctly allocating production and consumption in plankton ecology models is of great importance in future studies. (Less)
Popular Abstract
The great bacterial banquet – voracious algae in a warmer and darker world.

It is nowadays notorious that the world is getting warmer, and even if that may sound pleasant for some of us, that does not necessarily mean so. Otherwise, nobody would worry about climate change. In fact, why are scientists so alarmed?

Climate change or the long-term alterations of weather patterns have been linked to human activity and burning of fossil fuels. Along with temperature, rivers and lakes are also becoming browner in the northern hemisphere, as more coloured substances are being released from soils and washed away by rainfall. Scientists have been reporting consequences of climate change for the last decades and also underlining that the future... (More)
The great bacterial banquet – voracious algae in a warmer and darker world.

It is nowadays notorious that the world is getting warmer, and even if that may sound pleasant for some of us, that does not necessarily mean so. Otherwise, nobody would worry about climate change. In fact, why are scientists so alarmed?

Climate change or the long-term alterations of weather patterns have been linked to human activity and burning of fossil fuels. Along with temperature, rivers and lakes are also becoming browner in the northern hemisphere, as more coloured substances are being released from soils and washed away by rainfall. Scientists have been reporting consequences of climate change for the last decades and also underlining that the future will be neither brighter nor colder.

In some rivers and lakes, photosynthesis will be affected by darker water colour and plants and algae will not be able to grow as efficiently as before. Also, the higher the temperature, the higher the activity of enzymes, and the higher the energy and oxygen consumption. For some organisms, a warmer world demands a higher food intake. These changing processes interfere with our understanding of rivers and lakes. If temperature increases the metabolism of living organisms, and brown water impacts the distribution of sunlight in lakes, how will plants and animals cope with such drastic changes?

Algae eating bacteria?

The whole picture gets even more complicated with recent scientific findings concerning algae eating bacteria. Algae may adopt a mixotrophic metabolism by shifting their feeding mode from photosynthesis to ingesting bacteria. This intriguing metabolic shift raised the core questions of my project, particularly since climate is changing and our usual perception of algae is connected with photosynthesis and oxygen production. Therefore, I collected lake water and increased the water temperature and colour simultaneously, simulating a future scenario for the coming one hundred years. My results showed that climate change benefits the feeding activity of mixotrophic algae in comparison with organisms that can only ingest bacteria, for example. Temperature and water colour strongly boosted the bacterial ingestion of the algae group Cryptomonas spp., but that was not observed in other groups. I also observed that bacteria become more abundant in warmer and darker water and, therefore more food is available for bacteria-eating algae.

Such findings change the way we perceive rivers and lakes, since we know now that some algae can both produce oxygen through photosynthesis and ingest bacteria. Therefore, investigating algae metabolism as well as recognizing which organisms are potentially involved in mixotrophic metabolism is of great importance. In the future, scientists need to take this knowledge into consideration when predicting global changes, and planning solutions in a changing world.

Advisor: Lars-Anders Hansson; Susanne Wilken
Master´s Degree Project 60 credits in Aquatic Ecology 2014
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Palha Morais Soares, Ana Margarida
supervisor
organization
course
BIOP35 20132
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
4537073
date added to LUP
2014-07-08 14:39:56
date last changed
2014-07-08 14:39:56
@misc{4537073,
  abstract     = {Abstract

Future climate change scenarios project a water temperature increase of 2 to 5 ˚C for the upcoming 100 years. Simultaneously, north temperate zones will face precipitation changes that will ultimately enhance humic content and water colour in freshwater systems. 
I hypothesised that increased temperature and water colour would benefit the grazing activity of mixotrophs, and the dominance of mixotrophic organisms over strict autotrophs and heterotrophs. The hypothesis was tested in an outdoor mesocosm experiment. A gradient of both 1˚C temperature and 50% water colour increase was built in 5 steps up to 5°C and 250% respectively. 
Results showed that mixotrophic species outcompeted heterotrophs for the entire period, but not autotrophs. With regards to grazing activity, important differences were found between the mixotrophic groups present in the mesocosm: Cryptomonas spp. and Dinobryon spp. Temperature and water colour strongly enhanced grazing rates on bacterial prey in Cryptomonas spp., but not in Dinobryon spp. This study also provides evidence that bacteria thrive in a climate change scenario and are grazed effectively by mixotrophic flagellates. This has important consequences for energy and carbon flow along trophic webs, and thus influences our understanding of the microbial loop efficiency. Therefore investigating group-specific responses as well as correctly allocating production and consumption in plankton ecology models is of great importance in future studies.},
  author       = {Palha Morais Soares, Ana Margarida},
  language     = {eng},
  note         = {Student Paper},
  title        = {Mixotrophy in aquatic flagellates under a climate change scenario},
  year         = {2014},
}