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Effects of warming on the ecology of algal-dominated phytobenthic communities in the Baltic Sea
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Through climate change, the global average air and surface water temperature has risen 0.85°C during the last 100 years. The Baltic Sea experienced one of the most rapid increase in temperature recorded of marine ecosystems. During the last two decades of the 20th century, the surface water temperature of the Baltic Sea has increased seven times faster than the global average.

This thesis is an investigation of how community traits, trophic interactions and ecophysiological processes in the filamentous algal belt in the northern Baltic Sea are affected by warming. The majority of the studies were conducted in or in the vicinity of the Forsmark Biotest basin, an artificial heated enclosure of the southern Bothnian Sea (northern Baltic Sea). One study also included sampling along a natural salinity gradient - the Swedish east coast.

In the benthic diatom community, we found that cell size decreases with decreasing seasonal temperature, and increased with warming during the cold season. Warming also selected for motile and colonial traits. Along the salinity gradient, cell size decreased with decreasing salinity, apparently mediated by changes in the nitrogen to phosphorus ratio.

In the filamentous algal community, warming increased algal cover and photosynthetic capacity, and affected the ratio of carotene to chlorophyll a ratio. Warming also desensitized the photosynthetic response and growth of algal communities exposed to anthropogenic stressors: increased nitrogen and phosphor concentrations as well as copper additions. In connection to one of the field studies, the first finding of the non-native bivalve Mytilopsis leucophaeata in Sweden was also done.

Using a fish exclusion experiment in heated and non-heated areas, we found that warming decreases the number of trophic levels in the lower parts of the food web, which in turn lead to increased top-down control and higher algal biomass at heated than unheated sites.

In summary, warming has here been shown to have major impacts on the phytobenthic community due to a combination of direct effects on physiological processes, as well as indirect effects mediated by interactions among species and trophic levels.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University , 2015. , 69 p.
Keyword [en]
climate change, warming, photosynthesis, trophic cascades, pigments, community traits, temperature gradient, invasive mussel
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-110374ISBN: 978-91-7649-025-9 (print)OAI: oai:DiVA.org:su-110374DiVA: diva2:770962
Public defence
2015-02-20, Föreläsningssalen, Institutionen för ekologi, miljö och botanik, Lilla Frescativägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.

 

Available from: 2015-01-29 Created: 2014-12-11 Last updated: 2015-01-16Bibliographically approved
List of papers
1. Diatom Cell Size, Coloniality and Motility: Trade-Offs between Temperature, Salinity and Nutrient Supply with Climate Change
Open this publication in new window or tab >>Diatom Cell Size, Coloniality and Motility: Trade-Offs between Temperature, Salinity and Nutrient Supply with Climate Change
2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 10, e109993Article in journal (Refereed) Published
Abstract [en]

Reduction in body size has been proposed as a universal response of organisms, both to warming and to decreased salinity. However, it is still controversial if size reduction is caused by temperature or salinity on their own, or if other factors interfere as well. We used natural benthic diatom communities to explore how body size'' (cells and colonies) and motility change along temperature (2-26 degrees C) and salinity (0.5-7.8) gradients in the brackish Baltic Sea. Fourth-corner analysis confirmed that small cell and colony sizes were associated with high temperature in summer. Average community cell volume decreased linearly with 2.2% per degrees C. However, cells were larger with artificial warming when nutrient concentrations were high in the cold season. Average community cell volume increased by 5.2% per degrees C of artificial warming from 0 to 8.5 degrees C and simultaneously there was a selection for motility, which probably helped to optimize growth rates by trade-offs between nutrient supply and irradiation. Along the Baltic Sea salinity gradient cell size decreased with decreasing salinity, apparently mediated by nutrient stoichiometry. Altogether, our results suggest that climate change in this century may polarize seasonality by creating two new niches, with elevated temperature at high nutrient concentrations in the cold season (increasing cell size) and elevated temperature at low nutrient concentrations in the warm season (decreasing cell size). Higher temperature in summer and lower salinity by increased land-runoff are expected to decrease the average cell size of primary producers, which is likely to affect the transfer of energy to higher trophic levels.

National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-108991 (URN)10.1371/journal.pone.0109993 (DOI)000342670800108 ()
Note

AuthorCount:3;

Available from: 2014-12-04 Created: 2014-11-10 Last updated: 2017-12-05Bibliographically approved
2. Warming increases photosynthetic activity in a shallow coastal ecosystem dominated by Cladophora glomerata (L.) Kützing
Open this publication in new window or tab >>Warming increases photosynthetic activity in a shallow coastal ecosystem dominated by Cladophora glomerata (L.) Kützing
(English)Manuscript (preprint) (Other academic)
Keyword
climate change, global warming, coastal ecosystem
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-106840 (URN)
Available from: 2014-08-25 Created: 2014-08-25 Last updated: 2014-12-15
3. First records of Conrad´s false mussel, Mytilopsis leucophaeata (Conrad, 1831) in the southern Bothnian Sea, Sweden, near a nuclear power plant
Open this publication in new window or tab >>First records of Conrad´s false mussel, Mytilopsis leucophaeata (Conrad, 1831) in the southern Bothnian Sea, Sweden, near a nuclear power plant
Show others...
2013 (English)In: BioInvasions Records, ISSN 2242-1300, Vol. 2, no 4, 303-309 p.Article in journal (Refereed) Published
Abstract [en]

The invasive, biofouling, Conrad's false mussel Mytilopsis leucophaeata was first recorded in Sweden during spring 2011 in the cooling water system of the power plant of Forsmark in the southern Bothnian Sea. The cooling water discharge area offers a favourable environment for growth, survival, and reproduction of M. leucophaeata and may provide a stepping stone for further spread. We present three different studies in the area, revealing a rapid increase in mussels in the artificially heated area, with densities of the magnitude of thousands of individuals m-2, as well as mussels living in surrounding waters, indicating an on-going expansion in the region.

Keyword
cooling water, invasive mussel, Bothnian Sea, biofouling, Mytilopsis leucophaeata, Conrad’s false mussel
National Category
Ecology
Research subject
Marine Ecology; Plant Ecology
Identifiers
urn:nbn:se:su:diva-110363 (URN)
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2015-05-25Bibliographically approved
4. Warming decreases sensitivity of epilithic algal communities to nutrient and copper additions
Open this publication in new window or tab >>Warming decreases sensitivity of epilithic algal communities to nutrient and copper additions
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-110368 (URN)
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2014-12-15
5. In situ warming increases top-down control in a coastal food web
Open this publication in new window or tab >>In situ warming increases top-down control in a coastal food web
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-110370 (URN)
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2014-12-15

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