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Warming increases photosynthetic activity in a shallow coastal ecosystem dominated by Cladophora glomerata (L.) Kützing
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
(English)Manuscript (preprint) (Other academic)
Keyword [en]
climate change, global warming, coastal ecosystem
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-106840OAI: oai:DiVA.org:su-106840DiVA: diva2:740412
Available from: 2014-08-25 Created: 2014-08-25 Last updated: 2014-12-15
In thesis
1. Effects of warming on the green alga Cladophora glomerata: Ecological and genetic responses
Open this publication in new window or tab >>Effects of warming on the green alga Cladophora glomerata: Ecological and genetic responses
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since the beginning of the 20th century, average global surface temperature has increased ~0.7 °C and the current scenarios predict that it will continue to rise additional 2-4 °C during the 21st century. Although many emphasise the need to better understand how warming affect ecosystems on both communities and species level, conclusive data is relatively scarce and our understanding of the effects of warming on community processes and species’ genetic and plastic responses to climate change is still in its infancy.

This thesis aims at investigating the ecological and ecophysiological responses to warming of the vegetation in the littoral zone in the Baltic Sea and whether warming affects the genetic composition of the dominant algal species in this zone, the green alga Cladophora glomerata. Warming was studied by comparing properties of the vegetation and the genetic composition of C. glomerata grown in natural communities in unheated sites and heated sites with 3.4-10.3 °C higher water temperature. The studies in this thesis were performed in the Forsmark (60°24'N 18°09'E) and Oskarshamn (57°25'N 16°40'E) areas.

The thesis shows that warming changed the community composition in Cladophora-belts, but not the species richness. It also shows that vegetation coverage and height increased with warming. The results also suggest that the vegetation at the heated sites was exposed to lower levels of oxidative stress. The results showed relatively high genetic diversity in the strictly asexual species C. glomerata, but that the genetic diversity decreases with warming. Further, all analyses showed differences between samples from heated and unheated sites and revealed specific patterns for samples from the heated sites. Additonally, C. glomerata at heated sites were more strongly affected by the effect of season than at the unheated sites. An analysis of the genotypic composition of C. glomerata from heated and unheated sites in the two different sub-basins of the Baltic Sea (Forsmark and Oskarshamn) revealed a congruent direction in selection to warming.

In all, this new knowledge increases the understanding of how a habitat-forming filamentous alga in a coastal ecosystem may respond to current and future global warming.

Abstract [sv]

Sedan 1900-talets början har den globala medeltemperaturen ökat med 0,7 °C och enligt nuvarande prognoser, bland annat från FN:s klimatpanel, förväntas temperaturen fortsätta att öka med ytterligare 2-4 °C under 2000-talet. Kunskapen om vad vi kan förvänta oss för effekter av den globala uppvärmningen på ekosystem och enskilda arter är fortfarande otillräcklig.

I denna avhandling studeras effekter av uppvärmning på vegetationen i den littorala zonen i Östersjön samt på den genetiska sammansättningen hos en dominarande algart i denna zon, Cladophora glomerata (grönslick). Effekter av uppvärmning studerades genom att jämföra egenskaper hos vegetationen samt den genetiska profilen hos C. glomerata från naturliga lokaler och lokaler med 3.4-10.3 °C högre vattentemperatur. De uppvärmda lokalerna är i områden där kylvatten från Forsmarks (60°24'N 18°09'E) respektive Oskarshamns (57°25'N 16°40'E) kärnkraftverk släpps ut.

Avhandlingen visar att uppvärmning ändrade sammansättningen men inte artrikedomen på vegetationen i det s.k. grönslicks-bältet. Den visar också att vegetationens täckningsgrad och höjd ökade med uppvärmning. Resultaten antyder också att vegetationen i de uppvärmda lokalerna var utsatta för lägre nivåer av oxidativ stress. Den genetiska diversiteten i grönslick är relativt hög trots att den är en klonal och obligat asexuell art, men den genetiska diversiteten minskar med hög uppvärmning. Den genetiska kompositionen hos grönslick från de uppvärmda lokalerna uppvisade liknande genetisk sammansättning i alla analyser och skilde sig från den hos grönslick från de ouppvärmda lokalerna. Vidare påvisade resultaten att effekten av säsong påverkar grönslicksbestånden i de uppvärmda lokalerna mer än bestånden i de ouppvärmda lokalerna. Jämförelser gjordes också av den genetiska sammansättningen hos grönslick från uppvärmda och ouppvärmda lokaler både vid Forsmark och Oskarshamn. Resultaten visar att skillnader mellan uppvärmda och ouppvärmda ställen var likartad i både Forsmark och Oskarshamn, vilket kan tolkas som att det som en effekt av uppvärmning sker en selektion i liknande riktning på båda ställen.

Sammanfattningsvis bidrar denna studie till en ökad förståelse om hur en habitat-byggande filamentös alg kan reagera på gällande och framtida globala temperaturökningar i ett kustekosystem.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2014. 71 p.
Keyword
AFLP, Baltic Sea, Cladophora glomerata, climate change, community ecology, genome scan, global warming, selection
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-106847 (URN)978-91-7447-954-6 (ISBN)
Public defence
2014-10-03, Lecture hall, Department of Ecology, Environment and Plant Sciences, 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 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2014-09-11 Created: 2014-08-25 Last updated: 2014-09-15Bibliographically approved
2. Effects of warming on the ecology of algal-dominated phytobenthic communities in the Baltic Sea
Open this publication in new window or tab >>Effects of warming on the ecology of algal-dominated phytobenthic communities in the Baltic Sea
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
climate change, warming, photosynthesis, trophic cascades, pigments, community traits, temperature gradient, invasive mussel
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-110374 (URN)978-91-7649-025-9 (ISBN)
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

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