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Benthic-Pelagic Microbial Interactions and Carbon Cycling in Clearwater Lakes
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the interactions among microbiota in clearwater lakes. Field sampling and field experiments were performed to evaluate interactions among microbiota and the importance of benthic versus pelagic microbiota in terms of biomass and production. In addition, carbon cycling in an oligotrophic clearwater lake was calculated.

Biomass and production of microbiota was clearly focused to the benthic habitat. During natural nutrient concentrations growth of heterotrophic bacteria (benthic and pelagic) was coupled to production of microphytobenthos in Lake Eckarfjärden, indicating interactions between autotrophic and heterotrophic microbiota in, as well as between, habitats. At increased nutrient concentrations, growth of heterotrophic bacteria was not correlated to microphytobenthos production. This was explained by less release of dissolved organic carbon (DOC) from microphytobenthos when they got access to more nutrients. Further investigations showed different scenarios in oligotrophic clearwater lakes following increased nutrient concentrations. The interactions between microbiota may be altered following increased nutrient concentrations and the microbial mat either positively or negatively affect the pelagic microbiota. The most striking result was that the expected shift towards dominance of pelagic primary production does not necessarily occur.

Major flows of carbon were identified between different habitats in the oligotrophic clearwater Lake Eckarfjärden, and the net result was that the benthic habitat provided carbon to the pelagial. High DOC concentrations in the lake together with low pelagic production are factors that would indicate net heterotrophy. Accordingly, the pelagial of Lake Eckarfjärden was net heterotrophic but when the benthic and littoral habitats were included in the calculations, the lake turned out to be net autotrophic.

In conclusion, the benthic microbiota contributed significantly to the total production in the investigated lakes and had a major role in the lake metabolism. Thus, this thesis emphasises the importance of benthic microbiota in shallow clearwater lakes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2005. , p. 39
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 52
Keywords [en]
Biology, microphytobenthos, phytoplankton, heterotrophic bacteria, interactions, nutrients, carbon cycling, clearwater lakes
Keywords [sv]
Biologi
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-5798ISBN: 91-554-6251-0 (print)OAI: oai:DiVA.org:uu-5798DiVA, id: diva2:166419
Public defence
2006-02-03, Ekmanssalen, Kärnhuset, EBC, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2009-03-31Bibliographically approved
List of papers
1. Characteristics of oligotrophic hardwater lakes in a postglacial land-rise area in mid-Sweden
Open this publication in new window or tab >>Characteristics of oligotrophic hardwater lakes in a postglacial land-rise area in mid-Sweden
2002 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 47, no 8, p. 1451-1462Article in journal (Refereed) Published
Abstract [en]

1. We describe some remarkable ephemeral, oligotrophic hardwater lakes formed becauseof land rise in the coastal areas of the Baltic Sea, that are unique in Sweden and probablyalso worldwide. Two younger, coastal lakes were studied by regular sampling for 1 yearand compared with an older (i.e. greater altitude) lake, that passed through theoligotrophic hardwater stage some 3–4000 years ago.

2. Despite some differences in composition of the catchment, the two younger lakes weresimilar with regard to water chemistry and plankton community composition. Theconcentration of phosphorus was low while nitrogen was high, resulting in very high N/Pquotients (101 and 131). Although water colour was moderate, the concentration of organiccarbon was extremely high (average values of ‡ 20 lg TOC L–1), consisting mainly ofdissolved compounds (DOC).

3. While the plankton was poorly developed, sediments in both lakes were covered by alayer of photosynthesising micro-organisms. This substantial 'microbial mat', which hasnot been described in detail before, was up to 15 cm thick and dominated by cyanobacteriaand purple sulphur bacteria. The concentration of sediment phosphorus was extremelylow (352 lg g–1 dw) in one of the lakes and dominated by organic-bound (residual)phosphorus.

4. Deep sediments in the older lake, representing its oligotrophic hardwater period,differed in phosphorus composition from the currently oligotrophic hardwater lakes byhaving a strong dominance of HCl-extractable (Ca-bound) phosphorus. This indicates thatphosphorus, initially organic-bound within the microbial mat, is subsequently bound tocalcium. We hypothesise that this is promoted by the environmental conditions created bythe benthic photosynthetic activity, in combination with the prevailing hardwaterconditions.

5. The rich and flourishing microbial community on the sediments may also explain thehigh concentration of DOC in the lake.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-93054 (URN)
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2018-06-05Bibliographically approved
2. Net autotrophy in an oligotrophic lake rich in dissolved organic carbon and with high benthic primary production
Open this publication in new window or tab >>Net autotrophy in an oligotrophic lake rich in dissolved organic carbon and with high benthic primary production
2006 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 43, no 1, p. 1-10Article in journal (Refereed) Published
Abstract [en]

Biomass and production of microbiota—primary producers as well as heterotrophic bacteria—were studied both in the pelagial and in the benthic habitat over 2 yr in the shallow oligotrophic Lake Eckarfjärden, Sweden. Both biomass and production of microbiota were concentrated in the benthic habitat. Despite a high dissolved organic carbon (DOC) concentration of about 25 mg C l–1 in the water, the total bacterial production was lower than the total primary production. Moreover, measurements of DOC concentrations in the in- and outflow, and CO2-saturation measurements, indicate that the system is net autotrophic. Generally, low-productive systems (<100 µg C l–1 d–1) tend to be net heterotrophic. In contrast, we found a low-productive (55 µg C l–1 d–1) but net autotrophic system, the conditions of which were largely influenced by benthic production. Many lakes in the world are shallow and may provide substantial benthic areas suitable for primary production. Hence, it is important to include this habitat when evaluating whether lakes are autotrophic or heterotrophic systems.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-93055 (URN)10.3354/ame043001 (DOI)
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2018-06-05Bibliographically approved
3. Inorganic nutrient acquisition in a shallow clearwater lake: dominance of benthic microbiota
Open this publication in new window or tab >>Inorganic nutrient acquisition in a shallow clearwater lake: dominance of benthic microbiota
2006 (English)In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 68, no 2, p. 172-180Article in journal (Refereed) Published
Abstract [en]

This mesocosm study from the oligotrophic Lake Eckarfjärden in Sweden shows, in contrast to many previous studies, that benthic microbiota dominated production following elevated nutrient concentrations in the water. Increased nutrient concentrations favoured microphytobenthos, whereas phytoplankton biomass remained roughly the same. Microphytobenthos biomass and production were clearly stimulated by nitrogen addition, while phytoplankton showed signs of phosphorus limitation. There were tight interactions between pelagic and benthic habitats and between organisms, and pelagic as well as benthic heterotrophic bacteria were disfavoured when microphytobenthos had access to nitrogen.

We conclude that increased nutrient concentrations in the water column may trigger immediate responses in both habitats, altering the tight interactions between microbiota, but not necessarily resulting in a shift towards pelagic production.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-93056 (URN)10.1007/s00027-006-0805-x (DOI)
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2018-06-05Bibliographically approved
4. Benthic-pelagic coupling in a shallow clearwater lake - effects of nutrient addditions on plankton
Open this publication in new window or tab >>Benthic-pelagic coupling in a shallow clearwater lake - effects of nutrient addditions on plankton
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-93057 (URN)
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2014-07-14Bibliographically approved
5. A carbon budget for an oligotrophic clearwater lake in mid-Sweden
Open this publication in new window or tab >>A carbon budget for an oligotrophic clearwater lake in mid-Sweden
2006 (English)In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 68, no 1, p. 52-64Article in journal (Refereed) Published
Abstract [en]

In this study, a whole-lake carbon budget for the oligotrophic, clearwater Lake Eckarfjärden was established both on an annual and seasonal basis. For budget calculations, the lake was divided into three habitats (pelagial, littoral and benthic) and the biota into 19 functional groups. In the lake, major parts of biomass (97%) and primary production (91%) are concentrated in benthic and littoral habitats and to a few functional groups. Respiration on the other hand, is focused on benthic and pelagial habitats where 60% and 39%, respectively, of the respiration took place. Our conceptual model indicates strong interactions between habitats. For instance, the pelagial is fed with carbon fixed by primary producers in the benthic and littoral zones. On an annual basis, total primary production exceeds total respiration and the lake is net autotrophic. However, there are clear differences between habitats and between seasons. For instance, the littoral is net autotrophic during spring, summer and autumn, the benthic habitat is net autotrophic only during summer, and the pelagial is always net heterotrophic. Our results demonstrate clear couplings between habitats and organisms and the importance of a holistic view when studying lake ecosystems.

Keywords
Lake Eckarfjärden, functional groups, carbon flows, habitat interactions, metabolic processes
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-93058 (URN)10.1007/s00027-005-0807-0 (DOI)
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2017-12-14Bibliographically approved

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