Getting involved! Students, Post-docs, etc.:
if you are interested in our research on aquatic food web ecology, would like to pursue your internship, BSc, MSc, PhD, or post-doc, or sabbatical research with us, simply contact us and join in!
if you are interested in our research on aquatic food web ecology, would like to pursue your internship, BSc, MSc, PhD, or post-doc, or sabbatical research with us, simply contact us and join in!
Aquatic food web ecology
Much of our research revolves around questions about food web functioning in aquatic ecosystems. We ask,
a) How do diet sources differ in their biochemical composition among ecosystems?
b) How are different diets utilized by consumers, such as zooplankton, benthic invertebrates, and fishes?
c) How and which diet is conveyed across several trophic levels and allocated within consumers?
d) How does climate change affect the supply, uptake, biotic utilization, and trophic transfer of diet sources?
Aquatic food web ecology
Much of our research revolves around questions about food web functioning in aquatic ecosystems. We ask,
a) How do diet sources differ in their biochemical composition among ecosystems?
b) How are different diets utilized by consumers, such as zooplankton, benthic invertebrates, and fishes?
c) How and which diet is conveyed across several trophic levels and allocated within consumers?
d) How does climate change affect the supply, uptake, biotic utilization, and trophic transfer of diet sources?
TROPHIC BIOMARKERS:
To discern different diet sources, we apply and further develop trophic biomarkers by using stable isotopes, fatty acids, and compound-specific stable isotopes. Our research suggests that the combination of bulk stable isotopes and fatty acids yields a more detailed understanding of how different diet sources are utilized and retained in aquatic consumers of various ecosystems (e.g., Jardine et al. 2015; Brett et al. 2017; Kainz et al. 2017).
We recently developed a method to analyze hydrogen stable isotopes (del-2H) of fatty acids and could thus complement the existing pool of compound-specific stable isotopes as trophic biomarkers in aquatic food webs (Pilecky et al. 2021). Hydrogen stable isotopes provide more distinct isotopic differences between natural diet sources, such as terrestrial vs. aquatic diets (Twining et al. 2020; Mathieu-Resuge et al. 2021).
In addition to using bulk stable isotopes in our analytical laboratory, we apply the following groups of fatty acids as source biomarkers:
- Bacterial sources (e.g., odd-chain, branched fatty acids, incl. 15:0, 17:0, as well as their iso- and anteiso homologues)
- Plant/algal sources (e.g., polyunsaturated fatty acids of various chain lengths and degrees of unsaturation)
- Terrestrial sources (e.g., long-chain saturated fatty acids, incl. 24:0 and longer)
see: McMeans et al. (2015)
To discern different diet sources, we apply and further develop trophic biomarkers by using stable isotopes, fatty acids, and compound-specific stable isotopes. Our research suggests that the combination of bulk stable isotopes and fatty acids yields a more detailed understanding of how different diet sources are utilized and retained in aquatic consumers of various ecosystems (e.g., Jardine et al. 2015; Brett et al. 2017; Kainz et al. 2017).
We recently developed a method to analyze hydrogen stable isotopes (del-2H) of fatty acids and could thus complement the existing pool of compound-specific stable isotopes as trophic biomarkers in aquatic food webs (Pilecky et al. 2021). Hydrogen stable isotopes provide more distinct isotopic differences between natural diet sources, such as terrestrial vs. aquatic diets (Twining et al. 2020; Mathieu-Resuge et al. 2021).
In addition to using bulk stable isotopes in our analytical laboratory, we apply the following groups of fatty acids as source biomarkers:
- Bacterial sources (e.g., odd-chain, branched fatty acids, incl. 15:0, 17:0, as well as their iso- and anteiso homologues)
- Plant/algal sources (e.g., polyunsaturated fatty acids of various chain lengths and degrees of unsaturation)
- Terrestrial sources (e.g., long-chain saturated fatty acids, incl. 24:0 and longer)
see: McMeans et al. (2015)
TROPHIC ENERGY and USE OF RESOURCES ... and a current problem:
The well-established River Continuum Concept suggests headwater streams in temperate forests being strongly dominated by terrestrial organic matter (t-OM). At the same time, these streams are typical habitats for freshwater salmonids, such as trout and charr, which are rich in omega-3 polyunsaturated fatty acids (n-3 PUFA). However, n-3 PUFA required for salmonids do not occur in t-OM. Thus, the high dietary omega-3 PUFA supply for salmonids and other headwater consumers, such as benthic invertebrates, may be too low.
In a current FWF research project ("From Alpha to Omega-3"), we target this conundrum and investigate,
a) spatial and seasonal variation in consumer dependence (benthic invertebrates and fish) on elemental (C and N and their stable isotopes) and molecular (lipids and their fatty acids) composition of basal resources along a longitudinal, pre-alpine stream gradient (ecosystem approach),
b) under different light conditions, the effect of allochthonous and autochthonous diet sources in headwater streams on dietary supply and retention of fatty acids in headwater benthic invertebrates (experimental approach), and,
c) using radioactive hepatocyte bioassays, the ability of freshwater fish to convert precursor fatty acids to DHA to compensate for a lack of dietary DHA (hepatic lipid metabolism in freshwater fish).
This research uses state-of-the-art methods, including flume experiments, linked with field investigations and apply stable isotopes, lipids and fatty acids, and compound-specific stable isotopes (C and H). We expect to shed light on the long-standing question of how consumers in headwater streams, but also in lowland streams, manage or fail to obtain essential nutrients and high quality forms of energy. See our review paper (Guo et al. 2017) and how macroinvertebrates feed and retain their diet sources in these subalpine stream food webs (Guo et al. 2018).
Major findings:
1. Terrestrial organic matter is poorly retained in macroinvertebrates (Kühmayer et al. 2020) and fishes (Ebm et al. 2021) of subalpine streams.
2. Based on hydrogen stable isotopes of essential fatty acids, terrestrial organic matter clearly differs from algal organic matter (Twining et al. 2020).
TROPHIC ENERGY and USE OF RESOURCES ... and a current problem:
The well-established River Continuum Concept suggests headwater streams in temperate forests being strongly dominated by terrestrial organic matter (t-OM). At the same time, these streams are typical habitats for freshwater salmonids, such as trout and charr, which are rich in omega-3 polyunsaturated fatty acids (n-3 PUFA). However, n-3 PUFA required for salmonids do not occur in t-OM. Thus, the high dietary omega-3 PUFA supply for salmonids and other headwater consumers, such as benthic invertebrates, may be too low.
In a current FWF research project ("From Alpha to Omega-3"), we target this conundrum and investigate,
a) spatial and seasonal variation in consumer dependence (benthic invertebrates and fish) on elemental (C and N and their stable isotopes) and molecular (lipids and their fatty acids) composition of basal resources along a longitudinal, pre-alpine stream gradient (ecosystem approach),
b) under different light conditions, the effect of allochthonous and autochthonous diet sources in headwater streams on dietary supply and retention of fatty acids in headwater benthic invertebrates (experimental approach), and,
c) using radioactive hepatocyte bioassays, the ability of freshwater fish to convert precursor fatty acids to DHA to compensate for a lack of dietary DHA (hepatic lipid metabolism in freshwater fish).
This research uses state-of-the-art methods, including flume experiments, linked with field investigations and apply stable isotopes, lipids and fatty acids, and compound-specific stable isotopes (C and H). We expect to shed light on the long-standing question of how consumers in headwater streams, but also in lowland streams, manage or fail to obtain essential nutrients and high quality forms of energy. See our review paper (Guo et al. 2017) and how macroinvertebrates feed and retain their diet sources in these subalpine stream food webs (Guo et al. 2018).
Major findings:
1. Terrestrial organic matter is poorly retained in macroinvertebrates (Kühmayer et al. 2020) and fishes (Ebm et al. 2021) of subalpine streams.
2. Based on hydrogen stable isotopes of essential fatty acids, terrestrial organic matter clearly differs from algal organic matter (Twining et al. 2020).
ENVIRONMENTAL CHANGE:
Current weather changes affect ecosystems in various ways. Since the beginning of the 20th century, Lake Lunz, our subalpine, oligotrophic model lake just outside of our research center WasserCluster Lunz, is monitored and investigated regularly. Based on a true treasure of long-term data series, together with the research group AquaScale, we can understand how this lake, together with many other lakes in the world, has changed in the past and continues to change now and in the future (Kainz et al. 2017).
Current weather changes affect ecosystems in various ways. Since the beginning of the 20th century, Lake Lunz, our subalpine, oligotrophic model lake just outside of our research center WasserCluster Lunz, is monitored and investigated regularly. Based on a true treasure of long-term data series, together with the research group AquaScale, we can understand how this lake, together with many other lakes in the world, has changed in the past and continues to change now and in the future (Kainz et al. 2017).
EXPERIMENTAL RESEARCH - lab, fish feeding, and mesocosm studies:
In addition to our research on aquatic ecosystems, we concurrently conduct experiments on;
a) plankton:
- lab studies (e.g., Koussoroplis et al. 2014)
- and mesocosms (e.g., Rasconi et al. 2015, 2017), and,
b) fish feeding response (fish tanks):
e.g., Murray et al. (2014, 2015), Kainz et al. (2018)
XENOBIOTICS:
We are also concerned about dietary uptake, trophic transfer, and physiological effects of xenobiotics, such as methyl mercury (Wu et al. 2021; de Wit et al. 2014; Schultz et al. 2012; Kainz and Mazumder 2005) and other persistent organic pollutants (Kainz and Fisk, 2009).