TY - JOUR
T1 - Identifying recent sources of organic matter enrichment and eutrophication trends at coastal sites using stable nitrogen and carbon isotope ratios in sediment cores
AU - Vaalgamaa, Sanna
AU - Sonninen, Eloni
AU - Korhola, Atte
AU - Weckström, Kaarina
N1 - Funding Information:
Acknowledgments We thank the SW Finland Regional Environment Centre (Tapio Suominen and Janne Suomela) for good teamwork in the field. We also thank Peter Appleby from the University of Liverpool for dating the sediment cores. This research was supported by the Academy of Finland (contract 202436, DETECT), an IEF Marie Curie Fellowship to Kaarina Weckström (grant agreement 236678) and a HENVI (Helsinki University Centre for Environment) postdoctoral fellowship to Sanna Vaalgamaa.
PY - 2013/8
Y1 - 2013/8
N2 - We studied the potential for using stable carbon and nitrogen isotope ratios in sediment profiles to trace external nutrient sources and eutrophication at four coastal sites in the Baltic Sea. The sites are characterized by various present and past activities in their catchments, including residential development, sugar processing, agriculture and fish farming. Radiometrically dated sediment cores were analysed for nutrient isotope ratios, organic carbon and total nitrogen. Background information was collected from historical sources, literature and water monitoring data. Despite the multiple organic enrichment sources, it was possible to identify individual sources and processes in the sediment profiles using stable isotope analysis of bulk sediment. The largest changes in δ
15N values were seen at sites receiving urban wastewaters. The site that received effluents from a sugar cane (C
4-plant) refinery in the past showed a clear effect on δ
13C values compared to the site that received wastewater from a sugar beet (C
3-plant) factory. Fish farming produced detectable, albeit minor changes in the sediment profile. Slightly lower δ
13C values reflected the influence of fish feed and fish metabolism, and higher δ
15N values likely indicated the influence of increased sediment denitrification. The land-sea connection via river discharge was observable in the overall δ
13C levels of the sediment cores. Our results suggest that temporal changes in sources of organic matter enrichment can be detected in well-dated coastal sediment cores using nutrient stable isotope analyses, even at sites subjected to multiple impacts. There is not, however, a simple relationship between sediment stable isotope profiles and the eutrophication history of our study sites.
AB - We studied the potential for using stable carbon and nitrogen isotope ratios in sediment profiles to trace external nutrient sources and eutrophication at four coastal sites in the Baltic Sea. The sites are characterized by various present and past activities in their catchments, including residential development, sugar processing, agriculture and fish farming. Radiometrically dated sediment cores were analysed for nutrient isotope ratios, organic carbon and total nitrogen. Background information was collected from historical sources, literature and water monitoring data. Despite the multiple organic enrichment sources, it was possible to identify individual sources and processes in the sediment profiles using stable isotope analysis of bulk sediment. The largest changes in δ
15N values were seen at sites receiving urban wastewaters. The site that received effluents from a sugar cane (C
4-plant) refinery in the past showed a clear effect on δ
13C values compared to the site that received wastewater from a sugar beet (C
3-plant) factory. Fish farming produced detectable, albeit minor changes in the sediment profile. Slightly lower δ
13C values reflected the influence of fish feed and fish metabolism, and higher δ
15N values likely indicated the influence of increased sediment denitrification. The land-sea connection via river discharge was observable in the overall δ
13C levels of the sediment cores. Our results suggest that temporal changes in sources of organic matter enrichment can be detected in well-dated coastal sediment cores using nutrient stable isotope analyses, even at sites subjected to multiple impacts. There is not, however, a simple relationship between sediment stable isotope profiles and the eutrophication history of our study sites.
KW - Baltic Sea
KW - C and N stable isotopes
KW - Organic matter
KW - Recent eutrophication
KW - Sediment profiles
UR - http://www.scopus.com/inward/record.url?scp=84880369583&partnerID=8YFLogxK
U2 - 10.1007/s10933-013-9713-y
DO - 10.1007/s10933-013-9713-y
M3 - Article
SN - 0921-2728
VL - 50
SP - 191
EP - 206
JO - Journal of Paleolimnology
JF - Journal of Paleolimnology
IS - 2
ER -