Evaluating the Influence that Anthropogenic Inputs have
on Carbon and Nitrogen Cycling and on the Biological
Assemblages in Tampa Bay, FL
David Hollander, Elon Malkin, Ed Van Vleet
College of Marine Science, St. Petersburg, FL 33701
in collaboration with
T. Edgar, T Cronin, P. Swarzenski, K. Yates, USGS Program Leaders
Project Objectives:
Determine how historical human influences have:
• Altered the geochemical cycling of carbon
and nitrogen (today’s presentation)
• Modified ecosystem structure as recorded in
the inputs of sedimentary organic matter.
Research Strategy
Field studies:
•Sediment coring throughout Tampa Bay
Analytical approach:
•Organic carbon and nitrogen concentrations
– reflects increasing input & production of organic matter
– C:N Ratios determine algal vs terrestrial inputs
•Stable Isotopes of organic carbon and nitrogen
– reflects specific nutrient inputs and assimilation
– trophic relationships
•Molecular organic geochemical analysis
– reflects organic inputs (algal, bacterial, terrestrial and pollution)
Historical Land-use characterization:
•USGS mapping group
•Southwest Water management District
Linking the Sedimentary Geochemical Record
in Tampa Bay to Historical Changes in
Land Use Development and Nutrient Inputs
Watershed’s land use
Urban / Industrial, Agricultural, Natural
Changing nutrient inputs:
•Sources-15N specific
•concentrations
•bioavailability
Recorded in Tampa Bay’s Sediments:
TOC, TON, C/N,
d15N, Molecular Biomarkers
Tampa Bay
•6 Watersheds
•Variable land-use
Safety Harbor/
Feather Sound
Study Sites:
•Sediment Cores
Hillsborough Bay/
Alafia River
•Geochemical Studies
•Area of land-use
characterization
Terra Ceia/
Aquatic Preseerve
Historical Land-Use Changes
• Alafia: increasing urbanization/industrialization
• Terra Ceia: increasing agriculture, recent urban
• Feather Sound: increasing residential urbanization
Nitrogen Isotope Fingerprinting of Nutrient Inputs
Urban-Sewage
Industrial
Safety HarborResidential
Soil
HillsboroughUrban
Fertilizer
Land
Plants
Specific Nutrient Input
Terra CeiaAgriculture
Linking Sedimentary & Land-Use Records:
Hillsborough Bay/Alafia River
1952
1995
Urbanization/Industrialization
TOC, Wt%
d15N, ‰ Air
C/N, Atomic Ratio
Human
Impact
Redeposited layer
Algal
Terr Plants
Fertilizer/
Ter Plant
Soil
Urban
TON, Wt%
•TON/TOC- 4x increase due to nutrient input and increased production
•Transition from vascular plant to algal/bacterial inputs (C:N, biomarkers)
•Enriched 15N > 10 ‰, coprastanol reflect wastewater-industrial inputs
Linking Sedimentary and Land-Use Records
1952
Terra Ceia/Aquatic Preserve
1995
Agricultural
Recent urbanization
C/N, Atomic Ratio
d15N, ‰ Air
Human
Impact
TOC, Wt%
Agricult/
TerPlant
Algal
TON, Wt%
Terr Plants
Fertilizer/
Terr Plants
Soil
Urban
Urban
•Increasing nutrient inputs leading to production (TOC/TON)
•Transition from vascular plant to algal/bacterial inputs (C:N, biomarkers)
•15N- Agricultural nutrient mimic vascular plant inputs, recent urban
Linking Sedimentary and Land-Use Records
Safety Harbor/Feather Sound:
Residential Urbanization
TOC, Wt%
1995
1952
C/N, Atomic Ratio
d15N, ‰ Air
Human
Impact
Redeposited layer
TON, Wt%
Algal
Terr Plants
Fertilizer/
Terr Plants
Soil
Urban
•Delayed geochemical response reflects later land use development
•Abrupt transition to algal/ bacterial inputs
•15N reflects increasing residential inputs
(commercial fertilizer, septic-wastewater)
Geochemical Implications for Ecosystem Modes
• Enables “hind-forecasting” of regional Bay
productivity
• Linking biological responses recorded in sediments
to historical land use and nutrient inputs
• Allows model refinement of nutrient forcing functions
• Distinguishing nutrient abundance from
bioavailability
• Allows for predictive food-web behavior
• Defines relationships among nutrient inputs, primary
productivity, and the abundance of economically
important upper trophic level consumers