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 VleetCollege of Marine Science, St. Petersburg, FL 33701

in collaboration withT. 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 StrategyField studies:

•Sediment coring throughout Tampa BayAnalytical 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 useUrban / Industrial, Agricultural, Natural

Recorded in Tampa Bay’s Sediments:TOC, TON, C/N,

15N, Molecular Biomarkers

Changing nutrient inputs:•Sources-15N specific•concentrations•bioavailability

Safety Harbor/Feather Sound

Hillsborough Bay/Alafia River

Terra Ceia/Aquatic Preseerve

Study Sites:•Sediment Cores•Geochemical Studies

•Area of land-use characterization

Tampa Bay •6 Watersheds •Variable land-use

Historical Land-Use Changes

• Alafia: increasing urbanization/industrialization • Terra Ceia: increasing agriculture, recent urban • Feather Sound: increasing residential urbanization

15N

, o/o

o A

ir

Fertilizer

Land Plants

Soil

Urban-Sewage Industrial

Specific Nutrient Input

Nitrogen Isotope Fingerprinting of Nutrient Inputs

Safety Harbor-Residential

Terra Ceia-Agriculture

Hillsborough-Urban

Linking Sedimentary & Land-Use Records:

•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

1952 1995

TOC, Wt% C/N, Atomic Ratio 15N, ‰ Air

Dep

th (

cm)

Algal Terr Plants Soil Urban

TON, Wt%Fertilizer/Ter Plant

Redeposited layer

Hillsborough Bay/Alafia River Urbanization/Industrialization

Hum

anIm

pact

Linking Sedimentary and Land-Use Records1952

•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

1995D

epth

(cm

)

Agricult/TerPlant

TOC, Wt% C/N, Atomic Ratio 15N, ‰ Air

TON, Wt%

Terra Ceia/Aquatic PreserveAgricultural

Recent urbanization

Soil

Urban

UrbanFertilizer/Terr Plants

Algal Terr Plants

Hum

anIm

pact

Alafi

a

Linking Sedimentary and Land-Use Records

1952 1995

•Delayed geochemical response reflects later land use development•Abrupt transition to algal/ bacterial inputs•15N reflects increasing residential inputs

(commercial fertilizer, septic-wastewater)

Dep

th (

cm)

TOC, Wt% C/N, Atomic Ratio 15N, ‰ Air

TON, Wt%

Safety Harbor/Feather Sound: Residential Urbanization

Redeposited layer

Hum

anIm

pact

Alafi

a

Terr

a Ce

ia

Algal Terr Plants Soil UrbanFertilizer/Terr Plants

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