Nitrogen Sources and Fluxes to Indian River Lagoon:

A Two Part Research Proposal

Alisa Britt Kepple

Why Should We Care About DIN and PON Concentrations Leaving the St. Lucie Inlet?

* The National Academy of Sciences has proposed that the eutrophication caused by accelerated nitrogen inputs is the biggest threat to coastal resources in the world.

The Indian River lagoon provides an opportunity to study the direct

effects of agricultural rich - population growth on a regional estuary.

St. Lucie Inlet: South Eastern Florida Last stop on the Intercoastal Waterway

HUC 03080202“Cape Canaveral”

Questions to be answered with this study:

• What is the major source of anthropogenically introduced nitrogen to this system and who is responsible?

– Fertilizer– Manure– Boat Pump out Positive source identification of nutrients to the lagoon using Arc Hydro GIS stream tracing

and multi-stable isotope tracers for positive source identification

• Has the EPA’s Baffle Box Solution Solved the Eutrophication Problem? Or made it worse?

•Arc Hydro time series analysis of storm surge events

The problem at St. Lucie:Storm Water Run-off

disrupts the natural ecosytem

• Due to increased population, deforestation, agriculture and industrialization periods of heavy rain lead to:– Influx of nutrients

• Sustained algal blooms– Reduced dissolved oxygen concentrations- Fish Kills

– Obstruct Sunlight - Sea Grass Beds destroyed

– Erosion- Influx of Fine Grained Sediment– Sea Grass Beds and benthic fauna populations destroyed

Part One: Nitrogen Sources to the lagoon

The riverine flux increases in direct proportion to

• Anthropogenic Sources– Fertilizer

– Atmospheric pollution

– Nitrogen fixation by crops

– import/ export of food and feedstocks

– Sewage effluent

– Riverine input of introduced vegetation

• Natural Sources– In-situ N fixation (absent from most estuaries)

– Riverine input of indigenous vegetation

14 N2

Trying to identify the SOURCE of nutrient pollution is a problem:

Euphotic Zone

Atmosphere

NO3-

15PON15 DON 15 NH4

+

N2O

15NO2-

Phytoplankton uptake and assimilation of the N-15 enriched nitrate

N-15 enriched PON incorporated in the sediment record

Sediment

PON (original signal)

Mineralization

NO3-

However, By Running an Additional Isotope on NO3-

Multi-isotope studies offer a direct means of source identification because different sources of nitrate and PON have isotopically distinct C, N, O signatures

Anthropogenically Introduced Sources collected for C, N, O Isotope Analysis

• Ammonium Nitrate Fertlizer- Fast release (golf courses)

• Ammonium Sulfate Fertilizer- Slow release (crops)

• Cow Manure

• Sewage Efluent (Different localities will have different signatures)

• Boat Pump-out (Expect wide range of signatures)

• Non-indigenous grass clippings (Kentucky Blue Grass)

• Non-indigenous tree leaves

• Pineapples

• Citrus (Orange, Grapefruit, tangerine, lemon, lime)

• Papaya

• Winter Vegetables (tomato, peppers, eggplant)

15N

13C18O

Native Plants of St. Lucie County to be collected for S, C, N, O Isotope Analysis

Botanical Name Common NameAcrostichum danaeifolium Giant Leather Fern Avicennia germinans Black MangroveBaccharis halimifolia Saltbush, Groundsel Batis maritima Saltwort Borrichia frutescens Sea-ox-eye Daisy Cassia chamaecrista Partridge Pea Cocoloba uvifera Sea Grape Conocarpus erectus Buttonwood MangroveEugenia axillaris White StopperFlaveria linearis Yellow Top Forestiera segregata Florida Privet Helioptropium angiospermum Scorpion-tailHymenocallis latifolia Spider Lily Juniperus silicicola Southern Red CedarKosteletzkaya virginica Saltmarsh MallowLaguncularia racemosa White MangroveLysinium carolinianum Christmas BerryParthenocissus quinquefolia Virginia Creeper Paspalum repens Water Paspalum Passiflora suberosa Corky Stem Passion Flower Rapanea punctata Myrsine Rhizophora Mangle Red Mangrove Rhus copalllina Southern SumacSabal palmetto Cabbage PalmSerenoa repens Saw Palmetto Sesuvium portulacastrum Sea Purslane Solidago sp. Goldenrod Spartina alternaflora Spartina grass Spartina bakeri Sand Cordgrass Spartina patens Salt-Meadow Cordgrass Verbesina virginica Frostweed

15N13C

18O

1. Water Quality Sample Collection and Stream Networks:

Arc Map Layers

• Ideal sample collection sites will be chosen after completion of base map and query analysis – (base map to show idealized collection sites within proximity of most highly populated, commercialized and farmed areas and areas exhibiting highest nutrient concentrations).

• Interactive query and trace function analysis to determine most likely point source of highest nutrient concentrations along the stream network

– Cylindrical transverse mercator projection – Base map of the Indian river lagoon and stream flow data – Stream networks and basin (EPA River Reach Files, EPA basin files)– Nutrient concentrations (USGS national water information system)

– Grid Polygons:– Indian River citrus industry – (Ammonium Sulfate Fertilizer)– Indian River golf courses – (Ammonium nitrate fertilizer)– Population of residential regions

– Point Feature Classes connected on network:– Marina locations– Sewage treatment plants – EPA baffle box locations

The EPA’s Solution: A Baffle Box• Concrete Sediment Trap

– Designed to trap leaves, sediment and litter

– Installed inside drainage systems along the developed shorelines

– Baffle Box System:

• Estimated 46,000 pounds sediment per month per box

The gradient in St. Lucie is from SL - 85 feet above SL

Baffle Boxes and Drainage Canals

Why I think this is a BIG problem rather than a Solution:

PONNO3

-

NO2-

NH3+

NH4 Surface Area = Bacterial Colonization

Oxygen = Nitrification

Baffle BoxStorm-water

Estuary and Coast

NO3-

INCREASED Primary Productivity DECREASED Sedimentation RateDECREASED oxygen concentration

INCREASED PROBLEMS!

2. Arc HydroTime Series Events

• Three separate time series events will be modeled of suspended sediment, nutrient and oxygen concentrations through the stream network to the lagoon during:– Dry Season– Storm surge event prior top the EPA’s

implementation of the baffle box– Storm surge event following the EPA’s

implementation of the baffle box

• Results from the three models will be queried and an analysis of the effectiveness of the EPA baffle box will be assessed regarding turbidity (fine grained sediment) and nutrient concentrations

Federally Endangered SpeciesAmerican AlligatorAtlantic Hawksbill TurtleAtlantic Green Sea TurtleEastern Indigo SnakeLeatherback Sea TurtleLoggerhead Sea TurtleShort Nosed SturgeonWest India ManateeSoutheastern Beach MouseBachman’s WarblerBald EagleFlorida Scrub JayKirtland’s WarblerPeregrine FalconPiping PloverRed WoodpeckerRoseate TernSnail KiteWood Stork

Process Predicted Signature Reasoning

Influx of Terrigenous Organic MaterialNegative 13C excursionNo change in carbonateNegative 15N excursion

Increased C/N ratio

13C Corg terrestrial = - 27 ‰

15N PON terrestrial = 0 %

Influx of Terrigenous Nutrients and DIC-resulting in increased primaryproductivity

Negative 13C excursion Corg and Cinorganic

Negative 15N excursion

Interpreting the Bulk Sediment Record : Additional Information from C/N and 13C and 15N isotopes

Milder, Montoya, Altabet (1999)

Core and POM/DOM/DIN/ Grab Sample STATION Core/ Grab Sample Station

Methods

Interpreting the C and N Isotope Record

Kao and Liu (2000)

The Determination and Relation Between Nitrate Concentrations in Rivers and the

Marine Environment

• How much nitrate or PON was introduced from a particular source is complicated by:

– The occurrence of multiple possible sources of nitrate and PON

– Overlapping N isotopic composition between point and non-point sources

– Co-existence of biogeochemical processes that alter the stable isotopic signature and concentrations of nitrate which is then incorporated into PON

Sumultaneous Equations

– δ15N = δ15N (Fertilizer) + δ15N (manure) + δ15N (sewage) + δ15N (boat pump out) + δ15N (grass-indig) + δ15N (grass-intro) + δ15N (mangrove) + δ15N (tree-intro) + δ15N (N fix crop)

– 13C = 13C (Fertilizer) + 13C (manure) + 13C (sewage) + 13C (boat pump out) + 13C (grass-indig) + 13C (grass-intro) + 13C (mangrove) + 13C (tree-intro) + 13C (N fix crop)

18O = 18O (Fertilizer) + 18O (manure) + 18O (sewage) + 18O (boat pump out) + 18O (grass-indig) + 18O (grass-intro) + 18O (mangrove) + 18O (tree-intro) + 18O (N fix crop)

• 1 = δ15N (Fertilizer) + δ15N (manure) + δ15N (sewage) + δ15N (boat pump out) + δ15N (grass-indig) + δ15N (grass-intro) + δ15N (mangrove) + δ15N (tree-intro) + δ15N (N fix crop)

15N13C18O

Collection of water Samplesfor Isotopic Analysis

• Samples biologically labile- filter immeadiately 0.1 u filter - refrigerate• Ammonium: “Micro-diffusion method”

– NH4 is slowly diffused into an acid solution to produce ammonium sulfate and then combucted to form N2 gas for the MS

• Nitrate: “Kjeldahl Reaction”

– Distill off existing ammonium- reduce nitrate to ammonium

• Nitrate 18O: Farquhar Method

– NO3--> KNO3

– Combust with Hg(CN)2 --> CO2 gas for the MS

• DON (Amino Acids and Phenols) “Feuerstein Method”

– Freeze Dry, ion chrmoatography, rotovap, dialysis through resins

• Filtered Fraction: POM– Pre-combusted glass fiber filter (GF/F)

– Combust to N2 --> MS

– Can also be analyzed for C, O, S isotopes

Hypothesis• Pre-1565 horizons in sediment cores will provide an isotopic baseline that reflects natural

sources of nitrogen

• Post 1565 to present horizons will show

– an increase in anthropogenically introduced nitrogen (manure, sewage and fertlizer)

– an increase in sedimentation rate

– a bimodal sedimentation pattern (fine and coarse grained)

– An increase in terrestrial vegetation run-off

– significant decrease in indigenous vegetation

– a spatial increase in denitrification (due to eutrophism)

• Post 1990 (Baffle Box)

– Decreased sedimentation rate

– Decreased terrestrial derived PON

– An increase in marine PON deposition laterally

– Increased denitrification laterally

• IF The EPA baffle box HAS been successful- it will be possible to differentiate between St. Lucie Canal fertilizers (Citrus Industry) and fertilizers introduced by the general public

How the Baffle Box Works• Storm-Water is forced through:

– A : Oil collection booms

– B: Sediment falls through grills

–

– C: Sediment is retained behind baffles

– D: Deflectors help maintain sediment despite water flow through

– F: (not shown) over-flow bypass area

• OK… So why THREE isotopes?????????

Kendall and McDonnel, 1998

Rayleigh FractionationAssume: Products are removed from the

Reactants

Denitrification Reactant

Denitrification Product

Capone, 2000

The Nitrogen Cycle: Can’t Assume the Products have been removed:

Associated Isotopic Fractionations

Interpretation is complicated because of multiple cyclesMost fractionation occurs during the “rate determining step”

* Large reservoirLittle or No fractionation Occurs

* Small Reservoir

Process Fractionation ResultFixation - 3 to + 1 Low 15N OM

AssimilationMicrobial Soil

-1.6 – 1 (-0.52) Reduction Reaction- OM

AssimilationVascular Plant

-2.2 to 0.5 (-.25)

AssimilationAlgae

-27 - 0 Smaller α for higher growth rates and lowNO3- and NH4

Mineralization -1 to + 1

Nitrification -35 to 0

Volatilization Ammonia gas produced has a lower 15N

Sorption/Desorption

1- 8

Denitrification + 15 to +30 15N of original nitrate increases

Interpreting the 13C Record

• - Two source model– A.) Sample has an intermediate composition

– B.) Correction Factors Applied: Metabollic Processes have changed the isotopic composition of the sample

• Three Source Model- Need for an additional Isotope– C.) Is sample a mixture of two components or the result of only one component?

Fry and Sher, 1984

In Regions where it is likely that Denitrification has Occurred

• The Effects of Mixing can be distinguished from the effects of denitrification

A= FertilizerB= Manure

But in most situations there are Source- Overlap Identification Problems………

Under idealized conditions, it is possible to tell NO3- generated

from fertilizer versus sewage