An REU Experience and An REU Experience and Research Project: Research Project:

Photolysis of DOM Produced Photolysis of DOM Produced by a Marine Cyanobacteria by a Marine Cyanobacteria

in the Gulf of Mexicoin the Gulf of Mexico

byby

Michael D’AmicoMichael D’Amico

Karenia Karenia BrevisBrevis

HAB’sHAB’s

TrichodesmiuTrichodesmiumm

??

??

Photoproduction of Labile Photoproduction of Labile Substrates from Dissolved Substrates from Dissolved Organic Matter Produced Organic Matter Produced

by by TrichodesmiumTrichodesmiumMichael D’AmicoMichael D’Amico

Mentored byMentored by

Dr. Deborah BronkDr. Deborah Bronk&&

Marta SandersonMarta Sanderson

Processes of photochemical transformation of DOM play Processes of photochemical transformation of DOM play an important part in the global marine biogeochemical an important part in the global marine biogeochemical

cycle. cycle.

DOMDOMPhytoplankton

NHNH44++ NO NO22

-- DPA PO DPA PO443-3-

Trichodesmium Bloom

•Hypothesis:Hypothesis:Water withWater withTrichodesmiumTrichodesmium DOM DOM will have higher rates of will have higher rates of photoproduction than those photoproduction than those without.without.

•Goal:Goal: To quantify rates of DOM To quantify rates of DOM photoproduction of NHphotoproduction of NH44

++, NO, NO22--, DPA, , DPA,

and POand PO443-3- in filtered sea water and in filtered sea water and

water containing DOM produced by water containing DOM produced by TrichodesmiumTrichodesmium..

0.2µm filtered seawater from chlorophyll max0.2µm filtered seawater from chlorophyll max

Incubated in flow through Incubated in flow through seawater tubseawater tub

At 3 hrs. and dusk (~12 hrs.) At 3 hrs. and dusk (~12 hrs.) samples from each bottle were collectedsamples from each bottle were collected

This was done for two experiments in the Gulf of MexicoThis was done for two experiments in the Gulf of Mexico

Sea WaterSea WaterSea Water + Sea Water +

Trichodesmium DOMTrichodesmium DOM

Quartz Quartz DarkDark

TrichodesmiumTrichodesmium DOMDOM2 days prior to each experiment,2 days prior to each experiment,

• Plankton tows using a 64Plankton tows using a 64μm mesh net at μm mesh net at 10m for 10 minutes collected 10m for 10 minutes collected TrichodesmiumTrichodesmium..

•Approx. 1000 colonies of Approx. 1000 colonies of TrichodesmiumTrichodesmium were incubated in 0.2μm Supor filtered were incubated in 0.2μm Supor filtered seawater for 24 hours.seawater for 24 hours.

•At 24 hours, the water containing At 24 hours, the water containing TrichodesmiumTrichodesmium was filtered through a was filtered through a 0.2μm Supor filter, and refrigerated 0.2μm Supor filter, and refrigerated overnightovernight

Chemical AnalysesChemical Analyses

NHNH44+ + concentrationsconcentrations and and POPO44

3-3-

concentrationsconcentrations::•spectrophotometer spectrophotometer •Grasshoff et al. (1983) colorimetric.Grasshoff et al. (1983) colorimetric.

NONO22- - concentrationsconcentrations::

•Alpkem Flow Solution IV nutrient Alpkem Flow Solution IV nutrient autoanalyzerautoanalyzer•Parsons et al. (1984)Parsons et al. (1984)

DPA concentrationsDPA concentrations::•SpectrofluorophotometerSpectrofluorophotometer•Parsons et al. (1984)Parsons et al. (1984)

Photoproduction and Photoproduction and consumption occurconsumption occur

NHNH44++ Photoproduction/balance between Photoproduction/balance between

consumption occursconsumption occurs

POPO443- 3- photoproduction occursphotoproduction occurs

NONO22- - is consumedis consumed

DPA concentrations showed no trendsDPA concentrations showed no trends

•P1 Seawater*:P1 Seawater*:Consumption in Consumption in darkdarkMinor consumption Minor consumption in quartzin quartz•P1 DOM P1 DOM water*:water*:Photoproduction Photoproduction @3h@3hAnd @12hAnd @12h

•P2 Seawater*:P2 Seawater*:Consumption in Consumption in darkdarkMinor Consumption Minor Consumption in quartzin quartz•P2 DOM P2 DOM water*:water*:Consumption in Consumption in darkdarkMinor consumption Minor consumption in quartzin quartz

NHNH44+ + concentrationsconcentrations

PHOTO #1

0.0000

1.0000

2.0000

3.0000

4.0000

5.0000

6.0000

3hrs 12hrs

Co

ncen

trati

on

(u

m)

PHOTO #2

0.0000

1.0000

2.0000

3.0000

4.0000

5.0000

6.0000

3hrs 12hrs

Co

ncen

trati

on

(u

m)

Ambient Dark Quartz Ambient w/DOM Dark w/DOM Quartz w/DOM

•P1 P1 Seawater*:Seawater*:Photoproduction Photoproduction @3h? Not @12h@3h? Not @12hQuartz Quartz ConsumptionConsumption•P1 DOM P1 DOM water*:water*:No No PhotoproductionPhotoproductionQuartz Quartz ConsumptionConsumption

•P2 Seawater:P2 Seawater:No No PhotoproductionPhotoproductionQuartz Quartz ConsumptionConsumption•P2 DOM P2 DOM water:water:No No PhotoproductionPhotoproductionQuartz Quartz ConsumptionConsumption

NONO22- - concentrationsconcentrations

Ambient Dark Quartz Ambient w/DOM Dark w/DOM Quartz w/DOM

PHOTO 1

0.0000

0.0500

3hrs 12hrs

Co

nce

ntr

atio

n (

um

)

PHOTO 2

0.0000

0.0500

0.1000

0.1500

0.2000

0.2500

0.3000

3hrs 12hrs

•P1 Seawater:P1 Seawater: Photoproduction Photoproduction @3h@3hAnd @12hAnd @12h•P1 DOM P1 DOM water*:water*: Photoproduction Photoproduction @3h@3hAnd @12hAnd @12h

•P2 Seawater:P2 Seawater: No No PhotoproductionPhotoproduction•P2 DOM P2 DOM water:water: Photoproduction Photoproduction @3h@3hAnd @12hAnd @12h

Ambient Dark Quartz Ambient w/DOM Dark w/DOM Quartz w/DOMPOPO44

3-3-concentrationsconcentrationsPHOTO 1

0.0000

0.0500

3hrs 12hrs

Co

nce

ntr

atio

n (

um

)

PHOTO 2

0.0000

0.0500

0.1000

0.1500

0.2000

0.2500

0.3000

3hrs 12hrs

Co

nce

ntr

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um

)

•DPA: DPA: No No consistentconsistent trends observed trends observed

Ambient Dark Quartz Ambient w/DOM Dark w/DOM Quartz w/DOMDPA concentrationsDPA concentrations

PHOTO 1

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

3hrs 12hrs

Co

nce

ntr

atio

n (

um

)

PHOTO 2

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

3hrs 12hrs

Co

nce

ntr

atio

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um

)

Evidence for Evidence for PhotoproductionPhotoproduction

EstuaryEstuary NHNH44++, DPA, DPA Bushaw-Newton and Bushaw-Newton and

Moran (1999) Moran (1999)

EstuaryEstuary NHNH44++ Bushaw et al. (1996) Bushaw et al. (1996)

Groundwater, EstuariesGroundwater, Estuaries NHNH44++ Koopmans and Bronk Koopmans and Bronk

(2002) (2002)

Coastal WatersCoastal Waters NONO22-- Kieber et al. (1999)Kieber et al. (1999)

Lake WaterLake Water POPO443-3- Francko and Heath Francko and Heath

(1982) (1982)

Lake WaterLake Water POPO443-3- Vähätalo and Salonen Vähätalo and Salonen

(1996)(1996)

Evidence for ConsumptionEvidence for Consumption

Inconsistent TrendsInconsistent Trends

EstuaryEstuary NHNH44++ Bushaw-Newton and Moran Bushaw-Newton and Moran

(1999) (1999)

EstuaryEstuary NHNH44++ Bushaw et al. (1996) Bushaw et al. (1996)

Groundwater, EstuariesGroundwater, Estuaries NHNH44++ Koopmans and Bronk (2002) Koopmans and Bronk (2002)

Natural WatersNatural Waters NONO22-- Jankowski et al. (1999) Jankowski et al. (1999)

Natural WatersNatural Waters NONO22-- Jorgensen et al. (1998, 1999)Jorgensen et al. (1998, 1999)

Lake WaterLake Water NONO22-- Vähätalo and Salonen (1996)Vähätalo and Salonen (1996)

Groundwater, EstuariesGroundwater, Estuaries NONO22--, DPA, DPA Koopmans and Bronk (2002) Koopmans and Bronk (2002)

Diatom CultureDiatom Culture POPO443-3- Gobler et al. (1997)Gobler et al. (1997)

Fresh Water LakeFresh Water Lake POPO443-3- Jorgensen et al. (1998)Jorgensen et al. (1998)

ConclusionsConclusionsNHNH44

++::

•increasing concentrations in quartz increasing concentrations in quartz tubestubes•decreasing concentrations in dark tubesdecreasing concentrations in dark tubes

•Quartz: NHQuartz: NH44++ photoproduction photoproduction

Or Or Balance between consumption and Balance between consumption and productionproduction

•Dark: NHDark: NH44++ consumption consumption

Humics absorb NHHumics absorb NH44++

ConclusionsConclusionsNONO22

--::

•decreasing concentrations in quartz decreasing concentrations in quartz tubestubes

•Quartz: NOQuartz: NO22-- consumption consumption

Photolysis of NOPhotolysis of NO22- - in sea water:in sea water:

NONO22

-- + h + hvv → NO + → NO + OO--

ConclusionsConclusionsPOPO44

3-3-::

•increasing concentrations in quartz increasing concentrations in quartz tubestubes

•Quartz: POQuartz: PO443-3- photoproduction photoproduction

DPA ???????DPA ???????

Trichodesmium Bloom

Phytoplankton

NHNH44++ NO NO22

-- DPA DPA POPO44

3-3-

Importance:Importance:

Photoproduction of Photoproduction of labile substrates labile substrates

from DOM from DOM influences the influences the availability of availability of nutrients to nutrients to

phytoplanktonphytoplankton

DOMDOM

•Hypothesis:Hypothesis: The treatments that added water with The treatments that added water with TrichodesmiumTrichodesmium DOM will have higher rates of photoproduction DOM will have higher rates of photoproduction than those without.than those without.

•General Trends show yes in some casesGeneral Trends show yes in some cases

•Not true in all casesNot true in all cases

Mahalo!Mahalo!