Plankton Controls on Suspended Sediments Plankton Controls on Suspended Sediments and Water Clarity in Chesapeake Bayand Water Clarity in Chesapeake Bay

W. Michael Kemp W. Michael Kemp Walter R. Boynton Walter R. Boynton

University of Maryland University of Maryland Center for Environ. ScienceCenter for Environ. Science

Horn Point Laboratory Horn Point Laboratory Chesapeake Biological LabChesapeake Biological Lab

25 January 200625 January 2006

General Study DesignGeneral Study Design

A) A) Statistical Analysis of Monitoring VFX dataStatistical Analysis of Monitoring VFX data•Relate plankton sinking to environmental variables Relate plankton sinking to environmental variables •Relate inorganic solids sinking to plankton and other variablesRelate inorganic solids sinking to plankton and other variables

B) B) Mesocosm ExperimentsMesocosm Experiments •• Manipulate nutrients and clays over algal bloom cyclesManipulate nutrients and clays over algal bloom cycles •• Test field derived relationshipsTest field derived relationships •• Test idea that algae control sinking & suspension of solidsTest idea that algae control sinking & suspension of solids

C) C) Incorporate Algorithms into Simulation ModelsIncorporate Algorithms into Simulation Models • • Dynamic, spatially aggregated scenarios to test algorithmsDynamic, spatially aggregated scenarios to test algorithms • • Transfer tested algorithms to WES modelTransfer tested algorithms to WES model

*REVISED in January 2005 DE-EMPHASIZING “C”*REVISED in January 2005 DE-EMPHASIZING “C”

Sediment Trap Monitoring Program DesignSediment Trap Monitoring Program Design

• Collection arrays sampling near Collection arrays sampling near surface, bottom, pycnoclinesurface, bottom, pycnocline

•Vertical orientation maintainedVertical orientation maintained

• Consistent orientation into Consistent orientation into currentscurrents

• Collector design with 10:1 aspectCollector design with 10:1 aspect

• Deployment duration 5-7 daysDeployment duration 5-7 days

Chlorophyll-a

Temperature, Salinity

Total Solids

Particulate N, P

DO, (Secchi)-1

Flux

Flux

Stock

Stock

Temp

Salinity

Oxygen

(Secchi)-1

PN

PP

Sediment Trap Data (VFX): 1985-1992Sediment Trap Data (VFX): 1985-1992

• Seasonal deployments February Seasonal deployments February into Decemberinto December

• Eight year (+) data recordEight year (+) data record

• Clear seasonal and inter-annual Clear seasonal and inter-annual patterns related to plankton patterns related to plankton production-respiration balanceproduction-respiration balance

• Measure sinking and Measure sinking and resuspension resuspension of new and recycled particlesof new and recycled particles

•Plankton Chl-Plankton Chl-aa stocks and fluxes stocks and fluxes follow seasonal cyclesfollow seasonal cycles

•Ratio Flux/Stocks is greater inRatio Flux/Stocks is greater in summer than springsummer than spring

•Control by ecological processesControl by ecological processes

•TSS stocks & flux follow Chl-TSS stocks & flux follow Chl-aa seasonal cycles seasonal cycles

•Ratio Flux/Stocks is greater inRatio Flux/Stocks is greater in summer than springsummer than spring

•Clearly, TSS & plankton Chl-Clearly, TSS & plankton Chl-aa dynamics are linked dynamics are linked

Seasonal Sequence of Chl-a & TSS Stocks & FluxesSeasonal Sequence of Chl-a & TSS Stocks & Fluxes

Chl-a Stock

Chl-a Flux

TSS Stock

TSS Flux

Temp

Salinity

PN:PC

PP:PC

Total Solids & Chl-a Fluxes vs. StocksTotal Solids & Chl-a Fluxes vs. Stocks

• Phytoplankton Chl-Phytoplankton Chl-aa stocks & fluxes stocks & fluxes are significantly correlatedare significantly correlated

• Weak relation overall, but strongerWeak relation overall, but stronger by when grouped by seasonby when grouped by season

• Similar relationship among yearsSimilar relationship among years

• Total solids stocks and fluxesTotal solids stocks and fluxes are weakly correlatedare weakly correlated

• Strong correlation between Chl-a Strong correlation between Chl-a flux and solids flux flux and solids flux

• Strongly suggests that TSS flux is Strongly suggests that TSS flux is controlled by plankton processescontrolled by plankton processes

Proportion of Sinking Flux as Lithogenic ParticlesProportion of Sinking Flux as Lithogenic Particles

•Fluxes of total solids & Chl-Fluxes of total solids & Chl-aa are strongly correlatedare strongly correlated

•Because TSS & Chl-Because TSS & Chl-aa sources sources differ, suggests same controls differ, suggests same controls

•““Non-algal” solids dominateNon-algal” solids dominate total mass of sinking particlestotal mass of sinking particles

•Inorganic, non-algal particlesInorganic, non-algal particles comprise 80% total masscomprise 80% total mass

•Non-algal fraction more variableNon-algal fraction more variable in summer in summer

Summary of Data SynthesisSummary of Data Synthesis

• • Seasonal and interannual patterns of plankton Chl-Seasonal and interannual patterns of plankton Chl-aa deposition deposition follows plankton production and grazing cycles follows plankton production and grazing cycles

• • Chl-Chl-aa sinking can be predicted from Chl- sinking can be predicted from Chl-aa stocks, temperature, stocks, temperature, (season) and nutrient conditions (diatom cycles)(season) and nutrient conditions (diatom cycles)

• • Sinking of inorganic solids can be predicted from Chl-Sinking of inorganic solids can be predicted from Chl-aa sinking sinking rates and TSS stocksrates and TSS stocks

• • WQ model simulations of algal and solids sinking should be WQ model simulations of algal and solids sinking should be compared to sediment trap datacompared to sediment trap data

• • Multivariate regression equations developed could be used to Multivariate regression equations developed could be used to model sinking of both algae and inorganic solidsmodel sinking of both algae and inorganic solids

• • Need to consider possible regional variations in these Need to consider possible regional variations in these processesprocesses

Mesocosm Studies: Phytoplankton-TSS InteractionsMesocosm Studies: Phytoplankton-TSS Interactions

• Experiments using replicate 1 mExperiments using replicate 1 m33 MEERC mesocosms with controlled MEERC mesocosms with controlled light, temperature and mixinglight, temperature and mixing

• Simulate spring and summer bloom Simulate spring and summer bloom conditions, add clay to maintain conditions, add clay to maintain background TSSbackground TSS

• Manipulate nutrients to create bloom Manipulate nutrients to create bloom and crash of algal biomassand crash of algal biomass

• Test for evidence of algal processes Test for evidence of algal processes regulating TSS levels & sinking ratesregulating TSS levels & sinking rates

Chlorophyll, TSS, Light Experiments: Protocol #1Chlorophyll, TSS, Light Experiments: Protocol #1

• Need to develop protocols for Need to develop protocols for many aspects of experiment many aspects of experiment

• For example, delivering clay in For example, delivering clay in relation to mixing cyclesrelation to mixing cycles

• Once or twice daily?Once or twice daily?

• Mixing cycle seems to have Mixing cycle seems to have greater impact of TSS levels greater impact of TSS levels than does clay delivery, per sethan does clay delivery, per se

Chlorophyll, TSS, Light Experiments: Protocol #1Chlorophyll, TSS, Light Experiments: Protocol #1

• Use of sensor systems to provide Use of sensor systems to provide continuous data for key variables continuous data for key variables

• Very high chlorophyll-a levels Very high chlorophyll-a levels because of growth medium added because of growth medium added with algal cultureswith algal cultures

• Mixed algal assemblages; Mixed algal assemblages; difficulties in establishing diatom difficulties in establishing diatom dominancedominance

• Spiking data associated with Spiking data associated with spurious electrical signals; need to spurious electrical signals; need to be filtered outbe filtered out

Chlorophyll, TSS, Light Experiments: Protocol #1Chlorophyll, TSS, Light Experiments: Protocol #1

• Despite problems some interesting Despite problems some interesting initial results initial results

• TSS levels seem to accumulate TSS levels seem to accumulate with algal bloom developmentwith algal bloom development

• Algal levels are too high to tell; Algal levels are too high to tell; cells comprise too large a fraction of cells comprise too large a fraction of TSS to infer control TSS to infer control

• Need more controlled lower level Need more controlled lower level algal bloom dominated by diatomsalgal bloom dominated by diatoms

#3: Clay

#3: Nutrients

#3: Clay + Nutrients

Chlorophyll, TSS, Light Experiments: Protocol #3Chlorophyll, TSS, Light Experiments: Protocol #3

• Two protocol experiments later, Two protocol experiments later, we are approaching a controlled we are approaching a controlled system system

• Sensor systems well behaved, Sensor systems well behaved, with filtration routines in placewith filtration routines in place

• Algal community composition Algal community composition controlled by manipulation Si:N controlled by manipulation Si:N ratio, temperature, mixingratio, temperature, mixing

• Two replicated experiments Two replicated experiments planned for winter-spring 2006planned for winter-spring 2006

• • Statistical relationships for modeling sinking rates of Chl-Statistical relationships for modeling sinking rates of Chl-aa and and inorganic solids are nearly finished; available for WES model in inorganic solids are nearly finished; available for WES model in couple of months couple of months

• • Optimistic about results of two mesocosm experiments planned for Optimistic about results of two mesocosm experiments planned for winter-spring of 2006; results used to test statistical models and to winter-spring of 2006; results used to test statistical models and to test idea of algal control of inorganic solid suspension in addition to test idea of algal control of inorganic solid suspension in addition to sinking of solidssinking of solids

• • Unless we are told otherwise, we will continue to follow advice from Unless we are told otherwise, we will continue to follow advice from a previous PI meeting and de-emphasize our proposed simulation a previous PI meeting and de-emphasize our proposed simulation modeling while increasing emphasis on producing data and modeling while increasing emphasis on producing data and statistical relationships useful for WES modelstatistical relationships useful for WES model

Concluding CommentsConcluding Comments