MERIS Observations of Lake Balaton

MERIS observations of Lake Balaton phytoplankton dynamics

Lake Balaton, Hungary

• Large, ~ 600 km2 surface area

• Severe eutrophication historically, annual blooms

• Trophic gradient, spatially

• Optically complex

• Ongoing monitoring

Chl-a retrieval validation

Artificial Neural Network:

Case 2 Regional Image radiance and geometry input

• Eutrophic Lake Reflectances, IOPs and concentrations output

• Boreal Lake Atmospheric & constituent retrieval components

• FUB/WeW Different in situ calibration conditions

Different in situ calibration conditions:

• Maximum Chlorophyll Index Make use of peak at 685 / 709 nm
• Fluorescence Line Height Best performance using L1b data

• 1409 full or partial MERIS overpasses (2007-2012)

• 679 in situ chl-a measurements (2007-2012)

• 289 in situ chl-a / clear MERIS matchup points - 1.5 - 57 mg m-3

• Extremely variable algorithm performance
• Neural networks greatly underestimating high chl-a
• Semi-empirical perform well
• FLH performs best

Phytoplankton phenology

Seasonal timing and related features of phytoplankton blooms, such as bloom start & end timing, length, rates of biomass increase & decrease, peak biomass concentrations, number of annual bloom events, etc.

Has been found to be sensitive to climate change and nutrient loading .

Important for trophic level interactions • Phenology of terrestrial vegetation and increasingly the pelagic ocean is commonly assessed using RS; this is underexploited for inland waters.

Lake phenology from space

• TIMESAT software (Jönsson and Eklundh, 2004)

• Time-series of chlorophyll-a concentration maps

• Smoothed time-series for each pixel • Metrics extracted for each smoothed time series and mapped

Conclusions

• Phenology metrics are important ecological indicators; their mapping using EO has been demonstrated for Lake Balaton, Hungary

• A cohesive spatial component is added to phenology analysis & temporal dimension of satellite imagery is taken advantage of in a quantitative manner

• Both spatial and temporal variability of all phenology metrics considered, and of bloom extent, has been revealed

Source: statgis.upol.cz

Read More Related Content On This Topic - Click Here

Media

Taxonomy

• Research
• Environment
• Lake Management