PhytoplanktonMichael L. Parsons

Coastal Watershed InstituteFlorida Gulf Coast University

Phytoplankton (microalgae)

Cyanobacteria (Microcystis)Diatom (Pseudo-nitzschia) Diatom (Actinoptychus)

Dinoflagellate (Karenia brevis)

Dinoflagellate (Gambierdiscus)

Chlorophyte

Silicoflagellate

Haptophyte

Diatom (Chaetoceros)

OverviewThe Good: phytoplankton are the base of the

foodwebThe Bad: too much can have negative impactsThe Ugly: some phytoplankton can produce

toxins that can kill animals and make people sick

Food Web

Phytoplankton Growth RequirementsLightNutrients (nitrogen, phosphorus, carbon,

other compounds)Can serve as indicators of nutrient loading

and light availability

The Good

nutrients plankton

phyto

pla

nkt

on

fish

The Bad

The Ugly

Phytoplankton and the CaloosahatcheeMany factors that affect the growth of

phytoplankton in the Caloosahatchee are controlled/influenced by the flow of the river.

As flow increases:nutrients phytoplanktonresidence time phytoplanktonsalinity assemblage shift

flow nutrients phytoplankton

Doering et al. 2006

flow residence time phytoplankton

Wan et al. 2013

Doering et al. 2006

flow residence time phytoplankton

Wan et al. 2013

flow salinity assemblage shift

Andresen 2011

Andresen 2011

Brand, unpub.

Red Tides and Caloosahatchee Discharges

Brown et al. 2006

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

7

14

21

28

35Red tide frequency versus S79 N loading

mg N/cf/s

% o

f sam

ples

>10

0,00

Kar

enia

bre

vis

per l

iter

“The combined flux of N and P from TB, CH, and the Caloosahatchee River could theoretically supply 11–50% of the N and 11–57% of the P required to support growth of the measured population abundance for each of the three blooms”

Workshop QuestionsWhat driver is the indicator sensitive to?

Nutrients, salinity, light

What constitutes a healthy population of the indicator? Low/moderate cell concentrations; more diatoms and less

cyanobacteria and flagellates

Is the indicator a valued component of the Caloosahatchee system? Should be!

What metrics are appropriate for assessing this indicator? Chlorophyll concentrations; species identifications

Workshop QuestionsWhat are the strengths and limitations of this indicator?

Chlorophyll is an easy (and strong) response variable to measure Cofounding factors (salinity and nutrients; flow and residence time)

What are the relevant gaps and uncertainties in our understanding of the relationship between drivers/stressor and indicator response? Teasing out nutrient loading versus residence time Role of Caloosahatchee in red tides

Could our use of this indicator be improved to address additional drivers/stressors? Yes – can help to optimize flow regimes in different conditions

Next steps? River and red tides Assemblage shifts versus flow