PHYTOPLANKTON COMMUNITY STRUCTURE AND THE

PHYSIOLOGICAL ECOLOGY OF THE TOXIC, BLOOM-FORMING DIATOM

PSEUDO-NITZSCHIA SPP. IN COASTAL ALABAMA

Justin D. Liefer

OutlineI. Introduction

I. Interaction with LLPSII. Why are we interested in nutrients (nitrogen, phosphorus)III. What are harmful algal blooms (HABs)IV. What is Pseudo-nitzschia

Study Goals and overview of results

FindingsI. Occurrence Pseudo-nitzschia in Alabama watersII. Seasonal patterns in nutrients and grounwaterIII. Seasonal patterns in Pseudo-nitzschia and other

phytoplanktonIV. Toxicity of Pseudo-nitzschia

I. Conclusions

Definitions• Algae –

– General (and old) term for a wide range of simple organisms that are similar to plants

– They do photosynthesis, making their own food using light. Includes seaweeds and phytoplankton

• Phytoplankton – – Microscopic, single-celled algae

(microalgae) that live in the water column.

– They act as the “plants” and base of the food web in oceans and lakes.

Disclaimers

The sky is not falling. This work is motivated by general scientific interest (DISL) and understanding of the local environment to help manage and protect it (LLPS)

The presence of toxins in the water or in fish does not mean that poison is imminent or even likely

I am showing interesting biological patterns that contribute to science in general, not assessing ecosystem health or tracking pollution

I am high-lighting potential areas of concern

Interaction with LLPS Volunteers from LLPS have collected bi-weekly samples

since June 2007. About 140 sampling trips, almost 1000 samples.

This has greatly assisted our research efforts aside from sampling help Local access and knowledge Oppurtunity for community outreach Educational opportunities

In turn, Little Lagoon is now very well-studied and will soon be well-represented in the scientific literature

Why Are We Interested in Nutrients? Phytoplankton (like plants) need nutrients (fertilizer) to grow.

Nutrient inputs can control the amounts and kinds of phytoplankton

Nitrogen (N) and phosphorus (P) are the most important nutrients

Silicate (Si) can also be important (diatoms)

Nutrients can be delivered from outside the system (river or groundwater discharge, runoff, sewage)

Nutrients can be produced internally (nitrogen-fixation, recycling by bacteria)

Difference between total nutrients and dissolved (available)

Harmful Algal Blooms (HABs)

A broad term for any proliferation of phytoplankton with potentialnegative consequences for the rest of the ecosystem or human health

An increasing global problem Nutrient pollution is widely believed to be the

cause of this increase Also due to invasive/exotic species

Can be “harmful” due to: Production of toxins Reducing oxygen in the water Physical damage (like clogging fish gills) geo.brown.edu

Pseudo-nitzschia, the toxic diatom A diatom (a group of phytoplankton) which occurs in

temperate waters globally

Can produce the neurotoxin domoic acid (DA). Production of the toxin varies, depends on conditions

DA accumulates in plankton, fish, and shellfish and can poison the animals that eat them

Domoic acid poisoning (DAP) is observed on the US west coast in birds and marine mammals after consuming toxic fish. Contamination often causes costly fishery closures

Amnesic shellfish poisoning (ASP) in humans. 1987, PEI poisoning event

APTexas PWD

ADPH

Features of Pseudo-nitzschia

A global concern Occurs in a variety of

systems Upwelling systems Estuaries Open ocean Oceanic fronts

Similarities in bloom conditions Pulses of nutrients Mixing Likes variable conditions A ruderal (weedy) strategy

Pseudo-nitzschia in Alabama

Pseudo-nitzschia rarely described along NE Gulf Coast

Notable exceptions: Liefer et al. 2009; MacIntyre et al. 2011

Key QuestionsI. When and where does Pseudo-nitzschia occur in

Alabama waters?

II. What are the seasonal patterns in water conditions and phytoplankton where Pseudo-nitzschia occurs?

III. What conditions control phytoplankton and promote blooms of Pseduo-nitzschia?

IV. What controls the toxicity of Pseudo-nitzschia? Does the toxin move up the food chain?

Groundwater discharge promotes Pseudo-nitzschia blooms at low temps

There is a local “hot-spot” for Pseudo-nitzschia blooms at Little Lagoon. Likely

caused by groundwater

Domoic acid accumulates in small fish, even when the toxicity of

blooms is low

Local Pseudo-nitzschia produces toxin, especially when

salinity and light are high,

phosphorus and silicate are low

Overview

When and where does Pseudo- nitzschia occur in Alabama waters?

Pseudo-nitzchia monitored by Alabama Dept. of Public Health since 2004

Samples of Pseudo-nitzschia abundance at 7 coastal sites were from 2004 – Oct 2008 were examined

A local hot-spot for Pseudo-nitzschia

Pseudo-nitzschia occurs more frequently and often in greater numbersw at Little Lagoon Pass (LLP)

Little Lagoon is a local hot-spot for Pseudo-nitzschia blooms

DIP

B

LL

P

DIE

E

GS

P

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PB

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AP

Liefer et al. 2009

Groundwater and Pseudo-nitzschia

Groundwater discharge was the most important factor examined

Styx River is an estimate for local groundwater discharge

Groundwater and Pseudo-nitzschia were highly correlatated from Apr 15-May 15 (bloom season) in each year.

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Local Hydrogeology

Dowling et al. 2004

Surface Flow 2/3 of nitrate

Groundwater 1/3 of nitrate

Water table is highest near Little Lagoon

Very high nitrate (important source of nitrogen) in local groundwater

Large local discharge of groundwater/nitrate to Gulf of Mexico

Unlikely that this would not effect the biology of local waters

Groundwater Discharge is Unique Very high in nitrogen,

low in phosphorus

Diffuse, difficult to measure directly

May add nutrients without large flushing/drop in salinity, unlike rivers

Pseudo-nitzschia was shown to prefer high salinity (30.1 ± 3.2). LLP may have ideal combination of high nutrients and high salinity

River DischargeSubmarine Groundwater Discharge

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nts

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Seasonal patterns in phytoplankton and Pseudo-nitzschia

Preliminary work prompted closer look at Little Lagoon

Little Lagoon is a shallow, poorly-flushed coastal lagoon.

No river inputs. Connected to groundwater-fed lakes via canals

Determining conditions and phytoplankton dynamics in Little Lagoon

Approach

4 sites monitored bi-weekly from Jun 2007 – Jun 2010. Temperature, salinity, overall water conditions Nutrients Phytoplankton pigments

Pseudo-nitzschia monitored during April 2008 bloom and regularly at 2 sites from Jan 2009 – Jun 2010.

Groundwater is the source of freshwater to Little Lagoon

Patterns in freshwater to Little Lagoon follows patterns in groundwater

Surveys for Radon 222 (with W. Burnett, FSU), a conservative groundwater tracer, shows direct groundwater inputs and a high correlation with salinity (R = -0.745)

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Two Different Nutrient Seasons

Winter and SpringLow tempHigh GroundwaterLow total nutrientsAvailable nitrogen is

higher and variable

Summer and FallHigh tempLow GW dischargeHigh total nutrientsAvailable nutrient

consistently low

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Cyanobacteria-dominated

Diatom-dominated

Winter/spring, diatoms dominate, phytoplankton low

Cyanobacteria dominante, phytoplankton high, oxygen low

Benthic Benthic BenthicGW GW GW

Two Regimes for Phytoplankton and nutrients

Benthic nutrient regime

GW nutrient regime

13

Sites

Winter and SpringNutrients are low, but more of them are

availableGroundwater controls salinity and nitrogen Diatoms dominate

Groundwater

Detritus

Phytoplankon on the bottom

NP

Summer and FallNutrients are high in the lagoonNutrients likely come recycling of detritus

(dead stufff)Cyanobacteria (blue-green algae) dominate

Groundwater

Detritus

Phytoplankon on the bottomN P

Pseudo-nitzschia Blooms Occur in Winter and Spring Only

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GW-dominated periods (blue bars, diatom-dominated periods (yellow bars), toxic Pseudo-nitzschia blooms, and low temperatures all overlap

Does temperature or groundwater+nutrients drive blooms?

ND

Every bloom so far has produced low/moderate levels of toxin

Example from Apr 2008

Pseudo-nitzschia high across much of lagoon

Toxicity highest in Gulf Lower nutrients High light High salinity

PC 1 Score

-4.5 1.50-1.5-3

106105104103

Pseudo-nitzschiaspp. (cells l-1)

Toxicity (pg DA cell-1)

<1 1-2 5 1510<1 1-2 5 1510

3

Are These Blooms Toxic?

What Cuases The Toxicity?

Others have shown nutrient stress to cause toxicity in Pseudo-nitzschia

My results show the same, but also that light is important

Blooms are likely to be more toxic where water isSaltierClearerHas less phosphorus and silicate

Toxin can move up the food chain2009

ShorelineBloom

FM

LLBS

Bloom had low toxicity

Toxin detected in 98% of fish collected during bloom (shoreline seine)

Fish toxicity was low compared to poisonous events in other areas

CB

Implications of fish toxicity

Bloom of low toxicity was able to transfer toxin to higher trophic levels. Much higher cellular toxicity observed in other local blooms

Most fish collected are not considered primary consumers. Toxin was transferred at least 2 levels up the food chain

Texas PWD

Sinh Nhut Nguyen

Fishbase.org

Summary and Implications

May – Dec

Photos: Protist Information Server, WRoMS

High TempsLow Discharge

High Total Nutrients

Low TempsHigh Discharge

Low Total Nutrients

Jan – Apr

DiatomsCyanobacteria

Groundwater Discharge

Little LagoonNGOM

Groundwater Discharge

Little LagoonNGOM

N + DisturbanceTwo seasonal

phytoplankton/nutrient Seasons Groundwater discharge at low temps promotes

Pseudo-nitzschia blooms

Light and nutrient

stress promote toxicity

Low grazing pressure on Pseudo-nitzschia

Toxins can move up

the food chain

TP

Si

Domoic Acid Production

Regional considerations Local geology, population

growth, agriculture = higher groundwater nitrate in the future. Risks for future blooms

DA contamination unlikely for shellfish in fresher water (e.g. Mobile Bay oysters)

DA exposure should be considered when relaying oysters or attempting aquaculture in local high salinity waters

Probability of High Groundwater Nitrate

Nolan et al. 2002

Local health implications DA may pose a threat to

mullet and menhaden fisheries (herbivores)

Most likely threat is to wildlife such as birds or marine mammalsKnown to be poisoned in

other areasConsumers of

phytoplankton-eating fish

Low dose, chronic exposure is a concern for humans and wildlife

Sinh Nhut NguyenFishbase

Texas PWD

C. Pabody

Thank You

Justin Liefer, jliefer@disl.org

Check the LLPS website (www.littlelagoon.org) for research updates