Presentation is loading. Please wait.

Presentation is loading. Please wait.

PHYTOPLANKTON COMMUNITY STRUCTURE AND THE PHYSIOLOGICAL ECOLOGY OF THE TOXIC, BLOOM-FORMING DIATOM PSEUDO-NITZSCHIA SPP. IN COASTAL ALABAMA Justin D. Liefer.

Similar presentations


Presentation on theme: "PHYTOPLANKTON COMMUNITY STRUCTURE AND THE PHYSIOLOGICAL ECOLOGY OF THE TOXIC, BLOOM-FORMING DIATOM PSEUDO-NITZSCHIA SPP. IN COASTAL ALABAMA Justin D. Liefer."— Presentation transcript:

1 PHYTOPLANKTON COMMUNITY STRUCTURE AND THE PHYSIOLOGICAL ECOLOGY OF THE TOXIC, BLOOM-FORMING DIATOM PSEUDO-NITZSCHIA SPP. IN COASTAL ALABAMA Justin D. Liefer

2 Outline I.Introduction I.Interaction with LLPS II.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  Findings I.Occurrence Pseudo-nitzschia in Alabama waters II.Seasonal patterns in nutrients and grounwater III.Seasonal patterns in Pseudo-nitzschia and other phytoplankton IV.Toxicity of Pseudo-nitzschia I.Conclusions

3 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.

4 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

5 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

6 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)

7 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

8 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 AP Texas PWD ADPH

9 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

10 Pseudo-nitzschia in Alabama Pseudo-nitzschia rarely described along NE Gulf Coast Notable exceptions: Liefer et al. 2009; MacIntyre et al. 2011

11 Key Questions I.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?

12 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

13 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

14 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 DIPB LLP DIEE GSP GSPB OBAP Liefer et al. 2009

15 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. Local Groundwater Level

16 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

17 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 Nutrients Freshwater

18 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

19 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.

20 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)

21 Two Different Nutrient Seasons Winter and Spring  Low temp  High Groundwater  Low total nutrients  Available nitrogen is higher and variable Summer and Fall  High temp  Low GW discharge  High total nutrients  Available nutrient consistently low Jun 07 Dec 07 Jun 08 Dec 08 Jun 09 Dec 09 Jun 10 Salinity 1 3 Sites

22 Jun 07 Dec 07 Jun 08 Dec 08 Jun 09 Dec 09 Jun 10 Temperature (°C) Mean Chl a (μg l -1 ) Cyanobacteria-dominated Diatom-dominated  Winter/spring, diatoms dominate, phytoplankton low  Cyanobacteria dominante, phytoplankton high, oxygen low Benthic GW Two Regimes for Phytoplankton and nutrients Benthic nutrient regime GW nutrient regime 1 3 Sites

23 Winter and Spring  Nutrients are low, but more of them are available  Groundwater controls salinity and nitrogen  Diatoms dominate Groundwater Detritus Phytoplankon on the bottom N P

24 Summer and Fall  Nutrients are high in the lagoon  Nutrients likely come recycling of detritus (dead stufff)  Cyanobacteria (blue-green algae) dominate Groundwater Detritus Phytoplankon on the bottom N P

25 Pseudo-nitzschia Blooms Occur in Winter and Spring Only Pseudo-nitzschia spp. log(cells l -1 ) Temperature (°C) Jun 07 Dec 07 Jun 08 Dec 08 Jun 09 Dec 09 Jun 10  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

26  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 Are These Blooms Toxic?

27 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 is  Saltier  Clearer  Has less phosphorus and silicate

28 Toxin can move up the food chain 2009 Shoreline Bloom  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

29 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

30 Summary and Implications

31 N + Disturbance Two 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

32 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

33 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 mammals  Known to be poisoned in other areas  Consumers of phytoplankton-eating fish  Low dose, chronic exposure is a concern for humans and wildlife Texas PWD Sinh Nhut Nguyen Fishbase Texas PWD C. Pabody

34 Thank You  Justin Liefer, jliefer@disl.org  Check the LLPS website (www.littlelagoon.org) for research updates


Download ppt "PHYTOPLANKTON COMMUNITY STRUCTURE AND THE PHYSIOLOGICAL ECOLOGY OF THE TOXIC, BLOOM-FORMING DIATOM PSEUDO-NITZSCHIA SPP. IN COASTAL ALABAMA Justin D. Liefer."

Similar presentations


Ads by Google