Eight Years of Research in Little Lagoon at a Glance

Justin D. Liefer

Personnel and Projects

Dr William BurnettKirstin EllerNi Su

Dr Bezhad MortazaviRebecca BernardJennifer Anders

Dr Richard PetersonDr Richard Viso

Dr. Hugh MacIntyreDr. Justin LieferDr. Lucie Novoveska(all formerly of USA and Dauphin Island Sea Lab)Dr. Alice OrtmannDr. Kyeong ParkDr. Ruth Carmichael

Funding•Alabama Department of Conservation and Natural Resources (2006-2009)•National Science Fourndation (2005, 2011-2014•SeaGrant (2011-2013)•National Oceanic and Atmospheric Administration

Water Quality and Eutrophication• Our interest in Little Lagoon

began with general scientific interest and a concern about “eutrophication”

• Eutrophication = Increase in nutrient supply to water bodies often resulting in a reduction of water quality.

• Defined by its effects– Hypoxia (loss of oxygen in the

water)– Harmful algal blooms (HABs, red

tides, pond scum, etc.)– Harmful bacteria (Fecal coliforms,

E. coli)– Large changes in ecosystem

Causes and Examples

• Large global increase due to human activity– Residential waste/sewage– Agricultural/fertilizer runoff– Industrial pollution

• Key Examples:– Mississippi Dead Zone– Chesapeake Bay– Lake Taihu, China

• One of the greates global environmental problems

Image: NOAA

Why would we be concerned about eutrophication in Little Lagoon?

What We Knew in 2006

1.Coastal Baldwin Co. has had some of the highest population growth rates in the nation over the last few decades

2.Highly agricultural region with very high rainfall rates that could produce runoff

3.Little Lagoon appeared to be a hot spot of a potentially harmful species of algae, Pseudo-nitzschia

Trulia.com

Seaotters.com

Key Questions

1. What are the sources and sinks for water and nutrients in Little Lagoon?

2. Is Little Lagoon undergoing eutrophication and what should (or can) be done about it?

3. What are the levels of E. coli in Little Lagoon and where do they come from?

4. Is there a harmful algae problem in Little Lagoon

Our Approach• Bi-weekly monitoring of water conditions,

nutrients, algae, and bacteria at 4 sites in collaboration with LLPS volunteers, 2007-2012

• Many research cruises in Little Lagoon and Lake Shelby, to test hypotheses, get detailed picture

• Sampling groundwater wells and aquifer measurements

• Experiments to test causes of toxicity in harmful algae and effects of grazing plankton on algae

How Little Lagoon Works • Primary source of water to Little Lagoon is submarine

groundwater discharge. The residence time of the lagoon is estimated to be 6-12 days.

• Discharge concentrated at ends, mainly east end and east canals

• Mixing at Little Lagoon Pass makes large gradient in salinity and water conditions over a short distance. This make the lagoon a great natural laboratory!

Image: Bill Burnett

Nutrient Inputs to Little Lagoon• Key nutrients for good growth and

eutrophication are nitrogen and phosphorus• If nutrients came from just groundwater or

runoff, we’d expect a direct relationship between salinity and nutrients

Instead we see two relationships

• Nitrogen comes from groundwater in when groundwater discharge is high

• Phosphorus in general and nitrogen in summer comes from another source

Nutrients from Sediments

• Nitrgogen in summer months (triangles) and phosphorus linked to temperatue

• This looks like recycling of nutrients from sediments at the bottom of lagoon

• Bacteria eating dead material and recycling in temperature-dependent

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• No direct measurements of this

• Hypoxia in summer may play a role in nutrient release

• Also important to note that hypoxia occurs at night in summer in lagoon

Nutrients from Sediments

Dealing with Groundwater or Sediment Nutrients

• Groundwater may be a legacy issue, not practical to remediate

• Sediment nutrients are somewhat natural• Not conducive to management• Little Lagoon has a high, persistent source of

nitrogen, so it is more sensative to pollution from phosphorus-rich sources

• Risks from sewage or agricultural waste• Risk of a vicious cycle?

E. Coli in Little Lagoon

• Monitoring by LLPS has shown high levels, occasionally above regulatory limit

• Occurs in wet, summer conditions

• Highest levels occurred when pass was closed during Deep Water Horizon Spill

Sources of E. coli• E. coli can come from humans or wildlife.

Genetics of E. coli differs depending on source animal

• Monthly E. coli samples from Little Lagoon showed canals (possible inputs) had different E.coli than that found in the lagoon

• The primary source was unidentified, but it was not humans, dogs, or cows

Sources and Concerns

• Possible sources could be birds or “regrowth” from accumulated E. coli that are dormant and regrow in summer months, good conditions

• Bottom line: humans likely not the source, but Little Lagoon has good conditions for E. coli growth and humans can affect those conditons

• Little Lagoon is sensative to agricultural (manure) and human (sewage) waste. These sources should be monitored as development and population increases

Harmful Algal Blooms in Little Lagoon • Many potentially harmful species occur in Little

Lagoon, just like many other coastal waters

• No acute problems in lagoon due to algal toxins (i.e. large fish kills, poisoning of humans or wildlife)

• The levels of one toxin, domoic acid, are low in the lagoon and nearby waters

• Levels of domoic acid test in small fish during one bloom were 100 times below level for safe consumption

• However, little is known about chronic, low-dose exposure to domoic acid

Pseudo-nitzschia in Little Lagoon• Pseudo-nitzschia

initally piqued our interest in Little Lagoon

• Blooms occur and often produce low levels of toxin in Jan – May of wet years

• Little Lagoon is a great natural laboratory for studying it, and blooms linked to groundwater

Dealing with Pseudo-nitzschia• Pseudo-nitzschia is sort of like the

weed that grows first after you tear up soil

• Fast growing and likes disturbance (i.e. variability in nutrients or mixing)

• Prefers moderate temps and nutrient levels, most toxic when nutrients are low

• Prevention is unlikely since it’s due to water flow process, not human nutrient pollution

• Monitoring and more research are key

Other Harmful Algae• Little Lagoon is most nutrient-rich,

stagnant in summer. Good conditions for harmful cyanobacteria (blue-green algae) if flushing were reduced

• Red tides drift in from Florida and have caused problems locally

• Future monitoring by LLPS will play a key role in assessing these potential problems

Conclusions• Water quality in Little Lagoon is only mildly impaired.

Nutrients and algae are comparable to similar waters around Gulf of Mexico

• Groundwater and sediments are primary sources of nutrients, difficult to manage

• Hypoxia occurs in summer, may cause nutrient release. Restricted and not persistent

• Pseudo-nitzchia and its toxin occurs here, but seem unlikely to pose a human health ris

• Fecal coliforms and E. coli are often high, but do not appear to be from humans, dogs, or cows.

Thoughts for The Future• Little Lagoon has large, somewhat natural

source of nitrogen (groundwater). Phosphorus inputs likely to have the largest effect on eutrophication

• E. coli grows well in Little Lagoon, particularly in the summer of wet years

• Little Lagoon is sensitive to phosphorus inputs and human/agricultural waste

Thoughts for The Future

• E. coli problems or cyanobacteria problems could be exacerbated by closure of Little Lagoon Pass in summer

• Flushing of the lagoon likely helps keep algae and bacteria levels lows

• Flushing might also encourage Pseudo-nitzschia or red tides from Florida, but risks of a stagnant lagoon seem greater.