Transcript Eight Years of Research in Little Lagoon at a Glance

Eight Years of Research in Little
Lagoon at a Glance
Justin D. Liefer
Personnel and Projects
Dr. Hugh MacIntyre
Dr. Justin Liefer
Dr. Lucie Novoveska
(all formerly of USA
and Dauphin Island Sea
Lab)
Dr. Alice Ortmann
Dr. Kyeong Park
Dr. Ruth Carmichael
Dr Bezhad Mortazavi
Rebecca Bernard
Jennifer Anders
Dr William Burnett Dr Richard Peterson
Dr Richard Viso
Kirstin Eller
Ni Su
•
•
•
•
Funding
Alabama Department of
Conservation and Natural
Resources (2006-2009)
National Science
Fourndation (2005, 20112014
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
Trulia.com
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
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
Total Phosphorus (uM)
Total Nitrogen (uM)
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 temperaturedependent
Nutrients from Sediments
• 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
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 Pseudonitzschia or red tides from Florida, but risks of
a stagnant lagoon seem greater.