Little Lagoon Preservation Society

Research and Monitoring Results and Interpretations

Prior Projects

MacIntyre, H.L., “Little Lagoon as an Incubator Site for the Harmful Bloom-Forming Diatom, Pseudo-nitzschia sp.”, Alabama Department of Conservation and Natural Resources, 2005-2006  $24,500

MacIntyre, H.L.: “Purchase and Testing of an AutoLab Underway Nutrient Analyzer for Real-Time Mapping during Harmful Algal Blooms”, Alabama Department of Conservation and Natural Resources, 2006 – 2007  $28,360

MacIntyre, H.L., “A Volunteer Phytoplankon Monitoring Network”, NOAA National Coastal Data Development Center/NOAA Northern Gulf Institute, 2007-2009  $34,000

MacIntyre, H.L.: “Potential anthropogenic triggers for toxicity in the Harmful Algal Bloom diatom Pseudo-nitzschia sp. in Little Lagoon, Alabama”, Alabama Center for Estuarine Studies, 2007-2009  $63,185

Total: $150,075

 
Current Research Results

Abstract

Trend analysis of pigment and nutrient data suggest that groundwater inputs are a key driver of phytoplankton diversity and abundance. Abundance of phytoplankton is strongly correlated with nutrient concentrations in the lagoon, reflecting relatively slow flushing. Sampling has documented blooms of the diatoms Pseudo-nitzschia spp. (potentially toxic) and Skeletonema spp. Potentially-toxic dinoflagellates Karenia brevis and Dinophysis caudata have also been detected in low numbers. Future hypothesis testing will focus on identifying significant groundwater inputs, quantifying their relative contribution to nutrient loads, and testing the relationships between discharge and the abundance and types of phytoplankton occurring in Little Lagoon.

In addition to support from ADCNR and MBNEP, our monitoring effort has been supported by NOAA Southeastern Phytoplankton Monitoring Network (SEPMN), and by Alabama Department of Environmental Management (ADEM). These partnerships have facilitated LLPS gaining a reputation as a “cutting edge” water-quality monitoring group with significant findings and credibility gains amongst our peer-groups and with City, County, State and Federal governments. City, County, and State officials/politicians regularly attend our quarterly membership meetings, which have featured subject-matter experts from DISL, University of South Alabama, and University of Alabama to date. 

 

 

 

Lagoon Residents

Analysis of phytoplankton, collected in bi-weekly sampling as part of NOAA’s Phytoplankton Monitoring Network, shows that bloom-forming diatoms (including the potentially-toxic Pseudo-nitzschia sp.) are common in the lagoon

 

 

 

 

  

 

 

Temporal Characterization

Four sites in the lagoon are sampled bi-weekly for a suite of physical, chemical and biological parameters.  Differences between sites are generally low compared to differences over time.  However, inputs of nutrient-rich, fresh water occur at Site 1 are not seen at all sites.

 

 

  

 

 

 

 

   

 

 

 

 

Spatial Characterization

There are consistent physical, chemical and biological gradient in the lagoon.  These are shown, reduced to the first component in a principal components analysis of data from 50 stations, collected on 7/13/07.  The first component explained 70% of the variability in the data.  The sites sampled biweekly by LLPS and DISL are also marked.  

 

 

 

 

Nitrate varies with salinity. Phosphate doesn’t.

The appearance of nitrate-rich and relatively fresh water at Site 1 is obvious (left).  Nitrate concentrations at the other sites were low and independent of salinity.   Phosphate concentrations (right) did not vary with salinity at any of the sites.

 

 

 

 

 

 

Microalgal biomass varies with nutrients

 Microalgal biomass is highly correlated with total nitrogen and phosphorus.  The correlation coefficient (R) is higher for phosphorus.  High correlation suggests flushing low relative to growth.  No hypoxia yet detected in surface waters.

 

 

 

 

 

 

Strong seasonal cycle in nutrients

Total nitrogen (TN) and phosphorus (TP) are correlated with temperature.  Total N and P are not correlated with salinity except at east end of lagoon (Site 1)

   

 

 
     

 

Nitrate is correlated with freshwater inputs

Nitrate is available for plant growth (most TN is not).  Concentrations are highest at east end of lagoon by canal.  Freshwater pulses are a source of nitrate. 

 

 

 

     

Nitrate is high in groundwater

Nitrate concentrations in groundwater are very high.  Estimated transport by groundwater to Gulf of Mexico is 50% of transport through Mobile Bay (Dowling et al. 2004). 

 

 

 

     

Nutrients are also very high in the sediments

Sediment concentrations are  about 1,000 times higher than in water.  Annual temperature-dependence in water is typical of release from sediment. 

 

   
     

Lagoon is a hot-spot for a toxic diatom, Pseudo-nitzschia spp.

Blooms in lagoon have been toxic but no obvious domoic acid intoxication/mortality detected.  Bloom density is correlated with discharge from Baldwin County aquifer.

 

   
     

Fecal coliform bacteria are often high

A quarter of samples are over the regulatory threshold (200 colony forming units L-1).  Highest values were c. 2,500 CFU L-1.  No correlation with temperature, salinity, nutrients, microalgae. 

 

 

 

     

Questions for future research

What mechanisms underlie variability in nutrients in the lagoon?

What are the most likely origins of the nutrients?

What is the relationship between nutrients, flushing and microalgal community composition (i.e. Pseudo-nitzschia spp. vs other species)?

What are the causes and consequences of toxicity in Pseudo-nitzschia spp?

What are the likely origins of the fecal coliform bacteria?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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