2002 Progress Report: Phytoplankton Community Structure as an Indicator of Coastal Ecosystem Health

EPA Grant Number: R828677C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R828677
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EAGLES - Atlantic Coast Environmental Indicators Consortium
Center Director: Paerl, Hans
Title: Phytoplankton Community Structure as an Indicator of Coastal Ecosystem Health
Investigators: Paerl, Hans , Luettich Jr., Richard A. , Pinckney, James L.
Current Investigators: Paerl, Hans , Fries, Steven , Luettich Jr., Richard A. , Noble, Rachel T. , Pinckney, James L. , Valdes, Lexia M. , Wyrick, Pamela
Institution: University of North Carolina at Chapel Hill , Texas A & M University
Current Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Hiscock, Michael
Project Period: March 1, 2001 through February 28, 2003
Project Period Covered by this Report: March 1, 2001 through February 28, 2002
RFA: Environmental Indicators in the Estuarine Environment Research Program (2000) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Water , Ecosystems


The objectives of this research project are to: (1) develop broadly applicable, phytoplankton-based indicators of estuarine and coastal ecological condition; and (2) link these indicators to nutrient and physical-chemical forcing features and remote sensing analyses of water column optical properties.

Progress Summary:


The Atlantic Coast Environmental Indicators Consortium (ACE INC), “Phytoplankton Community Structure as an Indicator of Coastal Ecosystem Condition” component has been operational since April 2001. All aspects of the proposed work plan are in place and coordinated with ongoing water quality and habitat monitoring programs on the Neuse River Estuary (NRE), (MODeling and MONitoring [MODMON]/Coastal Intensive Sites Network [CISNet] http://www.marine.unc.edu/neuse/modmon Exit and a ferry-based water quality monitoring program for the NRE and Pamlico Sound (PS) (http://www.ferrymon.org Exit ). These programs have served as the backbone for the collection of nutrient, photopigment (chlorophylls and carotenoid), productivity, water optical property turbidity, and physical data needed to characterize the structure, function, and environmental controls of indicator phytoplankton communities comprising the base of the estuarine food web. We have been collecting comprehensive diagnostic (of phytoplankton community composition) photopigment samples that will serve to establish a baseline of phytoplankton community composition against which we will be able to gauge trophic state and ecological change in response to a wide variety of environmental forcing features, including nutrient inputs, salinity (reflecting freshwater inputs and residence time), water clarity and other optical properties, zooplankton grazing, and toxic substances. We also have been collecting in situ hydrographic, dissolved oxygen, and water velocity data to allow calculation of the residence time in the system.

Photopigment indicators have proven to be highly sensitive diagnostic indicators of seasonal and interannual changes in hydrologic and nutrient inputs to these systems (Pinckney et al., 2001, 2002; Paerl et al., 2001; Paerl et al., 2002, Paerl et al., submitted). Our long-term vision of the regional deployment and interpretive use of photopigment indicators is shown in Figure 1. Note the strategic location of these indicators in the context of estuarine and coastal ecosystem function, resourcefulness, and service.

Figure 1. Roles of Diagnostic Photopigments as Indicators of Ecosystem Productivity, and Plant Community Composition in Response to Physical-Chemical Stressors in Estuarine and Coastal Waters

Chlorophylls and carotenoid photopigments are diagnostic for certain phytoplankton functional groups (i.e., diatoms, dinoflagellates, chlorophytes, cyanobacteria, cryptomonads). They are being used to identify and distinguish nutrient from hydrologically driven changes in phytoplankton community composition and activity in the NRE, PS, and the Chesapeake Bay. We have been able to utilize ongoing intensive data for this purpose in the NRE (1994-present), PS (1999-present), and the Chesapeake Bay (1993-present). During this period, these estuarine systems have experienced the combined stresses of anthropogenic nutrient enrichment, droughts (reduced flushing combined with minimal nutrient inputs), and in the NRE-PS since 1996, elevated hurricane activity (high-flushing accompanied by elevated nutrient inputs). These distinct perturbations have allowed us to examine impacts of both anthropogenic and natural stressors on phytoplankton community structure. Seasonal and/or hurricane induced variations in river discharge, and the resulting changes in flushing rates and hence, estuarine residence times, have differentially affected phytoplankton taxonomic groups as a function of their contrasting growth characteristics. For instance, the relative contribution of chlorophytes, cryptophytes, and diatoms to the total chl a pool coincided with, and was therefore enhanced by, periods of elevated river flow in the NRE. It is hypothesized that these effects are a result of the efficient growth rates and enhanced nutrient uptake rates of these groups. Cyanobacteria, however, demonstrated greater relative biomass when flushing was minimal and residence times were longer, specifically during the summer (see Figure 2).

Figure 2. Concentrations of Chlorophyll a (µg Chl a L-1) Contributed by Chlorophytes, Cyanobacteria, and Dinoflagellates. Values were derived using Chemical Taxonomy (CHEMTAX) for surface water at a mesohaline location (Station 120, see Figure 2) of the NRE during 1994-2000. Data were collected biweekly and were extrapolated temporally. White areas indicate instances where data were not collected. CHEMTAX data were plotted along with freshwater discharge at the head of the estuary. The dates of landfall of the four major hurricanes that significantly have affected flow since mid-1996 are shown.

Further evidence that changes in hydrologic conditions have significantly altered phytoplankton community structure is provided by the observed historical trends in dinoflagellate and chlorophyte abundance in the NRE. Both decreases in the occurrence of winter-spring dinoflagellate blooms and increases in the abundance of chlorophytes coincided with the increased frequency and magnitude of tropical storms and hurricanes since 1996. The relatively slow growth rates of dinoflagellates may have led to their reduced abundance during these high river discharge events. These results indicate that phytoplankton composition has been altered since 1994 in conjunction with major hydrologic changes; specifically, hurricanes accompanied by floods. These phytoplankton community changes could potentially have altered trophodynamics and nutrient cycling in the NRE during these years (see Figure 3).

Figure 3. Regional Means Standard Error (1995-2000) for chl-a (mg m-3) and the Relative Abundance (fraction chl-ataxa) of Phytoplankton Groups Determined by CHEMTAX. One approach to developing indicators from measurements of phytoplankton biomass and composition is to define the "average" conditions, as shown above, and then conduct analyses of deviations (seasonal, regionally, interannually) in relation to differences in environmental forcing functions and patterns of primary production.

The reconstructed taxonomic composition for the Chesapeake Bay (see Figure 3 and the Chesapeake Bay Component Study) also shows strong contrasting responses between dominant phytoplankton groups during the spring and summer because of the variability of freshwater flow and nutrient loading. This pattern is strongest in the spring-early summer, wherein high-flow alleviates N limitation of the mid-to lower estuary and supports diatom blooms in the spring, and sometimes in the summer. Low flow produces improved photic conditions but causes an expanded zone of N limitation in the main stem of the Chesapeake Bay during the summer, thereby changing phytoplankton dominance to those groups that can efficiently grow under these conditions.

Two autonomous profiling platforms have been deployed in the NRE. These platforms are designed to add to the archive of data by automatically taking complete profiles of the water column several times per day at key locations in the estuary. Figure 5 presents a sample of data from one of these platforms. Graduate student Nathan Hall is using this data to examine the vertical distribution of phytoplankton in the mesohaline region of the NRE. As shown in Figure 4, the vertical distribution of chlorophyll often is complex, which could confound accurate assessments of water column chlorophyll by surface measurements, such as remote sensing techniques. Additionally, data from the automated vertical profilers has revealed that diurnal vertical migration is a prominent feature of the vertical distribution of phytoplankton in the mesohaline region of the NRE. Figure 5 shows chlorophyll depth distributions from 1 week in June of 2002, when diurnal vertical migration was apparent. Time-series analysis techniques revealed that diurnal vertical migration was a prominent feature of the depth distribution of chlorophyll during the late spring through late fall, but not during the winter or early spring. A temporal correlation between the occurrence of diurnally vertical migrating phytoplankton, and time periods when bottom water inorganic nitrogen exceeded surface water inorganic nitrogen concentrations, suggests a relationship between diurnal vertical migration and nitrogen deficiency in the photic surface waters. Thus, the presence of diurnal vertical migrating phytoplankton possibly could be used as an indicator of surface water nitrogen deficiency. We will be incorporating Nathan Hall’s findings in modeling efforts aimed at improving predictive phytoplankton responses to physical-chemical forcing features in this and other estuarine systems. Graduate student Benjamin Peierls is examining the spatiotemporal relationships between phytoplankton community structure and function and bacterial (heterotrophic) production dynamics in the estuary. In particular, he is examining potential linkages between changes on phytoplankton community composition (i.e., blooms) and potential microbial shifts playing key roles in nutrient and oxygen cycling (i.e., hypoxia/anoxia) in these waters. Graduate student Janelle Reynolds-Fleming is working with the 3-dimensional, finite difference Environmental Fluid Dynamics Code (EFDC) model to simulate hydrodynamic conditions in the NRE. The model was calibrated with MODMON/CISNet data from 1998-2000 by the U.S. Environmental Protection Agency (EPA) Region 4 to provide assistance to the state of North Carolina in its efforts to develop a nutrient Total Maximum Daily Load (TMDL) for the NRE. We have completed an independent validation study with the model and found that it compares well with salinity and velocity data from two bottom mounted conductivity temperature-depth and Acoustic Doppler Current Profiler (ADCP) moored on opposite shores of the upper NRE during 1999-2000. Regressions between model data and field data suggest that the model explains 78 percent of the variability seen in the field data. The model presently is being used to study transit time and flushing rates over a variety of discharge scenarios in the system.

Figure 4. Time Series of Physical and Chl-a Data Near the Bend in the NRE.

Figure 5. Depth Distribution of Chlorophyll From an Automated Vertical Profiler. Values are percent of total water column chlorophyll in each 10 cm depth bin.

Dr. Lexia Valdes has been involved in establishing and analyzing a long-term database of diagnostic phytoplankton photopigments for the NRE-PS. She also is collaborating with L. Harding and Jason Adolph, University of Maryland (UMD)-Horn Point Environmental Laboratories (HPEL) to develop and analyze parallel databases for the Chesapeake Bay and the NRE-PS system to examine and evaluate the interactive affects of anthropogenic nutrient enrichment and natural forcing features, including large storm events, flooding, and droughts on the structure and function of estuarine phytoplankton communities. We are planning several publications that will comparatively examine large-scale ecosystem responses to these forcing features in both systems. We are working closely with L. Harding (UMD-Civil Engineering and Environmental Science [CEES]), P. Tester National Oceanic and Atmospheric Administration/National Ocean Service ([NOAA]/[NOS]), and R. Lunetta (EPA) to utilize field-based photopigment indicator data for calibrating and verifying remotely sensed assessments of phytoplankton production and community structure for the NRE-PS. To this end, aircraft-based flyovers ([Sea-viewing Wide Field-of-view], Airborne Visible/Infrared Imaging Spectrometer, and Light Detection and Ranging) have been initiated for PS and adjacent subestuaries. These flyovers closely parallel and complement similar efforts in place in the Chesapeake Bay (see CB-ACE INC/NASA Component, L. Harding), with the objective being a data set enabling us to examine comparative ecosystem responses to physical-chemical forcing features. These efforts will be extended to smaller estuarine systems (North Inlet, Galveston Bay, Plum Island Sound) in Years 2-4 of the project. We also are interacting with several of the companion EaGLe projects (PEER, CEER, Great Lakes Environmental Indicators) to set the stage and framework for incorporating photopigment-based indicators as routine measures of productive and trophic state of the planktonic components of coastal ecosystems.

Coupled Physical-Biological Studies: NRE-PS Component. ACE INC field sites were chosen to provide a range of residence times from long (the NRE-PS) to short (Plum Island Sound). In the NRE, relatively little quantitative analysis has been performed to establish residence time as a function of discharge or position in the estuary. We recently have completed lagged correlation analyses of observed discharge at Streets Ferry and observed salinity at several locations along the axis of the NRE. These indicate mean travel times of 18.4 days at New Bern, 29.5 days at U.S. Coast Guard Marker, and 11 days and 31.4 - 33 days at station 95. We are in the process of setting up the three-dimensional circulation model EFDC for the system to allow more detailed analysis of residence time as a function of river discharge.

The use of aircraft for the remote sensing of biological pigments requires assumptions or knowledge concerning the vertical structure of biological populations/pigments in the water column. We have collected nearly 1 year of continuous vertical profiles of water column hydrography (salinity, temperature, turbidity) and in situ chl-a fluorescence. These profiles reveal strong diurnal vertical migration of the chl-a source, as well as close correspondence between chl-a levels and mixing events. We have begun analysis of this data to provide insight into its implication for remotely sensed pigments.

Contributions to State of Knowledge. The pigment-based and associated physical-chemical indicators being developed and applied in this component project already have proven useful and applicable for evaluating ecosystem and regional responses to a variety of environmental stressors, including nutrient loads, changes in hydrologic characteristics (salinity, circulation), large-scale frontal passages (i.e., “noreasters”), and major storms including hurricanes (Paerl et al., 2001; Paerl et al, 2002; in preparation). In addition, they offer great promise as a data source for development, verification, and modification of remote-sensing of plankton production and community structure of a range of estuarine and coastal water bodies regionally and nationally.

Notable Accomplishments. Hans W. Paerl was awarded the G. Evelyn Hutchinson Award of the American Society of Limnology and Oceanography (ASLO) at the Society’s annual meeting on February 8-14, 2003. The G. Evelyn Hutchinson Award has been presented annually by ASLO since 1982 to recognize excellence in any aspect of limnology or oceanography. The award is intended to symbolize the quality and innovations toward which the society strives and to remind its members of these goals. In lending his name to the award, Hutchinson asked that recipients be scientists who have made considerable contributions to knowledge, and whose future work promised a continuing legacy of scientific excellence. Emphasis in selection for this award is given to mid-career scientists for work accomplished during the preceding 5-10 years.

Training and Development. This project largely has focused on graduate and undergraduate student training during 2002-2003. In addition, project results have been used (via the Web sites http://www.aceinc.org Exit and www.marine.unc.edu/neuse/modmon Exit ) to train middle school and high school teachers and students. Web sites also have been used to instruct technicians and data managers.

Outreach Activities. Both Drs. Paerl and Luettich are involved in a variety of statewide and national scientific advisory and educational activities. These include serving on the North Carolina Department of Environment and Natural Resources Technical Advisory Committee (Luettich), North Carolina Division of Water Quality TMDL modeling group (Luettich), the North Carolina Water Resources Research Institute’s Technical Committee (Paerl), the Albemarle-Pamlico Sound Natural Estuary Program (NEP) Technical Advisory Committee (Paerl), and the North Carolina Environmental Management Commission (Paerl), providing technical and evaluative advice for a variety of stakeholder groups (Luettich and Paerl), including the Neuse River Foundation, the Pamlico River Advisory Board, the Wilson Bay Advisory Committee, and the Neuse Basin Council of Municipalities. Nationally, Paerl has been involved in an advisory role in the EPA-Chesapeake Bay Program, the Tampa Bay NEP, the Narragansett Bay Program (URI), and the Florida Bay Technical Advisory Committee. We are sharing technological developments and evaluative approaches/tools with scientific and agency (state-, federal, and international-level) colleagues, as well as public educational institutions, media, and resource (i.e., fisheries, tourism) managers. Examples of the utility, informational value, and application (scientific, management, and public education) of data thus far obtained can be found on the MODMON and FerryMon Web Sites.

Future Activities:

Future activities include analyses and interpretation of the long-term data being performed to develop qualitative and quantitative relationships between the abundance of specific phytoplankton functional groups and various estuarine chemical and physical variables. These analyses will yield information that will link the abundance of each phytoplankton functional group with a particular set of environmental conditions. This way, specific phytoplankton functional groups can be used as bioindicators of estuarine condition. Recent correlative statistical analyses revealed that phytoplankton functional groups in the NRE differed in their relationship to these variables. In addition, the extent of these associations varied with season. Because of the non-linear and complex associations between these biological, chemical, and physical variables, we will be using more robust data analysis procedures, including neural network analysis, to establish quantitative associations between these variables.

Journal Articles on this Report : 3 Displayed | Download in RIS Format

Other subproject views: All 135 publications 32 publications in selected types All 28 journal articles
Other center views: All 383 publications 99 publications in selected types All 88 journal articles
Type Citation Sub Project Document Sources
Journal Article Luettich RA, Carr SD, Reynolds-Fleming JV, Fulcher CW, McNinch JE. Semi-diurnal seiching in a shallow, micro-tidal lagoonal estuary. Continental Shelf Research 2002;22(11-13):1669-1681. R828677C001 (2002)
R828677C001 (2003)
R826938 (2000)
R826938 (2001)
R826938 (Final)
not available
Journal Article Paerl HW. Connecting atmospheric nitrogen deposition to coastal eutrophication. Environmental Science & Technology 2002;36(15):323A-326A. R828677C001 (2002)
R828677C001 (2003)
R828677C001 (Final)
R826938 (Final)
not available
Journal Article Paerl HW, Dyble J, Twomey L, Pinckney JL, Nelson J, Kerkhof L. Characterizing man-made and natural modifications of microbial diversity and activity in coastal ecosystems. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology 2002;81(1-4):487-507. R828677 (2001)
R828677 (Final)
R828677C001 (2002)
R828677C001 (2003)
  • Abstract from PubMed
  • Abstract: SpringerLink-Abstract
  • Supplemental Keywords:

    phytoplankton, estuarine and coastal indicators, photopigments, nutrients, hydrology, water quality, habitat, ecosystem and regional scale, management, physical factors, climatology, hurricanes, nutrient management, total maximum daily loads, TMDLs, modeling, remote sensing, ferry-based monitoring., RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, climate change, Air Pollution Effects, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, Environmental Engineering, Atmosphere, Ecological Indicators, atmospheric dispersion models, aquatic ecosystem, climate change effects, ecoindicator, fish habitats, coastal ecosystem, remote sensing, environmental monitoring, environmental measurement, assessment models, nutrient loading, climate, Choptank River, trophic effects, estuarine ecoindicator, estuarine ecosystems, environmental stress, water quality, ecological models, climate model, atmospheric chemistry, photopigment indicator

    Relevant Websites:

    http://www.aceinc.org Exit
    http://www.ferrymon.org Exit
    http://www.marine.unc.edu/neuse/modmon Exit

    Progress and Final Reports:

    Original Abstract
  • 2001
  • Final Report

  • Main Center Abstract and Reports:

    R828677    EAGLES - Atlantic Coast Environmental Indicators Consortium

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R828677C001 Phytoplankton Community Structure as an Indicator of Coastal Ecosystem Health
    R828677C002 Trophic Indicators of Ecosystem Health in Chesapeake Bay
    R828677C003 Coastal Wetland Indicators
    R828677C004 Environmental Indicators in the Estuarine Environment: Seagrass Photosynthetic Efficiency as an Indicator of Coastal Ecosystem Health