Grantee Research Project Results
2002 Progress Report: Developing an Indicator for Nutrient Supply in Tropical and Temperate Estuaries, Bays, and Coastal Waters Using the Tissue Nitrogen and Phosphorus Content of Macroalgae
EPA Grant Number: R827637Title: Developing an Indicator for Nutrient Supply in Tropical and Temperate Estuaries, Bays, and Coastal Waters Using the Tissue Nitrogen and Phosphorus Content of Macroalgae
Investigators: Fong, Peggy
Institution: University of California - Los Angeles
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 1999 through July 31, 2002
Project Period Covered by this Report: August 1, 2001 through July 31, 2002
Project Amount: $399,335
RFA: Ecological Indicators (1999) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
Coastal eutrophication that results from increases in nutrient supply is a critical problem worldwide, causing major changes in marine populations and communities. The overall objective of this research project is to develop an indicator that quantifies nutrient supply to tropical and temperate marine ecosystems using the tissue nitrogen (N) and phosphorus (P) content of macroalgae as well as the nitrogen isotopic ratio. To complement the present suite of indicators used to measure eutrophication, this indicator is targeted to be especially useful in systems where nutrients are supplied in pulses or those where nonpoint sources of nutrients such as groundwater or fluxes from the benthos are important. There were five specific project objectives: (1) continue to identify and test potential species for use as indicators; (2) establish relationships between timing and magnitude of nutrient supply and accumulation of N and P in algal tissue; (3) establish quantitative relationships between environmental conditions, N and P supply, and tissue N and P; (4) develop a numerical simulation model based on experimental results that may be used as a "standard curve" for the indicator to hindcast nutrient supply in the field; and (5) field test the indicator.
Progress Summary:
Objectives 1 and 2 were accomplished in the first 2 years of the research project and have been summarized in annual reports for 2000 and 2001.
Objective 3: Establish Quantitative Relationships Between Environmental Conditions, N and P Supply, and Tissue N and P and Investigate the Usefulness of 15N as an Indicator of Nutrient Sources
For our bioassay, we proposed to culture algae under known nutrient conditions and then outplant subsamples in cages into estuaries to measure nutrient availability. Given this protocol, we need to quantify the effects of flow (reduced by cages) and initial nutrient status (controlled in culture) on the indicator's accuracy. A two-factor experiment varying water motion and algal nutrient status demonstrated a clear need for controlling both of these factors when developing a protocol for the bioassay. These preliminary results suggest that algae with depleted tissues are more sensitive to water nutrient supply, and therefore, would be more efficient indicators. In addition, we need a better understanding of flow speeds and their effects on uptake within cages used for outplanting.
An important characteristic for an indicator species in a complex nutrient environment is the ability to take up pulses of different forms of nitrogen simultaneously. Estuaries usually receive N in many different forms with high temporal and spatial variability. In a two-factor, fully crossed experiment, we exposed Enteromorpha intestinalis to different forms of labeled 15N for each of six different time intervals to assess differences in uptake. The alga took up NH4+, NO3-, and dissolved organic nitrogen (DON) simultaneously. This characteristic makes E. intestinalis a good choice as an indicator in waters with complex nutrient sources, like estuaries. In addition, our results suggest that 15N is a much more sensitive tool for assessing N accumulation in E. intestinalis tissue than NO3-, NH4+, or total N within a 24-hour time-scale.
To develop our bioassay further, we quantified the relative importance of water column versus sediment nutrient sources to macroalgae across a gradient of resource availability. The importance of these sources varied with their magnitude. Estuarine sediments were more important to the growth of E. intestinalis when water column N was low compared to when water column N was high, evidenced by the increase in algal growth when water nutrients were low and estuarine sediment was present. Furthermore, the magnitude of the effect of estuarine sediments on macroalgal growth appears to be related to the nutrient content of the sediments. Overall, growth was greatest when algae were incubated with sediments with the highest initial sediment N and P content.
To use algae as a bioassay, it is important to determine which of the primary nutrients (N or P) is most important in regulating growth and biomass. We tested for possible limitation by both N and P to determine if nutrient limitation varied between the more saline versus brackish portions of estuaries. We found that E. intestinalis collected from all sites spanning the gradient in water column nutrients was N limited. Once N was supplied in sufficient quantity, secondary P limitation occurred in some sites. Therefore, both N and P should be monitored using the bioassay.
We investigated the use of stable nitrogen isotopes (15N) as a bioassay to determine nutrient sources and sinks in estuaries. The underlying assumptions are that 15N values in the water reflect sources of N and that algae take up 15N in proportion to availability in a predictable manner. However, selection for 14N versus 15N atoms (fractionation) also must be considered. To our knowledge, no experiments of isotopic fractionation for macroalgae have been performed. To determine how different forms of dissolved inorganic N (DIN) are fractionated during uptake, we conducted two laboratory experiments that: (1) varied 15N with constant concentration of NO3- or NH4+; and (2) held 15N constant and varied concentrations of either NO3- or NH4+. Our experiments demonstrate that E. intestinalis has great potential as a useful tool for determining nutrient sources as fractionation did not occur; thus, it may be possible to use macroalgal nutrient content and isotopic composition as indicators of N source.
Objective 4: Develop Simulation Model
We have accumulated the data needed to develop and parameterize the simulation model for E. intestinalis for southern California, and much needed for Ulva expansa for the rest of the West Coast of the United States. We are in the process of expanding our initial model that predicts growth from nutrient supply. This will be updated as experimental results are incorporated. Our next objective is to conduct the same experiments listed above in a tropical region. We plan to conduct these experiments in Puerto Rico this spring.
Objective 5: Field-Test Indicator. We conducted a large-scale field experiment in three estuaries in southern California to test our bioassay technique. We deployed the bioassays in both wet and dry seasons; although, unfortunately, this year was the driest year on record for southern California. We also deployed experimental units in 10 locations in each of the 3 estuaries to capture the estuarine gradient from head to mouth. Preliminary results suggest that the gradient in freshwater influence is not reflected as a nutrient gradient. Algal tissue N and P did not vary in a predictable manner based on either freshwater inflow, or water column nutrient sampling at a snapshot in time. Tissue N in algae increased at all stations, in all estuaries, and in all seasons. This suggests that these systems were highly enriched year round. In addition, 15N in algal tissue increased throughout the estuary, suggesting that an enriched N source, such as groundwater, entered the entire estuary. It will be essential to repeat this experiment in a year that is not so dry to determine if N sources change between wet and dry years.
Future Activities:
We will continue to: (1) establish quantitative relationships between environmental conditions, N and P supply, and tissue N and P; (2) develop a numerical simulation model based on experimental results that may be used as a "standard curve" for the indicator to hind cast nutrient supply in the field; and (3) field test the indicator.
Journal Articles on this Report : 13 Displayed | Download in RIS Format
Other project views: | All 50 publications | 24 publications in selected types | All 22 journal articles |
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Type | Citation | ||
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Armitage AR, Fong P. Gastropod colonization of a created coastal wetland: potential influences of habitat suitability and dispersal ability. Restoration Ecology 2004;12(3):391-400. |
R827637 (2000) R827637 (2001) R827637 (2002) R827637 (Final) |
Exit Exit |
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Boyer KE, Fong P, Vance RR, Ambrose RF. Salicornia virginica in a Southern California salt march: seasonal patterns and a nutrient-enrichment experiment. Wetlands 2001;21(3):315-326. |
R827637 (2002) R827637 (Final) R825381 (1999) R825381 (Final) |
Exit Exit |
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Boyer KE, Fong P, Armitage AR, Cohen RA. Elevated nutrient content of tropical macroalgae increases rates of herbivory in coral, seagrass, and mangrove habitats. Coral Reefs 2004;23(4):530-538. |
R827637 (2002) R827637 (Final) |
Exit Exit Exit |
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Boyer KE, Fong P. Co-occurrence of habitat-modifying invertebrates: effects on structural and functional properties of a created salt marsh. Oecologia 2005;143(4):619-628. |
R827637 (2002) |
Exit Exit |
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Boyle KA, Kamer K, Fong P. Spatial and temporal patterns in sediment and water column nutrients in a eutrophic Southern California estuary. Estuaries and Coasts 2004;27(3):378-388. |
R827637 (2002) R827637 (Final) R825381 (1999) R825381 (Final) |
Exit |
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Cohen RA, Fong P. Physiological responses of a bloom-forming green macroalga to short-term change in salinity, nutrients, and light help explain its ecological success. Estuaries and Coasts 2004;27(2):209-216. |
R827637 (2002) R827637 (Final) |
Exit |
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Cohen RA, Fong P. Nitrogen uptake and assimilation in Enteromorpha intestinalis (L.) Link (Chlorophyta): using 15N to determine preference during simultaneous pulses of nitrate and ammonium. Journal of Experimental Marine Biology and Ecology 2004;309(1):67-77. |
R827637 (2000) R827637 (2001) R827637 (2002) R827637 (Final) |
Exit Exit Exit |
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Fong P, Kamer K, Boyer KE, Boyle KA. Nutrient content of macroalgae with differing morphologies may indicate sources of nutrients for tropical marine systems. Marine Ecology Progress Series 2001;220:137-152. |
R827637 (2000) R827637 (2002) R827637 (Final) |
Exit Exit Exit |
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Fong P, Fong JJ, Fong CR. Growth, nutrient storage, and release of dissolved organic nitrogen by Enteromorpha intestinalis in response to pulses of nitrogen and phosphorus. Aquatic Botany 2004;78(1):83-95. |
R827637 (2002) R827637 (Final) |
Exit Exit Exit |
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Kamer K, Fong P. Nitrogen enrichment ameliorates the negative effects of reduced salinity on the green macroalga Enteromorpha intestinalis. Marine Ecology Progress Series 2001;218:87-93. |
R827637 (2000) R827637 (2002) R827637 (Final) |
Exit Exit Exit |
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Kamer K, Boyle KA, Fong P. Macroalgal bloom dynamics in a highly eutrophic southern California estuary. Estuaries and Coasts 2001;24(4):623-635. |
R827637 (2000) R827637 (2002) R827637 (Final) R825381 (1999) R825381 (Final) |
Exit |
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Kamer K, Fong P, Kennison R, Schiff K. Nutrient limitation of the macroalga Enteromorpha intestinalis collected along a resource gradient in a highly eutrophic estuary. Estuaries and Coasts 2004;27(2):201-208. |
R827637 (2002) R827637 (Final) |
Exit |
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Kamer K, Fong P, Kennison RL, Schiff K. The relative importance of sediment and water column supplies of nutrients to the growth and tissue nutrient content of the green macroalga Enteromorpha intestinalis along an estuarine resource gradient. Aquatic Ecology 2004;38(1):45-56. |
R827637 (2000) R827637 (2001) R827637 (2002) R827637 (Final) |
Exit |
Supplemental Keywords:
stressor, effluent, ecology, marine science, measurement method, California, CA, Florida, FL, Puerto Rico, PR, algae, algal growth, aquatic ecosystem, bays, coastal ecosystem, coastal environments, ecosystem indicators, environmental monitoring, estuaries, estuarine ecosystems, hydrological stability, macroalgae, marine ecosystem, nitrogen, nutrient supply, nutrient transport, phosphorus, risk assessment, stressors, tropical ecosystems., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Effects - Environmental Exposure & Risk, Ecology and Ecosystems, coastal ecosystem, aquatic ecosystem, environmental monitoring, hydrological stability, nutrient supply, nutrient transport, risk assessment, bays, marine ecosystem, algae, estuaries, stressors, macroalgae, tropical ecosystems, algal growth, coastal environments, Puerto Rico, effluent, ecosystem indicators, estuarine ecosystems, tropical storms, water quality, phosphorus, ecological indicators, California (CA), Florida, nitrogenProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.