2001 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: R827637
Title: 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: Hahn, Intaek
Project Period: August 1, 1999 through July 31, 2002
Project Period Covered by this Report: August 1, 2000 through July 31, 2001
Project Amount: $399,335
RFA: Ecological Indicators (1999) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems


Coastal eutrophication that results from increases in nutrient supply is a critical problem worldwide, causing major changes in marine populations and communities. The overall goal of this proposal 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. 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 are five specific 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:

Objective 1: Testing Potential Species. Last year, we began to identify at least two tropical and two temperate species with the physiological characteristics needed for an indicator of nutrient supply. These characteristics include rapid nutrient uptake rates, a wide range of nutrient storage capacities, and the ability to tolerate a wide range of physical/chemical conditions. We targeted species that occur in a wide variety of habitats and are common within those habitats. Replicate samples of each species were collected from a variety of stations with known gradients of nutrients, when possible. A "good" indicator was defined as a species that has low within station variability in tissue nutrients, but high among station variability corresponding to differences in nutrient supply. Last year, we presented data from samples collected from 18 stations in Puerto Rico, 15 stations along the Caribbean coast of Panama, 18 stations along the Pacific coast of Panama, and 30 stations along the west coast of the United States. This year we added 6 stations in Kaneohe Bay, Oahu, HI; 9 stations in Caribbean Honduras, Central America; 10 stations along the coast of Washington in Puget Sound; and 7 stations around San Juan Island, Puget Sound, Washington.

Our results demonstrate that Acanthophora spicifera is a good candidate as an indicator within tropical marine habitats. This species has open branches and upright morphologies that extend into the water column to "sample" nutrients. It is able to sequester both N and P in proportion to supply. This is based on results of collections in Puerto Rico, Hawaii, and both coasts of Panama. Data from Honduras suggest that Dictyota divaricata is not an effective indicator of N supply, but it may be useful for P. For the west coast of the United States, Ulva spp and Enteromorpha spp were identified as good candidate species for southern California. Both species are common, and collections demonstrate that tissue N and P reflect varying nutrient regimes. However, Ulva and Porphyra perforata may be more useful than Enteromorpha in the Pacific Northwest as they are more common. In this region, Enteromorpha is largely restricted to freshwater seeps.

Objective 2: Accumulation of N and P in Tissue. To be a good indicator of nutrient supply, algae must have the ability to accumulate N and P in their tissues. To quantify this ability for the different species, we ran a series of identical experiments for each of the species in all study locations. Each experiment began with algae and water collected from a specific site. We conducted a 2 x 2 factorial experiment that varied the amount of N and P in the water and measured accumulation of N and P in tissues.

To date, experiments have been conducted in Puerto Rico, Honduras, the Eastern Tropical Pacific, Hawaii, Bodega (CA), and Friday Harbor Laboratories (WA). From these experiments, we determined that all the target species identified in Objective 1 were able to sequester N and P in response to nutrient N and P addition. However, nutrient history of algae from different locations is very important in determining the ability to sequester and store nutrients. Algae that are kept under low nutrient conditions have a greater ability to take up nutrients during nutrient pulses. We determined that the algae used in indicator experiments should be pre-conditioned in nutrient-poor water prior to deployment.

Objective 3: Establish Quantitative Relationships Between Environmental Conditions, N and P Supply, and Tissue N and P. We have begun to investigate the relationship between water flow and accumulation of N in the tissue of macroalgae. Field data from the collections, as well as the N versus P experiments, suggest that this is a very important factor influencing nutrient uptake and storage. Because our bioassay involves caging algae and placing them in the field to act as our nutrient sensor, quantifying the effects of changing water motion is important. We conducted an experiment where we varied water motion and water column nutrients in replicate experimental units, and we tested the effect of water motion on uptake by Enteromorpha intestinalis. Preliminary results show that increased water motion enhances uptake.

We also conducted several experiments that assessed the effects of nutrient supply, light, and salinity on Enteromorpha intestinalis tissue N and P content in southern California. Results showed that high N supply to the water column ameliorated the negative effects of reduced salinity. In addition, over the short term (3 days), reduced light had little effect on nutrient uptake rates. Thus, as long as supplies are high and light is at least moderate, Enteromorpha intestinalis can be used as a nutrient indicator in hyposaline estuarine habitats.

Objective 4: Develop Simulation Model. In Objectives 1 through 3, we are accumulating the data needed to develop and parameterize the simulation model. We have an initial model for Enteromorpha spp that predicts growth from nutrient supply. This will be updated as experimental results are received.

Objective 5: Field Test Indicator. Clearly, Objectives 1 through 4 need to be further along for us to do a field test of the indicator. At present, we can use it to determine relative differences between sites within a region. We have done so along known nutrient gradients in Puerto Rico and Hawaii. Alternate species have been tested in Honduras. We also have run a bioassay experiment in the Florida Keys, but the data have not been analyzed.

Future Activities:

We will continue efforts to achieve the goal of developing an indicator that quantifies nutrient supply to tropical and temperate marine ecosystems using the tissue nitrogen (N) and phosphorus (P) content of macroalgae.

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

Other project views: All 50 publications 24 publications in selected types All 22 journal articles
Type Citation Project Document Sources
Journal Article 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)
  • Full-text: EPA-Full Text PDF
  • Abstract: Wiley-Abstract
  • Other: ResearchGate - Abstract & Full Text PDF
  • Journal Article 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)
  • Full-text: ScienceDirect - Full Text HTML
  • Abstract: ScienceDirect-Abstract
  • Other: ScienceDirect - Full Text PDF
  • Journal Article 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)
  • Abstract: Springer-Abstract
  • Supplemental Keywords:

    stressor, effluent, ecology, marine science, measurement method., 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, nitrogen

    Progress and Final Reports:

    Original Abstract
  • 2000 Progress Report
  • Final Report