Grantee Research Project Results
2003 Progress Report: Physiology and Ecology of Macroalgal Blooms on Coral Reefs off Southeast Florida
EPA Grant Number: R830414Title: Physiology and Ecology of Macroalgal Blooms on Coral Reefs off Southeast Florida
Investigators: Lapointe, Brian E. , Barile, Peter J. , Yentsch, Charles S.
Institution: Harbor Branch Oceanographic Institution, Inc.
Current Institution: Harbor Branch Oceanographic Institution, Inc. , Plankton Research and Instruments
EPA Project Officer: Packard, Benjamin H
Project Period: October 14, 2002 through October 13, 2004 (Extended to October 13, 2005)
Project Period Covered by this Report: October 14, 2002 through October 13, 2003
Project Amount: $279,098
RFA: Ecology and Oceanography of Harmful Algal Blooms (2002) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water Quality , Water
Objective:
The objectives of this
research project are to: (1) use digital underwater video imagery to determine
seasonal (quarterly)
variation in growth of the invasive green seaweeds Codium isthmocladum, Caulerpa
verticillata, and Caulerpa brachypus at two reef sites (Princess Anne, North
Colonel's Ledge) in northern Palm Beach County; (2) analyze quarterly
tissue samples of the invasive seaweeds at the two reef sites for their carbon:nitrogen:phosphorus
contents (C:N:P ratios) and 15N (15N/14N) contents; (3) perform studies
on the photophysiology (P versus I curves, Photosynthetic Efficiency = Fv/Fm)
of the target species; (4) determine the relative importance of ammonium
versus
nitrate to the nitrogenous nutrition of the target species; and (5) perform
laboratory and field grazing assays to determine the potential for herbivores
to control these blooms.
Progress Summary:
Objective 1: Use of Digital Underwater Video Imagery To Determine Seasonal (Quarterly) Variation in Growth of Three Invasive Green Seaweeds at Two Reef Sites
We have been able to successfully track the seasonal growth patterns of the various green macroalgae using digital video imagery with the random point count method. The biotic cover data generated by this method indicated that C. verticillata was the dominant organism (approximately 60 percent cover) at both reef sites in winter 2003, but was replaced by a massive bloom (ranging from 60-90 percent cover) of the Pacific native C. brachypus var. parvifolia (referred hereafter as C. brachypus) in the spring, summer, and fall samplings at both reef sites. This research is important because it documented the expansion of this invasive species on reefs in northern Palm Beach County in 2003. We also have been able to quantify the presence of lesser abundant (< 10 percent cover) green macroalgae on these reefs, which include C. isthmocladum, Caulerpa racemosa, Caulerpa mexicana, and Caulerpa prolifera.
Objective 2: Analyze Quarterly Tissue Samples of the Invasive Seaweeds for
Their C:N:P Ratios and 15N Contents
We successfully analyzed the quarterly macroalgae samples from the two reef
sites for C:N:P ratios and 15N values. These data revealed a significant seasonal
shift for C. brachypus and C. racemosa from phosphorus-limited growth (N:P
ratios > 30) in the fall and winter to nitrogen-limited growth (N:P ratios < 30)
during the spring and summer. This seasonal pattern was supported by seasonal
shifts in the C:N ratio in C. brachypus at both reef sites from relatively
low values in the winter and fall (< 12) to higher values in the spring
(14-23) and summer (15-18) that are indicative of nitrogen limitation.
Seasonal trends also were apparent in the tissue 15N values. These values
ranged from approximately +5 to +9 o/oo in C. brachypus, C. racemosa, C.
verticillata,
and C. isthmocladum between winter and summer 2003, but decreased significantly
to values between +2 and +4 o/oo in the fall sampling. This pattern would suggest
seasonal variation in N sources to these blooms switching from sewage in the
winter, spring, and summer months to agricultural runoff in the fall, when
N loading from stormwater runoff is maximum.
Objective 3: Perform Studies on the Photophysiology of the Target Species
Our optical and photosynthetic measurements in 2003 confirm that C. isthmocladum and Caulerpa spp. collected from the two reef sites exhibit the kinetics of shade algae, i.e., high quantum yield for photosynthesis and low respiration (P:R=4-5). Light saturation for all species was less than 150 µmol photons m-2 s-1, a relatively low value characteristic of shade algae. The measured visible albedo is 5 percent, the result of high absorption by photosynthetic pigments. The maximum reflectance is at 570 nm for all the green species collected from the reef sites. All have strong absorption bands as a result of chlorophylls a and b (600-700 nm). The ratio of the two chlorophylls is somewhat higher than observed in terrestrial green plants but lower than that of oceanic green microalgae. The high quantum yield for photosynthesis is supported by measurements of the fluorescence yield (Fv = Fo/Fm = ~ 0.7), which approaches the theoretical maximum for all algae. The fluorescence yield measurement can be thought of as a surrogate to a nutritional index (i.e., nutrient replete as opposed to starved). Accordingly, these results support the hypothesis that these green macroalgae are not severely nutrient starved at the reef sites in northern Palm Beach County.
Objective 4: Determine the Relative Importance of Ammonium Versus Nitrate To the Nitrogenous Nutrition of the Target Species
In 2003, we collected and analyzed water samples from the reef sites for ammonium, nitrate, and soluble reactive phosphorus at quarterly intervals. These data will help in the design of laboratory experiments in Year 2 of the project to assess the relative importance of ammonium versus nitrate as N sources to these green macroalgal blooms.
Objective 5: Perform Laboratory and Field Grazing Assays to Determine the Potential for Herbivores To Control These Blooms
Investigations on the interactive effects of nitrogen availability, chemical defense compound production, and palatability of Caulerpa spp. to herbivores have benefited from the collaboration with chemical ecologist Valerie Paul of the Smithsonian Marine Station. Preliminary evidence suggests that the defensive compound Caulerpenyne may not be available at any of the study sites in the dominant macroalga C. brachypus in sufficient quantities to deter grazing by generalist herbivores (e.g., parrotfish), but may be important as an "activated defensive compound." Evidence for this hypothesis results from both laboratory extractions and field palatability bioassays utilizing reef icthyofauna.
Future Activities:
We will continue monitoring the invasive green macroalgal blooms at the two reef sites through the summer of 2004. We also will conduct field and laboratory experiments to better understand the importance of ammonium versus nitrate as N sources to these invasive blooms. Herbivory of Caulerpa spp. by specialist mesograzers will be evaluated in Year 2 of the project. We plan to present the results of our Ecology and Oceanography of Harmful Algal Blooms research project at the 13th International Conference on Aquatic Invasive Species to be held in Ireland in September 2004.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 33 publications | 11 publications in selected types | All 11 journal articles |
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| Type | Citation | ||
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Barile PJ, Lapointe BE, Capo TR. Dietary nitrogen availability in macroalgae enhances growth of the sea hare Aplysia californica (Opisthobranchia:Anaspidea). Journal of Experimental Marine Biology and Ecology 2004;303(1):65-78. |
R830414 (2003) |
not available |
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Lapointe BE, Barile PJ. Seagrass die-off in Florida Bay: an alternative interpretation. Estuaries 2004;27(1):157-164. |
R830414 (2003) R830414 (2004) |
not available |
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Lapointe BE, Barile PJ, Yentsch CS, Littler MM, Littler DS, Kakuk B. The relative importance of nutrient enrichment and herbivory on macroalgal communities near Norman’s Pond Cay, Exumas Cays, Bahamas: a “natural” enrichment experiment. Journal of Experimental Marine Biology and Ecology 2004;298(2):275-301. |
R830414 (2003) |
not available |
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Yentsch CS, Yentsch CM, Phinney DA, Lapointe BE, Yentsch SFW. The odyssey of new production. Journal of Experimental Marine Biology and Ecology 2004;300(1-2):15-30. |
R830414 (2003) R830414 (2004) |
not available |
Supplemental Keywords:
carbon, nitrogen, phosphorus, macroalgae, photosynthesis, fluorescence, herbivory, target species, laboratory grazing, field grazing, invasive green seaweeds., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Water, ECOSYSTEMS, algal blooms, Aquatic Ecosystem, Aquatic Ecosystems & Estuarine Research, Ecological Risk Assessment, Oceanography, Aquatic Ecosystems, Environmental Microbiology, Ecology and Ecosystems, nutrient enrichment, sewage outflows, nutrient dynamics, macroalgal blooms, coral reefs, benthic algae, bloom dynamics, macroalgal populations, nutrient kinetics, groundwater, coral-algal symbiosis, nitrogen, ocean outfalls, algal bloom detection, marine ecosystem, benthic studyRelevant Websites:
Progress 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.