Grantee Research Project Results
2006 Progress Report: Retrospective Analysis Of A Multi-Decadal Phytoplankton Time-Series In Naragansett Bay: Stressors, Resilience, Change, And Ecological Thresholds
EPA Grant Number: R832443Title: Retrospective Analysis Of A Multi-Decadal Phytoplankton Time-Series In Naragansett Bay: Stressors, Resilience, Change, And Ecological Thresholds
Investigators: Smayda, Theodore J. , Borkman, David G.
Institution: University of Rhode Island
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2005 through June 30, 2007
Project Period Covered by this Report: September 1, 2005 through December 31,2006
Project Amount: $296,574
RFA: Exploratory Research: Understanding Ecological Thresholds In Aquatic Systems Through Retrospective Analysis (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
A retrospective analysis of a 38-year (1959-1996) phytoplankton and plankton habitat time series, based on weekly observations in Narragansett Bay, was analyzed for identification of long-term changes in phytoplankton species composition, abundance and bloom timing (= phenology) and ecological thresholds associated with these changes. The ongoing analyses have focused on the identification of thresholds in climate variables (= NAO, Gulf Stream position, winter temperature) and anthropogenic-influenced stressors (=nutrient) that are related to observed long-term changes in Narragansett Bay phytoplankton abundance, species composition and bloom patterns.
Progress Summary:
The first year of our research focused on refining our statistical and time series analysis techniques and on presentations and discussion of initial findings with colleagues. Our first year of research took a two-pronged approach: a broad, phytoplankton functional group approach that 1) examined long-term changes in silica to nitrogen and silica to phosphorus ratios as related to selection of diatoms vs. flagellates, and 2) a species-specific approach that analyzed long-term changes in the abundance and bloom timing of key phytoplankton taxa. The two phytoplankton taxa of greatest interest were the ichthyotoxic flagellate Heterosigma akashiwo and the cosmopolitan coastal marine diatom Skeletonema costatum. The flagellate Heterosigma akashiwo has had a long-term decline that is related to a decline in ambient Narragansett Bay phosphorus concentration below a threshold of ca. 1 µM. In contrast to the pattern identified for Heterosigma, changes in the abundance and bloom patterns of the dominant Narragansett Bay diatom Skeletonema during 1959-1997 were related to climate variables, with a threshold in a winter weather index (the NAO; North Atlantic Oscillation) identified that acted as an ecological ‘switch’ between the classical winter-spring bloom that dominated the annual pattern in cold (- NAO winters) versus the summer bloom that dominated the annual pattern associated with warmer (+ NAO) winters. Thus far we have identified two key ecological thresholds: a nutrient concentration threshold for blooming of an ichthyotoxic flagellate (Heterosigma akashiwo) and a winter climate threshold that influences the annual bloom pattern timing. Comparative analyses of our results with other long-term phytoplankton time series in other North Atlantic coastal locations were facilitated by presentation of our results at an international meeting and workshop, co-organized by Dr. Smayda, in September 2006 (described in presentations, below)
Future Activities:
Future work will seek to verify the emerging concept that observed long-term changes in Narragansett Bay phytoplankton abundance, species composition and bloom timing are the result of recent changes that crossed ecologically meaningful thresholds in climate, particularly during winter, and in the concentration and ratios of anthropogenic nutrient additions.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Turner J, Borkman D, Libby P. Zooplankton trends in Massachusetts Bay, USA:1998-2008. JOURNAL OF PLANKTON RESEARCH 2011;33(7):1066-1080. |
R832443 (2006) |
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Supplemental Keywords:
estuary, climate, ecosystem health, time series, phytoplankton, zooplankton, algal blooms, stability, threshold, Rhode Island, RI, EPA Region 1, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, RFA, Aquatic Ecosystems & Estuarine Research, Ecological Risk Assessment, Aquatic Ecosystem, Ecology and Ecosystems, Environmental Monitoring, water quality, ecosystem indicators, riverine ecosystems, environmental history, Narragansett Bay, estuarine research, species interaction, anthropogenic impact, trophic interactions, aquatic ecosystems, anthropogenic stress, ecosystem stress, ecosystem response, ecological thresholds, climate change, NAO, Skeletonema, Heterosigma, HAB, harmful algae blooms, RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Air, Aquatic Ecosystem, Aquatic Ecosystems & Estuarine Research, Ecological Risk Assessment, Atmosphere, Air Pollution Effects, climate change, Environmental Monitoring, phytoplankton, environmental history, water quality, Narragansett Bay, species interaction, anthropogenic impact, estuarine research, ecological thresholds, ecosystem indicators, modeling ecosystem change, ecosystem stress, riverine ecosystems, ecosystem response, trophic interactions, aquatic ecosystemsRelevant Websites:
http://www.gso.uri.edu/phytoplankton/ Exit
http://www.narrbay.org/d_projects/plankton-tsv/plankton-tsv.htm Exit
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.