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Award Detail

Doing Business As Name:University of Maine
  • Robert S Steneck
  • (207) 563-8315
  • James A Estes
Award Date:08/22/2013
Estimated Total Award Amount: $ 574,617
Funds Obligated to Date: $ 574,617
  • FY 2013=$574,617
Start Date:09/01/2013
End Date:07/31/2018
Transaction Type:Grant
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.078
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Ocean Acidification: Century Scale Impacts to Ecosystem Structure and Function of Aleutian Kelp Forests
Federal Award ID Number:1316141
DUNS ID:186875787
Parent DUNS ID:071750426
Program:ANS-Arctic Natural Sciences
Program Officer:
  • Cynthia Suchman
  • (703) 292-2092

Awardee Location

Street:5717 Corbett Hall
Awardee Cong. District:02

Primary Place of Performance

Organization Name:University of Maine-Darling Marine Center
Street:193 Clark's Cove Road
Cong. District:01

Abstract at Time of Award

Marine calcifying organisms are most at risk to rapid ocean acidification (OA) in cold-water ecosystems. The investigators propose to determine if a globally unique and widespread calcareous alga in Alaska?s Aleutian archipelago, Clathromorphum nereostratum, is threatened with extinction due to the combined effects of OA and food web alterations. C. nereostratum is a slow growing coralline alga that can live to at least 2000 years. It accretes massive ?bioherms? that dominate the regions? rocky substrate both under kelp forests and deforested sea urchin barrens. It develops growth bands (similar to tree rings) in its calcareous skeleton, which effectively record its annual calcification rate over centuries. Pilot data suggest the skeletal density of C. nereostratum began to decline precipitously in the 1990?s in some parts of the Aleutian archipelago. The investigators now propose to use high-resolution microscopy and microCT imaging to examine how the growth and skeletal density of C. nereostratum has changed in the past 300 years (i.e., since the industrial revolution) across the western Aleutians. They will compare their records of algal skeletal densities and their variation through time with reconstructions of past climate to infer causes of change. In addition, the investigators will examine whether the alga?s defense against grazing by sea urchins is compromised by ongoing ocean acidification. The investigators will survey the extent of C. nereostratum bioerosion occurring at 10 sites spanning the western Aleutians, both inside and outside of kelp forests. At each site they will compare these patterns to observed and monitored ecosystem trophic structure and recent C. nereostratum calcification rates. Field observations will be combined with laboratory experiments to determine if it is a decline in the alga?s skeletal density (due to recent OA and warming), an increase in grazing intensity (due to recent trophic-level dysfunction), or their interactive effects that are likely responsible for bioerosion patterns inside vs. outside of forests. By sampling C. nereostratum inside and outside of forests, they will determine if kelp forests locally increase pH via photosynthesis, and thus buffer the effects of OA on coralline calcification. The combination of field observations with laboratory controlled experiments, manipulating CO2 and temperature, will help elucidate drivers of calcification and project how these species interactions will likely change in the near future. The project will provide the first in situ example of how ongoing ocean acidification is affecting the physiology of long-lived, carbonate producing organisms in the subarctic North Pacific. It will also be one of the first studies to document whether OA, ocean warming, and food web changes to ecological processes are interacting in complex ways to reshape the outcome of species interactions in nature. The project will support a postdoctoral investigator, and involve graduate and undergraduate students in the field work. The project will support research by a Native American undergraduate student and include outreach to coastal tribes and other members of the public.

Project Outcomes Report


This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Intellectual Merit: Climate change and predator loss are reshaping global ecosystems, yet the combined impacts of these stressors are rarely considered. Thus, over the 3-year duration of this project, we studied how kelp forests of the Aleutian Archipelago (Alaska) are being altered by the combined influence of ocean warming, ocean acidification, and the loss of a keystone predator (the sea otter). We focused on impacts to Clathromorphum nereostratum, a long-lived (millennia in some cases) calcifying alga that forms the structural base of the ecosystem and contains an archive of past temperature, structural integrity, and grazing intensity in its calcified matrix. Using field observations, we revealed that with the recent collapse of sea otter populations and resulting proliferation of sea urchins in the ecosystem, long-livedClathromorphum reefs are now being rapidly eroded by urchin grazing. In much the same way that tree rings have been used to reconstruct longer term historical events in terrestrial ecosystems, we then used urchin grazing scars that are faithfully preserved in Clathromorphum’s calcified matrix (with annual resolution) toreconstruct past grazing intensity in the ecosystem. Our reconstructionsestablish that reef bioerosion over the past half-century was strongly linked to the wax and wane of sea otters and the trophic cascade that ensued. We then went on to show experimentally that ocean warming and acidification have recently accelerated the process of reef bioerosion, and will continue to do so in the near-future. Our findings thus indicate that without sea otter recovery, Clathromorphumreefs will become extinct sooner than predicted from climate change alone. Such findings highlight the importance of large predators in nature. They also indicate that scientists will benefit from incorporating predator-prey interactions into climate change studies, given that such interactions can strongly magnify or attenuate the physiological impacts of climate change in marine food webs.


Broader Impacts:One postdoctoral researcher, three graduate students, and two undergraduate students received education experiences and technical training as part of this project. This group of trainees were comprised of ~65% females, with multiple individuals hailing from groups underrepresented in the sciences. To disseminate our findings, we have given numerous talks based on the results of our work, including public presentations (i.e., local science cafés and public forums), talks at scientific meetings (i.e., two Gordon Research Conferences and a Pew Charitable Trust meeting), departmental seminars at universities (University of Maine, University of California Santa Cruz, University of Michigan, Northeastern University, Harvard University) including non-traditional student universities (University of Massachusetts – Boston, Maine Maritime Academy), lectures to undergraduate classes (University of Maine, Colby College), and presentations to state and federal agencies (Maine Department of Marine Resources, U.S. State Department). To disseminate our findings more broadly, we collaborated with a documentary film maker (Compass Light Productions) to capture the essence of our work and make it available to the general public. We also helped publish an article through NSF’s Polar Program, and have worked closely with National Geographic Kids to disseminate our results in a cover story for the magazine (slated for release in August 2019). Several manuscripts (including one in review at Science) have been produced from this research. We anticipate their publication (and associated popular media articles) in 2019 and 2020.


Last Modified: 01/29/2019
Modified by: Robert S Steneck

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