| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | February 10, 2016 |
| Latest Amendment Date: | February 10, 2016 |
| Award Number: | 1623867 |
| Award Instrument: | Standard Grant |
| Program Manager: |
David Garrison
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | February 15, 2016 |
| End Date: | August 31, 2017 (Estimated) |
| Total Intended Award Amount: | $198,194.00 |
| Total Awarded Amount to Date: | $198,194.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 PROSPECT ST PROVIDENCE RI US 02912-9100 (401)863-2777 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Office of Sponsored Projects Providence RI US 02912-9093 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | BIOLOGICAL OCEANOGRAPHY |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Changes in the ecological structure, biodiversity and functioning of ecosystems have occurred in all types of habitats. Sometimes the change is so large and abrupt that the ecosystem switches to an alternate state, or regime, that persists for long periods of time (i.e. decades to millennia) such as the switch between a vegetated and desert ecosystem in the Sahara. Since regime changes may drastically alter the ecosystem goods and services provided to humankind, there is a practical as well as theoretical need to understand the conditions and drivers leading to tipping points between alternate regimes. To date, little is known about either the pre-conditions or drivers of regime change, particularly in subtidal habitats where long-term data on the ecological state of communities of interacting species prior to regime change is difficult to obtain. Most of the knowledge about tropical regime shifts in marine habitats has focused on shifts between corals and macroalgae even though these organisms represent only part of a species-rich ecosystem with many possible trajectories and outcomes of regime change. Consequently, the overarching goal of the proposed investigation is to test a conceptual model developed herein predicting how both El Niño and La Niña phases of the unusually strong 2016 ENSO (El Niño Southern Oscillation) may drive a regime shift in the Galapagos rocky subtidal at the whole community level. As the target community involves sponges as a key component, in addition to barnacles, Crustose Coralline Algae (CCA), corals, sea urchins, sea stars and predatory fish, the model tests predictions from the Sponge Reef Hypothesis (SRH), an emerging paradigm predicting that sponges may increasingly dominate space as corals decline from future climate change (representing a coral to sponge regime change). Preliminary data indicate that counter to the SRH, sponges declined during the unusually warm temperatures at the outset of the present ENSO in Galapagos subtidal communities. However, sea urchin predation on sponges and CCA appears to have accelerated at the same time, so manipulative field experiments are proposed to rigorously test and differentiate the effects of ENSO elevated temperature on sponge mortality from the effects of enhanced sea urchin predation on sponges. These experimental results will be evaluated in the context of actual, long-term (13-16 year) changes in the whole community obtained by quantitative re-sampling of the benthic community at 12 sites in the central Galapagos throughout the present ENSO. Re-sampling this baseline will also enable the analysis of indicators leading up to the hypothesized regime change. Broader educational impacts of the project will transpire at all levels from high school students to graduate students and the public.
Although regime changes have been described as abrupt shifts to alternate, persistent states in many ecosystems in response to natural or anthropogenic drivers, research on regime change in bottom-dwelling communities of tropical oceans has largely focused on a switch from coral-dominated to macroalgal- dominated regimes. This narrow focus overlooks potential influences of the diverse assemblages of sessile invertebrates such as sponges that share space on the hard substrate of reefs with corals and could proliferate as a new regime if corals are diminished. The SRH is an emerging community ecological paradigm that posits that sponges may increasingly dominate space as corals decline from future climate change and ocean acidification, yet it has not been rigorously tested. The exceptionally strong El Niño occurring in the Galapagos Islands presents a unique opportunity evaluate the potential for climate oscillations to create regime shifts at the community level and to test the SRH because subtidal benthic community structure has been quantified at least annually since 1999 at multiple sites in the central Galapagos Islands. Recent 2015 surveys indicated significant mortality of sponges at multiple sites coincident with the present El Niño warming, counter to the SRH. However, sea urchin predation on sponges and Crustose Coralline Algae (CCA) appears to have accelerated at the same time, so manipulative field experiments are proposed to rigorously test and differentiate the effects of ENSO elevated temperature on sponge mortality from the effects of enhanced sea urchin predation on sponges. More specifically, eight main hypotheses along with four alternate hypotheses are developed and proposed from a new conceptual model predicting direct and indirect pathways of regime change in a community of CCA, sponges, barnacles, corals, sea urchins, sea stars and predatory fish. The research will be performed in the rocky subtidal at the 12 community baseline sites in the central Galapagos archipelago during four trips in 2016-2017 bracketing the El Niño and La Niña phases. The proposed combination of experimental and observational (i.e. baseline re-sampling) methods will enable a rigorous evaluation of climate-induced direct and indirect pathways of regime change in tropical benthic ecosystems.
PROJECT OUTCOMES REPORT
Disclaimer
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.
The El Nino Southern Oscillation (ENSO) is the strongest inter-annual climate fluctuation known and it recurs every two to seven years. As such, ENSO provides a nearly unparalleled opportunity to study the impact of climate oscillations on populations, communities and ecosystems. We seized the opportunity provided by the 2015 -2017 ENSO to test hypotheses about how bottom dwelling marine communities and associated reef fish populations would change in response to the extreme oceanographic conditions in the central Galapagos archipelago (Fig. 1). The 2015 2016 El Nino was the strongest recorded since 1997/1999 event. Satellite measured Sea Surface Temperatures (SST) were more than 4.0o C above the 1981-2010 ENSO baseline. Our subtidal temperature record from the Rocas Gordon site (Fig. 1 B, C) indicated that temperature variability has increased over time in the Galapagos subtidal zone, likely representing increased thermal stress on marine organisms. A maximum temperature of 31.2o C occurred at 6 m depth at one of our sites at the end of March 2016. In addition to evaluating the overall impact of the strong El Nino on subtidal marine communities, we tested an overarching idea, the Sponge Reef Hypothesis (SRH), predicting that sponges may increasingly dominate space as corals decline from future climate change and ocean acidification.
The research funded by this award enabled us to conduct bi-annual surveys for 2 years (2015-2017) across 12 widely spaced sites (Fig. 1), while our 16-year baseline on species abundance leading up to this event allowed us to place the effects of the 2015/2017 ENSO in context. We found that sponges declined significantly (rather than increased) during the unusually warm El Nino conditions, thus the SRH was not supported. However, we discovered more changes associated with this ENSO than any other we’ve studied since 1999 (Fig. 2). They included 1) exceptionally high grazing on Crustose Coralline Algae (CCA) during the warmest period, 2) a reduction of barnacles due to heavy predation by fish and whelks during El Nino with a dramatic rebound in barnacle populations in January 2017 as productivity returned during La Nina, 3) a similar trend of population decline and increase during La Nina for 3 species of planktivorous reef fish (Fig. 2) and 4) two unprecedented, novel appearances of biological phenomena during the warmest period of the 2016 El Nino: cyanobacterial mats and disintegrating skin disease in reef fish. Our work showed that mats of these potentially noxious cyanobacteria overgrew ecologically important CCA, that they are temperature mediated, persistent and avoided by predators. In contrast, the fish disease was ephemeral, lasting only six months, focused in the region around our Cuatro Hermanos site (Fig. 1) but affecting up to 16 species of reef fish of all feeding types. The disease appears to have been caused by a bacterium Pantoea. It reduced the population densities of ring tailed damselfish, which is functionally important for increasing algal productivity of the sea floor, as well as king angelfish. This appears to be the first record of wildlife disease associated with a climate oscillation in the Galapagos marine ecosystem.
Physical and biological data from this project are available at the Biological and Chemical Data Management Office (BCO-DMO) via these links:
https://www.bco-dmo.org/dataset/628180/data
https://www.bco-dmo.org/dataset/683633
In addition, a general article describing our research fiundings under this award appeared in an article in the June 2017 isssue of National Geographic Magazine entitled: "Life in the balance: a warming planet threatens the Galapagos species that inspired Darwin’s theory of natural selection." with the link
https://www.nationalgeographic.com/magazine/2017/06/galapagos-climate-change-impacts-iconic-creatures/
Last Modified: 02/17/2018
Modified by: Jon D Witman
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