We are excited to share our latest publication (Witman & Lamb 2018), "Persistent differences between coastal and offshore kelp forest communities in a warming Gulf of Maine", published in the journal Plos One. The article highlights the unique biomass and diversity of the Cashes Ledge kelp forest 145 km east of the New Hampshire coast. Cashes Ledge is home to the greatest density and biomass of Saccharina latissima kelp at this depth in the Western North Atlantic, and supports a biomass of fish 305 times greater than coastal sites. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region that is functionally significant for sustained biological productivity in the Gulf of Maine.
A. view of common macroalgae at the coastal site of Mingo Rock dominated by Agarum kelp and the invasiive Dasysiphonia japonica. B. Saccharina latissima kelp forest on Cashes Ledge. C. View of S. latissima, a foundation species, at Cashes Ledge. D. Patch of Saccharina digitata kelp at Cashes Ledge. E. Photo of a deteriorating assemblage of S. latissima kelp covered with white colonies of the invasive bryozoan Membranipora membranacea during the warm summer of 2012. Fish in the foreground are cunner (Tautogolabrus adspersus). Photo credits: A, B and D by Brett Seymour, C and E by Brian Skerry.
Participants of the workshop on climate change in the Galapagos pose for a picture, including Jon Witman (second from left, back row), Pelayo Salinas de Leon, Boris Worm, Daniel Pauly, and other members of the Charles Darwin Station, Galapagos National Park, visiting scientists, and the Ecuadorian navy.
One sign of stress was that massive and finger corals turned white (bleached) during a broad temperature regime ranging from 30 to 16 o C in 12 months as the cool nutrient rich La Nina period followed the warm phase. For example, chlorophyll a, a measure of planktonic food concentration increased 7-fold during La Nina. Thus the team speculated that the ecosystem bounces back a certain degree during La Ninas – rolling uphill on the coaster, demonstrating resilience. A surprisingly consistent response seen during all 3 La Nina events was that barnacles settled and grew all over the rocky bottom and on the stressed corals down to 20 m depth. This represents a boost to the food chain as many species of fish and snails feed on the barnacles. It appears that the La Nina- increased barnacles may be slowly displacing corals. While corals did not bleach as much as previous El Ninos during the strong 2015-2016 El Nino, we observed a diverse range of ecological impacts from skin disease in reef fish to intense sea urchin grazing and a bloom of cyanobacteria at some oceanic sites. Our work underscores the importance of sustained ecological monitoring to detect the impact of climate oscillations in the ocean.
Fiona Beltram traveled to the University of Pennsylvania for the inaugural Ivy League Undergraduate Research Symposium (ILURS). The symposium consisted of 200 undergraduate students from Ivy League schools who were involved in independent research at their respective schools. Most students presented posters, while others gave short talks. Guest lectures by University of Pennsylvania and visiting faculty were also arranged throughout the three-day conference. Research topics ranged from art history and public health to astronomy and cancer research. Fiona gave a poster presentation detailing the results of her current work, which will serve as the first two chapters of her thesis for honors in the Biology degree. She is studying the appearance of cyanobacterial mats on the Galapagos reefs, the potential for a temperature-mediated introduction mechanism that is closely tied to El Niño extremes, and the ecological effects of the species’ continued presence on the reef.
Robbie lamb represented the Witman Lab at the annual meeting of the Ecological Society of America, August 6-11 at the Oregon Convention Center in Portland, Oregon. It was a terrific conference with some of the top ecologists in the country tackling some of our field's most pressing issues. A memorial session for Bob Paine brought together some of Dr Paine's former students including Jane Lubchenco, Bruce Menge, Peter Kareiva, and Jim Estes. Each gave talks highlighting Bob's legacy and teachings.
Robbie presented on his thesis research studying how wave turbulence filters the the community of subtidal herbivores in the Galapagos based on how quickly they can navigate the periodic stress of continually crashing waves. It was a real treat to elaborate on this research with Robbie's former advisor in the room, Bruce Menge of Oregon State University, who developed the environmental stress hypothesis over 30 years ago, the original inspiration for Robbie's work on flow and feeding.
Witman Lab covered in National Geographic feature article on climate change in the Galapagos Islands
One of our lab's primary research efforts is focused on studying the impacts of the El Niño - La Niña cycle on marine communities in the Galapagos Islands. This month, National Geographic featured an article on the work the Witman Lab and others are doing to study the myriad effects of climate perturbations on the iconic wildlife of the archipelago. You can read the article and check out special online content here, or see the print issue featuring the article titled "Life in the Balance" by Chris Solomon, photos by Thomas P. Peschak.
We are proud to share the new publication from the Witman Lab, titled "Experimental demonstration of a trophic cascade in the Galápagos rocky subtidal: Effects of consumer identity and behavior". In it, Professor Witman and colleagues Franz Smith and Mark Novak show observational and experimental evidence as well as behavioral interaction modeling of a 4-tier trophic cascade involving top predators (sea lions and sharks), meso-predators (triggerfish), herbivores (urchins), and primary producers (algae). This pathway is further complicated by interference competition by hogfish, which harass and steal the urchin prey from triggerfish. You can read the Brown University press release here, and the article is open access and free to read at:
Fiona Beltram was awarded a Voss Environmental Fellowship to study the dynamics and ecological impacts of cyanobacterial mats in the Galapagos Islands. We first discovered these mats covering large areas of the reef at several of our monitoring sites during the extreme El Niño event of 2015. Since then, Fiona has been developing experiments and observational techniques for assessing the environmental drivers of this new community state, what species might be potential herbivores of cyanobacteria, and how these mats affects the sessile invertebrates and algae that they overgrow.
Camila Lupi was awarded a UTRA grant to study the behavior of herbivorous fishes feeding on algae in extreme high wave environments. Camila will be working with graduate student Robbie Lamb using high-resolution measurements of wave velocities using an acoustic Doppler velocimeter, while simultaneously filming feeding behavior. The goal is to determine the flow conditions that are sufficient for excluding any given species from foraging in the shallow subtidal. This information will be used to validate a general model of periodically stressful environments and how they limit the potential for top-down ecological control.
Last Friday, Fiona Beltram was a guest speaker in Mr. David Moscarelli’s AP Environmental Science class at Ponaganset High School in North Scituate, RI (her former high school). Her presentation, entitled “Community Ecology in the Galapagos Islands”, outlined the basic principles of community ecology and their applications in marine systems. She discussed the lab’s work on El Nino-related effects of climate change in the Galapagos, and presented some recent temperature data from the 2015/2016 El Nino cycle. She then gave an overview of underwater fieldwork methods, and talked about her experience as part of the Witman Lab’s research team working in the Galapagos last summer. Mr. Moscarelli’s students are currently preparing to take the AP Environmental Science exam in May, and will continue to study community ecology and conservation biology throughout the year.
Jon and Robbie both attended the 2017 meeting of the Association for the Study of Limnology and Oceanography (ASLO), held at the wonderful Hawaii Convention Center in Honolulu, HI. It was a bit surreal to be back in Hawaii for a conference just 6 months after ICRS. Both gave talks on the effects of the extreme 2015-2016 El Niño event in Galapagos: Jon on benthic communities with a multi-ENSO perspective gained from almost 20 years of monitoring, and Robbie on fish communities. It was a very successful meeting and a great chance to learn more about the physical oceanography methods and questions currently being used.
Of course, a trip to Hawaii would not be complete without enjoying some of the beautiful landscapes and iconic wildlife!
Our work to describe the unique marine ecosystems on Cashes Ledge, a proposed marine national monument in the Gulf of Maine, is highlighted in the recent National Geographic February issue. The story is titled: "Why it's important to save our seas' last pristine places", and was written by Cynthia Barnett, with spectacular photography by our friend and colleague in the Cashes Ledge movement, Brian Skerry.
See also the Brown University website feature article written for Brown University News by David Orenstein: "Galápagos waters illustrate ecological drama of climate change". This article covers the Witman Lab's many research efforts studying the effects of El Niño cycles and climate change on marine ecosystems of the Galapagos Islands.
IN THE FIELD
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