Publications

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2019
Kim, S, Hammerstrom K, Dayton P.  2019.  Epifaunal community response to iceberg-mediated environmental change in McMurdo Sound, Antarctica. Marine Ecology Progress Series. 613:1-14.   10.3354/meps12899   AbstractWebsite

High-latitude marine communities are dependent on sea ice patterns. Sea ice cover limits light, and hence primary production and food supply. Plankton, carried by currents from open water to areas under the sea ice, provides a transitory food resource that is spatially and temporally variable. We recorded epifaunal abundances at 17 sites in McMurdo Sound, Antarctica, over 12 yr, and found differences in communities based on location and time. The differences in location support patterns observed in long-term infaunal studies, which are primarily driven by currents, food availability, and larval supply. The temporal differences, highlighting 2004 and 2009 as years of change, match the altered persistence of sea ice in the region, caused by the appearance and disappearance of mega-icebergs. The temporal changes were driven by changes in abundance of species that filter feed on large particulates. The shift in current patterns that occurred due to mega-icebergs decreased the normal food supply in the region. In addition to the decrease in food availability, we suggest that the reduced light resulting from thicker-than-normal sea ice resulted in a shift to smaller phytoplankton. A change in food quality as well as quantity may have influenced the temporal change in epifaunal communities.

2016
Dayton, P, Jarrell S, Kim S, Thrush S, Hammerstrom K, Slattery M, Parnell E.  2016.  Surprising episodic recruitment and growth of Antarctic sponges: Implications for ecological resilience. Journal of Experimental Marine Biology and Ecology. 482:38-55.   10.1016/j.jembe.2016.05.001   AbstractWebsite

Sponges are the most conspicuous component of the Antarctic benthic ecosystem, a system under stress both from climate change and fishing activities. Observations over four decades are compiled and reveal extremely episodic sponge recruitment and growth. Recruitment occurred under different oceanographic conditions on both sides of McMurdo Sound. Most of the sponges appear to have recruited in the late 1990s-2000. Observations from 2000 to 2010 follow thirty years of relative stasis with very little sponge recruitment or growth followed by a general pattern of recruitment by some forty species of sponges. That there was almost no recruitment observed on natural substrata emphasizes the contrast between potential and realized recruitment This unique data set was derived from a region noted for physical stasis, but the episodic ecological phenomena highlight the importance of rare events. Against a background of intermittent food resources and the low metabolic costs of stasis, understanding the causes of irregular larval supply, dispersal processes, recruitment success and survivorship becomes critical to predicting ecosystem dynamics and resilience in response to increasing environmental change. Our time-series emphasizes that long-term data collection is essential for meaningful forecasts about environmental change in the unique benthic ecosystems of the Antarctic shelf. (C) 2016 Elsevier B.V. All rights reserved.

2013
Dayton, PK, Kim S, Jarrell SC, Oliver JS, Hammerstrom K, Fisher JL, O'Connor K, Barber JS, Robilliard G, Barry J, Thurber AR, Conlan K.  2013.  Recruitment, Growth and Mortality of an Antarctic Hexactinellid Sponge, Anoxycalyx joubini. PLOS One. 8   10.1371/journal.pone.0056939   AbstractWebsite

Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.

2011
Sala, E, Dayton PK.  2011.  Predicting strong community impacts using experimental estimates of per capita interaction strength: benthic herbivores and giant kelp recruitment. Marine Ecology-an Evolutionary Perspective. 32:300-312.   10.1111/j.1439-0485.2011.00471.x   AbstractWebsite

The estimation of the strength of the interaction between species is key for understanding the organization of ecological communities. Although experimental and observational studies have estimated per capita interaction strength for individual consumers, no previous study has used such estimates for predicting the impact of a community of consumers on their prey in the field. Here we evaluate experimental estimates of per capita interaction strength and impact of consumers on prey by comparing our impact predictions with real-time series of prey abundance. We conducted aquarium experiments to estimate the effects of seven herbivore species on survival of early life stages (microscopic sporophytes) of the giant kelp, Macrocystis pyrifera. We also estimated the impact of a community of herbivores on a cohort of kelp sporophytes using time series (1983-2000) of herbivore abundance in the Point Loma, San Diego (California), kelp forest. The underlying assumption was that maximum herbivore impact on microscopic recruits is realized only after a disturbance removes the giant kelp plants and thus releases the recruits. Our model was successful in predicting the prevention of giant kelp recruitment, which occurred when the abundance of weak interactors increased above a threshold. These results indicate that experimental estimates of maximum per capita interaction strength can be used to predict strong consumer impacts.

2006
Thrush, S, Dayton P, Cattaneo-Vietti R, Chiantore M, Cummings V, Andrew N, Hawes I, Kim S, Kvitek R, Schwarz AM.  2006.  Broad-scale factors influencing the biodiversity of coastal benthic communities of the Ross Sea. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 53:959-971.   10.1016/j.dsr2.2006.02.006   AbstractWebsite

Early ecological research in McMurdo Sound revealed local spatial gradients in community structure associated with variations in anchor ice disturbance, fast ice and snow cover, and the effects of predators. Research contrasting the cast and west sides of McMurdo Sound has shown major differences in benthic communities, which have been attributed to oceanographic influences on the advection of water-column productivity and the frequency of fast ice break-out. Despite these regional and local differences, coastal benthic communities in McMurdo Sound show a high level of stability, and contain a variety of large and potentially very long-lived species. In Terra Nova Bay, about half way along the Victoria Land Coast of the western Ross Sea, the coastal benthic communities provide some insightful contrasts with those in McMurdo Sound. For example, the abundance and depth distribution of dominant species such as Sterechinus neumayeri and Adamussium colbecki are markedly different from McMurdo Sound. In both locations communities dominated by large sponges are most prolific in regions that are free from iceberg disturbance of the seabed. A recent assessment of northern Victoria Land coastal benthic communities, in conjunction with multibeam imagery of the seafloor, further highlights the importance of iceberg disturbance in structuring Antarctic benthic communities. A comparative synthesis of these coastal ecological studies enables us to generate hypotheses concerning the relative importance of different environmental drivers in structuring benthic communities. Overlain on the regular latitudinal shifts in physical factors such as light regime, are regional fluctuations that are controlled by atmospheric and oceanographic circulation patterns and coastal topography/bathymetry. Change in diversity along the western coast of the Ross Sea is predicted to be influenced by three main factors (1) ice disturbance (e.g., via anchor ice and advection of supercooled water or icebergs), (2) photosynthetically available radiation (affected by ice and snow cover and water clarity), (3) the locations of polynyas and advection of planktonic production and larvae. Interactions between these factors are expected to result in non-linear changes along the latitudinal gradient. While predictions generated from these hypotheses remain to be rigorously tested, they provide indications of how benthic communities may respond to changes in production, disturbance and the stability of coastal sea ice. (c) 2006 Elsevier Ltd. All rights reserved.

2005
Parnell, PE, Lennert-Cody CE, Geelen L, Stanley LD, Dayton PK.  2005.  Effectiveness of a small marine reserve in southern California. Marine Ecology-Progress Series. 296:39-52.   10.3354/meps296039   AbstractWebsite

While relatively small, the San Diego-La Jolla Ecological Reserve is one of the oldest in California, and it contains giant-kelp-forest, boulder-reef, submarine-canyon and sandy-shelf habitats. We evaluated the effectiveness of this 'no-take' marine reserve and gauged its success according to the goals implicit in its design. To overcome the lack of data prior to its establishment, we employed habitat-specific analyses. Our study comprised 4 components: (1) an historical review of its establishment; (2) a survey of conspicuous species in kelp-forest, submarine-canyon, and boulder-reef habitats; (3) comparisons with historical data; (4) a public survey regarding awareness, knowledge, and support of the reserve. Despite 30 yr of protection, only a few sessile or residential species exhibit positive effects of protection, and most fished species have decreased in abundance inside the reserve. However, the reserve protects the largest remaining populations of green abalone Haliotis fulgens and vermillion rockfish Sebastes miniatus in the area, which therefore represent important sources of larvae. Implementation and enforcement of coastal reserves depends on public support, but the results of the public survey indicated a lack of knowledge of the reserve, highlighting the need for improved public education in this respect. The results of the study reflect the limited value of small reserves and document the inadequacy of inside/outside comparisons as tests of reserve effectiveness when baseline and historical data are lacking.