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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.

Dayton, PK, Oliver JS, Thrush SF, Hammerstrom K.  2019.  Bacteria defend carrion from scavengers. Antarctic Science. 31:13-15.   10.1017/s0954102018000457   AbstractWebsite

Carrion in the form of dead seal pups and algal mats placed on soft bottom habitats at Explorers Cove and Salmon Bay, McMurdo Sound, attract scavenging invertebrates that are driven away by hydrogen sulphide produced by sulphate-reducing bacteria sequestered below a layer of Beggiatoa/Thioploca-like filamentous bacteria. This system is usually found for lipid-rich marine mammal carrion, but also occurred with natural algal mats.

Dayton, PK, Jarrell SC, Kim S, Parnell PE, Thrush SF, Hammerstrom K, Leichter JJ.  2019.  Benthic responses to an Antarctic regime shift: food particle size and recruitment biology. Ecological Applications. 29   10.1002/eap.1823   AbstractWebsite

Polar ecosystems are bellwether indicators of climate change and offer insights into ecological resilience. In this study, we describe contrasting responses to an apparent regime shift of two very different benthic communities in McMurdo Sound, Antarctica. We compared species-specific patterns of benthic invertebrate abundance and size between the west (low productivity) and east (higher productivity) sides of McMurdo Sound across multiple decades (1960s-2010) to depths of 60 m. We present possible factors associated with the observed changes. A massive and unprecedented shift in sponge recruitment and growth on artificial substrata observed between the 1980s and 2010 contrasts with lack of dramatic sponge settlement and growth on natural substrata, emphasizing poorly understood sponge recruitment biology. We present observations of changes in populations of sponges, bryozoans, bivalves, and deposit-feeding invertebrates in the natural communities on both sides of the sound. Scientific data for Antarctic benthic ecosystems are scant, but we gather multiple lines of evidence to examine possible processes in regional-scale oceanography during the eight years in which the sea ice did not clear out of the southern portion of McMurdo Sound. We suggest that large icebergs blocked currents and advected plankton, allowed thicker multi-year ice, and reduced light to the benthos. This, in addition to a possible increase in iron released from rapidly melting glaciers, fundamentally shifted the quantity and quality of primary production in McMurdo Sound. A hypothesized shift from large to small food particles is consistent with increased recruitment and growth of sponges on artificial substrata, filter-feeding polychaetes, and some bryozoans, as well as reduced populations of bivalves and crinoids that favor large particles, and echinoderms Sterechinus neumayeri and Odontaster validus that predominantly feed on benthic diatoms and large phytoplankton mats that drape the seafloor after spring blooms. This response of different guilds of filter feeders to a hypothesized shift from large to small phytoplankton points to the enormous need for and potential value of holistic monitoring programs, particularly in pristine ecosystems, that could yield both fundamental ecological insights and knowledge that can be applied to critical conservation concerns as climate change continues.

Dayton, PK, Robilliard GA, Oliver JS, Kim S, Hammerstrom K, O'Connor K, Fisher J, Barber J, Jarrell S.  2018.  Long-term persistence of wood on the sea floor at McMurdo Sound, Antarctica. Antarctic Science. 30:355-356.   10.1017/s0954102018000305   AbstractWebsite
Abrams, PA, Ainley DG, Blight LK, Dayton PK, Eastman JT, Jacquet JL.  2016.  Necessary elements of precautionary management: implications for the Antarctic toothfish. Fish and Fisheries. 17:1152-1174.   10.1111/faf.12162   AbstractWebsite

We review the precautionary approach to fisheries management, propose a framework that will allow a systematic assessment of insufficient precaution and provide an illustration using an Antarctic fishery. For a single-species fishery, our framework includes five attributes: (1) limit reference points that recognize gaps in our understanding of the dynamics of the species; (2) accurate measures of population size; (3) ability to detect population changes quickly enough to arrest unwanted declines; (4) adequate understanding of ecosystem dynamics to avoid adverse indirect effects; and (5) assessment of the first four elements by a sufficiently impartial group of scientists. We argue that one or more of these elements frequently fail to be present in the management of many fisheries. Structural uncertainties, which characterize almost all fisheries models, call for higher limit points than those commonly used. A detailed look into the five elements and associated uncertainties is presented for the fishery on the Antarctic toothfish in the Ross Sea (FAO/CCAMLR Area 88.1, 88.2), for which management was recently described as highly precautionary'. In spite of having features that make the Ross Sea fishery ideal for the application of the precautionary approach, gaps in our knowledge and failure to acknowledge these gaps mean that current regulation falls short of being sufficiently precautionary. We propose some possible remedies.

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.

Dayton, PK, Hammerstrom K, Jarrell SC, Kim S, Nordhausen W, Osborne DJ, Thrush SF.  2016.  Unusual coastal flood impacts in Salmon Valley, McMurdo Sound, Antarctica. Antarctic Science. 28:269-275.   10.1017/s0954102016000171   AbstractWebsite

Large floods bringing significant sediments into the coastal oceans have not been observed in Antarctica. We report evidence of a large flood event depositing over 50 cm of sediment onto the nearshore benthic habitat at Salmon Bay, Antarctica, between 1990 and 2010. Besides direct observations of the sedimentation, the evidence involves a debris flow covering old tyre tracks from the early 1960s, as well as evidence of a considerable amount of sediment transported onto the Salmon Creek delta. We believe that the flood was sourced from the Salmon Glacier and possibly the smaller Blackwelder Glacier. Such floods will be more common in the future and it is important to better understand their ecological impacts with good monitoring programmes.

Gocke, C, Janussen D, Reiswig HM, Jarrell SC, Dayton PK.  2015.  Rossella podagrosa Kirkpatrick, 1907: A valid species after all. Zootaxa. 4021:169-177. AbstractWebsite

In this study we provide evidence that the species Rossella podagrosa Kirkpatrick, 1907, commonly considered a synonym of Rossella racovitzae Topsent, 1901, is truly a valid species. We show that it can be clearly distinguished from other species especially when taking into consideration the in situ habitus of the sponge in combination with the spicules. Furthermore we demonstrate the weaknesses in the so far published synonymy concept for the very complicated genus Rossella Carter, 1872. From this we conclude that the best strategy for further analysis of Rossella and establishment of acceptable synonymies will need to be based on detailed examination of the spicules, the holotypes, and in situ habitus. When possible it will be useful to analyze specimens from all Antarctic oceanographic regions.

Herzka, SZ, Mellink E, Talley DM, Huxel GR, Dayton PK.  2013.  Stable isotope ratios of egg albumen of three waterbird species nesting in the Colorado River Delta indicate differences in foraging ground and isotopic niche breadth. Aquatic Conservation-Marine and Freshwater Ecosystems. 23:546-563.   10.1002/aqc.2326   AbstractWebsite

1. The Colorado River Delta is one of the most impacted wetland systems in the world and has experienced massive habitat loss owing to severe restrictions in freshwater inflow as a result of dam construction and diversion of water for irrigation. However, the delta still offers nesting and foraging habitats for waterbirds, although the habitats available are highly fragmented and limited. 2. Stable isotope ratio (SIR) analysis was used to assess quantitatively isotopic niche width of gull-billed terns (Gelochelidon nilotica), laughing gulls (Leucophaeus atricilla) and snowy egrets (Egreta thula) that nest at an inland and coastal location. 3. The variance in carbon and nitrogen SIR of egg albumen indicated that inland colonies have a much broader isotope niche width (range 2.9 to 23.9) than coastal colonies (<0.1 to 1.4). 4. Species-specific mean albumen delta C-13 values from inland nests were significantly more depleted in C-13 than coastal colonies (-19.5 to -23.1 parts per thousand and -10.4 to -14.9 parts per thousand, respectively). Comparison of albumen delta C-13 values corrected for trophic fractionation with those of potential prey and primary producers collected at 10 potential foraging grounds indicates that females of the three species that nest in inland colonies did not feed in habitats located in the vicinity of their nesting site, while coastal colonies had distinct isotopic signatures reflecting marine primary production. Inland colonies probably forage in a variety of habitats and for different prey, relying on food webs based mostly on C3 terrestrial plants. 5. Differences in the isotopic composition of eggs from species nesting in the same area and between conspecifics nesting in different habitats indicate that foraging habitats vary substantially, suggesting that feeding varies as a function of local resource availability. 6. These results suggest that a variety of habitat types fulfill the foraging needs of this suite of nesting waterbird species, especially in inland colonies. Since the specific feeding areas of nesting females from the inland colonies have not been identified, protection of the remaining wetlands within the Colorado River Delta is warranted. Copyright (c) 2013 John Wiley & Sons, Ltd.

Christian, C, Ainley D, Bailey M, Dayton P, Hocevar J, Levine M, Nikoloyuk J, Nouvian C, Velarde E, Werner R, Jacquet J.  2013.  A review of formal objections to Marine Stewardship Council fisheries certifications. Biological Conservation. 161:10-17.   10.1016/j.biocon.2013.01.002   AbstractWebsite

The Marine Stewardship Council (MSC) was created as a conservation tool - intended to provide "the best environmental choice in seafood" to consumers and to create positive incentives that would improve the status and management of fisheries. During its 15 years, the MSC, which has an annual budget of close to US$20 million, has attached its logo to more than 170 fisheries. These certifications have not occurred without protest. Despite high costs and difficult procedures, conservation organizations and other groups have filed and paid for 19 formal objections to MSC fisheries certifications. Only one objection has been upheld such that the fishery was not certified. Here, we collate and summarize these objections and the major concerns as they relate to the MSC's three main principles: sustainability of the target fish stock, low impacts on the ecosystem, and effective, responsive management. An analysis of the formal objections indicates that the MSC's principles for sustainable fishing are too lenient and discretionary, and allow for overly generous interpretation by third-party certifiers and adjudicators, which means that the MSC label may be misleading both consumers and conservation funders. (C) 2013 Elsevier Ltd. All rights reserved.

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.

Konotchick, T, Parnell PE, Dayton PK, Leichter JJ.  2012.  Vertical distribution of Macrocystis pyrifera nutrient exposure in southern California. Estuarine Coastal and Shelf Science. 106:85-92.   10.1016/j.ecss.2012.04.026   AbstractWebsite

We examined water column temperature time series profiles for several years at two locations in a single kelp (Macrocystis pyrifera) forest to characterize the alongshore variability of the nutrient climate that giant kelp is exposed to and compare it to the response of giant kelp. The differences in nutrient climate are due to differential alongshore vertical variations in temperature, a well-established proxy of nitrate, due to the topographically induced internal wave dynamics within the kelp forest. We observed the greatest temperature variability during summer and most of this variability occurred near the surface. The 14.5 degrees C isotherm, indicating the presence of nitrate, ranged the entire vertical extent of the water column, and was shallowest during the winter and in the southern portion of the kelp forest. Predicted water column integrated nitrate varies from 0 mu mol NO3-/m(2) to 431 mu mol NO3-/m(2) yielding a time series daily average of 0.12 gN/m(2)day (North La Jolla) and 0.18 gN/m(2)day (South La Jolla). Redfield conversion of these values puts the time series daily average for carbon production (upper limit) between 0.8 and 1.2 gC/m(2)day for the north and south parts of the bed respectively, and shows considerable variation at several time scales. Giant kelp in the southern portion of the forest exhibited greater stipe densities (a proxy for kelp production) than individuals in the northern portion, corresponding with the alongshore nutrient climate variability. The depth of the nutricline varied by up to 10 m over time scales as short as hours. Variability was greatest at diurnal and semi-diurnal frequencies, with shallower water column depths showing greatest variability. These depth-specific variations in temperature and nutrient exposure may have biologically important consequences for M. pyrifera especially during low nutrient seasons. (C) 2012 Elsevier Ltd. All rights reserved.

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.

Parnell, PE, Miller EF, Lennert-Cody CE, Dayton PK, Carter ML, Stebbins TD.  2010.  The response of giant kelp (Macrocystis pyrifera) in southern California to low-frequency climate forcing. Limnology and Oceanography. 55:2686-2702.   10.4319/lo.2010.55.6.2686   AbstractWebsite

The nutrient climate on the inner shelf off southern California changed markedly across the 1976-1977 North Pacific climate regime shift. With respect to giant kelp (Macrocystis pyrifera) canopies off southern California, the nitrate climate shifted from relatively replete conditions prior to the regime shift to depleted conditions afterward, and the dynamics of 14 giant kelp forests appeared to change as a result. The response of giant kelp to nutrient-replete years before the regime shift was dampened compared to their response afterward. The sensitivity of these kelp-forest canopies to nutrient limitation appears to have increased since the regime shift. This intensification of physical control after 1977 is evident in the strong correlation of seawater density (sigma(t)) and M. pyrifera density. The linear fit of the percent of time the 25.1 sigma(t) isopycnal bathes the inner shelf, accounted for similar to 71% of the variability in kelp density off Point Loma, and the median depth of this isopycnal has deepened similar to 5 m since the regime shift. The wave climate also intensified beginning in the early 1970s. The dampened kelp response prior to the regime shift was likely due to greater biological control of kelp canopies via consumer and competitive processes (i.e., biological modulation) or decreased physical control at possibly many trophic levels. Our results suggest that the response of kelp forests to El Nino Southern Oscillation events is mediated by lower frequency climate modes that may modulate the regulatory importance of biological and physical processes on giant kelp.

Parnell, PE, Dayton PK, Fisher RA, Loarie CC, Darrow RD.  2010.  Spatial patterns of fishing effort off San Diego: implications for zonal management and ecosystem function. Ecological Applications. 20:2203-2222.   10.1890/09-1543.1   AbstractWebsite

The essence of ecosystem-based management is managing human practices to conserve the ecosystem. Ecologists focus on understanding the ecosystem, but there are fundamental information gaps including patterns of human exploitation. In particular, the spatial distribution of fishing effort must be known at the scales needed for ecologically relevant management. Fishing is a primary impact on coastal ecosystems, yet catch distribution at scales relevant to habitats and processes are not well known for many fisheries. Here we utilized photographic time series, logbook records, and angler surveys to estimate the intensity and spatial pattern of commercial and recreational fishing. Effort was clearly aggregated for most types of fishing, the motivating factors for effort distribution varied among areas, and effort was coupled or uncoupled to habitat depending on the area and type of fishing. We estimated that similar to 60% and similar to 74% of private recreational and recreational charter vessel fishing effort, respectively, were concentrated into two small areas that also included similar to 78% of commercial sea urchin effort. Exploitation and effort were considerably greater in one kelp forest, which has important implications for patterns of kelp persistence, productivity, and ecosystem function. Areas subject to the greatest recreational fishing pressure appeared to have lower diversity. Our results indicate that fine-scale patterns of fishing effort and exploitation have profound consequences for ecosystem functioning and biodiversity. Ecosystem-based management of nearshore ecosystems depends on an understanding of the fine-scale patterns of exploitation.

Thrush, SF, Dayton PK.  2010.  What can ecology contribute to ecosystem-based management? Annual Review of Marine Science. 2:419-441.   10.1146/annurev-marine-120308-081129   Abstract

Modern fishing changes the ocean environment in many ways, including disturbing the sea floor, altering the food webs, and shifting many important ecosystem functions. Natural history, oceanographic, habitat, behavior, and ecological information must be integrated to implement meaningful ecosystem-based management. We discuss the urgent need to expand the concept of essential fish habitat to include important food-web relationships. The need for a broader perspective in terms of ecosystem function and the effects of interactive stressors is emphasized to in maintain the vitality and resilience of valued ecosystems. Maintenance of multiple ecosystem functions is a key factor in the adaptive capacity of ecosystems to change. We argue that ail ecological understanding of resilience embraces uncertainty and encourages multiple approaches to the management of humans such that ecosystem functions are maintained.

Thrush, SF, Hewitt JE, Dayton PK, Coco G, Lohrer AM, Norkko A, Norkko J, Chiantore M.  2009.  Forecasting the limits of resilience: integrating empirical research with theory. Proceedings of the Royal Society B-Biological Sciences. 276:3209-3217.   10.1098/rspb.2009.0661   AbstractWebsite

Despite the increasing evidence of drastic and profound changes in many ecosystems, often referred to as regime shifts, we have little ability to understand the processes that provide insurance against such change (resilience). Modelling studies have suggested that increased variance may foreshadow a regime shift, but this requires long-term data and knowledge of the functional links between key processes. Field-based research and ground-truthing is an essential part of the heuristic that marries theoretical and empirical research, but experimental studies of resilience are lagging behind theory, management and policy requirements. Empirically, ecological resilience must be understood in terms of community dynamics and the potential for small shifts in environmental forcing to break the feedbacks that support resilience. Here, we integrate recent theory and empirical data to identify ways we might define and understand potential thresholds in the resilience of nature, and thus the potential for regime shifts, by focusing on the roles of strong and weak interactions, linkages in meta-communities, and positive feedbacks between these and environmental drivers. The challenge to theoretical and field ecologists is to make the shift from hindsight to a more predictive science that is able to assist in the implementation of ecosystem-based management.

Levin, LA, Dayton PK.  2009.  Ecological theory and continental margins: where shallow meets deep. Trends in Ecology & Evolution. 24:606-617.   10.1016/j.tree.2009.04.012   AbstractWebsite

Continental margins, where land becomes ocean and plunges to the deep sea, provide valuable food and energy resources, and perform essential functions such as carbon burial and nutrient cycling. They exhibit remarkably high species and habitat diversity, but this is threatened by our increasing reliance on the resources that margins provide, and by warming, expanding hypoxia and acidification associated with climate change. Continental margin ecosystems, with environments, constituents and processes that differ from those in shallow water, demand a new focus, in which ecological theory and experimental methods are brought to bear on management and conservation practices. Concepts of disturbance, diversity-function relationships, top-down versus bottom-up control, facilitation and meta-dynamics offer a framework for studying fundamental processes and understanding future change.

Braje, TJ, Erlandson JM, Rick TC, Dayton PK, Hatch MBA.  2009.  Fishing from past to present: continuity and resilience of red abalone fisheries on the Channel Islands, California. Ecological Applications. 19:906-919.   10.1890/08-0135.1   AbstractWebsite

Archaeological data from coastal shell middens provide a window into the structure of ancient marine ecosystems and the nature of human impacts on fisheries that often span millennia. For decades Channel Island archaeologists have studied Middle Holocene shell middens visually dominated by large and often whole shells of the red abalone (Haliotis rufescens). Here we use modern ecological data, historical accounts, commercial red abalone catch records, and zooarchaeological data to examine long-term spatial and temporal variation in the productivity of red abalone fisheries on the Northern Channel Islands, California (USA). Historical patterns of abundance, in which red abalone densities increase from east to west through the islands, extend deep into the Holocene. The correlation of historical and archaeological data argue for long-term spatial continuity in productive red abalone fisheries and a resilience of abalone populations despite dramatic ecological changes and intensive human predation spanning more than 8000 years. Archaeological, historical, and ecological data suggest that California kelp forests and red abalone populations are structured by a complex combination of top-down and bottom-up controls.

Auster, PJ, Fujita R, Kellert SR, Avise J, Campagna C, Cuker B, Dayton P, Heneman B, Kenchington R, Stone G, Di Sciara GN, Glynn P.  2009.  Developing an ocean ethic: science, utility, aesthetics, self-interest, and different ways of knowing. Conservation Biology. 23:233-235.   10.1111/j.1523-1739.2008.01057.x   AbstractWebsite
Hewitt, JE, Thrush SF, Dayton PD.  2008.  Habitat variation, species diversity and ecological functioning in a marine system. Journal of Experimental Marine Biology and Ecology. 366:116-122.   10.1016/j.jembe.2008.07.016   AbstractWebsite

The expectation that long-term, broad-scale changes in the relative abundance of species, homogenisation of habitats and decreases in diversity will affect ecosystem function has led to an increasing number of studies on functional diversity and composition. Such studies frequently consider the effect of environmental gradients and anthropogenic impacts, but rarely the effect of biogenic habitat variation. In marine soft-sediment systems, habitat variability is likely to be of particular importance because of the strong link between habitat and species diversity. In this study we examine the link between functional trait diversity (as richness and evenness) and composition, and habitat variation in two locations with different regional species pools. We found similar functional traits occurring in the two locations, but differences between habitats within the locations. High evenness within traits was apparent (across both locations and habitats) reflecting the potential for the maintenance of function with the loss of individual species. Between-habitat differences in functional traits were driven by differences in organism densities rather than the presence/absence of individual traits, emphasising the importance of density shifts in driving function. Furthermore, our demonstration of habitat variation as a driver of functional composition and diversity suggests that habitat heterogeneity should be explicitly included within studies trying to predict the effect of species loss on ecosystem function. (C) 2008 Elsevier B.V. All rights reserved.

Parnell, PE, Groce AK, Stebbins TD, Dayton PK.  2008.  Discriminating sources of PCB contamination in fish on the coastal shelf off San Diego, California (USA). Marine Pollution Bulletin. 56:1992-2002.   10.1016/j.marpolbul.2008.08.023   AbstractWebsite

Management of coastal ecosystems necessitates the evaluation of pollutant loading based on adequate source discrimination. Monitoring of sediments and fish on the shelf off San Diego has shown that some areas on the shelf are contaminated with polychlorinated biphenyls (PCBs). Here, we present an analysis of PCB contamination in fish on the shelf off San Diego designed to discriminate possible sources. The analysis was complicated by the variability of species available for analysis across the shelf, variable affinities of PCBs among species, and non-detects in the data. We utilized survival regression analysis to account for these complications. We also examined spatial patterns of PCBs in bay and offshore sediments and reviewed more than 20 years of influent and effluent data for local wastewater treatment facilities. We conclude that most PCB contamination in shelf sediments and fish is due to the ongoing practice of dumping contaminated sediments dredged from San Diego Bay. (C) 2008 Elsevier Ltd. All rights reserved.

Steneck, RS, Bustamante RH, Dayton PK, Jones GP, Hobday AJ.  2008.  Current status and future trends in kelp forest ecosystems. Aquatic ecosystems : trends and global prospects. ( Polunin N, Ed.).:xvi,482p.., Cambridge, UK ; New York: Cambridge University Press AbstractWebsite
Hewitt, JE, Thrush SF, Dayton PK, Bonsdorff E.  2007.  The effect of spatial and temporal heterogeneity on the design and analysis of empirical studies of scale-dependent systems. American Naturalist. 169:398-408.   10.1086/510925   AbstractWebsite

Processes interacting across scales of space and time influence emergent patterns in ecological systems, but to obtain strong inference and empirical generalities, ecologists need to balance reality with the practicalities of design and analyses. This article discusses heterogeneity, scaling, and design analysis problems and offers potential solutions to improve empirically based research. In particular, we recommend bridging the dichotomy between correlative and manipulative studies by nesting manipulative studies within a correlative framework. We suggest that building on variation, by designing studies to detect variability, rather than fighting it often leads to an increase in generality. We also emphasize the importance of natural history information for determining likely scales of spatial and temporal heterogeneity and the probable occurrence of feedback loops, indirect effects, and interacting processes. Finally, we integrate these concepts and suggest planned iterations between multiscale studies to build up natural history information and test the strength of relationships across space and time. This offers a way forward in terms of heuristically developing models and determining ecological generalities.

Parnell, PE, Dayton PK, Margiotti F.  2007.  Spatial and temporal patterns of lobster trap fishing: a survey of fishing effort and habitat structure. Bulletin Southern California Academy of Sciences. 106:27-37.   10.3160/0038-3872(2007)106[27:SATPOL]2.0.CO;2   Abstract

ABSTRACT The patterns of distribution and abundance for the California spiny lobster (Panulirus interruptus) within the kelp forest off La Jolla, CA (USA) were compared to the distribution of fishing effort during the 2005/2006 lobster season over an area of 20.25 km2. Fishing intensity was greatest at the beginning of the season (3333 traps on opening day) decreasing to 258 traps a few days before the end of the 24 week-long season. The collective effort of the trap fishermen primarily targeted the best habitats at the scale of the kelp forest, but fishing effort at smaller scales (250m, the smallest scale of our study) was less correlated to the best lobster habitats, especially near the beginning of the season. Fishing efficiency (CPUE) decreased linearly throughout the season, decreasing by more than an order of magnitude despite the fact that the distribution of fishing effort was better correlated with habitat quality and distribution near the end of the season. Fishing effort was greatest throughout the season at the edge of a small no-take marine protected area indicating possible fishing of spillover.