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Thrush, SF, Pridmore RD, Bell RG, Cummings VJ, Dayton PK, Ford R, Grant J, Green MO, Hewitt JE, Hines AH, Hume TM, Lawrie SM, Legendre P, McArdle BH, Morrisey D, Schneider DC, Turner SJ, Walters RA, Whitlatch RB, Wilkinson MR.  1997.  The sandflat habitat: scaling from experiments to conclusions. Journal of Experimental Marine Biology and Ecology. 216:1-9.   10.1016/s0022-0981(97)00087-7   AbstractWebsite
Wilder, RJ, Tegner MJ, Dayton PK.  1999.  Saving marine biodiversity. Issues in Science and Technology. 15:57-64. AbstractWebsite
Schneider, DC, Walters R, Thrush S, Dayton P.  1997.  Scale-up of ecological experiments: Density variation in the mobile bivalve Macomona liliana. Journal of Experimental Marine Biology and Ecology. 216:129-152.   10.1016/s0022-0981(97)00093-2   AbstractWebsite

At present the problem of scaling up from controlled experiments (necessarily at a small spatial scale) to questions of regional or global importance is perhaps the most pressing issue in ecology. Most of the proposed techniques recommend iterative cycling between theory and experiment. We present a graphical technique that facilitates this cycling by allowing the scope of experiments, surveys, and natural history observations to be compared to the scope of models and theory. We apply the scope analysis to the problem of understanding the population dynamics of a bivalve exposed to environmental stress at the scale of a harbour. Previous lab and field experiments were found not to be 1:1 scale models of harbour-wide processes. Scope analysis allowed small scale experiments to be linked to larger scale surveys and to a spatially explicit model of population dynamics. (C) 1997 Elsevier Science B.V.

Thrush, SF, Schneider DC, Legendre P, Whitlatch RB, Dayton PK, Hewitt JE, Hines AH, Cummings VJ, Lawrie SM, Grant J, Pridmore RD, Turner SJ, McArdle BH.  1997.  Scaling-up from experiments to complex ecological systems: Where to next? Journal of Experimental Marine Biology and Ecology. 216:243-254.   10.1016/s0022-0981(97)00099-3   AbstractWebsite
Tegner, MJ, Dayton PK, Edwards PB, Riser KL.  1995.  Sea urchin cavitation of giant kelp (Macrocystis pyrifera Agardh, C.) holdfasts and its effects on kelp mortality across a large California forest. Journal of Experimental Marine Biology and Ecology. 191:83-99.   10.1016/0022-0981(95)00053-t   AbstractWebsite

Sea urchins, Strongylocentrotus franciscanus (A. Agassiz) and especially S. purpuratus (Stimpson) sheltering in holdfasts of giant kelp, Macrocystis pyrifera, feed on haptera, eventually creating cavitation damage that leads to structural failure of the holdfast when the plants are stressed by large waves. Periodically giant kelp plants on permanent transects in a large Southern California forest were categorized for their degree of urchin infestation and cavitation damage, and subsequent survival followed for 5 yr. Plants with a high degree of urchin damage had significantly higher rates of mortality than plants with little damage during several assessment periods. There was a decreasing gradient in the degree of urchin damage and importance of cavitation from the deep (18 m), outer edge of the Point Loma forest, through the center (15 m), to the inner (12 m) edge of the forest which paralleled urchin abundance and recruitment rates. This gradient acts to reduce the impact of the gradient of giant kelp mortality caused by storms, which is much greater in shallow water and decreases seaward.

Tegner, MJ, Dayton PK.  1977.  Sea urchin recruitment patterns and implications of commercial fishing. Science. 196:324-326.   10.1126/science.847476   AbstractWebsite

Coexisting sea urchins Strongylocentrotus purpuratus and S. franciscanus exhibit different recruitment patterns. Juveniles of the former species are found in a variety of habitats, whereas juveniles of the latter occur almost exclusively under the spine canopy of conspecific adults. The commercial harvest of S. franciscanus thus seems to affect nursery grounds as well as the reproductive potential of exploited populations.

Tegner, MJ, Dayton PK.  1991.  Sea urchins, El Ninos, and the long-term stability of southern California kelp forest communities. Marine Ecology-Progress Series. 77:49-63.   10.3354/meps077049   AbstractWebsite

Southern California kelp forests experienced major losses during the El Nino of 1957-1959. The proximal reason for the decline was ascribed to sea urchin grazing, and the eventual recovery of some forests followed sea urchin control efforts, kelp restoration, and improvements in sewage disposal practices. The very strong El Nino of 1982-84 allowed us to reexamine hypotheses regarding the interactions between kelps, sea urchins, and warm water, and to speculate about what happened during the earlier El Nino. Algal drift abundance, urchin recruitment rates, and changes in urchin density were followed at 5 sites in the Point Loma kelp forest near San Diego from 1983 to 1987. Sea urchin recruitment rates were very low during 1982-84 and the apparent reasons for this, namely decreased reproduction, depauperate planktonic conditions, and altered current patterns, probably prevailed during the earlier El Nino as well. Algal drift did not become limiting during the recent event, but urchin grazing was triggered at one site in 1987 after an amphipod infestation had reduced kelp biomass, and urchin recruitment and migration had increased grazing pressure. The Point Loma kelp forest showed significant recovery the year after the 1982-84 El Nino, something that took over 5 yr in the 1960s. Decline in the density of red urchins Strongylocentrotus franciscanus since the mid 1970s suggests that the fishery for this species, which became extensive in the late 1970s, Was an important contributor to the faster kelp recovery. In the absence of evidence for increased recruitment or temperature effects on grazing demand, it appears that the destructive grazing observed during and after the El Nino of 1957-59 resulted from reductions in kelp standing stock and productivity below levels necessary to satisfy the existing grazing demand.

Tegner, MJ, Dayton PK.  1997.  Shifting baselines and the problem of reduced expectations in nearshore fisheries. California and the World Ocean '97. :119-128., San Diego, CA: American Society of Civil Engineers Abstract
Dayton, PK, Tegner MJ, Edwards PB, Riser KL.  1998.  Sliding baselines, ghosts, and reduced expectations in kelp forest communities. Ecological Applications. 8:309-322.   10.2307/2641070   AbstractWebsite

The detection of trends in ecosystems depends upon (1) a good description of the foundation or benchmark against which changes are measured and (2) a distinction between natural and anthropogenic changes. Patterns and mechanisms observed over 25 years in a large kelp forest suggest that definition of a meaningful benchmark is impossible, because many of the large animals have been gone for years to decades, and kelps are sensitive to large-scale, low-frequency El Nino-Southern Oscillation events and longer term regime shifts. A shift in the oceanographic climate has significantly reduced the average size and carrying capacity of the dominant plant. The animals that have been functionally removed from the community include sea otters, black sea bass, yellowtail, white sea bass, and abalones. Other species are still present, but fisheries have had huge effects on the abundances, size-frequencies, and/or spatial distributions of sheephead, kelp bass, rays, flatfish, rock fish, spiny lobsters, and red sea urchins. Now even sea cucumbers, crabs, and small snails are subject to unregulated fishing. The plants continue to exist without a hint of the effects of the loss of so much animal biomass. Furthermore, most of the megafauna have been removed with very little documentation or historical understanding of what the natural community was like. Thus, our ability to separate anthropogenic impacts from the "natural" dynamics of the system is severely compromised. We discuss the importance of both an ecosystem focus on productivity and careful monitoring of as many populations as possible. In addition, we show that this community is not tightly integrated with mutual dependencies; hence, many species can be removed without much affecting the rest of the ecosystem.

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.

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.

Legendre, P, Thrush SF, Cummings VJ, Dayton PK, Grant J, Hewitt JE, Hines AH, McArdle BH, Pridmore RD, Schneider DC, Turner SJ, Whitlatch RB, Wilkinson MR.  1997.  Spatial structure of bivalves in a sandflat: Scale and generating processes. Journal of Experimental Marine Biology and Ecology. 216:99-128.   10.1016/s0022-0981(97)00092-0   AbstractWebsite

A survey was conducted during the summer of 1994 within a fairly homogeneous 12.5 ha area of sandflat off Wiroa Island, in Manukau Harbour, New Zealand, to identify factors controlling the spatial distributions of the two dominant bivalves, Macomona liliana Iredale and Austrovenus stutchburyi (Gray), and to look for evidence of adult-juvenile interactions within and between species. Most of the large-scale spatial structure detected in the bivalve count variables (two species, several size classes of each) was explained by the physical and biological variables. The results of principal component analysis and spatial regression modelling suggest that different factors are controlling the spatial distributions of adults and juveniles. Larger size classes of both species displayed significant spatial structure, with physical variables explaining some but not all of this variation. Smaller organisms were less strongly spatially structured, with virtually all of the structure explained by physical variables. The physical variables important in the regression models differed among size classes of a species and between species. Extreme size classes (largest and smallest) were best explained by the models; physical variables explained from 10% to about 70% of the variation across the study site, Significant residual spatial variability was detected in the larger bivalves at the scale of the study site. The unexplained variability (20 to 90%) found in the models is likely to correspond to phenomena operating at smaller scales, Finally, we found no support for adult-juvenile interactions at the scale of our study site, given our sampling scale, after controlling for the effects of the available physical variables. This is in contrast to significant adult-juvenile interactions found in smaller-scale surveys and in field experiments. Our perception of adult-juvenile interactions thus depends on the scale of study. (C) 1997 Elsevier Science B.V.

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.

Birkeland, C, Dayton PK, Engstrom NA.  1982.  A stable system of predation on a holothurian by four asteroids and their top predator. Papers from the Echinoderm Conference . 16:175-189. AbstractWebsite
Seymour, RJ, Tegner MJ, Dayton PK, Parnell PE.  1989.  Storm wave induced mortality of giant kelp, Macrocystis pyrifera, in southern California. Estuarine Coastal and Shelf Science. 28:277-292.   10.1016/0272-7714(89)90018-8   AbstractWebsite

The storm-related mortality rates of adult Macrocystis pyrifera in a Southern California giant kelp forest were determined over several winter storm seasons and compared with the hydrodynamic attributes of the most energetic storms. The data include stormy and relatively benign years and an exceptional storm which resulted in almost total destruction of a major Macrocystis forest. High orbital velocities (associated with large, high frequency waves), the presence of breaking waves, and entanglement by drifters were found to increase mortality through stipe breakage or holdfast failure. Longshore variability in wave intensity was found to affect kelp mortality rates. The data suggest that wave breaking may be an important factor in determining the inner boundary of the kelp bed.

Dayton, PK.  1985.  The structure and regulation of some South American kelp communities. Ecological Monographs. 55:447-468.   10.2307/2937131   AbstractWebsite
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.