Abstract. The intensity of human pressure on marine systems has led to a push for stronger marine conservation efforts. Recently, marine reserves have become one highly advocated form of marine conservation, and the number of newly designated reserves has increased dramatically. Reserves will be essential for conservation efforts because they can provide unique protection for critical areas, they can provide a spatial escape for intensely exploited species, and they can potentially act as buffers against some management miscalculations and unforeseen or unusual conditions. Reserve design and effectiveness can be dramatically improved by better use of existing scientific understanding. Reserves are insufficient protection alone, however, because they are not isolated from all critical impacts. Communities residing within marine reserves are strongly influenced by the highly variable conditions of the water masses that continuously flow through them. To a much greater degree than in terrestrial systems, the scales of fundamental processes, such as population replenishment, are often much larger than reserves can encompass. Further, they offer no protection from some important threats, such as contamination by chemicals. Therefore, without adequate protection of species and ecosystems outside reserves, effectiveness of reserves will be severely compromised. We outline conditions under which reserves are likely to be effective, provide some guidelines for increasing their conservation potential, and suggest some research priorities to fill critical information gaps. We strongly support vastly increasing the number and size of marine reserves; at the same time, strong conservation efforts outside reserves must complement this effort. To date, most reserve design and site selection have involved little scientific justification. They must begin to do so to increase the likelihood of attaining conservation objectives.

The intensity of human pressure on marine systems has led to a push for stronger marine conservation efforts. Recently, marine reserves have become one highly advocated form of marine conservation, and the number of newly designated reserves has increased dramatically. Reserves will be essential for conservation efforts because they can provide unique protection for critical areas, they can provide a spatial escape for intensely exploited species, and they can potentially act as buffers against some management miscalculations and unforeseen or unusual conditions. Reserve design and effectiveness can be dramatically improved by better use of existing scientific understanding. Reserves are insufficient protection alone, however, because they are not isolated from all critical impacts. Communities residing within marine reserves are strongly influenced by the highly variable conditions of the water masses that continuously flow through them. To a much greater degree than in terrestrial systems, the scales of fundamental processes, such as population replenishment, are often much larger than reserves can encompass. Further, they offer no protection from some important threats, such as contamination by chemicals. Therefore, without adequate protection of species and ecosystems outside reserves, effectiveness of reserves will be severely compromised. We outline conditions under which reserves are likely to be effective, provide some guidelines for increasing their conservation potential, and suggest some research priorities to fill critical information gaps. We strongly support vastly increasing the number and size of marine reserves; at the same time, strong conservation efforts outside reserves must complement this effort. To date, most reserve design and site selection have involved little scientific justification. They must begin to do so to increase the likelihood of attaining conservation objectives.

Abstract. Recent theory, such as the insurance hypothesis, suggests that higher species diversity may dampen perturbation dynamics within a community. The dynamics of a rocky intertidal macroalgal community were evaluated using an experimentally induced heat stress applied at the end of a 15-mo manipulation of diversity. This pulse event produced a gradient of thermal stress within plots and, consequently, different degrees of perturbation. In general, the resistance of the community to the thermal stress was forecast by the pre-stress cover of dominant species, total algal cover, and standing biomass. Because higher diversity treatments, especially those containing the dominant algal group, fucoids, had higher overall abundance, highest diversity treatments were the most severely affected. The stress was also relatively nonselective, in that species were reduced in roughly equivalent proportions, suggesting an important distinction for predicting when diversity will not influence disturbance dynamics. The resilience of the community was strongly dependent on which species were initially present in the plots and the degree of disturbance. In highly disturbed areas, although the recovery trajectory was similar in early successional stages, differences emerged later; these differences appear to be attributable to the composition of the surrounding regeneration pool. For treatments not receiving the thermal stress, low-diversity plots without fucoids remained in states unlike the reference condition for most of the monitored resilience period. But plots in high-diversity treatments, even areas within plots that had experienced moderate disturbance, returned to states similar to the reference quickly. Thus, resilience (but not resistance) results are consistent with the insurance hypothesis. Overall, diversity's influence on community dynamics is complex and will depend on the characteristics of the stress as well as the characteristics of the species present in the community.

Local interactions, biotic and abiotic, can have a strong influence on the large-scale properties of ecosystems. However, ecological models often explore the influence of local biotic interactions where physical disturbance is included as a large-scale and imposed source of variability but is not allowed to interact with biotic processes at the local scale. In marine intertidal communities dominated by mussels, wave disturbances create gaps in the mussel bed that recover through a successional sequence. We present a lattice model of mussel disturbance dynamics that allows local interactions between wave disturbance and mussel recolonization, in which each cell of the lattice can be empty, occupied by a mussel bed element, or disturbed (which corresponds to a newly disturbed cell that has unstable edges). As in natural ecosystems, wave disturbance can also spread from disturbed to adjacent occupied cells, and recolonization can also spread from occupied to adjacent empty cells. We first validate the local rules from artificial gap experiments and from natural gap monitoring along the Oregon coast. We analyze the properties of the model system as a function of different oceanographic forcings of productivity and disturbance. We show that the mussel bed can go through phase transitions characterized by a large sensitivity of mussel cover and patterns to oceanographic forcings but also that criticality (scale invariance) is observed over wide ranges of parameters, which suggests self-organization. We also show that spatial patterns in the intertidal can provide a robust signature of local processes and can inform about oceanographic regimes. We do so by comparing the large-scale patterns of the simulation (scaling exponents) with field data, which suggest that some experimental sites are close to criticality. Our results suggest that regional patterns in disturbed populations can be explained by local biotic and abiotic processes submitted to oceanographic forcing.

Abstract. When viewed across long temporal and large spatial scales, severe disturbances in marine ecosystems are not uncommon. Events such as hurricanes, oil spills, disease outbreaks, hypoxic events, harmful algal blooms, and coral bleaching can cause massive mortality and dramatic habitat effects on local or even regional scales. Although designers of marine reserves might assume low risk from such events over the short term, catastrophes are quite probable over the long term and must be considered for successful implementation of reserves. A simple way to increase performance of a reserve network is to incorporate into the reserve design a mechanism for calculating how much additional area would be required to buffer the reserve against effects of catastrophes. In this paper, we develop a method to determine this ''insurance factor'': a multiplier to calculate the additional reserve area necessary to ensure that functional goals of reserves will be met within a given ''catastrophe regime.'' We document and analyze the characteristics of two relatively well-studied types of disturbances: oil spills and hurricanes. We examine historical data to characterize catastrophe regimes within which reserves must function and use these regimes to illustrate the application of the insurance factor. This tool can be applied to any reserve design for which goals are defined by a quantifiable measure, such as a fraction of shoreline, that is necessary to accomplish a particular function. In the absence of such quantitative measures, the concept of additional area as insurance against catastrophes may still be useful.

The region of the eastern North Pacific coastline dominated by the California Current was surveyed annually from [2001][2002][2003] to examine (1) benthic macro-invertebrate and algal populations, (2) the magnitude and patterns of key environmental variables, and (3) how dynamic populations and communities of macroalgae and invertebrates respond to spatial differences in nearshore geomorphology, wave dynamics, and oceanography of the coastal shelf. We used a highly replicated spatially nested sampling design consisting of 144 shore segments (bedrock platforms longer than 50 m) with three replicate segments per site (,1 km), three sites per area (,10 km), and sixteen areas (.10 km) grouped into six domains (hundreds of kilometers). Results suggest that (1) low zone diversity was higher at northern latitudes when measured at segment, site, and area scales, but at domain scales there were more species at southern latitudes; (2) community structure showed high fidelity to geographic location with community similarity inversely related to separation distance, and the only regional scale biological discontinuity in community structure was centered near Pt. Conception; and (3) wave runup was the most significant physical parameter affecting overall community structure, however, tidal range, precipitation, air and water temperature, upwelling, salinity, and sand were significant mechanisms forcing differences in community structure within the region.Understanding the underlying causes of gradients of diversity has been a long-standing focus of the ecological community. The problem is complex and has been beset by controversy, yet great strides have been made (Huston 1995;Rosenzweig 1995;Hubbell 2001). A recent focus has been on the relative contributions of local factors, dispersal, and scale-dependent regional factors that influence regional species pools (Ricklefs 2004;Witman et al. 2004;Russell et al. 2006). The increased focus on largescale dynamics, however, has exposed a major shortcoming in many of the datasets that have been used to evaluate diversity hypotheses: the level of detail and resolution is

Our understanding of the relative influence of different ecological drivers on the number of species in a place remains limited. Assessing the relative influence of local ecological interactions versus regional species pools on local species richness should help bridge this conceptual gap. Plots of local species richness versus regional species pools have been used to address this question, yet after an active quarter-century of research on the relative influence of local interactions versus regional species pools, consensus remains elusive. We propose a conceptual framework that incorporates spatial scale and ecological interaction strength to reconcile current disparities. We then test this framework using a survey of marine rocky intertidal algal and invertebrate communities from the northeast Pacific. We reach two main conclusions. First, these data show that the power of regional species pools to predict local richness disintegrates at small spatial scales coincident with the scale of biological interactions, when studying ecologically interactive groups of species, and in generally more abiotically stressful habitats (e.g., the high intertidal). Second, conclusions of past studies asserting that the regional species pool is the primary driver of local species richness may be artifacts of large spatial scales or ecologically noninteractive groups of species.

I report a simulation study that tested the ability of a variety of experimental designs to achieve two fundamental goals: (1) to determine the association between loss of biological diversity and responses such as ecosystem functioning and (2) to determine which components of biodiversity, such as number of species, functional diversity, or a keystone species, were most responsible for that association. For the goal of reliably detecting an overall association, all designs I tested performed well and were unlikely to misidentify predominant patterns. Thus, this study affirms the common conclusion of many published biodiversity experiments that loss of biological diversity is often associated with a reduction in ecosystem functioning. However, for the goal of identifying the components of biodiversity that are most responsible for the effects, designs differed markedly. Some designs performed well in detecting number-of-species effects but poorly in detecting effects of unique species or functional groups. No design tested was able to discriminate both numeric effects and compositional effects in all situations. Thus, this study demonstrates that interpreting results about mechanisms from biodiversity experiments will be critically dependent on an experiment's design.