Current concepts of the role of interspecific interactions in communities have been shaped by a profusion of experimental studies of interspecific competition over the past few decades. Evidence for the importance of positive interactions — facilitations — in community organization and dynamics has accrued to the point where it warrants formal inclusion into community ecology theory, as it has been in evolutionary biology.

https://www.cell.com/trends/ecology-evolution/pdf/0169-5347(94)90088-4.pdf

Positive interactions in communities.

The worldwide decline of coral reefs calls for an urgent reassessment of current management practices. Confronting large-scale crises requires a major scaling-up of management efforts based on an improved understanding of the ecological processes that underlie reef resilience. Managing for improved resilience, incorporating the role of human activity in shaping ecosystems, provides a basis for coping with uncertainty, future changes and ecological surprises. Here we review the ecological roles of critical functional groups (for both corals and reef fishes) that are fundamental to understanding resilience and avoiding phase shifts from coral dominance to less desirable, degraded ecosystems. We identify striking biogeographic differences in the species richness and composition of functional groups, which highlight the vulnerability of Caribbean reef ecosystems. These findings have profound implications for restoration of degraded reefs, management of fisheries, and the focus on marine protected areas and biodiversity hotspots as priorities for conservation.

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Confronting the coral reef crisis

A heuristic framework for understanding and predicting the distribution and categorical abundance of species in stream communities is presented. The framework requires that species be described in terms of their functional relationships to habitat selective forces or their surrogates, which constitute "filters" occurring at hierarchical landscape scales (ranging from microhabitats to watersheds or basins). Large-scale filters are viewed as causative or mechanistic agents that constrain expression of local selective forces or biotic potential at lower scales. To join a local community, species in a regional pool must possess appropriate functional attributes (species traits) to "pass" through the nested filters. Biotic interactions are also a potential filter on local community composition, and they are invoked at the lower hierarchical levels, after species have passed through the physicochemical habitat filters. Potential landscape filters and their associated selective properties are identified, as are ...

Landscape filters and species traits: Towards mechanistic understanding and prediction in stream ecology

Summary 1. The goal of conservation and restoration activities is to maintain biological diversity and the ecosystem services that this diversity provides. These activities traditionally focus on the measures of species diversity that include only information on the presence and abundance of species. Yet how diversity influences ecosystem function depends on the traits and niches filled by species. 2. Biological diversity can be quantified in ways that account for functional and phenotypic differences. A number of such measures of functional diversity (FD) have been created, quantifying the distribution of traits in a community or the relative magnitude of species similarities and differences. We review FD measures and why they are intuitively useful for understanding ecological patterns and are important for management. 3. In order for FD to be meaningful and worth measuring, it must be correlated with ecosystem function, and it should provide information above and beyond what species richness or diversity can explain. We review these two propositions, examining whether the strength of the correlation between FD and species richness varies across differing environmental gradients and whether FD offers greater explanatory power of ecosystem function than species richness. 4. Previous research shows that the relationship between FD and richness is complex and context dependent. Different functional traits can show individual responses to different gradients, meaning that important changes in diversity can occur with minimal change in richness. Further, FD can explain variation in ecosystem function even when richness does not. 5. Synthesis and applications. FD measures those aspects of diversity that potentially affect community assembly and function. Given this explanatory power, FD should be incorporated into conservation and restoration decision-making, especially for those efforts attempting to reconstruct or preserve healthy, functioning ecosystems.

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Beyond species: functional diversity and the maintenance of ecological processes and services

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

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Kelp forest ecosystems: biodiversity, stability, resilience and future

Grime's approach to plant ecology (e.g., Grime 1981) has stimulated considerable interest and debate because it offers a promising way to unify the field by allowing comparisons to be made beyond the bounds of biogeography or even between the fundamentally different marine and terrestrial realms. Grime's comment on our paper (Steneck and Dethier 1994) initiates the discussion we had hoped for by raising some interesting questions; however, it also presents what we believe is an important misinterpretation of what we said. We chose to reply to Grime's comment for the sake of clarification and to pursue what we view as the more important question of whether fundamentally different plant strategies dominate under parallel environmental conditions in marine and terrestrial realms. Grime questioned the existence of disturbance-tolerant plants as a distinctly different plant functional type or "primary strategy". He maintains that "fast-growing ephemerals of high fecundity (ruderals) occupy high productivity-high disturbance" habitats whereas we "allocate this position to disturbance-tolerant perennial organisms..." Grime offers three interesting possible explanations; however, before we address them, we would like to add a fourth: Grime may not fully appreciate the distinction between "disturbance" and our new phrase "disturbance potential". We devoted an entire section to our definition of terms because we think there are conceptual limitations with current terminology. We agree with Grime that if one considers the strategy likely to succeed under high levels of "disturbance" (i.e., factors resulting in biomass loss sensu Grime 1981), then most likely ruderals will dominate. Disturbances (i.e., biomass lost) from any source when it exceeds rates of production will result in the elimination of the plant. Under such environments, plants capable of rapid colonization, growth and early reproduction (i.e., ruderals) will likely dominate the flora. The problem we saw in using "disturbance" (sensu Grime) as an extrinsic forcing function for community structure was that its impact depends on the intrinsic properties of the recipient plants in the community. For example, disturbances measured as biomass lost from browsing deer or from forest fires will impact lichens, grasses, shrubs and trees differently even when all are equally exposed to the same agent of disturbance. If these agents have no negative impact on the biomass of a plant, then, by definition, there is no disturbance. Thus, highly disturbance-resistant organisms, if they lose no biomass, cannot be disturbance tolerant because, strictly speaking, they experience no disturbance. Alternatively, we suggested that even without measurable biomass loss there can be a "disturbance potential" of the environment. We emphasized this concept:

Are Functional Classifications Different for Marine vs Terrestrial Plants? A Reply to Grime

Figure 1. Map of the 2001 sample sites. Figure 2. Species richness at the south and east-central Sound sites over 3 years. Figure 3. Cumulative species-richness curves for 3 years at each of the sites sampled in 2001. Figure 4. Species-area curves for each area sampled in 1999 and 2001. Figure 5. Species richness at all sites sampled in 2001. Figure 6. Percentage of the number of taxa that showed significant variation at different levels of analysis. Figure 7. Ordinations of community similarities among years, basins, sites, and transects for the south sound and east side sites. Figure 8. Contour plot of sea surface salinity in June 1999. Figure 9. Results of community similarity ordinations for the basins, sides, and quadrants of Puget Sound. Figure 10. Community ordination at the high-resolution species level, showing sites by site-code. Figure 11. Community ordination from the pristine vs. degraded mud sites. Figure 12. Community-similarity ordinations for the 2001 data based on different levels of resolution. Figure 13. Species richness and Shannon's Diversity index for 2001 sites sampled at high and low resolution. Figure 14. Coefficients of variation for transects across years for 5 common taxa. Figure 15. Coefficients of variation for sites in 2001, based on values at 3 transects per site. Figure 16. Coefficients of variation for three species of capitellid polychaete, based on 21 transects with at least 3 years of data (1999-2001). Figure 17. Coefficients of variation for three species of capitellid polychaete, based on 13 sites with at least 3 transects in 2001. Figure 18. Coefficient of variation for species richness in cores. Figure 19. Coefficient of variation for univariate metrics of assemblage composition in cores. Figure 20. Coefficient of variation for species richness in quadrat cover. Figure 21. Coefficient of variation for univariate metrics of assemblage composition in quadrat cover. Figure 22. Coefficient of variation for species richness in quadrat counts. Figure 23. Coefficient of variation for univariate metrics of assemblage composition in quadrat counts. iii LIST OF TABLES Table 1. Number of low-resolution taxa in each of 5 north-south distribution pattern categories, and each of 10 level-of-variation categories. Table 2. Species contributing more than 2% to the dissimilarity between pristine and degraded beaches. Table 3. Results of ordinations of 2001 data at different taxonomic levels. Table 4. Summary of results of principal components analysis of 13 normalized univariate metrics of community structure. LIST OF APPENDICES (all digital …

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Spatial and Temporal Variability of Shoreline Biota in South and Central Puget Sound; 2001 samples and analyses

Coastal seas and estuaries are among the most productive ecosystems on Earth and have long attracted human activity. Yet, urbanization pressures are intense and are compounded by accelerating climate stresses. Urban seas are now hotspots of stress in the Anthropocene ocean. The Salish Sea stands out as one of a few highly functioning urban seas in the world, boasting ecological riches and thriving coastal communities and industries, including tourism. For over 10,000 years the region has supported Indigenous peoples; now it is home to a growing population of almost nine million people, concentrated in and near the major cities of Seattle, Washington, and Vancouver, British Columbia. Increasing urbanization combined with intensifying climate stress is degrading the Salish Sea and acutely affecting communities already experiencing marginalization. Current environmental impacts include acidifying waters, hypoxia, and intense heat waves, all of which have had measurable impacts within the ecosystem. A recent synthesis of this system identified key domains for solutions, which we generalize here for invoking positive change in global urban seas: 1) innovation in data collection, curation, and integration using a systems approach in science and management; 2) sharing place-based knowledge to sustain community-based action; and 3) aligning science and policy with ecosystem boundaries. The differing governance and socio-political settings across two countries and numerous Indigenous nations creates a complex challenge in ecosystem management. Developing actionable solutions for people and the biota of the Salish Sea can create a global example of a sustainably managed urban sea with transferable insights to other urban seas in need of revitalization around the world.

Urban seas as hotspots of stress in the Anthropocene ocean: The Salish Sea example

An Analysis of San Juan River Otter (Lontra canadensis) Diets

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Megan N. Dethier

Papers

Are Functional Classifications Different for Marine vs Terrestrial Plants? A Reply to Grime

Spatial and Temporal Variability of Shoreline Biota in South and Central Puget Sound; 2001 samples and analyses

Urban seas as hotspots of stress in the Anthropocene ocean: The Salish Sea example

An Analysis of San Juan River Otter (Lontra canadensis) Diets

Southern Salish Sea Habitat Map Series: Admiralty Inlet