Publications

Export 29 results:
Sort by: Author Title Type [ Year  (Desc)]
2016
Novoa, A, Talley TS, Talley DM, Crooks JA, Reyns NB.  2016.  Spatial and temporal examination of bivalve communities in several estuaries of Southern California and Northern Baja California, MX. Plos One. 11   10.1371/journal.pone.0148220   AbstractWebsite

A combination of historical bivalve surveys spanning 30-50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

2015
Talley, DM, Talley TS, Blanco A.  2015.  Insights into the establishment of the manila clam on a tidal flat at the southern end of an introduced range in Southern California, USA. Plos One. 10   10.1371/journal.pone.0118891   AbstractWebsite

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam's post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e. g., riprap, boulders). We measured likely environmental influences (e. g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.

2014
Nordstrom, MC, Currin CA, Talley TS, Whitcraft CR, Levin LA.  2014.  Benthic food-web succession in a developing salt marsh. Marine Ecology Progress Series. 500:43-U69.   10.3354/meps10686   AbstractWebsite

Ecological succession has long been a focal point for research, and knowledge of underlying mechanisms is required if scientists and managers are to successfully promote recovery of ecosystem function following disturbance. We addressed the influence of bottom-up processes on successional assemblage shifts in salt marshes, ecosystems with strong physical gradients, and how these shifts were reflected in the trophic characteristics of benthic fauna. We tracked the temporal development of infaunal community structure and food-web interactions in a young, created salt marsh and an adjacent natural marsh in Mission Bay, California, USA (1996-2003). Macro faunal community succession in created Spartina foliosa habitats occurred rapidly, with infaunal densities reaching 70% of those in the natural marsh after 1 yr. Community composition shifted from initial dominance of insect larvae (surface-feeding microalgivores) to increased dominance of oligo chaetes (subsurface-feeding detritivores) within the first 7 yr. Isotopic labeling of microalgae, N-2-fixing cyanobacteria, S. foliosa and bacteria revealed direct links (or absence thereof) between these basal food sources and specific consumer groups. In combination with the compositional changes in the macroinvertebrate fauna, the trophic patterns indicated an increase in food-web complexity over time, reflecting resource-driven marsh succession. Natural abundance stable isotope ratios of salt marsh consumers (infaunal and epifaunal macroinvertebrates, and fish) initially reflected distinctions in trophic structure between the created and natural marsh, but these diminished during successional development. Our findings suggest that changing resource availability is one of the important drivers of succession in benthic communities of restored wetlands in Southern California.

Cook, RW, Talley TS.  2014.  The invertebrate communities associated with a Chrysanthemum coronarium-invaded coastal sage scrub area in Southern California. Biological Invasions. 16:365-380.   10.1007/s10530-013-0526-8   AbstractWebsite

The escape of ornamental plants is a main pathway of invasion into many ecosystems. Non-native plants can alter basal resources and abiotic factors leading to effects that ripple throughout an ecosystem. Invertebrates mediate these effects-responding quickly to abiotic and primary producer changes and, in turn, influencing other species. Invasions are of particular concern in the coastal sage scrub ecosystems of Southern California, where habitat loss and urban encroachment increase invasive species propagule sources and decrease native community resistance. The introduced annual Chrysanthemum coronarium (crown daisy) is a common invader with largely undocumented community-level effects. Our study tested the relationships between the invasive Chrysanthemum and a coastal scrub invertebrate community using a field study at the Tijuana River Estuary. We found similar or lower abundances and diversity of canopy fauna in the presence of Chrysanthemum. Community composition dramatically differed, however, in the presence Chrysanthemum, which was associated with higher abundances of dipterans, wasps and flower beetles, and lower abundances of hemipterans and thysanopterans than native shrubs. Differences in communities were consistent at the species- and order-levels, and were associated with the generally greater plant biomass and shadier conditions afforded by the natives. This study reveals that even a proportionally small amount of Chrysanthemum may shift the invertebrate community through alterations of abiotic properties and plant biomass. We recommend that Chrysanthemum be removed at the first sign of invasion or that spread is prevented since effects on the invertebrate community are dramatic and occur quickly.

2012
Talley, TS, Nguyen KC, Nguyen A.  2012.  Testing the Effects of an Introduced Palm on a Riparian Invertebrate Community in Southern California. Plos One. 7   10.1371/journal.pone.0042460   AbstractWebsite

Despite the iconic association of palms with semi-arid regions, most are introduced and can invade natural areas. Along the San Diego River (San Diego, California, USA), the introduced Canary Island date palm (Phoenix canariensis) forms dense patches among native riparian shrubs like arroyo willow (Salix lasiolepis). The structural differences between the palm and native shrubs are visually obvious, but little is known about palm's effects on the ecosystem. We tested for the effects of the palm on a riparian invertebrate community in June 2011 by comparing the faunal and environmental variables associated with palm and willow canopies, trunks and ground beneath each species. The palm invertebrate community had lower abundance and diversity, fewer taxa feeding on the host (e.g., specialized hemipterans), and more taxa likely using only the plant's physical structure (e.g., web-builders, oak moths, willow hemipterans). There were no observed effects on the ground-dwelling fauna. Faunal differences were due to the physical and trophic changes associated with palm presence, namely increased canopy density, unpalatable leaves, trunk rugosity, and litter accumulations. Palm presence and resulting community shifts may have further ecosystem-level effects through alteration of physical properties, food, and structural resources. These results were consistent with a recent study of invasive palm effects on desert spring arthropods, illustrating that effects may be relatively generalizable. Since spread of the palm is largely localized, but effects are dramatic where it does occur, we recommend combining our results with several further investigations in order to prioritize management decisions.

2011
Currin, CA, Levin LA, Talley TS, Michener R, Talley D.  2011.  The role of cyanobacteria in Southern California salt marsh food webs. Marine Ecology-an Evolutionary Perspective. 32:346-363.   10.1111/j.1439-0485.2011.00476.x   AbstractWebsite

Understanding wetland food webs is critical for effective habitat management, restoration and conservation. Microalgae are recognized as key food sources for marsh invertebrates but the importance of different groups under various conditions is rarely examined. We tested the hypothesis that faunal utilization of microalgae, and cyanobacteria in particular, is significant in Southern California created and natural salt marshes but varies with habitat type (creek bank versus marsh interior) and season (spring versus autumn). We used stable isotope analysis and mixing models (IsoSource) to compare food webs in adjacent young (created) and mature (natural) salt marshes. Isotopic values of some primary producers, macrofauna, epifauna, and fish demonstrated significant differences between the adjacent salt marshes. delta C-13 and delta S-34 values of the benthic microalgal community varied with taxonomic composition (diatoms versus cyanobacteria) and to a lesser extent with season. Depleted delta N-15 values of benthic diatoms and macroalgae indicated that N-2 fixed within algal mats was recycled within the benthic algal community. Marsh fauna, including most major macrofauna taxal, Cerithidea, and Fundulus, also exhibited seasonal differences in isotopic composition, and Cerithidea and selected macrofauna (oligochaetes, polychaetes) from the marsh interior were more enriched in C-13 and depleted in N-15 than those from the creek bank. In the young marsh, the cyanobacteria contributed a minimum of 17-100% of the primary production in food webs supporting macrofauna, and cyanobacteria contributed at least 40% of the primary production included in Cerithidea and Fundulus food webs. A wider range of primary producers contributed to food webs in the mature marsh. Cyanobacteria were a greater source of trophic support for macrofauna from the marsh interior than the creek bank, whereas Spartina was a more important food source for creek bank macrofauna in both marshes. Insect larvae largely consumed cyanobacteria, whereas polychaetes exhibited greater utilization of Spartina. Phytoplankton was the primary food resource for mussels in both marshes. Although the spatial and temporal complexity of food webs has traditionally been collapsed into the study of relatively simplified food webs, isotope signatures reveal fine-scale patterns in food web structure that may be used to make more accurate assessments of ecosystem state. Accurate interpretation of marsh trophic structure using natural abundance stable isotopes requires fine-scale resolution in space and time, a large number of samples, and a high level of taxonomic resolution.

2010
Jones, CG, Gutierrez JL, Byers JE, Crooks JA, Lambrinos JG, Talley TS.  2010.  A framework for understanding physical ecosystem engineering by organisms. Oikos. 119:1862-1869.   10.1111/j.1600-0706.2010.18782.x   AbstractWebsite

While well-recognized as an important kind of ecological interaction, physical ecosystem engineering by organisms is diverse with varied consequences, presenting challenges for developing and using general understanding. There is also still some uncertainty as to what it is, and some skepticism that the diversity of engineering and its effects is amenable to conceptual integration and general understanding. What then, are the key cause/effect relationships and what underlies them? Here we develop, enrich and extend our extant understanding of physical ecosystem engineering into an integrated framework that exposes the essential cause/effect relationships, their underpinnings, and the interconnections that need to be understood to explain or predict engineering effects. The framework has four cause/effect relationships linking four components: 1. An engineer causes structural change; 2. Structural change causes abiotic change; 3. Structural and abiotic change cause biotic change; 4. Structural, abiotic and biotic change can feedback to the engineer. The first two relationships describe an ecosystem engineering process and abiotic dynamics, while the second two describe biotic consequence for other species and the engineer. The four relationships can be parameterized and linked using time-indexed equations that describe engineered system dynamics. After describing the relationships we discuss the utility of the framework; how it might be enriched; and briefly how it can be used to identify intersections of ecosystem engineering with fields outside ecology.

Holyoak, M, Talley TS, Hogle SE.  2010.  The effectiveness of US mitigation and monitoring practices for the threatened Valley elderberry longhorn beetle. Journal of Insect Conservation. 14:43-52.: Springer Netherlands   10.1007/s10841-009-9223-4   AbstractWebsite

Habitat mitigation frequently leads to planting of new habitat, assuming that it can replace lost natural habitat. Yet this practice has rarely been examined in detail. In the USA habitat mitigation is frequently allowed under the US Endangered Species Act, providing monitoring reports which represent a potentially valuable data source for imperiled species. We used publicly available reports for the US threatened Valley elderberry longhorn beetle (Desmocerus californicus dimorphus) to assess record keeping practices used by US Fish and Wildlife Service (FWS), and the utility of such analyses for improving conservation. A large portion of mitigation reports known to exist were missing from FWS files, indicating problems with data management, and a loss of important information. Transplanted brought mature beetle host plants and beetles to sites, promoting beetle colonization. Conversely, few sites with seedlings were colonized. Results indicate a need for improved data management by FWS and longer term monitoring.

2009
Fremier, AK, Talley TS.  2009.  Scaling riparian conservation with river hydrology: Lessons from blue elderberry along four California rivers. Wetlands. 29:150-162.   10.1672/07-243.1   AbstractWebsite

Conservation frequently requires the preservation or restoration of ecosystems in human-altered landscapes. Understanding, these ecosystems requires matching patterns with processes at appropriate scales. Oil floodplains this necessitates coupling plant distributions with fine- and broad-scale hydrologic patterns. This is particularly important when target species are of conservation concern. such as the blue elderberry (Sambucus mexicana). Blue elderberry is the sole host plant for the federally threatened Valley elderberry longhorn beetle. yet controls oil file Sill-Lib's distribution have largely been untested. We used nested hierarchical analyses to test hypotheses about the role of broad- and fine-scale variables structuring 1 the distribution of elderberry in one undammed and three dammed rivers in California's Central Valley (USA). Elderberry presence across the floodplain,vas primarily driven by broad-scale hydrologic regime, as represented by the relative elevation, floodplain width, and lateral distance of shrubs from the stream, and secondarily by sediment texture and topography. The patchy spatial distributions of elderberry were similar among the rivers, but habitat quality characteristics (i.e., controls on abundance and size) were driven by divergent variables with high stochasticity. We can improve our understanding of species distributions and outcomes of recovery efforts by scaling floodplain conservation efforts to broad-scale hydrologic patterns and by detecting crucial variables using a multi-scale methodology. Within these relatively large, self-defined landscape units. certain precautions and the application of an adaptive management approach could be employed to address the local-scale uncertainty in large-scale conservation efforts.

Vaghti, M, Holyoak M, Williams A, Talley T, Fremier A, Greco S.  2009.  Understanding the Ecology of Blue Elderberry to Inform Landscape Restoration in Semiarid River Corridors. Environmental Management. 43:28-37.   10.1007/s00267-008-9233-0   AbstractWebsite

Societal constraints often limit full process restoration in large river systems, making local rehabilitation activities valuable for regeneration of riparian vegetation. A target of much mitigation and restoration is the federally threatened Valley elderberry longhorn beetle and its sole host plant, blue elderberry, in upper riparian floodplain environments. However, blue elderberry ecology is not well understood and restoration attempts typically have low success rates. We determined broad-scale habitat characteristics of elderberry in altered systems and examined associated plant species composition in remnant habitat. We quantified vegetation community composition in 139 remnant riparian forest patches along the Sacramento River and elderberry stem diameters along this and four adjacent rivers. The greatest proportion of plots containing elderberry was located on higher and older floodplain surfaces and in riparian woodlands dominated by black walnut. Blue elderberry saplings and shrubs with stems < 5.0 cm in diameter were rare, suggesting a lack of recruitment. A complex suite of vegetation was associated with blue elderberry, including several invasive species which are potentially outcompeting seedlings for light, water, or other resources. Such lack of recruitment places increased importance on horticultural restoration for the survival of an imperiled species. These findings further indicate a need to ascertain whether intervention is necessary to maintain functional and diverse riparian woodlands, and a need to monitor vegetative species composition over time, especially in relation to flow regulation.

2008
Talley, DM, Talley TS.  2008.  Salinity. Encyclopedia of Ecology. ( Editors-in-Chief:  Sven Erik J, Brian F, Eds.).:3127-3132., Oxford: Academic Press   10.1016/B978-008045405-4.00541-3   Abstract

Salt plays a critical role in both terrestrial and aquatic ecosystems, being an essential element of all living organisms, but also bearing the potential to cause stress or death when present in quantities either above or below certain limits. Here we discuss the origin and role of salt in ecosystems, and how salinity varies across a broad range of spatial and temporal scales.

2007
Talley, TS.  2007.  Which spatial heterogeneity framework? Consequences for conclusions about patchy population distributions Ecology. 88:1476-1489.   10.1890/06-0555   AbstractWebsite

Patches, gradients, and hierarchies are three common organizational frameworks for assessing the effects of spatial heterogeneity on species distributions. Since these frameworks are often chosen a priori, without knowledge of study systems, they may not correspond to the empirical heterogeneity present and may result in partial or erroneous conclusions about the forces structuring species distributions. I tested the consequences of choosing particular frameworks and whether patch heterogeneity structured patchily distributed populations of the valley elderberry longhorn beetle (Desmocerus californicus dimorphus) along four rivers in California's Central Valley (USA). A comparison of the three approaches revealed that each led to incomplete conclusions about controls on the beetle's distribution and populations. Patch analysis revealed weak effects of patch size and quality, and high unexplained variance, which likely reveals large amounts of stochasticity since replication was high. The patch analysis therefore concluded that distributions consistent with patch dynamic structures like classic metapopulation, source-sink, and mainland-island models existed in the different rivers. Conversely, gradient analyses revealed a gradient-distribution pattern responding to continuous and often large-scale variables, such as hostplant age or size, water availability, and the presence of an invasive leguminous tree; again most variance in beetle occurrence remained unexplained. Hierarchical analysis identified the natural spatial patterns of the system but gave no indication of causal processes. The combination of all three approaches explained the maximum variance in beetle occurrence, through inclusion of a comprehensive list of explanatory variables, multiple spatial scales, various types of heterogeneity, and a focus on the scales at which beetle-environment interactions were strongest. Surprisingly, these results still supported the notion that the beetle exists as a metapopulation, a structure thought to be rare because it ignores habitat quality and landscape conditions. These analyses exemplify the simultaneous importance of local patch attributes and broad-scale and/or gradient variables that are commonly overlooked in patch studies. Importantly, some patch attributes acted over inter-patch scales, affecting the perception of patch distances and distributional extents. Only through the integration of frameworks was I able to decipher the system's complexity and see that all three types of heterogeneity were acting in the system, sometimes over unexpected scales.

Hastings, A, Byers JE, Crooks JA, Cuddington K, Jones CG, Lambrinos JG, Talley TS, Wilson WG.  2007.  Ecosystem engineering in space and time. Ecology Letters. 10:153-164.   10.1111/j.1461-0248.2006.00997.x   AbstractWebsite

The ecosystem engineering concept focuses on how organisms physically change the abiotic environment and how this feeds back to the biota. While the concept was formally introduced a little more than 10 years ago, the underpinning of the concept can be traced back to more than a century to the early work of Darwin. The formal application of the idea is yielding new insights into the role of species in ecosystems and many other areas of basic and applied ecology. Here we focus on how temporal, spatial and organizational scales usefully inform the roles played by ecosystem engineers and their incorporation into broader ecological contexts. Two particular, distinguishing features of ecosystem engineers are that they affect the physical space in which other species live and their direct effects can last longer than the lifetime of the organism - engineering can in essence outlive the engineer. Together, these factors identify critical considerations that need to be included in models, experimental and observational work. The ecosystem engineering concept holds particular promise in the area of ecological applications, where influence over abiotic variables and their consequent effects on biotic communities may facilitate ecological restoration and counterbalance anthropogenic influences.

Talley, TS, Fleishman E, Holyoak M, Murphy DD, Ballard A.  2007.  Rethinking a rare-species conservation strategy in an urban landscape: The case of the valley elderberry longhorn beetle. Biological Conservation. 135:21-32.   10.1016/j.biocon.2006.09.022   AbstractWebsite

Reflecting the lack of critical information for most protected species, recovery plans for organisms listed as threatened or endangered under the U.S. Endangered Species Act tend to oversimplify habitat descriptions. Here we present our approach for improving the definition of habitat for rare and patchily distributed listed species. The valley elderberry longhorn beetle (Desmocerus californicus dimorphus) occurs in riparian and scrub communities in California's Central Valley. Habitat quality for the species currently is defined essentially exclusively in terms of presence and abundance of its larval host plant, elderberry (Sambucus spp.). Using detailed measures of physical and biological attributes at diverse sites occupied by the beetle, we characterized and defined habitat quality on the basis of not only host plants, but on an array of biotic and abiotic environmental characteristics. We identified four geornorphically distinct habitat associations: alluvial plain, narrow riparian corridor, upper riparian plain, and non-riparian scrub. Depending on habitat type, the environmental characteristics most strongly associated with beetle presence were host plant availability, topography and proximity to habitat edge. Increased local population size of beetles was associated with higher elderberry density and the presence of larger, more mature plants. Stochasticity in site occupancy over space and time confounds our ability to identify sites that are most able to contribute to long-term beetle survival, while underscoring the importance of unoccupied habitat to the beetle. Adopting a multivariate definition of habitat may facilitate more effective identification of locations critical to the recovery of the valley elderberry longhorn beetle, and prioritization of those management actions that can contribute effectively to meeting conservation goals for the species. (c) 2006 Elsevier Ltd. All rights reserved.

Talley, TS, Crooks JA.  2007.  9 Habitat conversion associated with bioeroding marine isopods. Ecosystem Engineers — Plants to Protists. Volume 4( Kim Cuddington JEG, Alan H, Eds.).:185–202,VI–VII.: Academic Press   10.1016/S1875-306X(07)80011-6   Abstract

Publisher Summary This chapter examines the engineering activities and their consequences for three types of marine isopods, Sphaeroma quoianum, S. terebrans, and Limnoria spp., on the biogenic marine habitats formed by marsh plants, mangroves, and kelp (respectively). The chapter also focuses on the case of S. quoianum and compares this example with the two other taxa. Each of these isopods has been anthropogenically spread around the world. Although these species represent conservation concerns, they also provide an opportunity for ecological insight afforded by the study of biological invasions. These isopods often perform their bioerosive activities in multiengineer systems, with the plants and kelp creating biogenic structure and the isopods removing it. Sometimes the activities may act directly on the physical environment, such as S. quoianum burrowing into unvegetated banks. However, the actual mechanisms by which they cause this loss of structure differ.

2006
Byers, JE, Cuddington K, Jones CG, Talley TS, Hastings A, Lambrinos JG, Crooks JA, Wilson WG.  2006.  Using ecosystem engineers to restore ecological systems. Trends in Ecology & Evolution. 21:493-500.   10.1016/j.tree.2006.06.002   AbstractWebsite

Ecosystem engineers affect other organisms by creating, modifying, maintaining or destroying habitats. Despite widespread recognition of these often important effects, the ecosystem engineering concept has yet to be widely used in ecological applications. Here, we present a conceptual framework that shows how consideration of ecosystem engineers can be used to assess the likelihood of restoration of a system to a desired state, the type of changes necessary for successful restoration and how restoration efforts can be most effectively partitioned between direct human intervention and natural ecosystem engineers.

Talley, TS, Holyoak M, Piechnik DA.  2006.  The effects of dust on the federally threatened Valley elderberry longhorn beetle. Environmental Management. 37:647-658.   10.1007/s00267-004-0320-6   AbstractWebsite

We combined a natural experiment with field surveys and GIS to investigate the effects of dust from recreational trails and access roads on the federally threatened Valley elderberry longhorn beetle ("VELB," Desmocerus californicus dimorphus) and its host plant, elderberry (Sambucus mexicana). Dust is listed in the species recovery plan as a threat to the VELB and unpaved surfaces are common throughout the riparian corridors where the VELB lives, yet the effects of dust on the VELB have been untested. We found that dust deposition varied among sites and was highest within 10 m of trails and roads, but was similar adjacent to dirt and paved surfaces within sites. Elderberry density did not differ with distance from dirt surfaces. Despite similar within-site dust levels, elderberry adjacent to paved surfaces were less stressed than those near dirt ones, possibly because increased runoff from paved surfaces benefited elderberry. Dust deposition across sites was weakly correlated with elderberry stress symptoms (e.g., water stress, dead stems, smaller leaves), indicating that ambient dust (or unmeasured correlates) influenced elderberry. Direct studies of the VELB showed that its distribution was not negatively affected by the proximity to dirt surfaces. Dust from low traffic dirt and paved access roads and trails, therefore, affected VELB presence neither directly nor indirectly through changed elderberry condition. These results suggest that the placement of VELB mitigation, restoration, and conservation areas can proceed independently of access roads if dust and traffic levels do not exceed those in our study site. Furthermore, dust control measures are likely to be unnecessary under such conditions. The potential effects of increased traffic and dust levels are addressed through a literature review.

2003
Hewitt, JE, Cummings VJ, Ellis JI, Funnell G, Norkko A, Talley TS, Thrush SF.  2003.  The role of waves in the colonisation of terrestrial sediments deposited in the marine environment. Journal of Experimental Marine Biology and Ecology. 290:19-47.   10.1016/s0022-0981(03)00051-0   AbstractWebsite

Elevated rates of sediment run-off, as a result of changes in land-use and climate, are a significant threat to marine coastal communities, with a potential to cause broad-scale, long-term alteration of habitats. Individual sedimentation events can smother estuarine Rats with terrigenous sediments, creating a significant disturbance to local benthic communities. Variations in the degree to which a habitat is altered, the rate at which mixing occurs, and species-specific dispersal and responses to the altered habitat, suggest that colonisation of terrestrial sediment depositions will vary with location, both between and within estuaries. This study was designed to explore the effect that variations in wave-induced hydrodynamics would have on long-term colonisation of terrestrial sediment depositions on intertidal flats. Sites for the experimental deposition of terrestrial sediment were located along a gradient in wave exposure, with only limited variation in immersion times (30 min) and ambient sediment particle sizes (predominantly fine sand). Over 20 months, periodic measurements were made of factors predicted to affect colonisation: the sediment characteristics of the deposited sediment; local-scale wave climate; bioturbation of the deposited sediment; and local populations of benthic invertebrates. Neither opportunistic use of the new resource, progressive recovery or facilitation by colonising macrofauna was observed. Little vertical mixing of the deposited and existing sediment by either waves or bioturbators occurred; instead bedload transport was the dominant process. Local differences in hydrodynamic conditions and macrobenthic communities resulted in site-specific colonisation of the experimental plots. The strength and duration of the macrofaunal response to deposited sediment observed in this study suggest that chronic small-scale (m's) patchy deposition of terrestrial sediment in the intertidal marine environment has a strong potential to alter both habitats and communities. (C) 2003 Elsevier Science B.V. All rights reserved.

2002
Levin, LA, Talley TS.  2002.  Natural and manipulated sources of heterogeneity controlling early faunal development of a salt marsh. Ecological Applications. 12:1785-1802.   10.2307/3099938   AbstractWebsite

Ecosystem recovery following wetland restoration offers exceptional opportunities to study system structure, function, and successional processes in salt marshes. This study used observations of natural variation and large-scale manipulative experiments to test the influence of vascular vegetation and soil organic matter on the rate and trajectory of macrofaunal recovery in a southern California created salt marsh, the Crown Point Mitigation Site. During the first three years following marsh establishment, macrofaunal density and species richness recovered rapidly within the Spartina foliosa (cordgrass) zone; densities in the created marsh were 50% of those in the natural marsh after 16 mo and 97% after 28 mo. However, the early successional assemblage had a lower proportion of tubificid and enchytraeid oligochaetes, and a higher proportion of chironomids and other insect larvae than did the mature natural marsh. Most of the colonizers arrived by rafting on sea grass and algae rather than by larval dispersal. Initial planting of S. foliosa had no influence on macrofaunal recovery, perhaps because of variable transplant survival. However, subsequently, both positive and negative correlations were observed between densities of some macrofaunal taxa and shoot densities of S. foliosa or Salicornia spp. (pickleweed). Salinity and measures of soil organics (belowground biomass, combustible organic matter, and chlorophyll a) also were correlated with macrofaunal densities and taxon richness. Of foul added soil amendments (kelp, alfalfa, peat, and Milorganite), Milorganite (a sewage product) and kelp both promoted macrofaunal colonization during year 1, but effects were short lived. The most significant sources of heterogeneity in the recovering marsh were associated with site history and climate variation. Faunal recovery was most rapid in highly localized, organic-rich marsh sediments that were remnants of the historical wetland. Elevated sea level during the 1998 El Nino corresponded with similarity of macrofaunal communities in the created and natural marshes. The large spatial scale and multi-year duration of this study revealed that natural sources of spatial and temporal heterogeneity may exert stronger influence on faunal succession in California wetlands than manipulation of vegetation or soil properties.

2001
Talley, TS, Crooks JA, Levin LA.  2001.  Habitat utilization and alteration by the invasive burrowing isopod, Sphaeroma quoyanum, in California salt marshes. Marine Biology. 138:561-573.   10.1007/s002270000472   AbstractWebsite

In recent years the pace of exotic species introduction and invasion has accelerated, particularly in estuaries and wetlands. Species invasions may affect coastal ecosystems in many ways. Alteration of sedimentary environments, through structure formation and burrowing, has particularly dramatic effects on coastal habitats. This study examines modification of channel bank and marsh edge habitat by the burrowing Australasian isopod Sphaeroma quoyanum Milne Edwards, in created and natural salt marshes of San Diego Bay and San Francisco Bay. Abundance and distribution patterns of this isopod species, its relationships with habitat characteristics, and its effects on sediment properties and bank erosion were examined seasonally, and in several marsh microhabitats. Mean isopod densities were 1541 and 2936 individuals per 0.25 m(2) in San Francisco Bay, and 361 and 1153 individuals per 0.25 m(2) in San Diego Bay study sites during December and July 1998, respectively. This isopod forms dense, anastomosing burrow networks. S. quoyanum densities did not differ as a function of location within creeks or location in natural versus created marshes. Burrows, which are on average 6 mm wide and 2 cm long, were associated with firm sediments containing high detrital biomass. Although erosion is a natural process along salt marsh banks, enclosure experiments demonstrated that isopod activities can enhance sediment loss from banks. In areas infested with S. quoyanum, losses may exceed 100 cm of marsh edge per year. The effects of habitat alteration by this invading species are likely to increase in severity in the coastal zone as these ecosystems become degraded.

Talley, TS, Levin LA.  2001.  Modification of Sediments and Macrofauna by an Invasive Marsh Plant. Biological Invasions. 3:51-68.: Springer   10.1023/A:1011453003168   AbstractWebsite

Invasive grasses have recently altered salt marsh ecosystems throughout the northern hemisphere. On the eastern seaboard of the USA, Phragmites australis has invaded both brackish and salt marsh habitats. Phragmites australis influence on sediments and fauna was investigated along a salinity and invasion-age gradient in marshes of the lower Connecticut River estuary. Typical salinities were about 19-24 ppt in Site I, 9-10 ppt in Site II and 5-7 ppt in Site III. Strongest effects were evident in the least saline settings (II and III) where Phragmites has been present the longest and exists in monoculture. Limited influence was evident in the most saline region (I) where Phragmites and native salt marsh plants co-occur. The vegetation within Phragmites stands in tidal regions of the Connecticut River generally exhibits taller, but less dense shoots, higher above-ground biomass, and lower below-ground biomass than does the un-invaded marsh flora. There were lower sediment organic content, greater litter accumulation and higher sediment chlorophyll a concentrations in Phragmites- invaded than un-invaded marsh habitat. Epifaunal gastropods (Succinea wilsoni and Stagnicola catascopium) were less abundant in habitats where Phragmites had invaded than in un-invaded marsh habitat. Macro-infaunal densities were lower in the Phragmites-invaded than un-invaded habitats at the two least saline sites (II and III). Phragmites stands supported more podurid insects, sabellid polychaetes, and peracarid crustaceans, fewer arachnids, midges, tubificid and enchytraeid oligochaetes, and greater habitat-wide taxon richness as measured by rarefaction, than did the un-invaded stands. The magnitude and significance of the compositional differences varied with season and with site; differences were generally greatest at the oldest, least saline sites (II and III) and during May, when faunal densities were higher than in September. However, experimental design and the 1-year study period precluded clear separation of salinity, age, and seasonal effects. Although structural effects of Phragmites on salt marsh faunas are evident, further investigation is required to determine the consequences of these effects for ecosystem function.

2000
Talley, TS, Dayton PK, Ibarra-Obando SE.  2000.  Tidal flat macrofaunal communities and their associated environments in estuaries of southern California and northern Baja California, Mexico. Estuaries. 23:97-114.   10.2307/1353228   AbstractWebsite

Several tidal flats in both Estero de Punta Banda and Bahia de San Quintin, Baja California, and one in Mission Bay, southern California, were sampled for macrofaunal properties (taxonomic composition, density, species richness, and functional groups for animals greater than or equal to 0.3 mm) and associated environmental variables (sediment properties, salinity, plant belowground biomass, and cover of Zostera marina) in order to establish a benchmark data set for these areas. The grouping of macrofauna into higher taxonomic or functional groups for these comparisons reduced variability and revealed stronger relationships. Each estuary had a fairly distinct macrofaunal assemblage, with that of Estero de Punta Banda being different from Bahia de San Quintin and Mission Bay primarily due to dominance by a capitellid polychaete, lower proportions of surface deposit feeders, and higher proportions of fauna with a planktonic stage. The flats in Mission Bq and Bahia de San Quintin were dominated by peracarid crustaceans, oligochaetes and polychaetes and had higher proportions of direct developers and macrofauna with mobile adult stages than did Estero de Punta Bands. There was an overlap of the environmental characteristics among estuaries, with more variability of sediment and vegetation properties within than among estuaries. Within Bahia. de San Quintin, there was an oceanic to back-bay distribution gradient of macrofauna that was similar to that found in estuaries in wetter climates, despite the lack of a salinity gradient in San Quintin. A decoupling of the benthos and the assumed anthropogenic stresses was observed with the degraded site, Mission Bay, being most similar to the relatively pristine Bahia de San Quintin. Selection of reference sites and sampling variables should be made cautiously because effects of disturbance factors on the benthos may be site-dependent, scale-dependent, or negligible.

Levin, LA, Talley T.  2000.  Influences of vegetation and abiotic environmental factors on salt marsh benthos. Concepts and controversies in tidal marsh ecology. ( Weinstein M, Kreeger D, Eds.).:661-708., New York: Kluwer Academic   10.1007/0-306-47534-0_30   Abstract

Sediment-dwelling fauna are a ubiquitous component of salt marshes yet we have limited understanding of their roles in marsh functioning and of the environmental conditions that control their distributions and abundances. This paper examines the influence of vegetation (presence, type, density, and biomass) and other environmental variables (marsh age, sediment and porewater properties, elevation, flow, oxygen, and biogenic structures) on salt marsh macrofauna and meiofauna. We review studies from a variety of geographical locations and include new information from systems with adjacent natural and restored sites in southern California. The influence of environmental factors on faunal assemblages varies with marsh system, factor intensity or concentration, taxon studied, and with other interacting factors present. We hypothesize a hierarchy of environmental variables in which abiotic properties such as marsh age, elevation and salinity act over large space and time scales, and are most likely to influence the presence or absence of species. Sediment properties (organic matter and particle size) and vegetation presence or type act on intermediate scales affecting macrofaunal abundance and composition. Plant biomass, culms and biogenic structures generated by fauna are patchy and act on small scales, often interacting with flow, to affect distribution and abundance patterns. Resolution of these processes in salt marshes should improve our understanding of controls on invertebrate communities and will ultimately aid the conservation and restoration of salt marsh habitat.

1999
Talley, TS, Levin LA.  1999.  Macrofaunal succession and community structure in Salicornia marshes of southern California. Estuarine Coastal and Shelf Science. 49:713-731.   10.1006/ecss.1999.0553   AbstractWebsite

Lack of basic understanding of ecosystem structure and function forms a major impediment to successful conservation of coastal ecosystems. This paper provides a description of the fauna and examines faunal succession in Salicornia-vegetated sediments of southern California. Environmental attributes (vegetation and sediment properties) and macrofaunal (animals greater than or equal to 0.3 mm) community structure were examined in sediments of five natural, southern California Salicornia spp. marshes (Tijuana Estuary, San Diego Bay, Mission Bay, Upper Newport Bay and Anaheim Bay) and in created Salicornia marshes 16 months to 10 years in age, located within four of the bays. Oligochaetes and insects were the dominant taxa in both natural (71 to 98% of total fauna) and created (91 to 97%) marshes. In San Diego, Newport and Anaheim Bays, macrofaunal densities were generally higher in the created marshes (88 000 to 290 000 ind m(-2)) than in their natural counterparts (26 000 to 50 000 ind m(-2)). In the youngest system, Mission Bay, the reverse was true (natural: 113 000 vs created: 28 000 ind m-2). Similar species numbers were recorded from the created and adjacent natural marshes. Insects, especially chironomids, dolichopodids, and heleids, as well as the naidid oligochaete, Paranais litoralis, characterize early successional stages. Enchytraeid and tubificid oligochaetes reflect later succession evident in natural and older created marshes. Sediment organic matter (both combustible and below-ground plant biomass) was the environmental variable most commonly associated with densities of various macrofaunal taxa. These relationships were generally negative in the natural marshes and positive in the created marshes. Within-bay comparisons of macrofauna from natural Salicornia- vs Spartina-vegetated habitat in San Diego and Mission Bays revealed lower macrofaunal density (San Diego Bay only), proportionally fewer oligochaetes and more insects, and no differences in species richness in the Salicornia habitat. The oldest created Salicornia marsh (San Diego Bay) exhibited an assemblage intermediate in composition between those of the natural Salicornia- and Spartina-vegetated marshes. These results suggest: (a) faunal recovery following Salicornia marsh creation can require 10 or more years, (b) high macrofaunal variability among bays requires marsh creation reference site selection from within the same bay, and (c) Spartina-based research should not be used for Salicornia marsh management decisions. (C) 1999 Academic Press.

1998
Levin, LA, Talley TS, Hewitt J.  1998.  Macrobenthos of Spartina foliosa (Pacific cordgrass) salt marshes in southern California: Community structure and comparison to a Pacific mudflat and a Spartina alterniflora (Atlantic smooth cordgrass) marsh. Estuaries. 21:129-144.   10.2307/1352552   AbstractWebsite

Environmental attributes (vegetation and sediment properties) of and macrofaunal community structure in sediments of five southern California Spartina foliosa marshes (San Diego Bay, Mission Bay, Upper Newport Bay, Bolsa Chica Lagoon, and Anaheim Bay) were examined during October 1994. Macrofaunal densities in Pacific S. foliosa marshes (avg. 122,268 indiv. m(-2) > 300 mu m) were 3 to 10 times higher than observed in Atlantic S. alterniflora and S. anglica marshes. The macrofauna of S. foliosa marshes was composed mainly of enchytraeid, naidid, and tubificid oligochaetes (66%), with the enchytraeids dominant at all sites except Bolsa Chica Lagoon. Polychaetes, insects, and peracarid crustaceans accounted for most of the remaining fauna. Multivariate analyses indicated greatest faunal similarity between the two southernmost marshes (Mission Bay and San Diego Bay), and between Anaheim and Newport Bay marshes, with Bolsa Chica Lagoon exhibiting a distinct assemblage. There were strong positive associations of faunal abundance and composition with percent organic matter and percent open area, and negative associations with percent sand and dry weight of algae. For the vegetated marsh in Mission Bay, faunal comparisons were made with an adjacent mudflat and with a S. alterniflora marsh in North Carolina, USA. The unvegetated mudflat exhibited similar macrofaunal densities but higher species richness than the adjacent Spartina marsh. The macrofaunal assemblage of the Mission Bay S. foliosa marsh differed from that of the Atlantic S. alterniflora marsh and the Pacific mudflat in having a greater proportion of oligochaetes, especially Enchytraeidae, and fewer polychaetes. This study represents the first published description that we are aware of for macrofauna in S. foliosa vegetated marsh sediments. The findings document faunal variation among southern California embayments and suggest that differences in macrobenthic community structure occur between marsh and mudflat habitat as web as between east and west coast Spartina marshes. Observed differences may have significant implications for wetland conservation and restoration efforts.