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Levin, LA.  1984.  Life history and dispersal patterns in a dense infaunal polychaete assemblage: community structure and response to disturbance. Ecology. 65:1185-1200.   10.2307/1938326   AbstractWebsite

The effects of differing life histories on the dynamics of dispersal, recruitment,and population maintenance were investigated for a dense infaunal polychaete assemblage on the Kendall-Frost mudflat in Mission Bay, California. Polychaete life history features provided the framework for investigations of small-scale dispersal mechanisms, infaunal response to disturbance, and the spatial and temporal predictability of species' abundances. Field and laboratory studies revealed that Rhynchospio arenincola Hartman, Streblospio benedicti Webster, Exogone lourei Hartman, Fabricia limnicola Hartman, and Capitella spp. shared many life history traits which limited the range of dispersal. These included small adult size, brood protection, small brood size, and planktonic larval stages which were reduced or absent. Pseudopolydora paucibranchiata Okuda, and Polydora ligni Webster exhibited initial brood protection but had larger brood sizes and longer lived larvae. Small-scale dispersal was examined by studying patterns of larval availability, recruitment into settling cartons, and colonization of defaunated sediments. The role of dispersal in response to disturbance was examined for two levels of perturbation. Small-scale disturbance, commonly generated on the mudflat by ray foraging and human digging, was studied by artificially defaunating small (0.4-m^2) sediment patches. A severe storm and consequent raw sewage spill created an episodic large-scale perturbation in the middle year of the 3-yr study. Analyses of species' responses revealed colonization ability at recruitment to be distinct from dispersal (migratory) ability. Rates and mechanisms of colonization were governed by larval development, settlement, and mobility patterns and varied with the scale of perturbation. For R. Arenincola, S. benedicti, E. Lourei, and F. Limnicola, factors such as brood protection, reduced planktonic larval phases, and postlarval movements, particularly by brooding adults, confer small-scale dispersal abilities which permit rapid colonization of disturbed patches and result in maintenance of high infaunal densities (>200,000 individuals/m^2). P. Paucibranchiata and P. Ligni possess long-lived larvae whose planktonic abundances are highly seasonal and variable from year to year. The timing of disturbance must coincide with periods of peak larval availability for successful colonization by these species. In general, the annual life cycles and flexible small-scale mobilities of most species enable persistence in the face of frequent fine-grained disturbance.

Fodrie, FJ, Levin LA.  2008.  Linking juvenile habitat utilization to population dynamics of California halibut. Limnology and Oceanography. 53:799-812.   10.4319/lo.2008.53.2.0799   AbstractWebsite

We investigated the nursery role of four coastal ecosystems for the California halibut (Paralichthys californicus) using the following metrics: (1) contribution in producing the fish that advance to older age classes, (2) connectivity of coastal systems resulting from migration of fish from juvenile to subadult habitats, and (3) effect of nursery habitat usage and availability on subadult population size, specifically evaluating the concentration hypothesis. Potential nurseries were grouped using a robust classification scheme that segregated exposed, bay, lagoon, and estuarine environments. Assignment of nursery origins for individual subadult fish via elemental fingerprinting indicated that exposed coasts, bays, lagoons, and estuaries contributed 31%, 65%, 1%, and 3% of advancing juvenile halibut during 2003, versus 49%, 33%, 16%, and 2% during 2004, respectively. These results were remarkably similar to "expected'' nursery contributions derived from field surveys, suggesting that in this system juvenile distributions were a good indicator of unit-area productivity of juvenile habitats and that density-dependent mechanisms during the juvenile phase did not regulate recruitment pulses. Elemental fingerprinting also demonstrated that individuals egressing from bays did not migrate far from their nursery origins (, 10 km), resulting in reduced connectivity along the 110-km study region over the timescale of approximately one generation. Consequently, we observed considerably higher subadult densities at sites near large bays, while populations distant from large bays appeared to be more influenced by nursery habitat limitation. Over large (similar to 100 km) scales, the location and availability of nursery habitat alternatives had significant effects on the population dynamics of an important member of the ichthyofaunal community of southern California.

Jeffreys, RM, Levin LA, Lamont PA, Woulds C, Whitcraft CR, Mendoza GF, Wolff GA, Cowie GL.  2012.  Living on the edge: single-species dominance at the Pakistan oxygen minimum zone boundary. Marine Ecology Progress Series. 470:79-99.   10.3354/meps10019   AbstractWebsite

Oxygen minimum zones (OMZs) are naturally occurring, low-oxygen water masses that create hypoxic conditions where they impinge on the seafloor. Their lower boundaries are characterised by elevated densities of hypoxia-tolerant fauna and an abundant food supply. The polychaete Linopherus sp. nov. (Amphinomidae) is the dominant taxon at the Pakistan margin (PM) lower OMZ, at near suboxic dissolved oxygen (DO) concentrations of 5 to 8 µM. We explored the response of Linopherus sp. nov. to gradients in oxygen and organic matter (OM) availability from depths of 700 to 1100 m during the inter- and late monsoon periods. Linopherus sp. nov. was present from 800 to 1000 m, and highest densities were found at 850 m. Population size structuring was evident and smaller individuals were present at depths of lowest DO concentrations. Linopherus sp. nov. showed morphological adaptation to low DO, and respiratory surface areas were significantly larger in worms at sites of lowest DO concentrations. Stable carbon isotopes (δ13C) revealed that Linopherus sp. nov. feeds mainly on sedimentary OM while enriched δ15N values suggest that Linopherus sp. nov. also utilises predation as a foraging strategy. Lipid biomarkers indicate an omnivorous lifestyle, in which Linopherus sp. nov. uses phytodetrital, bacterial and invertebrate/carrion food sources. Pulse-chase experiments demonstrated that Linopherus sp. nov. consumes phytodetritus and contributes significantly to OM processing, potentially altering OM quality and thus the availability of food resources to the benthic community. Severe oxygen stress leads to single-species dominance, which in turn simplifies macrofaunal ecosystems and thus reduces trophic complexity.