ABSTRACT1. Rhodolith beds, unattached coralline reefs, support a high diversity and abundance of marine species from both hard and soft benthos. We used surveys in multiple shallow (3-20 m) beds in the Gulf of California to (1) examine seasonal patterns in associated floral and faunal diversity and abundance, (2) compare differences in faunal associations between rhodolith beds and adjacent sedimentary habitats, (3) examine the importance of complexity of rhodolith structure to community structure, and (4) estimate the impact of anthropogenic disturbance on rhodoliths and associated species.2. Macroalgal richness was seasonal, and beds supported higher richness in winter (to 36 species) than summer (6-7 species), primarily due to foliose red algae. Strong seasonal variation in the abundance of dominant cover organisms was due to a shift from macroalgae and mat-forming colonial invertebrate species to microalgae.3. The community in a rhodolith bed of high-density thalli (El Coyote average $11000 thalli/ m À2 ) had higher richness (52 versus 30 species) and abundance of epibenthic and crypto-and infaunal species compared with an adjacent sand community. Species diversity and abundance was particularly high for unique cryptofaunal organisms associated with rhodolith interstices. Cryptofauna reached average densities of 14.4 organisms/ cm À3 rhodolith, the majority of which were crustaceans, polychaetes and cnidarians along with rhodolith-specific chitons.4. Results from sampling across a range of rhodolith morphs in the El Requeson bed (with lower average cryptofaunal densities of 2.3 organisms/ cm À3 ) revealed that the total organisms supported by a rhodolith significantly increased with both complexity (branching density) and space available (thallus volume). These data suggest that reducing the population size structure, structural complexity and cover of living rhodoliths could decrease species richness and abundance.5. While disturbance is a natural feature of these free-living beds, increased anthropogenic disturbance from trawling, anchoring and changes in water quality can directly impact the bed community through substrate alteration. Commercial fishing threatens rhodolith beds in the Gulf of California by decreasing rhodolith size and increasing sedimentation and burial rates. In addition to

Seagrasses, although well adapted for submerged existence, are C0,-limited and photosynthetically inefficient in seawater. This leads to high light requirements for growth and survival and makes seagrasses vulnerable to light limitation. We explored the long-term impact of increased CO, availability on light requirements, productivity, and C allocation in eelgrass (Zostera marina 1.1. Enrichment of seawater CO, increased photosynthesis 3-fold, but had no longterm impact on respiration. By tripling the rate of light-saturated photosynthesis, CO, enrichment reduced the daily period of irradiance-saturated photosynthesis (Hsat) that is required for the maintenance of positive whole-plant C balance from 7 to 2.7 h,

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Efecto de la temperatura sobre las tasas de fotosíntesis, crecimiento y calcificación del alga coralina de vida libre Lithophyllum margaritae

La composición y abundancia de algas marinas, invertebrados epibénticos y peces se estimó en marzo y octubre de 2003, mientras que los invertebrados endobiontes de los rodolitos (criptofauna) fueron cuantificados en marzo de 2003. De todos los organismos, los rodolitos y S. horridum tuvieron las mayores coberturas en los 0.5 km 2 de fondos de cantos rodados y arena estudiados, de 2 a 8 m de profundidad. Se muestreó un total de 29 especies de algas, 40 taxones de invertebrados bénticos y 33 especies de peces. Como resultado de la pérdida y el reemplazo de taxones, las diversidades de microalgas y peces fueron similares en ambos muestreos, mientras que la de invertebrados disminuyó sin ocurrir reemplazo de marzo a octubre. La cobertura de rodolitos fue similar en ambos muestreos. La cobertura y densidad de S. horridum fue altamente estacional, y la flora no rodolítica varió de abundancia de S. horridum (35% de cobertura) en marzo a abundantes tapetes de algas rojas en octubre (22% de cobertura). Los invertebrados epibénticos más abundantes en marzo fueron el erizo Arbacia incisa, los tunicados y los poliquetos; sin embargo, para octubre, el primero ya no estaba presente. Haemulon maculicauda y Calamus brachysomus fueron los peces más abundantes en ambos muestreos, pero se observaron grandes variaciones temporales especialmente en especies de peces que forman cardúmenes. La densidad de rodolitos en marzo fue de 24 ind m-2 , con numerosos individuos >8 cm de diámetro. Quince rodolitos de varias clases de talla contuvieron 114 taxones criptofaunales, con un promedio de 40 taxones/individuo para los rodolitos más grandes. Estos resultados muestran la importancia de los hábitats de rodolitos para la diversidad, las grandes variaciones temporales en algunas comunidades y la excepcional diversidad de esta comunidad subtropical.

Diel variations in rates of C export, sucrose-phosphate synthase (SPS) and sucrose synthase (SS) activity, and C reserves were investigated in Zosfera marina L. (eelgrass) to elucidate the environmental regulation of sucrose formation and partitioning in this ecologically important species. Rates of C flux and SPS activity increased with leaf age, consistent with the ontogenic transition from sink to source status. Rates of C export and photosynthesis were low but quantitatively consistent with those of many terrestrial plant species. The V,,, activity of SPS approached that of maize, but substrate-limited rates were 20 to 25% of V,,,, indicating a large pool of inactive SPS. SPS was unresponsive to the day/night transition or to a 3-fold increase in photosynthesis generated by high [CO,] and showed little sensitivity to inorganic phosphate. Consequently, regulation of eelgrass SPS appeared similar to starch-rather than to sugar-accumulating species even though eelgrass accumulates sucrose. Leaf [sucrose] was constant and high throughout the diel cycle, which may contribute to the down-regulation of SPS. Root sucrose synthase activity was high but showed no response to nocturnal anoxia. Root [sucrose] also showed no diel cycle. l h e temporal stability of [sucrose] confers an ability for eelgrass to buffer the effects of prolonged light limitation that may be key to its survival and ecological success in environments subject to periods of extreme light limitation and chaotic daily variation in light availability.

) on fragmented rhodoliths. The strong cueing to live coralline surfaces may have resulted from live coralline algal surfaces or surface biofilms. Growth, presented as post-settlement size, was significantly greater in scallops that settled onto whole vs. fragmented rhodolith substrates for both live (246.6 ± 1.9 vs. 238.9 ± 4.4 µm) and dead (244.2 ± 2.8 vs. 234.7 ± 5.6 µm) coralline surfaces. The structural and coralline cues provided by live, intact rhodoliths and their large-grained sediments contribute to the importance of rhodolith beds as nursery habitats by increasing both scallop settlement and postsettlement growth. Protection of living rhodolith habitats can enhance scallop and other invertebrate populations as well as the sustainability of scallop fisheries by enhancing early life stages.KEY WORDS: Argopecten ventricosus · Coralline · Rhodolith · Scallop · Larval settlement cues · Lithophyllum margaritae · Maerl · Bahía Concepción Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 396: [49][50][51][52][53][54][55][56][57][58][59][60] 2009 nell 1985, Raimondi 1990), and thereby strongly influence population and community-level processes (Rodriguez et al. 1993, Connolly & Roughgarden 1999. While hydrodynamic processes are known to strongly influence the delivery of larvae to suitable substrates (Butman et al. 1988, Abelson & Denny 1997, behavior in response to cues is also important in determining settlement patterns (Crisp 1974, Hadfield 1986, Raimondi & Morse 2000.Settlement cues, often required for metamorphosis of marine invertebrate larvae (Morse & Morse 1984, Pearce & Scheibling 1990, are thought to be indicative of environmental features that enhance survivorship (e.g. habitat, refuge, food or conspecifics). Physical cues include hydrodynamics (Crisp 1955), light (Crisp & Ritz 1973), depth (Knight-Jones & Morgan 1966), surface structural complexity (Harvey et al. 1993, disturbance events (Woodin et al. 1995) and surface chemistry (Hay 1996, Steinberg & de Nys 2002. Biological cues include presence of conspecifics (Keough 1998) and bacterial or bioorganic films (Maki et al. 1989, Keough & Raimondi 1995, Huggett et al. 2006). In addition, physical and biological cues can act synergistically (Crisp & Meadows 1963, Gee 1965, Le Tourneux & Bourget 1988. Few studies have been conducted in the field to understand in situ larval responses (Keough & Raimondi 1995) and how the distribution or magnitude of various cues might influence larval settlement (Underwood & Keough 2000).Complex seaweed surfaces, such as those found in coralline algae, provide combinations of physical and biological cues that can influence settlement in a range of invertebrates (Walters et al. 1996, Steinberg & de Nys 2002. Species of geniculate and non-geniculate (crustose) forms of coralline red algae occur in most coastal environments (Bosence 1983). A variety of invertebrate larvae are induced to settle on coralline algae by the physical features of the complex surfaces found on att...