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George Roff Colette C. C. Wabnitz Alastair R. Harborne Peter J. Mumby 《Marine Ecology》2013,34(4):409-419
Small grazing motile epifaunal invertebrates play an important ecosystem role on coral reefs, influencing both the abundance and composition of macroalgal communities and acting as a key food source for a range of predatory fishes. The first aim of this study was to investigate the associations between motile epifaunal communities and four common macroalgal species (Lobophora variegata, Dictyota divaricata, Microdictyon marinum and Halimeda opuntia) on fore‐reef environments in the Exuma Cays (Bahamas, wider Caribbean). Secondly, we investigated the implications of the well documented rise of Caribbean macroalgal cover on invertebrate densities by surveying sites inside and outside the Exuma Cays Land and Sea Park (ECLSP), where increases in parrotfish grazing intensity inside the marine reserves have led to reductions in macroalgal cover. Therefore, surveys compared similar reefs with significantly different macrolagal cover. Comparisons between macroalgal species revealed a four to fivefold difference in motile epifaunal densities per unit volume of macroalgae. Post‐hoc tests revealed that this difference was significant only for Lobophora, with no difference observed among the other species. As macroalgae provide both a refuge from predation and a food source for grazing epifauna, the higher densities of epifauna observed in Lobophora may be attributed to either refuge from visual predators through morphological features (high cover of overlapping blades close to the substrate) or lack of palatability for parrotfish grazing, providing a more stable refuge. Our results revealed no significant differences in diversity, density or community structure of motile epifauna per unit volume of macroalgae between sites inside and outside the ECLSP. Since canopy height and invertivore biomass did not vary systematically across reserve boundaries, this suggests that algal cover does not affect the density of epifaunal invertebrates. However, areal cover was consistently higher for all macroalgal species at sites outside the ECLSP than those inside the reserve. Therefore, when scaled by aerial cover of macroalgae, total abundance of epifauna was twofold higher outside the ECLSP. We suggest that the increasing abundance of macroalgae on Caribbean reefs may be having dramatic effects on epifaunal invertebrate populations and potentially their ecological functions. 相似文献
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Christine T. Y. Chung Scott B. Power Julie M. Arblaster Harun A. Rashid Gregory L. Roff 《Climate Dynamics》2014,42(7-8):1837-1856
Precipitation changes over the Indo-Pacific during El Niño events are studied using an Atmospheric General Circulation Model forced with sea-surface temperature (SST) anomalies and changes in atmospheric CO2 concentrations. Linear increases in the amplitude of the El Niño SST anomaly pattern trigger nonlinear changes in precipitation amounts, resulting in shifts in the location and orientation of the Intertropical Convergence Zone (ITCZ) and the South Pacific Convergence Zone (SPCZ). In particular, the maximum precipitation anomaly along the ITCZ and SPCZ shifts eastwards, the ITCZ shifts south towards the equator, and the SPCZ becomes more zonal. Precipitation in the equatorial Pacific also increases nonlinearly. The effect of increasing CO2 levels and warming SSTs is also investigated. Global warming generally enhances the tropical Pacific precipitation response to El Niño. The precipitation response to El Niño is found to be dominated by changes in the atmospheric mean circulation dynamics, whereas the response to global warming is a balance between dynamic and thermodynamic changes. While the dependence of projected climate change impacts on seasonal variability is well-established, this study reveals that the impact of global warming on Pacific precipitation also depends strongly on the magnitude of the El Niño event. The magnitude and structure of the precipitation changes are also sensitive to the spatial structure of the global warming SST pattern. 相似文献
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Jefferson T. Turner Russell R. Hopcroft Jean A. Lincoln Cameran Sassman Huestis Patricia A. Tester John c. Roff 《Marine Ecology》1998,19(3):195-208
Abstract. Grazing by the copepods Temora turbinata and Acartia lilljeborgii and the marine cladoceran Penilia avirostris on natural phytoplankton and cyanobacteria assemblages from Kingston Harbour. Jamaica, was examined in summer 1992. Food assemblages were often dominated by an unidentified filamentous cyanobacterium. with abundances of up to 1.16 × 104 filaments. ml-1. Other abundant phytoplankters included microflagellates and diatoms of the genus Niteschia. Mean clearance rates for the entire food assemblage ranged from 0.10 to 2.41 ml animal-1. h-1, although most mean clearance rates were between 0.5 and 1.5 ml. animal-1 h-1. Patterns of selection of different food items by various grazers on different dates were variable and inconsistent. Microscopic measurements revealed that cyanobacterial filament lengths were shorter in grazed than initial aliquots during a cyanobacterium bloom in August. This suggests that grazers reduced lengths of many filaments by biting off portions, in addition to consuming entire filaments. Such ‘filament clipping’ of cyanobacteria filaments has been recorded previously in freshwater studies and suggests that grazers impact a larger portion of the phytoplankton assemblage than is accounted for by ingestion and clearance rates based only upon removal of filaments. Grazers exhibited no adverse effects from consuming cyanobacteria. Cyanobacterkd are often considered to be toxic or of poor food quality for planktonic grazers. but due to the high abundance and dominance of filamentous cyanobacteria in Kingston Harbour. if these cyanobacteria were ungrazed. there would at times be little alternative phytoplankton food for copepods and cladocerans. Our results suggest that the trophic role of tilamentous cyanobacteria in pelagic food webs of the tropical ocean should be further investigated and possibly reconsidered. 相似文献
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On August 31th, 2006 the California Senate shelved SB1056, a bill which would have granted the State jurisdiction over the regulation of seed and nursery stock. Ostensibly proposed to ensure “a level playing field” for agricultural and food producers, SB1056 is one of a host of legislation drafted across the United States to preempt county and municipal bans on genetically engineered crops. In California, the heated struggle around “preemption” exemplifies the interweaving of neoliberal ideology with industry attempts to prevent an unfavorable regulatory environment, but more importantly the contingencies and vulnerabilities of this strategy. After reviewing SB1056’s history, this paper examines how a diverse opposition movement capitalized on the friction between the neoliberal arguments mobilized by supporters and dominant Californian political philosophies. The paper then highlights the ultimate effect of SB1056 through a critical exploration of current state and federal regulation and the entrenched interests of the California government. I argue that more than simply opening new spaces for accumulation, SB1056 would have muted opposition voices and transferred power to institutions financially committed to the technology’s commercialization. 相似文献
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50年前的5月,智利的一场特大地震开创了地震科学研究的新境界。RoffSmith回顾了那场世界上有仪器记录的最大地震。 相似文献
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