Influence Of Structural Complexity Research Articles

Refuge-dependent herbivory controls a key macroalga on coral reefs

Small-scale structural complexity shapes how consumers and primary producers interact, which can influence ecosystem trajectories. Coral reefs are some of the most structurally complex ecosystems, though their complexity is threatened owing to anthropogenic influences. Some reefs shift towards macroalgal dominance following mass coral mortality, which can hinder the recovery of corals because they compete with the faster growing macroalgae for space. Using video observations, surveys and in situ experiments on a forereef in eastern Palau, we investigated the role different microhabitats play in facilitating the persistence of the macroalga Lobophora, which is one of the strongest negative interactors with corals. Collectively, our observational and experimental data show that small crevices provide a refuge to Lobophora recruits by excluding most adult herbivorous fishes. Consequently, Lobophora is disproportionately more abundant within these concealed microhabitats on the reef, which highlights the important role of microhabitats as macroalgal nurseries from which macroalgae can spread following mass coral mortality. While a large proportion of our current understanding of grazer–algae interactions is based on research using flat surfaces, our findings demonstrate that the interactions between herbivorous fishes and benthic organisms are strongly mediated by microhabitats. It is thus important to consider the influence of structural complexity in order to understand the nuances that govern benthic regimes.

A New Method for Predicting the Hydrocyclone Efficiency with the Light Dispersed Phase

In this study, a new method for predicting the hydrocyclone efficiency with the light dispersed phase has been developed. The equivalent volume method is employed to simplify the effective region of the hydrocyclone into a cylindrical shape, the influence of structural complexity on the method is reduced. Based on the analysis of the dispersed phase droplets and the assumption of determining the droplets been separated, a residence time model of the droplets in the effective separating region is theoretically developed. This method can be expressed as a simple function including the cyclone dimension and operating parameters. By compared with the previous experimental data, it is showed that the calculated value is close to the experimental value when the separation rate is more than 10%. When inlet velocity is not too large, cause the dispersed phase droplet breakage is not obvious, the applicability of this method is better.

Evolution and progressive geomorphic manifestation of surface faulting: A comparison of the Wairau and Awatere faults, South Island, New Zealand: COMMENT

Zinke et al. (2015) documented a flight of Saxton River terraces deformed by the Awatere fault, South Island, New Zealand. They concluded that the manifestation of off-fault deformation (OFD) is a cumulative effect, and therefore may not be immediately apparent on younger terraces, with implications for slip rate determinations. I argue that they did not adequately consider the detailed structural setting of elements of OFD within the Saxton River releasing bend on the Awatere fault. The surface deformation at Saxton River is probably controlled by the coincidence of terraces with structural zones within the bend, and I contest the authors’ conclusion that off-plane deformation is simply hidden in younger terraces. The influence of structural complexity on the width and geometry of OFD is well established (e.g., Milliner et al., 2015). Zinke et al.’s figure DR2 (in GSA Data Repository 2015341) shows that OFD along the Awetere fault occurs at bends or steps in the fault plane, including at Saxton River where the fault bends right relative to the main trace by 5–10°, ~50 m east of the T2-T3 riser. This gives rise to a graben (T1 tread) and two pressure ridges (T2 tread and bedrock spur) that define and bound an overall 150-m-wide releasing bend (Mason et al., 2006) (Figs. 1A and 1B). The paired pressure-ridge and graben geometry is predicted when the wall rocks on either side of a strike-slip fault approach and interact with a fault bend during an earthquake (Sibson, 1989), and has been reported on the Hope (Cowan, 1990) and Greendale (Duffy et al., 2013) faults in New Zealand, and the San Andreas fault in California (Ben-Zion et al., 2012), among others.

The influence of structural complexity and reef habitat types on flight initiation distance and escape behaviors in labrid fishes

Structural complexity is a key parameter for fish on reef habitats. Several studies have investigated the influence of this variable on aspects of reef fish population and community dynamics. However, there is a lack of knowledge on the influence of structural complexity on antipredator behavior. Here we studied the effect of habitat type and structural complexity on flight initiation distance (FID) and the escape behaviors of four labrid fishes (Halichoeres brasiliensis, H. penrosei, H. poeyi and Sparisoma axillare) on two different reef habitats (coral and rocky reefs). Habitat type influenced the FID of three of the studied species (H. brasiliensis, H. penrosei and S. axillare), and structural complexity negatively influenced the FID of two species (H. brasiliensis and S. axillare). The frequency of escape behaviors varied between species. All of them showed high frequency of the ‘run away’ behavior and low frequency of the ‘leave the habitat’ behavior. On coral reefs, structural complexity influenced the ‘fled to the holes’ for S. axillare only. Reef ecosystems worldwide are being modified by anthropogenic activities. Our results suggest that if such activities reduce structural complexity, then ‘seascapes of fear’ for labrid fishes will become more widespread, which could lead to negative consequences in the reef ecosystems.

Physical properties of the V-Al5Cu6Mg2 complex intermetallic phase

The cubic V-Al5Cu6Mg2 phase with 39 atoms in the unit cell is an intermetallic phase with intermediate structural complexity between the simple Laves phase and the complex Bergman phase. Using 27Al NMR spectroscopy, we have determined the electric-field-gradient tensors at the positions of three crystallographically nonequivalent Al sites in the unit cell and confirmed the local site symmetries of these sites, as predicted by the Samson structural model of the V-phase from 1949. The influence of structural complexity on the physical properties of a solid was studied by determining bulk electrical and thermal properties (electrical resistivity, thermoelectric power, Hall coefficient, thermal conductivity and specific heat) and local electronic properties of the V-Al5Cu6Mg2 monocrystal by studying the 27Al NMR Knight shift and the spin-lattice relaxation rate. The experiments reveal that free-electron picture is good approximation to the V-Al5Cu6Mg2 electronic structure, despite the structural complexity of the lattice. The positive thermopower and Hall coefficient reveal that V-Al5Cu6Mg2 is a hole-type electrical conductor. Electrical resistivity shows linear temperature dependence with a positive temperature coefficient, typical of regular metals and alloys. The relatively large T→0 residual resistivity and the low thermal conductivity suggest the presence of quenched structural disorder, very likely intrinsic to the V-Al5Cu6Mg2 structure. We did not find any experimental evidence of a pseudogap close to the Fermi energy in the electronic density of states that could contribute to the electronic stabilization of the structure.

Structural variation in the brown alga Sargassum cymosum and its effects on associated amphipod assemblages.

The presence of diverse biological substrates adds complexity to coastal landscapes and increases the number of ecological niches that can be used by the mobile epifauna. Studies on the influence of structural complexity have focused mainly on algal host species, but there is little information about the influence of intraspecific structural variation on the associated mobile epifauna. In this work, we examined whether intraspecific variation in the brown alga Sargassum cymosum influenced the structure of amphipod assemblages on two shores with different wave exposure. At least 15 fronds were randomly sampled at Fortaleza and Perequê-Mirim beaches, on the Atlantic coast of São Paulo state, southeastern Brazil, and 12 variables were measured for each alga. The amphipods were identified and counted. The greatest structural variation in S. cymosum occurred within shores, whereas the differences between shores were mainly related to algal size. These characteristics influenced amphipod assemblages differently on each shore, with the greatest effects being associated with variables related to morphological complexity, such as holdfast size, the number and size of branches, and the extent of cover by sessile colonial animals. These findings show that monospecific algal banks are not homogeneous, and that morphological differences and interactions with other biological substrates can influence the mobile epifaunal assemblages.

Habitat selection of two gobies ( Microgobius gulosus, Gobiosoma robustum): influence of structural complexity, competitive interactions, and presence of a predator

Herein I compare the relative importance of preference for structurally complex habitat against avoidance of competitors and predators in two benthic fishes common in the Gulf of Mexico. The code goby Gobiosoma robustum Ginsburg and clown goby Microgobius gulosus (Girard) are common, ecologically similar fishes found throughout the Gulf of Mexico and in the southeastern Atlantic Ocean. In Florida Bay, these fishes exhibit habitat partitioning: G. robustum is most abundant in seagrass-dominated areas while M. gulosus is most abundant in sparsely vegetated habitats. In a small-scale field survey, I documented the microhabitat use of these species where their distributions overlap. In a series of laboratory experiments, I presented each species with structured (artificial seagrass) versus nonstructured (bare sand) habitats and measured their frequency of choosing either habitat type. I then examined the use of structured versus nonstructured habitats when the two species were placed together in a mixed group. Finally, I placed a predator ( Opsanus beta) in the experimental aquaria to determine how its presence influenced habitat selection. In the field, G. robustum was more abundant in seagrass and M. gulosus was more abundant in bare mud. In the laboratory, both species selected grass over sand in allopatry. However, in sympatry, M. gulosus occupied sand more often when paired with G. robustum than when alone. G. robustum appears to directly influence the habitat choice of M. gulosus: It seems that M. gulosus is pushed out of the structured habitat that is the preferred habitat of G. robustum. Thus, competition appears to modify the habitat selection of these species when they occur in sympatry. Additionally, the presence of the toadfish was a sufficient stimulus to provoke both M. gulosus and G. robustum to increase their selection for sand (compared to single-species treatments). Distribution patterns of M. gulosus and G. robustum likely result from a synthesis of various biotic and abiotic filters, including physiological tolerances to environmental factors, dispersal ability of larvae, and availability of food. Selection for structural complexity, competition, and presence of predators may further define the resulting pattern of distribution observed in the field.

The Influence of Structural Complexity on Fish–zooplankton Interactions: A Study Using Artificial Submerged Macrophytes

Aquatic macrophytes produce considerable structural variation within the littoral zone and as a result the vegetation provides refuge to prey communities by hindering predator foraging activities. The behavior of planktivorous fish Pseudorasbora parva (Cyprinidae) and their zooplankton prey Daphnia pulex were quantified in a series of laboratory experiments with artificial vegetation at densities of 0, 350, 700, 1400, 2100 and 2800 stems m−2. Swimming speeds and foraging rates of the fish were recorded at different prey densities for all stem densities. The foraging efficiency of P. parva decreased significantly with increasing habitat complexity. This decline in feeding efficiency was related to two factors: submerged vegetation impeded swimming behavior and obstructed sight while foraging. This study separated the effects of swimming speed variation and of visual impairment, both due to stems, that led to reduced prey–predator encounters and examined how the reduction of the visual field volume may be predicted using a random encounter model.

Influence of plant structural complexity on the foraging success of Trichogramma minutum: a comparison of search on artificial and foliage models

AbstractThe influence of structural complexity on the foraging success for host eggs (Ephestia kuehniella Zeller) by Trichogramma minutum Riley was investigated in the laboratory. Naive females were released into arenas with structurally different paper models or foliage (simple: trembling aspen Populus tremuloides Michx., complex: balsam fir Abies balsamea L.). Observations of individual females were made every 15 min and searching success was measured by the number of host egg clusters found and the amount of time taken to find them, within a period of 196 min. Females found significantly more egg clusters and were quicker at finding them on the sample paper and foliage surfaces than on the most complex paper or foliage surfaces. Older females (2–3 days) were more successful and searched quicker than younger (<24 h) females on all paper surfaces. The timed observations suggested that wasps which spent more time walking had a significantly decreased probability of finding an egg mass and were significantly slower at finding them. Females that spent more time on paper surfaces had an increased probability of finding an egg mass. The significance of searching differences is discussed in relation to the potential effects of plant surfaces on Trichogramma movements and to the physiological readiness of the wasp.