Species-specific effects of herbivorous fishes on the establishment of the macroalga Lobophora on coral reefs

Herbivory is a key ecosystem function that influences ecosystem trajectories. However, interactions between plants and herbivores are species-specific and change throughout the plants' lifetime. On coral reefs, herbivorous fishes reduce competition between corals and macroalgae through their grazing activity, thereby regulating the ecosystem state. Grazing vulnerability of marine algae generally decreases with increasing algal size. Therefore, the removal of newly settled recruits by herbivorous fish is likely important in preventing macroalgal blooms and reducing competition with corals. We studied the grazing susceptibility of recruits of the brown macroalga Lobophora to multiple fish species through a combination of feeding observations and manipulative in situ and ex situ experiments. Further, we recorded short-term Lobophora growth patterns and adult survival over 9 wk. Lobophora recruits were more susceptible to herbivory than adults, likely owing to their smaller size. However, recruit mortality was driven by only 3 of the studied species: Acanthurus nigrofuscus, Scarus niger and Chlorurus spilurus, whereas other common herbivores did not remove any Lobophora recruits. Our data also suggest variable growth and recruitment among months. These findings point to a possible increase in grazing resistance with age for Lobophora. As such, a decrease in grazing pressure by key fish species controlling Lobophora recruits could permit Lobophora to establish more grazingtolerant adult populations

Moment Closure - A Brief Review

Moment closure methods appear in myriad scientific disciplines in the modelling of complex systems. The goal is to achieve a closed form of a large, usually even infinite, set of coupled differential (or difference) equations. Each equation describes the evolution of one "moment", a suitable coarse-grained quantity computable from the full state space. If the system is too large for analytical and/or numerical methods, then one aims to reduce it by finding a moment closure relation expressing "higher-order moments" in terms of "lower-order moments". In this brief review, we focus on highlighting how moment closure methods occur in different contexts. We also conjecture via a geometric explanation why it has been difficult to rigorously justify many moment closure approximations although they work very well in practice.Comment: short survey paper (max 20 pages) for a broad audience in mathematics, physics, chemistry and quantitative biolog

Development and characterisation of a large diameter decellularised vascular allograft

The aims of this study were to develop a biological large diameter vascular graft by decellularisation of native human aorta to remove the immunogenic cells whilst retaining the essential biomechanical, and biochemical properties for the ultimate benefit of patients with infected synthetic grafts. Donor aortas (n = 6) were subjected to an adaptation of a propriety decellularisation process to remove the cells and acellularity assessed by histological analysis and extraction and quantification of total DNA. The biocompatibility of the acellular aortas was determined using standard contact cytotoxicity tests. Collagen and denatured collagen content of aortas was determined and immunohistochemistry was used to determine the presence of specific extracellular matrix proteins. Donor aortas (n = 6) were divided into two, with one half subject to decellularisation and the other half retained as native tissue. The native and decellularised aorta sections were then subject to uniaxial tensile testing to failure [axial and circumferential directions] and suture retention testing. The data was compared using a paired t-test. Histological evaluation showed an absence of cells in the treated aortas and retention of histoarchitecture including elastin content. The decellularised aortas had less than 15 ng mg¯¹ total DNA per dry weight (mean 94% reduction) and were biocompatible as determined by in vitro contact cytotoxicity tests. There were no gross changes in the histoarchitecture [elastin and collagen matrix] of the acellular aortas compared to native controls. The decellularisation process also reduced calcium deposits within the tissue. The uniaxial tensile and suture retention testing revealed no significant differences in the material properties (p > 0.05) of decellularised aorta. The decellularisation procedure resulted in minimal changes to the biological and biomechanical properties of the donor aortas. Acellular donor aorta has excellent potential for use as a large diameter vascular graft