Species-specific ability ofChlorella strains (Chlorophyceae) to form stable symbioses withHydra viridis

46 strains ofChlorella, identified by physiological and biochemical characters, were examined for their ability to form stable symbioses with aposymbioticHydra viridis. It was found to be a species-specific characteristic. Among the 15 taxa studied, onlyC. saccharophila var.ellipsoidea, C. saccharophila var.saccharophila, C. fusca var.vacuolata, C. kessleri, C. luteoviridis, andC. protothecoides formed stable symbioses withHydra viridis. Among the 11 known physiological and biochemical characters of theseChlorella species, only acid tolerance seems to be correlated with symbiosis: All symbiotic species are capable of growing at or below pH 4.0.     

Algal polysaccharides: potential bioactive substances for cosmeceutical applications

The cosmetics industry is one of the most profitable in the world today. This multi-billion-dollar industry has a profound sociological impact worldwide. Its influence is global, with most individuals being concerned with conserving their physical appearance, beauty, and youth. The consumers’ desire for novel, better, and safer products has stimulated the utilization of natural-product-based cosmeceutical formulations over synthetic chemicals. With remarkable advancements in marine bioresource technology, algal polysaccharides have gained much attention as bioactive ingredients in cosmeceuticals. Algae biosynthesize a variety of polysaccharides including fucoidans, alginates, carrageenans, galactans, agar, porphyran, glucans, and ulvans, all of which exhibit distinctive structural and functional properties. Many of these materials have been proven to possess skin-protective effects, including anti-wrinkle, lightening, moisturizing, UV protective, antioxidative, and anti-inflammatory activity. Moreover, they have a wide spectrum of physicochemical properties, such as the ability to form hydrogels, which extend their utilization as emulsifiers, stabilizers, and viscosity controlling ingredients in cosmeceuticals. Accordingly, algal hydrocolloids and their synthetic derivatives can also be applied in tissue engineering and cosmetic surgery. The challenge is to increase awareness about these polysaccharides and consequently generate value-added products. This review discusses the beneficial biological and physicochemical properties of algal polysaccharides, highlighting their potential in cosmeceutical applications.     

Image analysis - a simple method of algal culture growth assessment

A non-destructive method for the relative growth quantification of algae or cyanobacteria in the culture has been developed. It is based on image analysis and does not require any special equipment. Results provided by this method were compared with those provided by a chlorophyll a assessment, with a correlation factor of over 88%.     

Reef corals, zooxanthellae and free-living algae: a microcosm study that demonstrates synergy between calcification and primary production

A mature, high-biodiversity coral reef microcosm and its chambered subsets were used to examine the relationship between calcification and photosynthesis and its most critical biotic components. Whole ecosystem calcification at 4.0±0.2 kg (40±2 mol) CaCO₃ m⁻² year⁻¹ is related to its primary components (stony coral 17.6%, Halimeda 7.4%, Tridacna 9.0%, algal turf, coralline and foraminifera 29.4%, and miscellaneous invertebrates 36%). Through analysis of the microcosm's daily carbonate system, it is demonstrated that bicarbonate ion, not carbonate ion, is the principal component of total alkalinity reduction in the water column (thus, bicarbonate ion is the principal measured component of calcification as normally measured on reef transects). While chamber-isolated free-living algae remove carbon dioxide, and raise pH and carbonate ion equivalent to that in the microcosm as a whole, no total alkalinity reduction (calcification) occurs. On the other hand, chamber isolated stony corals remove considerable bicarbonate, with very little pH or carbonate ion elevation. Combining the non-calcifying free-living macroalgae Chondria with stony corals in chamber subsets, it is possible to remove more carbon dioxide (elevating pH) and thereby increase coral calcification rates by 60 and 120% above zooxanthellae-mediated rates to 20.6 kg (206 mol) and 18.5 kg (185 mol) CaCO₃ m⁻² year⁻¹ for Acropora and Montipora, respectively. These findings, which support the McConnaughey and Whelan hypothesis of bicarbonate ion neutralization in coral calcification, are easily demonstrated in the controlled microcosm environment.     

Benthic macroalgae as a dispersal mechanism for fauna: influence of a marine tumbleweed

Effective dispersal is problematic for benthic organisms without planktonic larvae; rafting and vertical migrations are mechanisms that can potentially be employed by such fauna, but these strategies entail considerable predation risk as well as other disadvantages. Unattached, but non-floating, “drift” algae harbor large numbers of fauna and may serve as an alternative dispersal mechanism in some systems. This paper reports field manipulations in Florida Bay, Florida, USA designed to determine (1) if such algae can disperse benthic animals, and (2) if dispersal efficiency varies as a function of two common substrata types: seagrass and bare sediment. A live immersion stain was used to mark faunal associates of Laurencia spp. algal clumps in situ. The fidelity of molluscs, decapods, ophiuroids, and fishes to stationary algal clumps was then compared with the fidelity of these animals to clumps that were forced to tumble over a given distance with a blower apparatus; these experiments were performed over both sand and seagrass substrata. Measurements of frequency, spatial extent, and rate of algal drift were made to aid in assessing the potential importance of benthic algae as a dispersal mechanism.

Algal clumps often rolled in a manner similar to that of terrestrial tumbleweeds; mark-recapture work showed that algal clumps can move up to 0.5 km/day and that algal drift is a frequent phenomenon. The algal masses were effective transporters of benthic fauna, including mobile shrimps and fishes; dispersal was more efficient over sand than over seagrass. Dispersal of fauna via this mobile habitat should entail lower risk than other adult dispersal stratagems such as vertical migration or rafting; this mechanism would be most advantageous for brooding species or those with limited planktonic phases. Differential fidelity to clumps tumbling across seagrass versus sand suggests that the algae could facilitate exchange of fauna between isolated seagrass patches.     

Comparison of methods to assess water column primary production in wetlands

We compared a number of techniques to measure water column autotroph production in a shallow, hypereutrophic wetland: diurnal oxygen changes; light and dark bottle incubations; chlorophyll a concentrations; daily changes in pH; and algal volume. Productivity from diurnal oxygen changes calculated at 0.25, 0.5, 1, 2, 3, and 4 h intervals give similar estimates, but not 12 h intervals (dawn-dusk-dawn). Net productivity in bottles was slightly lower than that indicated by diurnal oxygen changes, and gross productivity in bottles was much lower than diurnal changes. Changes in pH correlated well with gross and net productivity measurements, as well as algal volume. Chlorophyll a is correlated with diurnal and bottle net productivity measurements and pH changes, but not algal volume. Since daily pH flux and oxygen changes provide a better overall assessment of ecosystem processes than standing crop or bottle incubations, they could be useful measurements for ecological engineers interested in assessing the ecosystem function.