Seaweeds of potential economic importance in Kenya: field survey and future prospects

Kenya is a net importer of agar and alginate based on recent government statistics, although it may have the potential to be self-sufficient or even an exporter of these phycocolloids. There is little information on carrageenan importation into Kenya since government statistics incorporate it as agar. Seaweeds are relatively unimportant in the Kenyan diet since they are consumed rarely by coastal people. A survey of 15 sites along of the Kenyan coast evaluated the potential for harvesting seaweeds and for establishing seaweed farms. Gracilaria appears to comprise the bulk of the low grade agar import, even though local species of this genus are widely distributed along the Kenyan coast. Major populations of Gelidium may be a potential source of high quality bacteriological grade agar. Eucheuma may be farmed locally to support the increasing local and regional demands for carrageenan. Recommendations for a national program of management and production for Kenya will be discussed.     

Chemical screening of Brazilian marine algae producing carrageenans

The yield, IR spectra, 3,6-anhydro-d-galactose and sulfate content are given for several species of putative carrageenophytes from different sites on the Brazilian coast. Kappa carrageenan was found in Hypnea musciformis and Gigartina spp. ; all the other species tested yield an iota type. The lowest carrageenan yield was found in Cryptonemia crenulata (5%), and the highest in Gigartina sp. (72%); 3,6-anhydrogalactose content was highest in Hypnea musciformis and Gigartina spp., whereas sulfate was lowest in H. musciformis. Slight variations in the yield of carrageenans were found during the period of observation (March 1988 to May 1989), but no clear pattern could be recognized. No significant variation was observed in plants from different collection sites.     

The influence of environmental features in the content of mycosporine‐like amino acids in red marine algae along the Brazilian coast

Mycosporine‐like amino acids (MAA) are ultraviolet screen substances synthesized by marine algae. The physiological function of these substances is related to cellular protection against UV radiation and as a protective mechanism against oxidative stress. These substances can be found mainly in the ocean, among red seaweeds. Its concentration in organisms has been related to ultraviolet radiation and availability of inorganic nitrogen in the environment. We start our study of MAA content in different species to understand if environmental conditions influence the concentration of MAAs in red seaweeds. The Brazilian coast presents abiotic factors that interact to create different physical‐chemical features in the environment. We collected 441 samples from 39 species of red seaweed easily found in the intertidal zone, in low tide, during the summer of 2015. The sampling encompassed a latitudinal gradient (3° S to 28°5′ S) at 23 points along the coast. We quantified and identified the content of MAAs in species through the method of high performance liquid chromatography. We detected for the first time the occurrence of MAAs in certain species of red algae that have not been reported to contain MAAs before. We confirmed that some environmental factors influenced the content of MAAs. Enhanced MAA contents, for example, were found in environments with a basic pH, a high ultraviolet index, and high concentrations of phosphate and nitrate. Salinity, dissolved oxygen and variations of sea surface temperature also influenced, in a secondary way, MAA content in algae in their natural environments.     

Ethnobotany of seaweeds: clues to uses of seaweeds

Extensive uses of fresh and dried seaweeds by coastal populations over the world can furnish clues to potential food and other uses of seaweeds, just as the first extraction of a seaweed gelatin now used for bacteriological purposes was discovered by a housewife in search of a pudding. Ethnic uses as food depend heavily on closely related species suitable for making cool, gelatinous dishes or concoctions, or on species suitable for adding to soups or stews. Rarely, single species like cochajugo (Durvillea antarctica) in Chile and rimu (Durvillea antarctica) in New Zealand point to different kinds of food preparation. Oriental cuisine incorporates many different species of seaweeds in a wide variety of ways, whereas commercial western uses depend upon extracts of wall materials to suspend, emulsify or stabilize a broad variety of foods and products.     

Spatial variation in polyphenolic content of Ascophyllum nodosum (Fucales,Phaeophyta)

Spatial variation in polyphenolic content in annual shoots of the brown alga Ascophyllum nodosum was quantified using a hierarchical sampling design. Three sampling levels, covering distances of 10⁰–10⁶ m, were used. Comparisons were made between two areas, Tjärnö on the Swedish west-coast and the Isle of Man in the Irish Sea, with very different types of environmental conditions. No significant differences in mean polyphenolic levels were found between the two study areas (6.6% of dry mass at Tjärnö and 9.2% at the Isle of Man), whereas significant and substantial differences were found among sites within areas (range 5.7%–11.4%) and among quadrats within sites (range 3.7%–13.1 %). The extensive variation at the smaller spatial scales points out the importance of using thorough sampling procedures at all levels in large-scale studies on algal polyphenolics, e.g. biogeographical comparisons, which have been neglected in several previous studies. Moreover, the results imply that experiments on causal factors of polyphenolic variation should be designed to explain the spatial scales on which the factors are impportant. This study also investigated the relationship between polyphenolic concentration and both plant size and mean area of annual shoots. The mean area was used as an estimate of the mean growth rate of the annual shoots within an individual. No significant relationships were found between shoot growth rate, or plant size, and polyphenolic levels in annual shoots at any of the three spatial scales that were investigated.     

Sorbitol and sorbitol phosphate in brown seaweeds

Small amounts of D-sorbitol were extracted from 15 species of brown seaweeds representing four orders, independent of seasonal effects. Sorbitol phosphate was also isolated and identified.     

Photosynthetic light-response curves and photoinhibition of the deep-water laminaria abyssalis and the intertidal laminaria digitata (phaeophyceae)

Photosynthetic light‐response curves of the deep‐water Laminaria abyssalis Oliveira and of the intertidal L. digitata Lamoroux were determined and related to photoinhibition phenomena as monitored by oxygen evolution and photosystem II efficiency (F_V/F_M). L. abyssalis has half the pigment content, number of cells and plastids, and photosynthetic capacity per unit area compared with L. digitata. L. abyssalis showed a higher in vivo Chl a absorption coefficient and higher photosynthetic efficiency on a Chl a basis, although the two algae showed somewhat similar light‐response curves on a Chl a basis. Both species showed similar Chl a/Chl c and Chl a/fucoxanthin ratios, and similar dark respiration rates and light compensation points. In addition, they also showed similar convexities in their light‐response curves and no differences in their light saturation of F_V/F_M. Room temperature chlorophyll fluorescence induction measurements of fronds incubated in 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) suggest that both species may have a similar PSII absorption cross section. Thus, L. abyssalis appears to optimize its light absorption at very low light intensities, not by increasing the pigment content, but by absorbing light more efficiently. However, L. abyssalis was more sensitive to photoinhibition than L. digitata and showed no recovery of F_V/F_M and O₂ evolution after a photoinhibitory treatment, even with a subsequent exposure to 24 h of dim light. L. digitata, on the other hand, recovered its photosynthetic capacity within 6 h under dim light. These results suggest that photosynthetic light‐induction curves based on Chl a are not a good indicator of either the photosynthetic capacity or the sensitivity to photoinhibition when macroalgae of different species are being compared. Based on their light‐response and photoinhibition characteristics, we suggest that L. abyssalis, a deep‐water oceanic macroalgae, is an atypical shade alga whereas L. digitata has the properties of a sun alga.     

刺槐根瘤菌与纤维素分解菌对上海青和高粱的促生效应

通过盆栽试验,用刺槐根瘤菌(Rhizobium of Robinia pseudoacacia)与纤维素分解菌(Cellulose-decomposing Bacteria)对高粱和上海青进行单独接种和混合接种,采用针刺、浸种和涂叶3种接种方法,测量其各种生长指标。初步探究刺槐根瘤菌与纤维素分解菌联合对禾本科作物高粱和双子叶作物上海青两种非豆科植物的促生效应。结果表明,在非针刺条件下,两种菌混接组(B组)比单独接种根瘤菌组(D组)的促生效应更显著,上海青B组在灭菌条件下的根长促生率比D组高出48.97%,高粱B组在非灭菌条件下干重的促生率比D组高出30.76%;而且除了高粱的B组干重以外,盆栽试验条件下,B、D两组的其他生长指标在灭菌情况下的促生率比非灭菌条件下的促生率高,差别最大的为上海青B组鲜重,灭菌条件下比非灭菌条件下高出47.13%。根瘤菌与纤维素分解菌混合接种非针刺组,对高粱和上海青的各项生长指标促生效应明显,可为今后进一步开发非豆科作物菌肥提供试验依据。     

Comparison of the impacts of consumers, ambient UV, and future UVB irradiance on mid-latitudinal macroepibenthic assemblages

Future levels in ultraviolet-B (UVB) radiation are expected to increase directly due to stratospheric ozone depletion and under water indirectly by, for example, global warming effects on DOC concentrations, altered trophic interactions in the plankton, or reduced eutrophication. While detrimental UV effects have been reported at the cellular level, little to nothing is known about community-wide effects of ambient and future UVB radiation. In a 4-month field experiment, the ambient UV regime was (i) reduced by cut-off filters which removed either UVB or total UV from the solar spectrum or (ii) increased to predicted future levels by UVB lamps. To allow relating the effects of present and future UV regimes to another important ecological control of community structure and diversity in subtidal marine habitats, consumer effects were quantified by an exclusion treatment under ambient light regimes. Ambient UV regimes did not affect community structure, biomass accrual, and diversity. In contrast, under enhanced UVB levels, the dominance of the competitively superior blue mussels increased and species richness and biomass accrual decreased. Species composition of the assemblages differed between the two UV regimes. Effects of enhanced UVB radiation and of consumption on biomass accrual, diversity, and structure of the community were comparable in magnitude and timing, but of opposite direction. In contrast, the effects of enhanced UVB radiation on growth and abundance of mussels were in the same direction, but shorter and weaker than consumer effects. Most UV effects were transitory and vanished within the first 2 months of succession. Our results indicate that present and future UVB levels may be of limited importance and not stronger in effect size than other ecological controls in structuring the shallow-water low-diversity macrobenthic communities in temperate regions.     

Gradient in seaweed vegetation patterns along the North Icelandic coast,related to hydrographic conditions

The benthic algal vegetation of the North Icelandic coast exhibits particular features, different from those found in southern and western Iceland on the one hand and in eastern Iceland on the other. It is characterised by low-eulittoral belts of Devaleraea ramentacea, Petalonia species and Chordaria flagelliformis as well as by meadows of diverse Acrosiphonia species. In the tide pools Atlantic and typical North Icelandic associations occur side by side. This area thus represents an intermediate region between Atlantic and subarctic growth conditions. A certain gradient in the west-east direction was observed within the North Icelandic vegetation type and is possibly related to the gradual cooling and dilution of the water masses which pass the North Icelandic shelf. The hydrographic discontinuity in the extreme NW creates a sharp floristic and vegetational boundary for benthic algae, whereas in the NE a gradual transition towards the subarctic East Icelandic vegetation was observed. The Atlantic character of the vegetation was more pronounced in the western than in the eastern part of the north coast. An enclave of warm water vegetation was interposed along the western banks of the Tjörnes peninsula.This paper is based on a presentation at the XIII^th International Seaweed Symposium in Vancouver, Canada.