The effect of fertilizer application on farming of the seaweed Undaria pinnatifida (Laminariales, Phaeophyta)

A slow-release ammonium phosphate fertilizer coated with porous plastic was tested on Undaria pinnatifida (Harvey) Suringar as a possible solution to the nutrient deficiency in seawater that causes quality and yield deterioration in seaweed farming. The yield of U. pinnatifida within the fertilized area was 17–40% greater than that of the control area (unfertilized area). In addition, two harvests were possible per season and the quality of harvested U. pinnatifida was also better than that outside the fertilizer diffusion area. The released NH₄-N did not increase the concentration of NH₄-N outside the farming area. Therefore, this fertilizer increased yield and improved quality without causing water pollution.     

A comparison of ecological responses among aclonal (unitary), clonal and coalescing macroalgae

Based on growth patterns, regeneration capabilities and genetic make up, benthic macroalgae include three groups of species. Similar to land plants, they include clonal and aclonal species, and, similar to colonial aquatic animals, seaweeds also include coalescing species, that have the capacity to fuse forming composite (chimeric) entities. Since the awareness of the differences between these three kinds of seaweeds is rather recent, most ecological studies have not discriminated among them. However, ecological models based on one kind of seaweeds will not necessarily apply to all kinds of seaweeds. This study reviews ecological responses of algae at the individual and community levels, and describes similarities and differences among both the three algal groups and with parallel groups in land plants and chimeric marine animals. The ecological responses reviewed are plant sizes and shapes; patterns of resource acquisition; algal life phases, reproduction and dispersal; genetic variability, intraspecific and interspecific competition and herbivory. Analysis of these responses supports the idea in distinguishing among the above three algal group, reveals the need for numerous additional ecological studies and advices on incorporating concepts from the biology of chimeric aquatic animals and from clonal theory of land plants into the study of benthic macroalgae.     

Ecological effects of seaweed harvesting in the Gulf of California and Pacific Ocean off Baja California and California

The ecological effects of harvesting were investigated for two species, the giant kelp Macrocystis pyrifera and Eucheuma uncinatum, by using harvest records and aerial surveys that show yield changes and by using studies of recruitment, survivorship and community interactions. There were no ecological effects found for M. pyrifera harvested with contemporary methods, and there are no recommendations for changing current management practices for this species. It is recommended that E. uncinatum, which on occasion produces commercially significant standing crops, not be harvested unless special precautions are taken to leave some plants for regeneration of the harvested populations.     

Medicinal and pharmaceutical uses of seaweed natural products: A review

In the last three decades the discovery of metabolites with biological activities from macroalgae has increased significantly. However, despite the intense research effort by academic and corporate institutions, very few products with real potential have been identified or developed. Based on Silverplatter MEDLINE and Aquatic Biology, Aquaculture & Fisheries Resources databases, the literature was searched for natural products from marine macroalgae in the Rhodophyta, Phaeophyta and Chlorophyta with biological and pharmacological activity. Substances that currently receive most attention from pharmaceutical companies for use in drug development, or from researchers in the field of medicine-related research include: sulphated polysaccharides as antiviral substances, halogenated furanones from Delisea pulchra as antifouling compounds, and kahalalide F from a species of Bryopsis as a possible treatment of lung cancer, tumours and AIDS. Other substances such as macroalgal lectins, fucoidans, kainoids and aplysiatoxins are routinely used in biomedical research and a multitude of other substances have known biological activities. The potential pharmaceutical, medicinal and research applications of these compounds are discussed.     

The effects of seaweed harvesting on fishes: a critique

Synopsis Black & Miller (1991) concluded that there was no large impact of an experimental harvest of rockweed,Ascophyllum nodosum, on fishes. A critique of their study demonstrates that this conclusion cannot be substantiated by their data because of sampling biases, errors in experimental design and low statistical power. Further, evidence is presented which supports the hypothesis that rockweed may provide an important nursery habitat for juvenile fishes.     

植被砍伐对土壤养分的影响

研究了不同砍伐频率下,香港、深圳和鹤山研究样地山坡地Ｎ、Ｐ、Ｋ含量的差异．不同采样地之间,养分全量和有效量差异显著．在尚未砍伐的山坡地,土壤养分含量显著高于经常砍伐的山坡地．未伐土壤的Ｎ含量顺序为香港样地＞深圳样地＞鹤山样地．下层土壤Ｐ的含量高于上层土壤．深圳样地常代土壤养分含量高于鹤山．结果建议采用最适砍伐频率和在最适季节砍伐,以便减少砍伐产生的不利影响．     

Chemistry of the polysaccharides of the brown seaweed dictyopteris plagiogramma

Laminaran, fucose-containing polysaccharides (‘fucans’) and alginic acid were isolated from Dictyopteris plagiogramma.The laminaran comprised G- and M-chains (ratio 3: 1). The ‘fucans’ were present in four extracts of a four-step sequential extraction procedure and all contained slightly differing proportions of fucose, xylose, galactose, mannose, glucuronic acid residues and half-ester sulphate. Non-reducing chain ends as well as the positions of glycosidic linkages to fucose, xylose and glucuronic acid are the same as previously reported for other ‘fucans’. Galactose and mannose occur mainly as trisubstituted residues with substitution at 0-1, 0-3, 0-4 and at 0-1, 0-3, 0-6, respectively.     

我国蛇类养殖业发展的现状与思考

本文对我国蛇类养殖业发展现状进行了较为系统的总结,同时对我国经济蛇类自然资源及市场现状进行了分析,重点论述了经济蛇类的人工养殖技术发展现状及产业化进程中面临的关键问题,并提出了解决这些问题的对策.     

Semi-synthesis of a 3-O-sulfated red seaweed galactan-derived disaccharide alditol

Beta-D-Galp3-SO3-(1-->4)-3,6-anhydro-L-GalOH (agarobiitol 3(2)-sulfate, 4) was semi-synthetically prepared as follows: production of agarobiitol (1) from agarose by partial reductive hydrolysis, protection of the primary hydroxyl groups of 1 with trityl groups to produce the 1(1),6(2)-di-O-tritylated derivative (2), regioselective dibutylstannylene-mediated sulfation of 2 to give the 3(2)-O-sulfated-1(1),6(2)-di-O-tritylated compound (3), and detritylation of compound 3 to give the final product (4). This semi-synthetic route allowed the preparation of a red seaweed galactan-derived disaccharide alditol with sulfate group located at C-3 of the galactopyranosidic ring. Because red seaweed galactans are glycosidically linked at C-3 of the beta-D-Galp unit, a sulfated derivative with this structure could not be obtained by partial reductive hydrolysis of sulfated red seaweed galactans.     

Crocodile farming and conservation,the example of Zimbabwe

Crocodile farming is an important and lucrative activity in Zimbabwe which provides meat for human consumption and skins for the luxury leather industry. Because it gives an economic value to this otherwise unfriendly animal, farming crocodiles has a positive side effect on the conservation of this species in the wild. This paper gives an overview of the crocodile industry in Zimbabwe.     

An overview of seaweed resources in Chile

The seaweed harvest in Chile has doubled during the past decade, and export values have increased by 300% because of diversification and increase in the volume of products with greater value added. The export value of seaweed products increased from US $18 million in 1980 to $52 million in 1991. During the past decade, the successful cultivation of Gracilaria was implemented, and this has compensated for the large decrease in yields from natural beds. In the short term, it will be necessary to develop techniques for the cultivation of other resources such as Iridaea, Gigartina, Lessonia and Gelidium. Alternative biotechnological methods must also be developed, such as the use of Gracilaria strains with increased quality and production for growth in cultivation centers.     

Urbanization and its implications for food and farming

This paper discusses the influences on food and farming of an increasingly urbanized world and a declining ratio of food producers to food consumers. Urbanization has been underpinned by the rapid growth in the world economy and in the proportion of gross world product and of workers in industrial and service enterprises. Globally, agriculture has met the demands from this rapidly growing urban population, including food that is more energy-, land-, water- and greenhouse gas emission-intensive. But hundreds of millions of urban dwellers suffer under-nutrition. So the key issues with regard to agriculture and urbanization are whether the growing and changing demands for agricultural products from growing urban populations can be sustained while at the same time underpinning agricultural prosperity and reducing rural and urban poverty. To this are added the need to reduce greenhouse gas emissions and to build resilience in agriculture and urban development to climate change impacts. The paper gives particular attention to low- and middle-income nations since these have more than three-quarters of the world''s urban population and most of its largest cities and these include nations where issues of food security are most pressing.     

Dynamics of an age-structured population with Allee effects and harvesting

We propose a discrete-time, age-structured population model to study the impact of Allee effects and harvesting. It is assumed that survival probabilities from one age class to the next are constants and fertility rate is a function of weighted total population size. Global extinction is certain if the maximal growth rate of the population is less than one. The model can have multiple attractors and the asymptotic dynamics of the population depend on its initial distribution if the maximal growth rate is larger than one. An Allee threshold depending on the components of the unstable interior equilibrium is derived when only the last age class can reproduce. The population becomes extinct if its initial population distribution is below the threshold. Harvesting on any particular age class can decrease the magnitude of the possible stable interior equilibrium and increase the magnitude of the unstable interior equilibrium simultaneously.     

有机稻鸭共作对土壤理化性状和细菌群落空间分布的影响

为探明有机稻鸭共作对不同深度耕层土壤理化性状和细菌群落的影响,采用田间实验,研究了有机稻鸭共作(12年)和转型期稻鸭共作(3年)田在0～6、6～13和13～20 cm土层的理化性状和细菌群落结构变化规律。结果表明:有机稻鸭共作12年后,0～6和6～13 cm土壤理化性状得到较大程度改善,但13～20 cm层改变较小;与转型期稻鸭共作相比,有机稻鸭共作显著改变了细菌群落组成,使不同耕层土壤具有了更高比例的共同细菌门;同时还提高了各耕层土壤细菌群落的丰富度和多样性,减小了各耕层土壤细菌群落结构分布差异性,这在0～6 cm层土壤中表现尤为明显,使细菌群落结构整体朝着更加稳定方向发展;相关分析表明,pH值、土壤容重、全氮和硝态氮是影响有机稻鸭共作后土壤细菌群落空间分布的重要因子。综合来看,有机稻鸭共作主要通过改变土壤理化性状来影响细菌群落的空间分布,是促进农业可持续发展的一种重要模式。     

Fission and the dynamics of genets and ramets in clonal cnidarian populations

Until relatively recently many species of entomostracan crustaceans were thought to have widespread, even cosmopolitan distributions. Evidence now suggests that this is far less the case than thought. However, an exception appears to be provided by the crustaceans of episodically filled waterbodies. Typically these include Anostraca, Notostraca and Conchostraca. The paper considers the distribution of Triops australiensis (Branchiopoda: Notostraca) in Australia. There, it is a frequent inhabitant of episodically filled temporary waters. It is absent from such waters in northern Australia. A biogeoclimatic analysis using the program BIOCLIM indicates that this is because of the absence of suitable localities. BIOCLIM enables the preparation of maps which provide statistical predictions of climates suitable for the survival of a particular taxon. These predictions are based upon the known climate of localities where the taxon in question actually occurs. It is suggested that for the biota of shallow ephemeral waters (such as those typically inhabited by Anostraca, Conchostraca and Notostraca) biogeoclimatic analysis has a powerful predictive value.     

Macroalgal farming in the sea: water motion and nitrate uptake

A better understanding of water motion effects on nutrient uptake by marine crop plants should make it possible to farm the sea more effectively. Farms in China, Japan and the Philippines now grow plants on slack lines or nets that move with passing waves and currents. Nutrient uptake rates are increased onLaminaria farms in China by adding nitrogen-containing fertilizer. In contrast, forests of the giant kelp,Macrocystis grow in California at low nutrient levels without fertilization. The giant kelp, compared as a structure with the slack Chinese farms, has float-supported, spring-like stipes that stretch and recoil as waves pass. This motion seems likely to enhance flow over the thallus surface. In thus study we modified flow around kelp blades in a water tunnel in the laboratory by changing orifice plates, and flow around Chinese-style long-line farms in the sea by tightening them under various sea conditions. Our measurements suggest that if marine farms were designed and operated to increase water movement over the plants being grown, their rates of nutrient uptake, and growth would increase.This paper was presented at the Symposium on Applied Phycology at the Fourth International Phycological Congress, Duke University.     

Nutrient status in needles of Norway spruce and Scots pine following harvesting of logging residues

Nutrient concentrations in current and 1-year old needles from two Picea abies (L.) Karst and two Pinus sylvestris L. stands in Sweden were determined 8–10, 16–18 and 22–24 years after clear-felling and experimental manipulation of harvesting intensity. On all sites, three levels of harvest intensity had been applied in a randomized block design (n=4); (i) conventional stem-only harvesting, where all logging residues (i.e. tops, branches and needles) were evenly distributed on the ground, (ii) harvesting all above-ground tree parts except needles and (iii) above-ground whole-tree harvesting (no residues left on site). At stand age 8–10 years, nitrogen concentrations in the current year needles in plots where all residues or needles only were retained were higher than in whole-tree harvested plots, whereas concentrations of K, Ca and Mg were lower. The latter response was interpreted as a dilution effect. P:N, K:N, Ca:N, Mg:N, Mn:N and Zn:N were in general higher after whole-tree harvesting treatments than after the treatments where all residues or only needles had been left on site. At stand age 16–18 years, no significant differences in nitrogen concentrations were observed between treatments, but the levels of Ca, Mg and Mn in both current and 1-year-old needles were lower after whole-tree harvesting than after the treatments where logging residues remained on site. By contrast, potassium levels in the foliage were highest in treatments where only the needles were left on site, whereas the lowest levels were observed for treatments where all residues was left. At stand age 22–24 years, the treatment effects had diminished, except for the effects on Ca and K on the southern Norway spruce stand. It is concluded that the nutrient release from logging residues enhances nutrient uptake in trees of the succeeding forest generation, but this effect does not occur simultaneously for all elements. This revised version was published online in June 2006 with corrections to the Cover Date.