Factors controlling the growth of field populations of Hydrodictyon reticulatum in New Zealand

Since Hydrodictyon reticulatum was introduced to New Zealand it has spread rapidly and produced persistent annual nuisance growths in areas where nuisance algal had not occurred previously. Field bioassays were conducted at 10 sites between August 1993 and February 1995 to evaluate the seasonal growth patterns and the factors controlling growth under natural conditions. H. reticulatum exhibited a strong seasonal growth pattern with growth rates up to 0.33 doublings d^-1 from August to March, are duction in growth rate in April and little or no growth from May to July. The H. reticulatum present in New Zealand has are latively low requirement for dissolved inorganic nitrogen (DIN) in comparison with other nuisance species, with its growth rate being saturated at 200 mg m^-3. This and the high affinity for DIN as shown by a K_s of 29 mg m^-3 have been key factors in the establishment of nuisance growths of H. reticulatum in New Zealand. This revised version was published online in August 2006 with corrections to the Cover Date.     

Responses of Porphyra linearis (Rhodophyta) to environmental factors under controlled culture conditions

The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 ^°C), low PPF (70–140 mol photon m^-2s^-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s^-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.     

A study of gonadal organogenesis,and the factors influencing regeneration following surgical castration in Deroceras reticulatum (Pulmonata:Limacidae)

Summary At hatching, the hermaphrodite duct of Deroceras reticulatum consists of a single cell type designated the Gonadal Stem Cell (GSC). Proliferation of the GSC leads to the formation of numerous ductules each of which forms one of the acini of the gonad. The germinal and supporting cells are derived entirely from the GSC. The germ cells differentiate first, followed by the Sertoli and follicle cells. At the early sperm stage of gonadal development the hermaphrodite duct differentiates to function as a seminal vesicle. Once the GSC are committed to this change they lose their regenerative ability. The only remaining GSC are the cells of the acinar epithelium, and these retain their germinal potential until the death of the animal.Regeneration will occur from the hermaphrodite duct provided it is in the immature state, i.e., composed of GSC, and is exposed to the hormonal conditions of a young animal. Nervous connections and the presence of an artery are not necessary for this regeneration. The presence of a functional gonad does not inhibit regeneration.     

Selective grazing of acyanogenic white clover: Variation in behaviour among populations of the slug Deroceras reticulatum

Summary Collections of the slug Deroceras reticulatum were made from grassland sites containing contrasting frequencies of the cyanogenic morph of white clover, Trifolium repens. In choice chamber experiments, slugs obtained from sites with a low frequency of cyanogenic clover showed a significantly greater degree of selective eating of acyanogenic morphs than slugs taken from a site containing a high frequency of cyanogenic clover. Differences in selectivity between populations were caused both by differences in the rate of initiation of feeding on cyanogenic morphs, and by differences in the extent of damage once feeding had been initiated. The implications of these results for the cyanogenic polymorphism of T. repens are discussed.     

Dynamics of phytoplankton growth in the Waikato River,North Island,New Zealand

The Waikato River (latitude 38°S, longitude 176°E, North Island, New Zealand) is overwhelming y dominated by diatoms (mainly Melosira species) while blue-green and green algae are of minor importance. Both laboratory and in situ nutrient enrichment experiments showed enhanced growth of natural and index blue-green and green algae by addition of phosphate and nitrate. These algae were also shown to require higher temperature and light intensity than the diatoms. On the other hand, Waikato River with its higher silica content, moderate range of temperature and running water habitat was more favourable an environment for diatoms.     

Interactions between environmental variables on growth rate and carrageenan content of Solieria chordalis (Solieriaceae,Rhodophyceae) in culture

Using vegetative propagules (ramuli) of the iota carrageenan producing red seaweed Solieria chordalis, a maximum growth rate of 6.8% d⁻¹ was achieved when cultured at 20 °C and 100 μmol photon m⁻² s⁻¹ in seawater supplemented with 20 μM NO₃-N or 10 μM NO₃-N plus 10 μM NH₄-N. Ramuli grew less well when nitrogen was supplied solely as NH ₄ ⁺ . Maximum carrageenan content was observed at the same temperature, irradiance and salinity as growth, but at lower nitrogen concentrations. These findings are discussed in relation to results obtained from studies on other iota-carrageenan producing carrageenophytes.     

Modification of an algal culture medium for sustained growth of a saxitoxin-producing isolate of Alexandrium minutum

In order to study saxitoxin (STX) production bymicro-algae in the laboratory, a defined algal culture medium which supports optimum growth over a longtime-period is a requirement. In the development of such a medium, a number of modifications were made to a standard algal culture medium (GP) and growth of a STX-producing isolate of Alexandrium minutum in the different formulations was assessed by measuring maximum cell densities and mean generation times (MGT). All experiments were carried out under controlled conditions in an aerobic atmosphere with increased CO₂. Whilst maximum cell densities in the different modifications were similar, the MGT was significantly shortened by the addition of Tris buffer and the trace metals strontium, selenium and molybdenum. Replacement of natural with artificial seawater and removal of soil extract did not adversely affect algal growth. Five of the six media formulations supported the growth of A. minutumover a 9-month period. This revised version was published online in August 2006 with corrections to the Cover Date.     

温度、盐度对海月水母碟状体生长及存活的影响

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15-35条件下,海月水母碟状体可以在温度2.5-25℃存活,在15-25℃范围内可正常生长;在温度20-25℃和盐度20-30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15-35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。     

Influence of some environmental factors on Rhizopus nigricans submerged growth in the form of pellets

Morphological changes of a steroid transforming filamentous fungus Rhizopus nigricans were studied by altering submerged growth conditions at inoculum sizes previously determined to favor pelleted growth. Beside the main classification between pelleted and clumpy growth forms, the size, concentration and structure of pellets were characterized at different cultivating temperature, initial pH value, medium composition, additives, and aeration conditions. Initial pH below 4 and above 7, the presence of Ca²⁺ and Tween-80 gave rise to the clumpy growth, otherwise pelleted growth prevailed. Among tested factors the pellet size was mainly influenced by the inoculum size and the presence of baffles and Ca²⁺ in cultivation medium. The formation of smooth pellets, prerequisite for further application in the process of steroid biotransformation, resulted in cultivations at lower temperature, high agitation rates in shaken cultures without baffles and at high nitrogen concentration. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of environmental parameters on net photosynthesis of a free-living brown seaweed,Cystoseira barbata formarepens: determination of optimal photosynthetic culture conditions

The net photosynthesis of the Mediterranean brown seaweedCystoseira barbata f.repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 mol photon m^–2 s^–1; only very high irradiances induce photoinhibition. Maximum net photosynthesis occurred at temperatures ranging from 20 °C to 30 °C. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1^–1 NaCl, oxygen exchange is significantly reduced.Light, temperature and salinity requirements are discussed, taking into account ecological considerations. Yields and quality of alginic acid are presented according to the irradiance and yearly evolutionin situ in order to aid future cultivation of this species.     

Carabid beetle (Coleoptera: Carabidae) conservation in New Zealand

An overview of carabid beetles in the New Zealand conservation context is provided. Processes for threatened species recovery within the New Zealand Department of Conservation are outlined, and the Department’s two major beetle-related recovery documents (The Conservation Requirements for New Zealand’s Nationally Threatened Invertebrates, and The Carabid Beetle Recovery Plan) are discussed. A subjective consideration of the merits and drawbacks of both the documents, and the systems that support them, is presented, along with an option for the way forward for threatened species conservation in New Zealand.     

Influence of culture temperature on the growth,biochemical composition and fatty acid profiles of six Antarctic microalgae

The growth, biochemical composition and fatty acid profiles of six Antarctic microalgae cultured at different temperatures, ranging from 4, 6, 9, 14, 20 to 30 ^∘C, were compared. The algae were isolated from seawater, freshwater, soil and snow samples collected during our recent expeditions to Casey, Antarctica, and are currently deposited in the University of Malaya Algae Culture Collection (UMACC). The algae chosen for the study were Chlamydomonas UMACC 229, Chlorella UMACC 234, Chlorella UMACC 237, Klebsormidium UMACC 227, Navicula UMACC 231 and Stichococcus UMACC 238. All the isolates could grow at temperatures up to 20 ^∘C; three isolates, namely Navicula UMACC 231 and the two Chlorella isolates (UMACC 234 and UMACC 237) grew even at 30 ^∘C. Both Chlorella UMACC 234 and Stichococcus UMACC 238 had broad optimal temperatures for growth, ranging from 6 to 20 ^∘C (μ = 0.19 – 0.22 day^–1) and 4 to 14 ^∘C (μ = 0.13 – 0.16 day^–1), respectively. In contrast, optimal growth temperatures for NaviculaUMACC 231 and Chlamydomonas UMACC 229 were 4 ^∘C (μ = 0.34 day^–1) and 6–9 ^∘C (μ = 0.39 – 0.40 day^–1), respectively. The protein content of the Antarctic algae was markedly affected by culture temperature. All except Navicula UMACC 231 and Stichococcus UMACC 238 contained higher amount of proteins when grown at low temperatures (6–9 ^∘C). The percentage of PUFA, especially 20:5 in Navicula UMACC 231 decreased with increasing culture temperature. However, the percentages of unsaturated fatty acids did not show consistent trend with culture temperature for the other algae studied.     

Influence of environmental factors on the production of Potamothrix alatus paravanicus Poddubnaya & Pataridze (Tubificidae) in different areas of Lake Sevan

A modification of the Hynes' method was used to estimate production of Potamothrix alatus paravanicus Poddubnaya & Pataridze (Tubificidae), the dominant species of benthic invertebrate in Lake Sevan. Maximum production (5–24 g m^t\-2 wet weight) occurred in the sublittoral, while maximum biomass was found (8–17 g m^–2 wet weight) in the profundal. The turnover ratio of the average cohort varied between 2.4 and 5.0. The annual turnover ratio (P/B) decreased from 2.1–3.1 in the littoral to 0.1–0.4 in the profundal zone.A logarithmic correlation was found between P/B and temperature and oxygen regime, and depth and average size of clitellate specimens.     

Effect of nutrient supply on growth of blue mussels (Mytilus edulis) in a landlocked bay

The growth of blue mussels (Mytilus edulis) was studied in the landlocked bay Hopavågen in central Norway for 3 years, of which in 2 years (1998 and 1999) nutrients were added to increase the primary production. Nutrients (N:Si:P) were added daily from May to October in 1998 (molar ratio 15:5:4.1) and 1999 (molar ratio 16:8:1). The doses of nutrients correspond to 0.4 and 0.8 g P l^–1 day^–1 in 1998 and 1999 respectively. The growth of blue mussels (Mytilus edulis) in 1997 was followed at four depths (1, 2, 4 and 7 m). In 1998 and 1999 growth was followed at 2 and 10 m depths at four locations in Hopavågen and at a control station outside on the coast. The nutrient supply in 1998 only slightly increased the algal biomass (chlorophyll a), whereas mean daily primary production during the summer remained at the same level as the previous year. The increased nutrient supply in 1999 caused a nearly 50 and 100% increase in mean summer biomass and daily primary production, respectively. The growth of blue mussels in Hopavågen in 1997 and 1998 was within the same size range during the summer. In 1999 the shell length of blue mussels kept at 2 m depth was significantly higher than in the previous year at end of the growth season. The recorded growth was also significant higher than for mussels at 2 m depth at the control station. No difference in shell length was observed on mussels grown at 10 m depth in Hopavågen and in the control stations in 1998 and 1999. A higher tissue content was found in blue mussels grown at 2 m depth in Hopavågen, both in 1998 and 1999 when compared to the control groups. At 10 m depth no differences were recorded.     

Effect of temperature on the growth rate of Griffithsia tenuis C. Agardh (rhodophyta: ceramiales)

Clonal cultures of Griffithsia tenuis were grown for 18 days (Erdschreiber solution, LD 12 : 12, 2200 lux) at 13, 18, 22 and 25°C. The optimum temperature for growth (increase in number of cells) under these conditions was 22°C.

     

Effect of nutrients on the growth of a new alpine strain of Haematococcus (Chlorophyceae) from New Zealand

The microalga Haematococcus lacustris is a source of astaxanthin used widely in aquaculture, pharmaceutical, and cosmetic industries. A new strain of Haematococcus (LCR‐26C‐1f) isolated from the New Zealand alpine zone was evaluated in this study. The influence of vitamins, micronutrients, various carbon and nitrogen sources were investigated to maximize biomass production in batch cultures using shake flasks. Supplementation of vitamins consisting of thiamine, biotin, and cyanocobalamin improved the cell density by 40% over the vitamin‐free medium. Out of the individual vitamins tested, thiamine was shown to be necessary to maintain high cell densities. The best nitrogen source tested was nitrate in the form of sodium nitrate_, at a 40 mM concentration. Heterotrophic growth yielded much lower cell densities compared to autotrophic growth. The micronutrients iron and manganese were essential for growth. However, the best growth was obtained using a micronutrient mix that included iron, copper, cobalt, zinc, manganese and molybdenum.     

环境因子对东海原甲藻生长及脲酶活性的影响

以我国东南沿海大规模赤潮原因种东海原甲藻为实验材料,研究了环境因子对其生长及脲酶活性的调控作用。结果表明,东海原甲藻的适宜生长温度为20—25℃,而25℃下脲酶活性最高。在光强2μmol m-2s-1条件下细胞密度显著下降(P0.05),但仍能维持较高的脲酶活性(9.405 fmol h-1个-1)。在盐度20—40范围内,东海原甲藻能够维持快速生长和较高的脲酶活性。氮源组成对东海原甲藻生长无显著影响,但对脲酶活性影响较大。具体而言,东海原甲藻脲酶活性与尿素浓度呈显著正相关关系,而无机氮源NH+4和NO-3对其脲酶活性具有显著的抑制作用,在氮缺乏条件下脲酶活性明显增强。东海原甲藻脲酶活性对环境温度、光照、盐度和营养的响应特征可能是在长期进化中形成的生态适应策略,使其在无机氮源不足时得以转而利用有机氮源,从而在资源竞争中占据有利地位。     

环境因子及规格对菲律宾蛤仔幼贝潜沙行为的影响

作为埋栖型滩涂贝类的典型代表种类,菲律宾蛤仔Ruditapes philippinarum具有很强的潜沙行为。为了进一步了解其生态行为学,在室内实验室条件下,模拟了常见环境因子温度、盐度、p H值以及流速和规格大小对蛤仔幼贝(6—12 mm)潜沙速度的影响。结果表明,温度10—30℃,盐度25—30,p H值在6.0—9.0范围内蛤仔幼贝均能100%潜沙;在试验观察的4—5 h内,盐度由30突变至10时没有蛤仔潜沙,突变至20时有20%—30%潜沙(20℃,庄河蛤仔)或100%潜沙(15℃,福建蛤仔);p H值由8.0突变至10.0时不能潜沙;以暂养海水的温度(15或20℃)、盐度(30)和p H值(8.0)为中心,随着各个指标向两侧突变潜沙时间延长;流速为3、4和5 cm/s时,随流速增大潜沙速度加快;在规格6、9 mm和12 mm的幼贝中,以12 mm潜沙速度最快。若以半数潜沙时间(ET_(50))为判定指标,则适宜潜沙温度为15—20℃,盐度为25—30,p H值为7—9(莆田蛤仔)和8.0(庄河蛤仔)。在适宜条件下,蛤仔幼贝1 min内开始潜沙,3 min内有半数潜沙,5 min便全部潜沙。研究发现环境突变对蛤仔潜沙有明显影响,在天然海区放养蛤仔时应该注意购买地和放养海区温度、盐度和p H值的差异,并且选取10 mm以上幼贝放养效果较好。所得结论对完善菲律宾蛤仔幼贝的行为学及其底播养殖技术提供了有意义的参考。     

Effects of temperature and salinity on the growth of Gracilaria verrucosa and G. chorda, with the Potential for mariculture in Korea

Effects of temperature and salinity on the growth of the two agarophytes, Gracilaria verrucosa (Hudson) Papenfuss and Gracilaria chorda Holmes were examined in Korea. Both species grew over a wide range of temperatures (10–30 ^∘C) and salinities (5–35‰), and grew well at 17–30 ^∘C and a salinity of 15–30‰. In culture, G. verrucosa grew faster than G. chorda and their maximum growth rates were 4.95% day⁻¹ (30 ^∘C, 25‰) and 4.47% day⁻¹ (at 25 ^∘C, 25‰), respectively. In the field population the maximum growth and fertility of G. chorda were observed in summer. The growth rate of G. verrucosa was slightly higher than that of G. chorda for 2 weeks on the cultivation rope and in culture but it was much lower after being contaminated with epiphytes. The biomass of the epiphytes was 0.82 g dry wt. per host plant in G. verrucosa and 0.001 g in G. chorda. G. chorda exhibited resistance to epiphytism and grew 7 times in length and the dry weight increased 15 times after 55 days. In conclusion, G. chorda appears to be a good agarophyte with a fast growth rate and resistance to epiphytesm, and compared with G. verrucosa, has good potential for commercial cultivation.     

Impacts of introduced common wasps (Vespula vulgaris) on experimentally placed mealworms in a New Zealand beech forest

An introduced social wasp Vespula vulgaris may compete with native birds for honeydew and invertebrates in New Zealand forests. Experimentally hidden mealworms (Tenebrio molitor) persisted longer at two sites following wasp poisoning that at two sites where wasps were not poisoned. Mealworms persisted longer in the morning than in the afternoon within all study sites. An unusually low mealworm removal rate during a morning trial before wasp poisoning heavily influences the results of this experiment but we have no ecological reason to ignore it. Wasps may therefore be having a heavy impact on invertebrate abundance on very short time scales (within a day following dawn emergence). They may also remove cached food items that would otherwise be retrieved by the South Island robin (Petroica australis australis) during cold or dark feeding conditions.