Survival and growth of transplants of laboratory raised axenic seedlings of Enhalus acoroides (L.f.) Royle and field-collected plants of Syringodium isoetifolium (Aschers.) Dandy, Thalassia hemprichii (Ehrenb.) Aschers. and Halodule pinifolia (Miki) den Hartog

Experimental transplantation investigations, using laboratory raised axenic seedlings of Enhalus acoroides and natural populations of Syringodium isoetifolium, Thalassia hemprichii and Halodule pinifolia in the Gulf of Mannar Marine Biosphere Reserve, found that the denuded seagrass ecosystem of this Gulf can effectively be restored with plug and turfs methods of seagrass transplantation. Axenically developed E. acoroides, transplanted by the staples method, established by adapting to the prevailing environmental conditions. 0% seedlings “washed ashore” when the staples method was adopted using ‘L’ shaped bamboo sticks for transplanting E. acoroides and S. isoetifolium seedlings. This suggests that the seagrass transplantation using “L” shaped bamboo sticks, as staples will be technically feasible and eco-friendly for future seagrass transplantation programmes. Substratum type, duration of low tide exposure and environmental parameters like surface water temperature and turbidity are key parameters determining the success of the transplantation attempts.     

芘暴露对马氏珠母贝鳃和肝胰腺抗氧化酶活性的影响

在实验生态条件下,采用生态毒理学方法,选用海洋环境中常见的有机污染物多环芳烃芘（Pyrene）,以马氏珠母贝（Pinctada martensi）为实验材料进行毒理实验。研究了芘不同质量浓度（8、16、32和64μg·L^-1、不同时间（7,10 d）的胁迫对马氏珠母贝鳃和肝胰腺组织中超氧化物歧化酶（SOD）、过氧化物酶（POD）和谷胱甘肽过氧化物酶（GPx）3种抗氧化酶活性的影响。结果表明：3种酶在不同组织和不同胁迫时间的敏感性有所差异,在芘胁迫马氏珠母贝第7天,鳃组织中 SOD、POD、GPx 3种酶活性主要表现为诱导现象,高质量浓度组对3种酶活性均具有极显著诱导作用（p〈0.01）,而芘胁迫对肝胰腺3种酶活性的影响主要表现为抑制作用,且POD酶活性表现最敏感,在较低浓度组就被显著抑制（p〈0.01）;到染毒第10天,鳃组织中SOD、GPx两种酶诱导作用明显,POD诱导现象不显著（p〉0.05）,肝胰腺中3种酶活性与对照组相比诱导明显,并表现出一定的剂效关系。两种组织中SOD和GPx活性的变化具有一定的同步性。通过比较最低可观察效应质量浓度（LOEC）,发现在第7天,鳃组织中敏感性强弱表现为SOD=POD〉GPx,肝胰腺中表现为POD〉GPx〉SOD,而到第10d,两组织中敏感性又分别表现为GPx〉SOD〉POD,GPx=SOD〉POD。因此,在较短的暴露时间,POD酶活性可作为芘胁迫对马氏珠母贝的生物标志物,而对于较长时间的染毒实验,可选用 GPx 酶作为芘胁迫对马氏珠母贝的生物标志物以监测海洋环境芘污染。     

Influence of light and temperature on the photosynthetic rate of marine benthic diatoms

The influence of light and temperature on photosynthetic rate as measured by C¹⁴O₂-fixation of marine benthic diatoms was investigated, using both intact sediment samples (Marshall et al., 1973) and suspensions of diatoms harvested by a lenstissue technique (Eaton and Moss, 1966). After C¹⁴-incubation, sediment samples were filtered, burned in a sample oxidizer, and their activity determined in a liquid scintillation counter. Photosynthetic rate of mixed field populations is saturated by a light intensity of approximately 10,000 lux; at still higher light intensities no photoinhibition was found. In contrast to the mixed field populations, unialgal cultures of the benthic diatom Amphiprora alata Kütz. exhibited strong photoinhibition at higher light intensities (10,000 to 60,000 lux). Within a range of 4° to 20°C, the photosynthetic rate increased about 10%/C^o. No differences in photosynthetic pattern were observed between epipelic and epipsammic species.     

The effects of air pollution on work loss and morbidity

The pending revision of U.S. air standards and the analytic requirements of Executive Order 12291 will force regulators to examine closely the data showing possible human health effects from air pollution. A number of studies have investigated the relationship between air pollution and human mortality using an epidemiological approach. This study uses a data set on individuals, the Health Interview Survey, conducted by the National Center for Health Statistics, to examine the relationship between air pollution and various measures of morbidity. Regressions run with the total sample and a subsample of male nonsmokers indicate a statistically significant relationship between particulates and both work loss and restricted activity days. Further analysis considering alternative functional forms also indicates that the ambient level of particulates is still significantly related to the measure of morbidity.     

Pigment content and photosynthetic rate of the fronds of Macrocystis pyrifera

The Macrocystis pyrifera (L.) C. Ag. frond is here described in terms of chlorophyll a, fucoxanthin, chlorophyll c and photosynthetic rate. Pigment concentrations increased back from the apical meristem reaching a maximum after 2 to 3 m. Pigment concentrations were then generally constant throughout most of the length of the frond, finally decreasing again in the oldest parts of the frond with the exception of the sporophylls. Pigment ratios remained relatively constant throughout. Maximum net photosynthetic rates on a given frond showed a decrease with tissue age on both an area basis (1040 down to 463 nmol O₂ cm^-2 h^-1) and on a chlorophyll a basis, which was shown as half-saturation constants (quantum irradiance) which dropped on an area basis from 85 mol m^-2 sec^-1 at 4.5 m above the holdfast to 26 mol m^-2 sec^-1 at 15.5 m. Young sporophytes transplanted from the sea floor to the surface (12 m) tended to decrease pigment content, while those transplanted to the bottom tended to increase all pigments, but especially fucoxanthin. Photosynthetic rates, however, changed little on a unit area basis. The results of these data are considered in the light of recent work on photosynthetic units, tissue age effects and general adaptations of the M. pyrifera frond to its light environment.     

Effect of manganese toxicity on pigment content,Hill activity and photosynthetic rate of Vigna radiata L. Wilczek seedlings

Effect of different concentrations, viz. 10(-4) M, 5 x 10(-4) M, 10(-3) M and 5 x 10(-3) M of manganese sulphate (MnSO4, 7H2O) on chlorophyll, carotenoid pigment content and photosynthesis of mungbean seedlings was examined Progressive increase in manganese sulphate concentration upto 5 x 10(-3) M brought about a progressive decrease in total chlorophyll and chl a content. Chl b content changed very little by excess manganese treatment. Total carotenoid pigment content decreased considerably in comparison to control with every concentration of manganese sulphate tried here. Hill activity of chloroplasts isolated from leaves of mungbean seedling and rate of photosynthesis in terms of CO2 uptake showed progressive reduction along with the increase in concentration of the manganese.     

微囊藻毒素对几种淡水微藻的生长和光合活性的影响

微囊藻毒素(MC)是富营养化淡水水体中最常见的藻类毒素,而MC对藻类生长效应的影响却鲜见报道.通过模拟培养实验,研究了不同质量浓度的MC-RR对淡水藻类的生长和光合效能的影响.结果显示,100 μg·L-1以下的MC-RR对产毒铜绿微囊藻Ds(Microcystis aeruginosa Ds)作用并不明显;相反,100 μg·L-1 MC-RR对铜绿微囊藻无毒株854(Microcystis aeruginosa 854)有显著的杀藻效应,表明MC可能改变浮游植物种群中产毒与非产毒微囊藻的比例.MC-RR对其它藻类的作用因种类不同而效果各异.100 μg·L-1 MC-RR可显著抑制细长聚球藻(Synechococcus elongatus)的生长,并诱使水华束丝藻(Aphanizomenon flos-aquae)发生溶藻效应;100 mg.L-1显著降低了聚球藻和束丝藻的光合活性,表明微囊藻毒素对藻类生长的抑制与其对光合活性的抑制有关.100 μg·L-1以下的 MC-RR对蛋白核小球藻(Chlorella pyrenoidosa)、斜生栅藻(Scenedesmus obliquus)、水华鱼腥藻(Anabaena flos-aquae)的生长没有明显影响;1 000 μg·L-1 MC-RR 则可促进这三种藻的生长,但对小球藻和鱼腥藻的光合效能没有明显影响.以上结果说明MC参与浮游植物的种间相互作用与种群调节.     

The origin of nitrogen and phosphorus for growth of the marine angiosperm Thalassia testudinum

Marine Biology - How are high rates of production by Thalassia testudinum König maintained in notably nutrient-poor tropical waters? Yield-nutrient supply correlations indicate that a...     

Influence of sediment nitrogen-availability on carbon and nitrogen dynamics in the seagrass Thalassia testudinum

Variations in tissue carbon (C), nitrogen (N) content, and non-structural carbohydrate (NSC) reserves in the turtle grass Thalassia testudinum Banks ex König were examined in relation to changes in sediment-N availability in Corpus Christi Bay (CCB) and lower Laguna Madre (LLM), Texas, USA, from May to October 1997. Under natural conditions, sediment pore-water NH⁺ ₄-concentrations were higher at CCB (100?μM) than at LLM (30?μM); this difference was reflected in a significantly higher leaf and rhizome N-content at CCB than at LLM. However, sediment NH⁺ ₄-enrichment using a commercial fertilizer resulted in significantly higher tissue N-content relative to controls at both sites. N enrichment also influenced plant carbon metabolism, as reflected by distinct increases in leaf C-content at both sites. Significant decreases in rhizome NSC-content was recorded during the first two months of the experiment, suggesting that C was reallocated from rhizomes to leaves to support stimulated leaf growth at both sites. At LLM, leaf growth-rates increased and leaf turnover-time decreased as a result of sediment NH⁺ ₄-enrichment. With respect to chlorophyll, concentrations did not change significantly at CCB, but increased steadily at LLM after the first month following fertilization. In general however, chlorophyll concentrations in control plots were significantly higher at CCB than that at LLM. These observations suggest that leaf function related to C-fixation is enhanced under higher sediment N conditions, as reflected in higher leaf growth-rates and increased blade chlorophyll-content. In contrast, under low-N conditions, below-ground tissue production is enhanced at the expense of the above-ground shoots and leaves, resulting in the high below: above-ground biomass ratios often observed in seagrass beds of oligotrophic environments.     

The effect of organic material and inorganic ions on the photosynthetic rate of the red alga Bostrychia binderi from a Florida estuary

Various constituents of spring water (calcium, bicarbonate, nitrate, phosphate, total organic material) influence the response of photosynthetic rate of Bostrychia binderi Harvey to changes in salinity. The rate of photosynthesis increased with a decrease in salinity. The rate of photosynthesis in low salinities was greater in seawater diluted with spring water than in sewater diluted with distilled water. Elevation of photosynthetic rates in the lower salinities (0 and 5 ppt) was partially due to increased levels of bicarbonate and various nutrients present in natural spring water. The higher calcium levels in spring water resulted in higher photosynthetic rates in plants held for 3 to 7 d in the lower salinities (0 to 5 ppt). Increased levels of calcium in salinities of 5 ppt or higher increased the photosynthetic rate only during the first 7 d of exposure, since acclimation occurred equally in individuals held for 2 to 8 wk in sewater diluted with distilled or spring water. This study suggests that the diverse algal floras, characteristic of estuaries on the west coast of Florida are in part the result of natural spring water mixing with seawater, sustaining the algae over short periods of low salinities.     

Phytoplankton photosynthetic activity and growth rates in the NW Adriatic Sea

Taxonomic composition, biomass, primary production and growth rates of the phytoplankton community were studied in two stations in the NW Adriatic Sea on a seasonal basis, in areas characterized by differing hydrological and trophic conditions. The main differences between the two stations were quantitative rather than qualitative, most phytoplankton species being common to both stations. The effects of differing nutrient concentrations and plume spreading were evident. Biomass and primary production rates were significantly higher in the coastal station (S1), and the phytoplankton distribution in the water column was markedly stratified in S1 and more even in the offshore station (S3). However, chlorophyll a specific production, potential growth rate and production efficiencies were very similar in both stations, even when phosphorus concentrations were limiting. A discrepancy between potential and actual growth rate was observed: as a feature common to both stations, comparisons between potential and actual growth rates revealed that little carbon produced by phytoplankton accumulated as algal biomass; therefore, very high loss rates were estimated.     

Genetic and environmental effects on the growth rate of Littorina saxatilis

Transfer experiments with two morphs of Littorina saxatilis Olivi (=L. rudis) typically inhabiting exposed and sheltered localities, showed a between-morph difference in shell growth in the same type of habitat, and a withinmorph difference between exposed and sheltered environments. The former indicates a genetic difference between the two morphs, although growth rate has an environmental component as shown by the latter. Juvenile snails of the exposed morph were on average slightly larger than sheltered morph juveniles on hatching, but at 20 wk, when raised in identical environments, the sheltered morph juveniles had grown significantly larger than the exposed ones. A rise in temperature from 5° to 10°C enhanced growth rate for snails raised in the laboratory. Temperature alone could not however explain increased growth during the spring and summer in natural populations.     

The effects of license plate-based driving restrictions on air quality: Theory and empirical evidence

A typical driving restriction prohibits drivers from using their vehicles on given weekdays, based on the last digits of their vehicles’ license plates. A number of cities in developing countries have used license plate-based driving restrictions as a policy for reducing urban air pollution and traffic congestion. This paper develops a theoretical model of the effects of license plate-based driving restrictions on air quality that combines an economic model with information about the sources and atmospheric chemistry of different air pollutants. We then draw upon suggestive empirical evidence from license plate-based driving restrictions implemented in Bogotá, Colombia. Consistent with our theory model, we find suggestive empirical evidence that under certain circumstances, due to substitution, the purchase of a second car, the use of alternative modes of transportation, and/or atmospheric chemistry, it is possible for license plate-based driving restrictions to increase air pollution. Also consistent with our theory, we find that license plate-based driving restrictions may have different effects on different air pollutants, reflecting heterogeneity in the sources and atmospheric chemistry of the pollutants. In particular, owing to atmospheric chemistry, it is possible for a license plate-based driving restriction to cause a significant decrease in NO and a significant increase in NO₂, NO_x, and O₃.     

Hydrodynamics,diffusion-boundary layers and photosynthesis of the seagrasses Thalassia testudinum and Cymodocea nodosa

Photosynthetic rates of aquatic plants frequently increase with increasing current velocities. This is presumably due to a reduction in the thickness of the diffusion boundary-layer which allows for a higher carbon availability on the plant surface. Blades of the seagrasses Thalassia testudinum and Cymodocea nodosa exposed to different current velocities under controlled laboratory conditions, showed increased photosynthetic rates with increasing flow only at low current velocities (expressed as blade friction velocities, u _*). Carbon saturation of photosynthetic processes occurred at a relatively low u _* level (0.25 cm s^-1) for T. testudinum collected from a calm environment compared to C. nodosa (0.64 cm s^-1) collected from a surf zone. No further enhancement of photosynthetic rates was observed at higher u _* levels, suggesting limitations in carbon diffusion through the boundary layer below critical u ^* levels and possible limitations in carbon fixation by the enzymatic system at higher u _* levels. These results, as well as those of previous theoretical studies, assumed the flow on the immediate seagrass-blade surface to be hydrodynamically smooth. The presence of epiphytes and attached debris causes the surface of in situ seagrass blades to be exposed to flows ranging from smooth to rough-turbulent. As a consequence, the boundary-layer thickness on moderately epiphytized blades under medium to high flow-conditions is not continuous, but fluctuates in time and space, enhancing carbon transport. In situ u _* levels measured directly on blades of seagrasses indicate that T. testudinum and C. nodosa can be exposed to conditions under which the boundary layer limits photosynthesis during short periods of time (milliseconds) during low-energy events. As waves cause the thickness of the diffusion boundary-layer to fluctuate constantly, carbon-limiting conditions do not persist for prolonged periods.     

Long-term effects of ultraviolet radiation on growth and photosynthetic performance of polar and cold-temperate macroalgae

Long-term effects of artificial ultraviolet radiation (UV) and natural solar radiation on growth and photosynthetic activity, as measured by chlorophyll fluorescence, were investigated in 13 different polar and cold-temperate macroalgal species. Isolates of five different species from the Arctic and Antarctic were exposed to different light treatments of photosynthetically active radiation (PAR), PAR+UVA and PAR+UVA+UVB. Eight different species collected on the island of Helgoland, North Sea, Germany, were studied in the laboratory and under natural solar radiation conditions. Increase in fresh weight and changes in photosynthetic performance were monitored over a period of 3-4 weeks. The sublittoral polar species, particularly the Antarctic red algal species Gymnogongrus antarcticus and G. turquetii, the Arctic cold-temperate brown alga Alaria esculenta and, very drastically, the Arctic-endemic Laminaria solidungula, exhibited strong inhibiting effects of artificial UVB radiation on growth. In the cold-temperate sublittoral growth of the red algae Phycodrys rubens and, to a lesser extend, Membranoptera alata was substantially inhibited by UV radiation. In contrast, eulittoral species, e.g. Fucus serratus, did not show any differences in growth with respect to artificial irradiation conditions, with or without UV radiation. In the laboratory, some individuals of the green alga Codium fragile exhibited strong morphological changes of the whole thallus, particularly under UVB exposure. In the experimental outdoor set up, growth of most of the algal species was already inhibited by the full solar UV waveband, but, apart from Polyides rotundus, no additional UVB effect could be detected. Changes of in vivo fluorescence were not always consistent with the measurable changes in growth rate, indicating that physiological processes leading to an inhibition of growth may act independently of changes in photosynthetic activity. For the polar species, a general correlation between the natural vertical distribution in the field and the individual sensitivity towards UV radiation was indicated, while for eulittoral species from Helgoland no clear relationship was found. The obtained results show that measuring growth is a good ecological parameter to monitor long-term effects of UV radiation on single macroalgal species and the possible resulting changes of whole algal communities in coastal ecosystems.     

Effects of light exposure on the retention of kleptoplastic photosynthetic activity in the sacoglossan mollusc <Emphasis Type="Italic">Elysia viridis</Emphasis>

The effects of light exposure on the photosynthetic activity of kleptoplasts were studied in the sacoglossan mollusc Elysia viridis. The photosynthetic activity of ingested chloroplasts was assessed in vivo by non-destructively measuring photophysiological parameters using pulse amplitude modulation (PAM) fluorometry. Animals kept under starvation were exposed to two contrasting light conditions, 30 μmol photons m⁻² s⁻¹ (low light, LL), and 140 μmol photons m⁻² s⁻¹ (high light, HL), and changes in photosynthetic activity were monitored by measuring the maximum quantum yield of photosystem II (PSII), F _v/F _m, the minimum fluorescence, F _o, related to chlorophyll a content, and by measuring rapid light-response curves (RLC) of relative electron transport rate (rETR). RLCs were characterised by the initial slope of the curve, α_RLC, related to efficiency of light capture, and the maximum rETR level, rETR_m,RLC, determined by the carbon-fixation metabolism. Starvation induced the decrease of all photophysiological parameters. However, the retention of photosynthetic activity (number of days for F _v/F _m > 0), as well as the rate and the patterns of its decrease over time, varied markedly with light exposure. Under HL conditions, a rapid, exponential decrease was observed for F _v/F _m, α_RLC and rETR_m,RLC, F _o not showing any consistent trend of variation, and retention times ranged between 6 and 15 days. These results suggested that the retention of chloroplast functionality is limited by photoinactivation of PSII reaction center protein D1. In contrast, under LL conditions, a slower decrease in all parameters was found, with retention times varying from 15 to 57 days. F _v/F _m, α_RLC and rETR_m,RLC exhibited a bi-phasic pattern composed by a long phase of slow decrease in values followed by a rapid decline, whilst F _o decayed exponentially. These results were interpreted as resulting from lower rates of D1 photoinactivation under low light and from the gradual decrease in carbon provided by photosynthesis due to reduction of functional photosynthetic units.     

A note on some mathematical models on the effects of Bt-maize exposure

Some mathematical models for the estimation of the effects of Cry1Ab and Cry1F Bt-maize exposure in the biodiversity are examined. Novel results about these models are obtained and described in this note. The exact formula for the proportion of population that suffers mortality exposed either to Cry1Ab or Cry1AF pollen is derived. Moreover, regarding Cry1F pollen effects, the species sensitivity of Lepidoptera is discussed.     

Effects of in situ CO2 enrichment on the structural and chemical characteristics of the seagrass Thalassia testudinum

Seagrasses commonly display carbon-limited photosynthetic rates. Thus, increases in atmospheric pCO₂, and consequentially oceanic CO_2(aq) concentrations, may prove beneficial. While addressed in mesocosms, these hypotheses have not been tested in the field with manipulative experimentation. This study examines the effects of in situ CO_2(aq) enrichment on the structural and chemical characteristics of the tropical seagrass, Thalassia testudinum. CO_2(aq) availability was manipulated for 6 months in clear, open-top chambers within a shallow seagrass meadow in the Florida Keys (USA), reproducing forecasts for the year 2100. Structural characteristics (leaf area, leaf growth, shoot mass, and shoot density) were unresponsive to CO_2(aq) enrichment. However, leaf nitrogen and phosphorus content declined on average by 11 and 21 %, respectively. Belowground, non-structural carbohydrates increased by 29 %. These results indicate that increased CO_2(aq) availability may primarily alter the chemical composition of seagrasses, influencing both the nutrient status and resilience of these systems.     

Meiofauna on the seagrass Thalassia testudinum: population characteristics of harpacticoid copepods and associations with algal epiphytes

The composition and abundance of bladedwelling meiofauna was determined over a 15 mo period (1983–1984) from a Thalassia testudinum Banks ex König meadow near Egmont Key, Florida, USA. Harpacticoid copepods, copepod nauplii, and nematodes were the most abundant meiofaunal taxa on T. testudinum blades. Temporal patterns in species composition and population life-history stages were determined for harpacticoid copepods, the numerically predominant taxon. Sixteen species or species complexes of harpacticoid copepods were identified. Harpacticus sp., the most abundant harpacticoid, comprised 47.8% of the total copepods collected, and was present throughout the study. Copepodites dominated the population structures of the blade-dwelling harpacticoid species on most collection dates. Ovigerous females and/or copepodites were always present, indicating continuous reproductive activity. Results suggest that epiphytic algae influence meiofaunal abundance on seagrass blades, as densities of most meiofaunal taxa at Egmont Key were positively associated with percent cover of epiphytic algae throughout the study. The majority of significant correlations between meiofaunal density and cover of epiphytic algae involved filamentous algae, although encrusting algae dominated the epiphytic community. It appears that resources provided by epiphytic algae to seagrass meiofauna (additional food, habitat, and/or shelter from predation) may be associated with algal morphology.