鹿回头造礁石珊瑚群落多样性的现状及动态

通过对鹿回头岸礁（１０９°２８＇Ｅ,１８°１３＇Ｎ）造礁石珊瑚群落进行系统取样调查,分析了现有群落整体的成分组成,α－多样性和β－多样性及其在环境梯度上的变化;根据现有群落实际是处于不同演替时期地段的复合体的特点,把处于相同演替时期地段的综合特征作为分析群落整体在相应时期多样性特征的依据,探讨了群落演替过程中的多样性动态。研究发现：①中等水深（２．５￣５．０ｍ）地段的物种多样性平均值高于其他地段,     

SEASONAL CYCLING OF ALGAL NUTRIENT LIMITATION IN CHAUTAUQUA LAKE,NEW YORK1

Algal nutrient enrichment bioassays were conducted between May 1975 and August 1978 using water samples collected from Chautauqua Lake, New York. Photosynthetic fixation rates of natural phytoplankton assemblages were enhanced by additions of phosphorus and nitrogen, although enrichment with other nutrients had no significant stimulatory effect on algal photosynthesis. Whereas phosphorus stimulated in spring and early summer, both nitrogen and phosphorus enhanced photosynthesis in midsummer and fall. Relative to the effect of phosphorus enrichment, enhancement of photosynthesis by nitrogen during the summer and fall was highest in the northern part of the lake. During the period of ice cover, photosynthesis did not appear to be limited by nutrients in that nutrient additions (P, N, Si, C, Fe, trace metals) did not enhance fixation rates. Observed temporal fluctuations in the response of the algae to P and N correlated with changes in the lake water N:P ratio as well as with temporal changes in dissolved orthophosphate and nitrate-nitrite nitrogen. The N:P ratio decreased drastically in the summer and remained at ca. 10 or less through mid-fall, suggesting that N concentrations were inadequate for the non-N-fixing phytoplankton. Studies over 3 yr indicate that states of P and N limitation undergo time-space fluctuations that occur in a cyclic pattern in the surface waters of Chautauqua Lake.     

SEASONAL CHANGES IN SIZE STRUCTURE OF SARGASSUM AND TURBINARIA POPULATIONS (PHAEOPHYCEAE) ON TROPICAL REEF FLATS IN THE SOUTHERN RED SEA1

Seasonal variation in density, thallus length and biomass, population size structure, and allometric length‐biomass relationships was investigated in populations of Sargassum ilicifolium (Turner) C. Agardh, Sargassum subrepandum (Forssk.) C. Agardh, and Turbinaria triquetra (J. Agardh) Kütz. (Phaeophyceae) on shallow reef flats in the southern Red Sea. Thallus length and biomass varied strongly with season, with the highest values occurring in the cooler months. Thallus densities showed no significant temporal variation. Log‐total biomass versus log‐density relationships were positive throughout the growth season without any decrease in the slope of the relationship. In two populations, biomass‐density combinations approached the interspecific biomass‐density line, but the massive annual shedding of modules occurred before self‐thinning would set in. Allometric length‐biomass relationships varied with season in all populations and were associated with seasonal module initiation, growth, and shedding. Evidence of a strong asymmetric competition was found in two high‐density populations. These populations showed a predominance of small thalli during peak development, asymmetrical Lorenz curves, increasing Gini coefficients, and increasing thallus length relative to biomass during the main growth phase. In two other less crowded populations, small thalli were absent during peak development, Lorenz curves were symmetrical, and Gini coefficients decreased during the main growth phase. In these populations, size equalization appears to be due to responses at the modular level rather than size‐dependent mortality. We conclude that changes in size structure in this highly seasonal environment are determined by module dynamics, modified by asymmetric competition in some populations, with a minor role of recruitment and no regulatory effect of self‐thinning.     

SIZE STRUCTURE AND DYNAMICS IN A POPULATION OF SARGASSUM MUTICUM (PHAEOPHYCEAE)

Sargassum muticum (Yendo) Fensholt is an introduced brown seaweed with a very distinctive seasonal growth cycle on European shores. The present study links the dynamics of a population of S. muticum with the seasonal growth cycle of the species and the density-dependent processes operating throughout this cycle. Results indicate that both growth cycle and intraspecific competition influenced the structure and population dynamics. Size inequality increased during the slow growth phase (autumn–winter) of the 2-year study. Mechanisms generating inequality of size could be the existence of asymmetric competition and the inherent differences in growth rates between old (regenerated) and new thalli (recruits). Inequality of size distributions decreased progressively during the last months of the growth phase (spring–summer) and could be related to a process of self-thinning. There was a negative biomass–density relationship (as a measure of biomass accumulation-driven mortality) that confirms the importance of self-thinning as a major demographic factor in the S. muticum population.     

SEASONAL PATTERNS OF MORPHOLOGICAL VARIABILITY IN SARGASSUM POLYCERATIUM (PHAEOPHYTA)1

Temporal variability in certain morphological and taxonomically important features was quantified for Sargassum polyceratium Mont. from a population in the Content Keys, Florida (U.S.A.). Patterns of blade development, senescence, and loss caused pronounced seasonal changes in blade length-width ratios. Blade length and width were maximal early in the growing season (August-November) and decreased as the annual stems matured. Early in the growing season, plants had broader blades with randomly distributed cryptostomata. Late in the growing season (February-April), plants had more linear blades with cryptostomata approximately arranged in two rows, one on each side of the midrib. The length-width ratio of blades increased acropetally along the stems and were directly correlated to the size of the cryptostomatal opening and inversely correlated with the number of cryptostomata. The branching pattern of the annual stems ranged from short spur branches to well-developed, lateral axillary branches. The frequency of bifurcated blades increased significantly late in the growing season. Vesicle shape and size and pedicel length were temporally stable. Alated pedicels and mucronate vesicles occurred in low frequencies. The variability of the morphological features used to delineate species within the genus Sargassum on the tropical eastern coasts of the Americas is poorly understood.     

SEASONAL MODULE DYNAMICS IN SARGASSUM SUBREPANDUM (FUCALES,PHAEOPHYTA)1

Module dynamics of the fucoid alga SARGASSUM SUBREPANDUM (Forssk.) C. Agardh was studied in the southern Red Sea. Seasonal variation in thallus density and size was determined, and the initiation, growth, reproduction, and shedding of modules (primary laterals) were ascertained, using a tagging approach. Possible effects of different size‐related parameters on module initiation, growth, reproduction, and shedding were analyzed in the context of contradicting results for other macroalgae, in comparison with terrestrial plants. Thallus density varied little; most of the seasonal variation occurred at the modular level. A restricted period of new module formation early in the cooler season was followed by fast growth and reproduction. Massive shedding of modules occurred toward the end of the cooler season leading to strongly reduced biomass in summer. There was some evidence that high module numbers inhibited new module formation and enhanced the maximum module elongation rate (fastest‐growing module per thallus). On the other hand, elongation rates generally decreased, and apical tissue losses increased with increasing module length. This response was observed over a wide size range, suggesting grazing losses. There was no evidence of suppressed growth in small modules due to intraspecific competition. Elongation rates remained unaffected by reproductive status, indicating that there was no direct trade‐off between growth and reproduction. Module survivorship was independent of module number and size, but fertile modules were more persistent than vegetative ones. We conclude that module dynamics are determined by seasonal changes in the environment, size‐dependent processes, and interactions among the modules.     

EFFECT OF NUTRIENT LIMITATION ON FATTY ACID AND LIPID CONTENT OF MARINE MICROALGAE1

Phaeodactylum tricornutum and Chaetoceros sp. (Badllariophyceae), Isochrysis galbana (clone T-Iso) and Pavlova lutheri (Prymnesiophyceae), Nannochloris atomus (Chlorophyceae), Tetraselmis sp. (Prasinophyceae), and Gymnodinum sp. (Dinophyceae) were cultured at different extents of nutrient-limited growth: 50 and 5% of μ_max. The lipid content of the algae was in the range 8.3–29.5% of dry matter and was generally higher in the Prymnesiophyceae than in the Prasinophyceae and the Chlorophyceae. Increasing extent of phosphorus limitation resulted in increased lipid content in the Bacillariophyceae and Prymnesiophyceae and decreased lipid content in the green flagellates N. atomus and Tetraselmis sp. The fatty acid composition of the algae showed taxonomic conformity, especially for the Bacillariophyceae, where the major fatty adds were 14:0, 16:0, 16:1, and 20:5n-3. These fatty acids were dominant also in the Prymnesiophyceae together with 22:6n-3. An exception was I. galbana, in which 18:1 was the major monounsaturated fatty add and 20:5n-3 was absent. The fatty acids of N. atomus and Tetraselmis sp. varied somewhat, but 16:0, 16:1, 18:1, 18:3n-3, and 20:5n-3 were most abundant. Gymnodinum sp. contained mainly 16:0, 18:4n-3, 20: 5n-3, and 22:6n-3. An increased level of nutrient limitation (probably phosphorus) resulted in a higher relative content of 16:0 and 18:1 and a lower relative content of 18:4n-3, 20:5n-3, and 22:6n-3. The nutrient limitation probably reduced the synthesis of n-3 polyunsaturated fatty acids.     

TAXONOMIC REVISION OF SARGASSUM SPECIES (FUCALES,PHAEOPHYCEAE) FROM NEW CALEDONIA BASED ON MORPHOLOGICAL AND MOLECULAR ANALYSES1

Sargassum C. Agardh (1820) is a taxonomically difficult genus distributed worldwide and reported as the most species‐rich genus of the Fucales. It is especially abundant in the Pacific where decreasing species richness is reported to occur from west to east. New Caledonia has been recognized as one of the hotspots of Sargassum diversity; however, species lists available for this region are old and incomplete and have not yet been updated with regard to the latest taxonomic revisions published. This study aimed at revising Sargassum diversity in New Caledonia and to assess its geographic affinities with neighboring Pacific regions. We used combined morphological and DNA analyses on new collections and examined numerous type specimens. Although 45 taxa have been listed in the literature, most of them have been either transferred to synonymy since or misidentified, and in this study, only 12 taxa were recognized as occurring in New Caledonia. They belong to the subgenus Sargassum sect. Binderianae (Grunow) Mattio et Payri (2), sect. Ilicifoliae (J. Agardh) Mattio et Payri (2), sect. Polycystae Mattio et Payri. (1), sect. Sargassum (4), sect. Zygocarpicae (J. Agardh) Setch. (2), and subgenus Phyllotrichia (Aresh.) J. Agardh (1). New Caledonian Sargassum flora appeared as the second richest in the region after the Pacific coast of Australia, with which it has shown high similarity, and shared species with all neighboring regions. One species, S. turbinarioides Grunow, is considered as endemic to New Caledonia. The low genetic diversity detected among several polymorphic species belonging to sect. Sargassum is also discussed.     

温度条件对麦田土壤溶液养分浓度的影响

本文用实测资料分析了温度对麦田土壤溶液养分浓度的影响。研究表明,在农田土壤水分不亏缺的条件下,温度与麦田土壤溶液浓度呈正相关关系。随着太阳辐射增强,温度升高,土壤溶液中NO_3-N浓度增大,到14:00—15:00时,出现极大值。土壤溶液中钾浓度的高峰期基本是在中午温度高的时刻,低峰期在夜晚和午前10:00—11:00左右。10:00—11:00时的低值,可能与根系的同化吸收有关。土壤溶液养分浓度日较差大,光合面积增长快,营养生长旺盛。     

名古屋风景林凋落物和凋落叶养分含量季节动态的研究

对日本名古屋市的三个风景林－日本柳形（Cryptomeria japonica)林,日本米槠（Quercus cuspidata)林和常绿落叶阔叶混交林的凋落物和凋落叶养分含量的动态变化及养分贮量进行了研究。日本柳杉林、日本米槠林和常绿落叶阔叶混林的年凋落量分别为7309kg.hm^-2、5790kg.hm^－2和5325kg.hm^-2,日本柳杉林的主要凋落高峰发生在9月,次要凋落高峰发生在3月,而日本米槠林和常绿落叶阔叶混交林的凋落高峰分别发生在5月和11－12月。台风引起大量枝叶凋落。日本柳杉林、日本米槠林和常绿叶阔叶混交林凋落物的5种养分年贮量分别为224.22kg.hm^-2、119.33kg.hm^-2和133.21kg.hm^-2。凋落物养分中N、K和Ca的量大于P和Mg。凋落叶的养分量占养分年贮量的63．19％－79．06％。落叶树种凋落叶养分浓度的季节变化大于常绿树种。     

SELF‐THINNING AND SIZE INEQUALITY DYNAMICS IN A CLONAL SEAWEED (SARGASSUM LAPAZEANUM,PHAEOPHYCEAE)1

Fronds of clonal seaweeds with extensive holdfasts relative to frond size are known not to self‐thin during growth, even in crowded stands. We tested whether frond self‐thinning would occur for such a seaweed since these traits are more similar to those of unitary seaweeds, which do self‐thin in crowded conditions. We used Sargassum lapazeanum Setch. et N. L. Gardner (Fucales, Phaeophyceae) from the Pacific coast of Mexico, for which we first confirmed its clonal nature by performing a regeneration experiment in culture tanks. During the growth season (winter to late spring), S. lapazeanum stand biomass increased, while frond density and size inequality (Gini coefficient for frond biomass) decreased. These results indicate that self‐thinning occurred at the frond level. We propose a conceptual model for frond dynamics for clonal seaweeds in general. In stands of clonal species with small fronds and relatively extensive holdfasts (particularly when holdfasts are perennial), frond dynamics would be determined mostly by intraclonal regulation, which seems to prevent excessive crowding from occurring. Such species display a positive biomass–density relationship during the growth season. On the contrary, in stands of clonal species with large fronds relative to holdfast size, frond dynamics would be determined mostly by interactions among genets. For such species, self‐thinning may be detected at the frond level in crowded stands, resulting in a negative biomass–density relationship during growth.     

EFFECTS OF LIGHT INTENSITY AND TEMPERATURE ON CRYPTOMONAS OVATA (CRYPTOPHYCEAE) GROWTH AND NUTRIENT UPTAKE RATES1

Specific growth rate of Cryptomonas ovata var. palustris Pringsheim was measured in batch culture at 14 light-temperature combinations. Both the maximum growth rate (μ_m) and optimum light intensity (I_opt) fit an empirical function that increases exponentially with temperature up to an optimum (T_opt), then declines rapidly as temperature exceeds T_opt. Incorporation of these functions into Steele's growth equation gives a good estimate of specific growth rate over a wide range of temperature and light intensity. Rates of phosphate, ammonium and nitrate uptake were measured separately at 16 combinations of irradiance and temperature and following a spike addition of all starved cells initially took up nutrient at a rapid rate. This transitory surge was followed by a period of steady, substrate-saturated uptake that persisted until external nutrient concentration fell. Substrate-saturated NO₃^?-uptake proceeded at very slow rates in the dark and was stimulated by both increased temperature and irradiance; NH₄⁺-uptake apparently proceeded at a basal rate at 8 and l4 C and was also stimulated by increased temperature and irradiance. Rates of NH₄^?-uptake were much higher than NO₃^?-uptake at all light-temperature combinations. Below 20 C, PO₄^?3-uptake was more rapid in dark than in light, but was light enhanced at 26 C.     

ENCYSTMENT OF THE DINOFLAGELLATE GYRODINIUM UNCATENUM: TEMPERATURE AND NUTRIENT EFFECTS1

Sexual reproduction and encystment of the marine dinoflagellate Gyrodinium uncatenum Hulburt were induced in nitrogen and phosphorus-limited batch cultures. Sexuality did not occur under nutrient-replete conditions even when growth rate was reduced by non-optimal temperatures. Growth was optimal over a broader temperature range than encystment and virtually no cysts were produced at some low and high temperatures where growth occurred. Most cells initiated sexuality as intracellular pools of each limiting nutrient reached minimum or subsistence levels as much as four days after extracellular nutrients were exhausted. High nitrogen cell quotas during the phosphorus experiment indicate that sexuality was induced by a shortage of phosphorus and not by an indirect effect on nitrogen uptake. Total cyst yield corresponded to successful encystment of 9–13% of the motile populations, yet 60–85% of the plateau-phase motile cells were planozygotes (swimming zygotes formed from fusing gametes). Batch culture studies monitoring total cyst yield may thus seriously underestimate the extent of sexuality. More importantly, the number of cysts produced in a dinoflagellate population may be significantly reduced by environmental factors acting on the cells after sexual induction and fusion.     

FIELD AND CULTURE STUDIES OF A POPULATION OF ENDARACHNE BINGHAMIAE (PHAEOPHYTA) FROM SOUTHERN CALIFORNIA1

Abundances of the erect, blade phase of Endarachne binghamiae J. Ag. (Scytosiphonales, Phaeophyta) varied seasonally at a southern California rocky intertidal site. Blade cover and density were much greater in the fall through early spring; blades were mostly absent from quadrats during the summer. Blade abundances were negatively correlated with both seasonal variations in seawater temperature and photoperiod. Laboratory culture studies failed to provide evidence for sexual reproduction. The life history appears to be of the “direct” type with plurangia-produced zooids germinating into crustose disks. Most disks developed erect blade clusters under spring/fall (17° C) and winter (13° C) temperatures over the range of natural photoperiods employed (14:10, 12:12, 10:14 h LD). In contrast, cultures held under the summer temperature (21° C) produced almost entirely crustose growths regardless of photoperiod. Similar results were obtained for cultures grown at 100 and 200 μE · m^?2· s^?1. E. binghamiae blades were fertile throughout the year and produced viable zooids indicating that reproductive seasonality did not influence the seasonal pattern of blade abundance. Culture and field studies suggest that the initiation of new erect blade clusters from crustose disks is confined to the cooler months of the year (winter and spring). The summer reduction or absence of E. binghamiae blades appears to be due to increased mortality rates and temperature constraints on the development of new erect bladed thalli. Hypothetical causes of mortality are desiccation stress, sand burial, increased grazing activity and a genetically-based short life span.     

INTERACTING EFFECTS OF LIGHT AND NUTRIENT LIMITATION ON THE GROWTH RATE OF SYNECHOCOCCUS LINEARIS (CYANOPHYCEAE)1

The blue-green alga Synechococcus linearis (Naeg.) Kom. was grown in P- and N-limited chemostats over a range of potentially limiting irradiances in order to determine the combined effects of light and nutrient limitation on some aspects of the composition and metabolism of this alga. Over a narrow range of low irradiances, simultaneous limitation of growth rate by light and either N or P was shown. This simultaneous limitation of growth rate by a nutrient and a physical factor can be explained by the ability of an increased supply of one to compensate in part for a decreased supply of the other. At all irradiances, the internal concentration of the limiting nutrient increased with increasing dilution rate, and the results could be fitted to the Droop relationship. With decreasing irradiance, the internal concentration of the limiting nutrient increased. There appeared to be little or no effect of light on the minimum internal concentration of P but that of N increased with decreasing light. Both chlorophyll a and biliprotein per unit particulate C increased with increasing dilution rate and decreasing irradiance. The critical N/P ratio increased with decreasing light as the N requirement of N-limited cells increased faster than did the P requirement of P-limited cells. The composition of exponentially growing cells in complete medium varied much less with light. Neither dilution rate nor irradiance during growth had a great effect on saturated rates of P or N uptake or alkaline phosphatase activity. Calculated assimilation ratios increased with light and dilution rate. The role of the flexibility of nutrient composition in adaptation to adverse conditions and the implications of the results for the use of physiological indicators of nutrient status are discussed.     

VARIABILITY IN CELL SIZE,NUTRIENT DEPLETION,AND GROWTH RATES OF THE SOUTHERN OCEAN DIATOM FRAGILARIOPSIS KERGUELENSIS (BACILLARIOPHYCEAE) AFTER PROLONGED IRON LIMITATION1

Diatoms are the main primary producers in the Southern Ocean, governing the major nutrient cycles. Fragilariopsis kerguelensis (O’Meara) Hust. is the most abundant diatom species in the Southern Ocean and its paleo‐oceanographic record is frequently used to reconstruct the past position and nutrient characteristics of the Antarctic polar front. Here we report on the responses of F. kerguelensis on prolonged exposure to a range of iron concentrations, allowing a characterization of morphological and nutrient‐depletion changes in relation to iron status. Under iron limitation, F. kerguelensis grew slower, cells became smaller, chains became shorter, and the nutrient‐depletion ratios changed. Prolonged exposure to iron limitation caused F. kerguelensis to decrease its surface area and volume 2‐fold, and to increase its surface‐to‐volume ratio by 25%. With the decrease in growth rates, silicon (Si) and phosphorus (P) depletion per cell remained fairly constant, but when normalized per surface area (Si) or per cell volume (P), depletion increased. In contrast, nitrogen (N) depletion per cell decreased significantly together with the decrease in growth rates but was constant when normalized per cell volume. The different response in Si, P, and N depletion resulted in changes in the nutrient‐depletion ratios, most notably in the Si:N ratio, which significantly increased, and in the N:P ratio, which significantly decreased with decreasing growth rates. It is concluded that under iron limitation, variation in cell size and/or nutrient depletion ultimately can cause changes in oceanic biogeochemical nutrient cycles. It enables the use of cell size of F. kerguelensis as a paleo‐oceanographic proxy.     

南亚和东南亚巨蜥居群的种间亲缘和越南─新种描述

１９９２年１１月１５日从云南省河口县城自由市场的一位越南人手中买得一雌性巨蜥,经鉴定为一新种,定名为越南巨蜥Ｖａｒａｎｕｓｖｉｅｔｎａｍｅｎｓｉｓ。鉴别特征：新种背部鳞片光滑,仅在后半部插有极少的起棱鳞片,不同于Ｖ．ｎｅｂｕｌｏｓｕｓ（Ｂｏｕｌｅｎｇｅｒ,１８８５,１８９０;Ｔａｙｌｏｒ,１９６３）;新种不同于Ｖ．ｓａｌｖａｔｏｒ在于其背部没有眼斑状横斑带（ｏｃｅｌｌｉｍａｒｋｓ）（Ｇｕｅｎｔｈｅｒ,１８６４;Ｈａｒｒｉｓｏｎ等,１９５７;Ｐｏｐｅ,１９３５）;不同于Ｖ．ｉｒｒａｗａｒｄｉｃｕｓ（Ｙａｎｇ等,１９８７）,Ｖ．ｇｒｉｓｅｕｓ和Ｖ．ｍｏｎｉｔｏｒ（Ｓｍｉｔｈ,１９３５）在于有６─７个横向扩大的眼上鳞。文中运用了１５个外部性状对产于南亚,东南亚大陆及岛屿共９个种（含新种）的种间亲缘关系进行了研究,结果认为,种间亲缘关系的亲疏与分布地区相距的远近成正相关。     

SEASONAL MODULE DYNAMICS OF TURBINARIA TRIQUETRA (FUCALES,PHAEOPHYCEAE) IN THE SOUTHERN RED SEA1

Module dynamics in the fucoid alga Turbinaria triquetra (J. Agardh) Kützing were studied on a shallow reef flat in the southern Red Sea. Seasonal patterns in thallus density and size were determined, and the initiation, growth, reproduction, and shedding of modules were studied using a tagging approach. The effects of module density and module/thallus size on module initiation, growth, reproduction, and shedding were analyzed, and the occurrence of intraspecific competition among modules was examined. Seasonal variation occurred mainly at the modular level. There was a restricted period of new module formation in the cooler season, followed by fast growth and reproduction, massive shedding of modules from the end of the cooler season onward, and strongly reduced biomass in summer. There was no evidence of suppressed growth in small modules due to intraspecific competition. Module density and thallus/module size had opposite effects on elongation rates. High module densities enhanced maximum elongation rates (fastest‐growing module per thallus), resulting in longer thalli. On the other hand, elongation rates decreased and tissue loss increased with increasing module length. Reproduction had no clear effect on elongation rates, indicating that there was no direct trade‐off between reproduction and growth. The apparent size‐dependence of reproduction was due to delayed fertility in young modules. Module initiation and shedding were independent of module density. Shedding was also independent of module size and reproductive status. We conclude that seasonal changes in the environment affect module initiation, growth, reproduction, and shedding, whereas density and size‐dependent processes mainly affect growth rates.