BLUE-GREEN ALGAL MATS IN A SMALL STREAM1

Bedrock erosional features in a small stream (Little Schultz Creek, Bibb County, Alabama) created a variety of habitats for epilithic growth. One suck habitat was illustrated by the occurrence of small falls (<0.3 m) in the main channel of the stream and blue-green algal mats associated with them. The cohesive, laminar algal mats were found at 15 such sites along a 250-m reach of the stream. The primary mat matrix consisted of the blue-green alga Oscillatoria submembranacea Ardissone and Strafforella. The uppermost portion of each mat consisted of a thin (<1 mm thick) green layer of biologically active filaments. The lower layers were thicker (up to 2 cm thick) and consisted of brown laminae of Oscillatoria filaments, and associated sediments. In addition, numerous diatoms mere associated with the mat surface. Some were loosely attached (e.g. Achnanthes); others (Cymbella tumida (Bréb.) V. H.) were stalked. These mats were present throughout the year and showed a bimodal annual distribution with maxima hi February and July. In February, total mat coverage was higher than in July. This winter maximum may have been related to a mode of growth dependent upon sedimentation from storm events and subsequent upward growth of the alga. Mat primary productivity on an areal basis (432 mg C · m^?2· d^?1 in March and 907 mg C · M^?2· d^?1 in April) was 2–12 times the maxima measured on epizoic and cobbles surfaces and other bedrock surfaces in the same stream. The limited areal coverage of the mats, when compared to other surfaces available for algal colonization, made them less important than other epilithic and epizoic surfaces in terms of total primary production in this stream reach. However, we propose that the combination of their unique structure and high primary productivity may make these algal mats sites of high algal and bacterial metabolic activity, which may include anaerobic processes in midchannel, where such activity would not be expected to occur.     

STRUCTURE AND FUNCTION OF BENTHIC ALGAL COMMUNITIES IN AN EXTREMELY ACID RIVER1

The composition of algal species and pigments and the structural and functional characteristics of the algal community were investigated in an acid stream of southwestern Spain, the Río Tinto. The algal community had low diversity and showed few seasonal differences. It was mainly made up of Klebsormidium flaccidum Kütz. (Silva, Mattox & Blackwell) that produced long greenish or purplish filaments, Pinnularia acoricola Hust. (producing brown patches) and Euglena mutabilis Schmitz. The algal filaments made up a consistent biofilm that also included fungal hyphae, iron bacterial sheaths, diatoms, and mineral particles. HPLC analyses on Río Tinto samples showed that undegraded chl accounted for 67% of the total chl in the filamentous patches but were a minority in the brown patch (2.6%). The brown patch had a concentration of carotenoids eight times lower than that observed in the green patch. When chl concentrations were weighted for the proportion of the different patches on the streambed, undegraded chl a accounted for 89.2 mg chl a·m ^{? 2} of stream surface area (5.4 g C·m ^{? 2}). This high algal biomass was supported by relatively high nutrient concentrations and by a high phosphatase activity (V_max = 137.7 nmol methylumbelliferyl substrate·cm ^{? 2}·h ^{? 1} 1 Received 15 July 2002. Accepted 17 February 2003. , K_m = 0.0045 μM). The remarkable algal biomass in Río Tinto potentially contributed to the bacterial–fungal community and to the macroinvertebrate community and emphasizes the role that the algae may have in the organic matter cycling and energy flow in extreme systems dominated by heterotrophic microorganisms.     

ALGAL RESPONSE TO NUTRIENT ENRICHMENT IN FORESTED OLIGOTROPHIC STREAM1

Nutrient input in streams alters the density and species composition of attached algal communities in open systems. However, in forested streams, the light reaching the streambed (rather than the local nutrient levels) may limit the growth of these communities. A nutrient‐enrichment experiment in a forested oligotrophic stream was performed to test the hypothesis that nutrient addition has only minor effects on the community composition of attached algae and cyanobacteria under light limitation. Moderate nutrient addition consisted of increasing basal phosphorus (P) concentrations 3‐fold and basal nitrogen (N) concentrations 2‐fold. Two upstream control reaches were compared to a downstream reach before and after nutrient addition. Nutrients were added continuously to the downstream reach for 1 year. Algal biofilms growing on ceramic tiles were sampled and identified for more than a year before nutrient addition to 12 months after. Diatoms were the most abundant taxonomic group in the three stream reaches. Nutrient enrichment caused significant variations in the composition of the diatom community. While some taxa showed significant decreases (e.g., Achnanthes minutissima, Gomphonema angustum), increases for other taxa (such as Rhoicosphenia abbreviata and Amphora ovalis) were detected in the enriched reach (for taxonomic authors, see Table 2 ). Epiphytic and adnate taxa of large size were enhanced, particularly during periods of favorable growth conditions (spring). Nutrients also caused a change in the algal chl a, which increased from 0.5–5.8 to 2.1–10.7 μg chl · cm^?2. Our results indicate that in oligotrophic forested streams, long‐term nutrient addition has significant effects on the algal biomass and community composition, which are detectable despite the low light availability caused by the tree canopy. Low light availability moderates but does not detain the long‐term tendency toward a nutrient‐tolerant community. Furthermore, the effects of nutrient addition on the algal community occur in spite of seasonal variations in light, water flow, and water chemical characteristics, which may confound the observations.

Table 2. Percent abundances of the most frequent taxa in three reaches of the Fuirosos stream. U1 and U2 untreated; E, enriched both in the periods before (bef) and after (aft) the enrichment of the E reach. Acronyms identifying the taxa are indicated.

FATTY ACID DISTRIBUTION AMONG SOME RED ALGAL MACROPHYTES1

Macrophytic members of the Rhodophyta, which were grown under controlled conditions, were analyzed for their fatty acid distribution. Significant differences were found between some species of the Gelidiales and Gracilariales. Two dominant polyunsaturated fatty acids of the 20 carbon chain group, 20:4ω6 and 20:5ω3, were found in all the Gelidiales species, whereas only 20:4ω6 was found in the Gracilariales species. An inverse relationship between the content of these two polyunsaturated fatty acids in Gelidiales species and among the two groups of species are reported and discussed. All other fatty acid characteristics were more or less similar in these two orders. We cannot draw any solid conclusion about the relationship between Gracilariopsis cf. lemaneiformis (formerly Gracilaria lemaneiformis) and the genus Gracilaria, since our results (the existence of 20:4ω6 and 20:5ω3 in Gracilariopsis) contradict results found by other researchers. The diverse growth conditions of photon flux density and temperature caused some differences in the distribution of the fatty acids in each species. These differences could not explain the different results in similar species reported in the literature.     

ALCIAN BLUE: A QUANTITATIVE AQUEOUS ASSAY FOR ALGAL ACID AND SULFATED POLYSACCHARIDES1

Alcian Blue, a cationic copper phthalocyanine dye, complexes with the anionic carboxyl and half-ester sulfate groups of acidic algal polysaccharide in aqueous solution to form an insoluble precipitate. The quantity of dye removed from solution is proportional to the quantity of polyanion in solution, and this principle forms the basis for the quantitative determination of acid and/or sulfated algal polysaccharides. The assay is linear between 0 and 100 μg/ml agar, alginic acid, carrageenan, pectin and Porphyridium aerugineum Geit. polysaccharide. In addition, the technique is used to determine the anion density of acid polysaccharides on a molar or weight equivalency basis.     

ALGAL ASSEMBLAGES IN ANTARCTIC PACK ICE AND IN ICE-EDGE PLANKTON1

A significant amount of the primary production in the Southern Ocean and other ice-covered oceans takes place in localized ice edge plankton blooms. The dynamics of these blooms appear to be closely related to seasonal melting of sea ice. Algal cells released from the ice are a possible source of ice edge planktonic assemblages, but evidence for this “seeding” has been equivocal. We compared algal assemblages in ice and water in the Weddell Sea during the austral spring of 1983 at a receding ice edge with a well-developed ice edge bloom. The high degree of similarity between ice and water column assemblages, the spatial and temporal patterns in the distribution and abundances of species, and preliminary evidence for the viability and growth of ice-associated species provide evidence for seeding from sea ice of some species in Antarctica.     

ALGAL COMPETITION IN AN EPILITHIC RIVER FLORA1

Field and laboratory procedures demonstrate that the effluent from the Willimantic, Connecticut, sewage treatment plant changes the numerical composition of the dominant epilithic algae in the Shetucket River. This effect is due to the effluent altering the competitive balance between chlorella sp. and Achnanthes deflexa Reim. The chlorella completely dominates highly polluted stretches of the river, and shares dominance with A. deflexa in other areas. The degree of river pollution can be estimated by enumerating the natural standing crops of these 2 algae. A 2-membered assay utilizing these organisms is a sensitive laboratory pollution monitor and a useful predictive tool. Dominant stands of these epilithic species develop in polluted and unpolluted zones in this river due to competition for the limited area on the cobbles.     

BENTHIC DIATOM DISTRIBUTION IN A PENNSYLVANIA STREAM: ROLE OF pH AND NUTRIENTS1

Buffalo Creek is in a forested watershed in eastern Pennsylvania and is relatively acid in upstream reaches (pH～6), becoming alkaline downstream (pH～8). Temperature, nitrogen (NO₃-N) and phosphorus (O-PO₄) increase significantly downstream whereas N/P declines. Nutrient-diffusing substrata were deployed in triplicate at an upstream and downstream site. Six treatments included two concentrations of nitrate, two concentrations of phosphate, nitrogen + phosphate, and a control. Substrata were collected after 18 days, scraped and analyzed for accrual of chlorophyll a and algal community structure. Chlorophyll a and algal biovolume were greatest downstream across all nutrient treatments. At the community level, accrual appeared to be limited by phosphorus at upstream sites. Downstream accrual also may have been phosphorus-limited, but the results were equivocal. Benthic algae on all treatments at both sites were ～96% diatoms. Minimal overlap in species composition was observed between upstream and downstream sites. Of the 75 species of diatoms encountered in the study, 58 species did not occur at the upstream site and 10 species did not occur at the downstream site. The upstream site was depauperate in species and dominated by Eunotia exigua (Bréb. ex Kütz.) Rabh., which showed a positive response to phosphorus and accounted for over 50% of the biomass across treatments. The downstream site showed a four-fold increase in species richness. Communities at this site contained some species that appeared to be phosphorus-limited, e.g. Melosira varians Ag., and others that seemed to be nitrogen-limited, e.g. Diatoma vulgare Bory and Navicula seminulum Grun. We conclude that extreme conditions upstream (low pH, high N/P) result in a species-poor community dominated by acidophilous phosphorus-limited diatoms. Increases in downstream nutrients and pH result in a relatively rich and diverse community.     

ALGAL SYMBIONT OF A SOFT CORAL1

The algal symbiont of the soft coral Sarcothelia edmondsoni (Verrill), is identified as the dinoflagellate Gymnodinium microadriaticum (Freudenthal) Taylor on the basis of its cytology apparent in electron micrographs. The character of the nucleus, peripheral lobed chloroplast with a vase-shaped pyrenoid body and other inclusions form the basis for identification.     

INFECTION,GROWTH, AND COMMUNITY-LEVEL CONSEQUENCES OF A DIATOM PATHOGEN IN A SONORAN DESERT STREAM1

We describe effect of a pathogen that spread through a dense, rapidly growing, benthic diatom community during two infection periods (February and mid-April 1991) in Sycamore Creek, Arizona. Infected areas appeared as gray rings within a matrix of healthy diatom growth and spread rapidly, eventually covering all benthic substrata and causing algal sloughing (within 2 wk in February and 1 wk in April). Examination of algal material with transmission electron microscopy revealed the presence of invasive bacteria within diatom cells from infected areas, suggesting a pathogenic bacterium as the most probable cause of this phenomenon. Infected area supported lower chlorophyll a concentrations and contained higher percentages of diatom cells with fragmented or reduced chloroplasts than uninfected areas. Spread of the pathogen appeared to be linked most strongly with diatom densities. The infection spread most rapidly in April, when cell densities were highest, and decimated all diatom species populations. The February infection was more species-specific in its action, affecting large motile and rosetteforming taxa more strongly than small, adnate diatoms. This latter group likely resided at the base of communities and may have been buffered from pathogen transfer by mucilage and/or dentrital particles. Consequently, relative abundance of small, adnate diatom taxa increased in algal communities as a result of the February infection. Pathogen-induced alteration of diatom species composition and abundance should influence primary production in this ecosystem and affect the dynamics of organisms that exploit algae as a resource.     

ESTABLISHMENT,PERSISTENCE AND DOMINANCE OF CORALLINA (RHODOPHYTA) IN ALGAL TURF1

The dominance of Corallina thalli in an intertidal algal assemblage was examined by a series of algal removal experiments to test the hypothesis that other tam are competitively excluded from rock substrate. An alternate explanation, that environmental factors seasonally filter out taxa leaving Corallina as the only alga adapted for year to year survival, was considered. Development of vegetation on patches of naturally exposed bare rock was monitored and compared with manipulated surfaces. Thalli of several species were selectively removed from exposed surfaces and intact turf;. changes in tam occupying primary substrate were recorded over more than three years. No significant differences in mean percent cover for Corallina, Lithothrix, bare rock, or algal crusts were found among treatments. Except for initial growth of colonizing species, abundances of other species dad not increase in the absence of Corallina. Large amounts of rock remained bare or intermittently covered by transient populations of short-lived algae. Data from single quad-rats, where individual clumps of Lithothrix were followed from month to month, indicated that the continued presence of this co-occurring and often abundant species depended on turnover of short-lived thalli rather than persistence of the same clumps. No interactions were found among the several categories of species that appeared after rock substrate was cleared. Most species were the same ones that grew, epiphytically in intact turf at the same time. In control quadrats Corallina maintained 59-95% cover while slowly increasing on surfaces earlier exposed. I predict that Corallina species will regain their dominance in the absence of competitors for primary substrate if the slowly spreading basal crusts remain undisturbed. Morphological and life history characteristics are identified that adapt Corallina to its dominant role in this habitat.     

伤胁迫对蚕豆叶片中茉莉酸分布的影响

在植物应对伤害等环境刺激的反应中,已知茉莉酸(JA)作为一种重要的信号分子在植物体内长距离运输,但目前对JA的细胞和亚细胞定位知之甚少。本研究用免疫荧光显微镜技术和免疫胶体金电镜技术证明茉莉酸分布在蚕豆叶片叶肉细胞的叶绿体、表皮细胞的细胞壁、保卫细胞的细胞壁、细胞质、叶绿体和细胞核上。其中保卫细胞的叶绿体和细胞核是JA分布的主要场所。叶片的局部灼伤可提高JA在质外体和气孔保卫细胞中的水平。由此推测,伤胁迫下JA分配的改变可能与植物体防御反应密切相关,并参与了对气孔运动的调控。     

COMPARISON OF IN SITU PHOTOSYNTHETIC ACTIVITY OF EPIPHYTIC,EPIPELIC AND PLANKTONIC ALGAL COMMUNITIES IN AN OLIGOTROPHIC LAKE,SOUTHERN FINLAND1

The photosynthetic activity of different algal communities at the outer edge of an Equisetum fluviatile L. stand in an oligotrophic lake (Pääjärvi, in southern Finland) was investigated. Production by the algal communities was measured simultaneously using a modified ¹⁴C-method, and the results were related to the volume of algae and the available irradiance. The relative production rate (P/B quotient) of phytoplankton was ca. 3 × that of epiphyton and ca. 20 × that of epipelon. Epiphyton productivity remained almost constant although the algal volume varied greatly, suggesting that the surface layer of the algal community was mainly responsible for the photosynthetic activity. In the littoral area (at 1 m depth) primary production/m² of lake surface by phytoplankton, epiphyton and epipelon was similar but in the littoriprofundal area (2–4 m) phytoplankton production was twice that of epipelon. Primary productivity of epiphyton and epipelon/m² of substratum was about equal to phytoplankton productivity/m³ of water at the same irradiance. This relation provided a means of estimating the relative contributions of the different algal communities to the total algal production in the lake.     

ALGAL COMMUNITIES OF SPRINGS AND STREAMS IN THE MT. ST. HELENS REGION,WASHINGTON, U.S.A. FOLLOWING THE MAY 1980 ERUPTION1

Mt. St. Helens, a volcanic peak in the Cascade Range in southern Washington erupted violently on May 18, 1980, causing enormous damage to both terrestrial and aquatic ecosystems. The initial explosion evaporated, scoured or buried all springs and streams in the blast impact area. Ash fall and erosion from defoliated hillsides subsequently filled most of the lotic habitats with organic debris and volcanic ash. Recolonization of springs and streams by algae occurred quickly in areas where erosion through the ash progressed down to bedrock. Within 15 months or less of the eruption, algal communities were established throughout the blast impact area. However, as a result of the initial and continued disturbance these communities remained in an early successional stage. Floral assemblages were highly variable except that they were composed mostly of diatoms, with Achnanthes minutissima dominating most lotic sites. Springs showed the most rapid development toward stable floras.     

A GRADIENT IN BENTHIC INTERTIDAL ALGAL ASSEMBLAGES ALONG THE SOUTHERN CALIFORNIA COAST1

Based on an analysis floristic data, a gradient appears to exist in the composition of intertidal algae along the 450 km of southern California coastline immediately south of Point Conception. Reciprocal averaging ordination of the algal flora at 51 sites in this area suggests that the gradient is not strictly latitudinal. Variation from a latitudinal gradient occurs ca. 60-80 km south of Point Conception. An ordination of frequently occurring species indicated that compositional changes are substantial when sites at the extreme north and south are compared, but that the changes are gradual and continuous. Possible explanations for the gradient are discussed, and these include: sea temperature, upwelling, sand movement, human disturbance (i.e., pollution, trampling), and wave action.     

维生素A酸在东方蝾螈肢体再生过程中的出现和分布~*(简报)

有尾两栖类(蝾螈和美西螈)是脊椎功物中仅有的具备再生出失去肢体能力的动物。维生素A 酸(Retinoic Acid,简称RA)存在于鸡的发育中的肢芽,局部使用可模拟极化区的作用,因而被认为可能是形态发生素。作为     

氮磷对污水净化中藻类群落结构的影响

在室内模拟生物净化槽中比较研究了氮,磷对污水净化藻类群落结构和污水净化效果的影响。其结果ＴＮ／ＴＰ＝４４．７／７．０１ｍｇ／Ｌ组,藻类种类多样性最高,净生产力最高,污水净化效果也最佳。     

LINKING BENTHIC ALGAL BIOMASS TO STREAM SUBSTRATUM TOPOGRAPHY1

The physical properties of substrata significantly influence benthic algal development. We explored the relationships among substratum surface texture and orientation with epilithic microphytobenthic biomass accumulation at the whole‐substratum and micrometer scales. Unglazed clay tiles set at three orientations (horizontal, vertical, and 45°), and six substrata of varying surface roughness were deployed in a prairie stream for 3 weeks. Substrata were analyzed for loosely attached, adnate, and total benthic algal biomass as chl a, and confocal laser scanning microscopy was used to measure substrata microtopography (i.e., roughness, microscale slope angles, and three‐dimensional surface area). At the whole‐substratum level, vertical substrata collected significantly (P < 0.05) less algal biomass, averaging 34% and 36% less than horizontal and 45° substrata, respectively. Benthic algal biomass was also significantly less on smoother surfaces; glass averaged 29% less biomass than stream rocks. At the microscale level, benthic algal biomass was the greatest at intermediate values, peaking at a mean roughness of approximately 17 μm, a mean microscale slope of 50°, and a projected/areal surface area ratio of 2:1. The proportion of adnate algae increased with surface roughness (26% and 67% for glass and brick, respectively), suggesting that substratum type changes the efficiency of algal removal by brushing. Individual substrata and microsubstrata characteristics can have a strong effect on benthic algae development and potentially affect reach scale algal variability as mediated by geomorphology.     

HIGH POLYUNSATURATED FATTY ACID LEVELS IN TWO SUBTROPICAL MACROALGAE,CLADOSIPHON OKAMURANUS AND CAULERPA LENTILLIFERA1

The lipid and fatty acid compositions in two edible subtropical algae (the brown alga Cladosiphon okamuranus Tokida and the green alga Caulerpa lentillifera J. Agardh) were determined to clarify their lipid characteristics and nutritional values. Glycolipids and phospholipids were the major lipid classes, with significant levels of triacylglycerols. Polyunsaturated fatty acids (PUFA) were the major fatty acids of both algae. The lipid class composition and major fatty acids were similar in both the algal species, irrespective of wild and cultured specimens. Typical n‐6 PUFA, such as 18:2n‐6 (linoleic acid) and 20:4n‐6 (arachidonic acid), occurred in characteristically high levels in both of the algae. High levels of n‐3 PUFA were measured in all lipid classes of both species without 22:6n‐3 (docosahexaenoic acid), 18:3n‐3, 18:4n‐3, and 20:5n‐3 (eicosapentaenoic acid) for Cl. okamuranus; and 16:3n‐3, 18:3n‐3, and 20:5n‐3 for Ca. lentillifera. The finding suggests that the green algal species, which mainly biosynthesizes short‐chain (C₁₆ and C₁₈) PUFA, differs from that of the brown alga, which is capable of biosynthesizing high 20:5n‐3 levels. The PUFA levels in glycolipids of the two algal species comprised up to 60%, even though they are subtropical marine species. High n‐6 PUFA levels in the algal lipids probably influence the significant levels of n‐6 PUFA in herbivorous fishes, because the n‐6 PUFA levels in marine fish lipids are generally undetectable or negligible.     

PHYSIOLOGICAL ECOLOGY OF NITROGEN FIXING BLUE-GREEN ALGAL CRUSTS IN THE UPPER-SUBALPINE LIFE ZONE1

Blue-green algal (cyanobacterial) crusts composed of nitrogen fixing Nostoc commune Voucher ex Born. et Flah. and Tolypothrix conglutinata var. colorata Ghose were studied in the upper-subalpine life zone, Mission Mountain Wilderness, Montana. Rates of ethylene production were highest in the submerged shoreline crusts, lower for exposed crusts pioneering rocky shorelines and lowest in the Carex meadow. Nitrogenase activity (acetylene reduction technique) was constant between 200–285% crust moisture content (wet/dry weight) and then rapidly declined to 0 between 200–140%. Optimal temperatures for ethylene production by illuminated cells was between 20–30° C for T. conglutinata, 20° C for N. commune and about 25° C in darkness for both species. Nitrogenase activity by T. conglutinata in culture was unaffected by repeated freeze-thaw treatments whereas N. commune was severely inhibited. In contrast, N₂-ase activity of these two species in an intact crust was unaffected by repeated freeze-thaw treatments. Application of nitrogen-free growth medium to intact crusts increased nitrogenase activity by 3.7 times implying that these were mineral deficient under field conditions. Photosynthesis was light saturated at 125 μmol-m^?2.s^?1 whereas nitrogenase activity was light independent for cells with carbohydrate reserves. When carbohydrate reserves were reduced by 8 h incubation in darkness, between 1–3 h of illumination were required to restore nitrogenase activity to 80% of the maximum rate. Biochemical pathway inhibitor studies employing DCMU, MFA, and CCCP showed that oxidative metabolism was the source of reductant for acetylene reduction. Tetrazolium precipitation in heterocysts paralleled acetylene reduction activity in the inhibitor treated cells.