PATTERNS OF ALGAL SUCCESSION IN A PERTURBATED MARINE INTERTIDAL COMMUNITY1

Patterns of algal succession for a sewage-polluted and an unpolluted habitat near Wilson Cove, San Clemente Island, California, were studied from December 1974 to June 1977. Resident populations were analyzed for 56 fully denuded and 34 undisturbed control quadrats during 11 assessment periods. The denuded quadrats in the perturbated (polluted) habitat showed recovery within 1.0 mo as determined by cover, percent similarity and species diversity comparisons with control plots. The short recovery times of the algal populations dominating the perturbated habitat indicate that these species maintain relatively constant overall abundances due to their potential for rapid recruitment and growth. Denuded quadrats in the unpolluted habitat did not show recovery even after 30.0 mo. These quadrats were dominated during the first 1.3 mo by algae characteristic of the perturbated area, including filamentous Ectocarpaceae, colonial diatoms and bluegreen algae. Petalonia fascia (Müll.) Kuntze (1.3–3.0 mo), and Scytosiphon lomentaria (Lyngb.)J. Ag. and Colpomenia sinuosa (Roth) Derb. & Sol. (1.3–5.0 mo) were abundant shortly following plot denudation and provided thick growths that may have excluded other algae. The similarity between the species occupying the sterilized plots during the first few months and those that provide the majority of cover in the perturbated area supports the hypothesis that the dominant algae of the upper and midintertidal regions of this habitat consist largely of early successional or opportunistic species with high capacities for growth and reproduction. Additionally, these experiments suggest that algal populations described for other perturbated epilithic systems also represent resilient subclimax associations.     

ADAPTATION OF STYROFOAM SUBSTRATE TO BENTHIC ALGAL PRODUCTIVITY STUDIES IN LAKE TAHOE,CALIFORNIA-NEVADA1

A routine sampling technique has been developed using artificial styrofoam substrate to estimate benthic algal productivity in the littoral zone of lakes. Estimation of maximum carbon fixed in Lake Tahoe ranged from 11.1 mg C·m^?2· day^?1 at 0.5 m to 17.1 mg C·m^?2· day^?1 at 1.0 m. Estimates were made for communities composed of both diatom and green algal populations in water between 0.5 and 3.0 m. Maximum productivity occurred between 1–2 m. The technique developed can give comparable estimates of productivity if adequate replication is undertaken to decrease problems associated with periphytic heterogeneity.     

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.     

PATTERNS OF INTERSPECIFIC INTERACTIONS IN THE ULVA-DOMINATED INTERTIDAL COMMUNITY IN A SOUTHERN COAST OF KOREA

The reproductive success of marine species with external fertilization depends on environmental conditions during gamete release. There is special interest presently in whether water motion causes sperm limitation under natural conditions. We investigated gamete release of Fucus vesiculosus from an exposed shore to ascertain: 1) when gametes are released during the tidal cycle, 2) when fertilization occurs, and 3) what the natural sperm:egg ratios are. Water samples were collected and concentrated over five minutes every half hour off Pemaquid Point, ME from three replicate sites within each of two locations using a pump-filter device. Immunofluorescence microscopy revealed that gamete release occurred only on the two calmest spring tides. Sperm became present in the water column at the same time as oogonia (30 min⁻¹ h prior to high tide [HT]) and reached peak concentration at exactly HT. The sperm:egg ratio was 76:1 on 8 Oct 1999 and 21:1 on 8 Nov 1999 at exactly 30 min prior to HT and dropped sharply after HT. Gametes continued to be collected for several hours after HT but analysis of pronuclear position in aceto-iron-hematoxylin stained eggs revealed that all fertilization occurred at approximately HT. We modelled the total number of days when reproduction was possible using these results and wind and wave data from the National Data Buoy Center. Our research provides evidence that gamete release by F. vesiculosus occurs at slack HT on calm days and that sperm are not a limiting factor in fertilization for this species.     

PATTERNS OF INTERSPECIFIC INTERACTIONS IN THE ULVA‐DOMINATED INTERTIDAL COMMUNITY IN A SOUTHERN COAST OF KOREA

The reproductive success of marine species with external fertilization depends on environmental conditions during gamete release. There is special interest presently in whether water motion causes sperm limitation under natural conditions. We investigated gamete release of Fucus vesiculosus from an exposed shore to ascertain: 1) when gametes are released during the tidal cycle, 2) when fertilization occurs, and 3) what the natural sperm:egg ratios are. Water samples were collected and concentrated over five minutes every half hour off Pemaquid Point, ME from three replicate sites within each of two locations using a pump‐filter device. Immunofluorescence microscopy revealed that gamete release occurred only on the two calmest spring tides. Sperm became present in the water column at the same time as oogonia (30 min^?1 h prior to high tide [HT]) and reached peak concentration at exactly HT. The sperm:egg ratio was 76:1 on 8 Oct 1999 and 21:1 on 8 Nov 1999 at exactly 30 min prior to HT and dropped sharply after HT. Gametes continued to be collected for several hours after HT but analysis of pronuclear position in aceto‐iron‐hematoxylin stained eggs revealed that all fertilization occurred at approximately HT. We modelled the total number of days when reproduction was possible using these results and wind and wave data from the National Data Buoy Center. Our research provides evidence that gamete release by F. vesiculosus occurs at slack HT on calm days and that sperm are not a limiting factor in fertilization for this species.     

MODELING THE ANNUAL PRODUCTION OF INTERTIDAL BENTHIC MICROALGAE IN ESTUARINE ECOSYSTEMS1

The purpose of this study was to develop and validate a habitat-specific production simulation model to quantify annual benthic microalgal production in North Inlet estuary, South Carolina. Using hourly measurements of incident irradiance during 1990–1991 as the forcing function, the simulation model was used to obtain hourly estimates of areal benthic microalgal gross primary production in five habitat types. The model, which was validated using actual measurements of production, showed good (r²= 0.63, P < 0.001) agreement between observed and predicted production in the short Spartina alterniflora Loisel zone habitats showed the highest mean hourly production (61.1 mg C m^?2 h^?1) while intertidal mudflats had the maximum hourly rate (166.9 mg C m^?2 h^?1). Daily production was highly variable, primarily due to daily fluctuations in irradiance. Annual estimates of habitat-specific production were multiplied by the mates of habitat-specific production were multiplied by the known area of each habitat type to determine total microalgal production for the estuary (3.423 × 10⁹ g C yr^?1). Short Spartina zone habitats provided 45% of total microalgal annual production, followed by intertidal mudflats (22%), tall Spartina zones (18%), shallow subtidal (13%) and microalgal production exceeds phytoplankton and microalgal production but is less than Spartina production.     

INTRASPECIFIC GENETIC DIFFERENTIATION IN CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS) FROM SOUTHERN CALIFORNIA AND THE GULF OF CALIFORNIA

Intraspecific patterns of mitochondrial DNA sequence variation were determined among California sea lions ( Zalophus califomianus californianus ) from three colonies along the Pacific coast of southern and Baja California and one colony in the Gulf of California. We found no variation in 368 base pairs (bp) of cytochrome b sequence among 40 sea lions from these localities, but analysis of 360 base pairs of control region revealed eleven genotypes. The four genotypes found in the Gulf of California population were unique and phylogenetically distinct from those found in sea lions along the Pacific coast. The average sequence divergence between Gulf and Southern California genotypes was 4.3%, suggesting a relatively long period of isolation. However, colonies along the Pacific coast, which are less than 200 km apart, shared mtDNA genotypes, indicating that recent genetic exchange has occurred between them. Therefore, we suggest that regional female philopatry exists in California sea lions. Regional boundaries may be related to oceanic currents or patchiness in the distribution of resources. Further research is needed to better understand the underlying causes of genetic differentiation in the California sea lion.     

ZONATION OF DEEP WATER BENTHIC ALGAE IN THE GULF OF MAINE1

Algal community structure is described for a deep-water rock pinnacle in the Gulf of Maine. Three depth zones of algal dominance were apparent consisting of 1) leathery macrophytes (to 40 m), 2) foliose red algae (to 50 m) and 3) crustose algae (fleshy crusts to 55 m and coralline crusts to 63 m). Microscopic filamentous and erect calcareous algae were also present but inconspicuous. Upright macroscopic filamentous and thin sheet-like forms were not observed on the pinnacle. Sea anemones (Metridium senile) dominated some vertical faces and abrupt prominences in the shallowest regions of the pinnacle (to 24 m) and locally appeared to set the upper vertical limits of kelp and possibly foliose reds. Laminaria sp. formed an open park-like canopy from 24 to 30 m whereas Agarum cribrosum, the deepest kelp, grew as isolated individuals to 40 m. Peyssonnelia sp. and Leptophytum laeve were the deepest occurring fleshy (to 55 m) and calcareous crusts (to 63 m), respectively. The occurrence of these algae at record depths for the Gulf of Maine and for cold water marine environments may be the result of an absence of large herbivores and the high productivity potential of the benthos in these relatively clear waters. By compiling data on depth distribution patterns world-wide, it is evident that the three zone structure of algal morphologies observed in the Gulf of Maine is a global phenomenon.     

NONDESTRUCTIVE TRACING OF MIGRATORY RHYTHMS OF INTERTIDAL BENTHIC MICROALGAE USING IN VIVO CHLOROPHYLL A FLUORESCENCE1,2

In vivo chlorophyll (Chl) a fluorescence was measured in undisturbed intertidal sediments with the purpose of tracing the vertical migratory rhythms of benthic microalgae. A pulse amplitude fluorometer, an instrument which does not require physical contact with the sample, was used, thus allowing successive measurements to be taken on the same sample without causing any type of disturbance to the sediment structure. The basis of the method is the possibility to detect changes in the Chl a concentration near the sediment surface caused by the vertical movement of the microalgae. This requires the verification of two conditions: the possibility to follow changes in the sediment Chl a content from fluorescence intensity, and a sediment photic depth smaller than the vertical distances covered by the moving microalgae. Both conditions were experimentally verified in intertidal muddy sediments of the Tagus estuary, Portugal. In vivo fluorescence was shown to vary linearly with the sediment Chl a content, and the sediment photic depth was estimated to reach 0.27 mm, a value clearly smaller than the reported depths for microalgal migrations. Sediment samples kept under in situ conditions exhibited large hourly Variations (over 400%) in the Chl a fluorescence intensity, which were closely synchronized with the daytime periods of emersion. The rhythmic fluctuations in Chl a fluorescence were confirmed further to represent microalgal migration by (1) its endogenous nature (fluorescence continued to follow diurnal and tidal cycles after removal of environmental stimuli), (2) its dependence on the vertical distribution of the microalgal population within the sediment (vertically homogenized samples failed to display fluorescence variations), and (3) the lack of significant temperature and light effects on the fluorescence emission under in situ conditions (tested in three species representative of the main groups found in the studied microphytobenthic communities—the diatom Phaeodactylum tricornutum (Böhlin), the cyanobacterium Spirulina maxima (Setch. et Gard.), and the euglenophyte Euglena granulata (Klebs) Lemm.). The results obtained indicate that, in spite of the potential concurrent effects of factors other than the Chl a concentration on the fluorescence intensity, in vivo Chl a fluorescence can be used to trace nondestructively the migratory behavior of benthic microalgae.     

AN INVESTIGATION OF THE VERTICAL DISTRIBUTION OF SELECTED BENTHIC MARINE ALGAE WITH A TIDE–SIMULATING APPARATUS1

The growth yields of 8 species of red and 4 species of green algae, collected from various vertical levels on the western Atlantic (New Jersey) shore, were investigated in a range of emersion-submersion regimes in the laboratory. The sinusoidal tide-simulating apparatus consisted of a plexiglass frame connected by a nylon thread to a rotating wheel, powered by an electric motor geared to make one revolution every 12 h. Inocula of settled spores on glass cover-glasses were placed at 6 levels on the frame and alternately raised out of, and lowered into, a seawater tank every 6 h with consequent subjection to 0, 18, 37, 58, 79, and 100% submergence regimes per tidal cycle. There was little correlation between the vertical position of a species on the shore in nature and its ability to grow as the percentage submergence per tidal cycle increased. All species tested grew best when continuously submerged, even those that are usually restricted to elevated positions on the shore in nature. The majority grew well in all regimes in which there was some submergence per tidal cycle, except for one sublittoral species (Callithamnion byssoides) whose growth decreased sharply as the percentage exposure to the air was increased.     

FACTORS CONTROLLING THE INTERTIDAL ZONATION OF IRIDAEA FLACCIDA (RHODOPHYTA)1

Field experiments were used to examine the effects of biological interactions on the abundance of Iridaea flaccida (S. & G.) Silva within and below its normal range in the intertidal zone of central California. A combination of competitor removal, grazer exclusion and transplant manipulations showed that within the I. flaccida zone, this alga can be the first macroscopic plant to become reestablished after clearing and that this can occur in less than two months. Grazing by molluscs within this zone retards, but does not prevent, re-establishment. Although absent prior to the experiments, both I. flaccida and I. cordata (Turn.) Bory settled, grew rapidly and reproduced in cleared areas below the I. flaccida zone, regardless of the presence of grazers. These plants did not establish themselves if entire thalli or holdfasts of other algae normally occupying the lower zone were present. The results support the few other in situ experimental investigations of algal zonation by showing that, when bounded by other plants, the lower limits of intertidal algae are directly determined by competition. They also suggest that I. flaccida and I. cordata may be conspecific.     

西藏南部江孜地区早白垩世甲不拉组底栖有孔虫动物群的发现

根据最新的国际年代地层表,侏罗/白垩系界线是显生宇系一级唯一没有GSSP(全球界线层型与点位)的界线。位于特提斯喜马拉雅北亚带的江孜地区,发育了连续的侏罗/白垩系界线地层,是目前国内海相侏罗/白垩纪界线生物地层学研究最具潜在竞争力的地区之一。本文在西藏南部江孜地区甲不热北沟剖面甲不拉组底部往上3.9米处及19.3米处首次发现了胶结壳底栖有孔虫动物群,共计4属11种:Ammobaculites agglutinans,Ammobaculites sp.1,Ammobaculites sp.2,Ammobaculites sp.3,Ammobaculites sp.4,Ammobaculites sp.5,Glomospira charoides,Haplophragmoides gigas minor,Haplophragmoides sp.1,Haplophragmoides sp.2,Reophax texanus。根据该动物群重要分子的地质时限推测,甲不拉组底部往上3.9米处就已经属于白垩系地层。因此甲不拉组底部胶结壳有孔虫动物群的发现支持了将甲不拉组划归白垩系的意见。     

A SHORT-TERM DEMOGRAPHIC STUDY OF CYSTOSEIRA OSMUNDACEA (FUCALES: CYSTOSEIRACEAE) IN CENTRAL CALIFORNIA1

Several demographic features were examined in the field over a period of eleven months for the subtidal alga Cystoseira osmundacea (Turner) C. Agardh at two localities near Monterey, California. This species showed a restricted distribution with depth, with peak average numbers of 3–4 plants per m² occurring at 6–8 m and forming a dense canopy on the surface of the sea. Below 10 m depth, there was a decline in the abundance of plants and also in the proportion of plants which bore seasonal fronds and reproductive tissue. Macrocystis pyrifera (L.) C. Agardh plants were also common at both localities. There was a negative correlation between the presence of this species and C. osmundacea at a scale of 1 m², but no correlation at 4, 9, and 25 m². Cohorts of C. osmundacea were mapped and tagged at one locality. The plants had markedly seasonal growth, with the greatest elongation of fronds occurring between March and June. Dense surface canopies and reproductive tissue were present during the summer months of June–August. These seasonal fronds were shed during September, leaving small perennial holdfasts and fronds. Plants were strictly dioecious, and there was a one-to-one ratio of male to female plants at both localities. Length-dry weight relationships showed that the largest plants had over 80% of their weight invested in seasonal fronds (vegetative plus reproductive tissue). Recruits of C. osmundacea at one locality appeared during September–November only in areas cleared to bare substratum. There was 15% survival of recruits between November and the following May, while 98% of the original mapped cohort survived for the 11 months of the study.     

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.     

A COMPARISON OF THE ATTACHED ALGAL COMMUNITIES OF A NATURAL AND AN ARTIFICIAL SUBSTRATE1

A study of communities of attached algae in Lake Mize Florida, wax made during July 1969, July-August 1970 and April 1971. The substrates exposed during the study included glass slides mid the terrestrial form of the amphibious sedge, Eleocharis baldwinii (Torr.) Chapman. Counts were used to determine the relative abundance and densities of the species present on the 2 substrates under different environmental conditions. Such analyses indicated that at any given lime and place, a number of factors influenced the composition of the periphyton. Generally, lightly adhering, resupinate species attained higher densities on glass slides than filamentous and loosely associated metaphytonic species. The epiphytic flora of E. baldwinii contained a large number of both strong attachers and the metaphyton. The vertical range of many attached species was also greater on E. baldwinii than on glass slides.     

DISTRIBUTION OF BLUEGREEN ALGAE IN A MISSISSIPPI GULF COAST SALT MARSH1

Edaphic bluegreen algal communities were sampled from five menotypic angiosperm zones in Grvelline Bay Marsh near Ocean Spring. Mississippi. Samples and environmental data were taken on a quarterly basis from October 1976 to June 1977 beneath the following marsh angiosperms: Distichlis spicata (L.) Green, Scirpus olneyi gray, SPartina patens (Aiton) Muhl., Sp. alterniflora Loisel., and Juncus roemerianus Scheele. Communities in all five zones were dominated by Schizothrix calcicola (Ag.) Gom. (sensu Drauet) throughout the study, while the subdominant bluegreens varied according to season. The number of individuals in all zones was greatest in the summer and lowest in the winter. An examination of the structure of the five edaphic communities indicated a single, nearly homogeneous community exists over the entire surface of the marsh shaded by a angiosperm canopy. Light intensity appears to be the major factor affecting the distribution of bluegreen algae in this salt marsh.     

SURVIVAL OF FUCOID EMBRYOS IN THE INTERTIDAL ZONE DEPENDS UPON DEVELOPMENTAL STAGE AND MICROHABITAT1

Embryos of the fucoid alga Pelvetia fastigiata (J. Ag.) DeToni were outplanted into the intertidal zone to assess survival during the physical stress brought about by emersion during a single low tide. Survival varied among microhabitats. Under the adult Pelvetia canopy, survival of 6-h-, 24-h-, 48-h-, and 1-wk-old embryos was nearly 100%. Almost all embryos of all ages died in exposed habitats on bare rock or within habitats where the Pelvetia canopy was removed experimentally. However, within red algal turfs, where most juvenile Pelvetia occur, survival was unusually age specific: 24- to 48-h-old embryos survived poorly compared to younger (6 h old) or older embryos (1 wk old). Survival patterns reflected microhabitat temperatures during the experiments. The fate of young post-settlement stages must be studied at these fine temporal and spatial scales to understand the organization of intertidal communities.     

COMPONENTS OF PHOTOSYNTHESIS IN THE INTERTIDAL SACCATE ALGA HALOSACCION AMERICANUM (RHODOPHYTA,PALMARIALES)1

Rates of photosynthesis for the intertidal saccate alga Halosaccion americanum Lee were determined under submersed and emersed conditions. By fitting the data to a hyperbolic tangent function, P _max was 4.08 mmol CO₂. m^?2. h^?1 and I_k was 116.4 μE. m^?2. s^?1. under submersed conditions. Under emersed conditions, P _max was 1.89 mmol CO₂. m^?2. h^?1 and I_k was 22.9 μE. m^?2. s^?1. Dark fixation represented 3.7% of P_max in submersed thalli, whereas it equalled 33.3% of P_max in emersed thalli. Photosynthetic uptake from the thallus cavity represented a significant source of carbon, achieving 68.8% of that from the atmosphere and 29.4% of that from seawater. Retained seawater also greatly reduced drying under emersed conditions. Experimental thalli lost 70.4% of their water after 120 min under desiccating conditions, whereas control thalli lost only 6.3%. Emersed photosynthetic rates were enhanced by desiccation, At times, rates for desiccated thalli were two times those of fully-hydrated ones. Only after water loss exceeded 47% did photosynthetic rates fall below fully-hydrated rates. Utilizing data from this study a model was constructed to determine total photosynthetic production of H. americanum over a single daylight period. These caluclations demonstrate that photosynthetic contributions from emersed photosynthesis and retained seawater are significant. Because production from all sources is almost equal, total photosynthesis over a single day does not change greatly regardless of the time spent in air or in water.     

中国东北样带草地群落放牧干扰植物多样的变化

放牧干扰是草地群落植物多样性变化的主要影响因素之一。中国东北样带９个草地群落放牧干扰植物多样性性变化的研究结果表明：中牧或重牧阶段Ｓhannon指数达最大值。形成中牧（重牧）＞重牧（中牧）＞轻牧＞过牧的规律。群落物种丰富度、均匀度与多样性的相关分析表明,均匀度变化对多样性变化具有更大的贡献率。而丰富度呈下降趋势,即轻牧（中牧）＞中牧（轻牧）＞重牧＞过牧。生活型功能群多样性也表现出明显的变化。中国东北样带草地群落植物多样性的分布格局是：草甸草原＞典型草原＞典型草原＞荒漠草原＞碱化草甸,并且群落物种丰富度对多样性有更大贡献率。     

OCCURRENCE OF A EUROPEAN RED ALGA (SCHOTTERA NICAEENSIS) IN SOUTHERN AUSTRALIAN WATERS1

Schottera nicaeensis (Phyllophoraceae, Gigartinales), presently known only from the western Mediterranean Sea and the northeastern Atlantic coasts of Europe, is reported for the first time from the Melbourne region of Port Phillip Bay in southeastern Australia. The species is perennial in the Bay, although tetrasporophytes and cystocarpic plants are commonest in late spring and early summer. This seasonal pattern, and the vegetative habits of plants during the whole of the year, show similarities to populations described by other workers for Northern Hemisphere localities where comparable water temperature and daylength regimes obtain. The small Australian S. nicaeensis community is found at 5–9 m depths and is concentrated on lighthouse foundations adjacent to the main Port of Melbourne shipping channel. It is hypothesized that the species has recently been introduced into Port Phillip Bay, and a scenario for its possible means of import on ships is suggested.