EVOLUTION OF THE ANTARCTIC MARINE BENTHIC ALGAL FLORA

There are many logistic difficulties associated with studying Antarctic marine algae and, as a consequence, the taxonomic information available is far from comprehensive and any generalizations should be regarded with caution. The Antarctic marine benthic flora is characterized by a low species richness. Biogeographical characteristics of the flora are outlined. There is a high degree of endemism, possibly around 35–40%. Other major floristic elements are a group of species with a distribution extending to Tierra del Fuego and subantarctic islands, a group spread through temperate regions of the Southern Hemisphere, and a cosmopolitan group. Ecological observations show that ice has a major effect on the occurrence and distribution of algae, and ecophysiological studies indicate that Antarctic macroalgae possess various adaptations to ice, low temperatures, and strongly seasonal light conditions. Possible trends in the evolution of the Antarctic benthic marine flora, including a reduction in species richness and the origins of biogeographical links with subantarctic and temperate regions of the Southern Hemisphere, are discussed in the context of tectonic and climatic changes over the past 100 million years. A comparison is made with studies on the evolution of shallow-water marine fauna.     

BENTHIC ALGAL COMMUNITIES OF THE METOLIUS RIVER1,2

Sampling of benthic algae from selected sites in the Metolius River was carried out at regular intervals between April 15, 1967 and March 9, 1968 to determine the species composition of the communities. With the exception of the sampling site at the headwaters and the site immediately downstream, the benthic community of the Metolius River is described as a Cladophora–Achnanthes–Spirogyra community, with species of these 3 genera predominating on a year-round basis. The community described for the headwaters and the sampling site immediately downstream was composed primarily of Nitzchia palea and Cymbella cistula. Of the approximately 60 species of algae which were identified, only 9 showed a definite seasonal distribution, the remaining species being found on a year-round basis.     

PCR AMPLIFICATION OF NUCLEAR AND PLASTID GENES FROM ALGAL HERBARIUM SPECIMENS AND ALGAL SPORES1

Plastid and nuclear ribosomal genes were amplified from an 11-year-old herbarium specimen using simple, rapid, nontoxic, and inexpensive methods. Gonimoblast tissue, isolated from either dried or fresh red algal cystocarps, was ground using the polyvalent, metal chelating resin Chelax 100. After boiling and centrifuging, the supernatant yielding enough DNA for 20 or more polymerase chain reactions. Using these methods, we also amplified plastid and nuclear genes from as few as two red algal spores. These methods should facilitate future studies of algal systematics, evolutionary biogeography, and phylogeny as well as studies of algal dispersal patterns and population biology.     

LARVAL ECOLOGY OF MARINE BENTHIC INVERTEBRATES: PALEOBIOLOGICAL IMPLICATIONS

1. Modes of larval development play important roles in the ecology, biogeography, and evolution of marine benthic organisms. Studies of the larval ecology of fossil organisms can contribute greatly to our understanding of such roles by allowing us to race effects on evolutionary time scales. 2. Modes of development can be inferred for well preserved molluscan fossils because the size of the initial larval shell (Protoconch I in gastropods, Prodissoconch I in bivalves) reflects egg size. Other morphological criteria are also available, and a comparative approach based on related taxa with known development may be the most reliable method. By combining larval and adult traits, it is possible to recognize modes of larval development in at least some fossil bryozoans, brachiopods, and echinoderms as well. (a) Planktotrophic larvae arise from small eggs, are released in enormous numbers with little parental investment per offspring, and suffer tremendous mortality during and shortly after a planktic existence. These larvae feed on the plankton during development, and are commonly capable of a prolonged free-swimming existence, and thus wide dispersal. (b) Nonplanktotrophic larvae (which include both planktic lecithotrophic forms and ‘direct developers’) generally arise from large eggs, with relatively few young produced per parent. Relative to planktotrophic larvae, nonplanktotrophic larvae generally receive greater parental investment per larva, and larval mortality is generally lower. These larvae rely on yolk for nutrition during development, and planktic durations are generally much briefer than for species with planktotrophic larvae, so that dispersal capability is considerably less. Energetic investment per egg is generally higher than in planktotrophs, but as there are lower fecundities as well it is difficult to generalize about the total energetic cost of one mode of reproduction against the other. 3. Owing to the high dispersal capability of planktotrophic larvae, it has been suggested that species with such larvae will be geographically widespread, geologically long-ranging, and exhibit low speciation and extinction rates. Species with nonplanktotrophic larvae will tend to be geographically more restricted, geologically short-ranging, and exhibit high speciation and extinction rates (again, as a consequence of their characteristically low larval dispersal capabilities). 4. Recognition of differential dispersal capabilities can play a role in paleobiogeo-graphic analyses. Concurrent study of the distribution of groups with contrasting modes of development will permit testing of hypotheses concerning timing, magnitudes and frequencies of migration and vicariance events. 5. Larval types are not randomly distributed in the oceans, but relationships with other aspects of the organisms' biology and habitats are very complex. Mode of development varies with: (a) Ecology. A simple r–––K model of adaptive strategies is clearly insufficient to explain the observed relationships: while many ‘equilibrium’ species have nonplanktotrophic larvae, and organisms living in less prdictable environments often have planktotrophic larvae, some of the most opportunistic marine species have nonplanktotrophic larvae. Nonetheless, planktotrophic development seems most suited for exploitation of patchy but widespread habitats. (b) Latitude. At shelf depths, planktotrophy is predominant in the tropics, and decreases sharply at high latitudes. (c) Depth. Incidence of planktotrophy decreases with depth across the continental shelf, at least in some taxa. Beyond the shelf, many deep-sea organisms are nonplanktotrophic (e.g. most bivalves, peracarid crustaceans), but planktotrophic development appears to be present in other groups (prosobranch gastropods, ophiuroids, and bivalves inhabiting transient habitats such as sunken wood and hydrothermal vents). These trends in developmental types will be accompanied by trends in evolutionary rates and patterns as outlined above. The study of larval ecology by paleobiologists will yield insights into the processes that gave rise to ancient evolutionary and biogeographic patterns, and will permit the development and testing of hypotheses on the origins of the patterns observed in modern seas.     

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.     

EXPERIMENTAL MESOCOSM STUDIES OF SALINITY EFFECTS ON THE BENTHIC ALGAL COMMUNITY OF A SALINE LAKE

As closed-basin systems, saline lakes are prone to fluctuate in level and salinity with climate change and hydrologic alterations. Loss of many Great Basin lakes has resulted from the diversion of tributary streams for agricultural or municipal uses. At Mono Lake, an alkaline salt lake in eastern California, salinities have risen from 50 to 100 g·L^?1 in just 50 years. Experimental mesocosms were established to simulate some of the potential ecological effects that could have accompanied this change. The influence of salinity on diatom diversity, taxonomic structure, and primary production was tested using mesocosms deployed at Mono Lake. Mesocosm tanks were 500 L in volume, 1 m square, and 0.5 m deep, with open tops covered by 1 mm mesh net. Five treatments (50, 75, 100, 125, and 150 g·L^?1) with four replicates per treatment were used over a 2-month period. The diatom-dominated benthic algae were reduced both in standing crop (from 6 to <0.1 g·m^?2) and diversity (from 30 to 12 taxa) with increased salinity, with most loss occurring in salinities ≥75 g·L^?1. Photosynthetic oxygen production also was significantly lower at salinities ≥75 g·L^?1. Diatom indicator taxa for these shifts included Denticula sp., Nitzschia frustulum, N. monoensis, N. communis, and Stephanodiscus oregonicus increasing in relative abundance in higher salinity treatments, accompanied by decreases in Achnanthes minutissima, Cymbella minuta, N. dissipata, and Rhoicosphenia abbreviata. Exhibiting dominance at moderate salinity levels (75 to 125 g·L^?1) were Nitzschia frustulum, N. communis, N. palea, and Navicula crucialis. These latter species may be limited by both physiological stress at high salinity and grazing and competition at low salinity. The filamentous chlorophyte, Ctenocladus circinnatus, and cyanobacteria (Oscillatoria spp.) occurred only in salinity treatments from 50 to 100 g·L^?1. Diversion of tributary stream flow and resulting salinity increases in this lake threaten sustained benthic primary production and algal species diversity relative to conditions prior to stream diversion. The 1994 decision of the California State Water Resources Control Board to return stream flows to Mono Lake will raise the lake level and reduce salinity to around 75 g·L^?1 and is expected to increase the diversity and productivity of the benthic algae of this ecosystem.     

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.     

SPATIAL PATTERNS AND ECOLOGICAL DETERMINANTS OF BENTHIC ALGAL ASSEMBLAGES IN MID-ATLANTIC STREAMS, USA

We attempted to identify spatial patterns and determinants for benthic algal assemblages in Mid-Atlantic streams. Periphyton, water chemistry, stream physical habitat, riparian conditions, and land cover/use in watersheds were characterized at 89 randomly selected stream sites in the Mid-Atlantic region. Cluster analysis (TWINSPAN) partitioned all sites into six groups on the basis of diatom species composition. Stepwise discriminant function analysis indicated that these diatom groups can be best separated by watershed land cover/use (percentage forest cover), water temperature, and riparian conditions (riparian agricultural activities). However, the diatom-based stream classification did not correspond to Omernik's ecoregional classification. Algal biomass measured as chl a can be related to nutrients in habitats where other factors do not constrain accumulation. A regression tree model indicated that chl a concentrations in the Mid-Atlantic streams can be best predicted by conductivity, stream slope, total phosphorus, total nitrogen, and riparian canopy coverage. Our data suggest that broad spatial patterns of benthic diatom assemblages can be predicted both by coarse-scale factors, such as land cover/use in watersheds, and by site-specific factors, such as riparian conditions. However, algal biomass measured as chl a was less predictable using a simple regression approach. The regression tree model was effective for showing that ecological determinants of chl a were hierarchical in the Mid-Atlantic streams.     

RHAMNOCHRYSIS AESTUARINAE,A NEW MONOTYPIC GENUS OF BENTHIC MARINE CHRYSOPHYTES1

Rhamnochrysis aestuarinae from Ipswich, Massachusetts, is a new species of benthic marine chrysophyta. Details are given describing its gross and fine structure morphology, its reproductive life history as understood from, both field and culture studies, and its ecology and probable systematic position in the Chrysomeridaceae (Sarcinochrysidales).     

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.     

A PORTABLE DIGITAL SOUND EMITTER FOR INTERACTIVE PLAYBACK OF ANIMAL VOCALISATIONS

ABSTRACT

A new portable digital sound emitter (DSE) for normal and interactive playback of sound signals in the field and in the laboratory is described together with two examples of applications of the DSE in interactive field experiments. The DSE may be loaded with a broad spectrum of digitised sounds, e.g. artificial signals or natural animal vocalisations, and it is controlled via the keyboard of a portable PC running a dedicated program. This program, which can be tailored to support a vast number of different demands, enables the experimenter to start and stop the analog output from the DSE at any time and to choose freely between the available sounds and playback modes. The use of the DSE for interactive playback experiments therefore is only limited by the ability of the operator to perceive the vocalisations of the participating animal and to operate the keyboard of the PC.     

海南岛海产鱼类吸虫两新种

本文记叙了海鲶长等睾吸虫和马面鲀四管吸虫两新种的特征,并与其近似种做了对比描述。     

渤海北部底栖海藻的初步研究

报道了渤海北部底栖海藻的种类组成、区系性质、群落结构和季节性变化。经调查,该海区隶属于蓝藻门、红藻门、褐藻门和绿藻门的底栖海藻共有１１９ 种,其中包括５７ 种经济海藻和７ 个新记录种。研究表明,渤海北部底栖海藻的温度性质以暖温带性为主,带有一定的亚热带性;其群落成分的季节性变化非常明显     

INTRACELLULAR PHOTOSYNTHATE ALLOCATION AND THE CONTROL OF ARCTIC MARINE ICE ALGAL PRODUCTION1

Ice algae are a case study in photo-autotrophic growth and metabolism under chronically low temperature and irradiance. We measured the allocation of ¹⁴C-labelled photosynthate among major classes of intracellular carbon (low molecular weight compounds, or LMW; lipid; protein; and polysaccharide) and found light-dependent changes in allocation broadly similar to photo-adaptive responses known in phytoplankton at higher temperatures; average relative allocation to protein varied inversely (10–37%) and allocation to lipids and polysaccharides directly (10–23%, and 16–21%, respectively) with the sub-inhibiting irradiance levels we employed (3.5–33.0 μE.M⁻². s⁻¹). Unlike many observations at higher temperatures, ours indicated (on average) a large and light-insensitive allocation to LMW (ca. 40%) and a greater light-sensitivity in lipid than in polysaccharide allocation. At the higher incubation irradiances, resembling in situ levels typical of areas with little (0–5 cm) snow cover, allocation to protein was often low (10–13%) compared to many observations of nutrient-sufficient or light-limited phytoplankton. Allocation to protein increased substantially (to ca. 40%) during a period of intensified tidal mixing, and assimilation numbers also attained a maximum at about the same time. Such dynamics show that the ice algae are not constrained to their often protein-poor allocation by the constantly low ambient temperature. Rather, they display marked shifts in metabolism consistent with major changes in light and inorganic nutrient supply, driven in part by the physical process of tidal mixing.     

INTRACELLULAR PHOTOSYNTHATE ALLOCATION AND THE CONTROL OF ARCTIC MARINE ICE ALGAL PRODUCTION1

Ice algae are a case study in photo-autotrophic growth and metabolism under chronically low temperature and irradiance. We measured the allocation of ¹⁴C-labelled photosynthate among major classes of intracellular carbon (low molecular weight compounds, or LMW; lipid; protein; and polysaccharide) and found light-dependent changes in allocation broadly similar to photo-adaptive responses known in phytoplankton at higher temperatures; average relative allocation to protein varied inversely (10–37%) and allocation to lipids and polysaccharides directly (10–23%, and 16–21%, respectively) with the sub-inhibiting irradiance levels we employed (3.5–33.0 μE·M⁻²·s⁻¹). Unlike many observations at higher temperatures, ours indicated (on average) a large and light-insensitive allocation to LMW (ca. 40%) and a greater light-sensitivity in lipid than in polysaccharide allocation. At the higher incubation irradiances, resembling in situ levels typical of areas with little (0–5 cm) snow cover, allocation to protein was often low (10–13%) compared to many observations of nutrient-sufficient or light-limited phytoplankton. Allocation to protein increased substantially (to ca. 40%) during a period of intensified tidal mixing, and assimilation numbers also attained a maximum at about the same time. Suck dynamics show that the ice algae are not constrained to their often protein-poor allocation by the constantly low ambient temperature. Rather, they display marked shifts in metabolism consistent with major changes in light and inorganic nutrient supply, driven in part by the physical process of tidal mixing.