Fabio Rindi

DIVERSITY, LIFE HISTORY, AND ECOLOGY OF TRENTEPOHLIA AND PRINTZINA (TRENTEPOHLIALES, CHLOROPHYTA) IN URBAN HABITATS IN WESTERN IRELAND 1

On the basis of field and culture investigations, five species of the genera Trentepohlia and Printzina were found to occur in urban habitats in western Ireland: Trentepohlia abietina (Flotow) Hansgirg, T. aurea (Linnaeus) Martius, T. iolithus (Linnaeus) Wallroth, T. cf. umbrina (Kützing) Bornet, and Printzina lagenifera (Hildebrandt) Thompson et Wujek. These species formed perennial populations on a variety of substrata. T. abietina occurred on bark of trees; T. cf. umbrina occurred on stone walls; and P. lagenifera grew on several substrata, mainly cement and asbestos sheeting. T. aurea and T. iolithus were found on old concrete and cement walls; in particular, the latter species formed characteristic, extensive, deep‐red patches on many buildings. In culture, best growth and reproduction of these species were observed at 10 and 15° C, 16:8 h light:dark. Both in culture and in the field, reproduction took place by release of biflagellate swarmers behaving as asexual spores, germinating to produce new plants without any evidence of sexual fusion; release of biflagellate swarmers in the field was generally observed in all seasons throughout a whole annual cycle. Confirmation of the occurrence of sexual reproduction in Trentepohlia was not obtained.

THE PRASIOLALES (CHLOROPHYTA) OF ATLANTIC EUROPE: AN ASSESSMENT BASED ON MORPHOLOGICAL, MOLECULAR, AND ECOLOGICAL DATA, INCLUDING THE CHARACTERIZATION OF ROSENVINGIELLA RADICANS (KÜTZING) COMB. NOV.1

Despite a simple morphology and intensive studies carried out for more than two centuries, the systematics of the Prasiolales still presents several unsolved problems. The taxonomic relationships of several common species of Prasiolales, mostly from northern Europe, were investigated by a combination of morphological observations, culture experiments, and molecular analyses based on rbcL sequences. The results indicate that Rosenvingiella and Prasiola are separate genera. The capacity for production of tridimensional pluriseriate gametangia and the presence of unicellular rhizoids are the morphological features that discriminate Rosenvingiella from filamentous forms of Prasiola. The molecular data indicate that uniseriate filaments can be produced in at least three different species of Prasiola. The genetic diversity of uniseriate filamentous Prasiolales is higher than their simple morphology would indicate, and the provisional retention of Schizogonium Kützing 1843 as independent genus is recommended. The rbcL phylogeny confirms that Prasiola calophylla, P. crispa, and P. stipitata are distinct species, whereas P. stipitata and P. meridionalis are probably conspecific. Rosenvingiella polyrhiza is a strictly marine alga, and most records of Rosenvingiella in Europe are referable to Rosenvingiella radicans, proposed here as a new combination based on Ulothrix radicans Kützing 1849 . This is a primarily terrestrial alga that can occur from upper intertidal rock to locations situated hundreds of kilometers inland. The great confusion that has arisen in Europe between these two species in the last century is mostly due to misidentifications of marine populations of R. radicans.

THE MARINE AND TERRESTRIAL PRASIOLALES (CHLOROPHYTA) OF GALWAY CITY, IRELAND: A MORPHOLOGICAL AND ECOLOGICAL STUDY

Green algae belonging to the order Prasiolales have been reported frequently in terrestrial, freshwater, and marine habitats, generally in situations in which they are not submerged continuously and often in association with deposits of avian feces or other rich sources of nitrogenous compounds. Terrestrial habitats in Galway City on the west coast of Ireland have large populations of four such algae: Rosenvingiella polyrhiza (Rosenvinge) P. C. Silva, Prasiola calophylla (Carmichael ex Greville) Kützing, P. crispa (Lightfoot) Kützing, and P. stipitata Suhr ex Jessen, of which only the last is in any way fully associated with a tidal regime. The other species are found in an extraordinary range of nonmarine terrestrial habitats in the center of Galway, a city that still retains its narrow, medieval street plan. Width of the streets, proportion of residences, substratum type, and aspect are shown to be the main factors affecting the distribution of these algae, although a combination of consistent dampness and nitrogenous‐compound availability from animal wastes is likely to be the primary determining factor. Morphological and phenological data are presented for each entity, and it is concluded from field observations that R. polyrhiza should continue to be recognized as a separate entity, even though a close relationship with Schizogonium murale Kützing is probable.

A long-term comparison of the benthic algal flora of Clare Island, County Mayo, western Ireland

The marine benthic algal flora of Clare Island, off County Mayo, western shore of Ireland, was investigated; collections of intertidal and subtidal marine algae were made at 16 sites along the eastern and southern shores in the years 1990, 1993 and 2000–2002. The data and observations obtained were compared with the results of a similar survey conducted by Arthur Disbrowe Cotton in 1910–1911. Considering the results of the original survey and the new survey together, the marine algal flora of the island currently totals 293 species; 224 species were recorded by Cotton in the original survey, whereas 223 species were identified in the present study. Most species are common to the original and the new list and the main differences are easily explainable; the new survey used SCUBA diving, which allowed the collection of several subtidal species not collected in 1910, and Cotton reported several microscopic green and brown algae, usually difficult to recognise in the field, which were not rediscovered. The most remarkable differences consist in the current presence of some large intertidal brown algae (Bifurcaria bifurcata, Cystoseira foeniculacea and Cystoseira nodicaulis) that were not reported in the survey of 1910. Two algae, Codium fragile subsp. tomentosoides and Asparagopsis armata, were introduced in Europe after the original survey. At present, the benthic algal assemblages of Clare Island still have basically the same structure and distribution as in 1910 and, if compared with other coastal areas of Europe, the intertidal marine environment of Clare Island appears remarkably well conserved.

Phenology and small-scale distribution of some rhodomelacean red algae on a western Mediterranean rocky shore

Distribution and phenology of some filamentous species of Rhodomelaceae in the low littoral and shallow sublittoral zones of an exposed, western Mediterranean rocky shore were studied for 1 year. The spatial distribution of many species shows a pronounced small-scale (metres or tens of metres) variability. Boergeseniella fruticulosa was most abundant in spring and fertile (tetrasporangia only) in spring and summer. Polysiphonia flocculosa was most abundant in spring and summer and reproductive throughout the year. Polysiphonia opaca was most abundant in summer and fertile in spring–summer. Maximal vegetative development and reproduction of Lophosiphonia cristata were observed in summer; conversely, Polysiphonia ceramiaeformis and Polysiphonia subulata were best developed and mostly reproductive in winter and spring. Womersleyella setacea was the least abundant of the studied species and apparently reproduced only by vegetative growth and fragmentation. The reproductive phenology of the species investigated is generally in agreement with reports for other Mediterranean regions. The life history traits of most species are typical of seaweeds in which environmental factors directly govern the onset of the main activities of the organism by meeting the primary physiological needs (‘season responders’).

Ecophysiological performance of an urban strain of the aeroterrestrial green alga Klebsormidium sp. (Klebsormidiales, Klebsormidiophyceae)

Aeroterrestrial green algae are among the most ubiquitous members of the microbial flora colonizing aerial surfaces. Filamentous green algae, in particular, produce large populations in several natural and artificial habitats. In recent years it has been shown that the bases of the walls of urban environments are frequently colonized by filamentous green algae. However, information concerning the physiology of these organisms and the factors that determine their distribution is extremely limited. We studied the physiological responses of a strain of Klebsormidium sp. (Klebsormidiales, Klebsormidiophyceae) collected in an urban area (Konstanz, Germany). Growth responses, photosynthetic performance, desiccation tolerance and accumulation of organic osmolytes were measured in several different combinations of environmental factors. Klebsormidium sp. exhibited optimal growth and highest photosynthetic efficiency under relatively low photon fluence rates, performing optimally between 15 and 30u2009µmol photons m−2u2009s−1 and showing increasing inhibition above 85u2009µmol photons m−2u2009s−1. Although it could survive at salinities up to 60u2009psu, this alga was relatively stenohaline; growth was optimal between 1.2 and 15u2009psu and declined considerably at higher salinities. Sucrose acted as the major organic osmolyte, and its concentration increased almost linearly between 1.2 and 30u2009psu from 29.7 to 171.2u2009µmolu2009g−1u2009dry weight. Further increases in salinity, however, were accompanied by a strong reduction in sucrose content pointing to insufficient osmotic adjustment. Klebsormidium sp. was able to photosynthesize efficiently for up to 2 hours under complete desiccation. Afterwards, however, there was no measurable photosynthetic activity although complete photosynthetic efficiency (F v/F m) was recovered upon rehydration for 48 hours. Overall, the results correlate well with the ecology of Klebsormidium sp. in the field and its distribution in continental Europe.

Spatio-temporal variability of intertidal algal assemblages of the Slovenian coast (Gulf of Trieste, northern Adriatic Sea)

Abstract The algal assemblages of the northern Adriatic Sea have been studied intensively, but few quantitative data on their spatial and temporal dynamics are available. The intertidal assemblages of two coasts on the Gulf of Trieste were studied for a year, and the patterns of spatio-temporal variability were examined at several scales in space and time. Patterns for the whole assemblage and individual species were analysed by multivariate and univariate analyses. The assemblages of the two shores were relatively poor in species and characterised by different compositions. A moderate temporal variation was found, mostly related to differences between the periods winter-spring and summer-autumn. Patterns for individual species were mainly characterised by differences between the two shores (Polysiphonia opaca), interactions among shores and sampling dates (Fucus virsoides, Ulva compressa, Gelidium pusillum, Lophosiphonia obscura) and differences on the spatial scale of tens of metres (Ceramium species in aggregate, Cladophora albida, Ectocarpus siliculosus, Ulva laetevirens). The dissimilarity between the assemblages of the two shores was the emergent pattern, and differences in the texture and composition of the rocky substratum (marl and limestone, respectively) are considered perhaps the main causes of these differences. Future studies in this region should give more attention to this factor.

Phylogenetic analysis of rhodolith formation in the Corallinales (Rhodophyta)

Although the ecological importance of rhodolith (maerl, free-living coralline algae) beds is well-known, rhodolith-forming species have been neglected in molecular phylogenetic studies. This is the first molecular systematic study aimed at understanding whether the rhodolith habit is a fixed feature in lineages and determining the relationship (phylogenetic vs. environmental) between rhodolith and crustose habits. Phylogenetic relationships of rhodolith-forming species and encrusting coralline algae at generic and species levels were analysed using SSU rDNA and psbA sequences. Extensive sampling in the European North Atlantic, Pacific and Caribbean Mexico of Phymatolithon, Lithothamnion, Lithophyllum and Neogoniolithon taxa forming rhodoliths and crusts was accompanied by examination of type or topotype material. Phylogenetic reconstruction showed that Neogoniolithon contained a monophyletic group of rhodolith-forming species whereas other rhodolith-formers were closely related to encrusting forms in the genera Phymatolithon, Lithothamnion, Mesophyllum, Hydrolithon, Spongites and Sporolithon. DNA analysis showed that the crust-forming Lithophyllum cf. incrustans/dentatum also forms rhodoliths with a stone nucleus that occur on rocky shores. In contrast, species that form beds of non-nucleate rhodoliths (e.g. Neogoniolithon spectabile, N. strictum, Lithophyllum cf. incrustans/dentatum or sp. 1 and Phymatolithon calcareum) rarely form crusts. The rhodolith habit cannot be used to delimit species for taxonomic or identification purposes. Extensive taxonomic revision will be required to deal with problems such as the position of specimens identified as Lithophyllum margaritae in two unrelated lineages.

Reproduction and life history of the green alga Prasiola linearis Jao (Trebouxiophyceae, Chlorophyta)

Marine species of Prasiola are most common on rocky shores of the North Atlantic and North Pacific Oceans. Prasiola linearis is a little-known member of this group, whose known distribution is restricted to coastal marshes of Pacific North America. The little information available on this species is mostly based on the original description; its life history has not been previously reported. Reproduction and life history were investigated in a series of experiments conducted in different combinations of culture medium, temperature, daylength and photon irradiance. The alga reproduced by aplanospores that were produced in the apical part of the blade. Upon release, each aplanospore reproduced a new thallus; sexual reproduction, which occurs in other marine species of Prasiola (P. stipitata and P. meridionalis) was not observed in P. linearis. No variation in reproductive patterns was observed between different combinations of factors tested; however, the alga showed very weak growth at 208C. The life history of Prasiola linearis consists of a repetition of the same morphological phase reproducing by aplanospores. The diversity of life histories observed in marine species of Prasiola is illustrated and discussed.