Volume 44, Issue 4

The biomass and production of the epiphytic community on the leaves of Cymodocea nodosa were measured during an annual cycle, from June 1991 to May 1992. The biomass of the epiphytes always increased with the age of the leaf in each shoot throughout the year. The mean annual biomass of epiphytes was 52.6 g dw m −2 of leaf, with a maximum of 109 g dw m −2 of leaf in November and a minimum of 33 g dw m −2 of leaf in March. The biomass of the epiphytes was always lower than the biomass of the leaves on which they were growing, except in November. The epiphytic biomass varied from 124.1 g dw m −2 meadow area in winter to 29.7 g dw m −2 in spring. The mean annual contribution of the epiphytes to the total epigean biomass of the meadows was 31 %, with the highest contribution of 34–57% in autumn-winter and the lowest one of 17−28% in spring-summer. The annual production of the epiphytes by shoot area was 453 mg dw year −1 and the annual production of this epiphytic community per m 2 of meadow was 625 g dw year −1 . The mean production of the epiphytes was also estimated over the year. Two maxima were detected, one in winter of 90 μg dw cm −2 day −1 , mainly due to the longest life-time of the leaves in these months (up to 90 days), and the other in late spring-early summer of 86 μg dw cm −2 day −1 because of the high contribution of seasonal epiphytes as well as the highest accumulation of biomass of epiphytes per day. In March and April, the minimum value of 38 mg dw cm −2 day −1 is directly related to the shortest life-time of the leaves in these months (up to 45 days). In general, the epiphytic flora on the leaves of the warm temperate seagrass Cymodocea nodosa showed biomass and productivity tendencies comparable to those known for other temperate and tropical seagrasses.

Effects of temperature, daylength, and irradiance on the growth and tetrasporogenesis of Caulacanthus okamurae and its life history were examined in culture. Plants grew over a wide range of temperature (13–27 °C), daylength (8–16 h light), and irradiance (20–160 μmol photons m −2 s −1 ), and optimal growth occurred at 23 °C, 14:1̅0̅, L:D̄ and 60 μmol photons m −2 s −1 . Tetrasporangia were formed at the same ranges of daylength and irradiance as in the plant growth experiments but did not develop at 13 °C and 16 °C. Life history of C. okamurae was a Polysiphonia -type and it was completed in unialgal culture within 4–5 months. Early developmental patterns of tetraspores and carpospores were similar; spores divided into two unequal cells each producing a single rhizoid. Cystocarps were formed at the end of branch tips of female plants. On the basis of physiological and morphological features, the taxonomic position of C. okamurae is discussed.

Koorchaloma spartinicola sp. nov. is described and illustrated based on specimens collected on decaying Spartina alterniflora leaf blades, from Sapelo Island, Georgia, U. S. A. The new species is compared with other species of Koorchaloma , and a key and a table are provided. Koorchaloma spartinicola differs from other species of Koorchaloma , especially in that it has conidiophores largely reduced to conidiogenous cells, brown setae to only 80 μm length that are not swollen at the apex, and large, broad conidia (mean length = 18 μm; length: width = 2.9:1) with mucoid appendages at both ends, the apical one ultimately splitting into several radiating strands.

During the summer months, Langstone Harbour, a eutrophic inlet on the south coast of England, is subject to blooms of green macroalgae commonly referred to as ‘green tides’. In a series of laboratory experiments, the vegetative growth of eight ‘green tide’ algae collected from the harbour was examined under a range of irradiances, temperatures, salinities and N and P concentrations. Test algae were Chaetomorpha linum, Cladophora dalmatica, Enteromorpha compressa, Enteromorpha linza, Percursaria percursa, Rhizoclonium tortuosum , Ulva curvata and Ulva rigida . All algae showed a broad tolerance to the environmental conditions of irradiance, temperature and salinity. The most rapid growth rates were recorded in irradiances ranging from 18 to 175 mmol m −2 s −1 , whilst the temperature promoting the most rapid algal growth ranged from 10 to 20 °C. With respect to salinity, the highest growth rates were recorded for algae cultured in the range 6.8 to 27.2 PSU. Several species were tolerant of salinities as low as 3.4 and 0 PSU. All algae showed a broad tolerance to a wide range of N and P concentrations. Maximum growth rates were recorded in nutrient concentrations ranging from 10 to 100 mmol m −3 PO 4 , 100 to 1000 mmol m −3 NO 3 and 60 to 100 mmol m −3 NH 4 . At these concentrations of N and P, considerable biomass was attained by the algae, with growth rates up to 21% per day. This, coupled with their broad environmental tolerance, is likely to promote their ecological success in the shallow, nutrient-enriched waters of Langstone Harbour and, indeed, in eutrophic waters worldwide.

Dasya puertoricensis is newly described from subtidal habitats in southwestern Puerto Rico. The new species is characterized by its conspicuously dense, brush-like branch tips, rhizoidal cortication and by its indeterminate adventitious filaments which arise from pseudolateral basal cells. Adventitious monosiphonous laterals are absent. Tetrasporangial stichidia normally possess 6 sporangia per fertile whorl. The cystocarps are sessile with cortical cells at their broadened bases enveloping the bearing branches.

Macroalgae living at high latitudes experience considerable variation in the availability of light energy and nutrients. Perennial species may smooth these variations by utilising internal energy and nutrient reserves. These reserves also enable growth during the unfavourable season. The northern Baltic Fucus vesiculosus exhibited vegetative growth throughout the year. The lowest winter growth rate was 1/3 of the highest growth rate in summer. The mannitol content of F. vesiculosus , probably used as an energy reserve, followed the annual cycle of solar radiation. The mannitol reserve was not utilised completely. The lowest winter concentrations of mannitol were 1/3 of the highest summer concentrations. The highest internal nitrogen concentrations were measured in spring, just before the spring bloom depleted the dissolved inorganic nitrogen of seawater. The internal nitrogen reserves declined steadily during the summer period to their minimum in August–September. Our results indicate that F. vesiculosus stores nitrogen for rapid summer growth in nitrogen depleted conditions and mannitol for growth during the dark winter period. Baltic F. vesiculosus is thus well adapted to the conditions of northern latitudes, where nutrients and light energy are not simultaneously available.

Six genera and 13 species of red algae, characteristic of sand-plain habitats between 10 and 28 m depths, are reported for the first time for the Caribbean coast of Colombia. They are Amphiroa beauvoisii Lamouroux, Halymenia pseudofloresia Collins et Howe, Dudresnaya bermudensis Setchell, D. crassa Howe, Sebdenia flabellata (J. Agardh) Parkinson, Agardhiella subulata (C. Agardh) Kraft et Wynne, Sarcodiotheca dichotoma (Howe) Dawson, S. divaricata W. R. Taylor, Chrysymenia enteromorpha (Harvey) Farlow, Lomentaria corallicola Børgesen, Dictyurus occidentalis J. Agardh, Laurencia brongniartii J. Agardh, and Micropeuce mucronata (Harvey) Kylin ex E. C. Oliveira. Agardhiella subulata differs from Solieria filiformis (Kützing) Gabrielson both in morphology and in habitat. Sarcodiotheca caribaea from the Caribbean Sea is considered to be conspecific with S. dichotoma from the Gulf of California (Mexico), and it is reported for the second time for the Atlantic Ocean. Sarcodiotheca divaricata is reported for the second time for the Atlantic Ocean and for the first time for the Caribbean Sea. Lomentaria rawitscheri Joly (1957) from Brazil is considered here to be conspecific with L. corallicola Børgesen (1939) from the Gulf of Iran.

The acclimation responses of two intertidal macroalgae, Gracilaria sp. and Enteromorpha intestinalis , to different dissolved inorganic carbon (DIC) levels were investigated under laboratory conditions. The effect of DIC availability on growth rate, biochemical composition (C, N, pigments and Rubisco) and on the degree of inhibition of external and total carbonic anhydrase activities (by acetazolamide and 6-ethoxyzolamide, respectively), and of a putative HCO 3 − exchanger protein (sensitive to the inhibitor 4,4′-diisothiocyanatostilbene-2,2′-disulfonate, DIDS) was species-specific. Pigment and Rubisco contents co-varied negatively with DIC availability in Gracilaria sp. However, no such pattern was observed in Enteromorpha intestinalis . The mechanisms of DIC uptake were also modulated by the external DIC concentration. Under limiting DIC conditions, the induction of mechanisms for CO 2 acquisition above the diffusive rate was observed in Gracilaria sp., while a repression of the DIDS-sensitive mechanism was obtained for Enteromorpha intestinalis . The results revealed the plasticity of these intertidal macroalgae to acclimate to different ambient DIC levels, and indicate the important role of DIC as a factor controlling biochemical and physiological processes.

Growth of female gametophyte and sporophyte phases of Chondracanthus chamissoi was measured under controlled laboratory conditions, examining effects of different combinations of photon flux density and temperature. Apical segments of both (isomorphic) phases of this alga were cultivated in Von Stosch medium using 12 combinations of photon flux density (PFD; 20 to 120 μmol m −2 s −1 ) and temperature (10 to 25 °C), comparing the wet weights of thalli produced after 15 days. A difference in the growth rate was noted between the isomorphic phases in which the female gametophyte grew more than the sporophyte at 15 °C and above. In both phases, there was a tendency towards increasing growth with increasing temperature, whereas changes in PFD did not produce significant changes in growth in all treatments. However, a significant growth effect due to interaction of the two variables was noted. Within the range of variables studied, temperature was the controlling factor in the growth of Chondracanthus chamissoi mediated by factors of light and life cycle phase. The differential growth of different life cycle phases in response to environmental variables may explain the dominance of one phase over another in natural stands of this alga.

Among the most common diatoms in arctic spring blooms are Fossula arctica Hasle, Syvertsen et von Quillfeldt, Fragilariopsis cylindrus (Grunow) Krieger in Helmcke et Krieger, F. oceanica (Cleve) Hasle, Thalassiosira antarctica var. borealis Fryxell, Doucette et Hubbard, T. hyalina (Grunow) Gran and Chaetoceros sociali s Lauder. Although Fossula arctica was described as late as 1996, the others have been recorded for more than 100 years. Despite this, the different Fragilariopsis species are often confused with each other and with other ribbon-shaped species. This is also true of Thalassiosira spp. The need to clarify the differences between some of these common arctic diatoms is clear. Identifying species in water mounts may be particularly difficult. Descriptions in the literature of species in water mounts are also rather few. A study was conducted in order to facilitate the identification of those species most often confused. Distinctive features for each species are described and illustrated and possible misidentifications discussed to ease the identification. The results are based on the author's samples collected from different Arctic areas as well as on information from the literature.

A checklist of the benthic marine plants of the archipelago of Madeira is presented based on published information and personal observations. This list includes 1 Spermatophyte and 359 algal species, comprising 64 Chlorophycota, 64 Chromophycota and 231 Rhodophycota. Fifteen doubtful records for the area are also included.