The effects of desiccation and salinity gradients on the PSII photochemical efficiency of an intertidal brown alga,Sargassum fusiforme from Kagoshima,Japan

The responses of photochemical efficiency to desiccation and salinity gradients in an intertidal edible brown macroalga, Sargassum fusiforme (Harvey) Setchell (Sargassaceae, Fucales), were determined using a pulse amplitude modulation (PAM)-chlorophyll fluorometer. The effective quantum yields (ΔF/F_m'; = Φ_PSII) of photosystem II (PSII) dropped to zero after 360-min aerial exposure under low irradiance (20 μmol photons m⁻² s⁻¹) and 120-min exposure under high irradiance (700 μmol photons m⁻² s⁻¹) for this species at 20°C and 50% relative humidity. Under these conditions, ΔF/F_m' failed to recover to initial levels even after 1-day rehydration in seawater. In general, ΔF/F_m' decreased as desiccation reduced the absolute water content (AWC, %). Nevertheless, when AWC was above ca. 20%, ΔF/F_m' was mostly restored to initial levels after 1-day rehydration in seawater, suggesting strong tolerance to dehydration. Furthermore, S. fusiforme appeared to tolerate a broad range of salinity (i.e. 15–50 psu) during six days of culture; however, ΔF/F_m' declined when salinity was <10 and 60 psu. Strong tolerance to dehydration and salinity stress likely provides S. fusiforme an advantage that allows it to flourish in the intertidal habitat.     

Photosynthetic activity including the thermal‐ and chilling‐light sensitivities of a temperate Japanese brown alga Sargassum macrocarpum

The effects of irradiance, temperature, thermal‐ and chilling‐light sensitivities on the photosynthesis of a temperate alga, Sargassum macrocarpum (Fucales) were determined by a pulse amplitude modulation (PAM)‐chlorophyll fluorometer and dissolved oxygen sensors. Oxygenic photosynthesis–irradiance curves at 8, 20, and 28°C revealed that the maximum net photosynthetic rates (NP _max) and saturation irradiance were highest at 28°C, and lowest at 8°C. Gross photosynthesis and dark respiration determined over a range of temperatures (8–36°C) at 300 μmol photons m^?2 s^?1 revealed that the maximum gross photosynthetic rate (GP_max) occurred at 27.8°C, which is consistent with the highest seawater temperature in the southern distributional limit of this species in Japan. Additionally, the maximum quantum yields of photosystem II (F _v/F _m) during the 72‐h temperature exposures were stable at 8–28°C, but suddenly dropped to zero at higher temperatures, indicative of PSII deactivation. Continuous exposure (12 h) to irradiance of 200 (low) and 1000 (high) μmol photons m^?2 s^?1 at 8, 20, and 28°C revealed greater declines in their effective quantum yields (Φ _PSII) under high irradiance. While Φ _PSII under low irradiance were very similar with the initial F _v/F _m under 20 and 28°C, values rapidly decreased with exposure duration at 8°C. At this temperature, F _v/F _m did not recover to initial values even after 12 h of dark acclimation. Final F _v/F _m of alga at 28°C under high irradiance treatment also did not recover, suggesting its sensitivity to photoinhibition at both low and high temperatures. These photosynthetic characteristics reflect both the adaptation of the species to the general environmental conditions, and its ability to acclimate to seasonal changes in seawater temperature within their geographical range of distribution.     

Photosynthetic responses to photosynthetically active radiation and temperature including chilling‐light stress on the heteromorphic life history stages of a brown alga,Cladosiphon okamuranus (Chordariaceae) from Ryukyu Islands,Japan

Photosynthetic responses to temperature and photosynthetically active radiation (PAR) were investigated on the heteromorphic life history stages (macroscopic and microscopic stages) of an edible Japanese brown alga, Cladosiphon okamuranus from the Ryukyu Islands. Measurements were carried out by using optical dissolved oxygen sensors and a pulse‐amplitude modulated fluorometer. Maximum net photosynthetic rates and other parameters of the Photosynthesis – PAR curves at 28°C were somewhat similar in both life history stages, without characteristic photoinhibition at 1000 μmol photons m^?2 s^?1. Results of oxygenic gross photosynthesis and dark respiration experiments over a temperature range of 8–40°C revealed similar temperature optima for both stages (29.7°C, macroscopic stage; 30.3°C, microscopic stage), which support their observed occurrences in the habitat during summer. Maximum quantum yields of photosystem II (PSII ) (F _v /F _m ) were relatively stable at low temperatures with the highest at 15.1°C for the macroscopic stage and at 16.5°C for the microscopic stage; but dropped at higher temperatures especially above 28°C. Continuous exposures (6 h) to 200 and 1000 μmol photons m^?2 s^?1 at 8, 16, and 28°C revealed greater depressions in effective quantum yields of PSII (Φ _PSII ) of the microscopic stage at 8°C, as well as its F _v /F _m that barely increased after 6 h of dark acclimation. Whereas post‐dark acclimation F _v /F _m of both stages exposed to low PAR fairly recovered at 28°C, suggesting their photosynthetic tolerance to such high temperature. Under natural conditions, both heteromorphic stages of C. okamuranus may persist throughout the year in this region. Beyond its northern limit of distribution, the microscopic stage of this species may suffer from photodamage, as enhanced by low winter temperatures; hence, its restricted occurrence.     

Phenology,irradiance and temperature characteristics of a freshwater red alga,Nemalionopsis tortuosa (Thoreales), from Kagoshima,southern Japan

Phenology, irradiance and temperature characteristics of a freshwater benthic red alga, Nemalionopsis tortuosa Yoneda et Yagi (Thoreales), were examined from Kagoshima Prefecture, southern Japan for the conservation of this endemic and endangered species. Field surveys confirmed that algae occurred in shaded habitats from winter to early summer, and disappeared during August through November. A net photosynthesis–irradiance (P–E) model revealed that net photosynthetic rate quickly increased and saturated at low irradiances, where the saturating irradiance (E_k) and compensation irradiance (E_c) were 10 (8–12, 95% credible interval (CRI)) and 8 (6–10, 95% CRI) μmol photon m^?2 s^?1, respectively. Gross photosynthesis and dark respiration was determined over a range of temperatures (8–36°C) by dissolved oxygen measurements, and revealed that the maximum gross photosynthetic rate was highest at 29.5 (27.4–32.0, 95%CRI) °C. Dark respiration also increased linearly when temperature increased from 8°C to 36°C, indicating that the increase in dark respiration at higher temperature most likely caused decreases in net photosynthesis. The maximum quantum yield (Fv/Fm) that was determined using a pulse amplitude modulated‐chlorophyll fluorometer (Imaging‐PAM) was estimated to be 0.51 (0.50–0.52, 95%CRI) and occurred at an optimal temperature of 21.7 (20.1–23.4, 95%CRI) °C. This species can be considered well‐adapted to the relatively low natural irradiance and temperature conditions of the shaded habitat examined in this study. Our findings can be applied to aid in the creation of a nature‐reserve to protect this species.     

Structure-activity relationship of a neurite outgrowth-promoting substance purified from the brown alga,Sargassum macrocarpum, and its analogues on PC12D cells

The structure-activity relationship of a neurite outgrowth-promotingsubstance (designated as MC14) from the brown alga, Sargassummacrocarpum, was analysed. Eight synthetic carotenoids and1,4-benzoquinone were used to determine the moiety of the MC14molecule structurally responsible for the nerve growth factor(NGF)-mediated neurite outgrowth-promoting activity on PC12D cells.The bioassays showed that none of these carotenoids exhibitedNGF-potentiating activity. In contrast, 1,4-benzoquinone enhancedsignificantly NGF-mediated neurite outgrowth from PC12D cells, therebeing a 260% increase over the activity of negative control (10 ngmL^-1 NGF). The effect of quinone structure on NGF-potentiatingactivity, when examined using 12 naturally occurring quinones,demonstrated that lawsone, alizarin and lapachol significantly enhancedNGF-mediated neurite outgrowth by 329%, 325% and 265%,respectively, of that in the negative control. These results show thatquinone is the structural moiety of MC14 molecule responsible for theneurite outgrowth-promoting activity. In addition, the hydroxyl groupbonded to quinone had a significant effect on neuritogenic activity. Thebearing of a hydroxyl group at the 1'-position of benzoquinone, and thebearing of two hydroxyl groups at the 1' and 2'-positions of anthraquinone,played a crucial role in enhancing the neurite outgrowth-promoting actionof NGF.     

Effect of irradiance and temperature on the photosynthesis of a cultivated red alga,Pyropia tenera (= Porphyra tenera), at the southern limit of distribution in Japan

The effect of irradiance and temperature on the photosynthesis of the red alga, Pyropia tenera, was determined for maricultured gametophytes and sporophytes collected from a region that is known as one of the southern limits of its distribution in Japan. Macroscopic gametophytes were examined using both pulse‐amplitude modulated fluorometry and/or dissolved oxygen sensors. A model of the net photosynthesis–irradiance (P‐E) relationship of the gametophytes at 12°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 46 μmol photons m^?2 s^?1, and the compensation irradiance was 9 μmol photons m^?2 s^?1. Gross photosynthesis and dark respiration for the gametophytes were also determined over a range of temperatures (8–34°C), revealing that the gross photosynthetic rates of 46.3 μmol O₂ mg_chl‐a^?1 min^?1 was highest at 9.3 (95% Bayesian credible interval (BCI): 2.3–14.5)°C, and the dark respiration rate increased at a rate of 0.93 μmol O₂ mg_chl‐a^?1 min^?1°C^?1. The measured dark respiration rates ranged from ?0.06 μmol O₂ mg_chl‐a^?1 min^?1 at 6°C to ?25.2 μmol O₂ mg_chl‐a^?1 min^?1 at 34°C. The highest value of the maximum quantum yield (Fv/Fm) for the gametophytes occurred at 22.4 (BCI: 21.5–23.3) °C and was 0.48 (BCI: 0.475–0.486), although those of the sporophyte occurred at 12.9 (BCI: 7.4–15.1) °C and was 0.52 (BCI: 0.506–0.544). This species may be considered well‐adapted to the current range of seawater temperatures in this region. However, since the gametophytes have such a low temperature requirement, they are most likely close to their tolerable temperatures in the natural environment.     

Studies on the salinity and desiccation tolerances of Helice tridens and Helice japonica (Decapoda: Grapsidae)

In the Shigenobu River Estuary (33 ° 48′ 18″ N, 132 ° 41′ 10″ E), Matsuyama (Japan), Helice tridens inhabits the mid-intertidal zone to the limit of the high tide, while H. japonica is found around the mid-intertidal zone. In addition, H. japonica is distributed further downstream than H. tridens. These differences suggest that H. japonica has a lower salinity and desiccation tolerance than H. tridens. Laboratory experiments on salinity tolerance confirmed the higher tolerance of H. tridens compared to H. japonica. Helice tridens survived at least a week under fresh water conditions, whereas most of the H. japonica died. Helice tridens was shown to be more able to tolerate desiccation than H. japonica, through behavioral, not physiological, adaptation to dry conditions. The present results demonstrate a stronger adaptation of H. tridens to semi-terrestrial and/or freshwater environments than H. japonica. This revised version was published online in July 2006 with corrections to the Cover Date.     

Freezing and desiccation injury resistance in the filamentous green alga Klebsormidium from the Antarctic, Arctic and Slovakia

The freezing and desiccation tolerance of 12 Klebsormidium strains, isolated from various habitats (aeroterrestrial, terrestrial, and hydro-terrestrial) from distinct geographical regions (Antarctic — South Shetlands, King George Island, Arctic — Ellesmere Island, Svalbard, Central Europe — Slovakia) were studied. Each strain was exposed to several freezing (−4°C, −40°C, −196°C) and desiccation (+4°C and + 20°C) regimes, simulating both natural and semi-natural freeze-thaw and desiccation cycles. The level of resistance (or the survival capacity) was evaluated by chlorophyll a content, viability, and chlorophyll fluorescence evaluations. No statistical differences (Kruskal-Wallis tests) between strains originating from different regions were observed. All strains tested were highly resistant to both freezing and desiccation injuries. Freezing down to −196°C was the most harmful regime for all studied strains. Freezing at −4°C did not influence the survival of studied strains. Further, freezing down to −40°C (at a speed of 4°C/min) was not fatal for most of the strains. RDA analysis showed that certain Antarctic and Arctic strains did not survive desiccation at +4°C; however, freezing at −40°C, as well as desiccation at +20°C was not fatal to them. On the other hand, other strains from the Antarctic, the Arctic, and Central Europe (Slovakia) survived desiccation at temperatures of +4°C, and freezing down to −40°C. It appears that species of Klebsormidium which occupy an environment where both seasonal and diurnal variations of water availability prevail, are well adapted to freezing and desiccation injuries. Freezing and desiccation tolerance is not species-specific nor is the resilience only found in polar strains as it is also a feature of temperate strains. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia. This paper is dedicated to the memory of the late Dr. Bohuslav Fott (1908–1976), Professor of Botany at the Charles University in Prague, to mark the centenary of his birth.     

Age- and size-based morphological comparison between the brown alga Sargassum macrocarpum (Heterokonta; Fucales) from different depths at an exposed coast in northern Kyoto, Japan

Although large perennial brown algae are known to show great morphological plasticity responding to specific environmental factors such as depth and wave exposure, there are few reports showing this morphological variability taking into account age or size composition. Here, we conducted age- and size-based morphological comparison between the perennial brown alga Sargassum macrocarpum C. Agardh from their upper depth limit, middle depth, and lower depth limit at an exposed coast in northern Kyoto, Japan. Model II regression was fitted for the relationships between age or stipe diameter (SD) and morphological variables including SD, holdfast weight (HW), number of main branches (MBN), total weight of main branches (MBW), thallus weight (TW), and thallus length (TL) of 30 specimens collected seasonally from each depth zone. The differences between depths in these regression equations were analyzed using SMATR. Although SD, HW, and MBN of the specimens did not differ between depths under both age- and SD-basis, there were significant differences between depths in MBW, TW, and TL, suggesting that the differences in TW between depths are resulted from differences in MBW. Whereas TW at the lower depth limit was lower than that at the upper depth limit or middle depth in many months, TL at the upper depth limit was shorter than that at the middle depth or lower depth limit in some months. These results suggest that S. macrocarpum at shallower depths tend to have short and bushy morphology, whereas those at deeper depths have long and less bushy morphology.     

The photosynthetic performance of a cultivated Japanese green alga Caulerpa lentillifera in response to three different stressors,temperature, irradiance,and desiccation

The effects of temperature, irradiance, and desiccation on the photosynthesis of a cultivated Japanese green alga Caulerpa lentillifera (Caulerpaceae) were determined by a pulse amplitude modulation (PAM)-chlorophyll fluorometer and dissolved oxygen sensors. The photochemical efficiency in the photosystem II (F_v/F_m and ΔF/F_m') during the 72-h temperature exposures (8, 12, 16, 20, 24, 28, 32, 36, and 40°C) was generally stable at 16–32°C but quickly dropped at lower and higher temperatures. The photosynthesis–temperature curve at 200 μmol photons m^?2 s^?1 also revealed that the maximum gross photosynthesis (GP_max) occurred at 30.7°C (30.5–30.9, 95% highest density credible intervals). Photosynthesis–irradiance curves at 16, 24, and 32°C quickly saturated, then expressed photoinhibition, and revealed that the maximum net photosynthetic rates (NP_max) and saturation irradiance (E_k) were highest at 32°C and lowest at 16°C. Continuous 6-h exposure to irradiances of 200 (low) and 400 (high) μmol photons m^?2 s^?1 at 16, 24, and 32°C expressed greater declines in their ΔF/F_m' at 16°C, revealing chronic chilling-light stress. The response to continuous desiccation (~480 min) under 50% humidity at 24°C showed that ΔF/F_m' dropped to zero at 480-min aerial exposure, and the treatments of more than 60-min desiccation did not return to the initial level even after 24-h subsequent rehydration in seawater. Likewise, ΔF/F_m' fell when the absolute water content (AWC) of the frond dropped below AWC of 90% and mostly did not return to the initial level even after 24-h subsequent rehydration in seawater, signifying a low tolerance to desiccation.

     

The plastome of a brown alga,Dictyota dichotoma

Summary Plastids of the brown algaDictyota dichotoma contain a single homogeneous DNA species which bands at a buoyant density of 1.693 g/cm³ in neutral CsCl equilibrium density gradients. The corresponding nuclear DNA has a density of 1.715 g/cm³. The molecular size of the plastid DNA is 123 kbp as calculated by both electron microscopy of spread intact circular molecules and gel electrophoresis following single and double digestions with various restriction enzymes. A restriction map has been constructed using the endonucleases Sal I, Bam HI, and Bgl II which cleave theDictyota plastome into 6, 12, and 17 fragments, respectively. No large repeated regions, as found in chlorophycean andEuglena plastid DNAs, were detected.Dictyota dichotoma is the first member from the chlorophyll c-line of the algal pedigree for which a physical map of plastid DNA has been established. Dedicated to Professor Dr. W. Stubbe on the occasion of his 65th birthday.     

Effect of desiccation on the photosynthesis of seaweeds from the intertidal zone in Honshu, Japan

Intertidal seaweeds are periodically exposed during low tide and thus experience extreme levels of desiccation. The physiological activity of seaweeds changes during this water loss process. This study examined how desiccation affects the photosynthesis and respiration of seaweeds from different intertidal levels, and whether the ability to retain photosynthesis and respiration rates during desiccation varies among these species. Photosynthesis and respiration rates of 12 species of seaweeds were measured under various levels of desiccation, using an infrared CO₂ gas analyzer. High levels of drought negatively affected photosynthesis, while most species showed initial rises in photosynthetic rates. The ability to retain photosynthesis and respiration activities under desiccation conditions varied among species. These physiological responses were not related to the intertidal level at which these species occur, but to their ability to prevent water loss. The species with lower rates of water loss had slower declines in the rate of photosynthesis and respiration.     

Isofuhalols,a type of phlorotannin from the brown alga Chorda filum

From an acetylated fraction of an extract of Chorda filum, phloroglucinol triacetate and six 2-to 5-ringed phloroglucinol-derived polyhydroxyphenyl ethers were isolated and their structures elucidated. Among these are three isofuhalols, compounds of a new structural type.     

Seasonal and diel changes in photosynthetic activity of the snow alga Chlamydomonas nivalis (Chlorophyceae) from Svalbard determined by pulse amplitude modulation fluorometry

The seasonal and diel dynamics of the physiological state and photosynthetic activity of the snow alga Chlamydomonas nivalis were investigated in a snowfield in Svalbard. The snow surface represents an environment with very high irradiation intensities along with stable low temperatures close to freezing point. Photosynthetic activity was measured using pulse amplitude modulation fluorometry. Three types of cell (green biflagellate vegetative cells, orange spores clustered by means of mucilaginous sheaths, and purple spores with thick cell walls) were found, all of them photosynthetically active. The pH of snow ranged between 5.0 and 7.5, and the conductivity ranged between 5 and 75 microS cm(-1). The temperature of snow was stable (-0.1 to +0.1 degrees C), and the incident radiation values ranged from 11 to 1500 micromol photons m(-2) s(-1). The photosynthetic activity had seasonal and diel dynamics. The Fv/Fm values ranged between 0.4 and 0.7, and generally declined over the course of the season. A dynamic response of Fv/Fm to the irradiance was recorded. According to the saturating photon fluence values Ek, the algae may have obtained saturating light as deep as 3 cm in the snow when there were higher-light conditions, whereas they were undersaturated at prevalent low light even if on the surface.     

The effect of photosynthetically active radiation and temperature on the photosynthesis of two Vietnamese species of Sargassum,S. mcclurei and S. oligocystum,based on the field and laboratory measurements

SUMMARY The effects of photosynthetically active radiation (PAR) and temperature on the photosynthesis of two Vietnamese brown algae, Sargassum mcclurei and S. oligocystum (Fucales), were determined by field and laboratory measurements. Dissolved oxygen sensors and pulse‐amplitude modulated (PAM) fluorometry were used for the measurements of photosynthetic efficiency. A Diving‐PAM revealed that underwater measurements of the effective quantum yield (Φ _PSII ) of both species declined with increasing incident PAR, with minimum Φ _PSII occurring during noon to early afternoon. Φ _PSII recovered in the evening, indicating photo‐adaptation to excessive PAR. In laboratory experiments, Φ _PSII also decreased under continuous exposure to 1000 μmol photons m^?2 s^?1; and full recovery occurred after 12 h of dark acclimatization. The net photosynthesis – PAR experiments of S. mcclurei and S. oligocystum conducted at 28°C revealed that the net photosynthetic rate quickly increased at PAR below the saturation irradiance of 361 and 301 μmol photons m^?2 s^?1 and nearly saturated to maximum net photosynthetic rates of 385 and 292 μg O₂ g_ww ^{? 1} min^?1 without photoinhibition, respectively. Gross photosynthesis and dark respiration experiments determined over a range of temperatures (12–40°C), revealed that the maximum gross photosynthetic rates of 201 and 147 μg O₂ g_ww ^{? 1} min^?1 occurred at 32.9 and 30.7°C for S. mcclurei and S. oligocystum, respectively. The dark respiration rates increased exponentially over the temperature ranges examined. The estimated maximum value of the maximum quantum yield occurred at 19.3 and 20.0°C and was 0.76 and 0.74, respectively. Similar to the natural habitat of the study site, these two species tolerated the relatively high temperatures and broad range of PAR. The ability of these species to recover from exposure to high PAR is one of the mechanisms that allow them to flourish in the shallow water environment.     

The effect of temporal variability in salinity on the invasive red alga Gracilaria vermiculophylla

Non-native, invasive species are often characterized by being tolerant to environmental stressors, leaving them more fit relative to native species. The red alga Gracilaria vermiculophylla originates from the NW Pacific but has recently spread along the coastlines of Western Europe, where it has become abundant in many shallow, soft-bottom estuaries. Salinity is important for the local and regional distribution of algae. The distribution of G. vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under such conditions. Little, however, is known about the ecophysiology of G. vermiculophylla and it is therefore difficult to predict its spread and future distribution. Laboratory experiments with G. vermiculophylla showed that steady-state salinity above 15?psu was optimal for growth and that the growth rate was reduced at salinities below 15?psu. Variable salinity reduced the growth rate and larger oscillations were more stressful than small ones. Exposure to very low salinity (0–5?psu) was stressful for the alga and algae exposed to these low levels for 2–4 days were unable to recover fully. Gracilaria vermiculophylla did not seem to perform better in hyposaline conditions than many native, estuarine species. The present distribution of G. vermiculophylla in Scandinavia can be explained well by its response to salinity, but this may not explain its present success relative to many naturally occurring algal species.     

The photosynthesis of Dunaliella parva Lerche as a function of temperature,light and salinity

The photosynthetic behaviour of Dunaliella parva Lerche from the athalassic lagoon of Fuente de Piedra (Málaga, Southern Spain) was studied experimentally at three NaCl concentrations (1, 2 and 3 M), five temperatures (15, 23, 31, 38 and 42°C) and nine different irradiances between 82 and 891 mol m^–2 s^–1. Results are analyzed to define the best growing conditions for the algae. D. parva shows the highest photosynthetic rates at a NaCl molarity of 2 M, under a moderate light intensity (600 mol m^–2 s^–1) at 31°C. Above this light intensity a clear photoinhibition of the photosynthesis was found at 2 M and 3 M of NaCl. D. parva is a halotolerant and a thermoresistant species as evidenced by its net photosynthesis rate and positive values of oxygen evolution at 42°C.Two methods for modelling photosynthesis vs. irradiance curves are discussed. The first is a single model, based on third-order polynomial equations, and the second is double model, based on hyperbolical Michaelis-Menten type functions and negative exponential to define photoinhibition.     

Bacterial communities of some brown and red algae from Peter the Great Bay, the Sea of Japan

The structure of microbial communities of brown algae, red algae, and of the red alga Gracilaria verrucosa, healthy and affected with thallus rot, were comparatively investigated; 61 strains of heterotrophic bacteria were isolated and characterized. Most of them were identified to the genus level, some Vibrio spp., to the species level according to their phenotypic properties and the fatty acid composition of cellular lipids. The composition of the microflora of two species of brown algae was different. In Chordaria flagelliphormis, Pseudomonas spp. prevailed, and in Desmarestia viridis, Bacillus spp. The composition of the microflora of two red algae, G. verrucosa and Camphylaephora hyphaeoides, differed mainly in the ratio of prevailing groups of bacteria. The most abundant were bacteria of the CFB cluster and pseudoalteromonads. In addition, the following bacteria were found on the surface of the algae: Sulfitobacter spp., Halomonas spp., Acinetobacter sp., Planococcus sp., Arthrobacter sp., and Agromyces sp. From tissues of the affected G. verrucosa, only vibrios were isolated, both agarolytic and nonagarolytic. The existence of specific bacterial communities characteristic of different species of algae is suggested and the relation of Vibrio sp. to the pathological process in the tissues of G. verrucosa is supposed.