Ecophysiological characteristics of four intertidal marine macroalgae during emersion along Shantou coast of China, with a special reference to the relationship of photosynthesis and CO2

Intertidal marine macroalgae experience periodical exposures during low tide due to their zonational distribution. The duration of such emersion leads to different exposures of the plants to light and aerial CO2, which then affect the physiology of them to different extents.The ecophysiological responses to light and CO2 were investigated during emersion in two red algae Gloiopeltis furcata and Gigartina interrnedia, and two brown algae Petaloniafascia and Sargassum hemiphyllum, growing along the Shantou coast of China. The light-saturated net photosynthesis in G. furcata and P. fascia showed an increase followed by slightly desiccation, whereas that in G.interrnedia and S. hemiphyllum exhibited a continuous decrease with water loss. In addition, the upper-zonated G. furcata and P. fascia,exhibited higher photosynthetic tolerance to desiccation and required higher light level to saturate their photosynthesis than the lower-zonated G. interrnedia and S. hemiphyllum. Desiccation had less effect on dark respiration in these four algae compared with photosynthesis. The light-saturated net photosynthesis increased with increased CO2 concentrations, being saturated at CO2 concentrations higher than the present atmospheric level in G. furcata, G. intermedia and S. hemiphyllum during emersion. It was evident that the relative enhancement of photosynthesis by elevated CO2 in those three algae increased, though the absolute values of photosynthetic enhancement owing to CO2 increase were reduced when the desiccation statuses became more severe. However, in the case of desiccated P. fascia (water loss being greater than 20 %), light saturated net photosynthesis was saturated with current ambient atmospheric CO2 level. It is proposed that increasing atmospheric CO2 will enhance the daily photosynthetic production in intertidal macroalgae by varied extents that were related to the species and zonation.     

有毒赤潮藻及其毒素的危害与检测

海洋中可引发赤潮的藻类约有300种,其中有毒赤潮藻为80种左右。现已知道的赤潮藻主要毒素有麻痹性贝毒、腹泻性贝毒、记忆缺失性贝毒、神经性贝毒、西加鱼度和溶血性毒素,前5种毒素的结构已经基本得到证实。有毒赤潮藻的毒素可以在海洋生物体内积累,人类误食含有藻毒素的食品时可能中毒,严重者还可能死亡。海洋有毒赤潮藻及其毒素的检测已经成为当今全球赤潮研究和监测的重要内容之一,可以通过形态学分类方法、分子生物学技术(遗传探针)和免疫学检测技术对有毒赤潮藻进行检测;可以通过生物学、物理化学检测方法和神经受体结合、免疫学检测技术对赤潮藻毒素进行检测。     

珊瑚藻-孔石藻（Porolithon onkodes）对海水温度升高与pH值降低的响应

Coralline algae(CA),a type of primary calcifying producer presented in coastal ecosystems,are considered one of the highly sensitive organisms to marine environmental change.However,experimental studies on coralline algae responses to elevated seawater temperature and reduced pH have documented either contradictory or opposite results.In this study,we analysed the growth and physiological responses of coralline algae Porolithon onkodes to the elevated temperature(30.8°C)and reduced pH(7.8).The aim of this analysis was to observe the direct and combined effects,while elucidating the growth and photosynthesis in this response.It was demonstrated that the algae thallus growth rate and photosynthesis under elevated temperature were depressed by 21.5%and 14.9%respectively.High pCO2 enhanced the growth and photosynthesis of the thallus at ambient temperature,while they were deceased when both temperature and pCO2 were elevated.CA is among the most sensitive organisms to ocean acidification(OA)because of their precipitate high Mg-calcite.We hypothesize that coralline algae could increase their calcification rate in order to counteract the effects of moderate acidification,but offset by the effect of elevated temperature.Accordingly,our results also support the conclusion that global warming(GW)is a stronger threat to algal performance than OA.Our findings are also proposed that coralline algae may be more resilient under OA than GW.     

Feeding behavior in Caribbean surgeonfishes varies across fish size,algal abundance,and habitat characteristics

Feeding behavior of coral reef fishes often determines their species‐specific ecological roles. We studied the two most common Caribbean surgeonfishes (Acanthurus coeruleus and Acanthurus tractus) to examine their species‐specific grazing rates and feeding preferences and how these differed with environmental context. We quantified the feeding activity of both surgeonfishes at four spur and groove reefs in the Florida Keys, USA, that varied in fish abundance, rugosity, algal community composition, and sediment loading. Overall, A. tractus fed twice as fast as A. coeruleus. Both species selected for turf algae but avoided feeding on turf algae that had become laden with sediment. Selectivity for upright macroalgae was more complex with A. tractus targeting Dictyota spp., while A. coeruleus avoided Dictyota spp. relative to the alga's abundance. Both species selected for epiphytes growing on other organisms such as macroalgae and sponges. However, several of these feeding patterns changed with ontogeny. For example, larger individuals of both species fed more frequently on long, sediment‐laden algal turf and less frequently on Dictyota spp. compared to smaller sized individuals. In addition, A. tractus also increased its preference for upright calcareous algae as they attained larger sizes. Overall, the disparity in feeding preferences of surgeonfishes likely indicates subtle differences in species‐specific ecological roles. Both A. coeruleus and A. tractus likely prevent development of turf algae and thus maintain algal communities in the early stages of succession. Additionally, A. tractus may also help reduce macroalgal abundance by targeting common macroalgal species.     

Competition within the marine microalgae over the polar dark period in the Greenland Sea of high Arctic

Abstract-With the onset of winter, polar marine microalgae would have faced total darkness for aperiod of up to 6 months. A natural autumn community of Arctic sea ice microalgae was collected fordark survival experiments from the Greenland Sea during the ARKTIS-XI/2 Expedition of RV Po-larstern in October 1995. After a dark period of 161 days, species dominance in the algal assemblagehave changed from initially pennate diatoms to small phytoflagellates (<20μm). Over the entire darkperiod, the mean algal growth rate was-0.01 d~(-1). Nearly all diatom species had negative growthrates, while phytoflagellate abundance increased. Resting spore formation during the dark period was ob-served in less than 4.5% of all cells and only for dinoflagellates and the diatom Chaetoceros spp. We as-sume that facultative heterotrophy and energy storage are the main processes enabling survival during thedark Arctic winter. After an increase in light intensity, microalgal cells reacted with fast growth withindays. Phytoffa     

Seasonal variation of molluscan assemblages in different strata of photophilous algae in the Alboran Sea (western Mediterranean)

The seasonal dynamics of molluscan assemblages inhabiting the algal fronds and the underlying sediment of photophilous algae were analyzed in NW Alboran Sea between July 2007 and April 2008. Molluscs were sampled using SCUBA in two different algal stands (7 km apart) dominated by the brown algae Stypocaulon scoparium, and following an inter-strata sampling protocol consisting in first sampling the algal fronds and then the underlying substratum. The studied algal stands harbored a highly biodiverse malacofauna, with 193 species identified. Assemblages on algal fronds and sediment displayed significant seasonal variations, being more apparent on the fronds, with maximum species richness, abundance and Shannon–Wiener diversity values in summer in both strata. The between-strata differences were also observed in the trophic structure of the assemblages: algal fronds were quantitatively dominated by microalgae or periphyton grazers and the sediment by detritivores and plankton and seston feeders. The high dominance of some species resulted in lower values of diversity and evenness in autumn in the sediment (e.g. Nodulus contortus and Bittium reticulatum) and in spring on the fronds (e.g. Rissoa guerinii and Musculus costulatus). The seasonal variability of the assemblages was mainly related to the population dynamics of dominant species (22 spp. displaying dominance values > 1%) (i.e. recruitment events, high mortality rates of juveniles and/or migrations among habitats). Other factors analyzed were (1) the vegetative cycle of algae, which played an important role in the abundance of some dominant epifaunal grazers, with high abundance and species richness values coinciding with high biomass of algae; and (2) the percentage of organic matter in the sediment, which was related to the abundance changes of some depositivores species. Further conservation strategies for macroalgal stands should be taken into consideration, as this type of photophilous habitat harbors rich associated faunistic communities and it is not generally considered in conservation lists of habitats to be protected.     

不同粒径TiO_2颗粒对海洋微藻的毒性效应

本实验以新月菱形藻为受试生物,研究了低浓度不同粒径TiO2颗粒(21nm、60nm和400nm)对海洋微藻生长、抗氧化酶活性(超氧化物歧化酶SOD、过氧化氢酶CAT和过氧化物酶POD)、脂质过氧化产物(MDA)含量的影响,并测定了相应的活性氧自由基(ROS)的含量,初步探讨了TiO2颗粒对海洋微藻的作用机制。结果表明,1mg/L TiO2颗粒对新月菱形藻生长的抑制作用随着粒径的减小而逐渐增强,第48h、72h、96h呈现出显著的纳米效应。TiO2颗粒可以诱导藻细胞内ROS的含量增加,对藻细胞产生氧化胁迫,新月菱形藻的抗氧化酶活性发生应激响应,以清除过量的ROS,但剩余的ROS对藻细胞产生氧化损伤,导致MDA含量升高,并且纳米级TiO2颗粒对新月菱形藻的氧化损伤大于微米级颗粒。在不同粒径TiO2颗粒的胁迫下,藻细胞SOD和CAT活性的响应也存在差异。本研究将为开展人工纳米材料对海洋生态系统影响的潜在风险评估提供科学依据。     

The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs

Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of trophic interactions (i.e. herbivory by fishes and sea urchins) and spatial competition (between algae and coral) on algal community structure of reefs surrounding two Hawaiian Islands that vary in their level of human impacts. Reef‐building organisms (corals and crustose coralline algae) were less abundant and turf algae were more abundant on Maui as compared to Lanai, where human impacts are lower. In contrast to previous studies, we found no evidence that macroalgae increased with human impacts. Instead, low turf and macroalgal abundance were best explained by the interactive effects of coral cover and sea urchin abundance. Fishing sea urchin predators appeared to have cascading effects on the benthic community. The absence of sea urchin predators and high sea urchin densities correspond to a disproportionately high abundance of turf and crustose coralline algae. We propose that high turf algal abundance is a better indicator of reef decline in Hawaii than high macroalgal abundance because turf abundance was highest on reefs with low coral cover and few fish. The results of this study emphasize that understanding changes in community composition are context‐dependent and that not all degraded reefs look the same.     

山东荣成马山里海域大型藻类群落结构时空变化研究

山东半岛东端以岩基海岸为主,而浅海多为岩礁底质,适宜大型藻类生长。为探究该海域的大型藻类群落结构特征,于2018年11月(秋)、2019年2月(冬)、5月(春)和8月(夏)对山东荣成马山里海域的3个典型生境(草床区、天然礁区和泥沙区)中的大型藻类进行了调查。结果显示:3种生境共鉴定出大型藻类23种,其中红藻门15属15种,褐藻门3属4种,绿藻门3属4种。物种数最高值出现在天然礁区(22种),最低值出现在泥沙区(12种)。生物量最高值为春季草床区(1 567.44±21.29) g·m^-2、最低值为秋季的泥沙区(594.45±107.06) g·m^-2。大型藻类优势种在不同生境、不同季节不同:草床生境为小珊瑚藻(Corallina pilulifera),在4个季节中均占绝对优势;礁区为绿藻向红藻、褐藻变化;泥沙区为从红藻到褐藻变化。Pielow均匀度指数的最高值在3个生境中相近且均出现在冬季;多样性指数最高值、最低值分别出现在礁区与泥沙区; Margalef丰富度指数的最高值出现在秋季的礁区,而最低值出现在夏季的泥沙区;聚类与排序结果表明,大...     

Distribution and feeding patterns of juvenile parrotfish on algal‐dominated coral reefs

By the consumption of algae, parrotfishes open space for young coral settlement and growth, thus playing a central role on the maintenance of coral reefs. However, juvenile parrotfish ecology is often overlooked due to the difficulty discerning species during this phase. Herein, we present the first attempt to investigate changes in habitat use and diet that happen to juveniles of the Redeye parrotfish Sparisoma axillare, focusing on four zones within an algal‐dominated reef: the macroalgal beds, back reef, reef flat, and fore reef. Smaller S. axillare juveniles (<5 cm) preferred to inhabit the macroalgal beds and the reef flat, whereas juveniles larger than 5 cm were more abundant in the back and fore reefs due to distinct post‐settlement habitat conditions. Aggressive interactions with the territorial damselfish Stegastes fuscus were the primary driving factor of juvenile distribution and feeding rates. Attack rates increased with juvenile size and the lowest bite rates were observed in zones with higher densities of territorial damselfish. In previous studies, the persistence of parrotfish recruits in habitats dominated by damselfish was reduced, but newly settled parrotfish occurred more densely within the damselfish domain by behaving as a cryptic reef fish. As these juveniles grew, their bite rates increased, a change associated with a shift from cryptic to roving behavior. Feeding preferences were determined by substrate cover, where juveniles fed on available food sources in each habitat. Juveniles relied on jointed calcareous algae in habitats dominated by these algae, a pattern not observed for thick leathery algae. Filamentous algae were the preferred food for smaller fish; for individuals greater than 10 cm, a higher ingestion of sand was observed. Most studies evaluating the functional role of parrotfish do not consider species feeding preferences. However, the potential for a species to turn an impacted reef back to a coral‐dominated phase is influenced by their food selection, which is dependent on the algal species composition.     

大管岛礁区潮下带大型底栖海藻群落的初步研究

1990年5月和11月对大管岛礁区潮下带大型底栖海藻进行了两次定量调查。共采到23种大型海藻，其群落构成以红藻类占优。海藻种类的区系温度性质属明显的温水性区系。5月份平均生物量为240．939／m2，11月份平均生物量为164．399／m2。两季度月都以岛西侧的D7断面平均生物量最高，分别为820．159／m2和472．509／m2。就垂直分布而言，1—2米水层内海藻分布密度最高，达527．549／m2。优势种为海蒿子和石花菜。     

The occurrence and depth penetration of macroalgae along environmental gradients in the northern Baltic Sea

Eutrophication is known to affect the community structure of macroalgae by e.g. decreasing the depth penetration of species and by shifting dominance from perennial to annual species. However, there is substantial lack of knowledge in the Baltic Sea regarding the distribution of many of the macroalgal species, how natural environmental factors affect their occurrence and how they respond to eutrophication. As macroalgae are used as indicators of the quality of the sea areas in the EU legislation (Water Framework Directive, Marine Strategy Framework Directive), this kind of knowledge is essential. The aim of this study was to determine which variables were related to variation in species occurrence and their lower limit of occurrence in the Finnish marine area. The study was carried out on data from five study areas along the Finnish coastline and included about 30 taxa. Our results showed that both the macroalgal communities and the occurrence (presence/absence) of most of the species differed between the study areas and that the differences were mainly related to salinity and exposure, although also eutrophication related factors played a role. Of the perennial species, eutrophied conditions seemed to favour only the occurrence of Sphacelaria arctica and Polysiphonia fucoides. Secchi depth was important in determining the lower limit of occurrence of brown and red algal species. However, Secchi depth was rarely the only factor causing variation in the lower limit of occurrence as also exposure, salinity and slope of the shore affected it. We conclude that in the northern Baltic Sea, the taxonomic composition of the macroalgal communities is not a very useful indicator of eutrophication as perennial species seem to tolerate rather eutrophied conditions, when suitable substrate is available. The lower limit of occurrence of many of the brown and red algal species is a good indicator of eutrophication but due to lack of suitable substrate in more eutrophied areas, especially in the depths where light becomes limiting, it is only applicable in the middle and outer archipelago areas. Furthermore, when planning monitoring programmes or setting thresholds for evaluating the ecological status of the sea, the natural variation in the lower limit of occurrence of macroalgae across sea areas is problematic and should carefully be taken into account.     

Exudation and decomposition of chromophoric dissolved organic matter (CDOM) from some temperate macroalgae

The quantity of chromophoric or coloured dissolved organic matter (CDOM) released by eleven species of intertidal and sub-tidal macroalgae commonly found on UK shores was investigated. The subsequent breakdown of CDOM was also measured by exposing collected CDOM samples to light and dark conditions for over two weeks. CDOM absorption properties were compared at a fixed wavelength of 440 nm and across two integrated wave - bands; UV-A (400–315 nm) and UV-B (315–280 nm). Absorption spectra of macroalgal CDOM samples were typically characterized by peaks and shoulders in the UV bands, features which were species specific. The spectral slope, derived using the log-linear method, proved to be very specific to the species and to the effect of light. Slope measurements ranged from 0.010 to 0.027 nm⁻¹, in the range of normal seawater values. Significantly more CDOM was produced by algae which were illuminated, providing evidence for a light driven exudation mechanism. Averaged across all species, exudation in the dark accounted for 63.7% of that in the light in the UV-B band. Interspecific differences in exudation rate encompassed an order of magnitude, with the highest absorption measurements attributable to brown algae. However, some brown algae produced considerably less CDOM (e.g. Pelvetia canaliculata), which were more comparable to the green and red species. Over an exposure time of 16 days, significant photochemical degradation of CDOM was observed using a natural summer sunlight regime, showing that natural solar radiation could be an important removal mechanism for newly produced algal CDOM. Though the most obvious effect was a decrease in absorption, photo-bleaching also caused a significant increase in the spectral slope parameter of 0.004 nm⁻¹.     

Seasonal occurrence and growth of benthic algae in the Patos Lagoon estuary, Brazil

The seasonal occurrence of 94 benthic algal species, including Cyanophyta, was observed on a monthly basis over one year in the Patos Lagoon estuary (32°S, 52°W), Brazil, and showed three patterns of algal periodicity. An aseasonal group of 46 species was present throughout the year and two groups of 24 species each occurred either during summer and fall or winter and spring. The seasonal growth of 55 green, brown and red algae was correlated with monthly variations of salinity, water temperature, daylength and light radiation energy, which were measured daily in the estuary. Summer/fall peak growth was observed in 15 algae most of which correlated significantly with high salinities alone or in combination with other factors during this period. Growth peak of 11 species in winter/spring was principally a function of low water temperatures alone or together with a reduced light regime.Both periodicity of benthic algae and their seasonal growth, as a more sensitive measure of their floristic affinity, demonstrated the presence of cool temperate and tropical elements in this flora typical for warm temperate biogeographic regions. Correlations between seasonal variation of algal growth and selected environmental parameters aided in the evaluation of causal factors for algal seasonality.     

Alterations in seawater pH and CO2 affect calcification and photosynthesis in the tropical coralline alga, Hydrolithon sp. (Rhodophyta)

Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO₂ concentration to 26 μmol kg⁻¹ (by bubbling with air containing 0.9 mbar CO₂) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO₂.     

从藻类化石的垂直分布探讨杭州西湖的演变历程

于１９９４年春在杭州西湖东北面,西面及湖中心小瀛洲３个钻孔共取了７０号岩芯样,经浮选,筛选,以显微镜检鉴定化石藻种,并分析其垂直分布,从而探讨西湖的形成历史,西湖自晚更新世以来的６个化石藻带由下而上依次为：轮藻带,微藻带,微红金颗藻－近缘针杆藻－条纹小环藻带,圆筛藻带,圆筛藻－近缘针杆藻－微红金颗藻桥穹藻－异极藻－短缝藻带和水花束丝藻带,从而反映了西湖的６个发育时期,淡水古湖沼期,淡咸水过渡期,海     

Factors affecting the biokinetics of technetium (95mTc) in marine macroalgae

Technetium (Tc) biokinetics were investigated in marine macroalgae using ^92mTc as tracer. Green and red algae accumulated Tc (VII) to a very low degree (CF ? 1–20); however, a much higher affinity for pertechnetate was found in some brown algal species (CF > 10³). Comparative tests with different species of brown algae revealed that technetium does not accumulate similarly in all species of this group. Moreover, no significant differences in radionuclide uptake were noted between brown algae exposed to Tc in either the IV or VII oxidation states. Bioaccumulation of technetium appears to be a metabolically controlled process since uptake did not occur in heat-killed individuals and both light and temperature significantly enhanced the accumulation of technetium in brown algae. Dissection of Sargassum vulgare following the uptake phase showed that the rapidly growing air bladder, leaf-like laterals and small branches contained higher Tc concentrations and retained a greater fraction of the radioactivity than the older, cylindrical main axis. Pertechnetate retention in two brown algae was found to be significantly different; their biological half-lives for Tc differed by an order of magnitude ($\text{T}{}_{\mathrm{<mtext>b</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{= 19 and 196}\text{days}$). During depuration, loss took place more rapidly from the younger portions of the seaweed, as evidenced by the highest concentration and greatest fraction of Tc retained in the older, cylindrical main axis. Provided certain precautions are taken, brown algae such as Cystoseira compressa and S. vulgare would serve as good bioindicator organisms for the presence of Tc contamination in marine waters.     

Top–down and bottom–up regulation of macroalgal community structure on a Kenyan reef

Top–down and bottom–up regulation in the form of grazing by herbivores and nutrient availability are important factors governing macroalgal communities in the coral reef ecosystem. Today, anthropogenic activities, such as over-harvesting of herbivorous fish and sea urchins and increased nutrient loading, are altering the interaction of these two structuring forces. The present study was conducted in Kenya and investigates the relative importance of herbivory and nutrient loading on macroalgal community dynamics, by looking at alterations in macroalgal functional groups, species diversity (H′) and biomass within experimental quadrats. The experiment was conducted in situ for 42 days during the dry season. Cages excluding large herbivorous fish and sea urchins were used in the study and nutrient addition was conducted using coated, slow-release fertilizer (nitrogen and phosphorous) at a site where herbivory is generally low and nutrient levels are relatively high for the region. Nutrient addition increased tissue nutrient content in the algae, and fertilized quadrats had 24% higher species diversity. Herbivore exclusion resulted in a 77% increase in algal biomass, mainly attributable to a >1000% increase in corticated forms. These results are in accordance with similar studies in other regions, but are unique in that they indicate that, even when prevailing nutrient levels are relatively high and herbivore pressure is relatively low, continued anthropogenic disturbance results in further ecological responses and increased reef degradation.