Diversity in the influence of temperature on the growth rates of freshwater algae, and its ecological relevance

1. Growth rates of seven species of planktonic algae were determined in culture over a range of temperature from 2 to 35 °C. Additional observations on growth and viability were made for 13 species in the temperature range 20–35 °C. 2. There was a wide range of growth rates between species at their optimal temperatures, from 1.7 divisions day^?1 (Asterionella formosa) to 0.3 divisions day^?1 (Ceratium furcoides). 3. There were considerable differences between species for growth at low and high temperature. Certain algae, including the diatom A. formosa and the flagellates Cryptomonas marssonii, Dinobryon divergens and Eudorina unicocca var. unicocca, had growth rates of 0.4 divisions day^?1 or more at 5 °C. The cyanophyte Tychonema (formerly Oscillatoria) bourrellyi, the xanthophyte Tribonema sp., the desmid Staurastrum cingulum and the large dinoflagellate C. furcoides grew poorly or not at all at this temperature. All 21 species tested could grow at 25 °C, but many – including most of the diatoms, some cyanophytes, and all the flagellates – failed to grow persistently at 30 °C. Only Aphanizomenon flos‐aquae survived with moderate increase at 35 °C, a lethal temperature for the other species. 4. The applicability was considered of proposed quantitative formulations of the rate‐temperature relationship. Simple exponential relationships applied only to very limited lower ranges of temperature. The relationship proposed by B?lehrádek was a better fit over a wider temperature range, but still excluded rate‐decline at high temperature. 5. The interspecific differences found are of potential significance for restrictions in natural distributions associated with season, altitude (especially above 500 m) and latitude.     

Microbial to reef scale interactions between the reef-building coral Montastraea annularis and benthic algae

Competition between reef-building corals and benthic algae is of key importance for reef dynamics. These interactions occur on many spatial scales, ranging from chemical to regional. Using microprobes, 16S rDNA pyrosequencing and underwater surveys, we examined the interactions between the reef-building coral Montastraea annularis and four types of benthic algae. The macroalgae Dictyota bartayresiana and Halimeda opuntia, as well as a mixed consortium of turf algae, caused hypoxia on the adjacent coral tissue. Turf algae were also associated with major shifts in the bacterial communities at the interaction zones, including more pathogens and virulence genes. In contrast to turf algae, interactions with crustose coralline algae (CCA) and M. annularis did not appear to be antagonistic at any scale. These zones were not hypoxic, the microbes were not pathogen-like and the abundance of coral-CCA interactions was positively correlated with per cent coral cover. We propose a model in which fleshy algae (i.e. some species of turf and fleshy macroalgae) alter benthic competition dynamics by stimulating bacterial respiration and promoting invasion of virulent bacteria on corals. This gives fleshy algae a competitive advantage over corals when human activities, such as overfishing and eutrophication, remove controls on algal abundance. Together, these results demonstrate the intricate connections and mechanisms that structure coral reefs.     

Effect of inorganic and organic nutrient addition on coral–algae assemblages from the Northern Red Sea

Previous studies in fringing reefs of the Northern Red Sea demonstrated that the in-situ competition of corals and algae in natural assemblages is highly variable between seasons displaying fast overgrowth of corals by benthic reef algae in fall that follows close to equilibrium between both groups of organisms in summer. This may be caused by up to 5-fold higher inorganic nutrient and 6-fold higher organic nutrient concentrations in fall and winter, thereby potentially promoting algae and cyanobacteria growth with concomitant phase shift. A long term mesocosm experiment (duration: 90 days) was conducted in order to study the effect of dissolved inorganic (ammonium, phosphate, nitrate, and mix of all three) and organic (glucose) nutrient addition onto the competitive process in the dominant coral–algae assemblages of the Northern Red Sea involving branching corals of the genus Acropora and a typical consortium of benthic turf algae. Nutrients were added in 3-fold higher concentrations compared to the annual averages, and the parameters algal growth, extension of bleached area on corals, tissue colour change and chlorophyll a concentrations were monitored at regular intervals over experimental duration. This revealed that elevated ammonium concentrations and elevated organic nutrient concentrations stimulate algal growth, while coral tissue pigmentation and chlorophyll a content were significantly decreased. But only in the elevated organic nutrient treatment all effects on corals were significantly pronounced when assembled with benthic turf algae. Supplementary logger measurements revealed that O₂ water concentrations were significantly lower in the elevated organic nutrient mesocosm compared to all other treatments, confirming side-effects on microbial activity. These findings indicate that organic nutrient input into coral reefs can affect physiology and metabolism of both corals and benthic turf algae. Reinforcing interaction between both groups of organisms along with involvement of microbes may facilitate phase shifts in coral reef ecosystems.     

Taxonomic note on some paleozoic marine algae (Uzbekistan, Central Asia)

The paleozoic marine algae of Central Asia were recently investigated and attributed to warm-water and Tethyan microflora. If the majority of the taxa (114 out of 117) were already described from other basins, a few elements merit attention. Two chlorophyte species are new (Atractyliopsis nuratauensis nov. sp., Amarellina moscoviensis nov. sp.) and a new Hoeegonites sp. is left in open nomenclature. The flora also contains representatives of the puzzling Moniliporelleae, a rhodophyte family only reported from Kazakhstan with the genus Furcatoporella. An unusual in situ cluster of calcispheres is also illustrated.     

Treatment of swine manure effluent using freshwater algae: Production, nutrient recovery, and elemental composition of algal biomass at four effluent loading rates

Cultivating algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. The objective of this study was to determine how algal productivity, nutrient removal efficiency, and elemental composition of turf algae change in response to different loading rates of raw swine manure effluent. Algal biomass was harvested weekly from laboratory scale algal turf scrubber units using four manure effluent loading rates (0.24, 0.40, 0.62 and 1.2 L m⁻² d⁻¹) corresponding to daily loading rates of 0.3–1.4 g total N and 0.08–0.42 g total P. Mean algal productivity values increased from 7.1 g DW m⁻² d⁻¹ at the lowest loading rate (0.24 L m⁻² d⁻¹) to 9.4 g DW m⁻² d⁻¹ at the second loading rate (0.40 L m⁻² d⁻¹). At these loading rates, algal N and P accounted for> 90% of input N and 68–76% of input P, respectively. However, at higher loading rates algal productivity did not increase and was unstable at the highest loading rate. Mean N and P contents in the dried biomass increased 1.5 to 2.0-fold with increasing loading rate up to maximums of 5.7% N and 1.8% P at 1.2 L m⁻² d⁻¹. Biomass concentrations of Al, Ca, Cd, Fe, K, Mg, Mn, Mo, Si, and Zn increased 1.2 to 2.6-fold over the 5-fold range of loading rate. Biomass concentrations of Cd, K, Pb, and Si did not increase significantly with loading rate. At the loading rate of 0.40 L m⁻² d⁻¹ (corresponding to peak productivity) the mean concentrations of individual components in the algal biomass were (in mg kg⁻¹): 250 (Al), 4900 (Ca), 0.30 (Cd), 1050 (Fe), 3.4 (Pb), 2500 (Mg), 105 (Mn), 6.0 (Mo), 7,500 (K), and 510 (Zn). At these concentrations, heavy metals in the algal biomass would not be expected to reduce its value as a soil or feed amendment.     

Membrane tubules in the tetraspores of a red alga

Summary Newly released tetraspores of the red algaNitrophyllum punctatum exhibit numerous tubular structures in their peripheral cytoplasm. They are formed by a unit membrane and present an evident continuity with the plasmalemma. Sometimes they are branched. They seem to increase the total cell surface and might be involved in secretion or osmoregulation.     

Vanadium-dependent bromoperoxidases from <Emphasis Type=Italic>Gracilaria</Emphasis> algae

Red algae from the Gulf of Thailand were examined for haloperoxidatic activity. Six species, Gracilaria changii, G. edulis, G. firma, G. fisheri, G. salicornia, and G. tenuistipitata, showed bromoperoxidatic activity. Duplicate polyacrylamide electrophoretic gels showed enzyme activity patterns developed by phenol red staining for bromoperoxidatic activity and by 3,3′-diaminobenzidine staining for peroxidatic activity. All algae gave isoenzymic bromoperoxidatic activity bands and peroxidatic activity bands, but there were peroxidatic and bromoperoxidatic activity bands that did not correspond. The bromoperoxidatic activity of the crude enzyme extracts as well as previously dialyzed enzyme solutions was enhanced significantly by incubation with vanadium pentoxide. The three purified bromoperoxidases from G. fisheri contained vanadium, and their relative activities corresponded to the ratio of vanadium to enzyme. In addition, they were not inhibited by H₂O₂. These data confirm that the enzymes are vanadium bromoperoxidases.     

Chloroplast genome characterization in the red alga Griffithsia pacifica

Summary It has been suggested that cyanobacteria served as the ancestors for rhodophytic algae whose chloroplasts contain chlorophyll a and phycobilins, and that a rhodophyte served as the plastid source for chromophytic plants that contain chlorophylls a and c. Although organellar DNA has been used to assess phylogenetic relatedness among terrestrial plants and green algae whose chloroplasts contain chlorophylls a and b, few data are presently available on the molecular profile of plastid DNA in chromophytes or rhodophytes.In this study the chloroplast genome of the rhodophytic, filamentous alga Griffithsia pacifica has been characterized. DNA was purified from isolated chloroplasts using protease k treatment and sodium dodecyl sulfate lysis followed by density centrifugation in Hoescht-33258 dye-CsCl gradients. Single and double restriction enzyme digests demonstrate that the DNA prepared from purified chloroplasts has a genome size of about 178 kilobase pairs (kb). A restriction map of this chloroplast genome demonstrates that it is circular and, unlike the chloroplast DNA (cpDNA) in most other plants, contains only a single ribosomal DNA operon. DNA was also purified from the mitochondria that co-isolated with chloroplasts. Mitochondrial DNA consists of molecules that range in size from 27 to 350 kb based on restriction endonuclease digestion and electron microscopic analysis.     

Use of the FlowCAM for semi-automated recognition and enumeration of red tide cells (Karenia brevis) in natural plankton samples

Early detection is the most effective way to mitigate the effects of harmful algal blooms (HAB). Cell counts based on examination of microplankton samples using settling chambers and visual inspection with an inverted microscope are tedious and time consuming, and counting precision is generally poor at low cell densities. The FlowCAM is a continuous imaging flow cytometer designed to characterize particles in the microplankton size range (20–200 μm diameter). In this study we examined the ability of the FlowCAM to improve routine monitoring protocols for HAB species by automatically recording information on size and fluorescence per cell. This will eliminate the need to examine cells outside the ranges of these measurements for our target species, Karenia brevis. We also tested the ability of image comparison software to match images of cells in mixed assemblages to images of the target species. For simple mixtures of cultured dinoflagellates, the ability of the image matching software to discriminate target cells varied greatly depending on how similar the two species were in size and shape. When target cells were added to natural plankton samples, the image recognition software correctly identified 80–90% of the target cells, but misidentified 20–50% of non-target cells in the size range of the target species. We conclude that the FlowCAM is less tedious and time-consuming than microscopy, allowing for examination of more cells for greater counting precision. The cell recognition software helps reduce the numbers of cells that must be screened, but images must still be examined by a trained operator to identify the HAB species of interest.     

Cyclic condensed metaphosphates and linear polyphosphates in brown and red algae

The occurrence of linear condensed polyphosphates and cyclic condensed metaphosphates was studied by means of pulse-labeling with ³²P-orthophosphate (3–5 h) in a number of Phaeophyceae species: Pylaiella litoralis, Ilea fascia, Ectocarpus siliculosus and also Rhodophyceae species: Ceramium deslongchampsii, C. rubrum, Rhodomela confervoides, Porphyridium purpureum and P. aerugineum. Twodimensional cellulose thin layer chromatography revealed that in all species studied ³²P-radioactivity was generally present in all oligopolyphosphates containing 2 to 7 phosphate residues, in cyclic metaphosphates (tri-, tetra-, penta- and hexametaphosphates) and in high-molecular-weight condensed phosphates which remained at the starting point. Among the low-molecular-weight condensed inorganic phosphates the trimetaphosphate had a significantly higher specific activity than the other oligophosphates which were separated on the chromatography plates as measured by the direct scanning with a Geiger-Muller counter.The phosphate uptake strongly depends on the internal pool of reserve phosphates of the algae cells. The ³²P-orthophosphate incorporation of the cells is low and sluggish when growning in a synthetic medium or in sea water. Accordingly ³²P appeared preferentially in the low-molecular-weight fractions of condensed phosphates since the storage phosphates were not yet used. After previous incubation in a P-free culture medium of the algae the ³²P was rather rapidly incorporated and was found mostly in the highmolecular-weight condensed phosphates.During MAK-chromatography the high-molecular-weight fractions were eluted together with the nucleic acids (tRNA and DNA) while most of the low-molecular-weight fractions left the column immediately on elution.     

Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific

Numerous studies have documented declines in the abundance of reef-building corals over the last several decades and in some but not all cases, phase shifts to dominance by macroalgae have occurred. These assessments, however, often ignore the remainder of the benthos and thus provide limited information on the present-day structure and function of coral reef communities. Here, using an unprecedentedly large dataset collected within the last 10 years across 56 islands spanning five archipelagos in the central Pacific, we examine how benthic reef communities differ in the presence and absence of human populations. Using islands as replicates, we examine whether benthic community structure is associated with human habitation within and among archipelagos and across latitude. While there was no evidence for coral to macroalgal phase shifts across our dataset we did find that the majority of reefs on inhabited islands were dominated by fleshy non-reef-building organisms (turf algae, fleshy macroalgae and non-calcifying invertebrates). By contrast, benthic communities from uninhabited islands were more variable but in general supported more calcifiers and active reef builders (stony corals and crustose coralline algae). Our results suggest that cumulative human impacts across the central Pacific may be causing a reduction in the abundance of reef builders resulting in island scale phase shifts to dominance by fleshy organisms.