Trichodesmium Research Articles

Distribution of the cyanophyte Trichodesmium (Oscillatoriaceae) in the eastern Caribbean Sea: influence of the Orinoco River.

Orinoco River influence in the Caribbean Sea, characterized by high nutrient input, causes a decrease of Trichodesmium populations. The Caribbean Time Series (CaTS) station, south of Puerto Rico (17 degrees 36'N 67 degrees 00'W), was monitored for 25 months in order to observe the Trichodesmium abundance pattern and the presence of the river plume. In general, mean Trichodesmium abundance was higher at the surface and decreased with depth. The mean upper water column (surface to 20 m) abundance was 54.1 +/- 32.6 col/m3. Within the sampling period, abundance was highly variable (1-700 col/m3). Correlation between Trichodesmium abundance and wind speed (p=0.002), chlorophyll a concentration (p=0.001), nitrate (p=0.02) and silicate (p=0.003) concentrations were statistically significant. However, Trichodesmium abundance was not correlated with salinity (p=0.70), temperature (p=0.16) and seawater density (p=0.71) variations at CaTS. Eastern Caribbean regions highly influenced by the Orinoco River discharge were devoid of Trichodesmium colonies.

Density Account of Cyanobacteria (Genus: Trichodesmium) in Selected Cebu Provinces, Philippines

Density Account of Cyanobacteria (Genus: Trichodesmium) in Selected Cebu Provinces, Philippines

Intense ectoenzyme activities associated with Trichodesmium colonies in the Sargasso Sea

Ectoenzyme activities of alkaline phosphatase (APA) and leucine aminopeptidase (LAP) associated with Trichodesmium, a globally significant dinitrogen (N2) fixer, were measured on cruises to the Bermuda Atlantic Time-Series (BATS) site. Rates associated with Trichodesmium were compared to microbial enzyme activities in natural seawater between August 1992 and November 1997. Colonies of Trichodesmium function as 'microsites' for ectoenzyme activity and express high rates of APA (4 to 66 nmol colony �1 h �1 ) and LAP (53 to 389 nmol colony �1 h �1 ). For Tricho desmium APA, substrate half-saturation constants (Km) exceeded surrounding seawater APA by a factor of 20 to 40 times. Overall, the ectoenzyme activity measured in puff shaped colonies of Trichodesmium did not differ significantly from the rates associated with the tuft mor- phology. Ectoenzyme activites measured in the cyanobacterial consortium did not vary as strongly seasonally as was observed in natural seawater. Elemental ratios of Trichodesmium colonies showed a molar C:N ratio around the Redfield stoichiometry (mean = 6, range 4 to 7) while the C:P ratios were much higher (mean = 513, range 163 to 1044). Calculated per volume seawater, meas- ured uptake of phosphate and leucine were 4 to 6 orders of magnitude lower in Trichodesmium (1 to 5 fmol P l �1 h �1 and 0.1 to 3 fmol Leu l �1 h �1 ) than in microplankton (0.3 to 4 nmol P l �1 h �1 and 0.002 to 0.02 nmol Leu l �1 h �1 ). At peak abundance, Trichodesmium contributed a major part of total ectoenzyme activity in surface waters (81% of APA, 64% of LAP) suggesting that the dia- zotrophic colonies are significant sites of net nutrient regeneration. We propose that the high rates of regeneration associated with Trichodesmium colonies may accumulate dissolved nutrients dur- ing the course of bottle incubations, which leads to isotope dilution and an underestimation of P and N uptake in radiotracer studies with these cyanobacteria.

On the Occurrence of Trichodesmium Erythraeum (Ehr.) Bloom in the Coastal Waters of Kalpakkam, East Coast of India

A prominent discolouration of the coastal waters by the blue-green alga Trichodesmium erythraeum was encountered in the east coast of Kalpakkam on 16th March 2007. The bloom persisted only for one day exhibiting visible alteration in physico-chemical properties and phytoplankton community structure of the coastal waters. The Trichodesmium cell density was 4.14 x 10 6 cells l -1 , sharing 74.19 % of the total cell count (5.57 x 10 6 cells l -1 ). Only 24 species of phytoplankton were encountered on the day of bloom as compared to the highest number of 44 species in a single observation during pre- and post-bloom periods (1st March to 29th March). Concentration of chlorophyll-a and phaeopigments increased to about 20 times on the day of bloom compared to the pre-bloom values. An abrupt increase in ammonia, total nitrogen and phosphate was noticed on the day of bloom. The impact of this bloom on coastal water quality is reported.

Characterization of Phosphorus-Regulated Genes in Trichodesmium spp.

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