Blue-green algae of a developing salt marsh
In the past few years considerable attention has been paid to the distribution of the microflora of the salt marshes at Gibraltar Point, Lincolnshire (National Grid reference TF 555576). During these studies it was observed (Turner, personal communication) that blue-green algae (Myxophyceae) were of frequent occurrence in soil samples from the region, but no analyses of the algal flora were carried out. It is well established, however, that blue-green algae are generally present in salt marsh regions (Chapman, 1960 a). Previous studies on the blue-green algae of British salt marshes are few, although detailed investigations have been carried out at Canvey and Ynyslas (Carter, 1932, 1933 a, b) and Scolt Head Island (Chapman, 1939). Some difficulty is experienced, however, in attempting to correlate these results with present day studies, mainly because of the widespread colonization of salt marsh regions within recent years by Spartina townsendii H. & J. Groves, and by the fact that few quantitative data are available. It is hoped that the present communication which is concerned with the blue-green algal flora of the New Marsh at Gibraltar Point, a region dominated by Spartina townsendii, will allow an assessment to be made of the flora prevailing in a developing salt marsh under present-day conditions.
Available from: Christopher Janousek
- "Using rRNA estimates of diversity, Rothrock and Garcia-Pichel (2002) noted lower diversity in assemblages of heterotrophic bacteria and cyanobacteria at higher intertidal elevations. However, other work at the species level suggests that benthic taxa are generally well distributed across the intertidal (only showing differences in abundance across zones), suggesting widespread dispersal and/or broad tolerance to a variety of environmental conditions (Stewart and Pugh 1963, Sage and Sullivan 1978, Zedler 1982, Saburova et al. 1995). Differences in microphytobenthic composition may also be driven by other environmental gradients or interactions with wetland organisms such as canopy-forming vascular plants. "
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ABSTRACT: Sediments in coastal wetlands host communities of phylogenetically diverse primary producers such as diatoms, cyanobacteria,
and anoxygenic photosynthetic bacteria, but little is understood about spatial variation in the composition of these assemblages
at the highest taxonomic levels. Using High Performance Liquid Chromatography to quantify taxon-specific pigments, I investigated
habitat-linked heterogeneity in microphytobenthic biomass, composition, and diversity within two natural wetland systems from
southern California and tested for differences in community structure between natural and restored ecosystems. Natural vegetated
habitat at Mission Bay had higher concentrations of zeaxanthin (cyanobacteria) and bacteriochlorophyll a (anoxygenic photobacteria)
than unvegetated mudflat and creek banks. Organic matter was positively correlated with the concentrations of these pigments,
whereas sediment pore water salinity and sand content were generally unrelated to composition. At Tijuana Estuary, community
structure was generally similar between mudflat and Spartina marsh at the natural site, but concentrations of chlorophyll a and fucoxanthin (diatoms) were higher in mudflats. Restored
wetland similarity with adjacent natural habitat (age 2 yr at Tijuana Estuary and 6 yr at Mission Bay) depended on habitat
type and pigment measure. Restored upper intertidal succulent marsh at Mission Bay was most divergent: it had lower microalgal
biomass, a lower concentration of zeaxanthin relative to fucoxanthin, and less bacteriochlorophyll a relative to chlorophyll
a than natural habitat. The results suggest that patches of prokaryotic primary producers coincide with areas of high sediment
organic matter and/or hypoxia superimposed on a broadly distributed flora of diatoms across various wetland landscapes.
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ABSTRACT: 1. The extent of nodulation and nitrogen fixation by a population ofHippophaë rhamnoides bushes occurring on a sand dune system on the east coast of England has been studied.
2. Nodules were found on all plants (the latter ranged from 3 to 16 years in age) and using the isotope N15 it was confirmed that these nodules fixed nitrogen. The nodules on the youngest plants were most active in fixation but because of the greater total nodule mass older plants fixed the largest quantities of nitrogen.
3. Large increases in total nitrogen (i.e. soil plus plant nitrogen) occurred with increase in age of the plants, such nitrogen increases ranging from 27 kg per hectare per annum in the presence of bushes 0 to 3 years old to 179 kg per hectare per annum in the presence of bushes 13 to 16 years old.
4. The N15-technique indicated that a proportion of the nitrogen accumulated was due to fixation byHippophaë but nitrogen contributions from other sources could not be ruled out.
5. The levels of nitrate-nitrogen and ammonium-nitrogen in the soil underHippophaë showed a marked seasonal variation, increasing to a maximum in the winter and to a minimum in the summer. These levels were in general inversely related to the level of average monthly rainfall. Because of the low levels of combined nitrogen in the soil during the summer months it seems unlikely that combined nitrogen should markedly inhibit fixation in this situation.
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