Botanica Marina 

About: Botanica Marina is an academic journal published by De Gruyter. The journal publishes majorly in the area(s): Algae & Ecology (disciplines). It has an ISSN identifier of 0006-8055. Over the lifetime, 3067 publications have been published receiving 75651 citations. The journal is also known as: Botanica marina online.

The Ecological Significance of Extracellular Products of Phytoplankton Photosynthesis

Abstract: From laboratory studies on the release of glycollate and other extracellular products during algal photosynthesis it seems likely that a similar release should occur from phytoplankton ander natural conditions. This expectation is realizcd, but the extent of the release is uncertain. When various sources of error in determination of rate of release, including assimilation of extracellular products by heterotrophs, are taken into account it seems probable that the commonly accepted values, of around 5% of total carbon fixation in eutrophic waters rising to about 40% in oligotrophic waters, are reasonably correct. Except perhaps äs an overflow mechanism when photosynthesis takes place more rapidly than is required to supply the needs of growth, the release seems to be of no biological advantage to the phytoplankton, which do not reassimilate their extracellular products to any appreciable extent. Utilization by heterotrophs, however, is rapid, often equalling rate of production, and production of biomass in this way may sometimes amount to about 25% of primary production. Glycollic acid, which is often a major component of the released material, and which is normally present in seawater, appears to serve äs an energy source for uptake and assimilation of other Substrates rather than äs a direct Substrate for growth of marine bacteria.

A Modified System of Nomenclature for Red Algal Galactans

Abstract: A nomenclature system for red algal galactans based on their chemical structures is proposed. The terms «agaran» and «carrageenan» are suggested as the generic names for two possible diastereoisometric extreme structures of carbohydrate backbone built of alternating 3-linked β-D-galactopyranose and 4-linked α-galactopyranose residues and differing only in the absolute configuration of the 4-linked α-galactose residues (L- or D-, respectively). «Agarose» and «carrageenose» are the generic names for the corresponding backbones having 3,6-anhydro-α-galactopyranose (also L- and D-) as the 4-linked residue. All the other known regular structures may then be designated as substituted (methylated, sulfated, etc.) derivatives of agaran and agarose (agar group polysaccharides) or carrageenan and carrageenose (carrageenan group polysaccharides)

Excessive Growth of Macroalgae: A Symptom of Environmental Disturbance

Abstract: Excessive growth of seaweeds is a response of the biocenose, in a particular biotope, to a supply of nutrients. This supply may be natural or of anthropogenic origin. In the latter case, excessive growths and drifts of algae are consequences of the disturbance in the environment. Such growths are becoming increasingly widespread as the result of the progressive eutrophication of coastal waters, and now occur in at least twenty five countries worldwide. For example, particularly significant accumulations of seaweed are observed annually in Italy (1 000000 t fresh weight), France (100000-200000 1), and Australia (100000-600000 t). The densities range from 0.2 to 400 kg m~, the thickness of the mats from 2 to 100 cm. The first part of the present review describes the worldwide phenomenon and includes information on the localities affected and the density, biomass, annual production and harvesting time of the excessive algal growths. The second part tries to analyse the phenomenon and the problems posed by seaweed decay. Lagoons, bays and shallow estuaries near industrial, agricultural and urban areas are most affected by these increases in algal growth. In temperate waters, excessive growth of macroalgae is generally observed during the summer, while in tropical waters, it occurs during the winter. At first, the development of opportunist and tolerant seaweeds acts as a purifying system. Then, when the seaweed is stranded or the environmental conditions become unfavourable, the plants die and decompose. At this stage, a large biomass can become troublesome. In summary, the impact on the environment is as follows: an increase in the herbivore population, competition or toxicity towards flora and fauna, alteration of the sediment, recycling of nutrients and pollutants in the ecosystem, nuisance for local residents and reduction of tourism. Cast weed is sometimes collected from the beaches and dumped inland, but this method of disposal merely constitutes a transfer of pollution. Consequently, different ways of treatment were developed, including composting and methanisation.

Regression of Mediterranean seagrasses caused by natural processes and anthropogenic disturbances and stress: a critical review

Abstract: Seagrass meadows are considered to be among the most important marine ecosystems, with regard to both ecology and biodiversity and for the services they provide. Seven species occur in the Mediterranean Sea: Posidonia oceanica (the most common in the open sea), Cymodocea nodosa (particularly common in the eastern basin), Ruppia cirrhosa, R. maritima, Zostera marina and Zostera noltii (mainly in estuaries and brackish lagoons), and Halophila stipulacea (introduced from the Red Sea). Seagrass regression may be due to natural processes and/or natural or anthropogenic disturbances and stress. It can also be due to long-term climate trends, e.g., the post-Last Glacial Maximum rise in sea-level, the Little Ice Age (LIA) cooling and the post-LIA warming, resulting in possible misinterpretation. Human-induced losses of P. oceanica have been mainly related to coastal development, pollution, trawling, fish farming, moorings, dredging, dumping and introduced species. All other seagrasses have also undergone more or less dramatic regression events. In fact, accurate data are generally of very local value and they are lacking for most of the Mediterranean Sea. In the absence of a reliable baseline, some widely cited cases of regression are questionable. Relatively healthy P. oceanica meadows, whose limits have changed little since the 1950s, may thrive in highly anthropized areas. In addition, the decline of one species can benefit another, so that the overall seagrass balance may remain unchanged (e.g., Cymodocea replacing Posidonia). However, to conclude that everything is for the best would be erroneous. First, the lack of data supporting the general regression hypothesis does not invalidate the hypothesis. Indisputably dramatic seagrass losses have been documented (e.g., P. oceanica and Z. marina). Second, the Posidonia regression is irreversible at human scales, while other seagrasses can rapidly recover, and the expansion of some seagrasses (e.g., Cymodocea) cannot counterbalance, in terms of ecosystem services, the decline of the P. oceanica meadows. Third, human pressure (demography, tourism, etc.) on Mediterranean seagrass ecosystems is destined to strongly increase in the coming decades. Finally, the rise in sea-level due to global climate change will automatically induce a withdrawal of the lower limit of seagrass meadows whenever the limit is beyond the compensation depth. So the regression trend observed in Mediterranean seagrasses, even if it proves to be currently weaker than postulated, will significantly increase and become a major concern in the future. There is therefore an urgent need for the adoption of a set of efficient indicators and the setting up of a robust comparative baseline in order to draw up an accurate assessment of the losses and, for seagrasses other than Posidonia, possible gains at Mediterranean scale. In addition, seagrasses and seagrass habitats should be granted legal protection and, where such protection already exists, it should be implemented.