Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years. These 'seaweed tides' can harm tourism-based economies, smother aquaculture operations or disrupt traditional artisanal fisheries. Coastal eutrophication is the obvious, ultimate explanation for the increase in seaweed biomass, but the proximate processes that are responsible for individual beaching events are complex and require dedicated study to develop effective mitigation strategies. Harvesting the macroalgae, a valuable raw material, before they beach could well be developed into an effective solution.

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Green and golden seaweed tides on the rise

Sediment mediated species interactions in coastal waters

A broad spectrum of events that come under the category of green tide are recognized world-wide as a response to elevated levels of seawater nutrients in coastal areas. Green tides involve a wide diversity of sites, macroalgal species, consequences, and possible causes. Here we review the effect of natural and man-induced environmental fluctuations on the frequency and apparent spread of green tides. This article highlights the need for interdisciplinary research aimed at shedding light on the basic mechanisms governing the occurrence and succession of green algae in coastal seas. This will result in more effective management and mitigation of the effects of green tides, thus safeguarding the intrinsic and commercial value of coastal marine ecosystems.

‘Green tides’ are overwhelming the coastline of our blue planet: taking the world’s largest example

Global demand for bio-fuels continues unabated. Rising concerns over environmental pollution and global warming have encouraged the movement to alternate fuels, the world ethanol market is projected to reach 86 billion litres this year. Bioethanol is currently produced from land-based crops such as corn and sugar cane. A continued use of these crops drives the food versus fuel debate. An alternate feed-stock which is abundant and carbohydrate-rich is necessary. The production of such a crop should be sustainable, and, reduce competition with production of food, feed, and industrial crops, and not be dependent on agricultural inputs (pesticides, fertilizer, farmable land, water). Marine biomass could meet these challenges, being an abundant and carbon neutral renewable resource with potential to reduce green house gas (GHG) emissions and the man-made impact on climate change. Here we examine the current cultivation technologies for marine biomass and the environmental and economic aspects of using brown seaweeds for bio-ethanol production.

Mass-cultivation of carbohydrate rich macroalgae, a possible solution for sustainable biofuel production

Changes in the composition and structure of Mediterranean rocky-shore communities following a gradient of nutrient enrichment: descriptive study and test of proposed methods to assess water quality regarding macroalgae.

The eutrophication, or nutrient enrichment, of coastal waters as a result of man’s activities is now widely recognized as a major, world-wide pollution threat. Essentially, the increased anthropogenic source of inorganic plant nutrients interferes with the natural annual nutrient cycles and can artifically enhance primary production during periods when activity is normally low. This can have quite considerable ecological consequences for both pelagic and benthic organisms. For example, phytoplankton activity will be increased (Hoogweg et al. 1991) and, although this can be generally beneficial by increasing fisheries (Raymont 1947; Fonselius 1978; Elmgren 1989), there is some evidence that it has resulted in the occurrence of some phytoplankton blooms, both toxic and non-toxic, which have had serious effects on local fisheries and leisure activities (Braarud 1945; Ruud 1968; O’Sullivan 1971; Zou and Dong 1983; Rosenberg 1985; Kimor 1991). One such bloom occurred in the northern Adriatic in 1988 when large quantities of mucilaginous material was washed up on many tourist beaches (Degobbis 1989; Vukadin 1991). A number of authors have similarly speculated on the possible relationship between eutrophication and the occurrence of toxic blooms of microalgae in the North Sea (Cole 1972).

R. L. Fletcher

Papers

The Occurrence of “Green Tides”— a Review